Have you ever had a intake grate break on you and what were the results?

[Hal]

I have and it was'nt fun. Got tossed out of the boat and almost lost the boat.
Anyway after reading the post about the SS grate and problems with cracks in the welds I'm wondering how many of you guys have actually had one break on you and what were the results?
[ January 05, 2003, 12:46 PM: Message edited by: Hal ]

[77charger]

never had one break but lost a bolt one time it put a very small nick in the impeller.I use to check it often after that.

[Duane HTP]

I had a customer expirmenting on a new design of his own. When it let go, it stopped the lightweight race boat so fast, that he had 357 stitches to his face, chest and arms where he went through the dash. BE CAREFUL in that area.

[396_WAYS_TO_SPIT]

Duane HTP:
I had a customer expirmenting on a new design of his own. When it let go, it stopped the lightweight race boat so fast, that he had 357 stitches to his face, chest and arms where he went through the dash. BE CAREFUL in that area. Duane, that gave me a bad mental pic jawdrop jawdrop . I think I will leave my grate stock
396

[LVjetboy]

Only bolt heads like Charger. Use high grade bolts!

[HOSS]

Yeah, and don`t ski behind him. How fast do you think that bolt turned projectile was traveling? probably go right through the sternum.
How is the new boat 77?

[corlish]

I was a passenger in a Taylor SJ once when the grate fell out...as stated earlier NOT FUN. We were coming around a bend, water smooth as glass, I am guessing about 35-45 mph. When it came out, the boat stopped in a BIG HURRY and we were pointed in the opposite direction eek! . There were three of us, no-one was thrown out just banged up from bouncing around inside the boat.
The look on the two "older gentlemen" fishing in a jon boat was well about like this jawdrop
Corey

[jerry billet]

Just pulled my intake out last night, getting ready for the New year run. Was cracked almost entirely through the welds. Could not have had more than 1/2 inch holding on each side. Oh so close.
No time to get a new one, so will weld on this one. Will definetly get a replacement and carry a spare with me from now on.
Suggest to all that this be a regular inspection, touph to get under the boat and remove to properly inspect, but easier than diving for your hull by the safety crew while your in the hospital. Maybe NJBA should make this an inspection point also.
Good luck

[SSTSleakcraft]

I must have got WAY lucky. I noticed my boat wouldn't hook up when it normally loves the rough. Put it on the trailer and noticed it was gone. The welds broke from the pad. It might have fell out on the way to the lake. I figured in the water, it would have eaten my impeller.

[396_WAYS_TO_SPIT]

LVjetboy:
Only bolt heads like Charger. Use high grade bolts! Are you referring to charger boats? I am lost :confused: :confused:
396
( I am just curious because one of my boats is a charger)

[LVjetboy]

396, I was refering to 77Charger's post about loosing a bolt head, something that's happened to me too. Nothing to do w/Charger boats...sorry for the confusion.
Hoss, I’m thinking if the nozzle’s pointed high enough for the bolt to get ya, the rooster’d knock you off first. But since you mentioned it...
Let’s say you deep-water start and the nozzle’s pointed level with the water surface. You yell, “Hit it!” and at that moment a loader bolt lets loose and heads out the nozzle at jet velocity, say 150 mph. We know from watching James Bond where he’s fighting sharks with dudes on the dock shootin’...bullets go down 20 or 30 feet, right?
Now if the bullet speed is 1500 mph, that’s more than ten times the speed of the bolt head. So if the bolt exited the nozzle into still water, it may go say 2 or 3 feet...let's say 5 feet for good measure. But the bolt is traveling with a slug of water going the same speed. That slug of water dissipates pretty fast too, water fighting water and all, maybe to near zero about 10 feet out? So even if the bolt was still doing 150 mph at 10 feet out, it still slows to a stop no more than 15 feet out. Since I ski a 75-foot rope, I got 60 feet to spare. Even if I used a 20 foot rope, at that point the bolt head’s all but stopped and just goes “boink” bouncing harmlessly off my beer gut.
Seriously though, checking intake hardware’s a great topic. I think most here already understand that a loader lettin’ loose at speed is a very bad thing. Instant speed brake, only underwater. Stopping just like the bullet. I was lucky, before I found two popped bolts and a loose loader, I rarely crawled under the trailer to check my loader...maybe once a season? Since then I check each trip. And I upgraded to black oxide bolts...two seasons ago.
jer
[ December 25, 2002, 12:11 PM: Message edited by: LVjetboy ]

[jerry billet]

any idea how this cracked? Only about 1/2" of weld holding each runner on. http://billetracing.net/images/intake.jpg
How about some input from all you experts.

[HammerDown]

I would bet the metal was fatigued at the Weld.

[Hal]

Jerry.. you were very lucky to catch that when you did. I agree with HD. Metal fatigue maybe caused by harmonic vibration and the force of the water pulling down on the grate. I would still like to know why some guys have this problem and some never do :confused:
[ December 28, 2002, 07:07 AM: Message edited by: Hal ]

[caution 2]

I have a friend that had a nordic pickle at about 90mph the grate broke spun the boat broke it in half piched him out luckly just bruised, Ron Smith in a pickle broke one spun out distroyed boat pitched him out luckly just bruised up, that was at a NJBA race,In my race boat I personaly take out and inspect my grate before each race, have found it cracked 2 times, and replace my bolts every 3rd race just in case. Jim Brock

[LVjetboy]

Which just makes you wonder...is loader design something best left to trial and error? Seeing as how there's technology and analysis these days to predict stress and failure? And the result of error is so costly?
Jerry Billet, the only thing I'm expert in is BS. But I'll be happy to guess, occasionally have something worthwhile to say, and certainly not shy of posting.
The weld failed in tension from water forcing the ramp down. Starting at the aft edge where the vertical brace meets the plate, and continuing forward. Then, when the vertical braces hit the pump intake, that extra support was enough to keep the weld from total failure?
As to why it failed, well, the break looks pretty clean in the picture, was that a cold weld you think? Quality control? Not proper heat and melting to bind materials? Also consider corrosion...big time rust seen in this photo, corrosion possibly a player, and/or sharp weld edges concentrating stresses, can easily start cracks. Fatigue from cyclic loading also possible...but not demanded. Micro cracks alone combined with a weak bond...crack grows and the weld fails.
Which brings to mind some obvious questions. Why not stress relieve the weld with smoothing? Seems a small thing and makes easier to spot cracks? And why not support the loader at the upper edge with the pump wall the first place? Just a matter of matching vertical braces to pump wall.
Even MORE important, why risk snapping a boat in two and 357 stitches to your face when this issue can be resolved with attention to better analysis and designs? Does this really need to be left to freakin' trial and ERROR?
What if the million or so odd systems in the Space Shuttle were all left to trial and error? You think it would even get to orbit? Compared to what engineering can know and predict, I'd venture the state of our jet pumps are dark ages.
jer
[ December 28, 2002, 01:40 PM: Message edited by: LVjetboy ]

[slotracer]

jim if the grate you are talking about is the one you showed me you should post a pic of it if possible that was one messed up grate. on another note after i left your shop about half way over the grapevine my alternator went out on me and i got stuck on the i5 for a couple of hours finally got towed into bakersfield to a pep boys and got a new alt. and changed it got home about 9 p.m. man what a drive. pat(slotracer) :D

[Jim Brock]

Yes, that grate was out of the Nordic tunnel, but don't have any way to post picture, sorry to here about your alternater problem, sometime i'll tell you about my 12hr trip from the top of the grapevine to my shop, towing a boat in my motorhome, Jim

[Duane HTP]

Guys, one of the biggest causes of failure in the area that the above picture shows is when the loader is bolted in, it does not rest on the floor or throat of the pump. This is a must. Not all pump throats are the same as you all know. When trading with someone to try out their loader, make sure the bottom of the vertical runners or the crossbar welded between them is against the bottom of the throat. If the runners are not down tight, that loader will vibrate like hell at top speed, and sooner or later it will break off.
Duane HTP
[ December 28, 2002, 06:05 PM: Message edited by: Duane HTP ]

[Rivernut]

I read a fair amount about riser stress and metal fatigue since my original post regarding intake grates and cracking. I found a rich article that went into a lot of detail on fatigue and "riser" stresses. Unfortunatly, I can't access the article from my server anymore, maybe you guys can. The article was on an aviation site and was titled "When Metal Lets us Down". The link is below. Anyway, they emphasized the importance of proper torque. If something is held tightly enough to another object, they behave as one, and bad harmonics may be avoided. The proper torque value on an intake grate is anyone's guess, and it is probably different for each boat and grate. They also said that paint on cylinder heads where the bolts seat will compress and lead to failure caused by harmonic vibration of the head over time and the different expansion rates does not help either with dissimilar metals. I assume the case is similar with intake grates. Should the seating area of intake grates be painted? Should silicone or other sealers be used or are they a cause of failure? And what about thread-lockers on the bolts? Too much to think about...I just want to go fishing!!! AV Web (http://www.avweb.com/articles/metfatig/ )

[bp]

i've had others tell me that the runners, or strakes, should have satisfactory clearance from the suction piece, such that the loader never comes in contact with it. the loader could crack the side of the suction piece. the mounting pad should sit flush into the recess - if it's not flush, you may think it's tight but it's not really.
i know of one racer(won't say who) that i observed just 'reefin on the loader screws, then 'reefin on the double nuts he was using (i mean really applying some serious foot poundage). i asked him why so much, and he told me it always came back loose on each pass (he also changed screws frequently). now, he's been doing this a lot longer than i have, but it seems to me that there is something wrong if the thing is loosening after each pass.
i visually check my loader after each pass, check that it's tight, and that the nuts are tight, and have not had any problems (knock knock). i think most people find no problems if the loader was correctly constructed, and fitted properly to an intake to begin with.
jer, i totally disagree with your "trial and error" analogy, whether it's nasa, nuclear power, or jets. it is continual testing, adopting knowledge gained through each test. the breakdown occurs in the area of quality control, and "skill of the craft", and then not applying any form of quality assurance for preventive maintenance of the components. ANYTHING can be run to destruction. poor qc, lack of attention to detail, or innadequate skill all lead to premature failure.
jerry francis, i agree that tech should look carefully at the things they can, and i really appreciate the good look i get when i get there a day early. however, i don't believe it's fair to lay component failure at the hands of tech. you need to make sure, as i do, that your stuff is in good condition.

[GlastronGuy]

bp:
i've had others tell me that the runners, or strakes, should have satisfactory clearance from the suction piece, such that the loader never comes in contact with it. the loader could crack the side of the suction piece. the mounting pad should sit flush into the recess - if it's not flush, you may think it's tight but it's not really.
i know of one racer(won't say who) that i observed just 'reefin on the loader screws, then 'reefin on the double nuts he was using (i mean really applying some serious foot poundage). i asked him why so much, and he told me it always came back loose on each pass (he also changed screws frequently). now, he's been doing this a lot longer than i have, but it seems to me that there is something wrong if the thing is loosening after each pass.
i visually check my loader after each pass, check that it's tight, and that the nuts are tight, and have not had any problems (knock knock). i think most people find no problems if the loader was correctly constructed, and fitted properly to an intake to begin with.
jer, i totally disagree with your "trial and error" analogy, whether it's nasa, nuclear power, or jets. it is continual testing, adopting knowledge gained through each test. the breakdown occurs in the area of quality control, and "skill of the craft", and then not applying any form of quality assurance for preventive maintenance of the components. ANYTHING can be run to destruction. poor qc, lack of attention to detail, or innadequate skill all lead to premature failure.
jerry francis, i agree that tech should look carefully at the things they can, and i really appreciate the good look i get when i get there a day early. however, i don't believe it's fair to lay component failure at the hands of tech. you need to make sure, as i do, that your stuff is in good condition. Where you been buddy? Haven't seen you around in a while. Hope you and Kathleen had a merry Christmas.
Chris

[bp]

hey chris, hope y'all had a great christmas. maybe with all this rain, oroville might come back up where we could see water??? we were outta town for the past week, and been working on the sw, tweaking a few things for next year. have a great new year, and if you're going to cfw, spank a few flatties willya???

[bp]

one more thing. it looks to me as though jerry francis' scoop was cracking for some time. there's obvious oxidation all along the crack.

[LVjetboy]

Bp, disagree on my trial and error soap? How could you! j/k. But I'd be happy to bounce some ideas off you later.
Sorta related, as in my ranting about lack of writen technical information for us jetter and confusion about some of the most basic things...here's an example:
In my post above, I suggested that the vertical support "strakes" resting on the intake wall could prevent the baseplate crack above. This was just a pure guess on my part as I've not seen anything writen on this or talked to the pro's about it. One of the pro's then posts that strakes resting on the throat is a must for support and damping vibration. Bp however has "heard" that the strakes should have clearance or can cause the intake to crack. It is of course possible that both could be true and the solution is to design the strake so the contact surface is spread more evenly across the intake. No big deal. But to me, the answer to a fairly simple question like this should already be known and recorded so the rest of us don't have to invent the wheel...by trial and error :)
jer
[ December 29, 2002, 11:55 AM: Message edited by: LVjetboy ]

[Hal]

Rivernut..I got to the site,but it looks like the article you seen has been removed.
Rivernut and bp both of you mentioned how important it was to have full contact between surface of the plate and the recess in the intake housing. In the last month that I ran my boat,on 2 checks this is what I found. 1st check I found that 2 screws were missing 1 had head sheared off and 1 was still intack but very loose. I had nuts on top but they were not nylocs.
The 2nd time after I replaced the screws I put on nylocs and safety wired them. I ran it a couple of times,checked and found that 3 of screws had the heads popped off one was still intack. Lucky two times...
I pulled it out and and on a more carefull inspection I found that the base plate was not flat. It looked like it was warped from the the welds. I got it straightened, reinstalled with some #8 screws. ( I had also welded some tabs on the vertical bars so they would rest againist the intake housing when it was installed.) Now I see that may have been a bad idea. Anyhow went out and tested 1 time 2 weeks ago without a problem, but I'm sure not going to feel comfortable at 90 +. Hell you can probably get tossed @ 60 if it breaks.
I don't know if they have changed the intakes sense the 70s (Mine is a 1977 model), because I sure don't think they were designed to take the stress of a scooped intake @ 100 +. I would think even if the base plate was making good contact and torqued down you would still get flexing in the 1/4" base plate from the force of the water being applied at
high speeds which would contribute to the vertical bars cracking at the welds. If someone is'nt already doing it, I would think somebody (who is currently set up to make them) could make
a replacement intake that is beefy enough to take the stess applied at high speed.
All you would have to is thicken the area (in the mold) on the intake where the recess is so you could have a 1/2" to 3/4" recess then you could have a base plate thick enough to use counter sunk 3/8" allen cap screws which could be torqued properly from the bottom of the boat. The base plate would then be thick enough that it would,nt flex.I have never liked the idea of having those wimpy 5/16" slot head screws being the only thing holding the intake. Thats got to be the most over stressed area on a jet race boat.
I don't know I guess I'am just rambling but I would sure like to find a way to have more confidence in the grate at hi speed besides a 6 pack of Coors. wink
If someone is making a better intake system please let me know. :)
[ January 05, 2003, 12:35 PM: Message edited by: Hal ]

[77charger]

HOSS:
Yeah, and don`t ski behind him. How fast do you think that bolt turned projectile was traveling? probably go right through the sternum.
How is the new boat 77? Hoss the new prop thing is great.So far i like it and its slower than the jet but smoother and quieter looking foward to long boat rides at powell in the summer

[LVjetboy]

77Charger...slower than a jet...no way!! So are you considering keeping it because it's smoother and quieter?
Hal, I'm no racer, so I'm thinking my opinion's a wash fypov, but I believe you 1/4 inch base plate is strong enough to handle race stress. I also think that "flex in the base plate" isn't an issue. Consider the longitudinal strengthening that 1/4 inch base plate gets from those horizontal strakes welded to it. Although a warped plate and/or pump mounting surfarce can magnify both vibrational and steady loads on your screw heads. This because the rocker from a warped plate works like a crow bar, shrinking moment arm and magnifying force on the screw. But that is not a "flex" issue.
Since you staightened the base plate, did you also check pump mounting pad for flatness? For good measure, have you considered black oxide allen heads?
I have more comments on the tabs but gotta go...
jer
[ December 30, 2002, 04:40 AM: Message edited by: LVjetboy ]

[bp]

Hal:
Rivernut..I got to the site,but it looks like the article you seen has been removed.
Rivernut and bp both of you mentioned how important it was to have full contact between surface of the plate and the recess in the intake housing. In the last month that I ran my boat,on 2 checks this is what I found. 1st check I found that 2 screws were missing 1 had head sheared off and 1 was still intack but very loose. I had nuts on top but they were not nylocs.
The 2nd time after I replaced the screws I put on nylocs and safety wired them. I ran it a couple of times,checked and found that 3 of screws had the heads popped off one was still intack. Lucky two times...
I pulled it out and and on a more carefull inspection I found that the base plate was not flat. It looked like it was warpped from the the welds. I got it straightened, reinstalled with some #8 screws. ( I had also welded some tabs on the vertical bars so they would rest againist the intake housing when it was installed.) Now I see that may have been a bad idea. Anyhow went out and tested 1 time 2 weeks ago without a problem, but I'm sure not going to feel comfortable at 90 +. Hell you can probably get tossed @ 60 if it breaks.
I don't know if they have changed the intakes sense the 70s (Mine is a 1977 model), because I sure don't think they were designed to take the stress of a scooped intake @ 100 +. I would think even if the base plate was making good contact and torqued down you would still get flexing in the 1/4" base plate from the force of the water being applied at
high speeds which would contribute to the vertical bars cracking at the welds. If someone is'nt already doing it, I would think somebody (who is currently set up to make them) could make
a replacement intake that is beefy enough to take the stess applied at high speed.
All you would have to is thicken the area (in the mold) on the intake where the recess is so you could have a 1/2" to 3/4" recess then you could have a base plate thick enough to use 3/8" allen cap screws which could be torqued properly from the bottom of the boat. The base plate would then be thick enough that it would,nt flex.I have never liked the idea of having those wimpy 5/16" slot head screws being the only thing holding the intake. Thats got to be the most over stressed area on a jet race boat.
I don't know I guess I'am just rambling but I would sure like to find a way to have more confidence in the grate at hi speed besides a 6 pack of Coors. wink
If someone is making a better intake system please let me know. :) hal, if the plate wasn't bottomed into the recess, the screws were not really tight, and would allow the plate to work against the screws. i would also eyeball the scoop to see if any part of it "looks" like an obstruction to water flow.

[jerry billet]

The grate is only one year old. The rust is from where shortened and filed doen the leading edge. Did not repaint it. I have taken the grate out many times for inspection and did not see any problems prior. I have never had a bolt break or loosen on the grate.
Some of the ideas I have heard not posted, are to somehow brace the rear of the grate in the jet. Some type of tab or slot that the rear of the grate ould slip ino or wedge against to keep the vibration down. Upon further inspection the area where it contacts the pump is a little worn from vibration. The base plate is not flat but I would worry about grinding on it as it would thin it out. Always use silicone to seal for leaks. The recessed area on the intake for the grate is not very flat either.
Agree, more work should be put into the loader grate, I've seen some pretty crude stuff.
Similar to other parts I've run across, if you can't find one, MAKE ONE.
Thanks for all the input. I look forward to beating you with all your ideas.
Only fitting, as in the season opener I lent fuel to Keith and he beat me. Then in the finals I lent a kill switch to Bob and he beats me too.

[Hal]

LV.. The base plate fit very good after I straightened it,There was no wobble in it like before. I could tell the differance when I put the screws in. They tightened up as soon as they hit the plate. (yes I did put in black oxide allen screws this time) The main reason I would like to see a thicker base plate would be so they could switch to counter sunk 3/8" allen cap screws. They could be torqued properly and I think it would put an end any fastening problems. I also don't think you would see the warping problems from welding on a thicker plate like you do on a 1/4" plate. I would like to hear your ideas on the tabs.
[ December 31, 2002, 08:34 PM: Message edited by: Hal ]

[HM]

I was lake racing an Elimator Daytona 19 about 8 years ago. He was just messing with me as my boat only did about 60 MPH back then. He hit it hard and all of a sudden, spun a full on 180 and came to a stop backwards. No one was hurt. I towed him back to the launch ramp. When he pulled out the boat, the left half of the intake grate was sticking straight down. I think he had just put on top loader grate.

[Duane HTP]

"Upon further inspection the area where it contacts the pump is a little worn from vibration".
On a lot of our faster race boats, we drill a 3/8" hole up through the bottom of the throat of the pump and then tap and thread the crossbar of the loader for a NC 3/8" bolt and lock tite it in. We used to use a 5/16 bolt for the application, but they would break off every once and a while. So that kind of tells you how much force there really is back there. The 3/8" bolt will stop the vibration. We even feel that we picked up one or two MPH on the R & D Express when we stopped the loader from vibrating. It loaded the impeller better. Duane HTP
[ December 30, 2002, 06:47 PM: Message edited by: Duane HTP ]

[Hal]

Daune.. what do you mean you drill and tap the cross bar? Don't you drill and tap the intake housing to 3/8" or do you just drill it out to 3/8" and use nuts on top to troque the screws down? Thanks.... Hal

[jerry billet]

I looked at my intake. You could drill/machine the housing to put the bolt in place. Would have to tap the loader grate, no way to get your hands in there to put a nut on anything.
Will be working on that item this weekend, most parties end up in the garage drinking beer anyway. Come up with most ideas then. (mostly hair brained ideas).
With any luck, we'll have a couple of cold ones and dream up some great ideas. Helps when you have all the tools you need in the garage to do prototypes, while you drink.
We'll share our ideas.
Have a great NEW YEAR>

[Hal]

Jerry.. I have my my engine moved forword a couple of inches and use a splined slip on drive shaft so I can put nuts on with every thing in place.
Don't you mean to drill and tap the intake housing and not the intake grate?
Happy New year to everyone.......... Hal

[Duane HTP]

We drill the intake housing, and we put the 3/8" threads is the crossbar between the runners. Torque to 35 lbs. You can weld a nut to the top side of that hole, but be sure to flow it. Duane
[ January 01, 2003, 11:16 AM: Message edited by: Duane HTP ]

[bp]

duane, could you post a pic? seems everyone is confused. are you drilling through the intake, or the suction piece? through the top of the suction piece, or the bottom?

[GlastronGuy]

bp
You and Kathleen should have left for Camp Far West by now. Put down the mouse! wink
We are only 40 minutes away and will be leaving shortly.

[Duane HTP]

I drill up from the bottom, through the INTAKE that is installed in the floor of the boat.

[Hal]

I still don't get the part you are threading. :confused: :confused: would'nt you thread the intake housing where the 5/16" screws were before? I don't have any cross bars on my grate and I can't understand why you would put threads on the grate anyway its only 1/4" thick. which is'nt thick enough to hold 3/8" bolts and then you would have to put the bolts in from the top and grind off whatever is sticking out passed the intake base plate to make it flush with the plate and the intake housing. Then you would only have a 1/4" of threads holding it on which may be weaker than than the original setup. :confused:
Tell it like your are talking to a real dumb guy next time and maybe I'll get it. idea
Thanks.......Hal

[Duane HTP]

I've never learned how to post pictures here. I'm not talking about the four intake grate mounting screws. On most racing intake grates there are two vertiacl runners welded to the mounting pad which has the four muonting screws in it. At the back of these runners there is a cross piece between them that should rest on the bottom of the throat of the intake. We drill up through the intake at that point and then thread the crosspiece and install a 3/8" bolt. This locks the crosspiece against the bottom of the throat of the pump and stops the vibration of the back end of the loader.

[Hal]

I got it this time Duane. I looked at some of the loaders at the MPD site and I see what you are talking about. I guess its time for a new loader. Thanks.....Hal
http://www.handykult.de/plaudersmilies.de/happy/invasion.gif

[gstark]

Here are some thoughts on the whole topic based on the preceding responses.
Rust on the loader - most likely this has no bearing on the loader's structural integrity. The oxidation rate of steel combined with the material thickness most likely results in cosmetic rust. As difficult as it is to see the failure, it appears to be HAZ (heat affected zone)cracking where there is a transition between as-cast weld deposit and parent wrought material.
Weld fatigue - whether or not this is a fatigue failure or a static load failure requires a trained eye to determine this. Jetmugg is certainly qualified to render an opinion on this.
The weld quality, quality control procedures, etc. are really a moot point. Unless you have visually inspected the part and have had it in your hands, these are only conjecture.
Whether or not the weld was cold lapped, or has poor penetration, I can't see in the photo. As far as stress relieving a plain carbon steel weldment such as this, I doubt that there is any benefit. The weldment is fairly simple with short longitudinal welds, and any post-weld residual stresses are likely negligible on these thicknesses and geometry.
The likely culprits for the bolting problem are (1) surface flatness of both mating pieces and (2) incorrect torque values.
Unless the weldment has been milled flat or surface ground over the entire surface, it is likley that 1/4" mounting plate is both warped and distorted due to welding. The inlet housing is cast aluminum, and most likely is not a machined surface. Now try to mate these two uneven surfaces together and torque the fasteners. What happens is that the bolts apply a compressive force to the plate. Unfortunately, the amount of compressive axial force (due to torquing)never reaches the amount required to flatten one or both surfaces. The loader never gets properly secured to the inlet housing.
Think of it as a series of springs, because that is what is coming into play. Cast aluminum and steel materials with elastic moduli (stiffnesses)of 10x10^6 psi and 30x10^6 psi are being locked together by a 30x10^6 psi fastener. The correct torque to apply to these material types is a calculated value based on several factors, including the elastic moduli of the materials, the diameters, and the desired preload. Add uneven surfaces and one has no idea of the correct torque value to use. You may know the rated torque to apply based on the fastener but you do not know the correct torque to achieve both the required preload and to overcome the mating surface characteristics. Refer to a machine design textbook (not the Machinery's Handbook) addressing bolted joints for more background on this subject.
Then when the loader gets used, it sees loads that increase the preload and decrease it as well. Without threadlocking of some type, and maybe with it, a reduction in bolt preload occurs with eventual bolt failure. Stress concentration factors come into play here as well, but to generalize is kind of dicey.
As far as thickening the base plate from 1/4 to 3/8 to eliminate distortion, it isn't likely that this will solve anything. With a t-type weld joint, you will need to increase the weld amperage/current to achieve adequate penetration if you up the gage. Regardless, a t-type weld joint generally results in distortion/warping on the parent or base material as the weld pool solidifies. The only way to eliminate this is with chill rings/plates and rigid weld fixtures. Then a stress relief may be in order.
From a design and structural perspective, I will begin by assuming that both surfaces will be both flat and are correctly torqued at installation.
The loaders function is to direct the incoming water flow higher into the bowl, hopefully increasing the pump efficiency. Correct me if I am wrong here. However, most loaders that I have seen are mounted at the forward end of the pump inlet by 4-flat head fasteners. This is great if all you were doing is attaching the mount to the pump, except that now we add a whole bunch of steel to the flat plate. This steel is cantilevered from the plate and has substantial mass relative to the plate. The composite CG of the structure is likely biased aft of the geometric center of the loader.
Now we apply loads to the grate as we operate the boat. These loads come from two sources, and possibly a third which I will ignore for now. The first source of load is the obvious one, the flow of water over and under the loader. One will always assume that the forces acting on the loader are always downwards, but I doubt this is correct. In all likelihood, there is loading that results in both tension and compression forces upon the structure. These forces can be summarized to act at the centroid of the structure. A bending moment (force x distance) results which is reacted into the baseplate, along with shear loads and other axial loads. These moments and forces may or may not be cyclical - they may be a steady state , or they may reverse depending on the conditions. The real problem here is that no one knows much about these forces, whether they are reversing, partially reversing, cyclical, and most importantly, what their magnitude is. This is compounded by the fact that every hull will result in different values. We do know that these loads are dynamic as they are constantly occuring. The nature of these loads is summarized by what is called Random Vibration. Using the appropriate instrumentation, a PSD (power spectral density) plot could be generated that quantifies the magnitude of these forces and the frequency at which they occur. In simple terms, a snapshot of this PSD would represent the energy being absorbed by the structure. This energy creates displacement of the structure and therefore strain. Stress is a mathematical indicator that relates the actual strain to the material properties of the loader.
The second source of loading is one that is probably overlooked 99.9% of the time. Every reciprocating or rotating piece of equipment (pumps, compressors, turbines) generates critical frequencies (N1, N2). At these frequencies, excitation occurs, and this excitation can be transferred to adjacent components based on transmissability, mounting, etc. This type of vibration is called Sine Vibration. For those in the design area, Mil-Std-810 or RTCA/DO-160 are governing specs commonly used. I am sure that if I mounted a loader on a shaker table, that I could drive it to failure at some frequency between 50hz and 500 hz in short order. The real question is "What is that frequency ?" If the loader's natural frequency matches that of the pump, there is trouble for sure. The basic design of the loader with cantilivered slender members fixed at one end makes this design prone to failure. The natural frequency of a simple structure such as this can be calculated fairly easily. The fact that it can should tell us something. Reading Duane's fix to race loaders, it sounds like he fixes the opposite end of the loader, so that both ends are fixed. This dramatically changes the boundary conditions of the structure, stiffening it, and moves the natural frequency maybe by a factor of 10x or more, probably eliminating displacements and strain/stress.
The third mode of loading is when we contact something that we don't want to, such as debris or a bottom. This creates an impact load which can cause a static overload failure.
Enough rambling - all of you are probably tired and confused as hell by now. Let me know if you want to hear a mechanical engineer's explanation or not.
[ January 01, 2003, 07:37 PM: Message edited by: gstark ]

[Hal]

I think everyone on this site appreciates it when person with your knowledge on a subject will give us such an in depth reply. I know you gave me the answers to why my problems were happening. I thank you for your time. Hal

[jerry billet]

WOW! your making me think too hard. GSTARK you add quiet a bit of info to consider. Probably have everyone rethinking thier loader grates now.
Spend some time with the neighbor and looking at the grate I have. Deceided that the design may be good, but for speeds we are running, the workmanship is bad. Deceided the best option is to remake one with a proper jig, and stess releive it. Also include an attachment for the rear.
Thank every one for your input, lets hope this does not die. Have not seen anyone post pictures of thier fixes. I will show you my prototype when completed.
Thanks

[Jetmugg]

Good analysis, Gstark. I think one of your earlier posts hit it right on the head - We need to understand the mode of failure before we can fix the problem. Based on the photos posted earlier, It's impossible to tell the failure mode. We need to be able to see the fracture faces themselves. General rules of thumb - if the two surfaces look macroscopically smooth starting at the fracture initiation site, and then the last portion of the material to break looks rough and pebbly, then it's a fatigue crack. If the whole surface looks like it's torn and rough, that's a ductile overload failure.
All this talk has me a bit worried, I think I'll have to investigate the added support like Duane described.
This is a great thread, valuable for high performance, and it just might save somebody's life.
SteveM.

[bp]

The weld quality, quality control procedures, etc. are really a moot point. Unless you have visually inspected the part and have had it in your hands, these are only conjecture.
----------
excellent write-up GSTARK. however, i do not believe quality control to be moot. on the contrary, you're entire write-up is a tribute to design quality control.
i did not mean to imply that the failure on jerry's loader was a direct result of poor weld quality, or skill of craft, although it could be. as sm mentioned, without closer examination, failure mechanism cannot be accurately determined (another quality process). my point was that pretty much any backyard dude can buy a welder, eyeball someone's loader, glue something together and go run it to destruction. knowledge of design (design quality, knowing the correct methods, and the correct questions to ask), and the risk if the effort fails, need to be considered before DIY.

[gstark]

bp - I was not inferring that you were stating the failure mode of jerry's loader. Rather I was addressing the entire topic which consisted of many opinions and thoughts. I noticed that you've tended to focus on "quality" aspects, and therefore have tried to address these ideas.
I do not believe that I made myself clear when I stated the "weld quality, quality control procedures, etc. are really a moot point."
What is weld quality ? How is it defined and measured ? How is it assured on a production basis? Visual inspection, NDE methods, test coupons, material/chem certs ?
What are quality control procedures ? Is this an AS9000, ISO 9000, D1-9000 or UL requirements item or what ?
How is quality assurance actually delivered to the part ?
What are the non-destructive exam methods such as penetrant inspection or radiographic inspection and the acceptance criteria for each?
These were my thoughts when you brought up quality control. I could be wrong but I'd bet that the fabricators of these items do not have the internal organization that supports these processes and procedures.
Therefore, until these subjects are established and understood, talking about these topics seemed premature (moot) to me.
The failure mode, whatever it is, is not necessarily a failure due to quality issues. There can be inherent deficiencies in the design, some of which I have tried to touch upon by describing the dynamic behavior of structures.
There can be an underestimation of the environment in which the part operates. This means the forces, displacements, and other unknown inputs may influence the behavior and possibly the failure of the structure.
I would tend to see my previous post from a designer's perspective bringing over 20 years of design, analysis and product testing to the table for all of us to chew on.
I certainly agree with you regarding anyone being able to slap something together with a buzz box and running it. There can be a huge difference between an adequately designed product and somthing made in your garage. But not always.
One cannot discount the experience of the pros who frequent this board and other pros who don't. Personally, I am aware of one pro who brings the engineering side to the table along with his extensive and rich racing/business experience.
For what it is worth, I am an avid DIY'er. MIG/TIG/SMAW, machining, you name it. An important aspect of this is knowing when one is out of his league and should seek out one of the pros.
The bottom line through all of this is hopefully, more design work can be done on these loaders. From the sound of it, there are serious issues when failure occurs, and damage to property, life and limb is something that all of us want to avoid.
Now, I think I will now go outside and examine my own intake grate. (I don't have a loader). All this thinking has got me thinking and worrying.

[LVjetboy]

GStark, I'd shoot you another 5 for that detailed post but I can't vote twice :) As you know I'd love to see more "engineering" and analysis in every part of jet pump technology.
Now if you'd just post more often... :D
And for your last post...yep, I think a lot of us took a trip to the garage to look closely at that loader. Me included...all a good thing from this thread I'd say.
jer
[ January 02, 2003, 07:51 PM: Message edited by: LVjetboy ]

[gstark]

LV - I generally post only on subjects that are of serious technical/safety interest to me and avoid all the "peripheral" topics lacking this content.
I must correct myself from my first post when I described loading conditions. When I was thinking about this subject, I envisioned the fluid/hydraulic environment into which the loader operated and the loading that this imposed on the structure. I described this from a standpoint where one could test and validate a design using random vibration spectra.
I have further discussed this topic with a colleague of mine who specializes in finite-element analysis. I described the problems we've been discussing and showed digital pics of intakes, pumps, etc. His comments on this were:
1. Design any structure to have a fundamental resonant frequency greater than 6000 hz and you will probably never have a failure. Frequency matching of the pump/engine to the loader will fail something, when is the question.
2. Any analysis performed to optimize the design would be specific only to that hull/intake and it would be difficult to apply one set of answers across the board. Cost or time to do this work starts to get big in a hurry. What is the economic payback on this - is there a market for these items, and how big is it ? (when he said this I knew that what I have been teaching him over the past 5 years had finally sunk in).
3. The inlet of the pump area is amazingly crude and substantial benefit can be reailzed by improvements to this area. He suggested a 15 deg or less scoop with gradual turning vanes that could act as a ram inlet. How this is accomplished without secondary problems is the question. Balance drag against performance increases (if any).
4. The single point mounting system with cantilevered mass is poor from a dynamic perspective .
He suggested that the best approach was a trial and error method to see what works.
See what happens when we try to over-analyze and complicate things.

[Hal]

gstark... Thanks for all info and time you gave this topic. I hate sad endings. cry I did pick up some good info in this post though. :D It looks like my intake grate screws were probably breaking because of the base plate being warped and that with a different grate I can add a couple of extra fasteners for better stabilization of the grate.
It still leaves a lot to be desired as far as safety goes. The original design was probably safe for a 60 MPH jet boat because the stock intake does'nt have the loading stress on it that we put on with after market stuffer grates. So you can't blame the the engineer who designed the pump. The trial and error method can be very painfull or deadly while learning which intake works the best and is safe also. These pumps have been out over 30 years and It looks like we have not found the answer yet. frown
[ January 04, 2003, 10:54 AM: Message edited by: Hal ]

[gstark]

Hal - I agree with you. I'm not a fan of trial and error when there are consequences such as discussed.
On another note, if you are thru-bolting your loader on, what fasterers are you using. You may consider an A286 fastener which is a high strength corrosion resistant material. There are used in turbines and hot sections of engines. There are a number of callouts for these, typically a NAS number. If you need further info, let me know. In fact, I've got a good selection of these at home - who knows we may live close to one another. You would be welcome to these if desired.

[Hal]

gstark, Check e-mail

[LVjetboy]

Hal, I think kinda sad too...economics limiting jet pump R&D and all. Not much of a jet market out there. Until someone with resources, motivation and expertise puts effort into say, designing a less crude intake, or a better loader, progress is slow, in some cases non-existent, and exclusively trial and error. Those with the most resources (maybe pump manufacturers?), I suppose have little economic motivation to do engineering and design work. Not to blame that original pump designer of long ago for a 60 mph design, but how about a design update from say, Berkeley? And where’s Berkeley when it comes to loaders? They offer pump upgrades designed for higher speeds, why not a couple loaders matched to their intake for several different speed ranges?
Gstark, I doubt there’s any danger within the pump industry of over-analysis or complexity. Regardless of economics, I still believe in better designs through engineering and analysis.
For example, your colleague mentioned a couple ideas off the top of his head, just based on you introducing the subject of pump intakes and loaders to him. Imagine how an experienced fluids dynamics and structural engineer with knowledge of jet boats working the problem over time could develop even better and safer loader designs? Or intakes or whatever.
Some here may’ve misunderstood my “more technology” campaign or use of the term “engineering” as some dude plugging numbers into a fancy CFD program and out pops a magical loader. Not likely.
Engineering is of course a lot more than computational fluid dynamics or finite-element analysis. About ten years ago I worked with a group of engineers in both CFD and experimental testing of jet engine components. Balancing experiment with analysis. So the benefits and limitations of both trial and error (experiment) and analysis are no mystery to me. And those engineers applied engineering knowledge, an understanding of the physics of what was happening inside the engine with a blend of both approaches to design ever faster jets. Now our pumps aren’t nearly as complex, but still a perfect opportunity for better “engineered” designs. Economics may be the barrier, but the lack of better-engineered pump technology or apparent progress towards that goal is still disappointing to me, and valid point in my opinion.
jer
[ January 05, 2003, 12:44 AM: Message edited by: LVjetboy ]

[gstark]

jer - you are absolutely correct. Unless Berkley, Legend, Agressor, AMT, or any other pump mfgr (did I leave any out, jeez I hope not) devote R&D $$$ to further development, the only advances will come from (1) the pros who work this stuff every day and (2) special interests who pursue advancement.
There is an economic reality to this topic and the payback of product development for these items is pretty sparse.
I think the problems with the pro's approach is that they likely have little influence on the inherent design of the castings. The tooling for these is existing and new patterns/molds are costly. Who foots the tab for this? Passing these costs to the limited consumer market just increases costs and most boaters that I know do not have unlimited or very large budgets. The pump inlet casting is an item that I am referring to specifically.
If one could contact some of the original Berk engineers and have an ongoing dialogue with them that would be great. Unfortunately, this involves business/trade information/secrets that they are not likely to share. At best, they could incorporate changes in their product if they saw fit.
And for the pro's to pass this to the manufacturers erodes their business base. After all, they are in business to do this very thing.
As far as any monkey being able to run a FE/CFD program, that is all so true today. I see too many engineers believing the boob tube without questioning the results. A reality check is always required - do the results make sense, is the behavior what I expect ? Often times inexperienced users run off with results that make no sense. For example, in 1980 I worked in the piping group for a major A&E firm designing nuke plants. I had oversight and review responsibility for stress reports. I received a stress report on a large valve from a vendor. This report stated that the valve would fail under a 1G load. Not only is this conclusion idiotic, as gravimetric loading is 1G meaning that the valve would fail under its own weight, but that a report could be submitted with this conclusion is disturbing.
So the point here is that analysis must be tempered with an experienced eye and always validated by test.
To brighten the day, I will take up the challenge of performing these analyses. This will take some time, as I will need geometry of loaders, in fact, if someone can provide a loader to me, that would be great. I will do the 3D solid modelling of the loader structure and begin with a modal analysis of the structure to determine the natural frequencies and the 1st - nth harmonics. This is the first step. The structural analysis due to loading will be more difficult as this will involve definition of the forces acting upon the loader and ramps. What speeds, angle of attack, etc. Bear in mind that these analyses are discrete in nature for one set of conditions and each run requires time to prep and reach a solution.
I think I will start with my own intake grate which is the stock Legend item. Just doing the modal analysis of this will be interesting.

[Hal]

These people may be interested in redesigning a safer, more efficient performace intake housing.
They manufacture the pumps. If they come up with a better pump design at the same time thats a good thing.
Being the intake housing is seperate from the pump I would'nt think that that designing a new fail safe and with the use of cnc machines the manufacturing of a new housing would be to big of a deal. But I don't know about that part.
All we need is some way to install and fasten a grate in that if there is a fastening or a weld failure the grate will not be able to drop down and turn into a water brake or a rudder.
Thats where the driver and if any, the passengers turn into projectiles. If your lucky you will be thrown out of the boat and come out of it only bruised and battered. Hopfully there will be someone near in a boat that can pick you up because you also have a good chance of the destruction (if its a lite weight hull and running at hi speed) or sinking of your boat at this time. A very good reason to always wear a life vest when you plan hot dogging around in your jet boat. Thats one way to be prepared for an intake failure because there is no warning before it happens.
Read this, its on thier web site.....
AN INTRODUCTION
At CP Performance we have literally decades of performance experience under our belts. Our selection of products is what has made us recognized worldwide. We know that one product cannot fit everyone's needs, that is why we distribute all of America's leading brands.
You have a choice! And when you have questions, we are here with the answers. Our entire staff shares in the research and development of many new products that we bring to market each year. At CP Performance we "research and develop", unlike so many others, that merely "research and copy".
We are constantly striving to bring you, our valued customer, the very latest in technology. You see, here at CP Performance, we are ALL boating enthusiasts. We test our products and those from the virtually hundreds of manufacturers products we sell. We also install what we sell. This gives us the knowledge to help you with your projects.
We strive everyday to keep our reputation as America's Leading Distributor of Stock and High Performance Marine Accessories. We value each and every one of you, our customers, and we want your satisfaction with every purchase you make with us. You can feel confident because we guarantee the quality of the items you purchase from us and will maintain low prices everyday.
Was there anything new left for CP Performance to do before the close of the century? The keen minds of the newly formed partnership combined their youth, experience and drive to catapult CP Performance into becoming America's leading distributor of stock and high-performance marine products, as well as the manufacturers of Berkeley jet drives and Hardin Marine Products.
Mike and Scott say their goal is to bring affordable prices back to the consumer. Together, they work for the greater good of CP Performance, not as individual owners -- they boast no egos. They are truly excited about marketing the finest products money can buy at wholesale prices, with an incomparable selection of parts available.
Mike and Scott both feel that jets are coming back strong. They have jumped at the opportunity to assist customers in rebuilding their units or the outright purchase of a new one. CP bought Berkeley Pump Company.
Today, the overall cost of the manufacturing of the parts for Berkeley has decreased approximately 30% with the use of CNC machines, and the quality of the product is remarkably superior. All the parts are manufactured in the U.S. with a complete guarantee.
http://www.cpperformance.com/ (800) 225-9871
[ January 05, 2003, 11:16 PM: Message edited by: Hal ]

[jweeks123]

hahahahahaha!
opps. excuse me for getting carried away by the CP post.
jw

[LVjetboy]

Gstark, pictures of your grate?
I'm just thinking, although exact excitation frequency hard to know, is there a most-likely range that can be known? And if you know that, couldn't new ideas for loader and mounting designs be tested throughout that most-likely range for failure?
Just rambling here as I have no clue. But my main thought is your efforts result in a set of general design criteria that can improve loader safety at high speeds? Or working with racers to test and improve loader designs? Who knows? I don't have your skills, but I do sense something is missing, and maybe this is an area needing the expertise you have.
jer

[LVjetboy]

Hal,
Sounds like a lot of marketing hype. Would be nice if someone in the business actually did all that. Now if that was my business, I'd certainly frequent this forums to find out what my customers were thinking...make sense? Wonder if they do??
I truly believe loaders CAN be designed without the failure problems some see today. This is not rocket science. Or even space shuttle science. :confused:
jer
[ January 07, 2003, 02:18 AM: Message edited by: LVjetboy ]

[Hal]

LVjetboy,
I did send them an e-mail 3 or 4 days ago with the URL to this forum topic and asked if someone would take the time to read it. Told them maybe they could shead some light on this subject. You would think they would be interested in what gstark has offered and want to get involved. But then it is big business and if the market is not there I don't think the safety issue alone will be enough to sway them into helping out. It would be nice if they would though. Maybe just some communication gstark would be good.

[Cs19]

This was a great thread from a long time ago. Its too bad we dont see threads like this anymore.
Everyone check/change your loader bolts this winter.

[CARLSON-JET]

This was a great thread from a long time ago. Its too bad we dont see threads like this anymore.
Everyone check/change your loader bolts this winter.
CS-19, Yes this was good reading indeed. thanks for reintroducing it. I agree more thorough examinations of our equiptment is in order every season end and opener is in order for our own and passengers safety. R.B.