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Thread: Flywheel or Flexplate

  1. #21
    396_WAYS_TO_SPIT
    well I can just say that I run a "heavy" flywheel in my boats and they never let me down Im sure the flexplate would be better but "if it aint broke, then dont fix it"
    MP, you do have a point in your last post

  2. #22
    Klass Klown
    You obviously KNOW nothing about elementry school english........torsional harmonics.......hmmmmmmm, lets see a harmonic is a vibration, so the more weight you spin up has more harmonics? I didn't think vibration was something you wanted in a rotating mass. I remember the Ford Courier trucks, so under powered they had to put a 40 lb flywheel in them to keep from stalling the motor when you let the clutch out......Now, explain to me what advantage this additional weight has on a rotating mass in a boat. MP
    Ok M.P, let's see have you ever seen a one lung very very old motor with a FLY WHEEL ( hence the name)??? With more rotating weight ( once it is spinning) ( not perpetual motion) let's say in a car.. You leave the line at let's say , well, you load the clutch or trans brake up to 6500 rpm, Now a heavy car which could use the extra rotating mass coupled to the tranny will leave and lug the motor to say 5000 rpm depending on tire size, efficiancy of the set up tire spin etc. would benefit with the heavier rotating mass as opposed to a lighter flex plate.. Would you agree???? So in a boat the question is once the rpm is attained would a heavier flywheel help or hinder?? Without the extra weight it would pull the motor down quicker Under a load correct? So exactly how much the extra weight hinder's the overall acceleration is what's debateable... Can you HONESTLY TELL ME YOU KNOW BASED ON TIME SLIP OR LAP TIME?? Your post is very DEBATEABLE!!! And I honestly think you are chartering in grounds Unbeknown to you!!!!!!!!!!

  3. #23
    Klass Klown
    One more thing, you take the pro stock class in N.H.R.A they run lenco's, Liberty's etc, Do you not think in the most Competitive class in N.H.R.A if rotating weight was such the issue i.e. above they would be running ---oh let's say an automatic HA HA lol Lmao Guess again!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!! I guess boats are more of a science than prostock cars!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! ENOUGH SAID

  4. #24
    Moneypitt
    And I honestly think you are chartering in grounds Unbeknown to you!!!!!!!!!!
    Ah, the key word here is Ground. In both your examples you are refering to moving a mass on the ground. A direct conection to the ground, flywheels, clutches, driveshafts, and of course gears and tires. IMO,you can not compare the requirements of automotive performance and boat performance, nor can you compare the rotating mass required to bring a boat out of a corner with the inertia required to launch a vehicle. You mentioned the need to maintain Rs through a corner, but you forget the massive power to weight ratio advantage in a boat. With hulls weighing around 400 lbs bare, and everything added is primarily for purpulsion, a boat just doesn't need the rotating mass. In fact, having a motor that will lay down suddenly when you want it to can be a tremendous advantage. Example: Down the front straight, green flag start at about 60 MPH and 5/16ths of a mile into the first turn. The motor goes to 7500, the speed is around 100 as you come to the turn pin. You're on the inside lane with 5 or 6 boats outside you. You drive the boat as deep into the turn as possible, allowing for distance to break your speed down to almost nothing to do a u turn in a boat length, and stay in your 10 foot lane, on BOTH sides of the pin. IF your motor wants to continue spining because of the "rotating mass", you are not going to be assisted in slowing by the reduced speed of your prop, and would have to lift way too early to keep up with the boats on the outside, that can keep their Rs up as they turn much wider. Once you lose the lane, or fall behind the pack you are in for a rough ride for the rest of the race, even if you have the power to stay with the pack you are just far enough behind to never find any good water. By the same token, you must be able to re rev the motor like turning on a light switch, or once again, you will fall back. Please remember these boats are geared and proped to come to RPMs right now. And again I say, in a boat, there is no reason to add additional weight to a rotating mass, UNLESS the combination is way under powered for what it is trying to pull, and even then it would only apply while initial engagemeent is taking place. Once the boat is in motion under power it will get drier and drier and require less inertia to maintain RPMs. I think we are trying to compare apples to oranges.....Weight issues aside, a rigid flywheel does have it's advantages in a boat while starting, IF, flexplates are flexing away from the starter gear. As I said initially, I have ran stock GM flexplates with stock GM starters, cranking a 13.1:1 motor with 37* degrees in a locked mag without any problems for years. I try very hard to make the rotating mass as light as possible, and it revs, click on, click off, click on, click off........MP

  5. #25
    Squirtin Thunder
    Cars like heavy fly wheels !!!
    There are lots of good points, but I will make one also. The FLYWHEEL is heavy, much harder to slow down, FLEXPLATE is light much easier to slow down. And the same with acceleration. Now if you are trying to beat the next guy out of the corner you want the snappiest throttle responce as possible, but when catching air because of rough water you want to drop Rs as quick as possible to protect parts. In NHRA, IHRA and many more drag racing series it really does not matter being the rubber is your breaking point and basically stays loaded to a degree even when you haze the tires. In Off-Shore racing they have an extra guy to run the throttles and they still have problems. In a Jet Boat you will destroy a impeller with a heavy Flywheel, because you can not slow the rpms quick enough, 396 has a perfect example of that somewhere. By loading and unloading hard at high rpm, 5500 and above they will crack and break.

  6. #26
    Klass Klown
    And I honestly think you are chartering in grounds Unbeknown to you!!!!!!!!!!
    Ah, the key word here is Ground. In both your examples you are refering to moving a mass on the ground. A direct conection to the ground, flywheels, clutches, driveshafts, and of course gears and tires. IMO,you can not compare the requirements of automotive performance and boat performance, nor can you compare the rotating mass required to bring a boat out of a corner with the inertia required to launch a vehicle. You mentioned the need to maintain Rs through a corner, but you forget the massive power to weight ratio advantage in a boat. With hulls weighing around 400 lbs bare, and everything added is primarily for purpulsion, a boat just doesn't need the rotating mass. In fact, having a motor that will lay down suddenly when you want it to can be a tremendous advantage. Example: Down the front straight, green flag start at about 60 MPH and 5/16ths of a mile into the first turn. The motor goes to 7500, the speed is around 100 as you come to the turn pin. You're on the inside lane with 5 or 6 boats outside you. You drive the boat as deep into the turn as possible, allowing for distance to break your speed down to almost nothing to do a u turn in a boat length, and stay in your 10 foot lane, on BOTH sides of the pin. IF your motor wants to continue spining because of the "rotating mass", you are not going to be assisted in slowing by the reduced speed of your prop, and would have to lift way too early to keep up with the boats on the outside, that can keep their Rs up as they turn much wider. Once you lose the lane, or fall behind the pack you are in for a rough ride for the rest of the race, even if you have the power to stay with the pack you are just far enough behind to never find any good water. By the same token, you must be able to re rev the motor like turning on a light switch, or once again, you will fall back. Please remember these boats are geared and proped to come to RPMs right now. And again I say, in a boat, there is no reason to add additional weight to a rotating mass, UNLESS the combination is way under powered for what it is trying to pull, and even then it would only apply while initial engagemeent is taking place. Once the boat is in motion under power it will get drier and drier and require less inertia to maintain RPMs. I think we are trying to compare apples to oranges.....Weight issues aside, a rigid flywheel does have it's advantages in a boat while starting, IF, flexplates are flexing away from the starter gear. As I said initially, I have ran stock GM flexplates with stock GM starters, cranking a 13.1:1 motor with 37* degrees in a locked mag without any problems for years. I try very hard to make the rotating mass as light as possible, and it revs, click on, click off, click on, click off........MP
    Answer my question have you ever timed a lap using either???????/ We are comparing apples to oranges I just dis agree with some of your advice.. So I would assume you use a 49# crankshaft and aluminum rod's correct?? As well as the longest possible rod length and lightest piston?? Just curious because there are more than one way to skin a cat.

  7. #27
    Moneypitt
    Answer my question have you ever timed a lap using either???????/ We are comparing apples to oranges I just dis agree with some of your advice.. So I would assume you use a 49# crankshaft and aluminum rod's correct?? As well as the longest possible rod length and lightest piston?? Just curious because there are more than one way to skin a cat.
    Circle racers do not race the clock, they race each other. Lightest piston, well, they are hollow dome; .250 long, lightest steel rods I can find, (Aluminum rods don't really have the life expectancy we require), and we can't afford 49# crankshafts. When running an apple, IMO lighter is better, and I understand your dis agreement with my advice when driving an orange, but it is only MY opinion, as I stated in the first post, and my opinion works for me as applied to apples. I have driven oranges, have you ever driven an apple? MP
    PS: If heavier is better, why were aluminum flywheels created for oranges??

  8. #28
    Senior Member
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    Bottom line here is that the extra mass has to be accellerated whether rotating or linear, it's all in what your trying to accomplish. IMHO I perfer the lighter mass approach, makes for quicker accelleration period on water.
    Sleek

  9. #29
    Klass Klown
    Circle racers do not race the clock, they race each other. Lightest piston, well, they are hollow dome; .250 long, lightest steel rods I can find, (Aluminum rods don't really have the life expectancy we require), and we can't afford 49# crankshafts. When running an apple, IMO lighter is better, and I understand your dis agreement with my advice when driving an orange, but it is only MY opinion, as I stated in the first post, and my opinion works for me as applied to apples. I have driven oranges, have you ever driven an apple? MP
    PS: If heavier is better, why were aluminum flywheels created for oranges??
    Yes I have, back to my point. I understand your point And agree to a certain extent with your advice I would not completely rule out a flywheel if I were on a budget and i was already in posession of one! As you cannott afford a 49# crank a Titanium rod, you obviously use what you can afford!! Although it has been my experience that does not always get you to the winner's circle!! :rollside:

  10. #30
    Taylorman
    I just wanted to know if i have a flywheel or flexplate guys. Wow this has gotten to deep. Heres my vote, lighter is better in an engine. End of story. You two are giving me a headache.

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