730 Hp

[Bow Tie Omega]

The gas trubine example, while very true, either produces thrust, like in a jet, or is coupled to a gear reduction box which acts like torque, like in a helicopter, a much better explanation of your theory though miketsouth, thanks
So help me understand this. You have 2 engines, on is all hp and no torque, while the other is the same amount of HP and substantially larger amount of torque over the entire HP curve. Now, put the same load on these motor, 1:1 ratio, single gear drive, pulling 10 thousand pounds, which one will win and why

[miketsouth]

Accleleration Horsepower. Check it out.
Scroll down to 'Acceleration Horsepower' (http://www.grapeaperacing.com/GrapeA.../miscpower.cfm)
mikeT

[cheech]

agreed it is not the dogs fault. he did not chose his owner.

[Bow Tie Omega]

That is exactly what I was saying, after looking at your recommended web site, torque is just as important as HP, and while drag cars can just gear a car to compensate for lack of torque, a jet boat can not, therefore, unlike a drag car motor, you need to include torque in the jet boat motor building equation

[miketsouth]

Originally posted by Bow Tie Omega
The gas trubine example,
So help me understand this. You have 2 engines, on is all hp and no torque, while the other is the same amount of HP and substantially larger amount of torque over the entire HP curve. Now, put the same load on these motor, 1:1 ratio, single gear drive, pulling 10 thousand pounds, which one will win and why
Trick question?
I know what you mean, though.
Go to a tractor pull and see how the Gas Turbines do. They kick ass. (I think most are limited to 30%) The prime mover in Gas turbines may be doing 50,000rpm. Very little torque. But your right, in certain applications HP over a good range (flat torque curve) is desirable. Dont matter in a jetboat at all.
In the theorietical recip I/C engine, power comes with RPM. More strokes, more power. Flat torque curve.
For more reasons than i know or understand this just dont happen. I suppose a well designed engine has a flatter torque curve, something to look for.

[miketsouth]

Originally posted by Bow Tie Omega
That is exactly what I was saying, after looking at your recommended web site, torque is just as important as HP, and while drag cars can just gear a car to compensate for lack of torque, a jet boat can not, therefore, unlike a drag car motor, you need to include torque in the jet boat motor building equation
The recommended site only applies to accelerating engines, or engines that have to change speeds while doing their work.
Doesnt seem to apply to jetboats.
In the jetboat you mash it, it comes up to rpm (hp output) and thats it. You want that speed to be at the maximum HP output.
Who cares how much HP it has at 3000 RPM. The pump wont absorb much HP at 3000 RPM. Or 4000RPM (impeller dependant). The HP absorption VS rpm curve not linear at all. Looks to me it goes up as the square or cube (2xrpm = 4 to8 x hp)
mikeT

[Bow Tie Omega]

Talking with several people in the past, that is exactly why jet boat motors are built differently then lets say a V-drive motor or I/O. It was the torque . Look at HB Jets motor which was built by DNE, they included Torque over a very broad band at 600 ft/lbs plus from 3500-6500, which is considered the operational range for lake jet boats. I do not agree with the "you just get in a jet boat and mash the pedal" . Hp is great as long as you do not have any load on the motor, but as soon as you have a significant load on the motor, and contrary to popular belief, a jet pump can and does put a load on a motor, you need torque to help turn it. SOmeone used the example of a torque wrench earlier and that they could generate 300 ft/lbs with their hand. But they had to use torque to show torque

[miketsouth]

Originally posted by Bow Tie Omega
Hp is great as long as you do not have any load on the motor, but as soon as you have a significant load on the motor, and contrary to popular belief, a jet pump can and does put a load on a motor, you need torque to help turn it. SOmeone used the example of a torque wrench earlier and that they could generate 300 ft/lbs with their hand. But they had to use torque to show torque
Horsepower IS load on the motor. Torque is load on the motor shaft. Two completely different things, yet tied together.
Jetboat impellers do put a load on the motor, i am not confused about that. Just not linear. REAL EASY to turn it slow, REAL hard to turn it fast. Not a 1:1 realationship at all.
The shaft transmits the horsepower, i know that too. If the shaft can turn more rpm it takes less torque to transmit the horsepower.
It was i that used the example of being able to produce torque and not horsepower. (as soon as the wrench turns, there is horsepower (work done), when it stops there is still torque, but no horsepower.
Using torque to show torque is an acceptable and revealing way of demonstration (i think)
In sizing a jetboat impeller, or finding out how fast the boat can potentially go, HP is the only thing you need to look at. One way of looking at it is torque times RPM. It is more direct to look at the HP though. If the horsepower curve it pointed, getting the impeller exactly right is important and difficult. If the HP curve is flatter, it is not so hard, and i would give up a few HP to get a little lower RPM and a longer lasting engine.
mikeT

[Bow Tie Omega]

I am enjoying this conversation with you because I am learning. I thought that the torque wrench example was a good one also. Listening to what you are saying, you seem to support that torque is important and then you seem to imply that torque is not important, maybe I am misunderstanding you. I will not argue that HP is not important, it is very important. I think the horsepower to torque importance ratio is close to 50/50, maybe even a 60/40 in favor of HP in a jet boat motor. WHat I had read above, I forget who said it, was that torque is a non factor. That, I am in total disagreement with. I am in total agreement with the theory that HP and torque together are best, I believe that torque will help a motor reach its full HP/rpm potential. We already know that torque and HP work together, otherwise there would be no measurement or mention of torque. I have seen incredible torque numbers matched with average HP numbers move 200000 pounds at 40 mph with relative ease. Anyone here telling me that torque is not a contributing factor to a motor reaching its full potential will have a hard time selling me on that after I have seen what 400 hp w/ 2000 ft/lbs of torque can move at 40 mph. ANd on that note, I have to go, I have webbing to shoot in the boat.....Joe

[cruser]

Maybe the problem here is concept that torque or HP are not separate things that can be produced, one without the other. This is not true when the force is transmitted using a crank shaft like in out favorite V8s. You need both components if you want to get work done (push water out the nozzle).
In the example of the torque wrench, the torque is the force applied at the end of the wrench. As the wrench starts to move, work is being accomplished (the bolt is turning). To express the power being expended that does this work, we say that power is the application of force over a distance. Here the distance is the arc of the end of the torque wrench. If you are applying 300 lbs of torque to the wrench and move the end of the wrench at 1 rpm, you are producing (300*1/5252) ~.06 HP. Better hit the gym I guess.
In the case of the turbine turning the rotors on a helicopter, Both components do exist. The turbine shaft is turning 50K rpms as you said, but still produces 'some' torque, otherwise the shaft would not turn. So, if the turbine produces a minimal amount of torque, say100 ft/lbs, the power at 50000 rpms still gets big, 100*50000/5252 = 952 hp. Quite a bit of power if you ask me.
cruzer