Damn Torque!

A general, non-powerplant specific, discussion on airboat technology, ie., hulls, rigging, polymer, etc..
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airduds
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Damn Torque!

Post by airduds » Wed Dec 16, 2009 4:28 am

After reading this board and a couple others over the years I've reached the conclusion that (that word) and it's relationship to power is the most misunderstood concept on earth. The pity is it's not that complex, in fact it's really simple. So if the problem isn't with concept, it must be with the word itself.

So I'm going to use a new term in place of that other word. Cylinder pressure.

In a reciprocating engine, what is commonly called that other word is in reality nothing but cylinder pressure. That's all. You can make it more complex by saying something like at a given instance in time it's the cylinder pressure times the circumference of the cylinder times the distance from the centerline of the crankshaft to the center of the crank throw times the trigonometric sine of the angle of the crank throw in relation to the bore of the cylinder. But really, it all boils down to cylinder pressure.

You can move a lot of air with a prop even at a low rpm if your cylinder pressure is out the roof but we all know the problems of too much cylinder pressure like pre-detonation. Or you can move a lot of air with a prop with not so much cylinder pressure if you spin the engine really fast but then it becomes hard to make things stay together.

So the trick to building a reliable engine that can move a lot of air with a prop is to start with good parts that can change directions many times per second without coming apart; and at the same time keep cylinder pressures low enough that you can start the fire when you choose and have it burn slowly and evenly enough to keep from acting like a sledgehammer or a blowtorch.
Hard times create strong men. Strong men create good times. Good times create weak men. Weak men create hard times.

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Waterthunder
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Re: Damn Torque!

Post by Waterthunder » Wed Dec 16, 2009 7:35 am

Cylinder pressure is very important but I wish it was that simple nothing ever is just one thing! You can build a motor with tons of cylinder pressure that doesn't detonate, like a diesel or a torque monster caddy motor but if you only follow that formula and only worry about cylinder pressure you can end up with a motor that quits pulling at 4,500RPM's. Case in point all you gotta do to have big cylinder pressure is have small cylinder head port, small cam, small intake, small carb and that motor will make ton's of cylinder pressure but will be a terd over 4,500RPM's I think I have built enough motors to have learned it's the whole combination! When I was younger about once a year I thought or read that one thing was the ticket and after trying it when building several motors in the end always found out it's never just one thing everything is different with every application and and combination. This is why many engine builders stick with one specific application it takes a 1/10 of the rnd and is much simpler! I will say cylinder pressure is a very big factor but with anything in a motor it's the sum of the whole combination!
THE PROOF IS IN THE PROP!

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cntry141iq
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Re: Damn Torque!

Post by cntry141iq » Wed Dec 16, 2009 8:19 am

I will tell you one thing ... if you wanna know about cylinder pressure all you gotta do is get around Stan when he is eatin sardines, raw onions, pork & beans and washin it down with a beer ... yep that is some serious cylinder pressure right there I don't care who you are and if he adds a couple of pickled eggs to the mix ... OMG it will take paint off ...
Don't waste your time ... it is the only thing you can't get more of
.. if it accidentally looks like I gave advice please ignore it .. and notify me immediately

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Waterthunder
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Re: Damn Torque!

Post by Waterthunder » Wed Dec 16, 2009 8:21 am

CT141 you may have found a case were cylinder pressure is a very bad thing!!! Let alone dangerous!
THE PROOF IS IN THE PROP!

"If you copy someone you will only achieve what has already been done."

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deepsea diver
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Re: Damn Torque!

Post by deepsea diver » Wed Dec 16, 2009 11:00 am

Stan's getting old, he better be careful. He's goin to "$hit him self" on that diet! :lol: Now you know why the lab rides up front!

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plumcrazy
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Re: Damn Torque!

Post by plumcrazy » Wed Dec 16, 2009 11:35 am

well deep sea i love to read tech stuff on motors, but to understand tq just hold a 540 piston in your right hand and a 350 piston in your left, and think only one piston is doing the work at any givin time in your motor, and it all becomes so clear . airpump baby thats all they are 8)

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