Petawawarace
Petawawa ON
Joined: 04/25/2005
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STAY ON TOPIC SCROGGY....GEEZ
DeJongMotorsports.com
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tuner78
Weyauwega - WI
Joined: 02/03/2006
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Very interesting topic - seems I'm not the only one growing weary of the off season (Bring on the ice and cold!!!).
Anyway, all of the responses are correct and that's what make this such a cool thing to be involved in. Hp vs Torque vs Rpm vs Handling. All play into the the game in one form or another and there specific importance depends on how you initially attack the set-up. Handling for the most part is based on driver preference and style because if the driver ain't likin it he ain't gonna drive it, so I'd say the best possible handling you can attain per the driver is a given. On the power side of things I believe that everyone does it a bit different depending on what has worked for them in the past and what has not, like the old saying goes "stick to what ya know". However, when ya need a little more (and we always do!) ya gotta think outside the box and racers are some of the best people I know for that!
Here's yet another approach for you Tuner/Engine builder types to contemplate. It's true that the modern day CVT drive system although very well suited for the application and very efficient within it's design parameters, tends to loose efficiency at the higher rpm's. It varies a bit between mfg's but for the most part efficiency starts to fall off in the mid 8000 range and by 10,000 is notable. So, here's the question. Given a clean sheet of paper, should you build the power package (porting, squish, compression, ignition curve, pipes or pipe, etc, etc, etc.) to peak or compromise if you will between the HP & Torque curves as close to the peak efficiency of the drive system as possible? Understanding of course that the entire equation is a moderate compromise of all of the variables, but eliminating loss through the power transmission system could provide gains by not needing to generate power that ends up wasted via heat/energy in the belt and clutches. Additionally, a more efficient power transmission system should create an opportunity for greater pull off the corner, and who couldn't make good use of that twice per lap.
Just food for thought to help pass the dog days of summer!
WINNERS:
Show up prepared
Are never intimidated
Don't give up
Are professional
Keep the faith
Team Behn RacingTuner78
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Flatout
Ottawa Ont.
Joined: 11/20/2001
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Tuner78 that is interesting.... I wonder if anyone has thought of "tuning for maximum output" (lets say at 11,000 rpm) and incorporating a reduction drive that slows the clutches down to the more efficient 7,500 rpm. The new belts would surely handle the increased torque and the engines could now sing up where they make the most power. Now all we need is a reliable lightweight gearbox that doesn't rob any power!
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Petawawarace
Petawawa ON
Joined: 04/25/2005
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Yamaha already has it (not sure about the lightweight part though). The 4 strokers spin up near 14,000 don't they? and they have to reduce drop the rpm's so the clutch will stay together.
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tuner78
Weyauwega - WI
Joined: 02/03/2006
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Wow - talk about brainstorming! There's already one speed reducer onboard most sleds in the form of a chain case. What about changing it's current role as follows: Mount the driven clutch on the axle shaft, mount the primary clutch on a stub shaft at the proper center distance (I think "Redline" did something similar to this) then gear reduction drive the stub shaft with the engine. Primary gear reduction could be achieved via timing belt drive or similar. A 3:1 ratio may be a good starting point if you need 11,000 rpm at the source, this would allow the primary clutch to operate at 3666 rpm. If some variation of this could be worked out there would be zero added weight.
May even shed a pound or two because stub shaft could be much shorter than the typical jack shaft that's the width of the chassis.
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USSA155
Wisconsin
Joined: 08/25/2006
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Intresting thoughts guys. We actually looked into this when we were working with a Yamaha V-Max 4 drag sled. I big problem is the speed. you just can't uase any reduction system. Chain drives (even when submersed in an oil bath) will not hold up at these speeds (chain speed is too high and the pins will tear themselves apart). This leaves you with a gear reduction. In order to acheive proper life expectency you would have to include a safety factor of at least 4 for use directly coupled to a powertrain. Now factor in crank flex, and you end up with a fairly loose fit gear set that is quite wide and would need to ride in an enclosed gear box that would some how bolt directly to the end of the crankcase.
Just and engineers perspective
Josh
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Flatout
Ottawa Ont.
Joined: 11/20/2001
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What about a polychain belt drive?
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tuner78
Weyauwega - WI
Joined: 02/03/2006
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Poly chain or similar is what I had in mind. Most of the custom chopper guys have been using them on the primary drive for years. I understand the rpm's are lower than we're talkin about here but the torque numbers in most cases are higher. Also, poly chains have been in use as blower drives from street use all the way up to top fuel (plenty of rpm there). Anyone have any personal experience with this type of drive?
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Spy-Guy 74
Almost in Canada, MN
Joined: 07/25/2003
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We used a gates polychain belt on our champ sled a couple of years ago. Works very well, except in the very rough and we all know it gets rough in the Sunday finals. When your track free wheels because its off the ground and then hits tends to blow the belt. After while your driver gets gun shy as it tends to throw you over the bars when the belt brakes. Wouldn't see me going back to this set up again.
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Jamon
St-Jean (Quebec)
Joined: 04/27/2005
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I think it would snap when launching... Poly are good to transfers continuous power. And also, you need large pulleys so you don't bend the strap to much, this means alot of room taken. It should be an enclosed gearbox like said before.
Team JL Racing, #26
Jason Levac, Driver-mechanic-fabricator-Tuner.
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