Apex gear reduction.

[Darren Betker]

I realize the apex has a gear reduction to bring the clutches down to a limit to save wear but is there any gears available to add a little more speed? Would think yamaha reduced a little more then what was actually needed to stay well within that safe zone. Wouldnt that be a good way to get more piwer/speed out of this sled?

 

[Macheater]

Yamaha slowed the pto down because a cvt and belt cannot handle the rpm's that the Apex engine spins at. CVT's are only good up to about 9500 rpm. And they begin to lose efficiency well before that.

If you want more speed you change chaincase gear ratio's.

 

[Riceburner]

Yamaha slowed the pto down because a cvt and belt cannot handle the rpm's that the Apex engine spins at. CVT's are only good up to about 9500 rpm. And they begin to lose efficiency well before that.

If you want more speed you change chaincase gear ratio's.

Agreed.

 

[Darren Betker]

so if just before 9500rpm is the magic number then what exact rpm did they reduce it down to? I had heard 8500. was just wondering if there is any room to work with. Guess not tho if nobody has ever mentioned being able to change tooth count 1 or 2 to get just that extra bit more. Crazy what guys will think of doing to squeeze every last hp.

 

[cannondale27]

You guys are so lucky to have the gear reduction. Even all the race organizations banned it as a unfair advantage back in the day. If you really want to spin clutch faster just mod the motor and ignition to spin the motor a bit faster Darren.

 

[Macheater]

I used to know what the reduction number was from memory but that was years ago. Now I would have to look it up. There is no "magic number" with clutch rpm. The cvt as with anything else eventually reaches a point of diminishing returns on a efficiency vs rpm scale. I haven't seen one for years but, I seem to remember that Olav Aaen's clutch book had such a graph. If you have ever seen a dyno chart, it looks similar to that. The efficiency rises, reaches a peak, levels and then declines. If memory serves, the decline starts right around 7500 rpm. That number is not set in stone, it may very slightly based on different clutch designs/setup's. That is 1 reason (but not the only) that many of the big 2 stroke twins make peak power right in the upper 700o to lower 8000 rpm range. I even saw 1 of the big cat engines peak hp around 7200 rpm a few years back.

The higher clutch speed rpm's are for the racers where making big hp usually requires big rpm numbers. But even here they must balance several factors, such as hp gained by the engine vs lost by the transmission. In decades past, belt longevity was also a factor since a blown belt lost the race. These days a belt can hold together but, still loses efficiency at higher rpm.

Back to the Apex. I'm fairly certain that clutch speed was a number that was highly studied and tested when the first rx-1 was built. Again, they (Yamaha) had to balance a number of different requirements. Component durability/longevity, efficiency, mass, etc. Then after testing, a number (reduction ratio) was established that would give the best "balance" of requirements for the production sled.

Slowing the clutches down to a more "2 stroke like" speed was absolutely necessary for the Apex. But, I'm willing to bet that even doing that came with a few tradeoffs as so often happens.

End result is that the clutches spin at a certain speed relative to the engine for a reason(s). To my knowledge Yammi does not make other selections available. And if there was any advantage to changing, some aftermarket company most likely would have stepped in by now.

 

[cannondale27]

I used to know what the reduction number was from memory but that was years ago. Now I would have to look it up. There is no "magic number" with clutch rpm. The cvt as with anything else eventually reaches a point of diminishing returns on a efficiency vs rpm scale. I haven't seen one for years but, I seem to remember that Olav Aaen's clutch book had such a graph. If you have ever seen a dyno chart, it looks similar to that. The efficiency rises, reaches a peak, levels and then declines. If memory serves, the decline starts right around 7500 rpm. That number is not set in stone, it may very slightly based on different clutch designs/setup's. That is 1 reason (but not the only) that many of the big 2 stroke twins make peak power right in the upper 700o to lower 8000 rpm range. I even saw 1 of the big cat engines peak hp around 7200 rpm a few years back.

The higher clutch speed rpm's are for the racers where making big hp usually requires big rpm numbers. But even here they must balance several factors, such as hp gained by the engine vs lost by the transmission. In decades past, belt longevity was also a factor since a blown belt lost the race. These days a belt can hold together but, still loses efficiency at higher rpm.

Back to the Apex. I'm fairly certain that clutch speed was a number that was highly studied and tested when the first rx-1 was built. Again, they (Yamaha) had to balance a number of different requirements. Component durability/longevity, efficiency, mass, etc. Then after testing, a number (reduction ratio) was established that would give the best "balance" of requirements for the production sled.

Slowing the clutches down to a more "2 stroke like" speed was absolutely necessary for the Apex. But, I'm willing to bet that even doing that came with a few tradeoffs as so often happens.

End result is that the clutches spin at a certain speed relative to the engine for a reason(s). To my knowledge Yammi does not make other selections available. And if there was any advantage to changing, some aftermarket company most likely would have stepped in by now.

Very well put Macheater. Something many Viper guys need to learn before they waste their money and possibly motor.

 

[Darren Betker]

companies like yamaha lean to the side or reliability over performance every time. so they woulda geared down past what other companies woulda just to maintain that reliability. So that tells me that there is definately room for improvement. Thats why im surprised that people havnt figured this out and yaken advantage of it. They have relibuility rated above all else.....said by yamaha execs over and over .....makes a guy wonder if and how much a guy could play around with the gear reduction to get that leg up. but i guess im wrong if even aftermarket companies wont touch it.

 

[gouldsjett1]

Greg santry of gns Enterprise used to sell different gears to change ratios.