New Rotax clutch

Joey Guyon · Posted: Mon Jan 05, 2009 6:56 pm Post subject:

It was with a used old style and a new new style (good vocabulary)

JG

Ray Chiappe · Posted: Wed Jan 07, 2009 3:28 pm Post subject:

It looks like for now no one can sell me just the new gears. Not until March!

Andy Seesemann · Posted: Wed Jan 07, 2009 3:42 pm Post subject:

Really?

You never called me.....

A
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Really Good Guy.

Ray Chiappe · Posted: Thu Jan 08, 2009 11:00 am Post subject:

Thanks Andy, you came through again!!

Robert Brooks · Posted: Tue Jan 27, 2009 12:29 pm Post subject:

We broke our old style clutch in the Saturday race @ the PHX COtA race and for Sunday switched over to the new style metal to metal and the new gears.
ZERO difference in performance, lap times, etc..... The only thing my driver said was that the new clutch is noisy! lots of metal to metal clanging, he could not even hear the exhaust.
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Keith Buffo · Posted: Tue Jan 27, 2009 12:44 pm Post subject:

With the old clutch, that sound was usually the drum hitting the starter gear because the thin spacer/washer behind the drum was forgotten. (I think I broke a clutch that way once, but not because of a missing spacer but a poorly made aftermarket drum.)

The big (and only) difference this clutch is supposed to make is in reliability. As you lucky folks race in warmer climates, please keep the rest of us posted on how robust the new clutch is over the long-term.

Walt Gifford · Posted: Tue Jan 27, 2009 8:20 pm Post subject:

How thick is the starter gear plate where the three bolts go through 'cause that looks like a trouble spot.

Gif Cool

Chad Stapleton · Joined: 19 Jul 2001 Posts: 4403

Walt Gifford · Posted: Wed Jan 28, 2009 7:58 am Post subject:

[quote="Chad Stapleton
Steel timing gears maybe ??

( I still cannot figure out the reason for that change in connection with the clutch ? Confused

)[/quote]

I've seen no reason given in physical science other than the plastic gears may be less reliable anyway. They say the new clutch is heavier but smaller dia and testing has shown no difference in performance so, it's got the same inertia. That leaves the way it locks up as the difference? If it lets the motor rev up more then hit hard, that might shock the gears a little more. Anyone with a mycron want to check? I think they just put 2 upgrades in the same discount package and everyone assumed there was a connection. That's ok because rotax does the thinking for us so, just buy the new parts then go have fun.

Gif Cool

Chad Stapleton · Joined: 19 Jul 2001 Posts: 4403

Walt,
some of the highest loading these gears ( + the clutch and the rest of the motor) ever will see, is when you lock up the brake momentarily on a high speed corner entry ( bumpy track).
The motor can go from 10-12k rpm to a momentary dead stop, then instantly get jerked back up to 10k rpm again if the clutch doesnt drop out ( mine doesnt !). Sometime this happens every lap with many karts doing exactly the same thing on the same corner.
I dont recall the plastic gears ever being a reliability problem for Rotax, so there must be some other reason for the change ??
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Chad
"Those of you who think you know everything are annoying to those of us who do !!"

Bruce Woodrow · Posted: Thu Jan 29, 2009 9:08 am Post subject:

I think you will find that the inertia of the new clutch is a little higher than the old one, which will effect the torsional vibration characteristics of the clutch/crank/balance shaft system, reducing the speed at which resonance occurs (closer to the 14,000 rpm limit), thus necessitating the stronger gears.

Bruce

Michael Boone · Posted: Thu Jan 29, 2009 12:03 pm Post subject:

I was at the Sodi Shop today and asked why the change to the metal gears? (They are the importer for France) One of there motor builders told me it because they've had a problem with the plastic gears braking.

They've changed 15-20 set this year alone a cause of pretty much what Chad has pointed out, He also said the old clutch will work with the new gears. That's also why it's sold as a kit: clutch & gears.

MB
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Chad Stapleton · Joined: 19 Jul 2001 Posts: 4403

Plastic gears have a few advantages... weight, cost, noise damping etc etc, but one major benefit of plastic is that if they do fail, the only damage they do is to themselves..hence easy & cheap to repair.
If a metal gear loses a tooth or chips a edge etc , it likely going to wreak havoc with other components Sad

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Chad
"Those of you who think you know everything are annoying to those of us who do !!"

Blake Choquer · Posted: Fri Jan 30, 2009 10:15 am Post subject: New Clutch

Even though the new style clutch is lighter, the extra rotational mass from the metal gears produces the engine to have less HP on the top end.

We spent a day dynoing the two clutches and my choice is still the old clutch. Find a set of plastic gears that are pre 2008 and you are good to go.

Sincerely,

Blake Choquer
www.karttechnik.com

John Savage · Posted: Fri Jan 30, 2009 10:44 am Post subject:

Blake, that Dyno will kill you Shocked

No guard on the rotor Shocked

No exhaust fume extraction Shocked

No engine cooling fan Shocked

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