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Pingu
08-28-2009, 09:38 AM
We are looking into trying a 5 or 6 speed transmission instead of the polaris f-n-r's that we keep breaking. So if you know anything that has worked or didn't work please mention it here.

Thanks

nutz4sand
08-28-2009, 10:22 AM
http://www.minibuggy.net/forum/welcome-mat/9072-just-old-fart-florence-oregon.html

minibajaman
08-28-2009, 11:22 AM
We are looking into trying a 5 or 6 speed transmission instead of the polaris f-n-r's that we keep breaking. So if you know anything that has worked or didn't work please mention it here.

Check out USF's setup, they are the most sucessful team running a manual gearbox. It seems like most teams running a manual tranny are using one from some sort of ATV or dirt bike.


http://www.minibuggy.net/forum/welcome-mat/9072-just-old-fart-florence-oregon.html
This is the Baja SAE area, so that's not very practical.

nutz4sand
08-28-2009, 12:25 PM
Oh. Ok. Did not realize that.

I guess my question is what are you doing wrong to break a Polaris gearbox with a 10 horse motor?

minibajaman
08-28-2009, 12:32 PM
I guess my question is what are you doing wrong to break a Polaris gearbox with a 10 horse motor?

I'm not sure but the Polaris gearboxes seem to have high failure rates when used in Baja SAE cars. It has less to do with horsepower and more to do with the application and shock loads and general abuse the cars see. I would say that a buggy sees more abuse in a weekend of Baja SAE competition then most ATV's would see in 5 years of normal use. In the two years prior to me joining the team I was on (back in 2001) the team used the Polaris HLNR with chain output gearbox and it broke on them quite a few times.

nutz4sand
08-28-2009, 12:39 PM
I would have to see its setup and hows its driven cause I KNOW they are tougher than that. Something baout the setup must be tweaking it.

I do not believe more abuse in a weekend than a ATV in five years.

I weigh 280 plus pounds and I HAMMER my 400 pound 400cc two stroke quads (Polaris 2wd Trailblazer and Scrambler 4wd) (both slightly built) through the whoops many many weekends without failure.

Even if the Minibajas were 20 horse twin cylinders they should not be tearing the trannies out.

Maybe they need better judges to recognize failure due to poor design?

There is no way I can see they can load a tranny like I do while riding. I beat mine pretty good. No failures (knock on wood)

Airwolf
08-28-2009, 03:48 PM
The problem may be the chain input- Polaris tranies are designed for the much lower shock load CVT clutches. I have a modified sportman tranny that is reliable with 100+ two stroke HP,
Running CVTs- It has been upgraded with better bearings and input shaft however.

Airwolf
08-28-2009, 03:50 PM
I agree with nutz4sand, in these parts truck tired ATV's with NOS regularly are hammered through root filled trails/boggs untill something breaks. ... that is to say ridden VERY HARD and I have yet to see a tranny break.

nutz4sand
08-28-2009, 03:51 PM
I can see a chain input being harsher but what kind of power are the Minis running? I have never seen a large engine in one.

TBD
08-30-2009, 12:30 PM
Being a current SAE Mini Baja member from CSULB. Our car is running a CVT to double reduction box without neutral or reverse. It seems that in these competitions are particulary tough on gearboxes. We are in process of modifing the internals of the gearbox to withstand the our calculated load. My recommendation is to look at what the top ten teams use and base your decision upon the knowledge your team already knows and has expierence with. Think TOUGH not HARD.
2009 Baja Midwest
10th - Acceleration
15th - Suspension Traction
Endurance - Broken input shaft