Gearing

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RcJunkie13 said:
Hey guys, I have a 36cc rovan baja, last run i put on the e-clip wrong and spur gear parts went missing, just wanted to know if alternative gearing would be better, right now it is 17/57.

Thanks
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I have the same Rovan as you and i'm realizing that in loose conditions the stock gearing is a bit low (meaning a lot of excessive tire spin and tricky to drive). The 36cc engine in top tune is a real screamer and the crappy handling can be difficult to keep the truck tracking straight. Come next season, i'm going to experiment with slightly higher gearing as Z.hb71 suggested. Higher gearing will "in theory" add some top speed (but realistically you won't see any speed gains). What should happen is the slight loss in bottom end torque will lessen the unwanted excessive wheelspin. Gearing is a compromise of either quick off the line acceleration or higher top speeds based upon your preference, (but you can't have both). Keep in mind that Rovan uses a oddball clutchbell pinion drive gear, and HPI Baja pinion gears will NOT interchange. Don't ask me how I found this out.
 
Polar_Bus said:
I have the same Rovan as you and i'm realizing that in loose conditions the stock gearing is a bit low (meaning a lot of excessive tire spin and tricky to drive). The 36cc engine in top tune is a real screamer and the crappy handling can be difficult to keep the truck tracking straight. Come next season, i'm going to experiment with slightly higher gearing as Z.hb71 suggested. Higher gearing will "in theory" add some top speed (but realistically you won't see any speed gains). What should happen is the slight loss in bottom end torque will lessen the unwanted excessive wheelspin. Gearing is a compromise of either quick off the line acceleration or higher top speeds based upon your preference, (but you can't have both). Keep in mind that Rovan uses a oddball clutchbell pinion drive gear, and HPI Baja pinion gears will NOT interchange. Don't ask me how I found this out.
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That weird clutch bell, I assume your talking about a hex style . In which case you will have to buy those from vertigo, they have 17t, 18t 19t, and 20 I believe. As that clutch bell is a rip off vertigo part. I will have to say, you are very wrong about the "you won't see any speed gains" from a gear change. I changed from 19/55 to 18/56 and it was a big difference.
dougstar said:
other thing you can do to stop the wheels losing total traction is a lower rate clutch spring?? like a 6k the clutch would be less spooled up on pull off??= less spinning
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+1 ?
 
Z.hb71 said:
I will have to say, you are very wrong about the "you won't see any speed gains" from a gear change. I changed from 19/55 to 18/56 and it was a big difference.

+1 ?
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So if you saw an increase in top speed with a gear change going from 19/55 to 18/56 this tells me your truck was "over geared" and you did not have enough engine hp to pull the 19/55 gearing. You lowered your gear ratio and gained speed (which was obviously a good call). Gearing 101 theory: Larger tooth drive pinion = higher top speed but less acceleration. Smaller drive pinion = quicker acceleration less top speed. Everything previously stated is reversed when swapping spur driven gears. To come up with a final drive ratio you divide the spur gear by the pinion gear so 19/55 = 2.89 final drive ratio and 18/56 = 3.11 ratio. The higher the final drive ratio (3.11) the better the acceleration but less top speed, the lower the ratio (2.89) the more potential top speed, and slower acceleration but again only achieving said top speeds if you have enough hp to pull the higher speed gears. If you already know all this sorry for the long winded reply.
 
Polar_Bus said:
So if you saw an increase in top speed with a gear change going from 19/55 to 18/56 this tells me your truck was "over geared" and you did not have enough engine hp to pull the 19/55 gearing. You lowered your gear ratio and gained speed (which was obviously a good call). Gearing 101 theory: Larger tooth drive pinion = higher top speed but less acceleration. Smaller drive pinion = quicker acceleration less top speed. Everything previously stated is reversed when swapping spur driven gears. To come up with a final drive ratio you divide the spur gear by the pinion gear so 19/55 = 2.89 final drive ratio and 18/56 = 3.11 ratio. The higher the final drive ratio the better the acceleration , the lower the ratio the more potential top speed, but again only achieving said top speeds if you have enough hp to pull the higher speed gears. If you already know all this sorry for the long winded reply.
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I don't believe it was over geared. Bottom end didn't feel lacking at all, and it reached top speed pretty quickly. 18/56 feels slightly short but livable. As I don't have such a big spot to open It up anymore.
Have got 7.5hp after all ?
 
Z.hb71 said:
18/56 feels slightly short but livable. As I don't have such a big spot to open It up anymore.
Have got 7.5hp after all ?
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Gearing is all about matching your hp to your conditions and your goal. Some love rip azz acceleration , some want nothing but top speed. Tinker with gearing and document your data from standing acceleration runs to top speed data. This way you know for sure what gearing changes work, and what gearing does not work for your goal.
 
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