Serpent S411 Sport build

[Newracer]

Hey guys. I'm slowly putting togethere an electric touring car for the 17.5T class, I'm using a HiTec HS-5565MH servo. Anybody which servo horn I use? 23T/24T/25T? And for the pinion? It's an 84T spur. I'm basically a newbie when it come to skill level.

Thank you very much for the help

[lomar15]

24 spline for the servo or it may also be marked HT

[Newracer]

Hey guys. I'm trying to figure out what tooth count pinion I'll need, the spur gear is an 84 tooth 48P and I'll be running a 17.5T motor.

Thanks,
Clay

[haddow]

It depends on your internal gear ratio. I think I am running a final drive ratio of 4.2-3.8 so with my 96 spur I am somewhere between 44-49 pinion (considering the internal ratio of my XRay). But i dont race electric much so I am not an expert.....

[Blake]

It looks like the Serpent S411 internal gear ratio is 2.0 based on a quick online search.

You will want an overall final drive ratio (FDR) of 4.2 to start with a 17.5 motor (this will change with a 21.5)

Basic formula:
FDR = (Spur / Pinion) * Internal Gear Ratio

Rearranged to find pinion:
Pinion = (Spur * Internal Gear Ratio) / FDR

Pinion = (84 * 2.0) / 4.2

Pinion = 40


So a 40 tooth pinion should be a good starting point.


I hope that helps,
Blake