Transmission Layout for Brushless
 

Hey guys,

Just a few elementary questions about transmissions. I know that for brushless, with such high torque and RPMs, that the 2 speed transmission is not that important, but I would like to pursue it anyways.

Two Questions:

What is the point of the "idler" gear in the old and new emaxx (or bl revo) transmissions? It seems like the idler gears can simply be eliminated.

What is the name for the type of two speed transmissions that utilize the two-gear pinion gear and the two spur pinion gear? You know, like the one you would see on an LST2 or something. What are the pros and cons of this type of transmission as opposed to the "shift on the fly" type used by the emaxx/revo?

Thanks

Idler gear was simply to reverse the direction of rotation when using brushed motors; I've seen a custom made tranny around here & the guy did away with the idler altogether- looked rather nice really.

No specific name for the 2-speed spurs and pinions, they are just specific to nitro models & have a clutch mechanism inside that activates at high rpms to lock the 2nd smaller gear of the spur-cluster to the input shaft.

Pros:
no chance of mis-aligned gears or shifting components when trying to shift at speed.
Adjustable shift point to make the most of the motors/ engine's power band/ curve.

Cons:
manual shifting is impossible.
More parts to maintain.
No reverse generally.
Have to use mechanical brakes.

I would really question what it is you are trying to achieve and what your goals are, or even what vehicle you are contemplating buying/ converting?

If you use a BL system you dont need a 2spd kit to give you more torque at low rpms, only if you had a really heavy truck, or were building a crawler-come-basher that needed low speed & higher speeds that were selectable as required/ desired ( see: BL traxxas summits @ the traxxas forum ).

Thanks for the response.

Not quite sure yet about what the project will be. I have the electronics minus a motor, now I just need a good platform. I'll buy the motor once I have an idea of weight. I plan on making my own chassis+bulkhead and then using the suspension of an 808 or something. I designed bulkheads and a chassis once before and it was simply ok, but I will take my time with the design of this one. As you were saying, this will probably be a heavy project and may need a two speed.

the simplest set up is just running a center diff set up just like the 1/8 scale trucks/buggies do

Its true. If you don't like the Center Diff action, there are lots of ways to lock it.

I have done the transmission scene before. Center diff set up is much easier all the way around