What motor?

[Sneeck]

I've just bought a 9920 and 9l from serum but he said that a 9xl would work better in a full alum center diffed maxx. I want to run on 16 cell's for longer run time.

Can I use this motor or should I really swap it with a 9xl?

[Dafni]

Do the maths! What center diff setup do you run? Calculate the reduction, leave room for 2 teeth more and less on the pinion, take your voltage and desired (realistic) speed, and choose the correct KV rating on the motor!

Some center diff setups give you less reduction, so a low KV would be better.
An 8th scale buggs setup with Maxx tires (and Maxx diffs) would require something like a 14XL (or 1950/12 for example)

Just do the maths!

[squeeforever]

not sure bout what kind of speeds you want but i went with a 10xl for my Evo on 16 cells. Oops, ive said to much....:010: :010:

[Sneeck]

Wow not so fast lol. I'm using a 8 spyder diff.

The 9l will give 52435 rpm on 19,2 volt's.

The 9xl will give 35577 rpm on 19,2 volt's.

As far as gearing goes, I have no idea what would be good for this truck. If I did not know this, I wouldn't ask the question.

Why would you need a 14xl for a center diff?

[Sneeck]

My goal is runtime over speed. 35 mph would be good enough if I can drive like 15 minute's.

[Dafni]

Originally Posted by Sneeck

Why would you need a 14xl for a center diff?

See, it's all in the reduction. An EMaxx tranny setup gives you a final gear ratio of 1:20ish, and if you use a buggy center diff, you'll get something like 1:10ish. (thus needing a "slower" motor)

Of course it depends on what center diff setup you want to use. If you incorporate a diff into a maxx tranny, the numbers will be different than a buggy diff. When in doubt, just count the teeth :)

If you need help, just give us the FGR.

35mph is a realistic speed for 16 cells.

[Sneeck]

But you don't need a slower motor if the gearing is lower or higher, you can gear it lower or higher. Atleast that's how I see it.

Will the 14xl give me more runtime than the 9xl on 16 cell's?

The 14xl has 1191 rpm per volt's. So that would be 22867 on 19,2 volt's.

[Dafni]

Of course you can gear higher or lower, that's why I said leave room for 2 teeth more or less in your calculation.
If you run a buggy center diff with a high KV motor....good luck finding a 5t pinion. See what I mean?

[Sneeck]

Yes I understand that. It would be around 51/ 11 with the centerdiff. Right now it's 72/17 on a maxx tranny.

So how about run time's?

[Dafni]

Okay, so you will have a buggy diff with an ofna spur in the center, and 13/43 front/rear diffs, correct?? (the spyders have no influence on reduction, btw)
On such a setup you will have to get a slow motor, otherwise you'll end up with a too small (non-existent) pinion.
These setups work with faster motors, but only on small buggy wheels.

You might consider the truggy diffs from hotbodies, though. They offer more reduction.

You will have a decent run time, no doubt. Right now I can't say more. I have a similar setup here (revo, with ofna diff center, and stock diff f&r) but still have to wait for the shafts. I will let you know how it turns out.

[Sneeck]

Allright 14xl it will be. What kind of pinion would I need?

Thank's for the info. I got a little project myself going on too, the center diff gave it away sorta. But it will be cool.