2wd gearing & slipper question.

butters86 · #1 23-07-2014

Hi All,
I've just swapped my brushed 12/4 motor and LRP speedo for a Turnigy 9.5T Sensored Brushless & Hobbyking 120A speedo.

It seems ridiculously quick at accelerating but has topped out by the end of a 10m long garden. After a 10 mins+ run on grass the batteries where cool as was the motor.

I can't help but think I could get more speed but not sacrifice much acceleration by changing the gearing.

I currently have an Ansmann Madrat. I've upgraded the 28T gear in the gearbox for a metal one from a HPI Firestorm so in theory the gearbox can take more abuse. The Spur gear is the stock which I believe is 80T? The differential gear is also stock 52T I think. The pinion I have fitted is an 18T HPI one.

So what would people recommend going to on the pinion? I think it has 21T stock but it was making my old brushed setup work too hard.

Also what is best practice/ what is the purpose of the slipper setup on the spur gear? At the moment it's just about fully tightened.

Ashlandchris · #2 23-07-2014

Right, pinion wise you would be ok 22 or 23. You could drop main spur to 78 quite comfortably, but one note of caution. I was advised by a former team c distributor to avoid the alloy gear as it destroys the other plastic ones. Team c do a kevlar 28t replacement which I'm told is ok. I still have standard plastic in my gearbox, with 78 spur and 22 pinion on a 10turn sensor less leopard motor and it us superb

butters86 · #3 23-07-2014

ok, I'll order 22 / 78 like you have an give it a go.
regarding the gearbox, I'll have to inspect it for wear then shortly and see how it's coping / possibly swap to the kevlar one. Is it also worth getting a team c kevlar spur?

somebody else recommended the alloy 28t gear as they where stripping plastic ones and had been OK since but if it wears out the other plastic ones then It's a false economy isn't it.

Ashlandchris · #4 23-07-2014

In fairness, I was advised against the team c alloy 28t gear, while you are using a HPI one so it may be better. I was told the mesh wasn't quite right on the team c one hence the wear rate.

Just one note of caution, on a mad rat, with it being rear motor, if you try for "too quick" you will spend your life wheelie-ing and have no steering

butters86 · #5 23-07-2014

You're right, I don't want to be wheelie-ing on the track. I think my clarkson "speed, power, more" is more for when I go for the bi-weekly visit to my parent's house which has a nice long garden

Dandare · #6 23-07-2014

A 24t pinion should be ok, I've also used a 27t. It does depend where (what type of track?) you're racing on. You can overheat a motor by maxing the rpm on long straights if under geared, likewise you can do the same by over gearing it on tighter track, it's a tricky one to figure out sometimes.

Regarding the slipper, I first set the diff tight enough so when you hold/lock one back wheel plus the spur gear you can almost not turn the other wheel, this is done with the slipper fully tightened. Then, for a base set up switch the car on, put it on the bench/ground, hold on to both back wheels & apply a constant steady throttle, you want the slipper set loose enough so the front wheels remain off the ground by 2-3"

As a note, you always want the slipper to slip before the diff does, or else you'll soon knacker the diff plates etc.

If you're using it on loose ground eg. dirt then you may want to loosen it further so you don't keep spinning out, on a higher grip surface eg. astro you'll tighten it slightly & maybe even add some weight on top of the servo.