Differential

[DKNguyen]

For the bruiser axles from RC4WD (or any shaft driven axle housing for that matter), is it possible to get a differential for it instead of the spool? I was thinking maybe I could add something in to lock the differential when needed. It would probably be something simple (external to the differential) like having disc brakes or some break on each wheel so the free spinning wheel could be stopped so torque would be transferred to the grounded wheel- that is how differentials work right?

[nik77356]

no thats not how diffs work they dont use brakes at each wheel. they use gears or balls to transfer power to the wheel without traction

[K_B]

If I'm not mistaken, the original design did not use diffs so I don't think there's anything in production as far as a diff goes, nor would there be enough room in the RC4WD housing to accomodate one.

[DKNguyen]

Originally Posted by nik77356

no thats not how diffs work they dont use brakes at each wheel. they use gears or balls to transfer power to the wheel without traction

I meant as a way to switch between locked and open diffs- rather than having a controllable lock inside the axle housing. I was asking if I had the operation of diffs right- if one wheel is free spinning and you lock it, all torque gets transferred to the other wheel.

[Robb]

Originally Posted by DKNguyen

I meant as a way to switch between locked and open diffs- rather than having a controllable lock inside the axle housing. I was asking if I had the operation of diffs right- if one wheel is free spinning and you lock it, all torque gets transferred to the other wheel.

Let's start at the beginning. The center internal "pumpkin" of an axle is called a differential. All shaft driven RC trucks will have a differential, seeing as they have "traditional" style axles.

In an open differential, drivetrain traction will be sent to the wheel with the least resistance. A perfect example would be having one tire on the ground, and the other tire off the ground. The tire off the ground would get all the "drive" and spin like crazy, while the other tire sits still.

A "posi-trac" or "limited slip" differential can work like an open diff, but it really takes completely stopping one wheel before all of the drive is sent to the other wheel. Using the "one tire on, one tire off" example, the diff would "slip" a little, and still send some drive to the tire on the ground, but not most of the drivetrain power. Unless completely stopped, the tire on the ground would get some drive torque.

A locked differential sends the same amount of power to both tires, no matter what scenario. Both wheels/tires have the same potential.


Your original question tends to point towards whether or not a switchable locker exists in RC. In the 1:1 world, devices like ARBs, Elec-Tracs, etc do this (on the fly switching between locked diff and open ((or LS)) diff). As far as I know, nothing exists in the scale RC world. IMO, your best option would be Tamiya High Lift axles which do give the ability to change them from open diff to locked diff, but this is not an "on the fly" ability................at least, not yet.

To go with the "brake one wheel" theory, your best bet would try your hand at a very limited slip setup.

[Mechanicalbob]

I have started a thread awile ago talking about a "lock on the fly" Dff for RC. One of the ideas I had/have is to mdify a X-Ray Multi-Diff T1FK 05. It has 3 diff settings, one-way / one-way solid / full-time solid axle.

[DKNguyen]

So one-way is like a one-way open diff? What is one-way solid and full-time solid? (Is one locked-one way and the other locked two-way?)

[Thorsteenster]

wedico makes an axle that has a cable operated locker, both german and expensive.
your brake on each wheel would be a good idea for a tracked vehicle.