How would you approach setting up brakes on a kart with a differential?

[kartnoob101]

I'm picking up a project kart this weekend with a rear differential. (Expect plenty more questions from me in the future, lol...)

It currently has brake bands that have seized up, so I'm looking at redoing the whole brake system. I'm wondering about the viability of dual disc brakes, both in terms of cost and syncing them up so that both wheels receive the same braking force. What type of system would you guys go for, keeping cost in mind?

 

[mckutzy]

Can't say much, need some pics as to the kart in question.
Discs need a hub and if its a diff rear, it all depends on the shafts diameter.

 

[kartnoob101]

I figured pictures might be necessary, I won't be able to get good ones until this weekend so it looks like I was a bit early in creating the thread... Thanks though, I'll get pics up as soon as I can

 

[Denny]

With out pictures I would sneak up on it carefully and cautiously. That's how I would approach it.

Denny

 

[landuse]

You need to have the brake set up that it stops the differential. The brake disc will have to be bolted to the diff, otherwise you will just be stopping the one wheel

 

[mckutzy]

I meant to say in my last post, you will need discs on both wheels.

 

[landuse]

I meant to say in my last post, you will need discs on both wheels.

Not necessary. You just need to stop the diff

 

[mckutzy]

I would have thought it much like a car or the like. Discs on left/right.

 

[kartnoob101]

I would have thought it much like a car or the like. Discs on left/right.

That's what I was originally thinking, hence mentioning "dual discs" in my original post. However, I feel like it would be difficult to sync them up and have them both provide the same amount of braking force to their respective wheels. Putting a brake on the input shaft of the diff, if possible, might be easier.

 

[mckutzy]

Any standard hydraulic setup will have them balanced automatically.
A mechanical setup will need more work to have them balanced, weather with cable or rod actuation.

 

[machinist@large]

Not necessary. You just need to stop the diff

:toetap05: :toetap05: Actually, Paul, when you have a differential, dual brakes aren't optional, they're mandatory. Just stopping the diff housing from turning is almost as bad as no brakes at all.

The spider gears in the diff compensate for difference's in speed between the wheels while in motion. The trouble starts when you stop the housing from rotating; now those same gears allow the wheel with the most traction to continue to move forward while now forcing the one with the least traction to spin at the same speed, only its in the OPPOSITE DIRECTION!!!

That's usually considered to be a really bad thing when you really, really, need to stop right now.......

 

[ML-TOYS]

Even on my trisport with the diff it originally came with dual band brakes but i am doing with dual hydraulic.

 

[itsid]

:toetap05: :toetap05: Actually, Paul, when you have a differential, dual brakes aren't optional, they're mandatory. Just stopping the diff housing from turning is almost as bad as no brakes at all.

The spider gears in the diff compensate for difference's in speed between the wheels while in motion. The trouble starts when you stop the housing from rotating; now those same gears allow the wheel with the most traction to continue to move forward while now forcing the one with the least traction to spin at the same speed, only its in the OPPOSITE DIRECTION!!!

That's usually considered to be a really bad thing when you really, really, need to stop right now.......

while I agree on "two discs are much better than one"
it's fairly common to only stop the diff on karts..

(IIRC the Muskin Dune cat for example)

And while it'd be exactly as you say if one wheel has no traction whilst braking (it'd stop the diff but not the kart)
you'll have to try really hard to achieve just that situation with "our general fun karts"
for any extended period of time longer than a split second..

I can't even imagine a curve tight and long enough to lift the inner wheel without tipping the kart;
since as soon as the second wheel regains traction it'd be stopping the kart

icy roads is the only thing I can think of...
and frankly, when, who and WHY!?

'sid

 

[machinist@large]

while I agree on "two discs are much better than one"
it's fairly common to only stop the diff on karts..

(IIRC the Muskin Dune cat for example)

And while it'd be exactly as you say if one wheel has no traction whilst braking (it'd stop the diff but not the kart)
you'll have to try really hard to achieve just that situation with "our general fun karts"
for any extended period of time longer than a split second..

I can't even imagine a curve tight and long enough to lift the inner wheel without tipping the kart;
since as soon as the second wheel regains traction it'd be stopping the kart

icy roads is the only thing I can think of...
and frankly, when, who and WHY!?

'sid

Alex, in a perfect world your argument would be spot on; let me add some data for you.

I live in the State of Michigan. And while the number of roads that are listed as "improved" (i.e. graveled once or twice a decade) has grown over the last 3 to 4 decade's, the number of truly paved road's pretty much hasn't.

Then there is the love of off road play time; a kart with only one brake acting only on the housing of diff will get someone killed at Silver Lake State Park, let alone them trying to play in the mud in someone's wood lot.

I've also lived thru the scare myself; when I was 12, the primary brakes on the tractor I was driving from home lost hydraulic pressure and failed. I reached down and pulled the parking brake up as hard as I could.

I remember the indecent; I remembered the RH rear tire spinning furiously in the grass and gravel on the shoulder of the road while the LH one continued on like nothing was wrong.

The parking brake on that tractor operates on the diff housing: since I'm now 46, I called my father, who was following my in one of the farm trucks to keep me safe as I learned to operate farm machinery to confirm what I remembered was correct.

He today gave me his side of things; I remember being scared out of my mind. Him pulling me off the tractor and stuffing me into the cab of the truck, being driven up to the house and being ordered to get in bed. (One of the punishments my parents used when my brother or I messed up).

About 10/15 minutes later, my great aunt comes in and gets me: my father sent me there to keep me safe while he and my great uncle tried to figure out what happened.

Turns out the drive coupling for the hydraulic pump failed.......

 

[itsid]

Sorry Pat;
I simply cannot wrap my head around how on earth the two wheels can have such different traction, even off road..

Gravel is not a problem; otherwise it would be impossible to accelerate on gravel
(same exact physics with opposite force vectors )

Of course I know how to get stuck in a mud hole... but "at speed" and in a situation where it really matters? Sorry, you lost me there.

In fact any situation where you can accelerate using a diff driven axle is a situation where you can slow down braking the diff housing only;
since that's the exact same thing physically.

Don't get me wrong, two are better than one, and four are better than two.. anytime!
Also I wouldn't doubt your experience, of course.

But for the sake of simplicity I'd still consider a kart with a diff attached single disc as reasonably safe *shrugs*
Or let me put it in another perspective...
I think it'd be more likely for the brake to fail completely (leaking hydraulics, snapped cable) than to get into a traction problem like you described.
Maybe I'm wrong, very possible ... personally I'd take that risk

'sid

[EDIT]
kartnoob, really.. if you have the slightest doubt about a single disc..DON'T!
Get two; it's always the safer alternative, if alone because you double stopping power

 

[kartnoob101]

Well, picked up the kart today and there is no exposed drive shaft, so a single brake on the drive shaft is not an option anyways.

It's got a semi-functional dual band brake system (the rod that connects the two bands is seized up real good), which I will probably fix up and use for the time being because dual disc brakes seem to be a bit of an investment!

 

[mckutzy]

Lets see some pics on this.

 

[kartnoob101]

At work, but here's what I have from the seller's emails.

I'll take better pictures tomorrow

 

[chancer]

I don't see a diff in these photos

 

[kartnoob101]

Yep, it's not visible in any of these, but I know it's there because if you lift up the back and spin one wheel, the other spins backwards

I'll get a picture of it tomorrow