So you know how pusher brake work? Did your new brake tool help?

Are ya having a problem with your rig? We'll try to help. Share your tech tips and experiences here. Dr. Billy Glaser, author of the "Unofficial 750 Ural Service Manual" site myural.com, is moderating this section.
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gobium
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So you know how pusher brake work? Did your new brake tool help?

Postby gobium » Wed May 03, 2017 11:10 am

Ural science, x ray vision
Do you understand the 2 cam piviots?
I dont know the answer just asking the question
1493823804-picsay.jpg
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Last edited by gobium on Wed May 03, 2017 11:25 am, edited 2 times in total.

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Re: So you know how pusher brake work? Did your new brake tool help?

Postby Albuquralque » Wed May 03, 2017 11:14 am

:lurker:
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Re: So you know how pusher brake work? Did your new brake tool help?

Postby Manscout » Wed May 03, 2017 12:24 pm

I want to know!
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Re: So you know how pusher brake work? Did your new brake tool help?

Postby scottolds » Wed May 03, 2017 12:32 pm

Is this what you are investigating?

How the shoes contact the drum?

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Re: So you know how pusher brake work? Did your new brake tool help?

Postby Lmo » Wed May 03, 2017 1:08 pm

I'm all eyes Mr. G. Even using your Mi-Pei tool I'm still trying to figure out this mystery (front and back). The drum being out-of-round isn't helping...

Cutting a backing plate for an "exploded" view . . totalement brillant !
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Re: So you know how pusher brake work? Did your new brake tool help?

Postby TerryG » Wed May 03, 2017 1:12 pm

Looks like just an attempt to provide cooling to the brake. The cam pivots are on the backing plate, not the drum. I would go with holes drilled in the backing plate - not weakening the wheel with cutouts.
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Re: So you know how pusher brake work? Did your new brake tool help?

Postby gobium » Wed May 03, 2017 1:14 pm

So?
Just asking, on 2wd or may be 1wd.
With shoe (leading or trailing) moves first or both move at same time? When finger the lever lightly

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Re: So you know how pusher brake work? Did your new brake tool help?

Postby Lmo » Wed May 03, 2017 1:24 pm

On back, they should be moving at the same time since there is only one brake cam.

On the front brake they should also be moving at same time, allowing for any slop in the connecting link between front and back brake cams. I fitted my front brake with Suncor turnbuckle to remove the slop, so they move simultaneously.

On my BMW R75/5 front brake, one shoe touches first because the internal springs are different of "rates". Not the case for Ural, right?
Lew Morris
Pismo Beach, California, 93449.
1963 (?) Dnural w/ '06 Ural Drive Train
C5 Power Arc
125/42 jets
Drilled slides/
.030" shims

1973 BMW R75/5 (original owner)
1947 HD FL (long gone, forever regretful)

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Re: So you know how pusher brake work? Did your new brake tool help?

Postby gobium » Wed May 03, 2017 1:26 pm

TerryG wrote:Looks like just an attempt to provide cooling to the brake. The cam pivots are on the backing plate, not the drum. I would go with holes drilled in the backing plate - not weakening the wheel with cutouts.

Terry?
The hub is junk hub. Attempting to see how brakes work.
Got nothing to do with what you said.

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Re: So you know how pusher brake work? Did your new brake tool help?

Postby gobium » Wed May 03, 2017 1:28 pm

Lmo wrote:On back, they should be moving at the same time since there is only one brake cam.

On the front brake they should also be moving at same time, allowing for any slop in the connecting link between front and back brake cams. I fitted my front brake with Suncor turnbuckle to remove the slop, so they move simultaneously.

On my BMW R75/5 front brake, one shoe touches first because the internal springs are different of "rates". Not the case for Ural, right?

Are you assuming ?.or you did the test on ural?

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Re: So you know how pusher brake work? Did your new brake tool help?

Postby Lmo » Wed May 03, 2017 1:57 pm

Not "assuming" based on what I have seen when I have my rear brake apart (Ural not Dnepr). If the cam cross-section is the same (they look like they are) they should move at the same time, and at the same rate. If one side of cam is different movement would be different.

Is this what you see?

On Ural front drum brake they must move together because leading brake cam shaft/arm feed the trailing arm through link. Slop in link would give some difference in movement, how much?

What is hard to visualize (for me) is how to make the brake shoe outside diameter match the brake drum inside diameter when brake is fully applied. The "sand paper" lathe tricks works to certain extent.
Lew Morris
Pismo Beach, California, 93449.
1963 (?) Dnural w/ '06 Ural Drive Train
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.030" shims

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Re: So you know how pusher brake work? Did your new brake tool help?

Postby URAL CT » Wed May 03, 2017 6:39 pm

Here's my thinking: when the cam engages (ya step on the foot brake) the bottom part of the brake shoe touches the hub first, then the top section engages the hub. Opens like a clam shell, It's pivoting from the bottom shoe where the cam is. The movement is very slight, if properly adjusted. The brake springs keep the shoes in place.
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Re: So you know how pusher brake work? Did your new brake tool help?

Postby gobium » Wed May 03, 2017 7:05 pm

Sidecar wheel
Lever is on top vs. Pusher wheel

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Re: So you know how pusher brake work? Did your new brake tool help?

Postby Snakeoil » Wed May 03, 2017 7:14 pm

I agree with everything you said Lew. To answer your question, in order to get full contact with either a TLS or SLS brake, you need to arc the shoes to match the drum. I've never done it, but can envision how to do it. And my friend Dave supposedly has an arching machined buried somewhere in his shop that he said I could have, if he ever gets around to finding it.

Mike Morris will do this for you. Not cheap. I talked to him about it a year or so ago.

Here is how I believe it is done. You set the shoes up on the backing plate with pads that are oversized. You put them on the machine and it grinds the pads to a diameter that you determine. I suspect that you put something like a 0.010 or 0.020 shim between the cam and the shoe and grind them to the exact diameter of the drum. You then remove the shim(s) and the shoes are sized and arched to fit the drums and be round when the cam expands them. The shims allow you to size and arc the shoes with the cam in the rest position while emulating the shoes being expanded.

Whether it is TLS or SLS should not matter. What will matter is how the shoes look on the plate. The SLS shoes will be fatter by the single pivot point. The TSL shoes will also be fatter at the pivot points, but those points will be 180 deg from each other.
I need to go bug Davy again. Maybe he will let me look for the machine. He's a pack rat so he might not want someone poking thru his stuff.

Here is an exaggerated sketch to show what I think they would look like after aching and the shims removed.

Shoe Arching.jpg
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Rob
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Re: So you know how pusher brake work? Did your new brake tool help?

Postby Snakeoil » Wed May 03, 2017 7:23 pm

URAL CT wrote:Here's my thinking: when the cam engages (ya step on the foot brake) the bottom part of the brake shoe touches the hub first, then the top section engages the hub. Opens like a clam shell, It's pivoting from the bottom shoe where the cam is. The movement is very slight, if properly adjusted. The brake springs keep the shoes in place.


This could just be semantics, but I thought I'd try to clarify. The shoe sits on a pivot on one end and a cam on the other. It pivots at the pivot end. It moves outward at the cam end. If the shoe is shaped to match the drum when mounted to the backing plate, then it really should touch all at the same time.

If it worked at you described, touching at the pivot end first, in order to continue to make contact, you would have to bend the shoe. This is why there is no material close to the pivot point. The closer you get to the pivot point the less the shoe moves.

The curvature of the mating pieces is what makes this hard to envision. But if you use two straight piece, it becomes very clear. Take two straight pieces of wood and put a hinge between them so they fold together. Now open and close them. They make no contact until you have 100% contact. The ends near the hinge moves very little and the opposite ends move a lot. One piece of wood is the drum and the other is the shoe. You want to grind the shoes on the backing plate so that they act like the two straight pieces of wood. Your goal is to achieve 100% contact. Look at your shoes, they friction material will be thicker at the pivot end than the cam end. Not a lot, but there should be a difference.
Regards,
Rob
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