H: Hubs, Wheels and Tyres Drum Brake and Shoe Tuning - Race Tech

[Cyborg]

it yust fits using the bearing of the wheel, note the lack of Rubber arround the drumView attachment 16317

Vincent,
What speed is the lathe turning? I did a drum yesterday and was getting too much chatter.
What type of insert are you using?
When I set the rear hub up on the lathe between centres, the runout on the drum was in excess of .012” which maybe doesn’t sound like a lot, but it looked horrible… like I would need a bigger damper on the RFM and stabilizers for my eyeballs.
I ended up using a small tool post grinder instead of a boring bar. The axle, bearings, hub, and drum were all new, so it seems a little surprising. The shoulders on the hub (where the spoke flange and drum sit) were different sizes end to end. Different tolerances everywhere.

 

[Vincent Brake]

When I get some parts in, its always in need of some skimming, nothing is realy up to say the normal task.
It may be that tollerances are Ok, but then where are they placed Geometrical....
Run-out, out of square, paralell, etc to name a few.

As far a skiming a hub assembly, I use a rubber inner tube tightly fixed arround the outer finnend drum, to avoid chatter.
As an insert I use CBN 0.4 tip radius T shape. At 150-200 M/min. 0.05-7mm feed.
Cbn, alltough -20 degree swarf angle, its extreemly sharp, Hard and thus light cutting, over an Hard type of tungsten, whom is getting bluntish as you enter Cast material.

But your solution may be easyer to set up, but not any grinder has good eniugh bearings

 

[Peter Holmes]

I leave my brake drums intentionally eccentric, they are an affordable ABS, just pull the brake lever on as hard as you can and let the stop start, stop start do it’s stuff.
Only kidding Vincent, don’t have a heart attack!

 

[Michael Vane-Hunt]

When we turned brake drums there was a coil spring that was tightly wrapped around the drum to help prevent chatter. Some older cars had a coil spring around the brake drum on the front drums maybe for the same purpose.

 

[vibrac]

Without thinking to deeply it would seem from the picture from #1 that it would not be beyond many of us to create a tool that rotates on the main spindle and could clean up the drum
not many of us could turn a wheel and a drum on its own is a wast of time
Certainly to measure the eccentricity from the spindle would be easy and you might find the machining is not necessary
fortunately you can set the taper bearings to zero clearance

 

[Monkeypants]

There is a way to do this without a 27" swing lathe or any lathe. It doesn't require the tire removal either, however a bit of patience is needed.
Invariably, when I describe the method, someone who has not tried it tells me in no uncertain terms that it cannot possibly work!

Glen

 

[Cyborg]

When I get some parts in, its always in need of some skimming, nothing is realy up to say the normal task.
It may be that tollerances are Ok, but then where are they placed Geometrical....
Run-out, out of square, paralell, etc to name a few.

As far a skiming a hub assembly, I use a rubber inner tube tightly fixed arround the outer finnend drum, to avoid chatter.
As an insert I use CBN 0.4 tip radius T shape. At 150-200 M/min. 0.05-7mm feed.
Cbn, alltough -20 degree swarf angle, its extreemly sharp, Hard and thus light cutting, over an Hard type of tungsten, whom is getting bluntish as you enter Cast material.

But your solution may be easyer to set up, but not any grinder has good eniugh bearings

Thanks for the info.
Yesterday, after I wrote that, I assembled the front hub and drums. It was a lengthy process matching everything up. The OD of the boss where the spoke flange and drum sit on the hub was different end to end. All parts were new, so nothing matched. By farting around, scraping, deburring, removing paint, reaming and select fitting, the runout after final assembly was about 0.0762mm, so much better than the rear drum.
I turned one side with the tool post grinder and got the runout to within 0.0762mm (.003”). I turned the other drum with a boring bar. This time I lowered the speed and feed. Finish was good with no chatter, but still couldn’t do better than 0.0762mm . Maybe with a larger boring bar it might clean up, but I’m calling it good enough.
I’m not sure what you mean by the bearings in the grinder not being good enough. I’m probably asking for trouble using the small grinder because it is not rigid enough and the stone is basically following the remaining runout?
After going through this process (especially with the rear hub/drum), I would never assemble one without turning the drums prior to lacing the rim.
Like you mentioned previously, we are buying 90% of the part.

 

[Cyborg]

There is a way to do this without a 27" swing lathe or any lathe. It doesn't require the tire removal either, however a bit of patience is needed.
Invariably, when I describe the method, someone who has not tried it tells me in no uncertain terms that it cannot possibly work!

Glen

Well I did think of you and your method while watching the chatter marks appear.

 

[Monkeypants]

To be fair, a small lathe would be needed if new linings have been fitted. This would just be used to get the brake plate with the newly lined shoes into the drum with a minimal clearance to start.
I used the Emery method to cure severe pulsation and to obtain very strong brakes.

Glen

 

[Cyborg]

That is today’s job. New shoes and no asbestos! What size shim do you put between the cam and shoe when turning?

Couldn’t you swing a 27” wheel assembly in that behemoth of a mill if you wanted to?