How deep - brake rivets?

[Robert Lees]

Re: How deep - brake rivets?

liquefied the bearing grease

With the distance between the brake faces and bearings, and the amount of metal (acting as a heat-sink) and air (acting as an insulator) inbetween, I would question such an assumption.

Is it possible that some other cause has created this effect? E.g improper grease spec.; high ambient temperature; emulsification caused by washing/rain, etc?

The reason I ask is that of the four BC12D's with Shinn brakes that I fly from my home field, none of them have had brakes that get worse that "warm to the touch", even after reasonably agressive braking following circuits & then a long taxy back.

Me & my flying buddy serviced the bearings of the wheels in the photo above; it was all as good as the day in June 2004 that we put them back together, 250 hours ago.

Thoughts?

[VictorBravo]

Re: How deep - brake rivets?

An IA (and Taylorcraft L-2 owner) told me that he was somewhat sure the grease had liquefied. The culprit, supposedly, was improper grease, or low temp grease, instead of high temp grease.

I had one...episode... of rather heavy braking but it was only one aborted takeoff. A ground observer stated that he saw smoke coming out from the wheels. After that episode, the airplane had about 1/3 brake on one side and almost nothing on the other.

I took the wheels off and found exactly what the IA told me I would find. Slimy slippery brake shoes. He told me to solvent clean them thoroughly, and wear out at least three clean rags on each side. I did so, put them back together, and after adjustment they were back to normal, above average in this case.

It was after that taxi text that he said to lift up on the struts to allow the bungees to pull the gear in, and that's when we heard the clunking noise, and that's when the wings had to come off. And that's another story that I have recounted elsewhere

[hangarb7]

Re: How deep - brake rivets?

But if you use the high temp epoxys, how do you eventually get the old linings off when time for a change?

Jack Dernorsek
N44057

[VictorBravo]

Re: How deep - brake rivets?

That would have been my second question! I don't know how Rob does it. I do know that epoxy usually doesn't want to stick to aluminum. You'd have to roughen the surface to have any chance at all. I SUSPECT that you would have to chisel them off, or have the wheel put in a lathe and actually machine off the old linings and epoxy. But I have no experience, Rob is the one to say how to get them off.

[M Towsley]

Re: How deep - brake rivets?

You utilize heat from a heat gun to soften the epoxy, then acetone to clean up the residue. Don't ask how I know........ Plus it is based upon the recommendation of the epoxy manufacturer. Also, the area where the lining would be adhered, (hypothetically), appears to be magnesium on my spare wheels.

[Robert Lees]

Re: How deep - brake rivets?

Who's using high temp epoxies? Not me!

You tell me how many hours you do per annum; how many years you intend to fly; divide the years by a typical annual reduction in lining thickness per annum (based on hours per annum usage); THEN I'll tell you how to remove the bonded linings.

If you get there before me, then I will lead you to a lathe and/or a hot air gun and a scraper. But I dare you to get there sooner!

[edit: Doh! Marty got there before me!]

[Jim Baker]

Re: How deep - brake rivets?

Personally (no offense to those who do) I would not even consider using glue to secure my linings. The rivets work great. I’m not sure, but as your linings wear, you may get to a point where you can not adjust the brakes anymore not because you are out of lining, but you may have exceeded the expansion limits of the brake shoes. When you have your wheels off, the rivets are a good indicator that you may soon need new linings.

Also, at some point, you’ll have to replace the “new” linings you are now putting in. I hate to think about how difficult it might be to remove them from the wheel if they were glued in. Recently, I replaced my linings as per the BC12D service manual. The job is quite simple and it calls for countersinking the linings to a 3/32 depth.

New brakes, should last years. You should be using little or no brakes under normal conditions. Use brakes to tighten your turns by breaking your tailwheel over. Plan your taxi speed appropriately for the conditions – and remember to make sure and pull the power to idle before applying the brakes (sorry that’s the instructor in me talking).

[Forrest Barber]

Re: How deep - brake rivets?

Service Manual??? WHAT a clever idea , does that mean you try to conform to Type Certificate or do you just try any wild haired idea that pops up on the internet. By the way i agree that rivets, no epoxy is the way to go for many reasons.....bye Forrest