How deep - brake rivets?

[mhorowit]

I'm counterboring my brake linings.
From the top of the head of the rivet, to the surface of the lining, how much depth should I allow?

- Mike

[alwaysoar]

rivet depth

do it the same depth as your old ones--that's what I was told by those in the know.


Ed @BTV VT
\TF 527

[mhorowit]

Well - the old ones were glued in place

- Mike

[Acroeric]

I usually sink them about 1/2 of the lining thickness.

[mhorowit]

Eric - thickness of rivet head = 2/64"; thickness of lining = 8/64"; 1/2 thickness of lining = 4/64", minus thickness of the rivet head leaves 1/32" of usable lining.

How long does that last before the rivet heads hit the shoes? - Mike

[alwaysoar]

rivet depth

Mike,
Rob Lees is the expert here, but I think what he said once is that you want to counterbore down to .050. The thickness is .125 leaving .075 for the head. That's how my old ones were bored and they held up, and that's what I did with my new ones. Not fully time tested.

Ed @BTV VT
TF 527

[Acroeric]

Mike- I was saying that from the top of the rivet head to the surface is 1/2 the total thickness. . . May not be the way everyone else is doing it but it has worked for me on several different occasions.

[Robert Lees]

Not the expert, Ed, thanks for the compliment though. You are also correct in that you must counterBORE, not counterSINK. You are also correct, in that do the same as what was there before...BUT...

...I personally now only bond these linings (on the basis that modern adhesives were of course not available in the "good old days", but if CG knew then what we now know, he would I'm sure have done the same)... (some folk might call this "Progress", but of course, like Carb Ice protection, we cannot install it due to some litigation issues.). My bonded linings are now to all intents and purposes fully time tested, but only up to 65 hp full static rpm (and how much more does one need?).

Anyway, I live in England, so sue me! back to the issue, I would agree with Eric; if relining using rivets, the rivet heads be half the thickness down through the thickness of the lining (does that make the head 1/16 below the surface of a 1/8 lining?)

For the lawyers listening, this means "The Rivet Heads Shall Always Be Below The Surface Of The Lining Material So As Not To Affect The Braking Efficiency"

To prevent cracking around the rivet heads, I am sure that no-one would object to the linings being "bedded down" in a bed of epoxy first.

Incidentally, since Asbestos-free linings are now banned, how many Shinn Brake users have submitted a 337 to use a different material to the original design? Or is the new non-asbestos material FAA approved for all applications?

My full text available at www.Taylorcraft.org.uk/Brake-issues.pdf (250 kb download)

Rob

[alwaysoar]

brake linings

Dear Expert, What would you use for epoxy that can be easily found here in the colonies?

Ed @BTV VT
TF 527

[Robert Lees]

Ed:

I use "Araldite", two-part epoxy in little tubes, I don't know what is available over there.

Rob

[mhorowit]

DREMEL makes an all-metal cutter bit which is 1/2" tall and 5/16" wide, so I drilled my pilot holes, drilled down a bit with my 5/16 bit, then finished off with the Dremel tool. Made just the right hole for the rivet- Mike

[captjon]

You might want to look at the temperature considerations in using epoxy. Some types don't do well under higher temperatures, thus negating your "bedding" attempts.

I know of a lady who aggressively got on her BC12-D brakes and "smoked" them. One can only assume that would raise internal temperatures up to several hundred degrees at least. And yes, she did have to reline her brakes after that...........

[Robert Lees]

I know the situation to which you refer, Jon, and my understanding is that she REALLY used the brakes after a fast arrival.

My experience of epoxy is that up to 60 degrees Celcius (convert to F if necessary) that all epoxies are secure, but in my experience (including some low-houred pilots using my Taylorcraft) is that the epoxy resin system will work just fine.

Paperwork might dictate otherwise!

Rob

[Robert Lees]

Follow-up

Just removed our wheels for annual inspection.
The linings in the photo below are bonded using epoxy (no rivets) and have done over 250 hours, and show about 0.010" of wear. There is no distress to the wheel or the lining itself.

[VictorBravo]

Re: How deep - brake rivets?

I also immediately thought of the heat problem. I had to get on my brakes very hard recently and it liquefied the bearing grease, which fouled the linings.

It is possible to find a higher temp epoxy. Jon Sharp used higher temp epoxy to make several parts for the Nemesis 1 racer forward of the firewall. If memory serves, his actual cylinder cooling shrouds (a larger part of his speed than anyone seemed to understand) were made by crew member Dan Bond from fiberglass and some hi-temp government epoxy.

If a suitable hi-temp epoxy can be found and tested, it would be a great service to the Taylorcraft tribe if someone could do a 337 form on it and make that available. I'd be happy to try and do it, but unfortunately there are other far more pressing issues in the way.