Potential galvanic corrosion Cleveland brakes

[MoonlightVFR]

C 170B - logbook notes Cleveland brake kit installed June 1973. Service Letter 65-41 noted in logbook.

Two (2) Bolts feed through the Brake wheel cylinder assembly casting. With great difficulty I unfastened the two bolts to detach the brake pad. The bolts did not turn freely. Bolts would not freely slide out of casting.
used 1/4 " drive 6 pt socket. Very difficult to reattach.

I am thinking galvanic reaction between the steel bolt and brake puck castinig.

These assemblies are nearly 50 years old.

This is a serious condition that must be remedied.

Am I the only one? Could not find simlar situation in the forum.

[GAHorn]

Grady, it's amazing to me that the airplane has gone thru so many annuals with the bolts in-removed, unless you believe the problem arose within the last inspection period.
These are usually cad-plated bolts. Were your's cad-plated?

Anti-seize compound (I use Permatex Anti-seize https://www.chemical-concepts.com/perma ... ant-1.html ) should be applied to these bolts as they are in a wet/exposed area and may also be exposed to salt from anti/de-icing fluids on runways and run up pads. Cleveland (Parker Aerospace) recommends Antiseize per MIL-T-5544 such as "Lubtork", made by W.J.Ruscoe Co., Akron, OH.

Walmart sells the Permatex for $7.

[Metal Master]

This is a picture of a scrapped Cleveland brake caliper.

When the bolts are frozen such as they are in this picture a larger concern is the piston bore which as seen here is heavily pitted. Even with new O-rings this will not stop hydraulic fluid from leaking past the o-ring. The edges of the caliper is crumbling from corrosion. And if you could get the bolts out and reassemble the caliper. The Back plate will not sit flat on the caliper and will cause the caliper to bind.

This picture is of the opposite side caliper in the same condition.

If none of the corrosion is present in the calipers and it is otherwise intact. I keep a 1/4 inch reamer to clean out the bolt holes. Install a new bolt which I keep in stock and treat the inside of the hole with Zinc Chromate primer. And then put a small amount of anti-seize on the bolt when installed. However in most cases when I have found the bolts stuck in the holes. I found the caliper unserviceable. These ones are toast. If you click on the picture and can enlarge it you will see how the corrosion has eaten away at the area adjacent to the Bolt holes.
Jim

[MoonlightVFR]

Thank you both for the response.


Metal Master your pictures are right on.

The new replacement cost of a Brake Wheel center has got to be very $$ expensive. Most likely these bolts are not being disassembled every annual. Just removed when pads are worn down.

The uninformed will reassemble without thinking of treating the components with anti seize. Your technique of ream and zinc chromate the hole is excellent.

I have no illustration showing part numbers. I wan to order four new bolts as spares for the future. Can you provide those part numbers or a link. Can they bolts be order from Aircraft Spruce?

I am going to do the other wheel. Will try a tip from the Tractor mechanics - Since co effient of expansion of Alum is greater that steel - apply heat from electric torch to the casting then try wrenching.

[sfarringer]

How do you clean and grease wheel bearings without removing those two bolts from the caliper?

[bagarre]

How do you clean and grease wheel bearings without removing those two bolts from the caliper?

Maybe they were performing a progressive annual where you only do one maintenance item each year.

[Metal Master]

How do you clean and grease wheel bearings without removing those two bolts from the caliper?

The parts from the pictures I posted the airplane had not flown in many years. It received new wheel bearings as well, I was able to salvage the wheels.I spent two years restoring that airplane it is now $160,000.00 1962 172. I may be worth half that. It does have a custom leather interior.
The Cleveland Parts catalog is available on line under Parker Aerospace.
http://www.parker.com/literature/Aircra ... 001-19.pdf
Many vendors sell these parts including Aircraft Spruce
Jim

[gfeher]

Grady,

Those bolts for the Cleveland 30-63A brake assembly are Cleveland p/n 103-11600, and are available from Spruce at $6.85 each. Or it's possible to use AN4H17A bolts and safety wire the heads.

The replies talking about use of anti-seize on the bolts got me running to my Parker/Cleveland maintenance manual for the brake assembly because I thought that the assembly bolts must be torqued "dry", i.e., without any anti-seize. And that's what's shown in Appendix A3 of the maintenance manual. The same thing is shown in Table H of the Parker/Cleveland Technician's Service Guide. So other's may disagree, but I would not apply anti-seize to the thread area of the assembly bolts, especially if I were using the 103-11600 bolts that are not safety wired. In any event, when Parker/Cleveland specifies use of an anti-seize on the bolts of other brake assembly model numbers, here's what it lists for anti-seize in Appendix B of the maintenance manual and Section K of the Technician's Service Guide (athough for our planes, I also like Permatex #133 anti-seize that George uses):

“Bolts/Nuts Antiseize -- Use only antiseize specified for your assembly
per SAE-AMS2518 (MIL-T-5544)
Armite Laboratories, Costa Mesa, CA
Royco 44 – Royal Lubricant, East Hanover, NJ
per MIL-PRF-83483
Moly-50 P/N 51094 – Fel-Pro Chemical Products L.P., Skokie, IL”

On a related issue which you bring up in your related post about the "anchor bolts" (i.e., the smooth pins on which the pressure plate slides), the Parker/Cleveland maintenance manual specifies use of a dry film lubricant on those "anchor bolts" (i.e., pins). See p.207 ("Lubricate the anchor bolts with a dry film lubricant (Appendix B, Section B3) specified for your climate environment: amphibious/extremely wet or non-amphibious. DO NOT USE GREASE OR OIL. These materials will attract dirt and enhance wear of the anchor pins.") Here's what Appendix B, Section B3 lists for the dry film lubricant:

“Anchor Bolts/Torque Plate Bushings
Amphibious Environment
Lubriplate X-357 Extreme Pressure Moly Lubricant
Non-Amphibious Environment
Silicone Spray
Dri-Slide® Multi-Purpose Lubricant
LPS Force 842® Dry Moly Lubricant”

I hope this helps.

[Metal Master]

I spent two years restoring that airplane it is now $160,000.00 1962 172. I may be worth half that. It does have a custom leather interior.

Jim, I like your style! I bet that 172C is the nicest one in existence. Last year of the fastback, right?

Yes

[MoonlightVFR]

I thank all of you for replies

had only noted logbook entry "SL Cessna 65-41" No paper work - No maintenance info.

gfeher esp thank you for parts numbers and much needed maintenance direction from Parker.

Good to understand that Parker wants to distance itself from ramifications of producing parts with known galvanic reactions of dissimilar metals.

I am going to bring my brakes up to known "best practices" standrds.

[gfeher]

Grady,
Even if you don't need to change your brake linings or remove the wheels for some reason (such as to grease the bearings or change the tires), you (or your A&P/IA) should remove the brake assembly bolts and clean and inspect the bolts, brake housing, pressure plate and "anchor bolts"/pins at least once a year (i.e., at annual). It's simple enough to do and really takes no time at all. There's no need for brakes to get as bad as the ones in ghostflyer's pics.

By the way, I should have mentioned this in my last post. Moly-50 is now Loctite Moly 50. Henkel Loctite bought out Fel-Pro a number of years ago. The other products/brands I quoted from the Parker/Cleveland manual are still the same as identified in the manual.