Clevis or Eye to A-23822 Brake Pin Clearance

[BRENT in 10-uh-C]

Have we discussed what we feel is the proper clearance of the Pin to either the Clevis or the eyelets of the Brake Rod or Cross-shaft Arms. Looking at the print of the brake rod, it appears that the engineers called for a dimension of 0.313" - 0.318 with a average size of 0.315. The stock pin size is 0.310". That comes in at an average of five thousandths clearance (- 2½ thousandths per side).

On O/S pins, they are 0.340" and I have evidently been 'over-reaming' the holes when we ream to 0.350" -this giving ten thousandths of clearance. Any thoughts on what is too little or too much?

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[Synchro909]

You ream those holes!??! Even the diagram you posted says it is a drilled hole. Maybe overkill?
As for clearance, if I can put the pin in the hole without it falling in, I call it good. There is tension on everything 100% of the time, even when the brakes are not in use so if lost motion is your concern, don't worry.

[alexiskai]

Originally Posted by Synchro909

You ream those holes!??! Even the diagram you posted says it is a drilled hole. Maybe overkill?
As for clearance, if I can put the pin in the hole without it falling in, I call it good. There is tension on everything 100% of the time, even when the brakes are not in use so if lost motion is your concern, don't worry.

I think he meant that he's needing to ream the holes because the "O/S" (not sure this abbreviation) pins are .34", so they're too big for the holes as originally spec'ed. The spec calls for total ID/OD clearance of .005 on average, but he's been reaming to a clearance of .010, so his question is whether folks think that's too loose.

[BRENT in 10-uh-C]

Originally Posted by Synchro909

You ream those holes!??! Even the diagram you posted says it is a drilled hole. Maybe overkill?
As for clearance, if I can put the pin in the hole without it falling in, I call it good. There is tension on everything 100% of the time, even when the brakes are not in use so if lost motion is your concern, don't worry.

Yes, we ream them. The method is really more about the set-up. Originally, they likely used a very rigid fixture to hold the brake rod, and a good quality drill station. Today, in dealing with worn brake rods where generally the starting point is oblong-shaped, a drill used outside of a very rigid set-up will likely move around during the drilling which would/will create an(other) oblong O/S (oversized) hole. Reaming does not do that since there are 6 flutes cutting instead of 2. This also allows a reamer to be used outside of a rigid fixture and powered by a cordless drill motor.

As far as always being in tension, not sure that is factual. I can generally remove all the pins from the clevises without any effort which could not be done if there was tension.

Also, it is worth noting that loose fitting pins cause rattles. I am not a fan of rattles.



Colin, you are correct. I guess this is an area that I never really thought about as to what was the prescribed clearance. A sheet of good quality copy paper is about five-thousandths thick, -so there is not a lot of clearance between the pin and clevis when you think of it in those terms. While the rods don't seem to rattle at 0.010", I think I will get some smaller reamers to tighten the clearance.

[Kurt in NJ]

If you make the fit too tight slight alignment issues could cause binding

[Synchro909]

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Originally Posted by Kurt in NJ

If you make the fit too tight slight alignment issues could cause binding

And stop rattles?

[Bob Bidonde]

Structurally speaking, an efficient shear pin connection will have no more clearance than 0.0035".

[Gold Digger]

I don't have too much problem with the oversize clearance as much as the wear. When the pin goes through the holes but then is real lose where it has worn. I try and give the rods the twist rule when I get done to keep down the rattles.

[BRENT in 10-uh-C]

Originally Posted by Gold Digger

I don't have too much problem with the oversize clearance as much as the wear. When the pin goes through the holes but then is real lose where it has worn. I try and give the rods the twist rule when I get done to keep down the rattles.

I don't worry with wear since during a rebuild, we use a WD40 product on all pins, rollers, clevis and tracks on the braking system so they have lubrication.

Again, I see no need to preload or twist the rod although I doubt doing it would affect anything as the minute amount of twist would likely be disbursed on a 40+ inch rod.

[Jack Shaft]

Slip fit on the pin, I do back up the cotter pin with a hard washer to reduce endplay. As stated there is no slack in a properly adjusted system.

[hop up]

As a toolmaker I would meet the specs to .0025 per side and MSC tool supply have the reamer to do that. Also they sell expandable reamers to meet your needs as far as binding that just says something is miss aligned

[johnbuckley]

anyone care to hazard a guess as to how long the stay within acceptable spec? 200 Miles of "normal" stop/start driving or 2000 miles?

[BRENT in 10-uh-C]

Originally Posted by johnbuckley

anyone care to hazard a guess as to how long the stay within acceptable spec? 200 Miles of "normal" stop/start driving or 2000 miles?

John, I would carry your highest number out another decimal. If the pins are the higher quality ones made, and with the brake rods with an eyelet near the same size as the pin so the contact area between the two is greater, -and with lube on each pin, I would think you could mic pins after 20k miles and they would still hit within spec.

[aermotor]

[QUOTE=BRENT in 10-uh-C;1968259]I don't worry with wear since during a rebuild, we use a WD40 product on all pins, rollers, clevis and tracks on the braking system so they have lubrication.

WD-40 In my opinion is not much better than water, unless used near daily. When you say WD-40 product what are you referring to?

John

[BRENT in 10-uh-C]

[QUOTE=aermotor;1968420]

Originally Posted by BRENT in 10-uh-C

I don't worry with wear since during a rebuild, we use a WD40 product on all pins, rollers, clevis and tracks on the braking system so they have lubrication.

WD-40 In my opinion is not much better than water, unless used near daily. When you say WD-40 product what are you referring to?

John

John, I don' think you have looked at WD40 products lately. They are a far cry from the old 'water displacement' manufacturer from when we were kids. Now they make Gel Lubes, Dry Film Lubes, Silicone Sprays, Chain Lubes, Spray White Grease, Rust Removers, Electrical Cleaners and a bunch of other stuff. We use the Dry Film lube on brakes since it is made to lubricate in dusty environments without attracting any dust. We have probably been using the Dry Film for 4-5 years now, and you can definitely tell a difference.

Have a look at THIS and see what you think??

[aermotor]

[QUOTE=BRENT in 10-uh-C;1968471]

Originally Posted by aermotor

Have a look at THIS and see what you think??

This should be a useful product rather than the original "snake oil". On my will try list.

John

[johnbuckley]

Originally Posted by BRENT in 10-uh-C

.... the Dry Film lube on brakes since it is made to lubricate in dusty environments without attracting any dust. ....

Thanks ....This is the important bit as I've always been concerned that dollops of grease when mixed with road grit might become a very effective " grinding paste" !

[shew01]

Originally Posted by BRENT in 10-uh-C

We use the Dry Film lube on brakes since it is made to lubricate in dusty environments without attracting any dust.

Brent, where do you find WD-40 Dry Film Lube?


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[BRENT in 10-uh-C]

Originally Posted by shew01

Brent, where do you find WD-40 Dry Film Lube?

Walmart, NAPA, and pretty much all major mass-merchandiser auto stores all carry stuff like this. I just happen to use the WD40 brand because their sales rep. came by with the NAPA rep. and demonstrated it but I would think competitive brands offer similar type products that would work equally well.

[alexiskai]

If we're talking "odd lubricants," I wanted to put in a plug for Kano Penephite, a penetrating oil with suspended graphite. Works great when something is rusted and you can't take it apart or remove it at the moment. The oil carries the graphite into the confined space and carries the rust out. Works great on leaf springs specifically, but I also use it for bearings on toys and yard equipment, stuff that gets beat up.

I'll look out for this WD-40 Dry Lube, though, that sounds like a good addition to the toolkit.