CMP brake question

[Jacques Reed]

Originally Posted by Phil Waterman

Hi Lynn. Grant, Rob

Thanks for the input, you've added to the list of things I want to check.

1. The idea of the spring having lost tension, fits in with the earlier observation that this adjuster turns easier than the others. Next step will be to put a torque wrench on it and see if it really is turning easier.

2. The thought that the spring itself might be winding up as the adjustment is being made, had not occurred to me.

3. Confirming that the adjustment cam is not loose on the bolt is a big thing to rule out. If it is I can not think of the damage that it could do if it dropped off in side the drum. So I suspect that pulling the drum will be a necessity.

4. A broken or weaken spring from crack, rust, age, is I suspect the most likely cause. But what is the fix? Replace spring, or put a spacer under it to increase tension?

5. Replacing the backing plate is probably the hardest, as I have no spare and a used one is just as likely to have the same problem.

Cheers Phil

PS - While I was typing Harry provided a source for NOS replace part. Thanks Harry will follow up if that is the cause.

Hi Phil,

Just looking at a brake adjuster cam that I removed a long time ago from a F15-A rear backing plate. I doubt if the cam is turning on the bolt as the elongated hole on the cam would prevent that.

A broken spring could well be the problem as that is the reason I removed this adjuster cam. The spring in the picture is a new one I had made up. In the end I found two NOS rear backing plates and never proceeded with replacing this cam's spring and another cam than had a broken spring.

If the spring is not broken then the thought occurred to me, what if the cam is resting on the shoe just past the highest point, and the return spring is enough force to rotate the cam back towards the low point on the cam that has a weakened spring?

If the linings have substantial wear it is possible the cam would be close to the top of the cam at the contact point with the shoe.

If you have to remove the cam to replace a spring a method that worked for me was to carefully grind down the side of the flat on the bolt where it is splayed to hold it to the cam. I used a Dremel cut off disk to do it. Was going to then weld the cam back on to the top of the bolt but never had to do it thanks to finding the NOS plates.

Will look forward to hearing the solution to the problem.

Cheers,

[Tony Smith]

Or you could get a bit fancy?:

https://www.ebay.com/itm/39-48-FORD-...sAAOSwKIpWEWN1

[Jacques Reed]

Real purdy!!!

Checking the F15-A parts list, the studs, cams, and springs are not unique to CMP vehicles so these stainless steel ones should fit properly. Parts do not have an asterisk in front of their number so they should be generic to all Fords of that era.

92Y 2038 Stud- adjusting cam
92Y 2041 Cam- shoe adjusting
92Y 2049 Spring- brake adjusting cam

Makes part finding a little easier when the * is not there.

Cheers,

[Phil Waterman]

Hi All


Well as I think everybody suspected the problem is in the tension spring on the adjusters. So I will be ordering some replacement springs.
Trailing Adjuster before.jpgTrailing Adjuster.jpg

The rear most or trailing adjuster once the brake shoe was pulled back could be turned by hand with almost no resistance. Once the end was ground off so the adjuster could be remove revealed the spring was broken.
Leading Adjuster Before.jpgLeading Adjuster.jpg






While the forward or leading adjuster required 25-30 ft.lbs of torque to turn, but on close examination it was discovered was broken into 3 segments.

Trailing Shoe Full.jpg



Take a look at the brake shoes, these are the original shoes mileage 24844.

[Phil Waterman]

Continued

Here is the trailing shoe
Trailing Shoe Full.jpg


This is the unit I made up for pulling drum and hub assemblies. Some of you might recognize as the parallel lift platform I use for holding to drill press when drilling frame rails.


Hub Puller 2.jpg DrillHorizontal.JPG


Will report back as I get replacement springs and reassemble.


Cheers Phil

[Phil Waterman]

Originally Posted by Tony Smith

Or you could get a bit fancy?:

https://www.ebay.com/itm/39-48-FORD-FLATHEAD-STAINLESS-Brake-adjuster-kit-W-SS-SPRINGS-Halibrand-SCTA/280857926801?hash=item41646fdc91:g dsAAOSwKIpWEWN1

Hi Tony


Thanks for the lead, but it turns out that these are for the adjusters for the pickup truck and use a 7/16 bolt. I contacted the seller above and he responded very quickly saying they are 7/16 inch.


The search goes on.


Cheers Phil

[Lynn Eades]

Hi Phil, I could supply the bolt and snail, but unfortunately I don't have the spring as nos.
I could strip them from a back plate but they are rusty.
Surely someone closer can help, but if no one steps up, send you address.
Lynn.

[Phil Waterman]

Hi Lynn


Thanks for the offer, but I think I have a sources for a replacement springs that I can cut to length. Comes in 36 inch lengths. Another supplier looks to have ones which will work but has a $40 minimum order.



So I got to do a little more measuring, in particular is the spring force to compress the spring one inch.


Cheers Phil

[Grant Bowker]

I suggest caution cutting a spring for this application from a longer coil as the springs I have seen for the snail adjusters have flat, closed and ground ends. I believe most springs of similar dimensions (free length, wire diameter and number of turns) will behave similarly unless there is a large difference in the material properties. I have found several springs wanted for CMP projects at https://www.centuryspring.com/ You can search their catalog online by inputting whatever information you have about the spring you are trying to match.

[Phil Waterman]

Hi Grant



Century is one of the sources I was looking at this afternoon, spring compression strength I will try measure tomorrow.


Cheers Phil