Rocky Mountain Brakes, Stop,.... then they don't

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jmemjr
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Rocky Mountain Brakes, Stop,.... then they don't

Post by jmemjr » Fri Dec 06, 2019 11:03 am

I have a strange issue with my rocky mountain brakes. I had them on the car for many years, and late last year they started to be hard to stop. Previously they were crisp and positive braking on the pedal.The car became hard to stop and required a hard pedal. Last fall I changed out the bands on them hoping it was a lining issue, and there has been little improvement. The first stop when they are cold now is positive with a nice pedal, then after the first stop, they are miserable. You have to press extremely hard, and you cannot stop hardly at all. I have tried adjusting every way to sunday on the bands and nothing changes.

All suggestions are welcome. I really would like to stop again!

John

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Henry K. Lee
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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by Henry K. Lee » Fri Dec 06, 2019 11:11 am

John,

A lot of times the hard brake issue is an out of balance issue from the equalizer bar attached to hard to the parking/emergency brake bar.

Hope this Helps,

Hank


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jmemjr
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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by jmemjr » Fri Dec 06, 2019 11:31 am

Good Point! I'll check that next.

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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by Walter Higgins » Fri Dec 06, 2019 11:33 am

If you have messed with the linkage, go over it well and check the geometry of everything. The mistake people often make with external contracting brakes is when they want the car to stop better they shorten the rods, particularly if they have a low pedal issue. More often than not what they should be doing is adjusting the band-to-to drum clearance as once everything is set up right the linkage geometry is a constant, but where wear or lining changes occur, it is to do with how the band interfaces with the drum.

That may not be your issue since you describe problems cold vs. hot, but you need to rule out geometry problems before you can move forward with exorcising your gremlin.


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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by Les Schubert » Fri Dec 06, 2019 12:23 pm

I wonder if the drum surface has become polished to a “glazed” finish. I presume that the possibility of any oil being on the surface has been eliminated. Just some thoughts

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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by CudaMan » Fri Dec 06, 2019 1:30 pm

The pedal effort on my AC brakes went way up last year - turned out the linings were worn out and I had turned the adjusters in to the point that the return springs went into coil bind before the linings firmly gripped the drums. I installed new linings, backed off the adjusters, and all was well.

You said you already replaced the linings, so that can't be your problem, but perhaps my experience can help someone else. :)
Mark Strange
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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by Les Schubert » Fri Dec 06, 2019 2:05 pm

What did you replace the linings with. I use woven style linings on my AC brakes. I have seen various materials offered as brake linings


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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by Norman Kling » Fri Dec 06, 2019 4:49 pm

Crawl under the car and have someone push hard on the pedal. Many times the equalizer can move all the way to hit the rear of the crankcase. If so, either something is bent, the rear of the engine has sagged or the adjustment is wrong. You might need to shorten the rods to the rear wheels and lengthen the rod between the pedal and the equalizer.
Norm


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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by jmemjr » Fri Dec 06, 2019 4:54 pm

The glazing of the drums is a thought but I dismissed it as a " nah cannot be". I will look at the linkages tonight and see what is going on there

anyone have experience of the drums glazing and having this issue?

I had a new RMB kit around for another car and replaced the bands and linings from what they gave me in the kit. so it is RMB factory correct.

This is all great information, keep the ideas coming

John


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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by Norman Kling » Fri Dec 06, 2019 6:11 pm

I should have said shorten both the rods to the rear wheels and the rod between pedal and equalizer.
This is how I adjust my cars. I have three of them. First adjust the clearance between the shoe and the drum. 20 thousands Then adjust the parking brake so that the wheels turn freely in neutral but when the lever is almost all the way back, the brakes come on. Next adjust the rocky mountain brake rods to the rear wheels so that it is applied with one more click than the parking brake. That will cause the parking brake to work first when rolling backward. Next adjust the transmission brake to work 1 1/2 inches above the floor board and the rocky mountain brake about 2 inches above the floorboard. That will give you transmission brake when you push hard. This way seems to work without the equalizer hitting the engine pan.
Norm


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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by dmdeaton » Fri Dec 06, 2019 8:10 pm

I took the hard woven “fairly new” linings off my model A and never looked back. Replaced them with softer bonded shoes arced to the iron drums and the difference is night and day. I know this is a different animal than the Rocky Mountain brakes but all brake are similar in function


Check the lining surface and make sure the whole band is wearing even. Maybe just the ends or center are doing the work.

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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by Mark Gregush » Sat Dec 07, 2019 12:11 pm

While the soft hard bonded lining might be ok for the replacement cast iron drums, would not be so good for pressed steel Model T or A drums. Good idea to check for contact on drums, bands out of round. The Rocky Mountain brakes are self engaging in forward rotation, as the wheel rolls and levers are pulled, the rotations helps pull them tight. So you should see the most wear at one end not both. You might also check to see if the two pieces attached to the backing plate are in the right place, if they are wrong they can stop the band from floating forward and back in the slot. Yours may be one piece but same thing.
I know the voices aren't real but damn they have some good ideas! :shock:

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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by Original Smith » Sat Dec 07, 2019 4:04 pm

It would be nice if someone would reproduce the original correct Rocky Mountain Brakes that were cable operated. There are no problems with them! The same goes for the AC brakes. Why make something so simple, so difficult??????


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Re: Rocky Mountain Brakes, Stop,.... then they don't

Post by nsbrassnut » Mon Dec 09, 2019 6:31 pm

I did see that the problem started before changing the brake lining. Just the same here are some comments on things that I have learned about some of the modern linings in use on our cars these days.

There are several differences in the characteristics of the linings available today and you should check what you are using as well as the application where it is used. Back in the day the most common lining was a "soft" woven lining usually asbestos but sometimes woven mohair or cotton in the really early cars. This lining would quickly mold itself to the correct curve of the drum even if the contracting band wasn't quiet round. It could also absorb some oil and water without it completely coating the braking surface when in service.

Modern linings are "harder" and slower to wear down and form the correct shape to work their best.

Many antiques use ScanPac GGW Green Gripper woven green lining. It has a high friction coefficient, but has a problem with severe fade and loss of friction if the surface reaches 600F or more. It doesn't take long to get the linings very hot on these cars where there is little cooling for the drums or lining. The loss of friction for GGW can be 80% at high temperatures, but it will recover when it cools down again.

This lining is also fairly stiff and hard and I have found the need to get it to form to fit the drum. My current method is to use pieces of adhesive sanding discs stuck on the lining then lightly apply the brakes and turn the wheel by hand to sand the lining to fit the drums better. With the sand paper off, put the brakes on hard and check with a feeler gauge to see if the lining is really touch the drum. On one car I started with barely 30% contact when first installed but eventually got it to over 80% using this method. The brakes when from nearly useless to just poor (single cylinder Cadillac, stops better by carefully using reverse than with the brakes).

There are also alternative modern woven linings with a lower friction coefficient, but less fade at high temperature. A potential compromise for the operating conditions.

There are also some molded lining materials, similar to the grey found on some modern Rocky Mountain and replacement inside brake shoes. My experience here is similar. The lining needed to be sanded to confirm to the drum for the best effect. The downside with this material was where it was used on outside band brakes that could be exposed to oil and/or water. The material worked well dry, but was scary on a rainy day.

The woven materials are porous and oil and water will wick through. The moulded linings are solid and liquids can act like a lubricant if there isn't much pressure on the lining to the drum.

There was a good article in the HCCA Gazette a couple years ago which covered this in more detail than I can put in here.

You may want to explore and try a few different lining materials to see what works best for your application.

I currently have two different lining materials (GGW and a German made woven friction alternative) on order to be tested on a Hudson and a set of Ford small drum accessory brakes next spring. Both are outside contracting band brakes. The process has been a learning curve.

When you adjust the bands, but sure to check that there is free play on both sides of the front anchor point linkage (for my style anyway). Two tight and the rebound spring will bind before the band is tight on the drum. It take two people to check the brakes fully, someone has to push the pedal while the other inspects the brake action at the drum to get all the settings right.

Good luck.

Jeff
Nova Scotia

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