A fellow member was kind enough to send me his old, original AC brake assemblies for free when he decided to switch to a new set of Rocky Mountain brakes. So, I have been using reprints of some of the original AC brake ads as a guide to help me fabricate the missing parts, here is what I have so far:
The pedal shown is one I bought cheap on ebay to help me form the brake arm strap. To start with, I plan to try and get the original cable and pulley system to work. I'll be installing the system over the winter, we'll see how it goes!
I would like to get some different brake lining material to replace what the brakes came with, can anyone make a recommendation? I have heard good things about "green gripper" linings, where is a good source for it?
Maybe Model A brake lining?
I agree with Les,Model A emergency Brake lining is good. You had best weld up those eyelets on that turn buckle,or they can come apart.
For what it's worth, the linings that came with the brakes are brand new and, according to Chaffin's, what is supposed to be on AC brakes.
Also, as you noticed when you opened the box, I never had the turn-buckle set up on my brakes. The black arm of the pulley just hooked around the brake pedal and was held there with a radiator clamp. Maybe that's why I was never able to adjust them very well.
However, I'm extremely happy with the new Rocky Mtn's and glad I changed. Wish you well with the AC brakes.
If you want to make the release springs work really well,substitute old valve springs .
Mark, if Steve Shelton will chime in here, he has a good video of his a/c set up that he installed a couple years back. I think he is very pleased with them. KGB
here is the video link on youtube. It doesn't really show how I set the linkage up but shows them working. I had the brake band loose enough to not contribute as I was working on the AC brake adjustment.
As for my set up - I went to TSC and bought some cable, a flat pulley, and turnbuckle, and a gate hinge. The gate hinge is the kind you use on a pipe gate. Oh, and some 1/4 inch rod.
I put the gate hinge around the torque tube with the part the pin would go through to the top. The rod goes through that and the hinge keeps it from rising when you step on the brakes. I Welded a tab on the brake pedal and hooked a clevis (bought from a marine supply place online) to the tab. Rod threads in the clevis, runs through the gate hinge, connects to the turnbuckle which connects to the flat pulley. Cable goes through the pulley to each brake.
I ended up adding a set of springs on the back to hold the brakes open.
The trick to these things is mostly about getting the brake drums flat and round. A lot of tinkering with a grinder. They DO work (as you can see) but I will proffer that they don't work as all as RM brakes. Two reasons (my opinion): 1. The RM kits comes with new drums already nice and round with a flat surface, and 2. the RM drums are larger. The increased diameter gives more leverage.
Finally, Jack Daron is dead on about the old valve springs.
Hope this helps!
Oh, final final note: I run these with a fully functional OEM brake band. Aside from the seller's "display only" tag and the potential for liability, I don't like all my eggs in one basket.
Final final final note: If you have an auxiliary transmission you HAVE to have some sort of wheel brakes! I remain shocked to see that there are people out there with a warlord or whatever relying only on the tranny brake.
Mark, Glad to see that you are working on this project. I would suggest that you improve the original design by enlarging the hole of the rear retainer so the band can move forward in the direction of rotation when the band is tightened. This will allow the brakes to self energize and give you more breaking power. You don't need much movement but the modification will greatly improve breaking.
Hi: I have a full setup that I was using and removed from the car when I sold it. I made a separate 4th pedal attached to the hogs head to activate them. I then made up a new set of running boards so as not to cut up my originals. I had a lot of fun with the 4th pedal, as no one knew what it was for. It gave me 2 sets of brakes. My only complaint with the ACs is they fade"" pretty quick. I can post some pics in a couple days if you need any more info as to your setup. I am not near my parts at this time.
Thankyou all for your comments! Steve, I had found your video earlier from a Google search on AC brakes, great video. I have also seen T. Oliver's video on his AC brake installation. He used pull rods and an equalizer setup instead of cables.
I do plan to keep the transmission brake functional along with the AC brakes and parking brake, so I'll have 3 braking systems.
Thanks again Bob for the parts, glad you like your new RM brakes. The reason I'm looking for replacement band material is that one of the bands broke at the end rivet hole, probably during shipping.
Glen, I'll look at enlarging the rear retainer hole, I like the idea of giving the brakes some self-energizing capability.
Oh, and Donnie, any pics you can add would be greatly appreciated, thanks!
McMaster-Carr has the brake lining matterials with and without the brass metal imbedded. I used this when relining a set of AC's and am happy with them.
Hey Mark, Looks like you ready now to make some brakes for the Front Wheels?
Check out the McNearney and the Big Four for ideas.
Mark, It is interesting to note that Jack Sunderlin, the original manufacturer of new Rocky Mountain brakes redesigned them because they were not self energizing. He used the AC design shown in the advertising shown above. This was a mistake because all he had to do was relieve the restraint at the rear pivot bolt so the band could move forward a slight bit in the direction of rotation. This would have made the brakes self energizing and retained the true Rocky mountain look..
Hello Glen, Do you have any original large drum Rocky Mountain brakes with the cast bracket that goes under the axle, I presume the drum dia is the same as the large drum supplied originally. I bought from you many years ago the modern style but I would prefer to go 'original'. With so many people changing to disk brakes I thought there might be a chance that some of these may become available. I made large Cast Iron drums to make the new ones work better, which they do.
Many thanks, Nigel
Glen, I took one of the AC brake assemblies apart yesterday. The rear anchor bolt is 1/2 inch, probably grade 2 as was common back then. By good fortune, the threads in the mount bracket that the anchor bolt threads into is the perfect size for a 3/8-16 helicoil, so I chased the threads with the helicoil tap and installed an insert. I plan to replace the 1/2 inch anchor bolt with a 3/8-16 grade 5 bolt with a washer under the head.
The smaller bolt should give the rear anchor some room to move and give some self-energizing action. I could go up to a grade 8 bolt, but I want something back there that will bend if it gets overloaded instead of snapping.
There was a small spring inside the rear anchor strap to preload the brake band assembly aft, I plan to re-install the spring (I might have to stretch it a bit) with the smaller bolt. The spring is probably there as an anti-rattle provision.
One big challenge I can see coming is getting the pedal bracket and linkage to fit under the floorboards, it looks really tight up there. Does anyone else running AC brakes have any tips?
Thanks for your interest!
Nigel, Sorry, wish I did have a set of original Rocky Mountain Brakes. If I find any I will let you know. Mark, You might consider opening up the width of the retaining bracket a little instead of changing the bolt. The additional clearance needs to be toward the ground so the band can move toward the top, You need about 1/2 inch movement capability. As for fit of the linkage I always use brake rods and a equalizer like the one on the Rocky mountains. This gives you a little more leverage and is easier to fit. As Nigel said above, the brakes also work better if you use cast iron drums. You might consider making these also. Just a note. As you may know, Larry Sidmore is making AC brakes with brass castings. These were original made by Dan McEachern. I bought 2 sets from Larry and spent a day modifying them so they would work correctly. I sent the information on how to fix the problems to Larry and never received an acknowledgement or a thank you. Never bought any more. Do you plan to sell your brakes? If so let me know.
I have original ACs on my '13 and find them to be quite satisfactory as a rear brake. I'm now evaluating my mcNerney style front brakes
Update - I've been slowly working on the AC brakes, interspersed with other projects. I bought new "Green Gripper" lining material from Chaffin's and mounted it to the bands using the proper countersinking and rivets:
I also bought a couple of new brake drums on eBay and painted them up. I left the inside and outside surfaces where the brake shoes and bands will fit bare steel:
After looking under the car in the area around the brake pedal, I don't think that the pedal bracket I fabricated is going to fit under the floorboards, it's just too tight under there. So, I have decided to go the route others have done and ordered the brake equalizer and a Rocky Mountain brake pedal from Lang's. This will move the linkage to the underside of the pedal shaft instead of above it and allow everything to fit easily under the floorboards.
Since the brake assemblies are original ACs and not the newer reproductions, the arms are set up to use a cable, and I want to at least try the cable setup. So, my current plan is to attach the pulley to the bottom of the equalizer, probably with a turnbuckle assembly so that I can adjust the tension easily.
Hopefully there will be enough travel and adjustability in the linkage to allow for firm braking action when the pedal is depressed, without any dragging with the pedal released.
I'll continue to post updates as things move (slowly) along.
This is a question for Glen Chaffin about self-energizing AC brakes. I'm fitting a set of Larry Sidmore's repro ACs to My 1925 T coupe. The retaining bolt at the back of the band seems to have some play with the retaining loop that's riveted to the band. Is that sufficient for self-energizing action?
I was under the impression that band brakes are self-energizing because of the wrap of the band around the drum, kind of like the way harpooned whales were controlled manually by wrapping the harpoon line around a post (for a few turns) and feeding it gradually by hand from a coiled rope in a tub.