Re: 1931 Brakes

Posted by Greenfield On 2022/6/5 7:04:45

I finished up the brakes on the 31, and wanted to impart some knowledge for other's future reference considering there isn't an abundant amount of information out there on the subject. This relates specifically to the Bendix, three-shoe brake system used on at least the 30 and 31 models, and perhaps 29 and 32 as well. All in all, things turned out really well.

1. I sourced the materials I needed from McMaster-Carr. They sell a brass mesh infused brake lining material and the necessary rivets. The lining material cost $7.55 a foot, and each wheel consumes four feet of lining material (yes, you read that right). The necessary width was 1.75 inches, and thickness was 3/16. I suspect Max Merritt uses the same stuff, but charge twice the price.
2. McMaster-Carr additionally had the hollow-tipped rivets needed to secure the linings to the shoe. I used rivets with a 5/16 head, only because that is what was used on the shoes I was removing. If I had to do it again, I'd use a rivet with a 3/8 head, just for additional holding power. In terms of the rivet, a 5/16 head is a "4" and a 3/8 rivet is a "5". The diameter of the rivet shank is a 9/64 (the hole in the shoe is 10/32). Hollow tipped rivets have a working range, which is the sum of the thickness of the shoe (.10" thick), and the amount of remaining lining material where the rivet is recessed (about .10" is what I did). The length of the rivets I used was a "4.5". If you want to use a 5/16 rivet, then order 4-4.5, and if you want a 3/8 rivet then order a 5-4.5. McMaster sells them in bags of 100, and you'll need two bags for all four wheels.
3. The rivet tool was sourced from Model A Ford suppliers. Seehttps://www.brattons.com/BRAKE-LINING-RIVET-TOOL/productinfo/2710/

The tool enables you punch out the old rivets and forms the new rivets by striking the interchangeable punches with a hammer. It cost about $30.

To build the liners, line up the material on the shoe, measure and cut it with an angle grinder. Place back on shoe, and use four or five clamps to tightly hold lining material to shoe. From the interior of the shoe, I used a tiny drill bit to drill pilot holes in the lining material to fit each shoe. Make a witness mark on the lining and shoe to ease reassembly. Then, unclamp lining and head to a drill press. I established the stops on my drill press so that about .10" of lining material remained at the base of the rivet hole. This permits you to achieve the Packard recommendation that 1/16" exists between the top of the rivet and the surface of the lining when assembled. I used a 5/16" forstner bit, very accurately lined up with the pilot holes, to cleanly drill out the rivet holes. Use the old liners to practice on to help establish your drill press depths, and I mic'd the hole to get it to get the liner thickness (in the hole) to about .10". The lining material has a curvature to it, so its necessary to bend it backward to ensure the drill site is as flat as possible, otherwise the bit might break through the lining which would not be good. I initially thought the "woven" nature of the lining material would cause it to get ripped up by the bit, but the lining material is so stout that it drilled like it was wood.

Once the rivet holes are drilled out, I used a larger drill bit (9/64 or so) to drill the pilot holes so that the rivet shank will fit. Push the rivets through the lining material, and lightly tap the rivets with a hammer and punch to set them. Then, using the witness marks, line rivetted linings back up with the holes in the shoe and again use clamps to hold everything together. A dental pick was especially helpful in lining up the rivets that needed a little persuasion to line up with the holes in the shoes.

Once the rivetted lining was mounted back on the shoe, you can again use the rivet tool to finally form the rivets to secure everything. Place the head of the rivet on the anvil side, line up the punch on the hollow tip, get everything as square and plumb as you can, pull down tight on the rivet head, and give the punch a whack with a hammer. You should get a nicely rolled rivet that holds everything tight and solid. I found that starting the rivet strikes on the apex of the shoe, and working out to the ends, helped eliminate any gaps between the lining and the shoes. Use an angle grinder to bevel the linings on the ends of each shoe.

I cleaned everything, and used lithium grease on the eccentric, anchor points, and other friction points. You have to find the "neutral" point on the eccentric to minimize the profile of the reassembled shoes to slide the drum back on, and some the linings took a little sanding to fit. The Bendix system basically requires you to get the linings very close to the drum for effective operation, and requires knocking the anchor bolts such that the linings (i.e. on the ends of the shoes that correlate to the location of the anchor points) are spaced about .005" from the surface of the drum . It was a tad awkward and difficult to achieve this considering there are things in the way on the back of the backing plate. I found that I could open the port on the drum, insert a feeler gauge between the lining and the drum surface, and insert a screwdriver a lever the shoe against the drum to achieve the .005" gap. Tighten the anchor bolts up, and I was good to go.

Everything else was adjusted per the Bendix instructions, and I have to say my brakes work really good. The job cost about $350 between the materials, tools, etc. Good luck!