I have a 31 Model AA chassis and I'm not real interested in swapping out rear/front ends. I would like the advice to stick with what I have. The goal is to turn this into hydraulic brakes Heres a close up of the brake actuator (I guess is what you call them when they are mechanical...The wheel cylinders counterpart). It is on the bottom of the backing plate (which I think is unusual but that may just be my ignorance) The push rod goes through the hole in the backing plate as seen above and continues through the I beam axle and ends in the below image (the trailer hitch ball looking thing), which I am assuming just has some gears in it that allows the rotation of the lever arm (drawn in red) to be turned into the downward linear force applied to the pushrod: What I am thinking about doing is trying to find a cylinder that will fit in this small space (replacing the traioler hitch ball thing) and push the rod down through the axle like it is already being done. It can be slightly larger than the trailer ball hitch thingo but not too much because it has to fit inside the backing plate recess when all put together. Am I being stupid, do cylinders that small exist, should I be completely rethinking my strategy? The original plan was to find a cylinder that would replace the mechanical actuator, but this other way I think would prove to be way easier as I would just be changing one thing. Also - Whats the best way of going about finding different sized cylinders? I'd like to have some idea before headin to the junk yard so I'm not spending the entire day just removing drums for cylinders that aren't even close to the size I need. Any help appreciated Scott
I'll bet there is someone on here that could advise you on which complete hydraulic backing plate assembly would be suitable. Looks like too much unnecessary engineering to me, to try and convert the setup you have.
Before you get too deep into the conversion idea. I have witnessed many conversions where the end result (hydraulic) perform no better than before. With that large truck, are you going to lower it, modify it to a point where the mechanical brake cross-bars and linkage interfere with the drive-train? I would never convert a system unless, as I said, your choice of drivetrain components will interfere with the mechanical brake components/linkages.
Not lowering it, but do think that that my driveline will interfere. May I could just try to rework the levers and such for clearance, but I definetly want to give Hydraulic a lot more thought. Scott
These are 14 inch drums (Big Truck), with a bolt pattern thats 5 on 6 7/8. I would really hate to lose the wheels, if I lost um I might as well change out the rear end, but I don't want to do that. thanks Scott
There have been a lot of replacement parts for both the front and back mechanical brakes that let them float to an extent to give you some float to them as in hydraulic if your going to stay with mechanical thats OK just make sure everything is spot on. pins fit tight , roller plates built up and ground flat
The first question are you keeping stock engine or what. If anything close to stock put the mechanical into first class shape using a high friction [ie soft] lining and making all linkage as new. Real later V-8 power change the axles. Unless you have a lathe, mill and real good design/engineering skills you are just kidding your self. You could make a composite system with hydraulic cylinders operating the levers at the wheel .
I'm doing a Restoration Hot Rod I guess. 1931 157 inch wheelbase AA 1976 300 ford straight six 1992 ZF S542 5 speed trans 1931 town sedan body Making a conglomerate somewhat original looking Ford Model A Quad cab pickup This is the basic goal but probably a somewhat different bed and he has all stock parts just used a different body.
Dang. I like that. Sure. If there's a lot of obstacles, hydraulics can solve that. The shortest distance is not always a straight line....... I can visualize making new backing plates from scratch and mounting donor wheel cylinders. Or once the decision is made, strip the hardware off the existing ones and weld up the un-needed holes. On my hot rod Nash (I kept the mechanical system) the crossbar needed to be lowered about an inch and a half to clear the donor transmission housing. The cross-bar hung on brackets off the bottom of the frame flange, so that was fairly easy to do. I think your crossmember goes through holes in the frame web???, which might make lowering the cross-bar a little more difficult.
I have two of them one on top and one that attached to the rails at the bottom. Sorry that this is the best pic I could find.
Quite opposite your stated intentions, my goal was to keep the mechanical brakes and build around them. I took the body off, moved the radiator/motor-trans-assembly/Cowl, etc. forward a couple of inches to keep the fat part of the gearbox(GM 3-speed-Saginaw with open driveshaft) ahead of the Brake cross-bars, including lowering the crossbars an inch or so. That, consequently, required re-fabbing the pedal mount bracket...........
Fast forward a couple of years in your mind. When talking to the crowd that gathers to admire your work, and considering the goal, there will be a BIG crowd, will the configuration of the brake system enter in the discussion? On my Off topic Chivvy pickup I converted to juice brakes with discs on the front. Now, more often than not, I regret it. Of course if I had not converted, maybe I would regret having not done it?? Ha.
Are you settled in with power/driveline changes? What motor, transmission? I'm assuming you're keeping the rear axle/torque tube setup..............
yeah pretty settled with the motor and trans, I like the 300 straight six cause they are easy to work on, reliable, and good low end torque for pulling this mammoth around (Not exactly wanting to go down drag strips or anything). I wanted to keep the torque tube and rear end with the 5.14 gears which led me to the ZF S542 trans. ZF S542 trans close ratio: 1st - 4.14 2nd - 2.37 3rd - 1.42 4th - 1 5th - 0.77 Rev - 3.79 I know a lot of people say get rid of the tube, but I like it and am gonna try it anyway. The ZF gearing with the overdrive is the only thing that could get me close to where I want to be without spending thousands on a trans plus a gear splitter. The only thing is that the ZF is massive, and I'm afraid I'm gonna have to do more cutting on the floor than I would have liked. I'm not planning on lowering the chassis any so I may be able to let the engine/trans ride kind of low, but it is still gonna be a problem. I've got a few weeks of cleaning and planning and then the engine and trans are going in for the begining of the mock up.
It would seem to me that if you find a 14" hydraulic brake from some other truck, you could still use your existing hubs and drums and not lose the bolt pattern. The only thing you need is the backing plate/wheel cylinder/shoe assembly. The drums don't care how the brakes are actuated.
Hi, I also have a Model AA truck. Have you thought about using a Ford drivetrain conversion kit in order to keep the rear end the same, or are you going to trade out your drivetain altogether? --Labienus
The Jalopy Journal
