My 1950 F-5 MH has air over hydraulics brakes. This system was not stock on Ford F-5s (or anything else I know about), and apparently was not installed by Marmon Herrington (according to Chuck at Chuck's trucks). Assume it was installed with the body. I've been disassembling the whole brake system and locating replacement parts. One part on the air chambers (there are two-one for front brakes and one for rear) has me stumped. On the non-pressure side of the air chamber are two mounting studs, used to mount the chamber to a bracket and to the hydraulic master cylinder. Of the two studs, one is a regular stud. The other has a pin (not sure what else to call it) that goes through the stud and can move in and out. The inside side of the pin had sort of a button on it. Pics are hopefully below.

(1) air chamber and master cylinder in truck


(2) air chamber out of truck and bolts removed (note this is the other chamber-which is different, with the non-pressure palte being steel, not aluminum)


(3) non-pressure side of chamber, showing the two mounting studs (outer) and the pushrod (middle, which actuates hydraulic master cylinder). Top stud has pin in it.


(4) one of the studs with a pin


(5) stud showing that pin moves in and out


The air chamber is a Bendix Westinghouse unit. Marking are as follows:
- Pressure plates (both are the same): BW 202880 Type B
- non-pressure plate 1 (steel): BW 203585 [not positive of those numbers)
- non-pressure plate 2 (aluminum): BW T-SA-1644-7

BTW, the local truck parts place (Fleet Pride) was able to locate replacement diaphragms for these (BW 200001), but no luck on the air chamber itself or the studs with pins.

Anyone know what the function of these pins in the studs would be? Is it necessary to match exactly? Where would I find a replacement?

Thanks tons!

Duane.

 

Anyone got any ideas on this? Thanks, Duane.

 

Duane - This might be a good example of why the FTE "big kids" (as Penn Dick calls them) might want to include F-5s in with the new Big Trucks forum. An air brake system like yours would have been more common on the Big Jobs I'd speculate. I just went through my Hildy's Blue Book of Ford approved optional equipment and find several brands that were available. A Bendix air system was standard equipment on F-8s it says. And besides Bendix Westinghouse there were Kelsey-Hayes, Midland, and Wagner systems available as factory approved installations. Finding tech info on any of them will be a real task, though, unless somebody steps up that's been down that road. And if you've already run it past Chuck, I don't know where you go after him. Stu

 

My best guess is the pin releives air on the back side of the diaphram. We have been
doing busness with Napa since 1951 & are good friends. I get many books from them
just for the asking. My master brake book has them, called "air packs". Ill get the
part no for you. Simply put the existing air line & hydralic line to it, and you will be
all new and all set. Im sorry that this site will not allow me to attach a photo, but
the new unit Bendix is similar to yours, but with a new master cylinder.
sam

 

Stu, Thanks for the thoughts. I would tend to agree with your speculation about this type of system being more common on bigger trucks. Although, in my limited experience so far (only a couple years) I do not know of any other trucks with an air over hydraulics system like this. I'm sure there were some. Actually, I've only talked generically to Chuck about the sytem, not about specific parts. I'm checking with him on some other parts right now, so may see if he can find anything.

Sam, That sounds like a reasonable guess as to function. The two "air packs" are slightly different on the non-pressure side, in addition to one being steel and one being aluminum. One of them has three or four small holes, about 3/16" diam, drilled through the case, which might also relieve air on the back side. but that air pack also has the stud with the pin too. Still sounds like a good explanation to me. If there is anyway you could scan the pertinent pages from your master brake book and PM them to me, I would super appreciate it. I think it would help to have any pictures, and all different part numbers for the unit and individual parts. but whatever you can provide will help.

Thanks, Duane.

 

Duane - I was thinking too that the pin might be an air release value. Another source of repair info might be an old Motor's Truck and Tractor Repair Manual. I've got one dated 1953 that has a lot of pages on air and vacuum brakes, but I don't see any diagrams that match your pictures exactly. The old books are on eBay all the time and might help some. Finding the needed parts, though, would be another matter. Stu

 

Duane - As I've looked through the old Motor's book there is a section on a Bendix "Air-Pak" power unit. The introductory text says the following:

The Bendix Air-Pak is a combination compressed air, hydraulic power brake unit for use on vehicles having hydraulic brakes and a source of compressed air for brake operation. The device consists of three basic units:
1. A compressed air cylinder, which includes an air pressure operated piston and push rod.
2. A hydraulic cylinder, which includes a hydraulic piston with a built-in check and a residual check valve at the output end of the cylinder.
3. An air pressure control valve, which includes a hydraulic pressure operated piston, an air pressure poppet valve, an atmospheric pressure poppet valve, and an air pressure control diaphram.

If that sounds like what you've got, or if you see the "Air-Pak" written on yours anywhere, let me know and I'll do some scans of the pages/diagram that pertain to it and do you a PM. Stu

 

Stu,

Appreciate you looking that up. It sounds different. I've seen nothing (so far) that says air-pak on it. Sort of corresponding to those numbers, I have:
1. An air pressure activated chamber (not really a cylinder) that through a diaphragm operates a push rod. This is connected directly to 2.
2. A regular master cylinder (don't know about check valves (something to think about, even if I do not have the air-pak)).
3. A foot valve, which is an air pressure control valve, operated mechanically from the brake pedal, to deliver varying amounts/pressure of air to the chamber/diaphragm (1.).
Sounds different to me.

I'm going to the Carlisle show tomorrow, and if there are the right types of vendors (I've never been to this one before), I will be checking out old air brake systems for sure.

Thanks,

Duane.

 

This thread gets me started on my next project. I have a '61 C-550 with vacuum assisted hydraulic brakes (ex fire truck) with a 292 HD, a Clark 250V(direct) and a Timekn D-160(?) with a 6.20 ratio. I need to set it up to pull an air-braked trailer for going to shows. It looks like installing the air supply system will be the easy part. The question is how to get the air to the service side of the trailer. By either installing a hydraulically operated air valve, or the other means looks removing the vacuum assist and going to an airpak with a discharge fitting for a trailer service line. Either installation would need to run through a tractor protection valve. Any info or links would be appreciated.

 

The pin in the stud is to show how much the chamber is traveling to apply brakes.Similar to brake pedal height
If the pin travels all the way it would be like you pedal on the floor,if it barely travels that would be a full pedal