I need to borrow an 87-89 USAF dual circuit master cyl. mount temporarily

[clinto]

Well, look at this.

 

[DavidWymore]

That's gonna be a good trick to manufacture

 

[yolner]

Yeah that doesnt look like a simple piece to reproduce.

 

[clinto]

That's gonna be a good trick to manufacture

Yeah that doesnt look like a simple piece to reproduce.

Well, in the nearly 30 years since the last dual circuit M44A2s left the assy. line, only M-series restoration has managed it but at a pricepoint that no one could afford. And I'm not sure it even took the correct master cylinder.

But I'm not your average guy and I have some people helping me who are extremely competent. We'll see what happens.

 

[yolner]

Actually would be nice to do it with a different (easier to find) MC. Either way I'll probably be one of your first customers. Always worry about those brakes.

 

[DavidWymore]

Well, in the nearly 30 years since the last dual circuit M44A2s left the assy. line, only M-series restoration has managed it but at a pricepoint that no one could afford. And I'm not sure it even took the correct master cylinder.

But I'm not your average guy and I have some people helping me who are extremely competent. We'll see what happens.

Oh, I'm sure you'll get it done, no worries there, just noticing its gonna be an accomplishment.

 

[clinto]

Oh, I'm sure you'll get it done, no worries there, just noticing its gonna be an accomplishment.

Biggest fear is what's it is going to cost. I need to get it done at a price point that people can afford.

 

[Tow4]

If you make that as a casting, the tooling cost will be too high even in China. I haven't tooled anything that size, but about half as large with similar complexity was north of $10k with a piece price of around $10 using ADC 6 or 12.

Your best bet is to fabricate that as a weldment. Depending on how much machining you have to do, I would expect the piece cost to around $1k. If you are good at welding and machining, you can get all the pieces laser cut and assemble/finish it yourself for half the cost or better.

Good project, I'm looking forward to seeing the finished piece.

 

[DavidWymore]

I agree. Plasma would be cheapest but laser or water more accurate. Could probably cut the bolt holes and pilot/locator in the plates close enough with either of the latter. Some cutting tables have milling/drilling/tapping heads to speed up those processes. Cut the pieces out with tabs and notches so they interlock and locate each other, weld together and weld tubes in with inside bores undersize, bore to finished size after welding.

 

[redmudjeep]

I have been gathering the parts to convert mine to a dual circuit system. The bracket is one of the few items that I am missing. Was figuring on fabricating one out of steel. Which will be much cheaper than the figures quoted above. Following to see what you come up with.

Mike

 

[Tow4]

I agree. Plasma would be cheapest but laser or water more accurate. Could probably cut the bolt holes and pilot/locator in the plates close enough with either of the latter. Some cutting tables have milling/drilling/tapping heads to speed up those processes. Cut the pieces out with tabs and notches so they interlock and locate each other, weld together and weld tubes in with inside bores undersize, bore to finished size after welding.

Laser accuracy is very good and to me that is worth a lot. My last fabrication project was all stainless steel mostly 0.25 inch thick had a lot of weldments with keying features for welding assembly and rectangular tubing with bushed pass throughs for pivots etc. I spoke with the fab shop owner and asked him about the laser's accuracy so I could determine tolerance stack ups and such. He told me it's pretty much dead on. The worst case would be about 0.002 +/- which for my project was nothing. When I got the prototypes I found out that he was right. I checked a couple of the smaller pieces on the MicroVu and they were just like the drawing. I was very impressed.

As far as boring tubes to size for bushings, clearance, etc. It is much more cost effective to size the tubing with the bushing size in mind so you limit the secondary operations. There is a pretty wide selection of tubing sizes available so you can probably find one that will work. If you find one that works, buy enough for your production run. Mills change processes and tolerances on tubing can vary widely from lot to lot. I discovered that after buying enough tubing to build 50 units for the initial production run and we bumped it to 100 during production. Half way through we had to start machining the bore to fit the bushing. Same tubing supplier, different lot. Lesson learned.

 

[Quido]

Laser accuracy is very good and to me that is worth a lot. My last fabrication project was all stainless steel mostly 0.25 inch thick had a lot of weldments with keying features for welding assembly and rectangular tubing with bushed pass throughs for pivots etc. I spoke with the fab shop owner and asked him about the laser's accuracy so I could determine tolerance stack ups and such. He told me it's pretty much dead on. The worst case would be about 0.002 +/- which for my project was nothing. When I got the prototypes I found out that he was right. I checked a couple of the smaller pieces on the MicroVu and they were just like the drawing. I was very impressed.

As far as boring tubes to size for bushings, clearance, etc. It is much more cost effective to size the tubing with the bushing size in mind so you limit the secondary operations. There is a pretty wide selection of tubing sizes available so you can probably find one that will work. If you find one that works, buy enough for your production run. Mills change processes and tolerances on tubing can vary widely from lot to lot. I discovered that after buying enough tubing to build 50 units for the initial production run and we bumped it to 100 during production. Half way through we had to start machining the bore to fit the bushing. Same tubing supplier, different lot. Lesson learned.

I wouldnt recommend casting. The amish in PA are off grid but do good casting work for decent prices. I have some contacts there and China if you want to give it a shot. China wants a large minimum though (100 I think). Machining something like that doesnt look cheap either. Laser/waterjet weldments probably the easier/cheaper route.

Sent from my SM-G950U using Tapatalk

 

[redmudjeep]

Any updates on the bracket? If this is not feasible to produce price wise, will you provide dimensions/specs so that people can try and make the bracket themselves?

 

[frank8003]

Whole truck for sale on SS with all this attached for $6000 today.
It is M35A2C hard top, dual brakes, dropsides, hardtop,
runs +drives + shifts good, spin ons, 1986 run out Air Force Truck...............
Blowing main seal, needs brakes, no PM's, needs NDT's, funny color......
but it has what I think you want..?

There is thousands of trucks out here that need dual brakes.
Time to scour the endless junkyards.
Time to invent stuff but I too old without inclination.

 

[texas30cal]

Has anyone considered using the electric/hydraulic boost pumps they use on hot rods that have big cams/low vacuum? If someplace like wilwood has a MC that fits the existing bracket with f/r outlets it would eliminate all the hassles/plumbing and second expensive air pack that come with retrofitting the air side.

 

[Robo McDuff]

I was looking into something like that for the 5-ton, maybe even using the hydraulic pump of the power steering. I think the CUCV has something like that, called hydro-boost? I forgot the details, but had decided that it was too complicated, expensive if bought new, and getting too far from original.

 

[texas30cal]

These are a electric pump that provides the boost to the hydraulic side of the brakes, no engine driven hyd pump needed. I think , and Clinto can verify I'm sure, that fitting a dual circuit master cylinder to the bracket on a single circuit truck is a big problem and I believe why he's looking to make brackets. I've read about this some but have never seen a dual circuit setup so it's hard to visualize.

 

[clinto]

Has anyone considered using the electric/hydraulic boost pumps they use on hot rods that have big cams/low vacuum? If someplace like wilwood has a MC that fits the existing bracket with f/r outlets it would eliminate all the hassles/plumbing and second expensive air pack that come with retrofitting the air side.

I was looking into something like that for the 5-ton, maybe even using the hydraulic pump of the power steering. I think the CUCV has something like that, called hydro-boost? I forgot the details, but had decided that it was too complicated, expensive if bought new, and getting too far from original.

These are a electric pump that provides the boost to the hydraulic side of the brakes, no engine driven hyd pump needed. I think , and Clinto can verify I'm sure, that fitting a dual circuit master cylinder to the bracket on a single circuit truck is a big problem and I believe why he's looking to make brackets. I've read about this some but have never seen a dual circuit setup so it's hard to visualize.

Some of this discussion is probably moving outside the realm of this thread. Fuzzytoaster had started a "dual circuit engineering" thread that would cover a lot of this.

That being said:

So you guys are proposing doing away with the air boost (airpack{s}) and finding a dual circuit master cylinder that will fit on the stock single circuit master mounting bracket and thus doing away with the single circuit master and the need to have a broken air system:

Right off the bat, I see two issues with that:

A. How are you going to operate the PTO? The M44/M44A1/M44A2 series trucks operate the PTO with a shift handle. 1951-1986 (single circuit) models have a u-shaped bracket that bolts to the single circuit master itself, they all have mounting bosses cast into them that are tapped for the mounting bolts.

The dual circuit trucks, having a master with no flat surface to bolt a mounting bracket to, have an ear cast into the master cylinder mounting bracket.

So if you take away the stock master and you keep the standard single circuit mounting bracket, you have no way to operate the PTO.

B. If you use hydroboost to boost the brake system hydraulic pressure, how do you get air to the gladhands? Sure, you'll still have the emergency side, but the service side is metered air from the airpack. So now you don't have air brake trailer capability.

Now, then you have all the other questions: Does a master exist that will fit in the physical space, in the right bolt pattern? If that exists, does it have a usable bore diameter? Will a hydroboost setup provide sufficient brake system pressure?

Now, consider an accident. If it is your fault, you're going to get sued. No question. If you have a factory designed system, that's one thing. What could a good lawyer do with a homemade custom system? Do you want to testify that you, with no engineering background and no formal testing system implemented a custom system of your own design?

And that's just the stuff I can come up with off the top of my head, after working for 14 hours today.

 

[texas30cal]

I understand , lots to overcome, I saw the electric setup the other day and just thought I'd suggest it.

 

[bachman502]

Let's keep this thread focused on remanufacturing the bracket and finding a substitute master cylinder. To many brake threads on this forum that just lead to dead ends.