modern dual circuit air over hydraulic brakes

[Mullaney]

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So, I have to ask... Will we eventually see a replacement (bolt-on) Air Disc Brake kit for heavy truck axles? OR is it never going to happen with older military trucks mostly because the old axle technology has just "moved along"?

There is a Meritor KIT225222 for example. They are darn EXPENSIVE, but then again too we would have a spring brake chamber and air powered braking system. The spring brake automatically gets applied when the air gets too low. Better than a mechanical dual brake system...

 

[rustystud]

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So, I have to ask... Will we eventually see a replacement (bolt-on) Air Disc Brake kit for heavy truck axles? OR is it never going to happen with older military trucks mostly because the old axle technology has just "moved along"?

There is a Meritor KIT225222 for example. They are darn EXPENSIVE, but then again too we would have a spring brake chamber and air powered braking system. The spring brake automatically gets applied when the air gets too low. Better than a mechanical dual brake system...

I've looked at that kit from Meritor and yes they are extremely expensive ! It would cost more then my truck is worth and then some ! Plus all the fabrication for our older axles.
I would go with one of the kits from Boyce or try what several members here have done first.
The transit agency had toyed with that idea before I retired, but in the end the cost was too much since the drum brakes meet all federal standards of stopping.
I'm sure in the future the newer buses and heavy trucks will come factory with air disc brakes, but that is the future.

 

[Superthermal]

Info on Hydro-max units. Info on electric motors relay/peddle control to be interesting(Figure 6) and the info on the power steering hydraulic pressure and GPM to be important to reference. There was no spec sheet to give a max PSI input. The general info in the screen shot below was on page 15.

http://1999southwind.com/DOWNLOAD/Bosch%20HydroMax%20Booster%20Manual.pdf

I did not see a brake fluid volume Min/max and output pressure comparison for a 1.75 or 2" master which would be helpful to determine if one or the other would be preferred/required if keeping drums on a 5 ton or using dual piston or 4 piston brake calipers on rotors. There is a graph giving a general pressure output PSI for the larger 2" piston which tops out about 2000 psi.

https://learning.hccs.edu/faculty/hugh.mann/class-presentations/demr-1317-basic-brakes-systems/hydraulics-air-over-hydraulic-brakes/hyd-brakes-and-air-over-hyd-brakes

This last link has a graph on the 1.75 piston "typical" PSI

 

[Bigsbetter]

Those valves still need two inputs for the two outputs.

Could it work if you split the single line with a T fitting to have 2 inputs into the proportioning valve and then 2 outputs? I understand the system would be ‘single circuit’ before the Tand proportioning valve, it then dual after that which would provide more safety.

 

[banditt1979]

Curious to see if there has been any forward movement on this. Also found a thread where a guy mounted his hydra max behind the crossmember to keep the original pedal assembly, thought I would share

Hydro-Max Brake Assist *pics added* (long read)

If you've not heard of this, don't feel bad. If, however, hydro-boost rings a bell then you're on the same page. :) Can't sleep so thought I'd post (will post pic some point today) about a project I've been working on. I pretty much expect some 'flaming' about this but I think I'm well...

steelsoldiers.com

 

[fleetmech]

Returning to the site after a break from much internet use......

The short answer is no, i haven't made much progress other than amassing a few parts. The long answer is that now I need to take some action. What was to be one of my last drives before putting the deuce away for the road salt season turned into the last drive for the season when my airpack seal let go and sent all my brake fluid into the air side. I went from full brakes, to half pedal, to no brakes in three applications while going down a long hill. Thankfully there was nothing at the bottom of said hill and i got it turned around and home safely.

That experience pretty well convinced me (if I wasn't before) that the stock system has to go. I haven't decided if im going to try to buy or build.

 

[banditt1979]

Returning to the site after a break from much internet use......

The short answer is no, i haven't made much progress other than amassing a few parts. The long answer is that now I need to take some action. What was to be one of my last drives before putting the deuce away for the road salt season turned into the last drive for the season when my airpack seal let go and sent all my brake fluid into the air side. I went from full brakes, to half pedal, to no brakes in three applications while going down a long hill. Thankfully there was nothing at the bottom of said hill and i got it turned around and home safely.

That experience pretty well convinced me (if I wasn't before) that the stock system has to go. I haven't decided if im going to try to buy or build.

Glad you didn't get hurt or hurt anyone else! I hope to see your project get moving again soon.

 

[HDN]

Returning to the site after a break from much internet use......

The short answer is no, i haven't made much progress other than amassing a few parts. The long answer is that now I need to take some action. What was to be one of my last drives before putting the deuce away for the road salt season turned into the last drive for the season when my airpack seal let go and sent all my brake fluid into the air side. I went from full brakes, to half pedal, to no brakes in three applications while going down a long hill. Thankfully there was nothing at the bottom of said hill and i got it turned around and home safely.

That experience pretty well convinced me (if I wasn't before) that the stock system has to go. I haven't decided if im going to try to buy or build.

That's absolutely wild! I'm thankful my truck came with dual-circuit brakes for situations like this. I'm glad everyone is safe

 

[Superthermal]

Returning to the site after a break from much internet use......

The short answer is no, i haven't made much progress other than amassing a few parts. The long answer is that now I need to take some action. What was to be one of my last drives before putting the deuce away for the road salt season turned into the last drive for the season when my airpack seal let go and sent all my brake fluid into the air side. I went from full brakes, to half pedal, to no brakes in three applications while going down a long hill. Thankfully there was nothing at the bottom of said hill and i got it turned around and home safely.

That experience pretty well convinced me (if I wasn't before) that the stock system has to go. I haven't decided if im going to try to buy or build.

Even with my rig working very well, I am always leery of the breaks. I am always looking for a way off the road etc.. just to make sure if there was a problem that I wouldn't hurt anyone. Dual circuit is a very important mod for these trucks. I am still interested as well.

 

[fleetmech]

Even with my rig working very well, I am always leery of the breaks. I am always looking for a way off the road etc.. just to make sure if there was a problem that I wouldn't hurt anyone. Dual circuit is a very important mod for these trucks. I am still interested as well.

Same here, and that leery-ness is one reason I dont use this truck as much as I otherwise would.

I intend to jump back into it once the weather warms up a bit, and I'll post up what i end up installing.

FWIW, I chatted with a guy at a show last year who had installed a rock crawler style pinion brake on his deuce, with a 4th pedal and independent master under the dash. According to him, it stopped the truck just fine. I know its something weve discussed on here before; that was the first time ive seen it actually done on a full size m35.

 

[5tonpuller]

Every year I inspect the brake system on the truck. 17 ton truck do not stop well with no brakes. If i even see a damp spot it gets fixed. ( got this thing about my ass puckering trying to stop). The hand brake is almost worthless.

Been looking at older truck in the junk yards that have hyd. brakes. Maybe trade parts? ( all new ones are air now) Even found what they call hyd. circuit breakers. Needs some pressure on both ends to let fluid pass. No pressure on one end it shuts off the flow.

At one time some one had a parts list and had a bracket set up for the 5 ton for the master cylinder and extra booster and a proportioning valve (of course can't find the post now) Of course it all is a mod. from the orig. If something (god forbid) did happen, would the court see it as a non factory mod. Then it could get interesting.

My 0.05 worth.