Split brake system

[FireFighterHill]

Another question I forgot to ask. When the brakes do fail on a M35 do they fail open or closed (locked)? I know on a lot of military trailers with airbrakes the air supplied keeps the brakes open so you can tow it and they fail in the closed (brakes on) position, so no air and you're just dragging the trailer and smoking the wheels.

Thanks

they fail OPEN. Correct me if im wrong guys but I believe you still have SOME braking power even if you lose air pressure? but if the hydraulic system has a leak you have no braking power.

 

[blisters13]

If you lose air, you still have braking, but with difficulty. If you lose a hydraulic assembly, you lose all service braking.

These brakes will not lockup if air or hydraulic pressure is lost.

I have been following this and note that the military didn't upgrade the vast majority of the M35's out there, and it was probably because 1) the trucks were getting to the end of their design life, so upgrading wasn't financially feasible and 2) these trucks probably had the "soft" parts replaced on a timed basis, so the brakes were reliable.

We are (or rather for me, WILL BE) driving old, heavy trucks which need to have dependable brakes and steering. The safest thing to do is to replace all the soft parts such as all hoses and cylinder cups; this can be accomplished by rebuilding cylinders or installing new.

The dual-circuit system is better, and if you live in a high-traffic area such as Southern California or any city, it would be the smarter thing to do.

The hydraulic fuse sounds great, but it could never "set" for a false failure, as then you would lose brakes to whichever circuit it was in. I think there is a distinct probability that the DOT would not allow the installation of "fuses" in braking systems (someone verify/deny?).

What I have NOT seen so far is anyone posting the modification kit number and where to buy it. So I guess that's not an option? Anyone??

 

[clinto]

What I have NOT seen so far is anyone posting the modification kit number and where to buy it. So I guess that's not an option? Anyone??

There are several threads that detail the parts, procurement and procedure for doing a split circuit system conversion.

So a search, try "split circuit" or "dual circuit" in the deuce and deuce modification forums.

The issue is cost and parts availability.

 

[Kohburn]

On a side note I replace the front brake lines with braided stainless lines.

i've done this on other cars, is there a kit with the right hoses and fittings? or did you just order the lengths and fittings yourself?

 

[jesusgatos]

Where did you get those braided stainless hoses?

 

[Trango]

By the way, I have a full, commercial air over hydraulic system off a Hino COE, which consists of 2 cylinders and reservoirs, along with an air treadle/pedal. This would allow a relatively easy conversion to a pure air/hydraulic system. This is akin to what Tom "Fastest M35" did on an old truck years ago, and he told me that he was really quite pleased. Paid $300 and had to pull it off the truck myself, I'd let it go for $160 + shipping. I don't really want to move it to the new house.

Let me know.

Bob

 

[Robo McDuff]

........

I was also thinking of something else...please someone who has a lot more experience with MV's and MV trailers tell my if I've lost my marbles or if it could conceivably work?

Most of the trailers I've seen have an air braking system used through the glad hand couplers at the rear of the truck. ........ would it be possible to use the service brake master cylinder from a trailer, along with it's air/pressure regulator (whatever it uses) and tap into the service air line going to the rear glad hand coupler. That way when you apply the brakes, it applies air to the new MC/regulator set-up and applies brakes to whatever axle you have that MC hooked into???

Sounds like an interesting idea (from October 8, 2009, a year ago) but did not see any reply on it. Since the thread is jumpstarted again, tought I bump this as well. Any thoughts on this or sombody did this?

 

[jesusgatos]

Would like to know more about this too. Sounds interesting. I'm leaning towards a hydro-max conversion.

 

[jaxsof]

This is my first time on this thread. Lots of good ideas. If you can get an equal displacement MC, and instead of splitting front/tandems, go LF-RM-FR and RF-LM-RR. you successfully split equally, and if you get a single failure, the braking effort is almost-sorta equal side to side.

Whatcha think?

 

[jesusgatos]

Personally, I'm not too wild about the idea of asymmetrical braking.

 

[FireFighterHill]

i've done this on other cars, is there a kit with the right hoses and fittings? or did you just order the lengths and fittings yourself?

Where did you get those braided stainless hoses?

I went to a local company the specializes in hose ans tubing for industrial application http://www.amazonhose.com/. I took in the old hose and they replicated it exactly, except braided stainless instead of rubber. It didn't add much to the overall cost. It was a little under 60 for both front lines.

 

[Kohburn]

I'll have to look at the fittings on the end of a set of hoses - I know i can order all the different types of fittings and hose to length from summitracing

 

[jesusgatos]

Yeah, that's what I'd really like to know (without having to disassemble my brakelines) - what size fittings, banjos, etc. I'm made my own flexible brakelines with AN fittings and braided stainless hoses, but for big trucks like these, I'd just have them custom-made. It's really not any more expensive than buying all the individual components to build them yourself and will give me a little extra peace of mind.

 

[Robo McDuff]

Personally, I'm not too wild about the idea of asymmetrical braking.

Jesusgatos, do you refer to the diagonal braking set-up mentioned in Jaxsof's post?

Actually, if I remember my lessons well, this is the way its done on cars, at least was done so on European cars in the 70s and 80s. It's anything but asemetric.

Well, in a way it is, but under normal conditions, the asymetry of each system compensates for the asymetry of the other system. If one system fails completely, the diagonal set-up mostly prevents the truck from lurching to one side. Braking only left front makes the truck go left, but braking right rear at the same time make the truck wanting to go to the right. End result: it stays in the middle of the road more or less.

And as Jaxsof indicated, it's actually the easiest way to do it with the least new parts needed.

 

[jesusgatos]

Under normal braking, I'm sure it would work just fine, and on a four-wheeled vehicle, it would probably be OK in the event that one circuit failed - but with three axles, I can see that becoming a problem. I would just rather retain symmetrical braking by dividing axles.

 

[Kohburn]

Jesusgatos, do you refer to the diagonal braking set-up mentioned in Jaxsof's post?

Actually, if I remember my lessons well, this is the way its done on cars, at least was done so on European cars in the 70s and 80s. It's anything but asemetric.

Well, in a way it is, but under normal conditions, the asymetry of each system compensates for the asymetry of the other system. If one system fails completely, the diagonal set-up mostly prevents the truck from lurching to one side. Braking only left front makes the truck go left, but braking right rear at the same time make the truck wanting to go to the right. End result: it stays in the middle of the road more or less.

And as Jaxsof indicated, it's actually the easiest way to do it with the least new parts needed.

sounds like a good system to me - in America cars are all split front/rear due to the front getting ~60% more fluid than the rear. It's near impossible to do that well on a 3 axle truck so the assymetrical setup sounds like a good balance.

just have to decide on the right dual outlet master cyl. (or rig up a new mechanical linkage for dual m35 master cylinders)

I suppose that if Jesus really wanted all the axles independant he could do multiple master cyls and 3 airpacs with a mechanical linkage to push them all with a single pedal.



what is the bore of the stock master cylinder?

 

[jesusgatos]

Actually, I'm kinda leaning towards a simple dual-circuit system like what was discussed in the HydroMax thread (front axle on one circuit & 2 rear axles on the other circuit).

 

[Kohburn]

I actually really like the idea of a 3 way split - but buying 2 more airpacs isn't money i would part with easily.

I search this site for 2 hours this morning and couldn't find the diameter of the master cylinder bore. Hope someone chimes in with that info.

 

[wdbtchr]

I though long and hard about going with dual circuts( although I was thinking front axle and front tandom on one and rear tandom for the 2nd). But that was just another project to put on the list. I decided to leave it alone until I'm rich and famous since I only operate off road. If I was going to use it on the highway, I might reconsider for safety. I figure if I lose the brakes hauling logs I'll just look for the smaller trees to mow down to stop.

 

[Donald Poppell]

As it has already brought up, Just wanted to add to it

This is out of a 737 Aircraft Tech manual. Kinda thinking this is the way I'm going to look more into.​

Hydraulic Fuses.
[FONT=Arial, sans-serif]These are essentially spring-loaded shuttle valves which close the hydraulic line if they detect a sudden increase in flow such as a burst downstream, thereby preserving hydraulic fluid for the rest of the services. Hydraulic fuses are fitted to the brake system, [/FONT]​