dual brakes or split brakes on an M39 5-ton

[Robo McDuff]

Did anybody actually installed a split brake system or dual brake system on a 5-ton M-39?

I see a lot of stuff on the topic, but focusing on the Deuce. I am looking for stuff on the M-39 series, preferably the M5x-A2s. Not the 809 and higher, not the Deuces, just M39.

I am wondering if anybody ever installed a second identical master cylinder and this air stuff connected to it. One set services the rear rear axle and 1 front brake, the other one the mid-rear and the the other front brake.

If a system fails and you have to do a emergency brake on only one system, you might get a drag to one direction. However, that is still better than having no brakes at all.

 

[Robo McDuff]

No answers in over a week, so I'll bump this one up again. Nobody?

 

[dozer1]

No takers yet on this thread? I too was curious if someone did some 5 ton dual circuit work. Nothing turned up in a search. Maybe you will be the first to do this?

 

[73m819]

I brought this up in the deuce brake thread, no answers,

I have been giving this some thought for a bit for the 36000+lb 819, I really would not like to not be able to stop if needed after coming in for a landing, using Honda's as a stop wall may scratch the paint on the front axle.

I would do front axle and one wheel of number two axle, the other circuit the other number two axle wheel and the rear axle, I think this will give you more even braking, Along with the second air pac, I was thinking of a duel MC from a mid 70s ford medium dump truck or a int. school bus, this would be from just before thay went to air, I would also add two more air tanks with one-way valves as reserve air for emg. braking only

 

[Robo McDuff]

I brought this up in the deuce brake thread, no answers,

I have been giving this some thought for a bit for the 36000+lb 819, I really would not like to not be able to stop if needed after coming in for a landing, using Honda's as a stop wall may scratch the paint on the front axle.

I would do front axle and one wheel of number two axle, the other circuit the other number two axle wheel and the rear axle, I think this will give you more even braking, Along with the second air pac, I was thinking of a duel MC from a mid 70s ford medium dump truck or a int. school bus, this would be from just before thay went to air, I would also add two more air tanks with one-way valves as reserve air for emg. braking only

Interesting way of dividing the power, putting the single one in the middle. We should really work this out and try this out.

Ideally would be if the front brakes had two cylinders per hub, one up one down so each brake shoe would brake in the same turning direction. Then, dual brakes would really be a piece of cake: One rear axle and the front top cylinders. Second rear axle and the front down cylinders.

 

[BadMastard]

This is a fascinating idea. Ok, with most braking systems the primary stopping power is the front brakes, I think about 70/30. What if you took the two circuits and put the front on one, and both backs on the other? You'd lose capacity, but it would ensure even braking?

 

[73m819]

But if done with front and the other circuit to the rears, If the rears take a dump, I dont think the fronts on a 5t are enough to stop in an emergency, on a 4x4, yes one circuit front, one rear, on a 6x6, I think front and one #2 axle wheel on a circuit and on the other, the other #2 wheel and the other axle would be needed to stop in an emg.

 

[BadMastard]

Good point. I haven't worked with a lot of dual rear axles so there may be quite a bit more stopping power there than other brakes. Although I think they have to be weight loaded for that to work. My guess is the front load up on an empty truck. I think the easy way to tell is do the front brakes using the same drum system as the back wear out first? 2 to 1? I haven't driven my deuce enough to say? anyone?

 

[Robo McDuff]

Does any of the M39 axles ever had a dual brake cylinder system? Now, there is only one brake cylinder mounted at the top of the brake plate, with the brake shoes turning around a fixed point at the bottom part. With a dual cylinder system, each brake shoe is operated by a separate cylinder.

 

[73m819]

Not that I know

"With a dual cylinder system, each brake shoe is operated by a separate cylinder. " with this set up, there is ONE flex line and a hard line to the other cylinder, If you want to split this up, It would take TWO flex lines, if you are going to ripe one flex line out, you will get the other which would mean NO brakes

 

[Robo McDuff]

Ron, your way of front axle + 1 mid and rear axle + 1 mid seems simpler and cause less drag to one side after one system fails then my way of rear axle + 1 front and mid axle + 1 front

Two points on your way.

1) Did not have time to read all threads and manuals on this yet, so I will ask it: do you need to balance the power of braking between front and rear brakes? IF so, how to solve that with your option?

2) The front axle has that sprag system. Does that come into the picture as possible problem in this set-up? I would think not since it does not now, but in that dual system, not sure if it would influence something if you brake with engine still engaged and one system fails.

 

[FireFighterHill]

I think the safest setup would be front on one circuit and both rear axles on the other circuit.

I wonder if a proportioning valve would be a good idea. Id think it would be better for the rears to lock up before the fronts, thus allowing you to steer instead of skid.

 

[73m819]

I think the safest setup would be front on one circuit and both rear axles on the other circuit.

I wonder if a proportioning valve would be a good idea. Id think it would be better for the rears to lock up before the fronts, thus allowing you to steer instead of skid.

The only problem with this set up is if you should LOOSE the rear circuit, I don't believe that the FRONT only brakes will stop a 5t at speed very well, the extra wheel from the #2 axle would be a help (better then nothing)

The ideal setup would be a CHEAP air conversion because a 5t really needs all wheels to stop

One other thought is air on the rears, hyd. on the front ( though if you are going to do the rears why not the front) my 39 autocar had a air rear axle that somebody installed before my ownership, the truck had vac.hyd. fronts, I could lock up both axles if needed

The sprag should have no affect on the brakeing, You could use a proportioning valve if you needed to balance the system (make an adjustable valve so you could fine tune the system)

 

[Robo McDuff]

.......The ideal setup would be a CHEAP air conversion because a 5t really needs all wheels to stop.........

Anybody did that with an M39 5-ton?

I think there are no cheap conversions. Splitting the existing system would be easier and cheaper. If you would also install two fluid reservoirs in the cabin you can equip them with a warning signal that warns when you are loosing liquid. Thing is, normally both systems should work. Once one goes, the thing is to be warned of it and trying to get home SAFE: you and everybody else!

In Europe, a hydraulics to air conversion would be considered a mayor change to the vehicle and almost certainly a trip to the DoT. Not sure, but if you then have a stickler prick, you might end up with them saying that, because of this modification, the truck actually is of a newer built and has to fulfill ALL the rules for newer trucks. You would not want to open that can if you can avoid it.

 

[73m819]

Another thought, someone posted a pic of a HYD FUSE for air craft, it senses pressure loss and shuts down the line to prevent fluid loss, this was brought up in the deuce brake thread, why could this not be incorporated into the split brake 5t system conversion, a FUSE for each wheel, so other then a major line loss, you would ONLY loose the breaking of one wheel if you lost a wheel cylinder. A wrecker or loaded dump or for that matter any loaded 5t needs All the breaking it can get.

 

[Robo McDuff]

Another thought, someone posted a pic of a HYD FUSE for air craft, it senses pressure loss and shuts down the line to prevent fluid loss, this was brought up in the deuce brake thread, why could this not be incorporated into the split brake 5t system conversion, a FUSE for each wheel, so other then a major line loss, you would ONLY loose the breaking of one wheel if you lost a wheel cylinder. A wrecker or loaded dump or for that matter any loaded 5t needs All the breaking it can get.

That would be great. If it exists for a reasonable price, I would install it immediately.

Ron, you know I don't have my truck next outside my door, so I cannot just pop out to look. Is there actually enough room next to the existing MC and air stuff to put a duplicate there?

Why using a second set of a different car? Would it not work better just to put an exact copy next to the existing stuff to duplicate the system?

 

[73m819]

That would be great. If it exists for a reasonable price, I would install it immediately.

Ron, you know I don't have my truck next outside my door, so I cannot just pop out to look. Is there actually enough room next to the existing MC and air stuff to put a duplicate there?

Why using a second set of a different car? Would it not work better just to put an exact copy next to the existing stuff to duplicate the system?

yes, but a duel mc

 

[Robo McDuff]

For a moment forgot about dual MCs, you're right, makes more sense.

As to distribution, what about both left rear wheel and right front on one circuit and both right rear wheels and front left on the other? Would that give better performance - read: less drag to one side (after a circuit fails) than the other options or is it 6 of one and a half dozen of the other?

 

[73m819]

For a moment forgot about dual MCs, you're right, makes more sense.

As to distribution, what about both left rear wheel and right front on one circuit and both right rear wheels and front left on the other? Would that give better performance - read: less drag to one side (after a circuit fails) than the other options or is it 6 of one and a half dozen of the other?

ON a WET road, you just put your self into a SPIN with a failure to one circut, a balanced system side to side is needed to keep the stopping as straight as possible

 

[Robo McDuff]

The time is coming that we start work on the brakes and steering and certainly after hearing several horror and almost horror stories with failing brakes, this is the one change I want to make if possible.

We are over a year further since the last post. Any new ideas on this?

Anybody finally did this for a 5-ton?