Split Brakes

[stumps]

I have read this thread with great interest, as I would like to have the additional safety of a dual circuit system, but as no one has brought this up yet, I guess I will.

A lot of different ideas have been proposed in the last 8 pages....... but why do you think the manufacturer (AM General) or the military (they do have a hand in this sort of thing-they could simply tell the people bidding on a contract "we want it THIS way") went the way they did?

All the proposals here were at their disposal as well....... so why do you think they went the way they did? If they could have done it this easily with off the shelf parts, they could lower the price of the bid and have better chances of winning it or keep the price the same and make more profit.

But for some reason, they chose to do it the way they did.

I'd really like someone to talk to a brake systems engineer @ AM G and ask them "Why this way, with the dual airpacks and such?". I'll bet he tells us something that we have not considered.

I'm not trying to flame you guys and I can see a lot of you have put a lot of time and research into this and I am sure everyone (myself included) appreciates it.

First, AM G had nothing to do with designing the deuces, or even the M35A2's. The Bendix braking system was designed, and specified for the deuces long before AM G came on the scene.

Single circuit brakes were the standard in the automotive world when the deuces were designed. Compared to the mechanical lever brakes that preceded them, they are a marvel of safety and design excellence.

The truck designers looked at things like putting cord in the double walled brake hoses, and using tern plating inside and outside of the tempered steel brake lines, and using a double flare joint, and using all plated steel fittings, and using rivets to hold the brake linings on the brake shoes, and using solid molded rubber cup pistons backed with tight tolerance aluminum cup plungers as being the necessary overbuilding to make the system very safe.

There are a lot of single point failures in an automobile, a single circuit brake system isn't really one of them. It takes multiple failures to make the system fail. Things like the plating on the tubing needs to rust through unnoticed, and the tempered steel tube needs to rust through to make a failure. Or, the rubber hose needs to lose its outer covering, the dacron outer reinforcement, the middle rubber lining, or the inner dacron reinforcement and the inner rubber lining to fail....

Also, considering the speeds and gearing the trucks were expected to use, most of the time, brakes aren't all that essential. Put your truck in low range, and let me know what happens when you take your foot off of the pedal after running full throttle. It lumbers down to a crawl PDQ.

I have used my farm tractor for 20 years with ineffective brakes, and never missed them. I turn the throttle down, and the tractor slows to a crawl.

Please don't take anything I have said to mean that I am advocating running without fully functioning service brakes! I am advocating paying close attention to the brakes you have. If you find any rust on a line, replace it. If some joint is seeping, find out why, and fix it. If the rubber hoses are cracked, replace them. If a wheel cylinder leaks, or your fluid level drops in the MC, find out why and fix it! CHECK YOUR BRAKES! It says so right on the label on the dash of your truck! Follow that rule, and your likelihood of having a brake failure with the deuce's single circuit brake system is insignificant. It already has a great deal of redundancy built in, you just may be unaware of it.

-Chuck

 

[clinto]

First, AM G had nothing to do with designing the deuces, or even the M35A2's. The Bendix braking system was designed, and specified for the deuces long before AM G came on the scene.

Single circuit brakes were the standard in the automotive world when the deuces were designed. Compared to the mechanical lever brakes that preceded them, they are a marvel of safety and design excellence.

The truck designers looked at things like putting cord in the double walled brake hoses, and using tern plating inside and outside of the tempered steel brake lines, and using a double flare joint, and using all plated steel fittings, and using rivets to hold the brake linings on the brake shoes, and using solid molded rubber cup pistons backed with tight tolerance aluminum cup plungers as being the necessary overbuilding to make the system very safe.

There are a lot of single point failures in an automobile, a single circuit brake system isn't really one of them. It takes multiple failures to make the system fail. Things like the plating on the tubing needs to rust through unnoticed, and the tempered steel tube needs to rust through to make a failure. Or, the rubber hose needs to lose its outer covering, the dacron outer reinforcement, the middle rubber lining, or the inner dacron reinforcement and the inner rubber lining to fail....

Also, considering the speeds and gearing the trucks were expected to use, most of the time, brakes aren't all that essential. Put your truck in low range, and let me know what happens when you take your foot off of the pedal after running full throttle. It lumbers down to a crawl PDQ.

I have used my farm tractor for 20 years with ineffective brakes, and never missed them. I turn the throttle down, and the tractor slows to a crawl.

Please don't take anything I have said to mean that I am advocating running without fully functioning service brakes! I am advocating paying close attention to the brakes you have. If you find any rust on a line, replace it. If some joint is seeping, find out why, and fix it. If the rubber hoses are cracked, replace them. If a wheel cylinder leaks, or your fluid level drops in the MC, find out why and fix it! CHECK YOUR BRAKES! It says so right on the label on the dash of your truck! Follow that rule, and your likelihood of having a brake failure with the deuce's single circuit brake system is insignificant. It already has a great deal of redundancy built in, you just are unaware of it.

-Chuck

Chuck,


I was not referring to the original single circuit system. I would have thought my post made that clear when I said "I'd really like someone to talk to a brake systems engineer @ AM G and ask them "Why this way, with the dual airpacks and such?". I'll bet he tells us something that we have not considered.".

I was referring to the dual circuit system that appeared in 1987. By 1987, the only manufacturer doing M44 stuff was AM General.

So let me rephrase my original post this way: "Everyone here is who is trying to come up with a cheap and easy way to get dual circuit brakes, please consider that all of your cheap and easy methods were at AM G's disposal when then introduced their dual circuit system in 1987 and for some reason they chose to go with their more complex and expensive method of dual airpacks and master cylinder. Why did they do that?"

My post had nothing to do with defending or degrading the single circuit brake systems or the Deuce's original braking system.

 

[stumps]

Hi Clinto,

My, uhmmm, blathering went beyond your original statement into a statement about the suitability, and safety of single circuit brakes in general.

I don't think AM General had much original design in the dual circuit brake system they used in the last deuces. It looks like it is using pretty standard stuff. The dual airpacks was their way of extending the redundancy all the way to the pedal.

How do they split the two circuits? At the obvious front axle/rear axles divide, or are they running 3 WC's per MC? I know, I could look it up, but I suspect it is right on your mind.

If the split is front/rear, then they must have done something to balance the two circuits, as the rear circuit would need twice the travel of the MC piston to achieve full braking as the front circuit.... otherwise, the front brakes would lock up before the rear brakes were fully applied.

-Chuck

 

[73m819]

does anybody have a dual circuit layout diagram

 

[hndrsonj]

The TM for the conversion is in the resources section. CSI says they can order the parts from AMG but it will be spendy.

 

[DanMartin]

does anybody have a dual circuit layout diagram

See post #18 in this thread....I posted that diagram already.

Here's the direct link:
http://www.steelsoldiers.com/attach...8795278-split-brake-system-splitbrakes_sm.jpg

 

[Chinookpilot77]

I would love to see some pictures of the linkage for the dual mc set up. I am trying to weigh all my options, and it seems like the linkage could be a nightmare trying to set up?

Anyone have pics of this?

 

[Crazyguyla]

Hi Clinto,

My, uhmmm, blathering went beyond your original statement into a statement about the suitability, and safety of single circuit brakes in general.

I don't think AM General had much original design in the dual circuit brake system they used in the last deuces. It looks like it is using pretty standard stuff. The dual airpacks was their way of extending the redundancy all the way to the pedal.

How do they split the two circuits? At the obvious front axle/rear axles divide, or are they running 3 WC's per MC? I know, I could look it up, but I suspect it is right on your mind.

If the split is front/rear, then they must have done something to balance the two circuits, as the rear circuit would need twice the travel of the MC piston to achieve full braking as the front circuit.... otherwise, the front brakes would lock up before the rear brakes were fully applied.

-Chuck

Chuck,
There's a proportioning valve between the front and rear brake systems, just like split systems on automobiles. It hasn't even been discussed in this whole thread.

There are pros and cons to the dual system that later deuces were equipped with. If I was going to do the dual brake setup, i would mount the reservoir separate from master cylinder. The way the dual system was designed for A2's, the reservoir is under the floor and harder to fill than to normal single circuit master cylinder. The A3's had a remote reservoir for it's dual brake system. I like the simplicity of my single brake system and the extra vigilance needed to keep it working. My brakes are completely shot and are getting totally rebuilt.

...The truck designers looked at things like putting cord in the double walled brake hoses, and using tern plating inside and outside of the tempered steel brake lines, and using a double flare joint, and using all plated steel fittings, and using rivets to hold the brake linings on the brake shoes, and using solid molded rubber cup pistons backed with tight tolerance aluminum cup plungers as being the necessary overbuilding to make the system very safe.

There are a lot of single point failures in an automobile, a single circuit brake system isn't really one of them. It takes multiple failures to make the system fail. Things like the plating on the tubing needs to rust through unnoticed, and the tempered steel tube needs to rust through to make a failure. Or, the rubber hose needs to lose its outer covering, the dacron outer reinforcement, the middle rubber lining, or the inner dacron reinforcement and the inner rubber lining to fail....

All the above have failed in my brakes. They were totally rusted out when I bought the deuce. All my lines, MC, and booster have been replaced;just have to replace all those pesky wheel cylinders.

Marcus

 

[hogtruck]

Some pics of dual MC and linkage.

 

[RangerDave]

Since I am going to be rebuilding my whole system, I have been reading this with great interest...
A thought had occurred to me that the solution to the single MC problem of system failure was a newly invented hydraulic line spill check poppet.... It was designed for hydraulic line failures in the mining and forestry industries where a 70 GPM pump could puke out all the hydraulic fluid in a mere matter of moments..... Place one on each axle group and isolate the problem without system failure!!! But alas - upon closer inspection, pressure opens and closes the check valve to allow flow, the spring provides 100psi back pressure so that with the control lever in neutral, hydraulic fluid doesn't oooze out of the closed circuit...

Oh well, just trying to think out of the box... there is another safety hydraulic check valve used on man lifts and outriggers where if the hydraulic cylinder looses pressure, it locks in place... I must see how that works.

 

[mikew]

A valid part number for the master cylinder is: Bendix 11999 or Raybestos MC39577

This crosses to a NAPA TS108038, TS108002 and UP39577.

This is a dual circuit master cylinder with 1 3/4" bore used on Ford B600 buses in 1984-1985, about $150.

Does anyone know the bore diameter of the M35A2 single circuit master cylinder?

 

[gringeltaube]

.................................bore diameter of the m35a2 single circuit master cylinder?

1-3/4"

g.

 

[oifvet]

what we need is the casting #, not the part number.

I just removed the master cylinder (cleaned and replaced it) on my 1989 (USAF) M35A2C... (A dual-circuit brake truck)...

The "casting" number on the side of the master cylinder itself was 2230600 and also read 1.75 BORE on the opposite side.

The reservoir was 2232692 and the adaptor located between the reservoir and MC was 2232608. I believe these are Bendix numbers. I "Googled" and found the items were available, unlike the "obsolete" Bendix numbers that I was working with from other sources.