dual wheel cylinders

[jesusgatos]

I was just crawling around under my new M103A3 trailer yesterday, and noticed that there appear to be two hydraulic wheel cylinders inside each drum, instead of the S-cams used on our deuces. Why are the trailers set up like this? Are those brakes self-adjusting? Are they more/less powerful than deuce brakes? Can those brakes be swapped over onto a deuce?

 

[whyme]

a more interesting quesion to me would be can they be modified to function while only using one of the two cylinders? this could be a solution to providing a redundent breaking system on the trucks, well at least one part of the solution.

 

[jesusgatos]

Maybe I'm not following you, but I don't think that'd work too well if pressure wasn't equally distributed between the two wheel cylinders. I think you'd be much better off dividing axles into different circuits. I'm just wondering if this might offer any increase in braking performance.

 

[jasonjc]

The deuce does not use "S-cam's".

 

[southdave]

i believe most of the parts are interchangeable, I have never been into 105 trailer or my duece yet, although I am staying at holiday Inn express. But I do have have 40 wheel cylinders and pads that list 105s and m35a2c, wheen I looked up the nsn

 

[jesusgatos]

Oh. My bad. Am I thinking of air brake parts? I meant the adjustable pivots (on cams) at the bottom. I've rebuilt the brakes on Mah Deuce, but haven't ripped into the trailer yet.

 

[jesusgatos]

i believe most of the parts are interchangeable

Cool, but WHY do the trailers use dual wheel cylinders? More braking power?

 

[southdave]

maybe somthing with adjustment?? I am out on limb so...

 

[Capt.Marion]

Maybe one's for the hand brake and the other's for the trailer brakes (actuated by air from the towing vehicle)?

 

[6X6 ALL THE WAY]

I was thinking the same thing a week ago. If you had two wheel cylinders, that should give you more braking force. Since the top and bottom of the pads are being pushed out. As long as the master cylinder could put out enough volume to feed four more wheel cylinders. I was thinking of trying this out on my bobber that im building

 

[RRAY670]

1971 general products M35a2 w/w (paid for but not yet in my driveway, EUC waiting since 4/25)


Was yours on event 5132 in ft drum? I'm still waiting for mine too.

 

[Crazyguyla]

IIRC, been about 8 yrs since I looked at trailer brakes, the daul cyl setup works like this. One cyl is for regular braking, the secon cyl is for the emergency brakes(loss of air pressure). I could be wrong. Someone should look in the TM and read why there is two wheel cyl.

 

[tm america]

It would give more braking power depending on the size of the cylinders.There would still be some kind of adjustments in there .Drum brakes are not self adjusting due to the way the return springs pull the shoes back in . The return springs would pull the shoes in to far to have any brakes if there wasnt some kind of stop-adjustment....disc brakes are self adjusting as there are no return springs to move the pistons back in the just rely on the lack of hydraulic pressure letting the pistons go in just enough to let things free up.

 

[jesusgatos]

Maybe one's for the hand brake and the other's for the trailer brakes (actuated by air from the towing vehicle)?

IIRC, been about 8 yrs since I looked at trailer brakes, the daul cyl setup works like this. One cyl is for regular braking, the secon cyl is for the emergency brakes(loss of air pressure). I could be wrong. Someone should look in the TM and read why there is two wheel cyl.

No, all four wheel cylinders (two per drum) are on the same circuit. The hand brakes are cable-operated.

 

[tm america]

dual cylinder setups work like this.. Both cylinders are applied at the same time from fluid supplied from the same source.They are not run separately .One cylinder is at the top where there is one normally the other is located at the bottom in place of the anchoring pin.

 

[gringeltaube]

i believe most of the parts are interchangeable, I have never been into 105 trailer or my duece yet, although I am staying at holiday Inn express. But I do have have 40 wheel cylinders and pads that list 105s and m35a2c, wheen I looked up the nsn

That is correct for the M105A1 which only takes one cylinder per wheel. The A2 versions use totally different shoes/ cylinders and other parts and 2 cylinders per wheel.
See both styles in TM 9-2320-213-14&P, section II, fig. 10 and 11.


G.

 

[jesusgatos]

So G, what do you think about the possibility of swapping the dual-cylinder A2 brakes over to a deuce?

 

[gimpyrobb]

Are you having THAT much trouble stopping? Once I adjust my breaks, I can lock them if I choose. The other considereation would be brake fade from too much heat. Do you think the trailers use two whl. cyls. as a back-up if one of the pistons siezes up? I doubt the trailers saw as much PMCS as the trucks. Just a W.A.G!

 

[jesusgatos]

Maybe one's for the hand brake and the other's for the trailer brakes (actuated by air from the towing vehicle)?

IIRC, been about 8 yrs since I looked at trailer brakes, the daul cyl setup works like this. One cyl is for regular braking, the secon cyl is for the emergency brakes(loss of air pressure). I could be wrong. Someone should look in the TM and read why there is two wheel cyl.

No, no trouble stopping. Especially after installing all new wheel cylinders and adjusting the brakes. But better is better, and if I can swap some parts around to improve braking performance, I will.

 

[rosco]

When dual cylinders are used - one for each shoe, performance is increased. Trailing shoes, on single cylinder systems, just don't do much. Its the leading shoe, that tends to bite into the drum, aided by the direction of rotation, that does most of the work. Noting that: some single cylinder systems on vehicles will use two different types of lining. A softer grade for the trailing shoe, so it will bite into the drum better, so it will match the work of the front shoe. Another example is the M37. The single/double acting cylinder, has two different bore sizes. The larger bore goes to the trailing shoe, giving more force to make it bite in and do more work. Hence it very important to get them installed correctly.

The later trailers are just using a more efficient system by using dual cylinders/one for each shoe! When I grew up using single system brake systems on vehicles, we didn't know they were dangerous and that we needed dual brake systems. Some how, we managed!

Lee in Alaska