how to cut apart a spring brake
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  1. #1
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    Do you guys have any ideas how I can safely cut apart a loaded truck spring brake?

    Joe

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    There should be a large nut on the end of the can to compress the spring, it is used to release the brake to tow a disabled truck.

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    Make sure the vehicle is blocked so it won't roll, surprising how many people forget this step.
    The safest way is cage the spring. To do this you need to locate the caging tool, a caging tool is a threaded rod about 9/16" dia. 8" long with a nut on one end and a "T" on the other. It should be in a round slot on the side of the air chamber. If not check the other chambers for one. You insert the "T" end into the hole in the end of the air chamber and turn it 90* and pull back out. You will feel it enter a slot. Then you tighten the nut and compress the spring. Then you can take the clamp bolts loose on the side of the chamber. Always be careful while doing this, I have seen the tool or plate in the chamber fail. Don't get in a direct line, the spring has 2000lb plus pressure.
    I have had to take an O/A torch and burn a hole in the side and cut the spring coils as a last resort.

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    Joe, go to arvinmeritor.com and/or wabeco, I think there are some tech sheets available there.
    ATB,
    Croz

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    Be extremely careful when disassembling brake springs. The spring is strong enough to push the actuating rod right through your body. When I worked on trucks, the company I worked for would not overhaul brake "cans", only replace them because of this danger.

    Chris

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    a type 30/30 brake can has 3500#s of force on the spring, so you are messing with dynamite

    it is one of those things that if you have to ask, you should not be doing it, period

    people have been mamed and killed by these things

    most are not serviceable these days, they made the spring section crimped together to save some people from themselves.

    you only have to have one of these bad boys blow up on you once to know what i mean, i nearly lost a hand just trying to use the caging tool when the corroded key slot let go when i was approaching the fully caged position. it blew apart the rear of the can, and went out the back of the truck nearly 200 feet.

    i knew not to cage one with my body behind it, i was using my off hand to hold the outer edge of the can for leverage while i cranked on the wrench.

    if you need to cage one to replace it ok, do it, just stay off to the side of it.. if you want to take it apart, presumably to recover the aluminum castings, do it in a press with proper tooling to control the damn thing.

    these are not a forgiving animal.

    bob g

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    I agree with everyone here on how it's done & the safety issues. Last service job I worked (several years ago) Our policy with them was remove from truck & straight to the scrap dumpster. Even back then replacements didn't cost much more to the customer than the parts & labor to rebuild one.

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    I have to make a machine or come up with a process to cut the brakes apart for a spring brake manufacturer so they can inspect warranty returns. The brakes will already be off the vehicle. I can't do any damage to the internals of the brake.

    Joe

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    It says to me: "clamp it in a tooling fixture/nest then apply load with an overpowering air cylinder with a mechanical backup latch in case air pressure is lost."

    It could also be a safety check valve which traps air in the cylinder, some options are available from Ross Controls.

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    You are messing with death, here You either need to have a qualified shop do this, or at least find a way to get the unit into a press and contain the thing safely.

    A few things I remember. One of the guys I used to work with at a heavy parts store used to rebuild these in a press in the back room. There used to be a piece of broken can jammed permanently into the door jam nearby as a reminder

    The caging tool, as I remember, is NOT designed for dissassembly. It's designed to release the brake in case of air failure so you can remove the can. If you DO try to use the caging tool, be aware that there is VERY little that engages the T end. If either the bolt or the part inside that receives the caging bolt is damaged, you could be in for a nasty surprise.


    One problem with these, is that water can get inside the vented side of the diaphragm, and corrode the can from inside out. The outside of the can may appear to be normal, and ready to explode.

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    The device I proposed above is one of those applications where you'd want to select hydraulic hose for air lines as you can't afford a bursted line.....

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    Several have told you about the dangers, so I'll think about the machine.

    I've seen both steel and aluminum cans, so the machine should be able to cut both. I would think about a cold saw. A couple of shims may need to go into the kerf to keep it from collapsing.

    As to the mechanism, how about mounting the can on a rotary spindle, like a rotisserie. One end would be fixed, the other end a hydraulic cylinder. Since you are only doing one company's product, make dedicated holding units for each end for each type of brake can. I think about 6 types will cover almost all types.

    The mechanism should be mounted in a stout box. Full automation with safety interlocks to insure the door is shut.

    All this may be more money than the mfg. wants to spend, but there is no way I would touch this for something manually operated.

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    440RR is exactly right about the caging tool, it's meant to cage the spring enough to get the pin out of the slack adjuster, not disassemble the can. Look at how scrawny the little tits on the end of the tool are. New 3030's aren't much money, we bought them by the pallet and never opened one up.

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    I'm not sure why they are looking to do a warranty inspection, there are usually two areas that fail in the parking side, the diaphragm or the shaft O ring.
    I seem to remember some of them were crimped to prevent disassembly. Are these the kind that you are working with? Having to cut the crimp will change things.
    Making a machine to disassemble one would depend on what type you are working with and how fast they want to do it. I would use a porta-power in a fixture to make it simple and a hydraulic power unit for speed. Also a safety cage for releasing it.
    I would also look at liability issues with building such a machine.
    I have changed or disassembled/repaired hundreds of them in the past. It's kind of like picking up a rattlesnake, if you don't know what you are doing it can bite you.

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    Tell ya one thing, make sure that machine is 110% enclosed during every operation between loading and removing the completely decompressed assembly!

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    tell the cheap bastards that want the warranty inspections to send em back to mexico or whereever they come from.

    none that i am aware of are made in this country anymore.

    if you are cutting apart the crimped variety which are the most common today, you are risking death or serious injury.

    i tried to explain this in an earlier post.

    i have worked with these can's routinely for over 32 years, an i know the hazzards.

    screw with them and you "WILL" get bit, it is just a matter of time..

    there is nothing inside those can's that the manufacture needs to see, he can readily see if it has a broken spring, or if it has a faulty shaft seal, all can be done with simple air connections..

    this is insanity,

    oh well if you persist, then at least buy enough insurance to fix your body or in a worse case bury you.

    this is tantamount to looking down the barrel of a loaded shotgun, would you do that?

    you have to wonder why they are looking outside their own resources to get this type of inspection done.


    bob g

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    gbent,

    Thanks for your help. That's about where we are at so far. We have an enclosure that completely contains the piece. We have the can mounted to a rotary table. A nylon cylinder is pneumatically actuated to come down from the top and capture the top of the spring brake and only allows it to move about 1/4" when it cuts through. We have tried an abrasive wheel and it works but makes too much mess. This thing is going to be used in an R&D facility so it has to be fairly clean. We also tried using a couple of slides with a parting tool but as you already noted, when it cuts through one side it cocks and wedges the tool. I was thinking of trying a spindle with a jewelers saw. But your idea of adding shims may be the trick. I will give that some more thought. The only thing with that is the technician will have to open the door and reach in to place the shims in the cut. I will have to program in some kind of stop after the saw cuts through far enough to put the shims in place. I was hoping to make this a situation where you would load the part, hit the start button, and when it was done cutting you would release the cylinder that contains the top half of the can and then open the door when the spring is completely free of energy.

    Joe

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    Joe, I think I would change to hydraulics. A hydraulic cylinder can take a load without moving, where the air will give with a load applied. The hydraulics perhaps could be locked into position without squeezing the can, and might be able to overcome binding the kerf.

  22. #19
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    gbent,

    Hydraulics - yeah I thought of that but I already had a pneumatic cylinder laying around and was trying to keep costs down a bit - you know the story. But it may be one of those situations where I may as well do it sooner rather than later if it is the only solution. Thanks for your help. I am going to tweak our existing design a bit and see if we can get it to the point where we (the customer and I) are satisfied. If not - hydraulics it is!

    Thanks,

    Joe

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    Here's an idea. What does the machine look like that ASSEMBLES these parts? Why not make an identical machine that cuts instead of crimps? Somewhere in the world is a machine that safely puts these things together, why not just reverse engineer the process?

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