M936 Boom hoist mod to double cable length?

[zebedee]

I think we are getting confused between recovery capability and lift capability.

A big truck down an embankment will not be "lifted", it will be pulled or rolled then pulled - in army speak, that's what the drag winch is for.
Righting a rolled truck ON/Next-to the highway will be lift rolled or drag rolled with the lift line to control the final drop back to all wheels IF you used our trucks.

Civi wreckers do not have drag winches - underlifts, hyd spades, rotator slides take up the space - they have multiple boom winches, often rigged to the stabilisers, that do the 'dragging'.

NOW... Back on topic (for the purposes of the OP)!

 

[Floridianson]

What good is a rotator on supports?

Not like you can lift a car over a rail with it.

You could if you back up to the rail.

 

[Recovry4x4]

If they are only concerned with length, use 3/8.

 

[MOFTA]

Well, it may be all for naught anyway. A Class B wrecker (towing 7001-17,000lbs) has to have a minimum 12T factory rated boom, a Class C wrecker (17,001lbs up) has to have a minimum 25T rated boom. (I think I'm close on those weights.) Both have to have underlift units.

Now we know that the boom hoist on the M936 is rated at 10T max w/3 lines, but what is the actual rating on the boom assy itself?

Back when I first got my M936A2 wrecker, I was able to talk with one of the engineers who worked at Capitol Tool & Die, and he said that this unit was a VERY underrated version of one of their civilian wreckers. I just can't locate any of the documentation on the civilian wreckers they made. Did they actually go by Capitol Tool & Die or were they using another name for the civilian market?

Anybody got any info on them?

 

[73m819]

The military wreckers USE 1/2" wire rope for the hoist line.

You CAN NOT run smaller cable, the drum is a FLUTED drum (not a flat drum but ridges for the wire rope to ride in) these flutes ARE set to support 1/2" w/r under LOAD, if you use a thinner cable, the cable will not be supported so it WILL CRUSH, the thinner the w/r is, the worse the crush.

The cable strength stated is awful high for a SAFE WORKING LOAD for 1/2" w/r, the SWL is BREAKING limit divide by 4, used to be 3.5, this is for WINCHING, it is breaking limit divided by 5 or more for hoisting over 6' from the ground.

A 936 (even just the bed) would NOT make a good civi, on call otr wrecker, a military wrecker has a VERY SPECIAL nitch that it fills, a civi, otr, on call road wrecker is NOT that nitch.

The wrecker beds are made by Garwood

 

[Hawssie]

I am not following the last post #25 when you say "A 936 (even just the bed) would make a good civi, on call otr wrecker, a military wrecker has a VERY SPECIAL nitch that it fills, a civi, otr, on call road wrecker is NOT that nitch." Are you saying that a M936 is not designed to do do civi otr or on call but it would do it good anyway or are you saying its not designed for that kind of work and it should not expect to be able to do it. By the way I am not disagreeing or agreeing just trying to hear what you have to say.

 

[73m819]

I am not following the last post #25 when you say "A 936 (even just the bed) would make a good civi, on call otr wrecker, a military wrecker has a VERY SPECIAL nitch that it fills, a civi, otr, on call road wrecker is NOT that nitch Are you saying that a M936 is not designed to do do civi otr or on call but it would do it good anyway or are you saying." its not designed for that kind of work and it should not expect to be able to do it. By the way I am not disagreeing or agreeing just trying to hear what you have to say.

Yes, a military off road wrecker is designed for that OFF ROAD recovery, motor pool lifting (pulling power packs, ect.) and at one time for loading missiles on launchers. I am not saying that you can not use a tactical military wrecker or even just the bed in the civi world, just that you will be very disappointed, The hyds. are low pressure, slow, the rear drag winch is a very out dated design, the boom is weak, very low lifting capacity for the weight (even just the bed), the m39, m809, and the m939 series make VERY poor lift tow recovery wreckers because of the weight transfer to the rear, causing the steer tires to go lite, they are slow, under powered, HEAVY, VERY HEAVY (even just the bed) for what the wrecker capacity is, expensive to operate, lot of the parts are NOT everyday civi parts, ect..
Think of it this way, Sorta like my 1999 chevy 1500 pu pulling a 105 trailer, yes I can do it BUT the pu and I WILL not like it, a 3/4 ton pu will be a better puller.

As stated above IS the REASON the military has both tactical wrecker AND civi wreckers on the same base and might even be in the same motor pool parked next to each other, both can do the others job just NOT doing it well.

 

[Csm Davis]

Okay the booms on our wreckers are not weak but are under rated by the military for safety reasons. The boom and winch on a 816 or 936 are rated at 20,000 lbs the testing of them by the military is only 10,000 lbs which I know to be only for unsupported boom lifts, as I have watched the test and have a copy of it. Supported by the Travel legs it will lift at least 20,000. Case and point is lifted tow of another wrecker which I have done often, they weigh 36,000+ most around 40 fully equipped. Yes I know it is not a full 20,000 lift but it should be close and the boom and winch have no problem with it. This all said not sure without a set of plans and a engineer to sign off and a actual crane test that the state would accept this boom to do the job.

 

[Csm Davis]

Did a quick sketch/calcs from Ron's info (other thread comparing M54 and 819 drums)...
View attachment 482592
Yes, changing out the whole winch would be an option - question is - which method would be easier subject to skill/available shop etc., vs available other winch - then to addapt brackets... (prob just as much work!)
Weldersam, Big Jeff, Ron et al - don't be shy!!!

I believe that this is a good way to get the extra line you need and would give you more power as you get deeper into the drum. I was also told by a Alabama tow company, maybe the OP here, that they now require two winches per boom and I got to thinking about how to mount the second winch under the boom and to the rear of the wrecker on the boom, zebedee could you figure out how much 1/2 line would fit in half of the width of a front drum on a five ton? I believe that the drums may swap, if so he could run two lines on one split drum or mount the second winch and use only one half of one and the other side of the other so the cables won't interfere with each other. Or could you just run one winch a wrap or two a head of the other one?