M936 Boom hoist mod to double cable length?

[MOFTA]

Has anyone modified/changed the boom hoist to increase the length of the cable? Specs show it mounts 95 feet of cable. I've a need to increase it to 200ft +. I'm thinking the sides of the existing drum wouldn't hold it in place.

Any changes done by anyone without custom machining etc? I would like to be able to do it with readily available/surplus parts, without changing the appearance too much.

 

[73m819]

Double the width of the drum, you would need to make NEW drum mounts.

 

[doghead]

More wraps on the drum will equate to more strain on the winch drive/brake.

 

[73m819]

If he makes the drum wider, the load would be the same on the drum drive and brake, the problem he might have will be getting the cable to lay right on a wide drum (the fleet angle might be to tight), if he went to a fatter drum (higher flanges), then the extra wraps WOULD put a lot of extra load on the drive, ect..

 

[zebedee]

I believe we 'done this one to death' already.... started in post #115 of thread
http://www.steelsoldiers.com/showth...bed-modification&highlight=wreckery+body+mods

Longer drum in it's current position would not load either end - fleet angle as Ron mentioned and interference of boom cyls to name just one.

A second or third layer would mean side extensions but give reduced lift capacity by a percentage per additional layer and also require new or extended drum brackets and slightly adjusting the plumbing of the motor.



What is the reason for the additional 100 ft?

 

[MOFTA]

In researching the basic requirements of wreckers in Alabama being used on state call rotation, minimum 200ft of cable is required on all boom winches. I have been asked about putting a M936 body on a Class 8 chassis for commercial use as a rotator.

It would also require an underlift unit to be mounted under the chassis for the actual towing. The load specifications will be the limiting factor as to what "Class" the M936 bed could operate as. The document specs are based on the some of the modern larger commercial units I would believe.

Wouldn't affect private towing, just being permitted to operate on the government official wrecker call rotation roster here, the way I'm reading the document.

Might just have to list it as a crane for lifting and be done with it. According to the specs in the state document, the M936 wouldn't even qualify as being called a wrecker.

Thanks for the input.

 

[zebedee]

In researching the basic requirements of wreckers in Alabama being used on state call rotation, minimum 200ft of cable is required on all boom winches....

I think it can be done - but the reasoning for the rule is probably related to all modern civi wreckers use the boom winches for recovery as they do not generally have additional drag winches - which our ones have, with plenty of feet in that dept. So it might be worth getting a clarification to the ruleing from someone in "higher authority" with regards relevance of a military body (added drag winch) being an exception.

Afterall - you wouldn't use the extra for lifting anyway (the boom is only so long) and you have an adequate enough drag winch for recovery.

For the sake of compliance (pre excemption) the second mod would be easiest to achieve....


Here's a thought..... If you will never need the extra 100 ft for lifting - why not make the drum smaller! Enough for two more layers, that way you get additional feet, DO NOT have to extend the brackets or plumbing or ends of the drum. I am sure the drum is just a tube - and if you are using the second and third layers - the drum can be smooth as the cable would wrap neatly in the grooves of the previous layer. No compromise with lift capacity - since largest diameter is the same...... "Brilliant!" (said with Irish accent)

 

[MOFTA]

I believe we 'done this one to death' already.... started in post #115 of thread
http://www.steelsoldiers.com/showth...bed-modification&highlight=wreckery+body+mods

Longer drum in it's current position would not load either end - fleet angle as Ron mentioned and interference of boom cyls to name just one.

A second or third layer would mean side extensions but give reduced lift capacity by a percentage per additional layer and also require new or extended drum brackets and slightly adjusting the plumbing of the motor.



What is the reason for the additional 100 ft?

In going back to the above referenced thread, I confirmed the minimal increase in the lengths of the cable between the different existing models. It didn't come anywhere close to the needed 200ft I have asked about.

I was hoping that someone might have used a front mounted winch drum or such as a solution and already been through the process and confirmed it. I didn't want to reinvent the wheel if a solution was already available.

 

[MOFTA]

I think it can be done - but the reasoning for the rule is probably related to all modern civi wreckers use the boom winches for recovery as they do not generally have additional drag winches - which our ones have, with plenty of feet in that dept. So it might be worth getting a clarification to the ruleing from someone in "higher authority" with regards relevance of a military body (added drag winch) being an exception.

Afterall - you wouldn't use the extra for lifting anyway (the boom is only so long) and you have an adequate enough drag winch for recovery.

For the sake of compliance (pre excemption) the second mod would be easiest to achieve....
View attachment 482589

Here's a thought..... If you will never need the extra 100 ft for lifting - why not make the drum smaller! Enough for two more layers, that way you get additional feet, DO NOT have to extend the brackets or plumbing or ends of the drum. I am sure the drum is just a tube - and if you are using the second and third layers - the drum can be smooth as the cable would wrap neatly in the grooves of the previous layer. No compromise with lift capacity - since largest diameter is the same...... "Brilliant!" (said with Irish accent)

Now THAT is more along the lines of what I was thinking. I thought that maybe someone had already come up with a suitable existing drum that would fit the existing hoist components. Would only have to change the existing mounts for clearance.

You put my thought into picture! Thanks.

 

[Floridianson]

I trying to understand the need for 200 foot of crane line. If you ran the rear winch cable up to the boom where there you have a snatch block would you not have your footage plus boom.

Also you could rerig your winch with amsteel blue and get rid of the 5/8 cable. 1/2 amsteel goes 30,600 lb and 7/16 goes 21,500lb. Then you drum would carrie a lot more.

 

[MOFTA]

That would create an awful lot of downward pull against the boom cylinders, unless you had the support legs locked in place. Plus you would have to hang a sheave for the 3/4" cable from the boom itself, unless you had it suspended by the 5/8" hoist cable, cutting your load rating.

Just getting that large 3/4" sized block up there would pose its' own challenge.

 

[Floridianson]

The boom end has a hole in it allready and leave the block there. Yea you would need the support leg locked just as it should be. All that would be needed might be a roller built into the top where the cable might ride.
I have had to do this when trying to lift up on the stuck truck as sometimmes you need to pull up just not out.

 

[MOFTA]

Worth going out and checking the angles on the cable coming out of the roller fairlead.

 

[zebedee]

Did a quick sketch/calcs from Ron's info (other thread comparing M54 and 819 drums)...

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!!!

 

[Floridianson]

No roller on top just bottom and sides. Just add one so you could run short boom. Also I don't worrie about getting a 150lb block anywhere. lol

 

[zebedee]

Now THAT is more along the lines of what I was thinking. ........ Would only have to change the existing mounts for clearance.

You put my thought into picture! Thanks.

Not even that - NO CHANGE TO MOUNTS OR BRACKETS - just change the tube in the drum!




Floridianson - "I trying to understand the need for 200 foot of crane line." ..........

I'd guess it's just the state only knowing about civi wreckers w/o drag winches - just boom winches. But as they have decided they need ability to recover casualties upto 200' from the highway without wrecker leaving hard road, that is where they think only booms can do it. What they should do is specify just a recovery distance.

 

[doghead]

Consider a 2,3 or even 4 part line rigged to a truck 35' off the highway down an embankment. 200' of cable isn't really enough. Consider the time needed to rerig several times for a recovery like that. Also consider that you have a 5 ton lift capacity.

Your truck is no where near capable of heavy truck recoveries.

 

[Floridianson]

I thought with supports down the boom could go 20,000

 

[doghead]

What good is a rotator on supports?

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

 

[zebedee]

Quick approx calcs...

Original drum 10" dia, 17" long can hold ...
17 x 2 x pi x 10 / 12 = 89'

Smaller drum 8" dia 17" long can hold ...
17 x 2 x pi x 8 / 12 = 71' inner layer
17 x 2 x pi x 9 / 12 = 80' middle layer
17 x 2 x pi x 10 / 12 = 89' outer layer
Giving total of 240'

Not taking into account the additional cable from the drum, up the boom to the hook, or the adjustment to the smaller diameters due to meshing of layers therefore more length (ie. First layer 8.4" dia not 8", second layer 9.2" dia not 9")