The A-frame kit (hoist) for M35-let's talk about it

[jesusgatos]

So, making extensions for the towbar legs looks like a pretty straightforward project. But let's talk a bit more about the top of the A, where the two legs come together.

I want to make the A-frame extension foldable. I'm thinking about something that might look a longer version of the towbar. Then I'll want to have:

1) some type of pulley that you could run a winch-line through?

2) a hook, so that you could also attach something like a chain-hoist?

3) an attachment point for the tension-line that runs back to the pintle-hook?

Anything else?

I've got an M109. Should I be able to run two tension cables back to the two lifting points at the top/front corners of the box? Talking about 3000lb max lifting capacity here. All four lifting points on my M109 box are tied together with 2" x .120 HREW tubing, so the load would be distributed a little better than on a normal M109 box (here's a link to a picture). Still, I've got a lot of cabinetry inside that box and I'd sure hate to twist is all out of shape...

Speaking as a mechanical engineer, the wire rope going back to the pintle will be in tension, the towbar/pipe/whatever the uprights are made from will ONLY be in compression, assuming the pipe is attached as a pivot at the lifting shackles on the bumper. If the uprights are slipped thru the lifting shackles, and "wedged" against the shackle brackets, then bending may come into play. Just make sure the pipe is attached to the lifting shackle or lifting shackle brackets in a way that allows the pipe to pivot, then there won't be any torque on the pipe, only compression.

As an example, if you attach the pipe to the shackles, tilt them to whatever angle you want them to be at, let them go and they stay pointed towards the sky (without the wire rope attached), then they will have torque (bending) stress on them...not good. Attach the pipe so that if you point it towards the sky, then release the pipe(s) they fall back onto the ground, pivoting on the lifting shackles.

Clinto, in your picture above, the cross member at the top of your rig DOES have combined stresses (tension, compression, shear, Von Mises, etc). Also, it looks like the wire rope is slack, which means the uprights are supporting themselves inside the lifting shackles. If you lift that crate without tightening the wire rope you're running the risk of buckling the uprights inside the shackles. Tighten the wire rope until it has pulled back on the uprights some.

I was thinking the same thing about the picture that clinto posted (bending loads). Somebody posted a TM diagram that shows a similar assembly in detail. I'd rather make an A-frame that puts the legs in straight compression, but I'm scratching my head trying to figure out the best way to do that.

I could connect the top-ends of the two legs with a short bridge, with pivots where each leg is attached to the center-bridge. The pulley and cable/hoist attachment points would be mounted to the bride and that would put the legs in straight compression, but seems like it might make the whole assembly kind of 'floppy' and unstable (side-to-side). The solution might be as simple as tightening down the pivot-hardware?

Or I could something similar to the towbar, so that one leg would be in straight compression, but the other leg would see a bending load. That might not be such a big deal though, I don't know.

I could also connect the top-ends of the two legs together (single pivot), although that would require putting a little bit more thought into the pulley and cable/hoist attachment points (would have to be mounted to that same pivot-point in order for that design to work).

What else? I feel like there's probably a better way to tackle this problem.

I don't think that the frame or bumper would be the weak link here but I've found a tendency for the stamped frame extensions to bend downwards, as well as cracks to the lower rear portion of the (stamped) winch brackets. See pics.
3000 lbs @ 10' is definitely a lot of leverage!

G.

I don't have a winch on my truck yet, but I'm wondering whether it might be possible to put a 2nd set of shackle-mounts back where the shackles are mounted on non-winch trucks (on top of the winch extension bracket. At least that would put the load from the A-frame directly into the framerails (except for the upwards pull on the winch-line if you're using a winch).

I've been planning on adding some type of high-clearance (pivoting/telescoping/removable) hydraulic outriggers/jacks to Mah Deuce. Taking some of the load off the frame will be a secondary benefit though, the main reason is to level it out (it's an M109 motorhome).

 

[saddamsnightmare]

January 28th, 2010.

We used to have two of the old civillian 1948 Dodge Power Wagons with PTO winches, and the mechanics were able to fabricate the gin poles to fit the front bumper sling hook feet, just like the deuce. The poles were probably between 15 and 20' or so long, and the trucks could pick up enough weight with these that we had to weight the beds with 1 ton concrete slabs to keep the trucks from nosing over. The system worked really well on the Dodges and ought to do even better on the deuce and a half, what with all the inherent bed and rear drive weights already present.
I'll bet David Doyle could come up with the dimensions and weights of the tubing used out of his magicians's hat....

Cheers,

Kyle F. McGrogan

 

[jesusgatos]

Uh, what about extending a towbar by simply inserting some appropriately sized tubes between the two halves of the towbar to lengthen it? It would be super easy to make, only requiring a couple of tubes and an extra set of pins. I'd need to rig-up some anchor-points, but that's no big deal.

 

[emr]

U can just use the correct size high grade pipe that will just fit into the to lifting shackles, and just weld em in with a slight angle towards center and then weld em together with a short 10 inch pipe and hang a snatch block on it like the mil did, My A frame had the wrong conectors so I cut em off and slid em into an extra set of shackles and they are awesome...

 

[jesusgatos]

emr, would you mind posting some pics? I'm sure that works well enough, but I'm looking for a folding A-frame. I think making simple extensions to slip between the two halves might be the best way for me to go right now. I'll only have to carry two additional sections of tubing, and I could pin those two pieces of tubing together to make one long pole that I might find some other use for.

 

[jesusgatos]

How tall/long are most of the A-frame setups overall? I'd like to build an A-frame that's about as tall as a Deuce can handle (lifting something that's approaching that 3000lb weight limit).

 

[tm america]

i like the extended tow bar idea.but i think you would be better off going to the front lift points on the bed .they are made for lifting not pulling.if you go to the front one it will have more vertical load than it would on the back ones. this will help keep things from twisting and bending .The longer you make the gin poles the less horizontal load there will be on the lift points to.also the sopport legs are a goo idea to i seen some gin pole setups that didnt use cables going to the back just to legs going up to the snatch block and two more going back to the ground from the snatch block they lift more but you cant move the load like that

 

[jesusgatos]

I'm not sure I understand what you're saying. Are you talking about the lift-point on my M109 box, or on a regular Deuce bed or...?

 

[tm america]

the shackles on the top four corners of the m109 box are for lifting the bed of the truck with a crane or wrecker.not tie down points even though they could be used for that . look at the tms about removing the bed you will see what i am saying

 

[tm america]

the truck lift points are the same for the m35 and m109 it is the pin on the rear spring mount and the shackles in the front the rings on the bottom of the bed are just guides for the lift strap.the bed lift points are strong enough to pick the bed up they will at minimun hold 1250lbs each . with a a frame on the front of the truck the front mounts hold most of the weight .i bet the cables going to the bed only need to hold 500- 700lbs if the a frame is at a 60 degree angle like it should be

 

[emr]

I gave all dimensions of the correct A fame, pipe diameter lentghs etc, thickness and so on, in a past post about A frames. i will take some pics, and put em out soon, They were made to be used on the front tow/lift shackles on the bumper, these were made for towing and lifting. as the tow bar hook up and the Tree from the wreckers hooks right to em, and as david Doyle in a year or 2 ago posted picks of in service trucks being loaded in ships going over seas being lifted by em also. in theater and in home port...just an fyi, not imoprtant i guess...I run the cable to the back top of my wrecker set # 7 It has been at our show set up and may be this year also, since i may have it for sale with everything i ever collected for a deuce with it. that includes A frame ,tow bar all the trimmings ,both axle clamp sizes a military Holmes sling set and wrecker set #7 , A super nice shelter that just fits nice in the back, do not know what its called but is sweet, new metal bows and new cab and bed camo covers, a half cover to be used when the wrecker set is in it, to much to ist actually, so much parts the truck could be rebuilt, almost a double part for everything....just sayin, since im thinking about the A frame...

 

[tm america]

i agree the front shackles are more than strong enough to hold 3000lbs . i think the reason they rated them that low is for 2 reasons.first the front springs arent gonna handle much more than that.second the cable on the winch is rated at 10000lbs for winching but would have a much lower lift rating.it would be rated more closely to 3000 for overhead lifting

 

[jesusgatos]

the shackles on the top four corners of the m109 box are for lifting the bed of the truck with a crane or wrecker.not tie down points even though they could be used for that . look at the tms about removing the bed you will see what i am saying

Oh, I know those are lifting points. I just didn't understand what you were saying. And I was a little bit concerned about pulling forward (off-vertical) on those lift-points. Just don't want to stress the box.

 

[emr]

If u are thinking of going off the box maybe a four way cable to put equal tension on all four points, that would do it, But I would still be very very careful, the lift and pull on those are sure different like TM said, ripping them off would be a sad day for sure

 

[jesusgatos]

If u are thinking of going off the box maybe a four way cable to put equal tension on all four points, that would do it, But I would still be very very careful, the lift and pull on those are sure different like TM said, ripping them off would be a sad day for sure

I've got an M109. Should I be able to run two tension cables back to the two lifting points at the top/front corners of the box? Talking about 3000lb max lifting capacity here. All four lifting points on my M109 box are tied together with 2" x .120 HREW tubing, so the load would be distributed a little better than on a normal M109 box (here's a link to a picture). Still, I've got a lot of cabinetry inside that box and I'd sure hate to twist is all out of shape...

I've already modified the lifting points on my M109 box (I used those points to build a roof-rack around the perimeter of the box). Take a look at the picture in the quoted text above. I think that tubing should do a pretty good job of tying all the lift-points together and equalizing the load. A four-point sling like you're suggesting would probably be a pretty good idea though, if the A-frame is up high enough to let the cables going to the back corners take some of the load.

 

[jesusgatos]

So, making extensions for the towbar legs looks like a pretty straightforward project. But let's talk a bit more about the top of the A, where the two legs come together.

I want to make the A-frame extension foldable. I'm thinking about something that might look a longer version of the towbar. Then I'll want to have:

1) some type of pulley that you could run a winch-line through?

2) a hook, so that you could also attach something like a chain-hoist?

3) an attachment point for the tension-line that runs back to the pintle-hook?

Anything else?

I've got an M109. Should I be able to run two tension cables back to the two lifting points at the top/front corners of the box? Talking about 3000lb max lifting capacity here. All four lifting points on my M109 box are tied together with 2" x .120 HREW tubing, so the load would be distributed a little better than on a normal M109 box (here's a link to a picture). Still, I've got a lot of cabinetry inside that box and I'd sure hate to twist is all out of shape...


I was thinking the same thing about the picture that clinto posted (bending loads). Somebody posted a TM diagram that shows a similar assembly in detail. I'd rather make an A-frame that puts the legs in straight compression, but I'm scratching my head trying to figure out the best way to do that.

I could connect the top-ends of the two legs with a short bridge, with pivots where each leg is attached to the center-bridge. The pulley and cable/hoist attachment points would be mounted to the bride and that would put the legs in straight compression, but seems like it might make the whole assembly kind of 'floppy' and unstable (side-to-side). The solution might be as simple as tightening down the pivot-hardware?

Or I could something similar to the towbar, so that one leg would be in straight compression, but the other leg would see a bending load. That might not be such a big deal though, I don't know.

I could also connect the top-ends of the two legs together (single pivot), although that would require putting a little bit more thought into the pulley and cable/hoist attachment points (would have to be mounted to that same pivot-point in order for that design to work).

What else? I feel like there's probably a better way to tackle this problem.


I don't have a winch on my truck yet, but I'm wondering whether it might be possible to put a 2nd set of shackle-mounts back where the shackles are mounted on non-winch trucks (on top of the winch extension bracket. At least that would put the load from the A-frame directly into the framerails (except for the upwards pull on the winch-line if you're using a winch).

I've been planning on adding some type of high-clearance (pivoting/telescoping/removable) hydraulic outriggers/jacks to Mah Deuce. Taking some of the load off the frame will be a secondary benefit though, the main reason is to level it out (it's an M109 motorhome).

I've got a medium adjustable towbar now, and also picked up two extra short-side towbar legs (inner and outer halves), thinking that I'll cut the ends off these and use them to extend the towbar to make a taller A-frame. Make sense?

Still wondering about the best way to attach the towbars at the top of the A-frame though. Not worried about modifying them, so open to anything (cutting, welding, drilling, etc.). I can think of a few different ways to make something that I'm sure would work, but would like to hear from anybody that has experience with these sorts of things (lifting, rigging, etc.).

 

[gimpyrobb]

I'd be interested in those knuckles you cut off!

 

[jesusgatos]

Sure thing gimp. I'll let you know if I decide not to keep them for something else.

 

[hoopsoft]

We made a set for mine used oil field tubing 3" and 2.5 inch, they are adjustable from 12' to 18'.

I've picked up the front of another deuce with it. (supporting the bumper with hilifts to not stress the springs)

 

[Jakob]

Nice looking setup there, what'd you do for the bumper mounts?