Small log trailer from M720 dolly set?

[forestMog]

I want to build a side load/dump trailer using an M720 as a base.

My sketch does not yet include the detail, just a general concept. It is hard/expensive to find the hardware that comes with an S-280 shelter to use as an attach point. I have not seen drawings on the bottom connection on the S-280 shelter.

I hope to remove the lift bars from a second dolly set and weld them to the frame rails of my 'low boy' to provide the attach joint. Anyone care to comment on whether the dolly/dolly connection is as strong as the dolly/shelter connection?

 

[Larch]

avatar

What is that rig you have as your avatar? Any more pics?

 

[broman78]

looks like an old pulp wood truck with a grapple and or lift on the back. you may have better luck using an old pole trailer.

 

[forestMog]

1973 Unimog 406 forst. I keep adding stuff from scraps

 

[SCSG-G4]

720 is a smaller version of the dolly lift sets. Only about 4000-5000 pounds rating, but can be pulled by a smaller veh. 832 set is rated a bit higher and one version of the 1029 is rated up there with the CONEX containers. 280 shelters usually have a large plate part way up the corners where a very large bolt threads in. On the bottom there are brackets that hook into the bottom of the shelter and the bottom bar of the lift to keep twisting to a minimum. If you are just going to make a fixed system, just weld a square crib on the bottom with risers in the corners to attach to the bolt positions. You are basically making a fixed wagon out of the dolly set - could almost do the same with a deuce bed (dropside if you want sideloading/unloading). Just be very careful of the weight capacity - a 720 will not haul very many logs at a time. And the tires are smaller on the 720 than the 832 (832 uses deuce tires). HTH.

 

[forestMog]

looks like an old pulp wood truck with a grapple and or lift on the back. you may have better luck using an old pole trailer.

Main purpose is to transport 8' long wood on steep terrain in woods.

The log bunks are way bigger than needed, but it is what I have so that is what I will use.

The lift is important because my homegrown fork lift can only lift 24". I plan on dropping log bunk on one side and driving sideways onto the bed resting on the ground to load logs. Unload will be by winch line rigging not shown.

Dolly set has four wheel air brakes which is important on hills. The 16" lift is important too.

10" I beams from mobile home tongues will be used for the rails.

I am also considering the M832 dolly set as a base but I want to see if I can use the M720 which, because it weighs less, should be easier to maneuver in tight spots when empty. I have a scheme for moving it as a two wheel trailer when empty by adding removable struts to make the tongue solid, then use my rear lift to raise it. I know how to back a wagon but steep rough terrain makes it nigh impossible.

 

[wreckerman893]

Have you considered a bolster trailer??

 

[forestMog]

Have you considered a bolster trailer??

I'm thinking a bolster trailer is too high for me to load. Side loading/unloading sounds inconvenient, but my homegrown grapple fork lift is the only way I have to load. I could be wrong in my thinking, but I am convinced I need the lift capability and a low center of gravity. A higher lift capability sounds nice until you are on a side hill. Then its downright scary. I know I am pushing some limits here. There is very little flat ground where I work.

My theory of operation is to park the trailer sideways on the hill, lower the trailer bed, then load it by driving onto the bunk stakes from up hill using the grapple on the Mog . Unload will be by winch cable parbuckled to the side maybe with one side lowered. I don't know how steep I will be able to load but I suspect turning the loaded trailer up a 25% grade will be comfortable. I would not attempt that with a loaded trailer that had a bed height 6" above the wheels.

I am considering both the M832 and M720.

The GVW of the M720 would be below 10,000 lbs. I have no plans to operate the trailer loaded on a highway so I suppose I could license an M832 for 10,000 lbs even though it could weigh 14,000 lbs when operated in the woods. I might license it as special equipment since it is used entirely for forestry.

I want to keep open the possibility to move empty ISO containers on private property so an M832 would be a better choice for that. Of course that is another adapter project.

 

[firefox]

Note: California will not let you register M720 Dolly sets. Evidently some yahoos overloaded a
shelter and it came apart on the freeway with obvious results.
You may be able to register it if modified, but I don't know very much about that.I have a M720 in parts here in Berkeley CA which I might sell. It needs a little work but I think it is salvagable.
Bruce

 

[48cj2a]

I've installed several S-280 kits and they are not anything fancy.

The lower brackets on the shelter are just a female pocket to catch the two male pieces the extrude out from the square beam. The upper brackets are a piece of flat stock plate bent to go around the shelter corners and spread the distribution mounting on the thin skin and corner posts of the shelter. There is a square block welded to the plate treaded to catch the upper bolts and have gusseting for strength.

Unless you want to remove the dollys later I would weld or bolt them on solid, to a shortened mobile home frame or look for shelters called GRMs, S-530, S-141s or a pallet that uses the dolly. You need 407L type equipment or possibly use a duce or 105 bed, conex box to modify.

 

[gimpyrobb]

The 720 is rated to carry 6000lbs. I had one and parted it out. it uses little jeep tires on 5bolt rims. I think it should work pretty good for what you want to do. All the hydraulics are manual pumps, like working a car jack. Might want to find a hydraulic power pack to add on it. If you get one and decide the hydraulic cylinders that raise and lower the body would work for your side load arms, I still have the cyls. from the one I parted.

 

[48cj2a]

This is the pallet I was thinking of. Ours had 400cyl turbin generators on them but all part of the 407L System.

http://www.usarmygermany.com/Units/Air%20Defense/631st%20TCF%20a.jpg

http://www.usarmygermany.com/Units/Air Defense/631st TCF b.jpg

 

[forestMog]

I've installed several S-280 kits and they are not anything fancy.

The lower brackets on the shelter are just a female pocket to catch the two male pieces the extrude out from the square beam. The upper brackets are a piece of flat stock plate bent to go around the shelter corners and spread the distribution mounting on the thin skin and corner posts of the shelter. There is a square block welded to the plate treaded to catch the upper bolts and have gusseting for strength.

Unless you want to remove the dollys later I would weld or bolt them on solid, to a shortened mobile home frame or look for shelters called GRMs, S-530, S-141s or a pallet that uses the dolly. You need 407L type equipment or possibly use a duce or 105 bed, conex box to modify.

Thanks for clearing up my confusion on the lower brackets! The first image showing lifting lips is from the tech manual for the M832. The second image shows my current sketch of a log pallet to attach to an M832. Would the lower bracket be similar to what I show? If so, it would be fairly simple to make.

I am planning on using 6x6 quarter wall square steel tubing for the attachment. Its what I have. I am using 10" Ibeams from mobile home tongues as a pallet frame. Weight adds up quickly, now up to about a ton of steel for the log pallet.

Still can't decide on M720 or M832. Has anyone adapted an M720 to move an empty 20' long ISO container which weighs about 5000lbs? The lower weight would make it a lot easier to use!

What is 407L equipment and what part of GL would I search for it?

 

[48cj2a]

I dont remember any type of pin in the pocket on the lower brackets, but if it catches the male piece sticking out then it would be fine.

I'll try and look this week if any of the few shelters we still have at work have anything in the pocket and try and get some pictures too.

407L was a tactical communications system standard we used in the Air Force Communications Field. I did a few GL searches and did not come up with anything, so this will have to be a trial an error and creative search to find something.

As for the M832, we began using those as the loads became heavier and to share the spare tire with the Duce as we no longer had anything with the smaller Jeep size tires and wheels in the inventory. The load capacity is there but they are preyty bulky and hard to manuver by hand.

I attached many M720s to equipment by myself using the big wooden wheel chocks and a wrecking bar as needed, but wrestling a 832 is a different story.

 

[forestMog]

I attached many M720s to equipment by myself using the big wooden wheel chocks and a wrecking bar as needed, but wrestling a 832 is a different story.

Very good point!

If I make the log pallet connection the same as S-280 shelter then I can use the M720 to test my pallet. I can always get the larger M832 later if I need more capacity.

 

[maddawg308]

My opinion - get a M1061 2-axle trailer, put some side posts on it to hold the logs on to it. That way you can use it on or off road, without modifying the trailer itself too much.

 

[USAFSS-ColdWarrior]

I've often wondered about creative uses for Dolly Sets. Your idea has some merit. I've thought about a simple pallet/flat-bed that could be used as a float in parades or for utility purposes.

 

[forestMog]

My opinion - get a M1061 2-axle trailer, put some side posts on it to hold the logs on to it. That way you can use it on or off road, without modifying the trailer itself too much.

Thanks maddawg308.

Looks like a good option but I still want to explore the 'creative' process.

What is the bed height? Is a M-85 the same as M1061?

Can someone point me to online tech order on the trailers themselves?

 

[forestMog]

Found bed height is 37" on this site.

I don't have a logsa account so I guess a tech manual is out of my reach.

Thanks to all for the great info on this site!

 

[forestMog]

I have made a decision to use the M720!

Got one that looked like it has never been used since the shipping box which contains hoses etc is still strapped to it. When I inspected there was some easily repaired damage on the lunette stop and a flat tire. Most in the lot did not sell so it was way cheap.

I almost wish I had bid on two just in case I need an extra part but I didn't want to make two 300 mile+ trips for pickup. Shipping for two would have been about $400, still cheaper than I anticipated.

The dolly set tow speed for the M832 is listed at 30mph max when not carrying a shelter. No limit is shown for the M720 but I expect there may be similar issues because of the short wheel base or because of the light weight.

Anybody got ideas on how to increase safe speed? Maybe reduce tire pressure down to about 12lbs? I am considering adding a couple of struts to lock the steering and lift the front wheels off the ground so the dolly set will pull like a two wheel. I estimate 700 lbs tongue weight when set up as a two wheel. I have a weight distribution hitch I can use to improve handling of the towing vehicle.

I am towing it with a one ton 4x4 Ford van and will choose a route off the freeway. I will be inspecting and greasing the wheel bearings.

Now to wait for EUC. My first EUC took more than 60 working days. Hopefully they know me better now.