Flatbed dump bed build

[Ike Carlson]

I hope this is ok to post here. I am looking to bounce my ideas off of some other bright minds and maybe help someone out.

I have a 1991 F-250. It has been beefed up a bit and regularly hauls 5-6k lbs.
Yep, the weight is right and the truck hauls it without trouble. I haul logs, firewood, hay, rocks, etc... It's a farm truck.

It will use a telescopic hoist at the front of the bed and will have a 60* dump angle. I will use the power steering pump to run the hoist since I have manual steering and the telescopic cylinder only needs ~500 psi to dump a full load.

I'm using rectangle tube for the main rails and side rails. It won't add too much height, has a good bending moment, and is the best balance between strength, weight, and rigidity. I might use small I beam or tube for the cross members.

I am trying to decide if I should put the cross members between the rails or on top. Between is going to be more work, but would be lower. Setting them on top is quick and easy and would increase the section height of the bed, but that may encourage washboarding with the deck in compression. I don't mind a bit more fit up if it gives a better product, but I am looking for input to help make up my mind. I don't want the deck to be a mile in the air. I like to keep the center of gravity low and the truck easy to load by hand when needed.

Has anyone put the cross members between the rails? How about on a dump bed?

Edit: I am also considering a torque tube to minimize twisting. That way the cylinder lasts longer and I can hang deer/pigs from the front corner of the bed.

 

[matt_i]

The power steering will work but could be slow. Its not a ton of flow because the system doesn't require that. Although on a truck with hydraulically boosted brakes (not sure if yours has that, my 1988 GM does) it may be a larger pump.

Somewhere you will also need a bigger reservoir for fluid.

I think you are on the right track as far as making sure the cylinder doesn't bind. A misalignment coupler can only go so far. A triangulated shape like you'd have on a trailer tongue would be ideal but isn't going to mesh with existing frame rails without being on another plane.

Also it would be worthwhile to work out the physics of how much load is on the cylinder when collapsed, because that will be the heaviest loading. Could easily get into 10-15,000 lbs of load trying to raise 5000 lbs in the bed with the cylinder nearly horizontal at that point.

Hope the project goes well, we love pictures and make sure you document and post them

 

[Ike Carlson]

The cylinder is vertical, not horizontal. That was the first thing I made sure of. I don't like high forces or concentrating them. I already bought the cylinder and it will sit right behind the cab. It will see half of the load or a bit more, since I like to put at least some of the load on my front axle to maintain good handling.

 

[jsaw]

Are there any maximum pressure ratings on the cylinder? Power steering pumps are capable of producing 1000 psi.

 

[Ike Carlson]

It is good to at least 2500 psi.

 

[kbs2244]

It will work, but slowly.
and you will need a larger remote tank

 

[Ike Carlson]

It will work, but slowly.
and you will need a larger remote tank

That's no problem. I can weld air and water tight.

 

[Yarz]

My initial thought is cross members between the rails, strictly for the height aspect. I don't know how much harder that will make it though, and if it's worth that effort for just a few inches.

I'll be watching to see what you do.

That's no problem. I can weld air and water tight.

I don't think either of those will help in a hydraulic system...

 

[zkdiesel]

Probably better off with a stand alone hydro electric unit for dump. Have three Henderson 3 stage telescopic beds with front mount cylinder. All use the standard hydro electric unit with no problems.