Results 1 to 2 of 2

Thread: M105A2 bed moved to a dually, dump bed feasibility. hydraulics and frame ??s

  1. #1
    Colonel
    Join Date
    Jul 2011
    Location
    St Pete, FL
    Posts
    207
    Thanks
    29
    Thanked 174 Times in 74 Posts

    Default M105A2 bed moved to a dually, dump bed feasibility. hydraulics and frame ??s

    Im going to be losing access to my metal shop in the near future so I am getting all of my fab and welding projects out of the way instead of working on generators.

    The project:
    After much research, measuring, talking with people to see if I am crazy, more measuring, more research, (both with and without alcohol) I have decided not only to move this M105A2 trailer bed to my truck after I used the trailer for another project. Thats not too big of a deal in itself, my 90 gallon transfer tank is behind the cab, the bed will be flipped around and shortened so the wheel wells line up. Originally the transfer tank was going to partially sit on the bed and the wall was going to be welded in front of the transfer tank which allows me to have an 8' bed with the transfer tank and tailgate closed. The transfer tank is vertical so it doesnt take up much. Now that I am mapping out the dump bed idea I will be mounting the transfer tank to the frame separately from the bed itself. Ill definitely be shortening the bed, but how much is left to be determined. The wheel wells inside the bed will be completely removed because the tires will never be up that high I had 8700lbs in the bed once, still not enough sag to warrant any concern for tires rubbing.

    The added weight is welcomed. I am disappointed that my tires are at the minimum on the load inflation tables because the lack of weight. I used to haul a 12 ton equipment trailer around (pintle) and the truck handled beautifully; this project basically returns this truck to it's former glory while adding a unique MV look to it. (I still miss my trailer, I sold it for a down payment on a house)

    The area where I need to bounce ideas around and soliciting wisdom and knowledge:
    For the dump bed and putting about 5 hours into it there are a few items that im looking for ideas on. Lets start with these assumptions: Shortened to 8' and wheel wells removed and reinforced, level load of fill dirt / topsoil, dont ever plan on loading "heaping", and lets use numbers that gives enough capacity to not prematurely wear out whatever is installed. Lets say 2500lbs/yard and 2.75 yards capacity. Since 2500lbs is higher, lets say we have 6000lbs of payload on 1000lbs of bed.

    So Ive found these pickup truck dump bed conversions. Im not impressed on their construction or capacity for the ones for the OE truck bed. I found some from Premium Supply that look nice but no other brands so far.

    And then there are direct push style, like what would be on a dumptruck or towtruck. Im leaning more towards this because these are farther away from the pivot point so the bed and frame stresses would be less. The problem here would be it would almost have to be telescoping rams.

    The questions become do I put together my own kit using telescoping rams or go with a premade scissor style? Would going direct push be the equivalent to reinventing the wheel since most of the pictures of dump trailers and bodies are the scissor type?

    If I was reinventing the wheel do I go with a power pack or throw on a 2nd power steering pump for my hydraulic supply? I think I am answering my own questions and since the premium supply kits are around 1300-1500 I think that should be the choice unless I can go the direct push route for cheaper. My thoughts for direct push would be that I could mount the rams outboard of the frame and use longer rams, lower pressure due to angle and get away with not needing a power pack. (The truck already has 2x 8D batteries)

    On to more questions. Say I went scissor style. What kind of bed reinforcement would be required for this thing? I figured some square/rectangle tube running the whole length perpendicular and below the hat channel stiffeners that run side to side on the bed. Recommendations on size? Can I A) notch the side to side supports to add taller rectangle tube stock and weld the notched supports to the new frame, B) notch the rectangle tube stock to accept the existing supports or C) should I not notch either and add some flat stock to take up most of the gap? Will I loose too much structural integrity by notching? I see option C as the best option and now I just need sizes.

    For hinge placement, I was going to overhang enough to clear my pintle hitch with the tailgate completely down. This shouldnt be too hard as the bed is plenty long before I shorten it. Any thoughts on if that amount of overhang is enough or should I go with more?

    Reading about angle, I dont want to play the game of rocking the bed up and down to break a load free so I am thinking I should be shooting for 50degrees. thoughts? My anticipated loads are likely to only be fill dirt, topsoil, and runs to the scrapyard/dump.

    And finally lets discuss bed length. How long is too long? I already cant fit in the oversized home depot parking spots and the wheelbase doesnt allow me to make a U-turn in a 3 lane divided road (Id have to be in the fast lane to start a U turn) so adding length isnt a big deal from a maneuverability standpoint. I just dont want to change the wheelbase. Theres plenty of fast food joints that I cant get into already.

    My options are 1) to cut the bed down after flipping the tailgate to the other end so the wheel well (kind of) lines up with the axle which leaves me an 8' bed which doesnt even overhang my current hitch (about 6 inches short), 2) leave it 9'2" and extend the truck's frame, easily clears the hitch now, or 3) go with the 8' bed and because im in there cutting and welding already pull the hitch in 6 or more inches so I effectively shorten the truck, have an 8' bed, and a transfer tank outside of the bed. Now that I type it out it sounds like #3 is the winner. Plus anything that adds weight behind the axle is a plus because this truck is so front heavy its ridiculous.


    All things considered this thing is going to be overbuilt. Sweat equity im counting pretty low. This truck will also have provision for a gantry (outboard of the bed) which will make my generator deliveries cake, but that part is easy to plan for (just need to design where my 2 bars going under the bed will run so I can install them later)
    It's not that I have too many generators, it's that I don't have enough room.

  2. #2
    Colonel
    Join Date
    Jul 2011
    Location
    St Pete, FL
    Posts
    207
    Thanks
    29
    Thanked 174 Times in 74 Posts

    Default

    As this progresses my knowledge progresses. Found some tools to help that I am learning how to use. I found a calculator for "Beam bending equations calculator - supported both ends loaded on 2 points with equal loads" on Engineers Edge that helps with creating the crossmember that could support the bottom part of the scissor hoist, or a similar calculator for other configurations. Im getting the hang of the variables and thus far the output seems to be correct by estimating from real world experience.


    For the sake of design I am going to up my limit to 10000lbs (7500 payload, 1000bed, 500 for added structural stuff) so I know for a fact it wont be underpowered. The hydraulics depending on angle and connection point could have a max load of anywhere from 50% (tipping from the very front) to 100% (tipping at the middle point and ram / scissor perpendicular) to much more than that depending on how the triangle for the pivots is shaped. Thats for the connection points.

    My main trouble is finding a calculator for a beam load supported 2 points (not ends, having overhang) with load equally distributed on the beam. (the beam that will be under the bed to stiffen it up)
    It's not that I have too many generators, it's that I don't have enough room.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •