Chassis Brackets for Spring Mounted Flatbed

I originally had intended to make a 3 point mount for my camper, similar to a Unimog's.  This type of mount eliminates the transfer of twist in the frame to the truck bed, or the camper on it.  It is important to protect the camper from twisting, the chassis flexes quite a bit when on uneven ground, so that cabinets stay fastened, walls don't crack, doors don't jamb, etc.  It also allows the frame to flex freely, which supplements the suspension.

After being educated by the group at Expeditionportal.com, I decided to use a spring-based mounting system.  I basically decided to copy what the M35 (Duece and a Half) uses.

The basic advantage over a 3 or 4 point system is that the load is spread over the entire length of the frame, and it is probably easy to build a spring system than a 3 or 4 point system.   Having the load spread over the entire length of the frame is needed for the truck with lighter and/or not boxed frames. (This is all relative of course and the F-450 has a huge frame by many standards)

To replicate this system I purchased angle iron, actually steel, 5"x3" and 1/4-5/16" thick.  I cut it to the necessary lengths, added extensions where the frame had the depth to allow it, drilled holes in the plate that allowed me to use existing holes in the frame, painted them, and bolted them on.   It took WAY longer than it should have, as everything seems to do.  I was able to fit six mounts total, 4 of them with room for two springs and 2 of them with room for one spring.

I used Grade 8 hardware all around, in 7/16, 9/16 and 3/4", all in 2" length.  You can see in the picture above how the bolt in the upper right corner is smaller, I was able to use all existing holes in the frame which preserved the paint, the strength, my time and drill bits.   The frame is 8" deep at this point, so I welded a 3" plate on.  This bracket, along with one just like it on the other side, are directly behind the cab.  

For the two brackets in the middle of the frame, which each have room for one spring, I had to get a little creative.

I used the same angle steel and welded on a 1/4" strip of steel, with a 3/8" spacer at the end, and bolted it up within the leaf spring perch.   Because the leaf spring perch is not as deep as the mount springs, I will need to cut one down and will probable try to fit a small section of spring above the angle steel that will come off of the flatbed structure.  Again, I used Grade 8 hardware and existing holes, with one 3/4" bolt into the frame and a 9/16" into the cross member.


For the rear most brackets, I incorporated them into the custom hitch that I built.

These got 3 x 9/16" bolts.





For all the hardware I used a lock washer and in some cases I also used a lock nut.

The brackets were coated with two coats of POR15 and two coats of Rustoleum aerosol can truck bed liner.   I am not happy with the coatings and will speak more about that later, it may be my fault.

One "trick" I used to mark the holes on the plates, for drilling, was to clamp the plate to the frame in the final position.  I then took a socket that fit just exactly in each hole that I wanted to mark.  I then dipped the end of the socket in spray paint, with the longest extension clipped in the socket.  I then pushed the socket through the existing hole in the frame and make a nice circle of orange spray paint that was centered and let me drill fairly accurately.  All of my hardware is 1/16" smaller than the hole it is in, to allow a little bit of wiggle room.  The hole(s) in each bracket for the spring bolt to bass through are 3/4", the bolt itself will be 1/2" or 5/8".