crane service bed

1. #1td25c2013-02-23 15:06

   I done this to my Knapheide service bed so we could mount a crane to it. I started out buy lining the inside of the rear compartment with 1/8 inch sheet steel with holes drilled in it so it could be spot welded to the bed.Then welded in angle iron in all the corners,added 3/4 inch plate on top to mount the crane on.To help strengthen the bed itself I added a channel iron crossmember at the front of the compartment that went all the way accross the bed and also is bolted down to the truck frame.At the rear of the compartment I bolted into the bumper,This added alot of strength & realy tied it in to the truck ( see red arrows showing channel & bumper bolts,Sorry about the paint job).The bumper also is used with the manual pin type outriggers. Here is a thread where we were using it to change out a front idler on the dozer HeavyEquipmentForums

2. #2Mike L2013-02-23 18:17

   make sure you build downriggers for the back corners. I got my crane body second hand and the po didn't have downriggers on it. if you look close at my body it has a lean to the crane side. I bought crank down trailer jacks from tsc and welded them to square tubing that fits inside of bigger square tubing so they extend out for more support.

3. #3Shenandoah2013-02-24 01:11

   I have a Knapheide crane service body that has the right rear corner box braced for the crane. But they also run torque beams under the entire box to spread the load over the chassis. Below is a link to one of their PDFs that will give a glimpse if what I'm referring to. http://www.knapheide.com/media/uploads/Products/Crane_Bodies/Crane_Bodies_Literature.pdf And outriggers are a must. The forces the crane will put on the box can be calculated in foot pounds. One foot out with a thousand pound weight = 1,000 ft lbs. At four feet out the same weight yields a 4,000 ft lb load. Jerk the load and the ft lbs skyrocket. For the long haul you'll want to correctly engineer the box and braces. One of the things that could help is if you can get a close-up view of another functioning factory box, and pay attention to not only the inside of the cabinet, but also how the loads are distributed to the truck frame. That means looking below deck. My box has welded braces that bolt to the back of the truck frame and U-bolts that tie the front down. I wouldn't recommend U-bolts on the rear where the crane sits, fwiw. But that could be just me. Also remember that your outriggers need to be directly tied into the box bracing and not separated by any distance of sheet metal. In other words, the support frame needs to extend enough to tie into the outrigger structure. My drivers side outrigger is stationary going only up and down, and the pass side also goes outboard about 5+ feet. It's a massive torque tube that is encased in another massive tube, and pulls out manually and retracts the same way. My outriggers are crankers just like the ones you see on 7k or 12k trailer jacks. Those work good, so size yours for your most extreme load. Btw, companies like Knapheide, et al, use a special grade of steel like T1 and not your normal run of the mill steel that doesn't have enough tensil strength. So if you fabricate your structure with over-the-counter steel go overboard on thicknesses rather than be conservative. If you build it and it twists you may have to spend extra energies and monies doing something you could have easily accomplished from the get-go.

4. #4big b2013-02-24 22:46

   Thanks everyone for the pictures and the link to the website, keep it coming with the picks and advice.