I was able to work on the bumper-project today. It's been dragging out because there were a few "dimensional issues" that have had me stumped. I know some of the problems involve a slight bending of the front end (frame and body), which I mentioned in my last post. So I decided to check out the body lift done by the previous owner, which was not a prefabbed kit. After spending countless hours measuring and scratching my head ( <img src="/forums/images/graemlins/confused.gif" alt="" />), I finally realized that the lift blocks were not of uniform size. They ranged from 3" in the front to 2.75" in the back - but did not taper to give a "pre-runner" look. And it appears the shorter blocks were "shimmed" using rubber matting (the outdoor v-groove type). So what I thought (and was told) was a 3" body lift actually created about 4" of lift, though not uniformly <img src="/forums/images/graemlins/zombie.gif" alt="" />. In fact, the lift was so "not uniform" that the left-rear of the body actually "popped" when I unbolted the body - like it was under spring-tension. Now I understand why. If you're wondering how 3" blocks created about 4" of lift, I will explain... If you take a 3.5" diameter chunk of HDPE round stock and set it on top of the Sporty's body mount, the block will sit ON TOP OF the body mount. It will not fit in the mount's recess, which is about 3/8" deep. And if you leave the top of the block flat and lower the upper body bushing onto it, you gain at least another 1/4-3/8" of lift because the bottom of the bushing is designed to sit in the body mount's recess. But wait, you can also get even more lift if you add a layer of outdoor matting to give the self-lubricating HDPE some traction (so it won't slide on the body mount)... and then add a few extra layers of matting to "shim" the blocks that were cut to different heights - you know, to bring them all to a semi-uniform level. Yep, all that can give you an additional inch of lift! <img src="/forums/images/graemlins/notooth.gif" alt="" />

So once that stunning-epiphany smacked me into a prolonged state of "what the <img src="/forums/images/graemlins/ignore.gif" alt="" /> was he thinking", I decided it would be easier to scrap the body blocks and start from scratch <img src="/forums/images/graemlins/angry.gif" alt="" />. Fortunately, there's an industrial plastics supplier in the area. And I was able to find 7 blocks of Acetal (Delrin) round stock (3" diameter) in the scrap bin, which were cut to 3" lengths (all uniform). I only needed enough stock for 6 blocks because the front blocks will be replaced with steel tubing (so I can mount the bumper). And the nice lady working the service counter was kind enough to let me have all 7 for $50 <img src="/forums/images/graemlins/smile.gif" alt="" />. That might sound like a high price. But these are Acetal blocks (the generic form on Delrin), which is stronger than HDPE or UHMW... and more expensive ($56/ft of acetal, $28/ft of HDPE and $16/ft of UHMW). And they were already cut to a usable, UNIFORM size. So I only had to do some simple "machining" to prep them for the install. That said, here's the "photo essay" of the process...


Here are 6 of the blocks (the 7th was held in reserve, just in case something "bad" happened <img src="/forums/images/graemlins/scared.gif" alt="" />). I have included one of the lift blocks that came with my Sporty, for reference.




After marking the center of each block (both ends), I used a 2.5" hole saw to cut a groove in the top-side of each block. The groove was cut to about 1/4" deep. I used the groove to define the edge of the recess to be cut in the top of the block - to receive the base of the body bushing.



I used the hole from the center-bit of the hole saw as a starter/reference-hole for drilling the bolt hole (using a 7/8" spade bit). I would have liked to have drilled the hole a bit smaller. But 3/4" was the next-smaller bit in my box, which was a just a little too tight for the extension bolts that were used with the original lift. And I had to reuse them...




Next step - cut the recess. I did this using a $10 trim router I found at an auto parts store. A 3/8" carbide-tipped double-flute straight bit was used to cut the recess at 3/16" depth. I probably should have used a 1/4" bit because the cheap trim router didn't have a lot of horse power... Oh yeah, it only cost $10... <img src="/forums/images/graemlins/rolleyes.gif" alt="" />




The last step was to taper the base so it would fit in the recess of the body mount. That was easy to do using the router armed with a carbide-tipped 45-degree chamfer bit. I set the depth-of-cut just deep enough so the base of the block would fully-seat in the recess. I did this step with my router table. But a trim router would do the job well.




Installation was relatively-easy. I used my floor jack with a stack of 2x4s screwed together for a lift-block to lift the body from the side. If the lift-block is long (3-4 ft), it will allow you to lift the body without bending the undercarriage. And that seemed to be much easier than lifting the body from the front and rear, as I've seen described in other body-lift "how to's". Here are some pics of the blocks installed...














I must say that I'm very happy with the fit - it's tight. And the black acetal looks much better than the white HDPE. I did add a "donut" of non-slip material (shelf liner) between each block and the body mount (acetal is also a self-lubricating plastic). Oh yeah, after machining, the final lift was reduced to 2-5/8". But that's fine with me. I think 3" (or 4") is a bit excessive because it stresses the brake lines when the wheels hang (especially the front). And there were also issues with the shift-lever on the transfer case (which I had fixed once... hopefully I won't have to fix it again). Honestly, it doesn't look much different with a 2-5/8" lift. The good news is that many of the "dimensional issues" have been fixed by using UNIFORM lift blocks. So I hope to get busy mounting bumpers soon enough. And best of all - its easy to fabricate your own lift blocks with a router, drill (drill press is best) and a saw (though I lucked-out with the pre-cut blocks)... <img src="/forums/images/graemlins/kewl.gif" alt="" /> <img src="/forums/images/graemlins/cheers.gif" alt="" /> <img src="/forums/images/graemlins/patriot.gif" alt="" />