Thanks Dandeman,

Basicaly, I need to figure out what volume of air is needed to go from 10 to 20 psi for all four tires. Then, using the known volume of my rear bumper, I need to calculate what pressure the resultant volume required would end up at in said bumper. Finaly, as you stated, I then multiply that pressure by the area of my end caps to make sure I`m not exceeding safe limits. The only problem I can foresee is if the volume needed would result in a tank pressure that might be difficult to achieve with a regular compressor. I can set my shop compressor to 150 psi but what if I need 200 psi? I`m sure I could figure something out.

Toughguy

Excellent work! You've got all the ideas in place that I have in my head but haven't got the tools and money to make it happen!


Any tips on repairing the fenders like I saw in one of the first few pictures? Looks like you did a few spot welds every couple of inches. Any tips you'd like to share?

Yes Adam, the trick is to make stitchwelds in a way that will not apply too much heat in one area because that will result in warping. Start welding in an area where the two pieces line up the best. While there is still heat in the area, the metal will be more maleable and thus you should be quick with the body hammer should the panels need some convincing. Then move to another area at least 3 inches away if possible and make your next spot weld. Continue in this fashion until your panels are stitched together every 3 inches or so. Now start over about a half inch beside the very first weld and continue tacking beside every successive weld so that heat buildup is kept to a minimum. Once this round of welds is complete, it might be a good idea to let the metal cool a bit. This is where you can go around with the body hammer to fit the panels where your next welds will go. The rest is pretty straightforward. Just keep going around making your welds until you have filled the spaces between them to about a half inch or so.

The next step is to grind down the welds but you must also be careful not to introduce too much heat into your work. For this I use a 4 1/2 inch angle grinder with a sanding disc of about 60-80 grit. Heat buildup is not as big a concern when grinding a part that has a bend in it like the door pillars or the lip below the rocker panel so don`t worry too much there but if we are dealing with a flat panel surface, grind the weld in the same manner as they were welded. Do a few in one area and move to another area away from the first, letting the metal cool before going back to a previously grinded area.

Idealy, you would have made the patch carefuly to minimise the amount of filler needed to smooth things afterwards but this is not always the case. If you have to build up an area by more than 1/8 inch, use short strand fiberglass and finish with body filler for a smooth surface. Any small pits that remain are easily repaired with finishing putty and sanded smooth prior to priming.

In the case of my 4Runner, I knew the paint was going to take a beating so I primed top to bottom front to rear with an epoxy primer/sealer. This type has better adhesive properties. (like epoxy paint for the concrete floor of your garage) It also seals better and has a tougher finish that is impervious to moisture unlike a scratch filling primer that can retain water and allow the paint to bubble after only a few years. This primer still needs to be sanded to achieve a super smooth surface but your topcoat will still stick to it very well even if it is not. This is handy for areas that are hard to sand or impossible to reach.

I hope this helps you out a little. I did work in a bodyshop one year to pay for university and there I learned quite a bit but I am far from an expert so if my techniques seem incorrect please feel free to tell me.

Toughguy

Looking back on it now, do you think the negitive arch in the rear spring pack in this flexing pic was a clue to your future axle wraping problem? You know, hind sight is 20-20 and all. <img src="/forums/images/graemlins/smile.gif" alt="" />

Yes and no mt_goat. I readily achieved the flex I was looking for but I made some mistakes along the way.

Mistake #1 was not adding a load leaf to the rear spring packs, as required by Downey in their instructions. The reason the Downey springs are relatively inexpensive is because they don`t come complete. This is not indicated in the catalog or in their ads. The All-Pro springs are looking good at $280 US now!

Bad move #2 was using degree shims to level the truck out. It was only 1 1/2 inch but it gave the axle some more leverage on the springs. I might have been OK had I not done this because the original angle was lower and chances are the u-joint would never have bottomed out without it. In my defense, degreeing the axle so that the u-joint at the diff is level (or just a few degrees below level) IS the correct way to do it when you have a CV joint at the T-case. By comparison, if you have one u-joint at each end, you should rotate the axle so that the u-joint angle at the diff matches the one at the T-case. This is so the eliptical paths the u-joints travel get cancelled out by each other. (as long as they are in phase)

Despite those two mistakes, I could have avoided damage had I fabricated a control rod that would connect the top of the rear diff to the frame crossmember to prevent axlewrap. Why didn`t I do that? Lack of time. Plain and simple.

So in retrospect, yes the suspension was TOO flexy but the negative arch is not what should have clued me in. I designed the suspension the have the springs as flat as possible so that I could have as much suspension droop as compression. From what I have learned, this is the correct way to design a suspension for rockcrawling and generaly slow trailriding. If I had been designing a suspension for high speed whoops and sand washes, it would have much more compression travel than droop and the shock dampening would be much higher.

Here is a pic of what will become my torque rod. It`s just a farm tractor implement lift rod thing. It cost $20 from Princess Auto. I will lengthen it and make some mounts.


I will rebuild it, I have the technology!

Toughguy

Oh thank you, I've been looking for a thingy like that. Farm tractor implement lift rod thing huh, is that Princess Auto just in Canada?

Hehe. Yeah. 23 locations across Canada!
Princess Auto

I`m sure you yanks probly have similar kinds of parts stores in the US.

Toughguy