(This article was written for a driver on the CD-L who needed to reshape a cart shaft. My Dad was a boat builder and I grew up working in the shop building wooden boats with steamed oak frame ribs. I’ve reshaped/untwisted shafts purchased for cart construction, and this is the method I used.)
From your original post, it sounds like the bend missing is the front one closest to the cart. I’m going to give you instructions based on that assumption. If I’m wrong, just alter the instructions for the next bend forward, flipping everything over and putting the blocks on the outside instead of inside. If the bend is the one at the tip, you can slide a pipe over the tip of the shaft to extend it and make the bending easier. Make sure you put something between the pipe and the shaft where the edge of the pipe will cut into the shaft. It’s important to do this without leaving any unsightly marks or scars. If the shaft is bent up, you can use a sawhorse and a bucket of rocks instead of worrying about blocks and clamping. You still have to use the same boiling water, towels, plastic bag and tape part, so read on!
When you do this job, you can repeat this as many times as you need to get the whole thing exactly the way you want. If you DO repeat it, make sure you support the bends you’ve got and want to keep, as steaming them will allow them to straighten if not supported. Also, and this is VERY important, make sure you keep everything you’re working on on a flat plane or you will steam a twist into your shaft which is much harder to fix (fixable just a LOT tougher).
After stripping off all hardware, leather and finish from the section you want to steam, wrap the section in terry cloth. The more layers you put on, the more you’ll be able to hold the wet heat up against the wood. Make sure the terry cloth extends beyond the “to be bent” section in both directions. Tape the terry cloth on. How you tape it on is at your discretion. The more tape you put on, the more securely the terry will stay, but if you overdo, you’ll have trouble getting the terry soaked with water, so use common sense.
Next, you need to lay the garbage bags over the section to be soaked. You have to do this before you start applying blocks and leverage, because once you have the block(s) up against the terry, you won’t be able to get the plastic in between. Make sense? You want the garbage bag(s) arranged so they will hold the water in, so make sure there’s no seam or opening on the section you’re bending. You’re, in effect, making a kiddie pool for the part of the shaft you want to bend. Once the blocks are in place, you’ll tape the ends of the bag to the shaft (VERY snuggly) and pour boiling water in at the middle, with the garbage bag(s) keeping the water from draining away to the ground.
Okay, now we come to the blocking. Depending on the amount of bend you want depends on how you do the blocking and the cargo strapping. You need to plan for a little more bend than you want as the wood will straighten slightly (only slightly) when the blocking is removed after the shaft is cold. The best course of action is to prepare your blocks using the one correctly bent shaft as a prototype. You want your blocks to fit that curve. Whether you can scrounge the blocks you need or have to have some cut, you have to have the blocks match what you want the shaft to do. They are your template you’ll work from.
Place the blocks against the inside of the shaft according to where the bend will be. Place the 4×4 against the blocks with the same amount sticking past the point of the bend and put a cargo strap at each end. This whole process, from this point on, will be easier if you have the shaft resting on a relatively flat surface (make sure it’s something which can stand boiling water without breaking or marring) – the back of the pickup or a picnic table or the like. This will allow you to position the blocks without having a handful of people to hold them in place while you start wrenching things around.
Just before you start to tighten the cargo straps (if you have bar, “C” or pipe clamps the right size, they’ll work also) to pull the shaft into place, prepare your boiling water. It’s best if you have enough to do the entire job without stopping to heat more water. More water is always better than not enough water.
With the cargo straps snug enough to hold everything in place should it get bumped, pour the boiling water into the garbage bag(s). Be careful about getting splashed, or dumping any water on yourself or your helpers.
With the towels soaked and steaming, close up the garbage bag(s) and proceed to tighten your cargo straps (or clamps) until the shaft is very snuggly up against the blocks. Watch to make sure you haven’t incorporated any swoop or twist into the bend. Don’t make the clamping too tight, or you will have permanent block marks on your shaft. The terry cloth wrapping of the shafts will protect them to a certain extent, but if you get too vigorous with your clamping, there’s not enough padding to compensate, so be careful.
Walk away and leave it alone until it’s cold. Once it’s completely cold, undo everything and see if you like the result. If you don’t, take the plastic off, replace the terry with dry (it takes too much boiling water to get the cold water occupying the already used terry hot enough to do the job) and reblock to fine tune.
Once you have the shape you want, let the wood dry completely, sand lightly, refinish and reapply your hardware and leather. I’ve attached a drawing of how the blocking and strapping (clamping) needs to be arranged.
Let me know if you have any questions or if I didn’t make things clear enough and I’ll do my best to clarify and answer your questions.