I actually finished this some time ago, but for whatever reason, forgot to upload some photos of it.
So here’s the finished machine:
A shot of the adjustor mechanisms. The lower one is RHS-in-RHS, tensioned together with teflon lined, steel gib plates. The upper wheel is mounted eccentrically on a bushing. Wrenching the handle 180 degrees moves the upper wheel about 20mm upwards. The system is stiff enough that it doesn’t move when you don’t want it to, but not so tight that you need two hands to move it.
A close up of the area where the gibs are tightened. The countersunk screws in the middle don’t do anything other than to stop the gibs from falling out if you take out the unbrakos that actually tension them. They don’t actually need to be countersunk, but I had a bunch of them lying around.
The upper wheel is flame hardened 4140.
Each support for the lower axle can be adjusted independently to make sure that the rollers are touching in the middle and not near the sides. If need be, I can take off both the clevii and rotate them 90 degrees. I wanted to make sure that I’d be able to make a roof panel with this, so I wanted a few tricks up my sleeve if I ran out of throat.
There’s a tension plate on the front that takes the reaction force from the lower adjustment screw- which I still need to put a kick-pedal-wheel-thingy on. I welded a rack to put the rollers on the front. The rollers are all case hardened EN36A. I posted drawings some time back.
The rear wheels are steerable to make the thing easy to move around. The steering pivot was made from a couple of old brake caliper brackets, a big bearing, some scrap steel and one of those trolley things you can buy at Bunnings for 20 bucks.
I looked around for some thin sheet metal to have a go with, in the end all I found was this piece of 1.6mm stainless. Shaping this was very hard work- it’s much thicker than what I plan to actually use the wheel for.
Photo from recline position.