it looked like this at the hoisting end
and like this at the cantilever end.
Another of these, by now tedious, plates was made up to provide a mounting to bolt to the rim
and to which a square tube was welded to provide a mount for the winch and up we go . . .
Mounting the winch this way serves three purposes:
1) with the winch on the wheel and facing up the cable can be run over the pulleys and back down to the wheel which halves the amount of pull required compared to mounting the winch on the chassis and looping over the pulley or mounting the winch on the top tube and pulling up directly,
2) the winch is easier to mount on the wheel, especially when it is on the ground, rather than on the top beam, and
3) when turned over it provides a direct pull up for the motorbike.
Then the problems started . . .
First the top beam bent. The winch is quite fast and stops and starts suddenly with a brake to prevent unwinding when turned off. This jerky start means that the load can easily double with a bounce and thus overload the beam.
Next I had a look at the cantilever end - I couldn't believe how far the roof was deflecting upward - close to 20 mm - especially with the bouncing.
Then of course it was quite easy to swing the wheel out to clear the bolts while it is down near the ground. As it gets closer to the lifting beam, due to the lack of clearance above it, there is only about 50mm free cable. No way to swing in the 100m required to get the rim over the bolts.
Nothing for it but . . . to start a new lifting beam.
This one has a couple of spacers to lift it a bit higher.
Also the wall thickness is double!!
Whenever you weld something across a beam like this the welding contraction causes the beam to bend toward the weld ending up looking like a banana. Not a good look so under the piece to be welded is a packing strip and each end is clamped down bending it backwards before the welding starts. There is no real way to calculate the amount it will bend when welded because of the different heat and metal mass involved in each weld but after a while you get a feel for it, and this felt about right.
At the cantilever end it was extended to the next roof cross beam to decrease leverage and to give two more fixing points. If you look really carefully you can see fancy milled "feet" of 10mm thick bar to spread the load and the end of the tube chamfered closed as before.
At the other end, again with more acetal rollers, a very simple roller system was made to allow the whole top end to roll backward and forward the required 100mm to get the rim over the mounting bolts. The plates for the rollers are just roughly cut at this point to make sure it works. Later I will round the ends and trim it all up. The plates come apart easily and pack into a very small space. It is not intended to leave this part up there. Hopefully I will seldom (read "never" please!!) have to do this too often "in the bush".
The clamp is also a temporary item to prevent it all coming down on my head. It will have a "proper" retaining system now that I know it all works. Because of the increased strength of materials and more rigid mountings there also seems to be no bounce when stopping and starting.
It worked so well I put the wheel up and down a couple of times in about 10 mins and with no more real strain than holding down the control button.
The only real tedious part now will be disassembling it all and priming and painting to prevent rust and then reassembling.
Still, all in all, "Much happier now Jan."
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