Sunday, 19 September 2010

This week, was mostly about not succumbing to temptation. I took a day out and drove around a little, caught up with a few people and bought a brace of Suzuki Bandit lower frame rails, pictured to the left. These are bolt in to make engine removal either easier or possible, I'm not sure which as I've never taken the engine out of a Bandit. The point is the the half lap frame splices will fit together. OK, there's a round hole that won't quite accommodate the 17mm AF nut that us Europeans like to use for 10mm thread bolts, but that's nothing that a simple spacer wouldn't sort out, or possibly some Japanese style 14mm AF 10mm nuts. I'm leaning towards making some long nuts from hex bar and turning one end of them round on the lathe to fit in the recess in the splices.

The temptation I was avoiding was to start work on the frame braces. I have the tube on the shelf, and I'm happier messing around with frames than I am with anything else. As it was I managed to restrain myself to cutting some of the splices free from the Bandit frame rails and making a start on cleaning them up. The two that are bolted together are from the front and rear of the rail, and have a shorter "tail" than the other one which is from the tube that runs across the frame. Not having inspected any of this too closely before buying the parts, I had been expecting to get four half splices from the two rails, and not six, and I'd also imagined that the tails of the splices would be longer. Having acquired a half dozen half splices, it makes sense to think about using one pair on a cross brace in the same manner as the Bandit does. Of course, while the OD of the Bandit and BMW tubes are the same, as yet I have no way of telling what the wall thickness of the BMW frame is, though the R65 frame is purportedly lighter than the frame for it's larger brethren, so possibly has thinner wall tubing.

What I needed to be doing was finishing off the seat hump. Although I'd made the risers for the seat hump to attach to, and indeed drilled some mounting holes, I hadn't addressed the problem of attaching the front of the hump to the riser. Accessibility was the problem, with the nuts tucked up inside the "U" section of the seat riser, and the battery living right next to that. I don't like using captive or welded nuts on frames as it's always a problem if they strip or seize, so I made a pair of small aluminium blocks instead. These were sized to sit up in the "U" of the seat riser, and drilled and tapped to accept a M6 x 1mm bolt.

As well as that, they were drilled through the other face to accept a split cotter pin. The idea being that they were positioned under the seat riser, and the cotter pin passed through some holes drilled in the riser to retain them in place, allowing the seat hump to be placed and the front two mounting bolts fitted. While it's a fiddly thing to make, if the thread ever strips, or the bolt ever seizes and snaps off, removing the split pin will let the block drop out and it can either be repaired or replaced without any damage to the frame. It might sound like over thinking the job just a tiny wee bit, but I absolutely loathe having to sort this sort of thing out when it goes wrong in service be cause someone, somewhere, was too cheap, or too lazy to come up with an answer that had a less troublesome failure mode. Probably a bit of a hobby horse of mine really...

I also made some inroads into making the seat proper, and gave some thought to how that was going to be attached. I'm making it with 1/4" of the steel folded back on itself at the edges, the idea being that the vinyl can be glued and tucked back behind the folds, and then they can be tightened up with a rubber hammer trapping the vinyl in place. Well, if the seat's removable, it ought to look tidy underneath too. Hopefully, I'll get the seat base made and mounted in the course of the week, which will mean that the following week, I can give in to my baser desires, and start bending some tube.

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