Thursday, 18 April 2013

A Gripping Tale

As promised last time, I've spent this shedweek making some T grips.

 This is the one remaining grip on the original, the second one was missing.

Held in place by a single screw.

The originals are made of buffalo horn, this material although not easy to get, is still available. These days it comes from farmed Asian water buffalo and there are a few companies that deal in it. These horns are mostly hollow except for the very tip which is solid. The handles on antique bicycles are at the upper end of the size range of these solid tips and only the biggest horns will do. That's the first problem, you're paying for trophy horns. The second problem comes if you live in a country like NZ that has very strict import laws on animal products. I'm confident that it would be possible to achieve but I only have limited time available in my lifetime and I don't particularly enjoy fighting with bureaucracy. I'm not complaining about the MAF laws by the way, I just can't be bothered dealing with them.

I've spent some time researching valid historical alternatives. It seems that the Victorians used a great variety of materials, some ethical and some decidedly not. I think that getting some fresh ivory into NZ would cause even more problems, not least for the poor elephant. Lignum vitae is an interesting wood you know, it's also massively over harvested and now virtually extinct. However, I like to recycle and reuse stuff and about a year ago I saw a set of lawn bowls in an antique shop. Bowls of a certain age (mine are 1959) are made of lignum vitae and are just big enough to get some handles out of if you use a little ingenuity.

A bowl from 1959, shortly before it met with a saw.

First, sand off the coating to determine the grain direction. 
Then chop into pieces to get the blanks out.

Mount in the four jaw and bore the tapered hole through the grip, 
by taking the chuck off with the work still mounted I could repeatedly check for a good fit.

Flip through 90 degrees and drill and tap the hole for the retaining screw. Amazingly, this stuff is hard enough to take a screw thread, it was also unmarked by the jaws of the chuck. It machines beautifully by the way, with a lightly perfumed odour, the wood is very oily and the cut self lubricates. You get no problems with machining the end grain at all, it appears to be uniformly dense. I experimented and sure enough this wood sinks in water, decidedly so.

The blocks I have are only just long enough to get the grips out of so I need to glue some temporary stubs to either end so I can turn them. Gluing lignum vitae seems to be a topic that raises as much debate as greasing/not greasing tapered bottom bracket axles. In the end I rough sanded the ends for some mechanical interference with the glue, I also wiped with a solvent to remove the surface oil. I then glued using Araldite, a common two part epoxy.

I could then mark and centre drill each stub so I could turn between centres.

Turn to shape until nearly parted off then remove. 

Snap the glued end off and hand file the end profile.

Then place on the handle bars and sit on the bike. Rotate until comfortable, mark this position and make the hole. Finally run the tap through the grip and the bar.

The last thing to do is to file the ends of the bars to match the profile of the T grip. 

The grips are held very securely, there is no play or movement at all. I'm pleased with the result, I now have 3 of the 5 contact points finished, the remaining two being the 'pedals' on the end of the levers which will probably be the last parts to be made.

The total weight is now 34.75 lbs (~15.75 kg)

I think I'll make the brake hardware next, I'm itching to get started on the driving gear but if I do that first then I'll just want to ride it and then rush the rest of it.

In other news, I have been gently reminded that I have not yet finished the deck I promised that I would build for my lovely wife back in the spring. In truth I haven't even started it yet. She pointed out that even Mr. Middleton has managed to build a deck in the meantime. I'm going to have to get on with it, sigh.

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