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.

Tuesday, 9 April 2013

A Riveting Post

The promising start to the saddle making last week didn't end well. I got the saddle top cut out, creased the edge, cut out the vent and then screwed up the rivet holes. I tried to punch them through from below after marking the positions. The punch tended to wander a little going through the thickness of the leather. The result is that whilst the holes are lined up correctly with those in the cantle plate and the nose piece, the upper sides of the rivets do not line up perfectly on the top side of the saddle. Since I have plenty of leather, I chalked it up to experience and made another. Tim has told me how he makes his holes so this time should be better. Also the second time around I made a few changes to how I stretched the leather top over the block to make the process slightly easier and quicker. I didn't work, it took me longer. For some reason the second top is softer than the first one, this one marks very easily whereas the first one was quite hard, I'll carry on though and see how it works out.

Right where did we get to?

First thing is to cut the leather off the block and make it the right shape.

I asked Tim about how to get both sides the same and unfortunately there is no easy way. Fortunately the facile I am copying still had the original saddle leather so I was able to accurately copy the shape and dimensions.

Next run an edge beveller around the inner edge to produce a smooth chamfer.

Then dampen the leather slightly and run an edge creaser around the outer edge to
 produce a line. This requires care, particularly around the tight bend on the nose.

Then bevel the outer edge.

Then cut out the vent from the top of the saddle. 

I took measurements, photos and a rubbing from the original since I felt this was important to get the dimensions correct. Tim advised that I get a clickers knife to cut the vent. I failed to find one anywhere but I discovered that there is an easily available Stanley knife blade (5192) that is very similarly shaped. The blade is reasonably easy to control and well suited to this job. As an aside, Mr Middleton recently introduced me to diamond files. They come in at least three grades, the finest being of most use to me. I've been using mine to touch up high speed steel cutting tools in the lathe. I recently spotted a curved one and bought it with a view to honing these hooked Stanley knife blades. It turns out that I can get the Stanley blades sharper than new with it, scalpel sharp in fact, I'm most impressed and if you don't already own one, go and get one immediately if not sooner.

Next make the rivet holes. 

This time I took Tim's advice about the rivet holes and managed to get them in the right place. The upper sides need to be countersunk to allow the rivets to lie flush with the surface so that clothing doesn't catch on them.

Dye all the cut edges and when dry burnish to a gloss finish, 
I cheated and used my polished mop to do this. 
Lightly toasted leather doesn't half smell bad you know.

Then comes the bit that I was nervous about, the two creases along the sides of the saddle top. These two lines have to be the same and are done freehand with no guides. I marked the positions lightly with pencil to make sure they were symmetrical and then just went for it. I don't have the correct creasing tool for this so I smoothed the edge of an old fashioned steel tyre lever and used that.

The leather has to dampened again before creasing the line.

Then rivet the top on using copper rivets. I had just enough genuine 1/2" Brooks rivets left over from a previous job. Tim advised that these rivets are too large to be historically correct so I turned them down in the lathe until the heads were 3/8" as per the originals. I hate turning copper, it's so soft that it's hard, a little like sweeping water into a pile. Or herding cats. Or something.

The five holes that I had drilled, the three in the nose piece and the two new holes in the cantle plate were easy to rivet since I had sized them to the rivets. The four original, outermost holes in the cantle plate were larger and I couldn't get the rivets to hold properly and consequently had to remove them and have a little think. Of course I had no rivets left so I had to make some more from some much larger copper rivets used to hold truck brake shoes on. My Father has a large pot full and I stole some many years ago. This time I made some little copper washers and used them as roves to hold the tension on the rivet whilst I headed it, this worked out well. I'm not completely happy with the leather top, I think I could do better but I'll ride it and see how it works out in use.

The saddle is still not yet complete, I'm having a makers stamp made but it hasn't arrived yet. I'll post a photo when I get it.

I can now sit on the bike, and very comfortable it is to, which means that I can now make the handle T grips and get them at the right ergonomic angle. More later.

In other news, this week we've had a bad dose of redundancy going around at work. It's interesting that when the list of redundancies is announced all those on the list become work place pariahs. The fortunate few remaining in employment no longer make eye contact or want to linger and chat. They may catch redundancy you see. For those readers familiar with the traditions of English pantomimes.

"Where's my career"?

All together now children, "It's behind you".

 To my surprise, I am one of the lucky few to be kept on. I've had a lot of time off this year to look after my children and I didn't expect to survive the cut.

I explained what redundancy meant to my children and shortly afterwards they demonstrated their clear understanding of the nature of the problem by playing 'redundancy touch' (no returns allowed). This game is very similar to 'cheese touch', 'Jamie touch' or 'double dog poo touch'. Jamie being an unfortunate boy in my son's class. Children can be so pleasant.