Gear Blanks

After all that geary theory, it's time to get our hands dirty again. This week I've been making the gear blanks. I had previously started the sun gear blank because I needed to machine the main bore before I built the wheel up, All that remains is to machine the special key way that locks the gear to the front hub.

These pictures illustrates the key way, 

a tapered key fits into the shaped key way and is 

drawn up the matching taper on the hub by a locking screw. 

The original that I measured came apart very easily and has obviously been apart before as the tapered key and screw have both suffered at the hands of an enthusiastic hammer owner. The key (pardon the pun) to getting this kind of interface to work successfully is to have very close tolerances and as it turns out I had two attempts at the tapered key before I was happy. I may need to make another after everything has been hardened and plated, the tolerances are that tight.

The first job is to drill a hole that just grazes the edge of the bore 

and then countersink the outer end for the locking screw to locate in. 

I actually used two end mills for this job rather than a drill.

The next job is to flip the sun gear over and mill the back of the gear 

from the hole into the bore to create the key way. 

Note that the plug to bolt the gear to the vertical slide already 

had a recess machined out. This cut has to be at exactly the right depth.

Then we can machine the key itself, first job is to drill and tap

 a 1BA hole up the centre of a length of barstock. 

The original really was 1BA, I measured it very carefully.

Then without removing the work from the chuck, remount the chuck 

on the dividing head and mill away the excess to form the correct shape.

Finally, mill the 4 degree taper, this is where the size become super critical. 

With such a short taper, if the key is too tall you can't assemble it 

and if it is too short the key bottoms out as it is tightened.

Next make the locking screw, this is just simple turning and threading with two slots milled at opposite edges to adjust it. Of course, I also needed to make the special tool to do the adjusting...

Finally we can test the assembly of the lock.

Then I just need to make the blank for the planet gear, which is also just straightforward turning at this stage. All the fiddly stuff comes later.

Gear blanks ready for the teeth to be cut.

In other news, last weekend we had a local steam extravaganza at Steam Scene. I took the kids and we had an excellent time. A particular favourite being the miniature train rides which seemed to go almost to Christchurch and back. I was examining the gearing (for topical reasons, you understand) on a traction engine when the owner appeared and asked if I was "Claudia's Dad". It transpired that our respective daughter's were friends. During the course of our conversation, the geared facile came up. I enquired where she got her casting done locally and was referred to a small, local Christchurch foundry that should be able to help. I took my patterns and a photo of a geared facile around on Monday lunchtime. Well, again, it turns out we have mutual friends and had attended many of the same events together, we just hadn't met yet. The upshot is that my parts will be cast in steel and will be ready next Friday. I'll be sure to let you know how they turn out.

In more other news, On Sunday afternoon I helped an excitable, young Tinkerbell build her faux pathracer in my workshop. She arrived laden with Jaffa Cakes (I don't do this for free you know) and we proceeded to prep the frame before using vast quantities of my spare parts. Two of her chums from the local tweed riding scene, Dylan and Pete, also arrived and helped out. We finished it off, sans brakes, and she was able to ride it up and down the street before heading home very happy. She has since added some brakes. Tweed Pete also gave me a recommendation for a local gear cutter. I'll give him a ring tomorrow.

Spoke Flanges part 2

This week I've been drilling and tapping some holes, quite a lot of holes actually. Which in itself is an interesting question, how many spokes does a geared facile have? There doesn't seem to be an easy answer. I've conducted a survey on my own original sources which includes original photos, catalogues, adverts and machines that I know have original equipment. I've disregarded restored bicycles where I either don't know or suspect that the equipment is reproduction. Front wheels can have 50, 56 or 60 spokes with 50 being the most common, rear wheels can have 24, 28 or 30 with 30 being the most common. Also bear in mind that wheel sizes varied, with the front wheel offered in 36", 38" and 40" throughout the 5 years of manufacture, The rear wheel size varied with age, earlier bikes having a smaller rear wheel of 22", later bikes 24". I don't yet know if the rear wheel size varied with front wheel size. The machine I am copying has 40" front and 24" rear wheels with 60 spokes front and 30 spokes rear, this is a pneumatic bike though and Ellis & Co. may have felt that the new fangled tyres required a  stronger wheel. I have decided on 50 front and 30 rear, which is a common combination, it also has the advantage that both wheels have the same spoke spacing at the rim. Aesthetic reasons and all that....

So the next question is what gauge are the spokes? Fortunately this is handily stamped on the flanges.

60 x 13 gauge spokes. 

The remains of the original spokes measured 0.093" x 56tpi they are also (fortunately) straight gauge with no butting. I have made butted spokes before but it adds a considerable amount of time to a project. So all I need to do is get some 13 gauge wire of a decent tensile strength and roll some 13 gauge threads on one end and head the other end. But what thread do I use for the tapped holes? 13 gauge spokes are a very good fit in #3x56 UNF threaded holes. For the record 14 gauge spokes are #2x56 UNC.

The first job is to make a mandrel with a keyway to securely hold the flanges whilst I drill and tap them.

I used a chunk of aluminium just because I happened to have it lying around. 

The important bit is to not take the mandrel out of the chuck after it has been turned, this ensures that the flanges will be true to the register and the holes will all be centred on the flange with no wandering. The dividing head is invaluable for the drilling and tapping operations.

First centre drill the flanges, then drill the through holes and finally tap the threads.

The second flange requires a little thought since the spokes holes must be timed correctly relative to the first flange, spoke holes falling between opposite spoke holes and all that. I've been indexing at 1/25 of a circle for the holes, so If I advance 1/50 and then continue at 1/25 this will all work out.

The rear wheel flanges were easier when I realised that I didn't need to make a mandrel at all since these flanges are not keyed and the holes are aligned at the time of assembly.

First bore through for the cones and then cut the mounting recess 

and the inner profile. I've tried to catch the shower of chips 

that comes off when machining gunmetal, it really is spectacular.

At this point I can remove the chuck with the work still 

mounted and remount on the Myford dividing head and drill...

 ...and tap the holes as for the rear wheel.

Then remount in the lathe and cut the outer profile and part off.

Next week I'll polish and nickel plate all of the hub components made so far at which point I can then think about rims.

In other news, today is the last day of summer. We haven't had much of a summer at all really and the mornings are decidedly cooler and definately darker. The commute this morning was quite chilly.

My daughter celebrated her birthday on Sunday, she invited a gaggle of school friends to come around and practice make up and do some shouting and other such stuff. My son and I decided to go out for the evening and watch one of the star wars films in 3D which was wasome. He wants me to make a podracer in my shed next. I bet they don't use 13 gauge spokes.

Front Wheel Spoke Flanges - part 1

Well I was wrong, it turns out that you can cold set 4130 tubes. You just need a long enough lever. The bearing housings are now almost perfectly aligned and even though the original error was small, it would have bothered me. I'm like that.

So this week I've been making a pile of very expensive swarf chips by machining a large chunk of gunmetal into slightly smaller spoke flanges. As I expected the gunmetal machines beautifully. At one point, when I was removing a large volume quickly, I had a fountain of chips spraying off. Unfortunately, I was machining in short sleeves and lightly toasted my left arm.

Starting with this billet, amongst other things, I made some...

...very expensive chips.

The first step is to thin the billet down to the correct outer dimension 

and bore the centre deep enough to make two flanges at one chucking.

Aside from my own measurements of originals it is interesting to compare

against the actual specifications from the literature of the time.

This is from 1887, a few years earlier than the original I am copying.

Next step is to bore the recess for the inner bearing race, this is the final part of the

labyrinth seal. Also face the outer edge of the flange at the correct spoke angle.

Then I needed to machine the inner profile of the flange, 

this had to be done carefully to be an accurate facsimile of the original. 

Also round off the top of the flange and machine a groove to locate

 the spoke holes in the centre. Finally part off and make the twin flange.

Next job is to remount each flange the other way around and 

bore the slight recess for the hub and round off the shoulder.

And finally, I get the opportunity to use the keyway 

slotter that I bought years ago and have never used.

The completed flanges with a length of key steel used to lock them to the hub.

I'm pleased with the appearance compared with the original.

Next week I'll drill and tap the spoke holes.

In other news, we have much sadness now that my parents have gone home. To take our minds off this we accepted an invitation to a veteran car event here in Christchurch. We had a decent 50km ride on the Saturday which was hard on the way out and then tailwind home, magic. The following day we assembled in the Botanical Gardens in period costume and had a posh picnic. Several members couldn't resist showing off for the tourists and performed penny farthing trick riding on one of the lawns. My Son was over the moon when he was offered a ride in an 1899 steam Locomobile in beautiful condition.