Backbone

After the successful experiments of last shedweek, I can now do something about the current invertebrate nature of my geared facile. Time to make the backbone.

I'd been recommended to go and see Ron at Sherlock Rings & Flanges about bending my chromoly tubing for me. After explaining what I wanted and providing a drawing of the exact radius I required I left the tubes with him, he told me to come back the next day. Now, carrying a length of 1 3/8" tubing around on a motorbike is not easiest thing in the world and everyday I ride the motorbike to work is a day I don't cycle. I was a little sceptical about the promised time frame but I took the motorbike again the next day and turned up as requested. Well Ron was a man of his word and had already bent the tubing to my exact measurements. I think the project had tickled his fancy a little, we have several acquaintances in common and chatted for ages before I had to leave. If you ever need tube accurately bending, I recommend that you go and see Ron. As it turns out I asked Ron to bend the 7/8" tubing for the rear forks at the same time.

Bent round tubing before rolling.

My elliptical rolling mill needs to be bolted down the the deck and with the dark evenings now, I had to wait until the weekend to use it. The rear forks got rolled first, everything went smoothly and by cutting the tube in the middle of the bend I can produce both fork legs.

The elliptical fork legs, over length at this stage.

Next came the backbone, and time to see if my calculations are correct. I'd had the tube bent to an inner radius of 475mm (18.7"). This radius is too tight to follow the 40" front wheel, I'm expecting it to open out to a radius of 20.75" when I roll it to the correct elliptical profile.

Rolling the backbone elliptical.

Conforming to the rollers.

The much larger tube, actually the largest I have rolled, was physically very hard to manipulate. The process went well and the final shape is spot on, an accurate ellipse and the radius is perfect. Mathematics is your friend.

The next job is to trim the straight part of the backbone to the correct length so I can taper it. I've created a little jig that sits the wheels at the correct wheel base, I can then offer the backbone up and jiggle around with angles and clearances etc.

The front forks have just been rotated out of the way to allow clearance for the too long backbone.

The taper on the backbone is quite slight compared to a penny farthing, the final dimension being 1 1/8" at the rear fork crown.

Once again a little calculation on how much of a sliver

 to remove and then get busy with the hacksaw. 

Where the backbone meets the rear fork crown, the tube has to be round.

This shape has to be corrected from the elliptical shape 

before it is welded, after welding the 4130 is too hard. 

The tube went into Christchurch on the motorbike to get welded up and as before I took it to Pete who again did a first class job on Tigging it up.

This weld bead still needs to be dressed off a little.

I confess to have a minor concern about durability of these split and welded 4130 tubes, I'm unsure if the welds will crack with flexing. Time will tell I suppose.

My next shedweek will be spent making the rear fork crown from a billet of hot rolled 1045 steel.

In other news, my lovely wife has purchased a new pair of winter boots. This time I accompanied her so she had no need to hide them in the wardrobe. She was going to buy a ghastly pair until I suggested an alternative at twice the price, immediately earning myself bonus family credits. Family credits are hard won and I'll need to think carefully about how and when to cash them in.

In more other news we've had a nasty little flurry of aftershocks this weekend, starting with a magnitude 5.2 on Friday afternoon that almost had me clearing my nether throat [1]. After getting shaken out of bed twice last night by the house getting all jiggy with it, I gave up and read a book instead of trying to sleep.

Also, I've munted my back again. I have a long term disc injury and it's bloody well popped again. I wasn't even doing anything heroic at the time, merely emptying the washing machine. Based upon previous experience, My family have now got between two weeks and two years of extra grumpiness ahead. Ironic really when you consider what I've been making this week.

[1] apologies to Sir Walter Raleigh c/o Mark Twain

Elliptical tube rolling - part 2

I need to make some more elliptical tubing. You may recall my initial success with the front fork legs some months ago. I've now started thinking about how I'm going to make the backbone and rear forks, both of which are elliptical. However, the backbone and the rear forks are bent elliptical tubing which adds a new dimension to the problem. Do I roll the round tubing into it's final elliptical shape and then attempt to bend it or do I do it the other way around and bend the round tubing and then roll it into an ellipse. Well, the answer is obvious when you consider why the tubing is elliptical in the first place, to increase the resistance to bending in the plane of the major axis. So I need to bend the tubing and then roll it to profile. This sounds simple but consider what will happen to the radius of the bend when it is slightly flattened, it will tend to straighten out, but how much?

I've developed a simple mathematical model to predict how the radius will change with increasing eccentricity from round to squashed flat. I'm pretty confident that it will be reasonably accurate for relatively low eccentricity and then become less accurate as more metal distortion takes place at high eccentricity. Theory is all well and good but I also want to test it with a real world example. I want to see if it possible to roll a bent tube without it bending in another plane for example.

I'm going to coin a new word at this point. The word is 'Shedweek'. A shedweek is the amount of time a person can spend happily occupied in a shed during the course of a week before other family members begin to pass unkind comments. Shedweeks are clearly variable in nature. I would strongly suggest experimenting in the lower range before venturing into the more advanced upper reaches.

I've spent my shedweek making some new rollers for my rolling mill, I have one pair for the backbone that roll from 1 3/8" tubing and another pair for the rear forks that roll from 7/8" tubing.

Rear fork blade rollers on the left and backbone rollers on the right.

Let the testing begin.

Start with a bent length of 7/8" bicycle frame, in this case the "loop" from an old ladies loop frame. 

The frame had no merit other than as a donor for some suitable bent tubing.

It died for a good cause.

Then progressively squish the tube in the rollers, in practise I found that 

the bend in the tube just followed the rollers beautifully, it wasn't an issue at all.

Frequently remove the tube, measure the major axis and draw along the radius to measure later. 

This will enable me to see how well my mathematical model behaves at different values of squishedness.

The final shape is a nice even, flat ellipse. 

There is a very slight twist, as before, in the straight section, but I'm not worried about that. 

As it turns out my model was accurate to 98% for the eccentricity I require in the backbone. This means I can calculate the initial bend I need, which works out to an inner radius of 18.7" (475mm). Then when I roll the backbone elliptical, it should straighten out to a final radius of 20.75" (527mm). I'll cut some of my remaining tubing, after Mr. Middleton helped himself, and take it to a company that specialises in rolling large tubes next week.

The rear forks are mostly straight with a sharp bend at the very end, I have a simple tube bender that can cope with this size so I may do this bend myself. 4130 is so tough though that I may reconsider.

In other news, last Sunday was Mothers day here in NZ. This had a seriously negative effect on my shedweek but I'm not about to complain. The children had made various shoddy cards and paintings of the sort that make mothers all misty eyed and emotional, but no presents. We have a rule in our house regarding presents to each other. As a normal man, I don't really do hints or observe subtle suggestions. Instead I ask for a clear, concise, written list of possible presents stuck prominently on the fridge door well in advance. I know that this may possibly remove a certain amount of surprise and romance from these occasions but it also dramatically reduces errors and improves efficiency.

So I took the list and the kids shopping late on Saturday afternoon because I'd forgotten all about it until then. We managed to get all the items including the lingerie which I'm also not going to complain about. These lists always feature marzipan. I should know this by now, but marzipan, real marzipan is hard to get in NZ. It is sometimes available in some supermarkets and I generally stock up when I see it for future list fulfilment purposes. Sadly, this time, my magic cupboard could not help and we had to run around like idiots to find some.

In more other news, I failed to complete a bike ride for the first time in years this week. I was riding home from work and had got to the road works where the new development is being built to the west of Kaiapoi, the one near the cemetery (the dead centre of town). The excellent road workers had left an unmarked, unlit trench across the shoulder. The night was dark and wet with thunder and lightning (very, very frightening) in the distance and I only saw it at the last second. I got the front wheel over it but the back wheel slammed into the far edge and popped the tube and dented the rim. Of course at this point the heavens opened and my wimp glands came up again. My lovely wife came and picked me up after I'd telephoned her on one of these new electric "mobile phone" things. They may catch on you know.

Tyres, Teeth & Tuhoe

I've haven't had much time to actually do much this week although I have spent time working out how to make the backbone, more on this later.

The tyres are red, they are not pink darling.

Rob has fitted the tyres to my wheels, or more accurately, he has fitted the tires to my wheels since he used the American system rather than the English one. The English system uses a spiral of wire moulded within the rubber. The tyre is cut too short for the rim and and inch or so of the spiral exposed on either end of the length. Then by twisting the rubber the wrong way for the same number of revolutions as coils are exposed on the spiral, the tyre can be joined and the spiral screws into itself and the gap is closed. The loop is then stretched over the rim and is held in place by tension only. This is usually OK for normal use but recent batches from the UK have been a bit crap and Rob has stopped using it. This is what can happen when crap rubber is used, the Rider is Jack Castor from California, he was quite seriously injured but is now fully recovered. This happened on an NZ tour a few years ago, Jack was descending from the Otematata saddle between Omarama and Kurow, notice the 'loop' forming in front of the wheel before it all goes pear shaped.

In contrast the American system uses a rubber extrusion with an empty hole through the middle, the rubber is cut too long for the rim and wire fed through the hole. The wire is tensioned on a special machine in such a way that the excess rubber gets bunched up evenly around the wheel whilst leaving a short section of each end exposed. The two ends are trimmed and silver soldered together. When the jig is removed the gap closes up tightly. Rob has been sourcing his rubber directly from the states and the stuff he now uses is of very high quality, it wears well on our rough roads but is still grippy enough to be safe in the wet.

I painted a couple of pinstripes on the rims before the rubber was mounted. I've been collecting images of original Victorian pinstripes for years now. Every time an original machine gets restored another unique reference point gets lost. But don't get me started on that. It is surprising how gaudy some of the Victorian machines were. We tend to think of the Victorians as very straight laced with stiff upper lips and little skirts around table legs lest the men think unseemly thoughts etc.. Actually, I'm not sure that the table legs thing is true but it's a good story. The point remains though, that to our modern eyes, some of the pinstriping and painted decoration seems way over the top. The double pinstripe on each rim is common, I've seen it on many original machines.

Tax free teeth?

Also this week, I've got the gears back from the gear cutter, he has done a fantastic job and I'm very pleased with the result. I will not say if he waived the GST when I waved cash, that would be rude. They need to be lapped to polish the faces but there is also a lot of machining to be done on both gears anyway. I'll oil these and set them aside for the time being as I focus on the rest of the frame so I can get the bike sitting on it's wheels.

This week I'm going to make some more rollers for my elliptical tube rolling mill, I need to make two sets. One for the elliptical backbone and one for the rear forks. The facile I am copying is a later model and has fully tubular fork blades either side rather than the half open style of earlier machines.

In other news, the family was at a loose end on Saturday so we took a trip on the MV Tuhoe moored at Kaiapoi.

MV Tuhoe.

It was fantastic in that old fashioned, slightly naff way. Sunday's trip coincided with the 'Super Moon' so the tidal river was very high.

Oh, that's super.

I particularly liked the way we were allowed free access to the engine room. If you find yourself at a loose end, I can highly recommend it, just wrap up well if an Easterly is blowing.

The engine room complete with engineer complete with engineer's cap.

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.

A lecture on gears

Pay attention at the back, there'll be an exam later. I'm looking at you Middleton.

I've needed to learn a little about gears and gearing theory in order to reproduce the geared facile. This has all been a lot of fun (we may have to disagree on this point, I'm a mathematician and my idea of fun may differ slightly from the norm) and I need to share my findings. I'm not going to go into great details but a Google search will yield many results on this stuff if you are interested.

Cycloidal or Involute?

The first thing to determine is the type of gear profile, there are two contenders: cycloidal or involute. Historically, cycloidal gears were used almost exclusively up until the late 19th century when the new fangled involute profile quickly became the standard. Cycloidal gears are still traditionally used in clock making and have a devoted following. Involute gears have certain benefits, such as a tolerance to incorrect gear spacing, that makes them attractive to industry. It is easy to distinguish between these profiles by eye.

I've been unable to find an absolute date for when the involute profile was introduced, all references I've seen suggest the end of the 19th century. Of course this is the exact time frame when the geared facile was being produced.

Examination of the original gears clearly suggests that they are involute, 

which means that Ellis & Co. were at the cutting edge of the current technology in 1887.

So now that we have established that the gears are involute, we need to calculate the size of the teeth. For gears in a gear train to mesh accurately they need to have some commonality in the tooth size, this is known as the Diametrical Pitch (Pd), which is the ratio of the number of teeth to the pitch diameter. All involute gears with the same Pd will mesh accurately.

All original faciles that I have measured have 37 teeth on the sun gear and 18 on the planet gear. I stand to be corrected on this but the literature of the day backs this up. The final gear ratio in this simple epicyclic train is calculated as follows:

gear ratio = wheel size in inches x (driver + driven)/driven

with a 40" wheel, 37 tooth driven sun gear and 18 tooth driving planet gear we get a gear ratio of 59.46" or the equivalent of a penny farthing with a 59.46" wheel. Ellis and Co. offered the geared facile in three sizes 36", 38" & 40" and claimed gear ratios of 54", 56" & 60" resp. The actual calculated values are 53.51", 56.48" & 59.46" resp, it seems that Ellis & Co. liked to keep things even at the expense of accuracy.

Note that it is very important that at least one of the gears has a prime number of teeth, this ensures that the gears will wear absolutely evenly. With a pulsed power delivery such as a bicycle, if this were not the case, spots of high wear would rapidly occur where the same tooth was repeatedly under peak load.

So how do we calculate the Pd to be used? We have the number of teeth and we also have the centre to centre distance for the gears, from the literature and also from my own measurements I know that the gears ran on a 3" crank.

Centre distance = ((driver teeth + driven teeth)/2)/Pd

gives us a Pd of 9.16666 teeth per inch

which is unfortunate since commercial gear cutters are always sold as whole numbers (and the odd half size). If I use a Pd of 9, I get a centre to centre distance of 3.056", a little too far off for comfort. Fortunately gear cutters in metric countries use an alternative to Pd known as the module.

Module = 25.4/Pd

so we need a module of 25.4/9.1666 = 2.77

metric gear cutters are available in fractional sizes, the closest to 2.77 being 2.75. If I use a module of 2.75 my centres work out to 2.977", less than half the error of using Pd 9 cutters, also remember that tolerance to incorrect spacing that involute gears have?

The last thing to calculate is the outside diameter of the gear blanks, this is given by the following formula:

OD = (teeth + 2)/Pd

this gives sizes of 4.222" for the sun gear and 2.165" for the planet, which match closely to my measurements of the originals.

gear cutters are available in sets of 8, with a different cutter used for a range of teeth

#8 12-13 teeth
#7 14-16
#6 17-20
#5 21-25
#4 26-34
#3 35-54
#2 55-134
#1 135-rack

So I need to buy cutters #3 & #6 for mod 2.75. The only other variable to consider being the pressure angle which I won't go into. As it happens it was cheaper to buy a full set rather than individually.

I had originally intended to cut the teeth myself but now that I have the cutters in my hand, I've realised that my machinery simply isn't massive enough for the job, these are big teeth. Teeth are usually cut at one pass and require an immensely stiff setup to cut the bigger sizes. I'll contact a local gear cutter when I finish the blanks off. I'd rather get a good job done than screw things up.

Has anybody managed to get here yet without falling asleep?

In other news, I've been for a gentle 50km ride at the weekend. My first since the Le Race debacle. The only bits that still hurt are two fingers on my left hand and my right knee. My right knee was OK after the ride, not great but OK. I still haven't looked at the crashed bike yet. For the ride I selected a late 1940's Raleigh Record Ace (RRA), this was for several reasons: it's very comfortable and I still have a pair of shoes for the toe clips that aren't munted from a recent crash.

A late 1940s RRA. Red, of course.

Not disco slippers.

In more other news, Mr. Middleton and partial family have been for a visit. I was unable to provide an earthquake which was a source of some disappointment. However Mr. Middleton was able to console himself by stealing some of my 4130 seamless tubing. I think he is going to use it to make something from this book written by somebody or other.

Also, Tinkerbell wants to come and see my magic cupboard. Actually, she wants help building up a faux pathracer and I happen to have lots of bits that she needs. Sadly, she intends to paint it british racing green!

Seriously though, there is only one colour suitable for bicycles and that's red[1]. We all know that.

[1] Unless it's black.

Oh, and I lied about the exam.

Wheel Building

It's surprising how little fettling you can do with the tops of four fingers missing (see below), however, I've tried to be a brave little soldier and this week I've built the wheels up. If you recall, I'd been itching to do this but I had to wait for the paint on the rims to cure properly. Lacing the rims to the hubs is easy and just requires poking spokes through the rim and screwing into the appropriate hole in the hub.

I started with the rear wheel as it is smaller and I can fit it into my wheel truing jig. 

Radially spoked wheels go from loose to very tight in about a turn and a half, so it is important to take it easy when starting off otherwise the rim may well be straight but not very round. The strength of the hollow steel rims means that there isn't a great deal that can be done about larger bumps and kinks in the rim, these have to be worked around as best you can. Also the wheel has to be trued so that the outer, hollow well where the tyring sits is true, not necessarily the sides or inner edge. 

Spoke grip in use.

The spoke key used is a special little clamp that is tightened onto each spoke in order to turn it. This takes a little time as you can imagine and means that the process cannot be hurried. These spoke grips are not uncommon and can be found relatively easily. They were made in quite a few variations and it is fun to collect as many types as you can. Not many people outside of this antique cycle world would know what one is used for but since they are small they are thrown in a drawer and forgotten about. They seem to have been made in large numbers as I have seen them advertised for sale in catalogues as late as the 1910s, though not for their original purpose. I made a small run of replicas some years ago and I've been using them since in preference to my originals.

Abingdon King Dick Spoke Grip advertised in 1912. This is the same Abingdon Works Co. that made the Abingdon ball head on the geared facile. I suspect that spoke grips were made in vast numbers and these advertised here are New Old Stock rather than current production.

Before I can lace the front wheel I need to machine the bore of the sun gear, this is the main gear that mounts to the end of the live axle. When the wheel is built it would not be possible to offer the axle up to the lathe to check for a nice fit.

This really does have to be accurate as all the torque to drive the machine

 relies on this fit, sloppiness would soon cause excessive wear and failure. 

Checking the fit.

Actually, I got a bit carried away and made the entire blank rather than just the bore. I like turning and the time just seemed to disappear. The gear is made from 4140 as it will need to be hardened. I may carry on and finish it off before I do anything else, I don't like leaving things half finished.

The front wheel was laced first and then trued by installing into the forks and truing in situ. 

Now that both wheels are complete, it is possible to get an idea of the scale of the bike by comparing it to other contemporary designs. It really is tiny.

As compared to a contemporary bicycle...

...and as compared to a contemporary safety.

In other news, Le Race didn't go exactly as planned. I'd stayed the night in Christchurch so I could just ride around the corner to the start in the morning. I got a good position on the grid and I didn't need a pee as the race started so pretty good so far. The usual high speed sprint down Colombo street (on wet roads) was followed by the first climb up Dyers Pass. I felt great and was pretty close to the pointy end of things, I was climbing well and riding comfortably when I got a rear wheel puncture. Glass, it's always bloody glass in Christchurch and this was on a new Vittoria open Corsa, my all time favourite tyre. I changed the tube and blew it up with one of those new fangled carbon dioxide cylinders but by this time I'd lost minutes and hundreds of cyclists had gone past me. Starting off again in my haste, I left my glasses at the side of the road. About now I realised that a decent time was not going to happen so I decided to just enjoy the ride. As I was now towards the back of the race amongst the slower riders, I found I was having to overtake everybody to climb at my comfortable pace, this is not too easy with large bunches without crossing the centre line and I was held up in the early stages. My bunch going across the flats was only about 8 riders and with most people having a go at the front we were still pretty slow. Le Race only really starts when you begin the climb up to Hill Top,

I love this section of the race and made up a lot of time on this hilly bit. 

As we approached Akaroa, I was catching riders I'd been with at the start, then came the final descent into Akaroa. Long Bay Road has a bad reputation as a dangerous descent on a bike. True, it starts above 600m and less than 6km later is at sea level. True, it has a crappy surface. True, it has many sharp bends, some of which are off camber, some tighten up on you and some are covered in gravel. True, the exposed saddle often has a nasty cross wind to catch you out.

Now, where Long Bay Road rejoins the main Christchurch Akaroa Road, the race route turns hard left and goes down the Old Coach Road. This road is very steep and requires care, unfortunately I was descending like a complete twat and lost the front wheel on the first right hand bend. Remember those wet roads? The slide took ages and I had time to consider my impending doom before I comprehensibly grated myself down the coarse chip seal. The marshalls were alerted by following riders and I was in the back of an ambulance in just a few minutes. When doing these kinds of rides, I make a point of thanking the marshalls as I ride past, it's volunteers like these that make these events possible, just something to consider. Anyway, the marshalls and the St. John Ambulance guys were fantastic. Roughly an hour later, I gingerly rolled down the remainder of the hill and crossed the finish line under my own steam to sympathetic applause.

Ouch.

Later as Sue & Colleen from the Akaroa Health Centre stitched me up, I reflected on how lucky I had been not to break anything. Now 10 days later, I'm well on the mend although my right knee will be a long time healing as I sanded it right down to the bone. I haven't looked at the bike yet, I daren't. It's my favourite 'modern' bike, a 1996 Argos built for me from the first batch of Reynolds 853 with lovely clunky 8 speed Campagnolo Record components. I think it's mostly OK. My beautiful new disco slippers are ruined as is my helmet. The clock read 4:11 as I crossed the line, my bike computer said 3:13. I think without the incidents, I'd have done the ride somewhere between 3:00 and 3:10, not too bad for a old, fat retrogrouch on a 'vintage' bike. I'll have to do it again next year. If my lovely wife will allow it.

Speaking of Spokes

This week I have been repeating myself. I try hard not to do it but as I get older I find that it's an undeniable truth. I think I'll start paying the kids to poke me when they catch me doing it in public.

But I digress and that's not what I mean anyway. This week I have been making the spokes which involves a huge amount of repetition, none of it is hard or arduous but it's easy for the mind to wander when doing something for the 100th time. A wandering mind and a large hammer is not necessarily a good combination I find.

The 13 gauge spokes are made from 2.4mm (0.094") wire. The threads are rolled on which raises the crest of the thread and increases the final diameter to 0.099" (#3 x 56 UNF).
The donor wire I have used is 308 stainless steel TIG welding rods. I'm somewhat reluctant to use stainless as it isn't an original material in use in the 1880's, However in my defence, I have scoured NZ for high tensile wire in the correct size and failed miserably. It is very easy to get 2.5mm wire but this is too large for the thread roller and the threads produced are then too big. That 0.1mm does make a big difference! If I do find a source in the future, I may revisit this. for reference, most modern stainless spokes are made from 304 stainless.

The first step is to put a head onto all the blank pieces of wire. I haven't done this for a few years and it took a bit of practise to get good at producing a decent shaped mushroom. The wire is clamped between the two halves of a die with a few mm extending. This is struck with the hammer to form a head into a slight countersink in the top surface of the die.

Now having previous experience of this I was able to make a suitable die to overcome some of the issues. The first one is that the wire has to gripped very tightly. I made my die from a length of angle iron I found in my magic cupboard. By clamping a sheet of paper between the two sides of the die before drilling the hole at size, the final hole will be a very tight fit when the paper is removed. The hole should be as long as you can drill it to increase the friction of the clamp. The second problem is that as you are hammering away, the die will get deformed. I've found I can get about 20 spokes headed in a mild steel die before it needs cleaning up. It is possible to make a die from tool steel and get it hardened to prevent this deformation, these do last considerably longer but can also shatter.

With no tool steel in the cupboard, I've solved this problem 

by making a throwaway die with a series of holes, 

when one gets too munted, start to use the next one along.

A few mm extend out of the die...

...which is then clouted with a big hammer.

I found I was unable to cold head the stainless steel, I needed to heat up the wire extending out of the die with a torch before hitting it with the hammer. This is not ideal as the resulting heads will be weaker. Time will tell.

The raw spoke heads out of the first die.

The heads at this point are all over the place, functional but very irregular and just a bit crap. Mr Middleton would have been fine with them but my OCD (according to my lovely wife) made me improve them.

I made another die from some tougher 4140 steel, this die is not split but has a slightly larger hole and a countersink (actually both sides were used since it still got munted from the hammering).

The second die.

I then poked the spoke through the hole and held the head up to the 

side of the bench grinder. By twiddling the spoke around in the hole 

I was able to make the heads round (rounder anyway). 

Then resting the die on top of the larger vice the heads are hammered down 

into the countersink, producing a far more even, consistent head. 

Next step is to calculate the length of the spokes using a bit of trig. I did this twice on separate evenings to check that I'd got it right before I did any cutting.

Finally roll the 13 Gauge threads onto the other end and we're all done.

I didn't think I had a 13G thread roller but my magic cupboard produced the goods once again.

The finished spokes.

The rims have finally been painted, but with the colder weather, the paint is not drying as well as I'd like. I'm itching to build the wheels up but I need to be patient.

In other news, my lovely wife is to have some fairly major surgery next week. Obviously, I am incapable of looking after her and the children unassisted so my Mother-in-Law is coming for a month to help out. We are all very excited about this as you can imagine. I have been given a very long list of "stuff which must be done". I suspect that if I haven't got the wheels built by then the paint will be fully cured by the time I do get around to it. We will see.

Le race is on Saturday. I realised last night that drinking beer and watching the TV does not constitute "training". I'll do 20km tomorrow night after work, that'll do.