Wednesday, 29 June 2016

Royal Enfield Chainset part 1 - Forged Cranks.

One of the things that has always bothered me about my Royal Enfield is the chainset. The early girder frame Royal Enfields have a distinctive chain ring.

A distinctive chain ring, yesterday.

My lovely wife's 1903/4 ladies girder frame has the same design albeit in a much small size, it's just that you can't see it in the enclosed chain case. I think it's got either 38 or 40 teeth but without taking off the chain case I can't easily find out. My racer has a suitably manly 52 tooth chainset of the correct design but the crank arms are mismatched, the left being a very early Williams of the same length. The right hand side has also been repaired at some point. The chain ring and the crank arm are both Royal Enfield but clearly didn't start life together. Either the ring or the crank is a replacement with the old ring being cut off and the new one welded behind it.

The weld is not a thing of beauty. 

This means that the chain line is slightly off being pushed inboard by the width of the chain ring. The cranks are also monstrously long at 7" (~178 mm) between centres, this was fashionable at the time but my knees have never thanked me for it. I much prefer cranks in the 165-170 mm range.

The solution is to keep the old cranks safe with the bike but make a new pair for riding purposes. The thought of owning a bike that I can't or don't ride is anathema to me, this is why I'm going to so much trouble making new parts for the bike. As I mentioned last time, when I emigrated from the UK about a hundred years ago, I bought everything with me, even rusty old crank sets. This was fortuitous as decent quality old parts are very hard to find in New Zealand. From the hoard I selected a pair of 6.5" (~165 mm) Williams C34 cranks. They had rust pits and not much chrome left and were the ideal donors.

20 minutes in HCl acid to remove the chrome and rust and I could begin to start work. First I need to remove the spider, this is swaged on over a toothed interface.

I milled off just enough material to allow the spider to come off 
and still allow me to room to mount the new chain ring. 

The Williams date code stamped into the cranks identified them as 1956, 50 years after the Enfield. Cranks had changed little in that half century but a few minor details needed correcting. The Williams cranks had a few weight saving bevels cut into them that the Enfield did not, these needed to be filled with weld and then re profiled back.

Weight saving bevels...

...not saving weight.

The shape of the cranks has also subtly changed over the years, earlier cranks have a much more abrupt transition between the pedal boss and the shaft and between the axle boss and the shaft. This is easier to remedy as taking off metal is always easier than putting it on again. Half an hour playing with some files and the transitions are now of the older Edwardian profile.

unmodified on the left, original in the middle and re profiled on the right...

...and the same at the pedal boss

Then the edge bevel needs to be replaced...

... to make it appear original.

At the same time, I got rid of the last of the nickel plating. Hydrochloric acid makes short work of chrome but won't touch the nickel substrate. This is very handy is you want to make something look older than it really is by exposing the nickel but means that you have to remove the nickel by other means.

The original cranks bear the legend "ENFIELD CYCLE CO LTD TOUGHENED CRANK" stamped into them.


This is quite a lot of letters to get lined up properly so I made a jig to make life easier, the idea being that I just need to worry about the spacing. The cranks on my lovely wife's Enfield read the same but have the word "THE" prepended. I have to assume that mine are correct for my year so I'll be missing off the initial "THE".

Stamping guides.

I couldn't do the Co. & Ltd. exactly as per the original. 
In years to come somebody may wonder about that.

The last stamping is the left and right hand thread around the pedal holes. Again I needed to make a little jig to guide the punches, this took a little thought to get something that worked well. I can't stand doing mono buttocked jobs, I'd much rather spend the time and do it right. But that's just me being all OCD I suppose.

Left Hand Thread.

Next week I'll make the chain ring. I've made a few chain rings before and while not difficult, they do take a bit of time if made by hand. I'm sure I could get the plate laser or water cut in a fraction of the time and if I was making more than one I'd probably do it. However including the time taken to draw up the chain ring in CAD, I'm pretty sure I could have the one ring smashed out by hand in the same time.

In other news, we've bought a rowing machine. To say that my giant son is into rowing would be like mentioning that I quite like cycling a bit. Being winter here (the solstice was just a few days ago) there is almost no rowing on the rivers at the moment. He does go and use the "ergs" at his club for the social aspect but living in the middle of nowhere makes it quite hard to do too often. Also my lovely wife and giant daughter have expressed interest from a fitness point of view. A very short conversation with my son about what to buy and a short time later we have a Concept2 Model E in our living room. Apparently, there is only one erg to get if you are serious about it. I've also been using it myself although quite timidly as my back does not like new things that involve bending too much. We shall see how it works out.

Sunday, 19 June 2016

Royal Enfield Handlebars

As mentioned last time, I've been making some handlebars. Recall that when I last rode the bike, my awesome sprinting prowess bent the handlebars at the stem.


I took a good look at the 'bars and decided that the best course of action was to do nothing to the original set and make a new pair of facsimiles. This way I can keep the original 'bars with the machine should I ever choose to sell it but still be able to ride the machine with gusto and without fear of personal injury.  The original 'bars are of a very fine gauge tubing and are extremely light. They are also rusted through from the inside and after close inspection, I'm amazed that they didn't break rather than just bent. That's one of the advantages of steel components though, sudden catastrophic failure is rare as you tend to get heaps of audible warning before a part fails.

I'm not going to make mine as lightweight as the originals, mainly because I happen to have some chromoly bends left over from the facile project that I can reuse. These are in a thicker gauge which is probably no bad thing. As I discovered when getting tubing bent previously, it is very difficult to get compound bends made in close proximity to each other, at least it is if you want high quality mandrel type bends. So I'm going to fabricate the compound shape of the bars using simple bends joined together. By playing around with the length of the straight portions I can, to a degree, control the style and shape of the final result. I've made some hollow internal lugs from 4140 chromoly, these are a tight fit inside the tubes and when welded up can be made invisible.

Internal lugs ready for assembly.

The inverted front brake lever uses a Bowden cable that runs through the handlebar, this is a very neat feature common to many Royal Enfield models of the early years of the 20th century. My wife's 1903/4 model has a very similar arrangement. The lever is sized to fit inside the thin gauge tubing not my thicker stuff. for this reason I need to chop off the last 2" of the right hand 'bar and replace it with a suitably machined adapter.

Note the last two inches of the right hand handlebar are replaced with an adapter.

I asked Pete to weld up the various parts...

...and as usual he did a wonderful job. 

After normalising the welds, it is an easy job with a file to make the welds disappear. 

I know that filing welds materially weakens the joint but my experience with the facile and the design of my internal lugs means I'm comfortable doing this. I'm confident that they won't be breaking any time soon.

I had previously made the central lug to hold both sides of the handlebars and join them to the steering tube. I got carried away when I machined it and forgot to take any photos of the process.

The steering tube is interesting for several reasons. Firstly the design, notice that the headset, original to the bike, is not a headclip but a conventional design with an adjustable race and a locking headnut,

Steering tube and wedge.

this design means that the steering tube is clamped to the fork via an expanding wedge, the design of the wedge is slightly different to later designs but the idea is exactly the same. I believe that 1906 was the only year that this headset was offered, the years either side used the more standard headclip design. I'd love to know more if anyone has any information. I have a copy of the 1907 catalogue and what I think is the 1905 catalogue but no 1906 edition. I'm lead to believe that the patent number on the steering lock is from 1906. Secondly the OD of the steering tube is not 7/8" as you would expect, 7/8" tube doesn't fit into the forks. I needed to machine the OD down to 0.865" from 0.875" to get it to slip in nicely. Also the ID needed to be thinned to suit the wedge. I didn't want to have to modify any of the original parts that bolt to the handlebars, the facsimile handlebars must be made to fit the original parts.

Next job is to clamp everything in the right places and silver solder the lug. Notice the board that everything is zip tied to, it's the same board I used when I brazed up the facile handlebars. Spooky.

Ready for silver soldering.

Finally I just need to clean up the joints a little and check for fit in the bike, I'll plate them when I plate all the other parts I'm working on at the moment.

The shape and dimensions are extremely close to the originals, I'm quite pleased with them.

Don't you just love the Edwardian racer look?

In other news, I'm having some other frames professionally painted at the moment. I'm slowly getting my list of projects down so that I can start work on the racing penny farthings. These frames have been on my list for ages and I want to get both bikes back on the road before I start. More later.

Tuesday, 24 May 2016

Cinq5 Shift:R versus Gebla Rohbox. A long term review.

It shouldn't be this hard. Really. You may recall my mention of my new bike some time ago. I had the frame custom made around my existing Rohloff hub purchased new in 1999. Since I'm a nerd, I keep detailed records of my cycling activities and I could calculate how far I've ridden it in the intervening 17 years. I could but I can't be bothered at the moment. Shifting a Rohloff on a bike with drop handlebars is not an easy problem to solve if you don't like grip shifters. This page details a myriad of ways to achieve it but the majority are the most awful and non ergonomic cludge ups I could imagine. The Rohloff was originally intended for mountain bike racing but the actual market where it excels appears to be loaded touring and expedition bikes. I think I'm unusual in that I still use mine on a mountain bike, albeit a slightly different one. I'm a roadie, always have been. There I've said it in public. With my long term back injury, I simply can't do anything too technical off road. Not because I'm technically unable but because I can't afford to come off. Where I live we have lots and lots of gravel roads and forestry tracks. Not always open year round due to fire risk but there are always really good off road rides to do. The off road stuff is actually better than the road riding with far more interesting routes and much bigger climbs. This is the reason for the new bike, it's my go anywhere bike. And since I ride the road a lot, I wanted a similar position to my road bike(s) but tweaked a little to handle off road.

Cinq5 Shift:R cable box shortly before I killed it.

You may recall that I was an early adopter of the Cinq5 Shift:R shifters for the Rohloff. I installed them and mentioned at the time that the jury was out on them. I really wanted to like them but I had reservations. In summary:


  • Ability to shift one or two gears at a time
  • Lightweight
  • Beautifully made.

  • Tricky to setup so that you could both up shift and down shift 2 gears at a time
  • Fragile
  • Shifting from the center of the bars meant that you needed to be seated to shift. Not always the case off road.
  • The tiny ratchets often slipped and failed to engage and change gear.
  • Doesn't like being fully submerged. On my bike the cable box hangs down low and I often ride through fords and rivers that cover the box. This made the slippage worse until I could clean out the box when I got home. Towards the end, I often finished rides being unable to shift any gears.
  • The shift levers require high force to change gear. This despite my best efforts using high quality cable and sensible routing. I always grind cable ends square. I have a slightly dodgy left wrist that makes it harder to change gear on that side.
  • I used the 31.8mm diameter levers. To mount these required a handlebar with a wide central section of this diameter. My 'bars are 46cm Salsa Cowbells and even with these I wasn't able to mount both levers at the same angle as the cable outers would foul each other where they exited the levers. Not a big deal, but things like that irk me.
  • The design uses the inner cable the wrong way round, the nipple is at the cable box, which means that you can't use an alternative lever without modification.

Eventually one of the tiny pawls inside the cable box simply broke (the up shift pawl) and stranded me in a high gear. Fortunately, I wasn't too far from home and I could get back easily. As a recent convert to Strava, I can say with a high degree of accuracy that the Cinq5 system only lasted 1406 km. That's pretty poor. Since the levers were new, I contacted the dealer and eventually received a replacement cable box after a 2 month wait. The levers were unmarked and in as new condition.

Cinq5 Shift:R cable box shortly after I killed it.

In the meantime, I investigated alternatives since the bike had become my favourite and I'd miss riding it. The Gebla Rohbox looked like a valid alternative, so I ordered one from SJS cycles to try out. I've used SJS sporadically over the years to buy various, otherwise hard to get, parts. The Rohbox turned up 4 days after ordering (!) not bad when you consider that I live in the middle of nowhere and that it's about as far as you can get from Somerset before you start going back again.

The Rohbox was on the bike later that same day.

In summary:


  • Very simple mechanism made from robust parts
  • Uses the inner cables the right way round. ie the nipple at the lever. This means you can use pretty much any pair of levers to change gear.
  • The maker isn't a faceless organisation but is a bike maker from Germany called Georg. I'm an early adopter of his design and my unit shipped with springs that enabled it to shift two gears at a time. These didn't work well and Georg contacted me and sent out replacement springs and two new shift cables at his cost. These transformed the feel of the unit and the single gear change now has a nice feel to it. Georg is a really good guy and is happy to stand behind his product.
  • When used with ergo levers or similar, the handlebars are very clean.
  • Very easy to set up.
  • Although not sealed, the simple, robust construction is impervious to frequent river dunkings. I opened the box after having completed the same mileage on the Rohbox as on the Cinq5 system before it broke. There appears to be zero wear on the component parts.
  • I'm tending to change gear more often with the controls at my fingertips.

  • Can only shift one gear at a time. 
  • Relatively heavy compared to the Cinq5 cable box. If heavy means robust then I'm not complaining too loudly.
  • Larger than either the Cinq5 or the original Rohloff cable box.

Initially, I set up a hybrid system using the Cinq5 levers and the Rohbox. This set up worked pretty well but still had the issues with poor ergonomics for gear changes when standing and due to my left wrist issue. I used the bike like this for a few months until I found a set of second generation Campagnolo Record Ergolevers with aluminium levers. They were only made for a couple of years in the late 90s and are much sought after. I'm pretty much allergic to carbon fibre on my bikes, I can't really explain why either, just one of those things. I've rebuilt lots of Ergolevers over the years so I know my way around them pretty well and have a draw full of spare parts. I knew that I could use the levers pretty much as is and they would work but could be better if I modified them internally. I wanted to remove everything on the thumb, downshift side of each lever. I also wanted to lock the up shift lever firmly to the cable pull. The up shift lever has a pawl that locks into a ratchet depending on which of the gears you are in, it requires a few degrees of motion before it engages and I wanted to remove this motion to improve cable pull and the feel of the gear shift. The part I made simply replaces the front ratchet and is shaped very carefully to lock the lever to the pivot. With the thumb shifter mechanism completely removed, I simply needed to make a distance spacer and use a shorter bolt.
The modifications shaved a fair bit of weight from the units.

I'd already decided to ditch the auxiliary brake levers. I seldom used them and with the
Cinq5 gear shifters going at the same time it meant my bars would become much cleaner. 

The Cinq5 system used standard gear cable with the wires running length ways. Since the Rohloff does all its indexing in the hub this is unnecessary and I decided to try using brake cable outer as it is more flexible and may lessen the force required on the cable. I can feel a slight sponginess in the system as the cable compresses but combined with the longer shift levers on the Ergolevers, the force required to change gear is reduced. I can also change gear with my hands either on the hoods or in the drops. Finally, I can now change gear when out of the saddle...

This is the best gear change I've had yet on the bike, It's not perfect and it still has some shortcomings that at present I can live with.

  • I do miss the ability to shift multiple gears at once that the grip shifter afforded. Terrain can change quickly off road and I need to be vigilant. If I pause pedalling pressure momentarily, I can rapidly shift multiple gears by pumping the ergo lever, this works well.
  • I miss the ability to see which gear I'm in. In practical terms this means that the 7/8 8/7 change can occasionally catch me out again even after owning the hub for 17 years. It also means that I can try for a lower or higher gear and discover that I'm already in it.
  • The force required to change gear varies across the range, not all gears require the same input from the shifter. In certain gears, I can't recall which ones, this means that it is occasionally possible to shift two gears instead of the single shift that you wanted. I need to stress that this is an unusual occurrence though.
  • Errr, that's it.

I have no connection to either Cinq5 or Gebla and I paid full retail prices for both units with my own money. I have since sold the brand new, warranty replacement unit from Cinq5. It was a nice try, but simply not up to the kind of riding I like to do.

In other news, I've finally started work on my 1906 Royal Enfield that I broke the last time I rode it. The handlebars are the first part to get my attention, More later.

Monday, 31 August 2015

New Bike #2

I like epicyclic gearing, that's probably no great surprise to you given the original content of this blog. I have and ride examples of most of the exotic stuff that Sturmey Archer made in their heyday. These are the ones that collectors pay silly money for on Ebay. As an aside it tickles me that the ASC trigger featured on the Sturmey Archer heritage web page is one of my reproductions rather than an original. That's one of my early ones, note how the escutcheon doesn't quite fit the trigger body and that the detail is not an engraving. The internals were a perfect match with a genuine ASC trigger though. I sold these with full disclosure but it seems that subsequent sales weren't quite so transparent...

Let me know if you need one, I have a few left over. 

Given this love of the tiny whirring gears, I was hugely excited to learn of a new 14 speed epicyclic hub gear about to hit the market. Subsequently I became an early adopter of the Rohloff Speedhub, buying #1045 new in 1999. Rohloff have made over 200,000 since then. It has always lived on my mountain bike and has covered many miles with no real issues. The only time it let me down was when it lost its oil on the descent of Mount Ventoux in France. Now that was exciting, I can tell you. The oil seeped out of the hub and down the spokes and onto the rim. V brakes don't work well when liberally oiled. and 25 km up a big hill is not a good place to have it happen. The very early hubs had faulty seals that were replaced under warranty. I don't really do much actual mountain biking since I can't afford to come off with my back issues. Where I live we have lots of gravel roads that would be ideal for a new type of bike, a cross between a road bike and a mountain bike. Naively, I thought I'd invented the genre but apparently it's already a thing and they're called Monster Cross bikes. Not a cyclocross bike, that's different and very traditional with fairly skinny wheels often with tubular tyres. I mean a bike with all the advances of recent mountain bike technology but with a road oriented riding position complete with drop handlebars. And the Rohloff I already have.

Paragon Machine Works make Rohloff specific dropouts.

I wanted disk brakes as the technology has settled down since the early versions. My 1996 Ibis tandem was made with early Hope cable disks which whilst adequate simply do not measure up to the modern equivalents. My lovely wife and I took this tandem to France to watch the '98 Tour, the year of the Festina scandal. We rode it up and down the Col du Tourmalet and as a result I think I can say with some authority that modern disks are an improvement. We still have the tandem but these days it's mostly myself and my giant son that set Strava KOMs on it. He's an awesome stoker, he weighs nothing yet is unnecessarily tall and has a huge power to weight ratio. I ask for more power on the uphills and the machine lunges forward. One day, real soon now, he'll be thrashing me on two wheels. But I digress. The first job was to send off the Rohloff to the local NZ agent to get it converted to a disk brake version, this is an easy swap that simply requires a new endplate to mount the disk on and a new external shifterbox. Chris emailed me a few days later to say that it has arrived but with damage despite being well wrapped. The result was a very stressful 6 month battle with the courier company to get them to admit liability and pay for the damage. I'm pleased to say that I was successful but the original #1045 hub shell was damaged beyond repair, it's something that still irks me. The upside is that the replacement hubshell is bright red (naturally) rather than the original silver.

Mmmm. Shiny red...

The Rohloff doesn't have a great choice of shifters for drop handlebars, there are a few twist type shifters available but most solutions look like the most awful bodge ups. The new Cinq5 shifters looked just the ticket so ordered a set from Pure Sports.

Right lever for lower gears, left lever for higher gears. shifts two at a time.

Nice clean installation.

In the meantime I hunted around and engaged the services of a local NZ frame builder. I know, I know, I could have built one myself but I enjoy and admire craftsmanship from other builders too. I needed to provide all my critical dimensions and the family and I had a good laugh getting the measurements one evening. Having had a fair few frames made for me over the years, I've always known that I have relatively long thighs. Being such a freak means that I generally can't get my seat far enough back on off the peg frames. The brief was simple, full width 29er wheels, disk brakes, Rohloff hub, single chainring, 80mm suspension forks and obviously it has to be red.

When the frame arrived, I was like a dog with diphallia.

I'd been collecting all the parts required over the previous months and spent a happy day assembling it as follows:

Frame: CCC Columbus Xcr 29er
Fork: DT Swiss XMM 15mm axle
Headset: Hope mix 'n' match
Stem: Thompson 110mm -17 degrees
Handlebars: Salsa Cowbell 46cm
Drop brake levers: Tektro R200A
Auxiliary brake levers: Tektro
Seatpost: BBB carbon
Saddle: Brooks Cambium C15 (the new skinny rubber one)
Bottom bracket: Hope stainless steel
Chainset: 170mm Middleburn RS8-X type with Rohloff spider
Chainring: 38T Middleburn Mono
Chain: SRAM PC 870
Brake calipers: Avid BB7 road SL
Brake rotor front: 180mm Avid HS1
Brake rotor rear: Rohloff 160mm
Front hub: Hope Evo Pro 2
Rear hub Rohloff 16T
Rear skewer: 90's Hope titanium
Gear shifters: Cinq5
Rims: Stans ZTR Crest 29er
Spokes: DT black stainless double butted
Tyres: Continental Race King 2.2 tubeless using Stan's NoTubes system.
Pedals: old Shimano spds

I would have willingly given one of my testicles for a bike like this when I was young.

So far I'm loving the tubeless tyres. OMG how good are they? The bike is not trying to be a mountain bike but is reasonably capable on pretty harsh terrain. I rode the Contact Epic on it this year and whilst not well suited to the second half of the course it was OK. For its intended purpose however it excels, the bike disappears beneath me and rides as well on gravel as on seal. It has opened up lots of local unsealed roads including some spectacular climbing within a short ride of my house. Just this last weekend, I rode a 50km fully offroad loop with 900m of climbing right from my front door. I'm such a lucky boy.

The little green tag on the Brooks gives me access to hundreds of kilometers of empty forestry
roads at the weekends. I highly recommend you join if you live in or near North Canterbury.

I'm afraid that the jury is out on the Cinq5 shifters, I really, really want to like them, but they've let me down on a couple of big rides since I've had them. I'll write a full report on them later.

[Edit - The Cinq5 Shift:R system has now been replaced by a Gebla Rohbox, Take a look at my long term comparison of both systems]

In other news, I've knackered my back again. I bent down to pick up an allen key from the workshop floor and popped one of my existing prolapsed disks again. I spent yesterday in hospital on morphine which was where I wrote this so apologies if it's a little garbled. I hope that normal service will be resumed shortly. My goodness me, morphine is a powerful drug...

Monday, 17 August 2015

New Bike #1

I've been trying to clear a few projects lately. You know how it is when you have just too many things you have to do to make progress on the stuff you want to do. I also dislike having bikes in pieces. I'm increasingly finding that I'm forgetting details and mislaying or worse losing components. For these reasons, I've either been giving away or selling off some of the herd over the last year or so. I'm still not done but I'm making progress. The remainder is getting reassembled into complete bikes that I want to keep. The first example is this "BSA" from the late 1920s.

A BSA bicycle, yesterday.

The BSA is in quotes because although the frame is entirely made from BSA components, I have no idea who actually made it. The date is also a best estimate based upon components and a trawl of BSA catalogs. This approach is difficult here in NZ where local manufacturers had boxes of stock that was used until it ran out. In many cases long after the parts were manufactured. NZ was slow to accept new trends in bicycle fashion during the first few decades of the last century and lagged the rest of the developed world by a some way. When the first NZ & Australian riders took part in the Tour de France in 1928, the Europeans found it amusing that they were going to compete on technology that was 20 years out of date. The Australasian team upgraded as soon as possible to try and level the playing field. Even so the Kiwi in the team, Harry Watson, wrote home to complain about the reliability of the European bikes not being as good as locally made NZ ones. The bikes they took over to France would have been similar to this one.

I'm not sure why there was this lag. I've mentioned the likelihood of using up hoarded stocks of lugs etc. There is also the fact that NZ was very isolated from the rest of the world which would have meant an ignorance about emerging technology. But I suspect a large reason was shear bloody mindedness. "That bike was good enough for your granddad son, so it's good enough for you. Harden up". This continued right into the middle part of the century. The concept of a racing bike here was very different from in Europe. Steel rims were the norm although wood and rarely aluminium were used. Wide, heavy tyres were used as racing routinely took place on gravel, most roads being unpaved. Single fixed gear was normal and braking rudimentary or non existent. None of this detracts from the achievements of the riders though. These were genuine hard men, the equal to any in the world on two wheels. And of course since everybody was on the same equipment it didn't matter anyway. Genuine old racing bikes are not that common here. It seems that many were converted to roadster duties after retiring from racing. It's fun to spot these lurking beneath the modifications of time. Many were worn out and discarded, but even so very few seem to survive.

This one is something of a bitsa. Most components are BSA and are from the same period although the whole thing has been built up from spare parts. The frame is made entirely from BSA fittings. It has BSA lugs, brake and chainstay bridges, fork crown, steerer and dropouts, bottom bracket, rear forkends for the BSA cam system and a steering lock. I have no idea what the tubing is but is of the older 'D' profile chainstay, seatstay and fork profile. The steerer and crown are nickel plated and have numbers stamped which may or may not indicate 1928. The frame and forks are lightweight.

The wheels are 28 x 1 3/8" (ETRTO 642, 700A), a size that was obsolete in England by 1910-1915 but was still popular in the colonies right up to the sixties. Tyres are not interchangeable with the common 28 x 1 1/2" (ETRTO 635, 700B). New tyres are still available in a few specialist shops although I have a small stash of original Dunlops. These are the same tyres that were raced on back in the day, heavy block tread and all. The rims are wooden and I think French. The rear rim is the one that badly split a couple of years ago. I repaired the rim with modern adhesives and rebuilt the wheel, however the rim was unable to hold riding pressure in the tyre and it split again when sitting out in the sun.

The pressure was only about 40 psi at the time this happened. 

The new split was in a different place from the first one. I think that this rim will need to be for show only. The hubs are both BSA, the rear with the cams to adjust the tension. The rear hub also has my new cones made from through hardened 4130. I was going to run these as a trial to see how well they handle the real world before I start remaking all the worn parts on the facile. I'm going to have to learn how to make wooden rims in the near future if I want this bike to be ride-able on the road. More on that later.

The handlebars are early nickel plated racing bars. They are too narrow for me but I can't nip down the shop and exchange them so they will have to do. The saddle is a modern Brooks Pro that I bought new in 1995. I will change this when I find a suitable replacement. I'll put the original  gallows style seatpost back on at the same time. It doesn't work with this saddle, pitching it too far forward.

There are no brakes other than the fixed gear and no provision for them either. The frame is scruffy but has original paint and pinstripes so I've simply cleaned it up and oiled it. The chainset is an early nickel plated Durax, I've never seen a nickel one before and I didn't think the company was that old. Does anybody know when they started making these hollow octagonal fluted cranks? The bottom bracket cups and axle are Bayliss Wiley, the axle being a very elegant hollow example.

Tightly bound while the glue dries.

In other news, we've been tuning the trebuchet. The original design brief for these devices was to hurl the heaviest possible projectile a set distance. That distance being how far you had positioned yourself away from the target and out of range of troublesome archers etc. Our goal is subtly different, we want to throw a projectile as far as possible. Over the last few months the trebuchet has undergone a transformation. I've been studying the theory regarding the efficiency of these things (it's quite low by the way) and there are several things to pay attention to.

The weight needs to drop as vertically as possible to put as much energy as possible into the projectile. There are several ways to achieve this. The counterweight can be hung on a connecting rod as in our original design or the trebuchet can roll on wheels to allow the weight to rock the machine back and forth as it falls. It turns out that the length of the connecting rod is important, a longer rod allowing more correcting movement. In order to achieve this Kung Fu Pete came round and we moved the weight to hang horizontally.

Thomas, helping out.

At the same time I machined some better bushes for either end of the con rod. The whole machine was still being bodily moved with each throw, so it got some wheels added.

The wheels run on short tracks and the weight now drops more or less straight down.

As the weight reaches the bottom of the fall it has no option but to turn and swing horizontally. To get maximum energy into the projectile, you need to tune the release point to coincide with this direction change which will usually be when the throwing arm is vertical. There are two ways to do this, modify the angle of the sling hook and alter the length of the sling. These two variables affect each other so they need to be tuned together. A longer sling will release later as will a bigger angle to the release hook. It's a bit of a juggling act. Using a video camera and replaying in slow motion is an extremely useful tool to tune these variables. I imagine it's also what the medieval builders did.

The design of the throwing arm is worth some careful consideration. Ideally, it should be neutrally balanced so that the centre of gravity is coincident with the pivot point. This is hard to do and means that the weight side has to be bulky and the throwing side light and slender. I've consistently used a 1:4 ratio between the lengths of these with the current arm being 0.75m and 3m resp. The overall weight of the arm should be as light as possible to reduce the moment of inertia, again care needs to be taken that it doesn't get too weak. Since the tip of the arm on the throwing side is travelling extremely quickly, it makes sense to give it some useful aerodynamic qualities by making it wider in the vertical plane and narrower in the horizontal plane. I've also given it a rough aerofoil shape. I think I'm probably pushing my luck with the latest arm but it seems to happily throw 1 kg rocks without breaking or flexing too badly.

Swish it goes, very loudly.

The net result of all this work means that we've extended the range to just over 175 metres (~575 feet). There is a lot of variation between throws which is caused by having variable projectiles. Heavier stones describe a higher trajectory and  lighter stones a flatter one. I'm going to find a set of river boulders of equal size and weight and as round as possible. I can then fine tune the sling length and hook for maximum range using the video technique. Maximum range doesn't happen at a release angle of 45 degrees as you may think, it's more like 40 degrees. Air resistance having a large effect at the higher speeds means that releasing too high makes the projectile fall short. Mr. Middleton has badgered me into doing some accurate measurements in terms of range, height and duration. Watch this space.

We're pretty much at the end of the road in terms of more development of this design. That's probably not a bad thing though as there's now enough range to punch a hole through my nearest neighbour's roof if I get a foul shot. I really don't want that to happen. Loading and shooting this thing is also reasonably frightening, the forces and speed involved being potentially lethal. It has been an interesting exercise and it has certainly got people talking...

Tuesday, 19 May 2015

Myford Super 7

I still don't have a proper workshop but I do have a new lathe. New being a relative term of course. The Myford Super 7 that I mentioned months ago has now been completely refurbished. It's a sad and somewhat ironic fact that now that the original Myford company is no longer in business, spare parts are much easier to get hold of. Sadly, I think that this is a temporary situation as the inventory will run dry in due course. I've replaced everything that was worn. Bushes, bearings, feed screws, you name it. If it was worn I got a new one. The lathe has been dismantled into its component pieces, cleaned, painted and reassembled. The only component that didn't get taken apart was the clutch assembly as it was fine and I didn't need to touch it. The bed and slides are in very good condition. The front vertical shear being the only part that required attention. I made a jig to run up and down the bed and scrape the front shear. It was located on the two rear shears and adjusted with its own jib strip. This was very successful and has removed most of the taper. I didn't want to take too much material off but the result is very satisfactory. I had trouble with the original 0.75hp motor but I found another one and got it professionally wired to the Dewhurst switch. I'm pretty confident that I could have done it myself but knowing when to not do stuff myself is a useful skill that I'm slowly developing. I've only made a few little bits and pieces on it so far but I'm looking forward to learning the new lathe on the next project. So far I'm loving the gearbox, the higher speeds, the extra rigidity, the long cross slide, the spindle lock, the really easy back gear engagement, the 360 degree top slide, the auto eject tail stock. I could go on but you get the idea.

A long bed Super 7, this morning.

When I sold the ML7 back to Mr. Middleton I included all the original spares it came with including the chucks as they all had matching numbers and my OCD meant that they must stay together. The chucks that came with this lathe weren't good enough for my standards so I bought replacements from a supplier in the UK. They are original Bernerd chucks with almost no use. I'm keeping the old 3 jaw as a roughing chuck but I've sold the old 4 jaw. None of the numbers matched anyway. I also bought a larger 9" face plate and I treated myself to a genuine Dicksons QC tool post. I've been using one of the modern copies that are sold on any number of engineering websites. I was never happy with it, the standard of accuracy just wasn't there. Of the 16 QC tool holders I had only 3 would lock down tightly, I was unable to use the remainder. The Genuine Dicksons model is a pleasure to use and all of the tool holders can now be used for the first time. The difference in quality between the two is like night and day.

I also discovered that the Myford cabinet that the lathe came on isn't. A genuine Myford, I mean. It's far too flimsy, almost useless and it would be impossible to level. So I've cut the top off and bolted it down to my work bench instead. I like having my lathe up quite high so I don't have to bend over too much and the raising blocks have made this easy to achieve.

I've been riding a lot but not a huge amount on the facile. I do take it out occasionally but it has been having some issues. I snapped the first spoke a few months ago and I had a really hard time getting the broken thread stub out of the flange. I was concerned at the time I made the spokes that stainless steel was not a good material for this particular spoke application. The spoke had fatigued and snapped flush with the flange. I tried to cut a slot in to the stub with my Dremel and use a screw driver to extract it but it was just too tight. In the end I drilled a 1.5mm hole down the centre of the 2.4mm spoke and then filed the remaining threads away. It too me two days and I needed to completely strip the drive down and remove the front wheel to do it.

I suspect that all remaining spokes are similarly fatigued so I'm reluctant to break another. 

During the strip down I noticed wear on the bearing surfaces, particularly those in the lever pivots and the live axle. In all cases the wear appears to have started as the result of an impact that has dented the bearing surface, this has then got progressively worse. This means that the nitrided 4140 is simply not the right approach. I'm going to have to replace quite a lot of components but I'll have to do some research first. I've made a few sets of BSA cones as my first trial of new techniques to harden bearing surfaces. They are machined from 4140 but have been through hardened instead of nitrided. I'll see how they perform before I invest too much time re manufacturing lots of parts.

A pair of BSA cones in hiding. Notice the cams for chain tension adjustment.

The hub will need replacing as it has 6 bearing surfaces. Given the spoke issue, I'm going to take the opportunity to rebuild both wheels as tangentially spoked. When I first stared this project I wasn't aware that Ellis & Co. made tangentially spoked models. I've since found an excellent description from 1888 and located two surviving faciles with tangential wheels, one is geared and the other ungeared. The spokes are in a most unusual arrangement with the front hub having just 6 or 7 holes in each flange depending on the wheel size and spoke count. Each hole housing 4 spokes. I'll provide full details in due course. I was hoping to be doing my big ride about now but I'll put it off until the bike is repaired. I'm reasonably fit at the moment which is a great irony.

So the first real project on the new lathe is going to be making a rim roller. The rims currently on the bike aren't the right profile and for various other reasons I want them off my bike. I've been collecting parts for the rim roller for a little while and I hope to be able to start it soon. Both my giant son and Kung Fu Pete have expressed a desire to own a racing penny farthing so I'm going to need to be able to make some really nice, light rims in various sections. Both of them being unnecessarily tall means that I can make some huge bikes, probably 60" or so. Kung Fu Pete has also taken on the project of getting rubber tyring in various sizes made locally. I am extremely grateful for this as I simply don't have time. He's had a sample made that shows promise. We're learning all about exciting things like the shore hardness of rubber and what extruding dies look like. This will all be the topic of future blog entries.

In other news, we've had both sets of parents here over the summer. My lovely wife's parents weren't too happy when I had a 9" face plate, a Dicksons QC tool post and a pair of chucks delivered to their address in the UK to bring over for me. What's 15 kg between family members for goodness sake? My parents only left a short time ago. I needed to go out to the garage to count the Super 7 when they left as my Dad has always wanted one. Being a long bed model, he wasn't able to fit it into his hand luggage though.

In more other news, I finally got around to making a decent size trebuchet as a garden feature for the kids to play with.

Garden furniture.

We're fortunate in that we live on a hill and have a good half a kilometer of our land between us and the public road. It's a work in progress and it still needs more tuning. Adjustments to the sling length, pouch shape, counterweight, connecting rod length and the angle of the release hook all effect the trajectory of the missile. We're probably at the upper limit of what the frame will support with a 100 kg counterweight but by tuning we should be able to hurl a 1 kg rock out to 200m (~650 feet). We can reliably throw to 150 m at the moment. As my lovely wife commented though, with the tuning and the addition of weight, it's gone from a fun toy to a genuinely lethal weapon. I threw three rocks down the field this morning before work just because I can. There's something about it that I find immensely satisfying.

My giant son made a video of it in action you can see it here.