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.