The Abingdon Ball Head - part 2

Spring has sprung, the grass has riz.
I wonder where the birdies is?

etc.

In stark contrast to last week, Spring appears to have been switched on at last. The birdies in the above poem (incidentally not by Spike Milligan as I always thought) being magpies. We are nearly in the attack season again, I know this because I had one shout at me last weekend, next weekend he will be dive bombing me. But I digress.

This week I have made the top lock nut for the ball head, I have chosen to make the flush variant as I won't be using a lamp bracket mounted on the head. The original I am copying does have a lamp bracket as did the Percy Nix machine in the Coventry museum. This machine was used for the 24 hour race and would certainly have required a lamp for the night time part of the event.

This is a photo of the bike taken in or prior to 1931 (when it was in the Sammy Bartleet collection) 

and the lamp bracket is clearly visible. From Bartleet's Bicycle Book, 1931

The bracket has now disappeared as in this photograph I took just a few months ago of the same machine.

But this is what the flush variant looks like, neat eh? 

The Upper example is an early geared facile and the lower is a non geared model, both by Ellis & Co.

Machining the lock nut just involved simple turning and screw cutting 

plus a little indexing to get the holes in the correct place.

Now I can mount the completed neck into the head itself and establish

a) the length of the backbone to provide the correct inclination of the forks, this effects the trail of the machine and consequently how it handles.

b) the correct angle of the backbone to maintain an even gap between the wheel and the backbone. Although saying this, I have seen backbones on originals all over the place, some are very closely fitted with an even gap and some are not. Of the various originals I have now seen and measured, I have yet to see two the same, a remark echoed by other collectors that own these machines.

The angle of the forks likewise seems to vary hugely, the very early machines are more upright, something that is clear in the advertisements and literature. I've measured several from 1887 that have as little as 5 degrees inclination on the forks. This is in contrast with younger bikes that have up to 16 degrees inclination. The anomaly here is the racer from 1888 that has a full 20 degrees, this would produce a high trail value (for the period) that would be more stable at higher speeds with more rider fatigue. This is just my theory at present, I suspect it could probably be able to be ridden hands off.

As an aside I am currently reading the excellent new book on Dan Albone and Ivel cycles by Ray Miller and Lee Irvine (ISBN 978-0-9566337-4-3 available from the VCC UK). In chapter 5 Ray discusses how in 1886, Albone invented the first rear driving safety that could be ridden hands off, the discussion mentions the steering geometry being responsible but no actual mention of the trail. A friend of mine owns an 1887 Ivel safety locally (it is photographed in the book). Next time I see it, I'll measure the trail and report back. Clearly, steering geometry was beginning to be understood a little more by this time and I see no reason why Ellis & Co. wouldn't have adopted the current thinking at the time to slacken the head angle to provide more trail. I have decided to use an inclination of 16 degrees (the same as the original I am copying) which will give a moderate amount of trail.

The next job is to file the stub on the neck casting to be a very accurate fit into the backbone. I have made a little jig from part of the off cut backbone, this jig is coated with engineers blue, an evil substance that will coat everything within a 100 metre radius if children and cats are allowed into the workshop at the same time as the tube is open. The idea is that the backbone is placed into the jig and the high spots are marked by the blue, these high spots are then filed off and the process repeated. Great care being taken not to twist the casting relative to the jig. This took many hours, but the care has paid off and I now have a very well fitting backbone that should braze easily.

The jig to mark the high spots on the casting, 

shortly before engineers blue covered everything.

File off the marked high spots and repeat. Carefully.

Eventually, an accurate fit is obtained.

The backbone can now be cut to length.

A little trigonometry to ensure the forks are inclined at the correct angle before any cutting takes place. 

Ensure that both wheels are on a horizontal surface and the above chart is taped vertically 

to the wall behind the bike, then simply line up the forks with the chosen angle by line of sight.

Measure twice, cut once.

The tube has been left slightly proud of the edge to assist in the brazing process.

It will be filed flush afterwards.

The final job is to hollow out the stubs for all the reasons previously stated.

At last we can now do a dry assembly to see how it all fits together.

Still to do on the backbone is to make the step which is a simple folded piece of steel brazed to the left fork leg. I also need to drill and tap the holes in the rear fork crown to allow a mudguard to be mounted.

In other news, I have promised my lovely wife that I will build her a new deck when spring arrives. I fear that my shed fettling will have to take a back seat for a period if this good weather continues. I did try to bribe my brother to come and build it but he pretended not to hear me.

The Abingdon Ball Head - Part1

We've had some weather these past few weeks. Sadly it's not been of the kind that makes cycling enjoyable. This means that my shedweeks have been slightly more inflated than usual and consequently I've been busy. There are lots of photos for those that are hard of reading.

Do you recall the patterns that I took to the foundry some time ago? I received the castings back quite a long time ago, I just didn't get around to doing anything about them. Or telling you.

Freshly cast and very hard.

I've had them cast in p20 which has a similar composition to 4140 chromoly. p20 is classified as a tool steel (it's used for mouldings) and since the castings are small they have cooled quickly and become chilled. the castings were hard, too hard to machine so I took them to the heat treatment place around the corner and had them annealed. They were Rc52, they are now Rc31, still too hard for high speed steel tooling but OK with cobalt or carbide. I know this through experience after burning several HSS drills.

The first job is to make the Abingdon ball head so I can get the neck properly located in the head. This will then enable me to file the backbone stub to the correct angle so that the backbone will sit at the correct angle to the wheel.

I've been doing a little more research on the Abingdon ball head and it turns out that it was patented by Isaac Watts Boothroyd (of Ellis & Co. and later Crypto) and Philip Louis Renouf. I need to to do some more research on Renouf, his name pops up repeatedly in the 1880's. So it seems that Ellis & Co. the makers of the facile, invented the ball head and the Abingdon Cycle company then made it under license and also supplied it to other manufacturers. I have recently got hold of a copy of the American version of the patent (as stamped on the head) and when I figure out how to do it it, I'll make it available for download.

The American patent for the ball head, the text references 

the English one by number, 3294, as stamped into the head.

The original facile had all the correct pieces including the lamp bracket which mounts on the head by a lock nut on a lock nut (this will become clear). There were two options for the first lock nut, you could either have one flush as in the patent drawing or have one proud so that the lamp bracket could be mounted around it.

The original components.

As usual here is a series of photos describing the steps taken to machine all the bits.

mark the centres on either end and drill through, 

even using cobalt drills this wasn't easy, I ended up using carbide drills.

Then create the 60 degree inside cone on either end. I bought a special cobalt cutter for this, it was very expensive and I haven't told my lovely wife yet.

Next make the bearing cups that fit into either end. These each contain 10 x 5/32" balls and I needed to do some calculations on these to ensure the wall didn't become too thin.

Rough out the inner bearing surface.

Then machine and polish.

Finally, create the 60 degree cone. Part of by drilling through.

Then make the axle and the top cone, washer and lock nut.

Turn the axle between centres since it was frequently removed to check clearances.

Rough cut the thread and clean up with a die.

Mill the flats for the lock washer.

Turn and thread the cone.

Then knurl the outer edge and part off.

I hate knurling, it's a brutal, unsophisticated process.

Machining the grooves in the lock nut with a slitting saw.

Actually two slitting saws mounted side by side.

The component pieces.

The complete assembly then fits together in the same way as a pedal axle.

It takes standard ammunition...

Next week I'll make the top lock nut and file the stub to fit the backbone.

In other news, my lovely wife celebrated a significant birthday (-1) this week. In the usual manner I had asked for a concise list of potential presents well in advance. She wanted one of these, specifically the simple, non digital version that the Queen has. This is just as well since New Zealand is a simple, non digital country that the Queen has. It is possible to buy them in Australia but not here. I contacted the parent company, who have an office in Auckland, and asked if it was possible to buy the analogue version anywhere in NZ, they promptly replied that no you can't buy the analogue version in NZ because we don't have digital radio yet. I didn't reply.

I have ordered one from England and it will be arriving real soon now.

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.

Brazing the Front Forks

As promised last time, I've been directing my efforts at getting the front forks brazed up. There seemed to be an endless list of things to do before I could light up the oxy-acetylene though. I needed to hollow out the stubs that extend into each of the tubes. As mentioned before this is for several reason, firstly it helps to prevent cracks forming at the junction of the stub and the tube. Secondly it makes the brazing process easier as a large mass of material that is hard to heat is removed, this helps to prevent overcooking the tubes. And last is the obvious weigh loss from removing metal. In this case, hollowing out the 6 stubs (2 per 'knee' and 2 on the head) removed a pound of weight (0.45kg). Not insignificant.

However before I hollow out the stubs, I need to stamp the top of the Abingdon Ball Head with the appropriate patent information. I need the stubs to be solid to support the hammer blows required to do this. I admit to putting this task off for ages, the potential to completely screw it up is high. Every now and again I'd have a little practise on some scrap until I had developed a method of working that reduced the chance of errors. I was still shaking when I struck every letter and number though. The hard bit is to get the individual letters to be correctly aligned vertically with respect to each other and correctly spaced. My method is simple, I use 4 layers of masking tape to define the lower edge of each letter or number, placing each stamp onto the surface of the workpiece and then sliding until it contacts the ridge of masking tape. With practise, it becomes easier to apply the same pressure against the tape and the letters then line up with each other. To get the spacing correct, I mark the tape ridge at the correct intervals and then line up each stamp with the next mark.

It is worth noting that letters or numbers with less area, such as I and 1, require a lighter blow

 other wise they appear over struck compared to larger letters.

The results aren't too bad although the I is too far to the right,

I'm not too bothered as the original is also clearly hand stamped.

With this onerous chore out of the way I can now hollow out the stubs. I very roughly drilled and milled out as much material as possible before getting stuck in with a carbide burr mounted in an air die grinder. I bought a cheap Chinese die grinder that will run at 25,000 rpm without over running my compressor too much. Think of a dentist's drill on steroids. You really do need those high rpms when removing steel. It is a truly horrible job and results in thousands and thousands of razor sharp needles of steel *everywhere*, regardless of how carefully everything else is covered up. I've been digging steel splinters out of my fingers (and feet!) ever since despite wearing a ridiculous amount of PPE.

Roughly removing as much material as possible...

...before getting the carbide burr out

A pound of steel was removed from these 6 stubs.

Now I need to make a jig to hold everything in the correct location whilst the heat is applied.

I happened to have some angle iron in my magic cupboard, so this got chopped up... 

...and with some 10mm threaded rod, I can locate all the bits in a frame that doesn't move.

I used 40% silver solder to keep the heat on the 4130 chromoly tubing down. Silver solder has suddenly got really expensive, still I only need the one kidney. It all appears to have been successful with good penetration into the joints and very little distortion from the heat, although one of the blanks in the bearing house was *very* hard to get out afterwards. Fortunately I had previously made a 1.75" x 26tpi tap and had it hardened for exactly this eventuality and I was able to clean out the threads nicely.

This week I'll clean up the joints and mill the slots for the locking tabs. Then I can continue with the gunmetal flanges. Then I can make the spokes... etc. I've set myself a goal of having the frame sat on it's wheels inside of a year. I'm already 6 months into the project and more or less on track.

In other news, I've finally managed to arrange a small aftershock for my parents, We were having dinner in Christchurch and were rudely interrupted by a vicious little 4.6, I don't think they liked it much. We also had a nasty little swarm last night but fortunately my parents are away on a tiki tour of the West Coast this week. I'll try and save a few for their return.

In more other news, someone seems to have stolen summer this year. We haven't had one yet, does anyone know where it is?

Trepanning my head - part 2

This week, I've been boring a hole in my head. Not my actual head of course, that would be silly and may effect the completion of the geared facile. Also, I've been away with the whanau for a while, you may or may not have noticed.

Now where did we get to?

A light shave

With the head still mounted in the four jaw and the fixed steady, 0.050" has been shaved from the inside and outside of the area that will become the lugs for the fork legs, this has defined the limits where the fork tubing will slide onto. Also a 0.5" hole has been drilled 2.5" into the head from the under side. Now the head can be removed, flipped around and remounted. Time to bore a deep hole.

I confess to being a little nervous about boring this hole and have asked advice from my Father, who is an engineer, and from Mr. Middleton, who is not. The hole is 4.5" deep and is shaped like a wine bottle with a narrow neck (1.0") and then slightly wider (1.080") for the remainder of the depth. The hole is effectively blind with a flat bottom and a 0.7" diameter counter bore 0.1" deep. This will all have to be machined using the dials only as there will be no visibility down the bottom of the hole with a boring bar in the way. A bit like flying on instruments only, so to speak. The neck of the bore is threaded at 20tpi for 0.75" and this thread then gradually runs out into free space at the wider part of the bore, a nice engineering solution.

The bore is actually a through hole, but is only 0.5" diameter at the lower end. The first job is to drill the remaining 2.5" from the top down to meet the first hole (depth of bore is 4.5" with 0.5" remaining at the base). Starting with small drills and in steps increasing the size and reducing the speed until the 0.5" drill meets the first hole, I was pleased that the two met perfectly concentrically.

Start small

Concentric with the hole from below. Hoorah

Because of the depth, I need to use as larger diameter boring bar as possible to maintain rigidity. I'd also like to be able to use the same bar to machine the counter bore and face the bottom of the hole. A little trig. calculated this as a 16mm bar which requires a minimum 18mm hole to start. I bought one which uses the same CCMT06 inserts as the rest of my carbide tooling just for convenience. I used Carbide NZ who provided a great fast service. Unfortunately, my wife noticed the parcel and asked awkward questions. I'll need to build up my family credits again. First job is to enlarge the 0.5" hole to 18mm to the correct depth for clearance for the boring bar.

The largest drill I have - 18mm

This required careful depth calculation as the drill tips are 118 degrees and I need a flat bottom. By engaging the lead screw and feeding the saddle along with the graduated lead screw hand wheel, this is relatively easy.

The boring bar was a huge success and the hole has come out well. The counter bore at the end proved a little tricky but as far as I can tell by looking down it is OK. I'll be able to tell when I machine out the back of the head for the neck recess. A good tip I was given for boring is to have the tool tip a whisker above centre height, this means that any slight catches or dig ins will tend to push to tool tip away from the workpiece and not into it. This becomes important in a small home workshop where I don't have the ability to flood the tool with cutting fluid to remove the chips. A whisker, by the way, is a precise measurement, it is slightly bigger than a smidgen but not as large as a tad.

For some reason I forgot to take a picture of the boring process.
As consolation here  is a  photo of all the swarf from the machining of the head.
I have a Chinese company interested in mining rights

The next job is to cut an internal 20tpi thread on the narrow section of the head.

In an Abingdon ball bearing head this thread is not used to adjust the head bearing
as in a conventional cone bearing head but is used to lock the neck in place. More later.

I'd previously made a male threaded part to screw into this new thread, this serves two purposes. First it acts as a thread checker when cutting the thread and also as a new centre for centre turning again later.

Here's one I made earlier

The last of the turning operations on the head is to taper the main section. This is reduced from 1.6" to 1.3" over 4.5" inches which works out as a 1.9 degree taper. The Myford top slide only has about 3" of travel so I had to take two bites at this and feed the saddle along. In practice this was fine.

Note the false centre in use

Next week I'll start carving the handlebar mount.

In other news, as previously mentioned, we've been away. First to Mount Cook Village with the family courtesy of my employers. I like Mount Cook and thoroughly enjoyed the trip, we had heavy snow falling on arrival and then bright sunshine for the remainder of the weekend. Perfect conditions for some beautiful walking.

Our hotel - The Hermitage - is in the centre of the photo

Then last week we all travelled to the Coromandel Peninsular where we did all the usual touristy things

On Monday morning I got up early and went for a fantastic bike ride in beautiful weather on deserted roads. Was there some big event on the Sunday night?