Rebuilding a Model K Gearbox, an Alternative Hand Shift and my First Motorcycles

 

This is the last, the 4^th in fact, of the early 3-speed gearboxes that I have rebuilt.

This one is from an early Model K and has a very interesting hand shift attached directly to the gearbox rather than the usual petrol tank mounted lever.

As some of the bracketry and the gear change lever itself is remarkably similar to that found on the later positive stop mechanisms my initial reaction was that this is an early (discarded prototype?) positive stop. However, looking at it a bit closer it is not a positive stop – there is nothing in the mechanism to prevent a 1^st to 3^rd gear change; it is simply an external gate and fulfils the same function as the GC-3K Gear Control Gate that would have been a factory fitting. Why has it been fitted instead of the production item? I have no idea …like so much else, it is lost in the mists of time.

The one observation that I can make, however, is that quite a bit of effort has gone into making it. I don’t believe that it originated from the Velocette works at Hall Green but it could have been made in the workshop of one of the main Velo dealers, L. Stevens Ltd. in London, to whom the bike was shipped in 1926. In spite of the corrosion on the ferrous components, the gear change turned out to be quite serviceable – many of the nuts/bolts/screws were brass, which helped. Anyway, more about this later.

The gearbox was in remarkably good condition with no bits broken off, good threads throughout and with just the usual wear and tear of the internal components that would be expected after nearly 100 years.

On stripping the gearbox, I was surprised to find that it was fitted with a close ratio gear cluster.

There is a bit of rounding on the teeth of the mainshaft 2^nd gear but quite serviceable. The fit of the bush in the sleeve gear was not so good - it was free to rotate, but the wear of the bush on the surface with the mainshaft was quite acceptable and, after aligning the oil holes, a thin coating of Loctite 638 will ensure that the sleeve gear bush never moves again.

The clutch operating lever, C-31/2, that bears on the ¼” diameter thrust pin was not in quite the right place, as evidenced by the witness marks,

and this could only be corrected by removing a small amount of material from deep inside the gearbox shell using a Dremel at the location indicated with a bit of welding rod in the picture below.

The operating lever now bears centrally on the pin.

The layshaft end float was checked in the same way as the other gearboxes (see previous blogs) and a 0.011” shim was added behind the B-22/3 bearing to adjust to 0.008”.

On stripping the gearbox, I found that a 0.080” brass spacer had been placed between the sleeve gear and the bearing

and when I checked the meshing of the sleeve gear and layshaft gear I found that the alignment was perfect. Clearly, someone had taken the trouble to build this gearbox carefully in the past.

All bearings, including the sleeve gear bearing, were renewed - 4 in total. Finally, I found that the B3 cap that screws into the end cover did not quite reach the outer of the bearing that supports the end of the mainshaft resulting in the bearing being not properly clamped. A small annular disc was therefore made to ensure the bearing is locked in place.

Now, back to the external gear shift mechanism. The picture below shows the complete mechanism after removal from the gearbox.

After stripping, grit blasting the larger parts and putting smaller parts in the tumbler overnight, the various components cleaned up well.

It is impossible to get rid of the corrosion but all of the ferrous parts are serviceable and were subsequently chemically blacked before reassembly.

But first, a few observations about this mechanism: first and foremost, it is not a positive stop mechanism. The spring-loaded pawl and cam (the bit with the notches) replicate the functionality of the B64 “gear striking selector” (Velo parts book terminology) and the B66 selector plunger that are located inside the gearbox, shown below.

(note: the above picture is from one of the other gearboxes – the only difference is that this gearbox did not have the notch for neutral)

The second observation is that there are 2 sets of notches. One set has 4 notches – 3 deep and one shallow (and similar to the setup in the above picture) and at the other end are 2 notches for the pawl to engage.

As it was set up, the pawl engaged with the 2-notch end rather than the 4-notch end. Why would that be when there are 3 gears and a neutral? The semi-circular cam part could be fitted either way round and so the only way to find out was to try the 4-notch end.

The reason immediately became apparent: the notch for 2^nd gear had been put in the wrong place! By checking the distance (to ensure it is the same) between the B65 striking lever and the point of connection of the linkage on this mechanism in each gear I found that 1^st, 3^rd and neutral were correct whereas the notch for 2^nd gear should have been in the position indicated by the mark that I engraved on the cam shown below.

Whoever made it assumed that the notch positions for 1^st, 2^nd and 3^rd would be equidistant – they are not. Rather than make another cam, they simply swapped it around, made 2 notches for 1^st and 2^nd and 3^rd would be selected without a notch – this works fine – I’ve tried it.

If I can find a spare day or two, I’ll make another cam with 4 notches and try and get them all in the correct places.

In the meantime, the gearbox and the shift mechanism are all reassembled and working well. The gear indexer may not be pretty but it is an original period feature, probably made 95 years ago, and is part of the provenance of this bike.

I’ll make a new ¼” threaded adjuster rod and refit the kickstart in the next day or so.

 

And Finally….

Somebody asked me recently what was my first motorbike. Well, the first motorbike that I rode legally on the road at the age of 16, back in 1967, was an AJS Model 20 with a Swallow single-seat sports sidecar. The AJS Model 20 is a 500cc twin. In those days, the law allowed learners to ride solo motorcycles up to 250cc and unlimited (!!) capacity if a sidecar was fitted. I went for the 2^nd option. Life was much simpler then: a new rider applied for a provisional driving licence, bought insurance and off you went on the steed of your choice – without any training whatsoever.

By the way, please don’t think that this bike was in any way exotic. I bought it from a mate for 5 GBP and it subsequently needed a lot of work to make it roadworthy. I had also never ridden a bike + sidecar before and anyone that has previously ridden only solo motorcycles gets the shock of their life the first time they ride a combo! As you quickly find out, you have to steer them and point them where you want to go rather than leaning.

Anyway, in those days I lived in Shanklin in the Isle of Wight and on the day of my 16^th birthday I set off from the farm from where I had bought the bike to a motorcycle dealer in Carisbrooke by the name of Dave Death to get an MOT. They are still in business now – see their website here. If you scroll down their web page you will see a picture from 1962 – this is exactly how it looked when I went there.

The bike failed it’s MOT test on pretty well everything and so I set off for home – it’s about 10 miles - to start repairing things. About half way home, just coming into a village called Godshill, I was approaching a left hand corner and blipped the throttle to change down a gear and ….the throttle stuck wide open. There is nothing worse than an engine revving it’s nuts off under zero load – there was no kill button and the only thing to do was to keep it in gear and try and slow it down. Anyone that has ridden a sidecar outfit knows only too well the consequence of too much speed in a left-hand corner: either the sidecar wheel comes off the ground (as a prelude to turning over) or you straighten up, keep the sidecar wheel on the ground and go straight on. I choose the latter and went straight through a hedge on the opposite side of the road, ending up in the middle of a vegetable patch of somebody’s garden ….with the engine still revving. I managed to stop the engine by removing the spark plug caps and simultaneously electrocuting myself. But at least the engine was now quiet. After a bit of work, I nursed it home. An interesting first day on the road.

However, this wasn’t my first ever 2-wheeled + engine “thing”; that was a Velo Solex. For anyone that doesn’t know what these are they look like this.

Acknowledgement to whoever owns the copyright of this picture.

These were produced in prodigious quantities in France immediately after WW2 and consist of a 49cc engine that has a friction drive onto the front tyre. The engine pivots and so can be ridden as a cycle. It is started with the engine lowered, pulling in a decompressor lever with the left hand, pedalling like hell, letting the decompressor lever go ….and away you go. There was no throttle – either the engine is under power or it’s not.

So, how did I come by one of these? Well, back in secondary school days it was customary for boys (I have no idea what girls did – I had zero interest in girls at the age of 13) to get a job during the school summer holidays. I had a variety of jobs during my school years – gardening, clearing tables and washing up for a tearoom, making plastic bags in a factory, working in a garage but the first job that I had, for 3 summers in fact, was working at a shop by the name of Barney’s Emporium in Shanklin.

This is a picture of it in its heyday.

Acknowledgement to whoever owns the copyright of this picture

The shop was interesting, to say the least; it was owned and “managed” by Barney Powell and the part of the business that made any money was selling binoculars and telescopes. The other part of the business was a joke shop and the shop window was full of Barneys own jokes and comical take on life and which raised money for charity which was donated to the local Cottage Hospital each year as I recall.

Barney came from a family of actors/musicians/comedians and Barney himself was a comedian and musician that, among other things, played the xylophone on stage with his feet while sitting on a high stool! Quite a character.

Acknowledgement to whoever owns the copyright of this picture

But back to motorised bicycles…. Barney had a Velo Solex and for the 3 years that I worked for him he asked me to take it to a garage in a nearby town for an MOT test. I was supposed to pedal it there but, needless to say, once I had gone past the local police station in Shanklin I lowered the engine onto the tyre and experienced the pleasure of power for the first time. I remember when I got back (having passed the MOT) Barney feeling the cylinder with his hand and, with a glint in his eye, commenting on how hot the sun was today.

It turned out that this was his second Velo Solex. He had given an older one to a previous employee that had since started work as an engineering apprentice but had no interest in, and had done nothing with, the bike. I acquired it (for nothing) and then started to figure out how to get it to go. The engine on these bikes has a small petrol tank on the right side and a flywheel magneto/lighting coils on the left. After fiddling around, not really knowing what I was doing, I managed to get it going.

In the meantime, I had spotted another little bike with an engine in my neighbours open shed in their back garden. It had been there quite a few years, quietly rotting away, and I got this one too. It was a Cyclemaster – one of these.

Acknowledgement to Bonhams

I managed to get this going – so now I had 2! And what do you do when you have 2? You race them. There were always plenty of quiet lanes and footpaths where my buddy and I could ride these – we were still some years away from 16 years of age - we’d end up in some kind of social care these days. But it was pretty harmless and we learned a lot.

So which bike won? The Velo Solex. Although I didn’t know this at the time, the Cyclemaster was produced in 2 engine sizes: initially 25.7cc which was increased to 32.6cc in 1952. Although mine had the larger engine it could barely power a skinny lad along a straight – it was one of the noisiest and definitely the most gutless bike I’ve ever ridden.

Rebuilding KTT 55s Gearbox and Gearbox #1 - part 2

Having just completed the Rebuild of KTT 305s Gearbox, the laser welding repairs to the gearbox shell of KTT 55 and the end cover of gearbox #1 from an early 3 speed gearbox for one of the flat-tankers came back from EMP tooling.

The damage to the end cover of gearbox #1 was the more significant. You may recall from a previous blog post that the end of the bearing housing had been detached – see picture below which shows the damaged cover, on the right, compared to a good one - by somebody trying to remove the mainshaft through the bearing in the past.

I had cleaned up the surface of the end of the bearing housing, made an aluminium ring and then asked EMP to weld it to the casing. This was the result.

Now, I am not a time-served welder – I stick bits of metal together to the best of my ability using TIG or gas, but I imagine that anyone trained in the skills of welding would concur that this is a work of art.

To digress for one moment…. many years ago, when our 2 daughters were small children, one of the bedtime stories I used to read them was The Tailor of Gloucester by Beatrix Potter. It is a lovely story about how an old man, the tailor, is unable to finish making a waistcoat for the Mayor of Gloucester because he gets sick. Jumping to the punch line, mice, that live in the walls of the old house, sew the waistcoat for him and the stitching is so fine and exquisite that the tailor becomes famous. Nobody knows that the mice did the sewing – the last line of the book is: The stitches of those button-holes were so small—so small—they looked as if they had been made by little mice! If you want to watch it on Youtube you can see it here – the relevant bit is at the end.

So, what is the point of this little ditty? When I see the laser welding in the above picture, I think of those little mice sewing the button holes to produce a piece of work as exquisite as this.

Anyway, back to rebuilding gearbox #1. Measurements were taken for the layshaft end-float – the end cover-to-bearing distance

(the block of metal under the measuring face of the height gauge is a 1” slip gauge) and the shoulder surface for the bearing on the layshaft to the mating surface

and, including an allowance of 0.035” for the gasket, gives an end float of:

 (0.419” + 0.035”) – 0.46” = - 0.006”

 With a 0.019” (0.5mm) shim behind the bearing,

the end-float becomes 0.013”, which is quite acceptable.

After checking the mesh of the sleeve gear and layshaft gear, which were fine, the gearbox was assembled and checked that all gears select – all OK.

Out of the 3 gearboxes that I have so far refurbished, this is the only one that has a kickstart – neither KTT 55 nor KTT 305 have the facility for fitting a kickstart. One important point to check before putting the layshaft into the gearbox for final assembly is that the flat on the end of the kickstart shaft is in the correct (on the upper side) position for the kickstart cotter pin when the kickstart lever is fitted

by positioning the B-14/3 cam in the correct position.

The cam can be put in either of two positions 180⁰ apart and it is the location of the stop on the outer part of the cam coming up against the stop in the gearbox shell that determines the “rest” position of the kickstart. If it is the wrong way round then the flat on the shaft for the cotter will be at the bottom which will position the kickstart pointing vertically downwards instead of up. Not very convenient for starting the bike!

A new C30/2 clutch thrust pin was made from silver steel and heat treated and a new roller type thrust bearing fitted (see previous blog post for details).

A pack of 10x ½” UNF (20 TPI) nuts was ordered and 5 of these were turned into castellated nuts (part BK-50) for the sprocket end of the mainshaft

using the rotary indexer and a 2.5mm end mill – the picture below shows these together with my one-and-only good original and 4 unmachined nuts (these will be reduced in width and used on the other end of the mainshaft – one has already been used on KTT 305s gearbox).

Finally, I was missing an oil filler plug for this gearbox. These are available for later models, which have a different oil filler, from both Grove Classics and Velo Spares Ltd however the larger plugs for the early gearboxes are not listed for sale.

The only option was to make one from a 1” diameter piece of brass by copying one from one of the other gearboxes.

The thread on the original is 13/16” diameter and 13 TPI and I cannot find any standard British, American or metric thread that comes anywhere close to this (….just out of curiosity, please message me if you know differently). Not that it really matters as my lathe can screw-cut a 13 TPI thread without a problem although the thread is so deep that a standard threading tool would not have cut deep enough and I had to use a tipped tool,

DCMT 07 02 04, normally used for regular machining, to get the required depth of cut. It’s not perfect but as close as I could get without grinding a one-off HSS tool.

The rebuild of gearbox #1 is now complete.

The masking tape is to stop various loose bits, such as the thrust bearing, falling off and scattering rollers over the workshop floor. Having misplaced a roller from a big-end assembly in the past (see end of this blog post) I am now especially careful.

KTT 55s gearbox didn’t need too much work. The damage to the shell of KTT 55s gearbox, shown below,

was more untidy rather than structural where somebody in the past had knocked off the corner at the boss of the casting where the 5/16” BSW threaded adjuster enters.

This was repaired.

After checking the mesh of the sleeve gear and layshaft gears

it was found necessary to add 2x 0.019” + 0.011” shims behind the sleeve gear

to achieve alignment.

Rebuild of the first 3 gearboxes is now complete.

In summary, all parts have been checked and any structural damage has been fixed as best as possible, all of the bearings have been replaced (with the exception of 2x sleeve gear bearings that were OK), layshaft end-float and sleeve gear/layshaft gear mesh engagement has been checked and corrected where necessary, new thrust bearings have been fitted, new thrust pins have been made and fitted and a set of new CR gears was fitted and a new kickstart shaft made for KTT 305s gearbox.

There is still a bit of outstanding work to be done – I need a BK-12/2 kickstart for the 5/8” diameter shaft of gearbox #1 (I have 3 later ones with 3/4” diameter – which are of no use because, whilst I can sleeve the main hole for the kickstart shaft, the centre for the cotter pin is too far away from the centre hole and that is not so easy to change) and a couple of B-29 ball joints – these are actually quite complicated little parts – see picture below of all the constituent bits of a deeply corroded one

….but I’m sure something will turn up.

And finally… Apart from the usual spanners, screwdrivers etc I have found that 2 tools are particularly useful in disassembling and assembling these gearboxes.

The first is a bearing puller – this is my set

for removing the B-22/3 bearing in the layshaft. The second is a couple of pin wrenches

for the B-4/3 kickstart shaft end cover.

And finally, I have just started to work on the gearbox from an early Model K

which I think is going to prove to be interesting.