Sunday 14 January 2024

Work on the Cycle Parts, Oil Pump Castings Delivered and a New Cylinder Head

Well, it’s a new year, 2024, and I’m hoping that I will be able to make good progress on the 3 early cammy Velo projects this year. Unsurprisingly, I am finding that it is taking considerably more time to restore 3 bikes simultaneously than one but it also has the advantage that restoring the bikes in a parallel rather than a serial fashion is more efficient in the respect that the process of reverse engineering and subsequent repair of original parts or manufacture of new components avoids repetition of certain steps.

I am waiting for the wheels to come back from my wheel builder but I’m pleased to say that the cambox scavenge oil pump castings (K-102/2) have just come back from the foundry after heat treatment. I’ll shortly start on reverse engineering the existing pump body and then machining new ones.

In the past month there have been plenty of relatively small but necessary jobs that needed to be done to complete preparation of the frame and forks before starting the dry builds.


Brake Pedals (part numbers F-39/2 and F-39/25)

Although I have 3 brake pedals, shown below,

a bit of work was needed to bring them to a good standard. The 2 on the left are original Velocette items and the one on the far right is a well-made unmachined casting that I acquired some years ago.

The brake pedal in the middle (part number F-39/2) came with the KTT 55 project and, as can be seen by comparing it to either of the others (part number F-39/25), has a shorter section at the pivot. The difference is because F-39/2 is for use with the TT footrests (as referred to in the parts book - more about those shortly). Somebody has kindly cut off nearly half of the pedal, presumably to avoid interference with something (primary chaincase?) and the first little job was to repair that.

The outline of the pedal was drawn on a piece of cardboard to enable the shape to be transferred to an appropriately thick piece of mild steel.

The shape was then formed roughly on the milling machine (it’s too cold to go outside and use the emery flapper wheel on the angle grinder)

before TIG welding on both sides

Finally, the repair was filed to size and a countersink milling cutter used to reproduce the pattern on the original.

It was probably the same person that cut off the small lug at the rear of the pedal that forms the stop and so another one of these was made and TIG welded into place.

The raw casting was machined and there are now 3 functioning brake pedals plus pivots.


Repair to Rear Brake Anchor Lug

Somebody had chopped off the brake anchor part of the rear frame lug on the KTP frame. I have no idea why anyone would do this…

A piece of steel was shaped appropriately to fit

and then TIG welded in place and finished to shape

Footrest Support Stays (FK-167 and FK-167/2)

The early KTTs have support stays on both the left and right sides of the bike. In addition to supporting the footrest the left stay also supports the brake pedal pivot and both add structural strength by “tying together” the rear part of the frame and the engine plates.

The right side (part number FK-167) looks like this on the bike (a photo I took of a KTT at Founders Day)

and the left side (part number FK-167/2) is shown below.

I had one good original pair of these from KTT 55 but the ones fitted to KTT 305 were neither original nor particularly well made in aluminium and needed replacing.

Flat steel bar (1 ¼” x ¼”) was bent to the correct shape for both components with oxy-acetylene and these were then clamped to the originals to spark erode the square sections – I have a good spark eroder 15 minutes away and it’s just easier and more accurate than filing.

The orientation of the square holes is very important to ensure that 7/16” square bar can be inserted through both sides and, for the front squares, also through the square holes in the engine plates.

The above picture shows the start of the dry build for KTT 305 with the new support stays in place. The frame has been grit blasted, carefully checked for any damage (all is OK) and primed to prevent it rusting. A spare pair of crankcase castings (they have a KA prefix engine number so probably from a KTP) are used to support the build.


Shock Absorber Adjuster (Part number 36F)

The Webb bottom girder fork links (23F and 24F)

have a threaded adjuster (part number 36F)

that is used to adjust the spring pressure that determines the amount of frictional damping.

Two sets of my fork links (one original pair and one pair that I had cast and then machined – see here) have a ¾” x 26 TPI thread and replacement adjusters also have the same thread. The one in the picture above is a new and well-made replacement from Ray Daniells.

For some unknown reason, the 3rd pair of bottom links, which are original Webb components, have a ¾” x 16 TPI thread and it was necessary to rethread a pair of adjusters to fit accordingly.

The first step was to set up the adjuster in the 4-jaw chuck to bore the centre to accept an insert.

The aluminium bar is to assist in setting up the adjuster on centre.

The central threaded portion was bored to accept a steel insert – the picture below shows an unmachined original (upper) with a machined one (lower)

Steel inserts were made and silver soldered into both the bored adjusters

and the 16 TPI thread screw-cut on the lathe (I do not have a ¾” x 16TPI tap)

The difference between an original 26 TPI (lower adjuster) and the new coarse 16 TPI thread (upper) is evident in the picture below.


A New Cylinder Head

I had decided some time ago to use an iron head on KTT 55 rather than the Mk IV KTT bronze head that came with the project ...but rather than dismember another engine I needed to find another head.

Luckily, a MK 1 KSS head turned up on eBay – see picture from the eBay listing below, which I won for a very reasonable price.

It is in remarkably good condition – all threads are good and there is only one very small part of a fin missing and that is hardly noticeable.

After grit blasting, an application of high-temperature cylinder black and with new valve guides, valves, springs etc..

the head is now with Automotive Machine Services to have valve seat inserts made and fitted.

And finally ….while I was repairing the brake pedal I noticed that the file I was using was Made in Sheffield and with a trademark.

The file is made of cast steel, it is very good quality and in excellent condition despite being over 70 years old and possibly made before WW2 – I inherited it (and many other hand tools) from my late father.

I don't recognize the trademark and, being curious, I emailed the Hawley Tool Collection to see if they knew. They replied immediately and the file was almost certainly made by William Makin & Sons Ltd who ceased trading in 1979.


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