Monday 31 July 2023

Velocette KTTs 55 and 305: Wheels – Part 4 – Completing the Hubs


Work on the hubs was progressing well although I am starting to realize that restoring 3 bikes at the same time is quite a challenge! Looking at the dates on my photographs I see that I started working on these in the middle of April. It’s now the end of July and over 3 months of solid work has so far gone into sorting out 3 sets of hubs.

At the end of my last blog posting the status was:

      -       Front hubs were nearly finished – brake plates and brake shoes machined, 2 sets of cup-and-cone bearings and external bearing dust covers made, one front brake actuating lever casting and 2x brake cams machined.

 -      One rear “cotton reel” hub had been machined and new sprocket/brake drum acquired from Grove Classics.

 The following were the main outstanding tasks:

     -       One spindle and bearing cones required for the 3rd front hub

 -      One rear wheel spindle to be made for new cotton-reel hub

 -      Lock nuts for rear spindles

 -      Bearing dust covers to be made

 -      Relining brake shoes, fitting and machining to size in the lathe


Front Spindle and Cones

One more front spindle (EN16T) and 2 bearing cones (heat treated O1 tool steel) were made for the 3rd hub


Rear Wheel Spindle

The rear hubs have 2x taper roller bearings (discussed in the last blog posting) that have an internal diameter of 5/8”. The way in which these bearings are set up and adjusted is that on the brake drum side the bearing inner abuts against a shoulder on the spindle whilst on the opposite side there is a threaded portion and a pair of locknuts are used to set the bearing in the correct position. However, because the adjustment is on the right side of the bike the direction of wheel rotation dictates that the thread is left-hand to avoid the possibility of the bearing “winding into” the wheel should the lock nuts come loose – a safety measure.

The thread used by Velocette for adjusting the taper roller bearing is 5/8” x 24 TPI left-hand. This is a fairly obscure size and taps and dies for this particular thread are not something that would be usually be found “on the shelf” in the workshops of most vintage bike restorers. However, it turns out that this conforms to a UNEF thread specification (Unified Extra Fine) and HSS taps/dies are available ….from the Far East on Ebay at a reasonable price. These were ordered and turned out to be of very good quality - the threads they cut were both sharp and accurate.

The rear wheel spindle is more complicated than the front spindle in the respect that there are 2 changes of section on both sides and the thread for adjusting the 5/8” ID taper roller bearing is LH, as mentioned above.

The spindle itself, together with a new external dust cover made from solid (EN1A) rather than pressed steel, is made from 7/8” diameter EN16T.

The large diameter in the centre portion of the original spindle is ¾” diameter but I used 7/8” as I had this in stock and the larger size provides a more substantial shoulder for the inner of the taper roller bearing against which it abuts. The smaller diameter at both ends is 7/16” and is threaded BSCY 26 TPI. It should be noted that the dimensions of this spindle differ from the standard rear spindle because this was engineered to fit the rear hub that I had previousy made.

Chain alignment was checked repeatedly when building all rear hubs.

Dust Covers

There are both internal (inside the brake drum) and external dust covers to prevent water and road dirt entering the bearings on both front and rear wheels. External dust covers were made from solid, as illustrated above, whilst the internal covers were made by modifying some silicone rubber items found one Ebay. These were advertised as

Black Silicone Rubber Hose End Blanking Cover Caps Cap Heat Resist 2.8~60.5mm

To make the seal itself, the first step was to make a simple mandrel to hold the cap in the lathe chuck and a tool with a sharpened edge to hold in the tailstock chuck to cut out a clean hole in the centre of the cap.

A sharp knife was then used to cut the dust cap to length on the rotating mandrel to complete the operation (Health and Safety please look the other way). These were used for both front and rear wheels


and, although it might not be original, provided both a simple and effective solution.

Finally, 5 sets of brake shoes were sent off to Saftek for relining with bonded 6mm thick soft linings.

Where necessary, these were then mounted in their respective brake plate and on a mandrel to skim to size ...carefully, on the lathe.

The 6 hubs, spindles, bearings and brake parts are now completed.

After taking a few measurements for the rim offsets, these will go to Steve, my wheel builder at Wheelwise, to order rims and spokes in preparation for building the wheels.

When I was preparing this collection of hubs for the 3 Velo projects, I found that I was lacking 2 rear brake arms, part # KS 17/2

this is not an easy part to fabricate – it needs castings and so patterns were made for the foundry. As I would soon be visiting the foundry I made a quick audit of other small parts that I was missing. These included handlebar clamps, part # F 37/26

and so patterns were made for these too,

I’ll detail progress on these in my next post.

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