My Method of Widening a BSA Bantam or Triumph Cub Rear hub.

 

I thought has I was about to widen my New Cub/Bantam rear hub ,that other people may be interested in the method I use to achieve this so have taken a few photos to help you.

 

 

This is the hub  fitted into the lathe, and I have just parted the hub into two parts. roughly in the centre of the hub tube.

 

***All Photos "Otterman"

Hub Now in two halves.

 

 

Now before I started to part the hub I center popped the four dots in line ? Well the hub needs to be welded back in the same line to maintain the spoke pattern!

 

 

With the new center section machined , I actually machined this from solid stock, but you could use machining thick walled tube. The hole through the middle is about 30 mm.

You can see that I have made the hub wider by 38mm,and the sleeves that fit into the hub are 25mm.long each side.

 

 

This is the three sections now pressed together? just a firm fit.

The hub is now fitted back onto the lathe ready for tack welding.

 

 

The hub was firstly trued by hand with the lathe out of gear, and then has you can see, spot welded in several places on each seam. The hub was then mig welded around while being turned by my left hand.

Also Note that a tight fitting Mandrill is needed to be made up with a centre hole to take the live centre on the tail-stock of the lathe.

 

 

The  hub was then left to cool ,then the lathe readjusted, and then the welds machined down to leave a plush finish.

 

 

OK there you go then. The hub will be off for powder coat on Monday morning.

 

John Hooker mailed me last night,to say drill the sprocket mounting bolt holes out to 6mm and use countersunk set screws and lock-nuts?

Well I have hubs built like this and I also have hubs using Acme Stainless bolts that are made to original spec? 7/32x 5/8 BSCY thread.

One problem is in trying to buy a tap this size!!! Near impossible so don't let the holes get filled with powder-coat. OK.

 This hub I have is new, maybe for a army Cub, It came from Nick Draper, so I feel I have to use it in memory of his dad John, who was a bit of a ACE on the trials Bantam, and had loads of interest in the last factory bike so I am told. Even got "Jeff Smith" to ride one once.

2/2/14

The hub is now back from being powder coated, and I have cleaned of the aluminium masking tape.

After a long search I maneged to find a 7/32"x 26 TPI set of taps from RDG Tools that I had delt with before .so the threads have been taped out ready for the sprocket.

New bearing will be fitted when I have finished machining the new longer spindle. this again needed new 5/8" taps and die bought from RDG 20tpi for this BSCY

 

08/10/2016.

I have been asked this week which is the best size for the BSA Bantam or Triumph Cub to be widened by.

Well A standard BSA Bantam hub is about 2 3/4" between flanges, centre to centre.

And Sammy Miller used to widen his hubs for the Faber Framed "Otter" by 1 1/2" (38)mm.

So our New centre section is 38mm, but don't forget that the parting tool I used is 3mm wide so that leaves the result at adding 35mm, Now if this is a Cub Hub this will probably make the New flange centres just under the Four inch mark (4")but using a Bantam it will be just over. This hub that I widened measures about four and a quarter, (4 1/4").

For a BSA "Otter" Foster or Faber this is fine and most of my swinging arms measure seven to seven and a half-inches between the swinging arm blades.

A standard BSA C15 is 170mm just under 6 3/4", the Faber and Foster "Otters are seven inches (7") and the Bantam that this hub is intended for is just under seven-and a half (7 1/2").

So it is down to what you intend to fit the hub into when you have widened it.

One most important thing is DON'T go buying a set of spokes that are said to be for a BSA Bantam or Triumph Cub for a eighteen inch (18") rim Why? because they will be to short.

 

More of an update later.