Development Work

Fork Blades 

Profile Forming Tool

Bob's Geared Facile blog (http://geared-facile.blogspot.co.uk/) describes an adaptation of a leather cutting machine he used to form the fork blade profile. Being unable to find such a machine I rummaged in the scrap box and borrowed some change gears from my Myford to come up with this alternative.

The machine has a couple of rollers machined to match the oval profile required for the fork blades.  The rollers are driven by the hand crank via the change gears and the spacing between them can be adjusted

Trial Fork Blade - formed from 1" x 18swg Mild Steel

Fortunately, when checking the outer perimeter of the remains of the original fork blades this was found to be 3.142 inches - i.e. equivalent to a 1" diameter tube.  First trila using some scap alloy tubing showed promise so some 1" x 18swg mild steel tubing was ordered and a short length used to check it would still work with the stiffer material.  Result was good, but suggested a better lever would be desirable (this is in hand see later)





Next stage is to sort out best way to form rake a nd taper on the blades...........

Wheel Rims

Mean while success with this and more info from Bob's blog turned my mind to making wheel rims.  At first I was tempted by the method Bob described of using tubing sections cut in half, nested together and welded. However, my welding skills have a long way to go to be good enough for that.  Sturmey's Indispensable Handbook describes The Club Hollow Felloe and says it is constructed of a steel tube rolled into a crescent section without join.  Now this appealed to me more and having already made a rolling machine it seems worth giving it a go.

First stage involved  lot of calculations and to my amazement I found that to form a crescent like the Roadster model illustrated in Sturmey's book and suitable for a 0.75" dia solid tyre a tube of 1" diameter was required. - how lucky can you get...... well no, I guess it makes sense as those early bicycle makers were a wily lot and were bound to pick materials available off the shelf.

Trial forming tool with first and final attempts

Final attempt after dressing

Thinking that the forming would need to be done in stages and not wanting to spend money and time making sets of rollers that would finish up as scrap, I decided to start with a simple formers to form a short section of tubing by squashing in a vice.  After a few trials I found that I could get a fairly good result in one step which would only require a little subsequent dressing to finish off  The first attempt was made without the guide rods and as can be seen went lopsided.

Rolling machine

Rolling machine drive side

Rolling Machine - awaiting Rollers

Meanwhile while thinking about all of the above I had started putting together a machine for rolling fork rake and now rolling rims.  It is awaiting rollers and strength testing but now I need to order the material for this and also find some scrap 1" x 20swg tubing to test it for suitability for the rims.  Again the basis for this has been the scrap box and Myford change wheels (shared with the forming machine).  Note also the better (longer) crank handle which will also be shared with the other machine