Part four by Jason Ballamy

Next was the pulley that would have taken the drive from the engine up to overhead line shafting via a flat belt. The photos show a few differences between the original and AM's interpretation such as 4 spokes vs 6, a split clamped hub and a narrower rim.

I started with the hub, a bit of 1" bar was drilled 1/4" and parted off then two shallow 3/8" grooves milled in opposite sides to take a couple of lengths of 3/8" sq bar.

The three parts were silver soldered together then drilled for the clamping bolts after which they were cleaned up and all edges rounded off. I subsequently drilled the hub out a bit under finished size so there was less metal to heat up on the next soldering stage.
I drew the pulley out full size on a bit of paper and used that to determine the positions of the various arcs to form the spokes. These were then marked out on some 1/8" sheet and cut and filed to shape, testing against the drawing for fit.
A nice man on e-bay provided some 100mm OD x 4mm wall EWR tube and a suitable length was sawn off, the ends were tidied up overlength on the lathe.
When heating the rim of a flywheel or pulley it tends to expand which can make the gap between rim and spoke too large for the solder or pull against the hub and distort the finished item when it cools. I decided to solder in two stages, the first being the spokes to the rim. Each spoke was set on a nut to pack it up to height and an off cut used as a makeshift hub, the spokes were then soldered into place.
A quick clean up of the inner spoke ends and the hub was set in place with a toolmakers clamp to ensure the previously soldered lugs would not move. This way I could heat the hub and not have the rim expand.
And here it is after a dip in the pickle and a light wire brush to remove flux.
Back to the lathe held it by the inside of the rim to bore the hub true and profile the rim to a slight crown. If you look at the lines on the rim you will see it is in 5 sections, the middle is parallel to the lathe axis, the ones either side of that are at 1deg and the outer section at 2deg, these will be blended later into a shallow crown.
And here is the finished pulley, you will see that before soldering I added a 1/64th slot 0.040" deep around the middle of the hub to look like a dummy split line.
Just a little work to clean up the solder fillets, coat of paint and then mount on an arbour to blend the rim and that’s another part off the list.


Two discs were cut off my ever shrinking piece of 80mm dia cast iron bar by hand to approx 1/2" thick to become the eccentric straps. These were then popped into the lathe and faced off to give a finished thickness of 3/8".

I then did a quick bit of layout with a pencil to see roughly how much I could take off to get a flat reference face, this and the next few stages were all done with the discs held vertically in the mill vice and cut with a 1/2" end mill.

With the reference face established the discs were blued and marked out with the height gauge and the four extremities cut, you will notice I left an 1/8" strip in the middle to allow for cutting and cleaning up the face.

The flat faces for the bolts were then machined and some of the waste removed just by eyeballing clear of the line. The holes were also drilled at this setting. In addition I formed a flat to screw an oil cup into, these can be seen on the original photo but are not on AM's drawings.
The discs were then cut in half with a hacksaw and machined back to the line, the socket head screws are only there while there is more machining to be done.
The centres were marked and the strap mounted in the 4-jaw to bore the hole to 1 3/4".
They were then held by this hole on the rotary table to clean up the outside profile using a 1/4" FC-3 cutter
I then knocked up some filing buttons to round off the bolting lugs, quick tip when doing this the nut often works loose so give it a quick tap with a hammer which makes it slightly oval and it won't come loose again.
Add a couple of fitted bolts, nuts & locknuts and thats them done save for a bit of clean up before final assembly.
With the eccentric straps done the next logical parts were the sheaves, they were roughed out from 2" bar when taking a break from sawing off the CI for the straps.
With the straps completed they could be used to test fit the final sizing of the sheaves, I then parted them most of the way through finishing off with a hacksaw.
Then popped back in the lathe and using the soft jaws they were faced off to finished thickness
The throw was then marked out and punched with the optical punch and once clocked true in the 4-jaw the hole was bored.

Just a couple of grub screw holes to finish them off and here they are with their straps.