Thanks for the comments

At least with the new drawings you should actually have dimensions to read as many times as you like rather than them being completely missing or simply not possible to achieve from the actual castings. But as my lathe is imperial and does not have a DRO I can confirm that the world is not going to end but I should inform you that it is not flat.

I’m not quite sure yet whether Blackgates will supply both sets of drawings or give the buyer the choice of the old imperial or my new metric ones so those with old iron need not have to take their socks off.

As Hopper says more of the hobby machines are coming with just a metric option and the same goes for tooling and equipment with metric being more readily available at reasonable prices.

Additional photos to go with part 1 of the article in issue 4774

A square on view of the first cuts to the bed plate. The two Sharpie marks indicating where the locating buttons are touching can also be seen more clearly.

Locating the datum point with an edge finder – between the pedestalls and mod way along them.

Cylinder mounting holes and bearing cap holes spotted prior to drilling

Marking the bearing ctr line by dragging the end of a spotting drill over the machined & blued surface

Spot facing the underside of the bed casting for the cap head screws that retain the cylinder.

marking the posistion of the saw cut to split the bearing cap casting into two

A light skim cut to clean up the sawn surfaces

Milling the two ears to thickness

Cont’d

Milling the oil pocket to width and height with a 1mm corner radius 6mm cutter to leave a small fillet

With the caps now screwed into place they and the tops of the pedestals can be milled to width

The casting is now held on it’s side and a wobbler used to locate the previously scribed ctr line.

The bearing holes being reamed to 10mm diameter although they could also be bored

using the shank of a drill to locate a filing button the curve of the cap can be marked prior to filing.

The last job on the bearing caps if to knock off all the corners with a needle file to give a softer cast look.

Next time I will describe the Cylinder and its associated parts.

Castings and Drawings available from Blackgates, see their Clarkson Catalogue

Nice looking compound John.

I also feel that the flywheel is rather thing, I wonder if they came up with the compound first where the two flywheels work OH in combination with the separate drum. They may then have decided to do the single and simply used the same casting, hence it not looking quite right. It does run with teh skinny one but is smoother at low revs with the heavier rim.

I don’t know if you have seen the article which has now started in the Mag but I give options to use the flywheel as supplied as well as a drawing at the end for modifications including the larger rim, recessed face to the valve chest and similar to the crank disc to give a counterbalanced look.

This was built from a set of compound castings that were missing a few bits, like yours an old set of castings. I had heard that they were known for being hard, some initial clean up cuts were not a problem but I did take the precaution of cooking a few of th ethinner castings prior to machining and had no problems.

The drawings I have done are not just a mathmatical conversion but redrawn to suit the actual size of castings and I was able to get all the parts from them. Several alterations along the way for a better look too including things like avoiding the need for that clearance notch in the end of the trunk guides

A few more extra photos to go with part 2 which is in issue 4775

Initial skim cut to just clean up the port face

Then a clean up pass of the bottom surface

Checking the casting is square to the chuck face while clocking in the ctr mark

Skim cut off the cylinder end then start drilling out so you can get a boring bar in.

Casting held the other way round and clocking in the bore prior to turning the second end

Second end turned

Bottom face after final milling

Port face after final milling

Milling the exhaust pipe boss to length

Clocking in the trunk gude with the indicator on the smaller diameter behind the flange

Part left in 4-jaw and moved to the mill for drilling the holes

Lap made from a simple wooden dowel coated on 600g silicon carbide powder and oil

Turning back cover spigot to fit trunkguide

Test fitting

Reming piston rod hoel ofter spotting and pilot drilling

Front cover spigot being turned using softjaws to hold thin work without wobble

On 22 May 2026 at 21:45 Neil Wyatt Said:

This is a great idea for articles that would otherwise be too photo heavy.

I think that compound version is great too. I love the tiles as well.

Neil

Worth encouraging other authors to do the same. I’ve been doing it for several years right since my first build article in ME

Anyway on with the additional images, this time related to the eccentric parts.

The raw casting.

Cleaning up the first side before reversing in the chuck to do the other side

Setting the scribed line parallel to the vice jaws

Spot drill, tapping drill right through, clearance drill part way and thread

Sawing in half

Cleaning up sawn edges

Clocking the dubby ctr location to run true. Masking tape to stop parallels falling out a schuck is rotated by hand. REMOVE parallels before machining.

Making a start on machining the outside

Pocket for the rod