I can't spot anything in the indexes of articles. May be worth looking through Stan Bray's build in 1999 , 4101 covers the parallel motion.

Also contacting Blackgates who now sell the engine to see if they have anything different on their drawings.

J

John,

I've got the Blackgates drawings. I can't access them until Sunday but I'll let you know then what the dimensions are.

Rod

John,

I have built the Sanderson Beam Engine and the parallel linkage dimensions were kept as the original Clarkson drawing. However, check the beam casting bosses on both sides of the beam to make sure that holes you are going to put in them are at the same centres as the horizontal rods of the parallel linkage. It would look really bad if the holes were not central to the bosses. If the bosses are slightly out due to a bad pattern then either machine the bosses to reposition them slightly or adjust the horizontal rods to suit. The important thing to remember when erecting the engine is that when the beam is horizontal, the crank should be horizontal and at that point the parallel linkage prescribes a right angled parallelogram. The short links to the parallel linkage support bracket are also horizontal at that time. To achieve those conditions you may need to shim one or more of the crankshaft bearings, the column height and the parallel linkage support bracket face. I took photos of all the main machining set ups for this engine and also the erection of the engine. If you get in touch I can send you copies on a CD if they would be of interest.

Geoff

John,

On full sized beam engines the length of the horizontal links are usually set at one half of the distance from the piston rod hole to the beam pivot. The horizontal links have to be that length or the geometry doesn't work, so you did the right thing in setting the distance at 3.023. Curiously, on my set of drawings which are Harry Clarkson's original issue of October 1969, the horizontal links are 3 1/32 ins. long which is close to your new length. (the vertical links on my drawing are 1 3/16 ins. and the short anchor links are 19/32 ins.). It is perhaps obvious but another measurement to adjust if necessary is the length of the piston rod because when the beam is horizontal and the parallelogram has right angles the piston should be at mid-stroke between the steam ports. I've also built Clarkson's Steeple Engine. An experienced engineer wrote an article in ME in 1979 stating that the Steeple Engine was impossible to build due to multiple problems including drawing errors. He was not wrong! One of the drawing errors in particular is very difficult to work around with the castings as they were supplied.

Geoff

John and Rod,

I've looked further into the parallel linkage dimensions to find the ideal length of the shorter anchor link using fixed dimensions for the horizontal and vertical links. I got the drawing board out and produced a drawing of the linkage several times scale size and marked on the linkage position with the beam up , horizontal and down. Using 3ins. (or a few thou over depending upon the casting bosses) and 1 3/16 ins. for the vertical links the required length of the anchor links is 3/4 ins. It looks like the length of the anchor link on the original Clarkson's drawing of 19/32 ins. is not ideal and that this has been corrected at some time to 3/4 ins. which will give a better result as now shown on the Blackgates drawing.

Geoff

John and Rod,

My castings were an old set of Clarkson's castings bought about fifteen years ago. They are iron castings rather than the gun metal castings and aluminium base supplied these days by Blackgates. The old castings are to my mind preferable as the fluting on the connecting rod and column are finer. Also, certain parts actually need to be left bright steel which they cannot be with the gun metal castings with the result that certain areas end up painted which really should not be. The downside of the old Clarkson's iron castings is hardness which can be problematical. My drawings are also dated 18/12/68, 14/2/69, and 18/10/69 but the beam dimensions do differ. From the piston rod end the hole centres are 3-1/32, 1-13/32, 1-19/32, and 2-27/32. It is possible that these differences are a result of having new patterns made as over forty five years it is likely that there will have been more than the one set of patterns. The anchor link dimension though I think is different. It will have been changed at some time from 19/32 to 3/4 to be geometrically correct and to reduce friction/binding. Drawings like this from the 1960s were produced by a dye-line process using a translucent Velograph film and ultra-violet light. It was not uncommon for changes to be made by scratching out the old dimension on the film and writing in a new one. Sometimes you could detect the changes as they left a sort of halo around the dimension. There is a change on the Steeple Engine drawing like this with a halo although the new dimension is still incorrect. Usually changes are dated and described in a box at the bottom of the drawing but not so in the case of Clarkson drawings.

Geoff

I cut my modelling teeth on beam engines, there is something special about slow running. Now I want one! What are you doing for a boiler?

Fizzy, my steam experience is strictly limited to a 10V 30 years ago, oh and a well stalled Jenny Lind. I think it will probably be compressed air powered but my particular ethic is that the model must be steam capable – so the correct heat resisting materials must used.

Jason, you may well be right Did I mention the orphaned Lady Stephanie? Perhaps I'm laying in a stock for when the revolution comes

Cheers,

Rod