Southworth rotative pump

Started boring the cylinder and gave gone for 3/4” steam and 1/2” pump cylinders; my thinking is that if for some reason I mess up, I can go to the larger bore diameters 😉

I’ve left 0.016” over length to bring down to size

Steam cylinder boring is complete and is to the correct length. Visually the bore does not appear central to the outside of the cylinder, however, the distance from the centre of the bore to the port face and to the bottom of the foot are correct; these are the critical measurements so I think the jobs a good'un 

Strange things ............ the drawings state the bore for the steam cylinder can be 1" or 0.625" and yet the Blackgates catalogue (see below) states 1" or 3/4" .........I phoned them this morning to order the missing eccentric strap and at the same time asked for a set of 'O' rings for the 3/4" steam cylinder and 1/2" pump cylinder which they are sending me?!?

I'm not sure what will be arriving but will have to make the covers fit the the 3/4" bore I made, I can't think of anything else which would be impacted?? Maybe the piston 

EDIT The eccentric strap casting was only £3.52 which was a pleasant surprise, and 'O' rings just a few pence 

Port holes drilled and cutouts for the steam passages made; the length and depth was not specified so I made a guess. Using these measurements and some basic trig, calculated the angle for the steam passages to be approx. 21.5 degs.

Unfortunately I had everything lined up at the correct angle to make the steam passages and realised the cutouts were neither long enough or deep enough and I would have ripped up the inside of the cylinder with rhe drill bit...... anyway best to find out before making a mistake.

The steam passages are the same diameter (5/32") as the ports which I haven't seen before, I'll have to mill the cutouts deeper and wider allowing for the drill bit to sit in the bottom edge of cutout without the possibility of damaging the cylinder

Or just drill in parallel to the bore, looks like you will have enough overlap of the cylinder end covers. As you are not making pump that will be working under load the tiny gain from the more direct angled drilling is not worth worrying about.

Yes, I was thinking the same, might be far simpler, I was also thinking to be certain I could deepen the ports as they are quite shallow at 3/16"?

Yes make them deeper then you will get more coverage of the hole by the cylinder end covers as it can be placed closer to the main bore.

Thanks Jason, that worked out very neatly and nicely; the steam passages and inlets joined up perfectly and the exhaust too

Cylinder needs the various holes for both end covers and the valve chest, but I'll be making those first to get the postioning correct

Question

Does that gap on the sides of the valve chest and valve matter or should they be relative close to the walls of valve chest as a guide for the valve?

The reason I'm asking this question is that I've cleaned up the valve chest and the width of the recess is already bigger than the 7/16" specified on the drawing at 0.536" before machining

I'm thinking clean up the side walls to make them even, then increase the width of the valve to fit, well enough to slide comfortably? The specification as given is 0.437" for as the width of the valve chest and 0.406" for the width of the valve, so I could replicate a similar difference but wider ..............?

As long as the valve does not rub on the sides of the chest, with any sideways slop there may be in its movement included, any extra gap does not really matter.

Thanks Chris 

In which case I'll just tidy up the inside walls of the valve chest  and leave the valve at its originally specified dimensions 

Bit of room won't hurt. The valve does not have a lot of clearance between it and the chest cover so any clearance at the sides will help the air get from the inlet in the side of the chest to the far inlet port.

Made good progress on the valve chest, marked up ready for a bit of drilling, but what am I missing (apart from some brain power) when it comes to the valve 'gland'?

The valve chest drawings states copy from item 43, item 43 is called the valve rod support and shown in one of the diagrams below??

I'm wondering given the 0.259" diameter indicated on the valve chest drawing if there should be a 'o' ring in the recess? I can't see any item which looks like a gland where the fixing holes indicated would take their position......

The video, which is the only photographic image of the completed engine, does show some sort of gland but I can't see it properly .......maybe I need to trawl the drawings again and look for a similar shaped object

EDIT: Ignore above, found it, well I found there are 2 different components, both marked as no. 43! see last photo .................I could have understood it they were all marked as no.42 

....I could have understood it they were all marked as no.42   

    Nice one - and so is progress too 

Per       

Yes an O ring goes in the recess hence the quite specific size.