Southworth rotative pump

[Sanjay F]

Hello all

It's time for a new project whilst closing off the Stuart Steam Hammer. Having looked under the bench the Southworth rotative pump grabbed my attention; it's something a bit different and I again fancied something which is not strictly an engine. This time it's a fresh, but old set of castings which have been untouched by human hands or at least another model engineer. 

It appears from the drawings there is the Scotch yoke or a non-Scotch yoke version which can be built from the same set; I'm going for the non-Scotch yoke as it appears to me like the more interesting and different option .......let's  see

I've been trawling the internet to try and find some pictures of a completed one without success. I have however found this Keith Appleton video where you can see one running at 3:25. If anyone has got some photos please post them and if someone has built one of these let me know as it's always good to find out if there are any pitfalls beforehand.

<a href="https://www.youtube.com/watch?v=6sA5yh7Ast8" target="_blank">http://www.youtube.com/watch?v=6sA5yh7Ast8</a>

[Jasonb]

Looks like you may be missing a casting as there are supposed to be 9 GM and 2 Iron castings

Bit of a poor photo

[Sanjay F]

Bugger! Well spotted you’re right

It must be the eccentric strap; I wonder if Blackgates are attending the expo in 2 weeks, I’ll get them to bring one along?

EDIT They're not on the suppliers list for the expo which is a shame ....

[Sanjay F]

This is different:

- the steam cylinder can be bored 1" or 0.625" then piston, end covers made the appropriate size
- the water cylinder can be bored 0.625" or 0.500" then end covers made the appropriate size

I'm not really sure how the bore size will impact the pump functionally but need to make sure that I pick a size and stick to it!  My instinct is to make both bores 0.625" and there's less chance of a measurement error on all other associate parts. It's not like the pump is going to be used in anger! 

[Charles Lamont]

Looks like a good project I will follow with interest. On the bore sizes, if it might ever actually be used as a boiler feed pump, the steam cylinder needs to have a larger bore than the pump. I would definitely go 1" and 5/8".

[Sanjay F]

Looks like a good project I will follow with interest. On the bore sizes, if it might ever actually be used as a boiler feed pump, the steam cylinder needs to have a larger bore than the pump. I would definitely go 1" and 5/8".

Thanks Charles, I didn't appreciate one had to be larger than the other when used as boiler feed pump; to be honest it's not going to be, but maybe I'll do it to be faithfull to the original full size version 

[Jasonb]

You need more pounds per sq inch on the steam piston than the pressure against the pump piston if water is going to get into the boiler. So as the pressure is the same the way to get the power to move the water is to increase the square inches of the steam piston.

[Sanjay F]

Thanks Jason/Charles - that does make sense 

Machined the 2 x flywheels today. They were really nice to machine and turned out nicely too after I did them the proper way in the 4 jaw not holding by the hub in the 3 jaw! 

[PaulR]

Will you need a 5-jaw chuck to do a 5-spoke variant the 'proper way'? 

[Sanjay F]

Will you need a 5-jaw chuck to do a 5-spoke variant the 'proper way'? 

The spokes on this flywheel only just fitted with the minimal clearance between the jaws. 5, 6, 7 how many jaws can you get/need! 

[Charles Lamont]

May I suggest a small chamfer on the inside edges of the rims to remove the rough edge and ensure the rim appears to run true. It's one of the little details that make a difference.

[Sanjay F]

May I suggest a small chamfer on the inside edges of the rims to remove the rough edge and ensure the rim appears to run true. It's one of the little details that make a difference.

Sounds like a good idea, one for tomorrow morning 

[Sanjay F]

Made a start on the steam cylinder with a clean up of the foot and cylinder ends. I just need to get them close to square/level as the actual length will be machined on the lathe.

I'm using the fly cutter with insert which was talked about on a previous thread ...........so far, so good 

[Jasonb]

You have got the side of the insert cutting, it should be the face. Also use a L/H tool not a R/H and while you are at it put a **GT insert in rather than the **MT

That cut surface should be bright and shiny.

[Sanjay F]

Oh dear, that explains a lot! 

I was wondering why it was such a brutal cut compared to last time  In fact I wasn't happy with it and reverted to the face mill and got a lovely shiny finish ..............

Let me try again with it when I move onto the pump cylinder! In the meantime the steam cylinder is cleaned up and ready for some lathe work