Stuart No1 centrifugal pump

[Steamingandy]

 I started a set of castings for the No1 centrifugal pump not available now, I’ve decided to put flanges on the inlet and outlet to give a bit more character and use O rings for seals

[crueby]

Interesting pump - what is the diameter of the main body?
 

[Steamingandy]

Interesting pump - what is the diameter of the main body?
 

The No1 is 3”

[Jasonb]

Off to a good start.

There is quite a bit of info about the Stuart pumps on this site for those interested.

http://stuartturnersteam.com/Machines/waterpmp/waterpmp.html

[Steamingandy]

Next bit impeller veins have a 6deg run to the outside

[Admiral_dk]

Funny - in my minds eye - i feel that the vanes are mirrored to what I have seen so far .... 

 ..... but all parts looks great 

[pieterb]

indeed, Admiral is correct. the curve of the vanes should be in the other way.

[Steamingandy]

indeed, Admiral is correct. the curve of the vanes should be in the other way.

As per drawing?

[Dan Rowe]

It is the photo of the impeller in the casing that is the issue generally the vanes face the other way see:
https://www.introtopumps.com/pumps-101/what-is-a-centrifugal-pump/

Cheers Dan

[Charles Lamont]

indeed, Admiral is correct. the curve of the vanes should be in the other way.

Well, that is what I would have thought too.

However, Stuart Turner were the Rolls Royce of small pump manufactures. (The main business areas were 2-stroke marine petrol engines and small pumps. Model steam engines was a sideline. The models business was eventually sold off as Stuart Models, and Stuart Turner remains as a pump manufacturer.)

The impellers on their electric centrifugal pumps were conventionally arranged with backward curving blades, but for some reason I don't understand, the pump casting kits used forward curved vanes. One reason for doing this might be that they were intended to be direct driven by relatively slow revving steam engines. Curving the blades forward normally creates a greater flow rate, at the expense of pressure.

Another odd feature of these pumps is they have no volute or diffuser space - the impeller fits inside the the circular case with only small clearances, so each space-between-the-blades can only deliver while it is beside the delivery port. For the other 5/6 of a turn, nothing much happens.

As someone who had some involvement with pump design during my career, I am at a loss to explain these design features, and am not going to waste our time on speculating, but you can be sure that S-T will have had good reason for adopting them.

 The text books (Anderson, Tuzson, Stepanoff etc) don't provide many clues for small pumps, where the hydrodynamic theory is increasingly overwhelmed by friction and viscosity effects. Steamingandy has (intuitively?) grasped this in polishing up the cast surfaces of the impeller.

[Steamingandy]

It would seem mr Stuart had other ideas, but I have seen a picture of a very early example and the shaft is mounted in the cover, maybe when they changed the design they didn’t bother changing the impeller veins round
As for the polishing of the impeller we would do it on the full size ones same principle as propellers

[Charles Lamont]

From what I have seen, the earlier pumps, with the casing split behind the impeller, also had forward curved blades.

[john mills]

I have built the no 2 
but the forward facing veins give different flow dependant on speed and head  the amount of power required
so depends on characteristics required  stuart turner  would use this shape because these characteristics suit the use driven by steam engines.
John

[Steamingandy]

From Stuart’s catalog advertising, the pumps capabilities

[Admiral_dk]

I think that I should point out that I didn't mean that it wouldn't work or was a faulty design - but that I had never seen one before were the vanes are curved this way ....

I of course hoped that someone had the explanation why .... and the much slower (without gearing) rpm of a steam engine sounds like a reasonable (if not proven) one ....

Best wishes

Per