Author Topic: Stuart No1 centrifugal pump  (Read 2529 times)

Offline Steamingandy

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Stuart No1 centrifugal pump
« on: November 25, 2021, 10:19:14 PM »
 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

Offline crueby

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Re: Stuart No1 centrifugal pump
« Reply #1 on: November 25, 2021, 11:05:20 PM »
Interesting pump - what is the diameter of the main body?
 :popcorn:

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #2 on: November 25, 2021, 11:28:39 PM »
Interesting pump - what is the diameter of the main body?
 :popcorn:
The No1 is 3”

Offline Jasonb

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Re: Stuart No1 centrifugal pump
« Reply #3 on: November 26, 2021, 07:06:42 AM »
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

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #4 on: November 27, 2021, 08:15:06 PM »
Next bit impeller veins have a 6deg run to the outside

Offline Admiral_dk

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Re: Stuart No1 centrifugal pump
« Reply #5 on: November 27, 2021, 08:27:09 PM »
Funny - in my minds eye - i feel that the vanes are mirrored to what I have seen so far ....  :headscratch:

 ..... but all parts looks great  :cheers:

Offline pieterb

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Re: Stuart No1 centrifugal pump
« Reply #6 on: November 27, 2021, 09:39:51 PM »
indeed, Admiral is correct. the curve of the vanes should be in the other way.

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #7 on: November 27, 2021, 10:21:58 PM »
indeed, Admiral is correct. the curve of the vanes should be in the other way.
As per drawing?

Offline Dan Rowe

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Re: Stuart No1 centrifugal pump
« Reply #8 on: November 27, 2021, 10:53:13 PM »
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
ShaylocoDan

Offline Charles Lamont

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Re: Stuart No1 centrifugal pump
« Reply #9 on: November 27, 2021, 11:09:35 PM »
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.
« Last Edit: November 27, 2021, 11:18:26 PM by Charles Lamont »

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #10 on: November 27, 2021, 11:19:12 PM »
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
« Last Edit: November 27, 2021, 11:28:15 PM by Steamingandy »

Offline Charles Lamont

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Re: Stuart No1 centrifugal pump
« Reply #11 on: November 27, 2021, 11:45:00 PM »
From what I have seen, the earlier pumps, with the casing split behind the impeller, also had forward curved blades.
« Last Edit: December 09, 2021, 05:46:31 PM by Charles Lamont »

Offline john mills

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Re: Stuart No1 centrifugal pump
« Reply #12 on: November 28, 2021, 07:49:32 AM »
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
« Last Edit: November 28, 2021, 07:56:02 AM by john mills »

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #13 on: November 28, 2021, 11:07:40 AM »
From Stuart’s catalog advertising, the pumps capabilities

Offline Admiral_dk

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Re: Stuart No1 centrifugal pump
« Reply #14 on: November 28, 2021, 11:17:20 AM »
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

Offline Dan Rowe

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Re: Stuart No1 centrifugal pump
« Reply #15 on: November 28, 2021, 03:24:21 PM »
Checking on the history of centrifugal pumps led to a couple of interesting links.

https://archive.commercialmotor.com/article/25th-july-1912/8/the-history-and-development-of-the-turbine-pump

"John Gwynne, who in the year 1851, took out a patent (No. 13,577)"

https://wikimili.com/en/Gwynnes_Limited

I failed to find the patent drawing but the early pumps were low head drainage pumps driven by a steam engine. I was surprised to learn how early the patent date is it predates the Worthington duplex steam pump by a few years.

Cheers Dan
« Last Edit: November 29, 2021, 07:05:29 PM by Dan Rowe »
ShaylocoDan

Offline MJM460

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Re: Stuart No1 centrifugal pump
« Reply #16 on: November 29, 2021, 10:35:06 AM »
Interesting that the centrifugal pump was patented so early, compared with the Worthington pump.  The Worthington was just a combination of two known technologies, so one might expect it to have come earlier, while the centrifugal pump had no direct hand driven equivalent, but it’s simplicity is no doubt the reason it took off, once recognised.  The same basic principle and arrangement is common to most pumps today.  One moving part and one simple to seal shaft exit, what’s not to like?  Especially, once the bearings were placed outside the seal so not subject to corrosion from the pumped fluid.  Also, can handle reasonable size entrained solids as long as they will fit through the passages.  Compare that with the jack pump that Toby has been building and shown in his excellent build log.  But I also know which one is more interesting on a model display!

Regarding the blade angle, forwards leaning, backwards leaning and straight radial are all used.  As John said earlier, it mainly just changes the curve shape.   Forward leaning gives a curve that, starting from closed discharge valve, has a rising discharge head before it starts to fall with increasing flow.  Commonly seen in large fire pumps, where the pressure is a little easier to handle if you only need one hose, but more pressure is available as flow increases, when you need all the water you can get.

Backwards leaning gives a head  curve that falls continuously with increasing flow from shutoff.  It is preferred in applications involving pumps operating in parallel for more flow. 

The radial ones I have seen most commonly are in very high speed pumps giving very high head in one stage.  But I don’t know how common they are in other applications.  They have an obvious advantage in simplicity for manufacture.

The casing also comes with subtle differences.  The concentric volute, (the casing passage around the impeller) only allows flow for part of the impeller at a time as Charles already mentioned, which clearly limits the design to lower flow applications.  More commonly the flow area in the volute increases around the periphery of the impeller to the outlet passage, allowing flow through the whole area of the impeller.    For simplicity of manufacture this was often designed as three or more curves of slightly different radius with centre’s placed to approximate a gradually increasing radius.  This casing volute form is called full emission, while the close fitting concentric casing used with straight radial blades is called partial emission.  The outlet nozzle itself is also designed as a divergent passage, which increases the kinetic energy recovery in the most efficient pumps.

I hope that helps clarify some of the puzzle.

MJM460

The more I learn, the more I find that I still have to learn!

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #17 on: November 29, 2021, 03:17:40 PM »
From what has been said ST knew what they were doing when they designed this pump, one feature I have never seen is the holes through the impeller, it only has 0.002” clearance from the casing round the outer edge so no meaningful quantity of water would travel behind it,it also has a 0.031” gap behind it, so is there a reason for the holes?

Offline Jo

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Re: Stuart No1 centrifugal pump
« Reply #18 on: November 29, 2021, 04:48:32 PM »
From what has been said ST knew what they were doing when they designed this pump, one feature I have never seen is the holes through the impeller, it only has 0.002” clearance from the casing round the outer edge so no meaningful quantity of water would travel behind it,it also has a 0.031” gap behind it, so is there a reason for the holes?

Mechanically it would act as a "pressure limit" on the output: If the water couldn't get out the higher pressure would build up down the vane until it reached those holes, then the excess water would go though the holes which would prevent the pressure effect going higher.

Jo
Enjoyment is more important than achievement.

Online astroud

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Re: Stuart No1 centrifugal pump
« Reply #19 on: November 29, 2021, 05:11:06 PM »
Wondering if the holes are in fact to relieve pressure at the back of the impeller that might cause leakage across any seal and into the bearing.

Offline Charles Lamont

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Re: Stuart No1 centrifugal pump
« Reply #20 on: November 29, 2021, 06:09:00 PM »
The purpose of the holes is to equalise the pressure on the impeller faces to minimise axial load. A well designed pump can create a very considerable vacuum, which tries to pull the impeller out through the inlet.
« Last Edit: November 29, 2021, 06:16:03 PM by Charles Lamont »

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #21 on: November 29, 2021, 08:17:13 PM »
Thanks for the explanation, there is no thrust bearing so the holes would make sense.

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #22 on: December 02, 2021, 08:48:09 PM »
Pushing on with more progress the, cover has come out well except a little blow hole that won’t make a difference, the mounting bracket was straight forward.
I have made a small base for it to bring it up to the height of the D10 crankshaft just need to mount them together on something appropriate.
Next a coat of paint to match
« Last Edit: December 02, 2021, 08:52:36 PM by Steamingandy »

Offline Charles Lamont

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Re: Stuart No1 centrifugal pump
« Reply #23 on: December 02, 2021, 10:41:42 PM »
Nice job.

(If it were mine and I was making this a permanent pairing, I think I would remove the redundant reversing gear from the engine.)

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #24 on: December 06, 2021, 07:40:52 PM »
Pump painted and mounted with the D10, flow looks adequate for both condensers, has been suggested using a gearbox to reduce the reves of the D10, I might have a go there should be enough power.
<a href="https://www.youtube.com/watch?v=VF96ZQuXK6k" target="_blank">http://www.youtube.com/watch?v=VF96ZQuXK6k</a>
« Last Edit: December 06, 2021, 09:20:04 PM by Steamingandy »

Offline crueby

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Re: Stuart No1 centrifugal pump
« Reply #25 on: December 06, 2021, 07:49:04 PM »
Very well done!

Offline Admiral_dk

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Re: Stuart No1 centrifugal pump
« Reply #26 on: December 06, 2021, 09:11:48 PM »
Great result - both as pump and looks  :ThumbsUp:

Offline Kim

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Re: Stuart No1 centrifugal pump
« Reply #27 on: December 06, 2021, 09:37:34 PM »
That's cool!  I love seeing model engines doing real work!  Your pump is working great!

Kim

Offline propforward

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Re: Stuart No1 centrifugal pump
« Reply #28 on: December 06, 2021, 10:22:54 PM »
Fantastic - really nice result and great to see it pumping like that.
Stuart

Forging ahead regardless.

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #29 on: December 08, 2021, 03:58:23 PM »
After a suggestion I tried a gearbox looks like I will be making another base, the D10 handles the set up with ease
<a href="https://www.youtube.com/watch?v=-NAeV2GzZ9g" target="_blank">http://www.youtube.com/watch?v=-NAeV2GzZ9g</a>

Offline crueby

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Re: Stuart No1 centrifugal pump
« Reply #30 on: December 08, 2021, 04:34:26 PM »
That gearbox made a huge difference!  What ratio is it?

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #31 on: December 09, 2021, 12:02:25 AM »
That gearbox made a huge difference!  What ratio is it?
The ratio is 3.5-1 I thought a bit high but seems to be ok

Offline Jasonb

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Re: Stuart No1 centrifugal pump
« Reply #32 on: December 09, 2021, 07:16:27 AM »
It certainly does increase the flow of the display setup but bear in mind that if you actually want the pump to do real work eg lift water to a head or against a restriction then it will have an adverse effect as the engine has less mechanical advantage.

Offline Charles Lamont

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Re: Stuart No1 centrifugal pump
« Reply #33 on: December 09, 2021, 05:36:15 PM »
It certainly does increase the flow of the display setup but bear in mind that if you actually want the pump to do real work eg lift water to a head or against a restriction then it will have an adverse effect as the engine has less mechanical advantage.
Probably not. As we saw with the direct drive, the engine could be run at, hmm, let's just say very fast, without the pump giving a huge output. Geared up, the pump is giving a good flow rate at modest engine rpm with very little head, and we are told the engine is well on top of that delivery at this gearing.

Centrifugal pump behaviour is nothing like a positive diplacement pump. From no head, or next to none, as we have here, as the head is increased, the pump will come into its 'design' range, where, for a given shaft speed, flow rate x head is maximised. This is the condition at which it will absorb the greatest power (at that speed) even though it is working at its best efficiency. Note also that flow rate x head = power output. If the head is increased further, the flow will start to decrease faster than the head increases, and the power absorbed will be less.

Increase the shaft speed, and the pump will deliver greater flow at no head, and greater head at no flow. If you increase head and speed commensurately, so as to stay on the max efficiency duty, then the power absorbed increases as the cube of the speed. Roughly, the flow is proportional to the speed and pressure proportional to the square of the speed.

All of the above is generalisation, and describes a pump that is well behaved. Some designs can be unstable under certain conditions. The Stuart No 1 has design peculiarities, but I don't have much idea as to how they would affect the performance characteristics in practice.

Offline Zephyrin

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Re: Stuart No1 centrifugal pump
« Reply #34 on: December 09, 2021, 06:32:22 PM »
you may easily estimate the work and power done by the pump, with an amount of water lifted to a measured head, in a definite time...and compare the different conditions.

this is really a beautiful and efficient pump !

Offline john mills

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Re: Stuart No1 centrifugal pump
« Reply #35 on: December 09, 2021, 07:23:04 PM »
I have a stuart no 2  i have it direct coupled to the virus engine  with it drives with ease. the engine is 1" bore and stroke twin single acting
the no 2 pump is larger 3/4" inch pipes. i would think the engine you have would have plenty of power with the gear box to drive the pump
at a reasonable speed with out the engine having to rev as fast as the pump needs .you will find when you try it.
     John

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #36 on: December 09, 2021, 07:44:34 PM »
The pump will be supplying the cooling water for the condensers, it is an open circuit, so only the restrictions is the pipe work so I think this will copy happily.

Offline Steamingandy

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Re: Stuart No1 centrifugal pump
« Reply #37 on: December 14, 2021, 07:51:30 PM »
All finished ticks over nicely
<a href="https://www.youtube.com/watch?v=6T_8E-L0Kto" target="_blank">http://www.youtube.com/watch?v=6T_8E-L0Kto</a>

Offline RReid

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Re: Stuart No1 centrifugal pump
« Reply #38 on: December 14, 2021, 08:10:31 PM »
That's lovely work all around. Well done! :ThumbsUp: :cheers:
Regards,
Ron

Offline crueby

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Re: Stuart No1 centrifugal pump
« Reply #39 on: December 14, 2021, 08:28:30 PM »
The pump and engine are well matched now, love it!  Just noticed what I think is a boiler feed water pump on the left end of the engine as well.   :ThumbsUp: