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Member postings for Paul Horth

Here is a list of all the postings Paul Horth has made in our forums. Click on a thread name to jump to the thread.

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Thread: steam turbine and generator
13/01/2011 21:19:36
A little more information on this subject:
 
Ages ago, I gave away my 1980s Model Engineer mags, but not before I had made copies of the articles I wanted to keep. There were a couple of small steam turbines described, which might be of interest to others ( if you are not already ahead of me).
 
Terry Timms, A Steam turbogenerator,(mounted on Sweet Pea), 17 January 1986.
A. Sherwood, Tinkerbell, a 5 in. gauge switcher (with turboalternator), 2 January 1987.
 
Both of these used similar rotors, about 1 inch dia with Stumpf type cavities. They drove alnico magnets with external stators with coils wound, and could light up a couple of small bulbs. the jet sizes were small - 0.033 for Timms, 0.018 for Sherwood. So these devices worked on a small steam flow.
I was aware of these designs, but I had hoped to find a way to avoid winding the coils by using an existing electrical rotor. However I take some encouragement from their success and I might have to follow one or other of these designs.
 
Paul
13/01/2011 19:01:38
Thanks again, gents, for all your comments.
 
KWIL - I am a member at Guildford and I have seen the small turbine that you describe mounted on a loco. That is the kind of size and shape that I was thinking about, however I didn't find out what was inside.
 
Keith - that's a generous offer, yes please, I would be very interested to read the Chaddock series if it's not too much trouble, I'll gladly pay the cost.
 
Dick - I was considering the concept of drilling holes in the periphery of a rotor to form an impulse wheel as you describe, thanks for confirming that this does work. I take it that you form the passages from both sides so that they meet in the middle to form a reversed path from inlet to outlet side. I would have to lash up a dividing fixture on the vertical slide mounted at an angle to the lathe axis.
Fitting magnets into the disc is a clever idea. If I understand you, the poles would face axially so that the coil would be mounted on the face of the casing, and there should be two magnets on a diameter either side of the central shaft, to keep the rotor balanced? That at least eliminates the coupling to the electrical rotor. I'd have to learn how to make the coils.
 
Paul
 
13/01/2011 11:33:03
Thanks again for the latest replies, I am benefiting from this education. I don't really have the motivation for a lengthy period of experimentation and development, so I am grateful to learn from those who have already put in this effort.
 
What I had in mind was something that looks like the US Pyle-National loco turbine, with the turbine and generator direct coupled and in line. That's why I wanted to avoid reduction gearing. It may be unavoidable that the practical speed limit means that the efficiency and power output are very low with this arrangement.
 
Donald - I remember the article by Ray McMahon, I have it somewhere. I think he used an ex cycle dynamo? I will check.
 
Jeff - I remember the Southworth turbine. That was an ambitious project and was for direct drive to the loco (no generator) and had the full steam output of a large boiler. it was impressive that he got this to work, but i was after something smaller, which might not be practical.
 
Richard Parsons - destiny in that name! I appreciate your sharing of many years of experimentation, enough to put me off, I would say. I do understand all the points that you make. I was aspiring to make an impeller rather closer to the conventional impulse wheel than the Stumpf, but I do accept that the Stumpf will work, although the efficiency would be poor. I am too lazy to attempt muli-stage turbines. Anyway, first I want to establish what the electrical end should be, this is really what prompted me to write in to this forum.
 
Some years ago the ME had an article about a Swiss gentleman who had built a turbo-electric loco in Gauge 1. He had fitted a steam turbine and generator into a Gauge 1 loco  which drove motors in the train and was radio controlled. A truly amazing achievement. I think his turbine had chevron-shaped passages milled into the periphery, and drove a special motor of Swiss manufacture, but he did not include details such as the rpm. I don't know if such motors are available here in the UK.
 
For bearings I had thought that those used by the IC engine fraternity would be OK...???
 
Provisional conclusions - a Stumpf impeller connected to a small high speed DC motor at about 15000 - 20000 rpm might yield a tiny dribble of power? and might fall apart soon? I wonder if it is worth pursuing this?
 
Thanks again
Paul
12/01/2011 23:21:01
Thank you all for your replies, all within an hour, amazing. These are helping me to think about the practicality of this problem.
To reply to some points raised:
Alan ,and J ohn - I was hoping to avoid the task of designing and building my own generator, as I consider both designing and building an electrical machine to be well beyond my skills. If I cannot make use of a commercially available machine, then I had best stop now I think.  I have read a book on the Tesla turbine but I can't understand its principle - it seems to work on friction between the discs, and i can't apply my thermodynamics and fluid flow to the concept.
David - I haven't yet gone to the site yet, but will do. Your point about steam demand is absolutely right. I want to limit the flow to about 3 lb/h, as the traction engine boiler can make up to about 12 lb/h. This is a small flow and one problem is to make the turbine passages small enough so that the steam velocity is still up at about 300 m/s in the wheel. I would use a jet of about 0.05 inch diameter.
Terry - maybe my speed doesn't need to be so high, but even 20000 rpm would be high for a typical motor. The turbine efficiency drops off rapidly at lower speeds and so I wouldn't get the power - but I don't really know?
 
Thanks again,
 
Paul
12/01/2011 21:44:50
I am thinking about having a go at a small steam turbine and generator. I have in mind a machine which can be mounted on my 2 inch traction engine (the source of steam) and which would be reasonably to scale. A turbine wheel of about 1.5 inch diameter and a generator about the same diameter and about 2 inch long. Enough power to light a few little bulbs, say 1 - 5 watts.
Now, such a small turbine rotor will have to run at a very high speed - 50000 to 100000 rpm. Leaving to one side the question of how to produce the blades or passages in such a wheel (which i am still thinking about), my  next question is where can I find a small electric motor which can be run as a generator at this kind of speed? It would need to be direct-coupled not geared down.
Most small motors that i can locate seem to be specified for 6000-10000 rpm which I think will not be high enough.
 
If anyone has any suggestions or experience of making a small steam turbine, then i would be most interested to hear from them.
 
Paul
Thread: Amberley 2010
29/09/2010 21:50:05
Mine is the green 2 inch Durham engine, my knees just in Jason's photo.
It was running all day without a problem, I used all my coal!
 
Paul
Thread: A professional boiler - poor service
11/01/2010 13:40:50
Laurence,
 
I agree completely with your comment about full size pressure vessels, I have spent my career in the oil and gas industry. and know how full size engineering is done. 
These model boiler makers are self-certifying. I have to take on trust that he has fitted the crownstays correctly (or at all???).  His inability to follow drawings does make my blood run cold, a bit.
I reassembled the engine by end September, and steamed it once in October in my back yard, because I don't yet have a club test or certificate. That will come in March.
This whole story has taken two years out of my steaming.
 
Lesson - as David Clark says, get references, go to someone recommended, even if they quote a long delivery time.
 
Paul
19/07/2009 22:20:57
I have just returned from holiday, and i'd like to thank you all for the messages of support.
 
I would be glad  to pass on the names of the suppliers that I dealt with to anyone who sends me a message. That includes the editor David Clark, so he can use this info as he should judge best. He may know of others who have had similar difficulties wit these suppliers.
 
Paul
13/06/2009 23:43:37

Last summer, I noticed that the boiler of my 2 inch traction engine was leaking. After investigation I decided that I needed a replacement professionally made boiler. I obtained quotes from several firms advertising in the Model Engineer, and gave the order to the firm who offered the best delivery time, which was 4 months.>>

What a fool I was.>>

The order was placed on October 22nd, the boiler has finally been delivered yesterday, a week short of 8 months from order. It had arrived for the first time two weeks ago, but it was not to the drawings in some important respects and had to be returned. 

This delay means that by the time I have reassembled the engine and obtained the club test certificate and insurance, I will have missed most of this season’s running. >>

> >

I was very angry with the attitude and the performance of the firm that I dealt with. My enquiries about progress in February and March were fobbed off. When I enquired in April about this boiler, I was patronised and told by the manager that he didn’t know if the material had been ordered, and he didn’t have any control over what his boilermaker was doing. When I questioned whether this was a professional way to conduct business, I was told bluntly, any more insults and I could have my deposit back.>>

Following this response, I made some enquiries, and found that he had outsourced the boiler to another supplier who also advertises in the Model Engineer. Speaking directly to the boilermaker was now possible, but I found (in mid-April, 6 months after my order) that the material had just been ordered, then he was going on holiday. >>

The boiler was delivered on May 29th. The cylinder saddle pad was in the wrong place so I couldn’t attach the cylinder. There were only 4 hornplate stays fitted on each side, instead of 5, and they were a smaller size than on the drawing. Back it went, at my expense of course. I had by now paid the full balance.>>

Now I have the boiler at last, but I am about to go on holiday.

Today I found a further error, the turret bush is too small to fit my turret, was not made to the drawing, I will have to make an adaptor.
>>

I have found this whole experience really frustrating. I was paying for a professional service but got something far inferior to that. I didn’t even get a receipt until I asked for it.>>

> >

I won’t name the suppliers on this forum, but if anyone is considering
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