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[frog32]

Hi.
I have started to build up a steam plant,using a Maccsteam boiler and Graham TVR1 engine.Before I can finalise pipe runs I need to obtain a Servo controlled steam valve to operate the engine. The only one I have so far found is the one supplied by Polly Engineering but I do not know anyone who at present is using it.
I would therefore be grateful for any help or advice from any members who are using the same steam plant as I am, or have experience of using the Polly steam valve.


Regards Roger.

[kiwimodeller]

Roger, the Polly/Bruce Engineering valve is probably the cheapest on the market and seems to work just fine. I have used one in the past as a throttle and am currently using one at present as a whistle control valve. The only drawback is that there is no mounting bracket, it just mounts in the pipeline. Others are available from Clevedon Steam http://www.clevedonsteam.co.uk/products.html . There also used to be a larger rotary type one listed by RDG http://www.rdgtools.co.uk/acatalog/Models_and_Steam_Fittings.html which works really well but I dont see it on their webpage now but it might pay to email them. If you do not have any luck let me know and I will look out the Model Boats mag that gave an email contact for 21st Century Steam who also had the larger one but they are out of stock at the moment, I am waitng for more. Hope this helps, cheers, Ian.

[derekwarner]

Roger.......another 90 degree servo operated  steam stop valve is by the French ANTON & best described here by KRAMER...as their V31 Item ......being a Swiss distributor ....
It is certainly a very tidy & compact unit.......as you have found......such valves are nearly as rare as rocking horse teeth  ...........Derek
 http://www.kramer-steam.ch/joomla/index.php?option=com_wrapper&Itemid=55

[frog32]

Hello Ian and Derek
 
Thank you for the information.  It's amazing that my first replies have come from the other side of the world!
 
Ian.  I did know about Clevedon Steam - they are approx. 17 miles from me.  I eventually got hold of Jerry this morning only to be informed that the two controls he has on his website are for a whistle and gas control and are more of an on/off control rather than a variable control.  He has been asked many times about a throttle control and has a friend whom he has asked to build one from his design but that's for the future.
 
Mainsteam also had one on their website a couple of years ago and I have also contacted him.  He did supply the cylindrical type but was not happy with the overall performance of it and so no longer stocks it.
 
Ian.  I have had a look at the radio controlled valve on the Poly Engineering site.  I couldn't get much information on how sensitive the valve is.  I note that you have used one; would you say it gives a smooth start up to maximum or does it just tend to go from stop to full power immediately?
 
Derek.  Thank you for the information on the Kramer valve.  I can't seem to get an up to date price because his English website doesn't seem to be up and running yet.  However, it does seem to be very expensive; the only price I could see was 61 Swiss francs.
 
I just find it amazing that there are very few options in this field; is it because most ready made engines come with the throttle built in and anyone who is scratch building an engine would be making their own throttle so are the Graham TVR1 kit builders the only people who are looking for an 'off the shelf' servo controlled throttle?
 
Can any other members throw any light on this query?  Thanks.
 
Cheers, Roger

[kiwimodeller]

Roger, it was some years ago that I used the Polly valve as a throttle and I was using a small valve to control a fairly large engine so it probably wasnt a fair test. From memory it used to be a bit on/off when starting up from stopped but did a good job of varying the speed once running. Now I have just remembered that the valve in my River Queen is a Polly one. The engine in that is a Graham VR1A single cylinder and the control off that is very good. I am sure it would handle the Graham twin. With all the valves I have tried I have found that there is a delay, particularly when slowing down to come alongside. I presume that what is happening is that although the valve is reducing the steam volume it takes a little while for the engine to consume steam already in the system and then the pressure delivered to the engine drops and the engine slows. It does not take long before it becomes second nature to throttle off good and early and to be ready to slam it in to reverse! I am surprised about the Mainsteam comment regarding the larger rotary style valve. I recently fitted one to a 16/16 double acting twin and it seems to be as effective as I need it to be. I will test it more thoroughly when I go sailing this Sunday. This one came from Chris at 21st Century Steam and was previewed in one of the magazines a few months ago. I know he is out of them again. It does seem strange that there is not a better supply and i am also trying to get some done with fittings for 3/16 pipe for larger engines. Will let you know the results of my testing after the weekend.

[frog32]

Hi Ian.  Thank you for the info.  I have been told that the TVR1engine does use a fair amount of steam and I'm not sure of the aperture sizes in the Polly valve.  I was trawling through various web pages and I came across some plans for building a rotary valve listed on the Home Model Emgineering Machinist website so I might later on have an attempt at Emaking one but in the short term it looks like i will have to go for the Polly one.  I assume that an ordinary servo with metal gears can be used with the Polly valve? Or does it need a high torque servo?
I would be interested to hear the results of your steaming weekend.  Cheers. Roger

[kiwimodeller]

My Polly valve on the Graham single is only operated by a small servo. Not sure what it is now, it is bigger than the micro servo operating the whistle but not as big as the standard rudder servo. Certainly not metal geared and nothing special. Cheers, Ian.

[kiwimodeller]

Roger, I sailed several steam boats at the weekend and took particular note of how the throttles worked. My big paddler which has a large single cylinder slide valve engine has a home made throttle with a long tapered stainless steel needle moving in and out of a modified brass pipe fitting. This works reasonably well but is bulky and needs a servo with plenty of travel. The Picket Boat which has a 16mm x 16mm double acting twin has the rotary valve we discussed and that works very well, I could stop the engine with the throttle, hold it just above stop to idle along and then go to full throttle and back to idling along quite easily but as noted previously it takes some time for the engine revs to drop when it has been on full speed. Ideal for medium sized and larger engines. The Polly valve on the River Queen worked as well as it always does, definite and easily seen changes in engine revs and also capable of just idling along. This boat has a variable pitch prop which I can put in neutral and observe the change in revs easily. A Polly valve with fittings to take 5/32" pipe would be my choice for a TVR1A engine. I am sure it will work well and it is not as big and bulky as the rotary valve. Hope this helps. Cheers, Ian.

[frog32]

Hi Ian.
Thanks for all your help and advice and for doing the tests for me on the servo throttles.  I have taken your advice and am about to order the Polly valve.  Its too cold over here to go boating so spent my time in the workshop making a 10" disc sander so that I can sand the profiles on the bulkheads for the hull that I have ordered from Model Boats by Design.  I have purchased the Steam Cutter 'Solent'; it's 42" long with a 10" beam thought.  I thought I would get something nice and stable for my first build.
Roll on summer! 
Many thanks.  Roger.

[kiwimodeller]

I had often thought that the Solent and a TVR1A would be a good combination. My River Queen and VR1A are similar but smaller (35") and that is a nice stable set up. With the fuller hull you will need a bit of ballast but that is a good thing. Look forward to watching your build.  We are basking in sunlight at the moment and about 26 degrees. Parts of Australia and the UK are under water and we are complaining about the paddocks dying off because we have not had proper rain since Boxing Day. Good luck! Ian.