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Post by Shawki Shlemon on Sept 20, 2006 10:27:12 GMT
Hi All I am building a Dukedog and I am sure there are many out there doing the same .This engine is a complicated one, sharing ideas seems to me to be of benefit to all of us .I am making some changes to my engine and I would like to share the first one with you. I like axle pumps on my engines. Mr K. Wilson did not provide for an axle pump on the engine . It is not possible to drive it from driving axle as is cranked and has 4 eccentrics for valve gear. The rear axle is too close to boiler back head . So after some thinking I decided to increase the distance between the axles from 9" to 10" to facilitate the modification . I mounted two 5/16" dia pumps on rear beam driven from rear axle .( see picture ) .I will blend the change in three ways (1) reduce boiler protrusion in the cab (2) move the cab slightly forward and (3) lengthen the cab . This way the change will not be visible to ordinary people . I invite others to make remarks on this or any other issue .
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Post by greasemonkey on Sept 20, 2006 12:15:56 GMT
Hi Shawki When I wanted to add a pump to an engine I put it on the middle tender axle, worked a treat. Your going to have fun shoe horning it in amongst the valve gear.
Andy
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gwrfan
Part of the e-furniture
Posts: 456
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Post by gwrfan on Sept 20, 2006 20:27:04 GMT
Hi Andy, A pump on the tender axle is fine - unless, like my Dukedog-to-be, you have built a tender with a Well tank! Regards from GWR Land.
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Post by greasemonkey on Sept 20, 2006 21:24:48 GMT
Hi Geoff You cant win them all!
Andy
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Post by Shawki Shlemon on Sept 22, 2006 9:37:35 GMT
Hi First of all the pumps are not driven by driving axle to interfere with valve gear , it is driven by coupling or rear axle .Secondly I have nothing against pumps on tender , just it is one of those things that one feels wants to do , after all it is a hobby . I like challenges.
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Post by GeorgeRay on Sept 22, 2006 20:56:21 GMT
Shawki Could you not have fitted crosshead pumps in place of the GWR vacuum pumps or is there not room. You might thenhave been able to keep the original wheel base.
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Post by Shawki Shlemon on Sept 24, 2006 8:59:48 GMT
Hi George That is exactly what I did and there is still room for vacuum pump but the axle is too close to the boiler to have eccentrics to drive the pumps.The axle had to be moved back a bit .The engine will be slightly longer, not noticeable but heavier and the weight in the wright place, hopefully will improve traction .
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Post by spurley on Sept 24, 2006 12:01:33 GMT
I think George was suggesting that the pumps be driven by the crosshead(s), hence the name crosshead pumps! So no need for any extra eccentrics.
However, I'm sure you know what you're doing and I sympathise knowing from experience how much room there is/isn't available between the frames of this engine. I have worked on the full sized survivor, 9017, at the Bluebell over the years. Cleaning, oiling and maintenance.
Cheers
Brian
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Post by Shawki Shlemon on Sept 25, 2006 10:47:14 GMT
Hi I missed the word crossheads for whatever reason but it would be hard to drive pumps at the back of the engine from crossheads in the front passing the boiler .I think (hope) the engine will not look bad and the performance will be the same or better .
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Post by steamjohn248 on Sept 25, 2006 20:19:48 GMT
In a world where reliable, sensible injectors are freely available 'off the shelf', why do people still insist on mechanical pumps. They went out in the real railway decades ago. OK on the real railway if one of your two injectors won't perform while you are prepping the egine, you fail the engine and you dont go off shed. In the world of models is this such a big deal? Having said that, all thengines we build have an emergency hand feed pump to keep you out of trouble if BOTH injectors fail half way round the circuit. But I've never had to use one. Most of the MODEL engines I've been invited to drive ( "with injectors that don't work so you'll have to use the axle pump"), have proved to have injectors that work perfectly if you treat em right. (I'm now going to have both injectors fail on me the next time out to cries of "told you so"). Yours waiting to be proved wrong. Steamjohn
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dscott
Elder Statesman
Posts: 2,438
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Post by dscott on Sept 26, 2006 7:13:31 GMT
Pumps, On my drawing of the Duke in its original condition, the water pump is opposite the vacuum pump, the same as on the Armstrong class. on mine i am using steam brakes, the twin vacuum cylinders cause lots of problems in their fitting. For weight go for the specified thickness of tubes, wow what a price these must be these days!!! Lovely to see your photos, the rough paintwork is so lifelike, its taken 20 years to get my Gemma looking industrial. David Scott.
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Post by Shawki Shlemon on Sept 27, 2006 11:03:09 GMT
Hi All I am very pleased to get comments of all kinds , after all this is what it is all about so everybody benefits from remarks. However I generally (not always) fit an injector on my engines for obvious reasons, but I like axle pumps as they work with clean , dirty , cold and hot water, and water delivery is controlled by by-pass valve .As for brakes on models , again I generally fit brakes as designed but adjust them to be inoperative because I believe that the engine pulls the train and the train should stop the engine , so the operative brakes are under my seat and on passenger carriages.I must note here that if brakes are inoperative on the engine ,all visible parts should be complete to make the engine look wright .
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Post by chris vine on Sept 27, 2006 20:22:44 GMT
Hi Shawki,
How do you find injectors in your hot weather?
We had an unusually hot summer here in Scotland and on the days when the mercury gets about about 25 celsius I find that the injectors are a bit temperamental at the full boiler working pressure, especially if the safety valves are blowing off, another 5psi I guess.
Chris.
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Post by Shawki Shlemon on Sept 28, 2006 9:48:55 GMT
Hi Chris My experience over the years is as follows - 1) Injectors made by different firms or individuals behave completely in different ways . some operate well at lower pressures while others operate better at higher pressures , but all of them have a range of operation . 2) They seem to respond to the temperature of the water rather than the atmosphere . The trick seems to be to keep the water cold in the tender . 3) I found that they are hopeless in tank engines as is difficult to keep the water cold in the tanks. 4) As you know water must be clean and no air should get in the system . 5) I have used some locally made here and some from UK (late Spinks) and found all to be satisfactory but as you gathered that I mainly use axle pumps except when I am stuck in traffic or in steaming bay .
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Post by chris vine on Sept 28, 2006 16:01:34 GMT
Hi Shawki,
Yes I had trouble with a tank engine and injectors. Luckily there was a tank under the coal bunker which stays cool so I fed the injector from there.
The fantastic thing about injectors is that M. Giffard ever invented them at all as they seem a bit magic (even though more volume of steam is taken out of the boiler than volume of water put in). Apparently he kept badgering the belgian state railway to lend him a locomotive to try out/demonstrate his new device. They told him to "Bu.....r off" (in Flemish I guess) because it was clearly a crack pot idea and could never work etc. etc..
Luckily he was persistant because eventually they lent him an engine just to show that it wouldn't work and to shut him up. Of course it worked perfectly and anyway that is how I was told the story..... (any other versions??)
I was also told that his prototype injector worked first time which I find even more extraordinary...
Chris.
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Post by Shawki Shlemon on Sept 29, 2006 10:16:38 GMT
Hi Chris Thanks for the history information, however we can't get something for nothing ,we need energy to pump water into the boiler , it may be steam or mechanical .My doctor once told me there is no free lunch .
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Post by chris vine on Sept 29, 2006 12:52:28 GMT
Hi shawki,
I know it isn't really magic and I understand the physics/thermodynamics of the injector, I am just amazed that M. Giffard got there when he did!
Chris.
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Post by Shawki Shlemon on Oct 1, 2006 9:17:18 GMT
Hi Chris I believe that on average we only use 10% of our brain, every now and then somebody uses more and guess what , they do something smart.Then we all reap the rewards .Thank God for that.
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Post by chris vine on Oct 1, 2006 17:28:20 GMT
Hi Shawki,
You are quite right, the funny time is when someone doesn't use even 1% of their brain, tries something that sounds completely stupid and it works!!
Chris.
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Post by Shawki Shlemon on Feb 15, 2007 9:05:54 GMT
Hi all It has been a while since I started this thread and now I am back to report on progress. Finished cylinders and valve gear , installed all parts and discovered the valve travel is insufficient. After investigating the problem I discovered that Mr Wilson has made a gross error . The offset in eccentric sheaves is 5/16" giving a total movement of 5/8" . The valve travel as designed is 5/8" (2x port+ lap). This is OK for Launch type expansion link but not for loco type link. I am reporting this for those people who have not yet made crank axle, valve gear,and cylinders to consider modification to increase travel and/or reduce size of valves and ports . Regrettably too late for me , I had to find another solution. First I ensured to get maximum travel possible by increasing the travel in the reverser and reducing the length of the DIE nut to 3/8". Secondly I centered the valves and measured the extra movement required to open the valves on time ( it was 0.050" ). Thirdly I removed the valves and reduced the length by machining 0.050" from both front and back. This action reduced lap from 0.125" to 0.075"therefore reducing the time for steam expansion a little . I would not do this if I did not have to. I completed timing locked the sheaves and tested the engine on air , all OK . The photograph shows the cylinder and valve gear installation.
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