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Boiler Feed Pump Stroke

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Alan Worland06/09/2011 19:39:06
247 forum posts
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I am about to start an eccentric for a feed pump. The pump is something I have already (I think it might be a Bassette Lowke model) which is .250 bore and according to my calculations will need to have a stroke of .125 per engine rev.
My question is, is the pump likely to still work with this small stroke? or would it be better to run it through a gear train and run the pump slower but with a longer stroke? and/or discharge any excess back to the water tank
The pump contains 2 stailess balls of .125 dia and .187 dia
 
Alan
JasonB06/09/2011 19:43:42
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Traction engine would usually have a bypass to return water to the tank when not needed, just shut the bypass when you need to add water.
 
By way of comparison the 1" Minnie also has a 0.25 bore pump with 5/16" stroke.
 
J
Alan Worland06/09/2011 20:26:58
247 forum posts
21 photos
Thanks Jason, seems like I should have a longer stroke than 0.125 then. Does the Minnie pump work at crankshaft revs? I am planning for the engine to run fairly slowly (cause I like it like that!) but wouldn't want the intermittent load of the pump stroke to affect the smooth runnng, so I am now thinking of gearing (with a longer pump stroke) to spread the load over more engine revolutions.
Does any of that make sense?
 
Alan
JasonB06/09/2011 20:34:55
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Straight off the crank like the majority of traction engines though a few were geared down. Not including those that only had injectors and no pump.
 
You say you have calculated that it needs 0.125" stroke per rev, is that what you think will need replacing per rev due to the amount of steam used. If so you need to allow for when the engine is not running but the blower is on and using steam or if opening the drain cocks, etc. if it cannot replace more than it will use per rev once you run the engine to use the pump you will always be in deficite.
 
Jason

Edited By JasonB on 06/09/2011 20:36:25

Alan Worland06/09/2011 21:10:13
247 forum posts
21 photos
I must say that the engine is not a traction engine, but my Stuart No 4 that I recently finished!
The water consumption as suggested by Stuart is 19.8 lbs per hour when running at 1500 rpm on 75 lbs of steam - which comes out at the above and sounds like a hard working engine.
The plan was to fire the boiler with gas (so no blower) and use the engine to run a small generator for lights.
 
Alan
 

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