allchin water pump

[michael birdParticipant @michaelbird72946]

Hi all,

 

The “how to” book states that the passage between the barrel and the valve chamber is drawn as 1/8″ dia. but should be 5/32″ dia. and must be concentric to (or should it be with) the barrel. This dia. is actually shown as 5/32 on my set of drawings.

 

The drawing of the plunger shows the small dia. on the end as 1/8″dia. (help)  If it should be 1/8″ dia. why the need for concentricity?  If it should be 5/32″ and a sliding fit on the small bore, surely there will be a pressure build up between this and the O ring on the plunger…. or am I being silly ?

 

Yours, Bob 

[michael birdParticipant @michaelbird72946]

[JasonBModerator @jasonb]

The drawing on page 190 “B” seems to show the spigot on the end of the plunger smaller than the 5/32 hole but like you say can’t see the need for perfect concentricity?

 

You have to remember that a lot of the text is straight from the original build articles and the drawings have likely been altered since hence your drawing showing 5/32 but the text probably refered to a drawing printed in the mag or an earlier revision of the main drawings.

 

Jason

[michael birdParticipant @michaelbird72946]

Hi Jason,

 

Thanks for your comments.  I will go ahead and make it with a 1/8″ dia. spigot on the plunger and see what happens, but still wonder if it’s an 1/8″ dia what purpose does it serve?  By the way, do you know of a forum that is dedicated to traction engine building where I could perchance chat with somebody who is also building an Allchin or similar.

Thanks again, Bob

[JasonBModerator @jasonb]

I do indeed

 

Pop into Traction Talk Forum, they have a separate section for models – general discussions, Members models and drawing errors. The full size stuff is not bad either.

 

There are a few alchin owners both 1 1/2″ and bigger as well as some who have progressed onto bigger things.

 

http://www.tractiontalkforum.com/

 

You just need to register, if you find it useful then a small contribution to running costs will allow you to access the archive and see all of the photos in posts depending on how they are hosted. My 2″ Fowler build is on there.

 

Another less active site is [url=http://groups.yahoo.com/group/scalemodeltractionengines/]Yahoo group[/url]

 

Jason

 

BTW the reason for the pin is to help stop airlocks, without it a bubble could form in the 5/32 passage and the gas would just compress with each stroke of the ram and not be expelled. The spigot is usually a bit smaller than the bore, its just the emphasis on concentricity that I can really see the need for.

Edited By JasonB on 26/03/2010 15:39:31

Edited By JasonB on 26/03/2010 15:41:09

[Dave WakefieldParticipant @davewakefield]

hi can any body tell me what cutter to buy to do the the gears for the allchin 1.5 inch. i need to know the module and no for the 15 teeth pinion. many thanks dave.

[JasonBModerator @jasonb]

Module won't do you much good as they are 16DP gears. and for 15T you will want a No7 cutter

Check what the pressure angle is, if you already have the other gears then you will need to match the PA either 14.5 or 20 degrees.

J

[Dave WakefieldParticipant @davewakefield]

Thanks Jason I've got the cutter and will be cutting the gear soon. The reason for making this gear is that i damaged the teeth when trying to bore out the centre, due to it being under size from the supplier, the hole size is to small for the key way to be cut in the gear change centre. Drawings are wong the centre of the gear is to weak to be bored out to the drawn size. Thanks once again, all the best its good to see that someone will give so much free help and advice.

[Paul LousickParticipant @paullousick59116]

Hi,

The drawings for the 6" Ruston Proctor traction engine which I am building does not have a piston water pump, only an injector and a separate steam operated Moore pump. (4" version comes with a piston pump).

I have a casting for an Alchin traction engine pump which is about the right size but I have a question about the piston design.

What is the reason for the small spigot at the end of the piston ?

Paul.

[Anonymous]

May be intended to reduce the dead water space? However, I suspect all it will do is restrict the water flow as the piston advances. Personally I think it's a waste of space itself.

Andrew

[Paul LousickParticipant @paullousick59116]

Thanks Andrew,

That was also my reasoning for the feature. I could not see any logical reason for it. All of the pump designs that I have seen do not have a spigot on the end of the piston and will make mine with a flat end unless someone can give me a good reason to keep it.

Paul.

[JasonBModerator @jasonb]

Suppose to be an "anti airlock pin" which you see quite often on these sort of pumps. Not sure how and if they work.

The Minnie design has one but not the Fowler.

J

[Anonymous]

Posted by JasonB on 17/04/2016 13:13:44:

Suppose to be an "anti airlock pin" which you see quite often on these sort of pumps.

Quite so, although not present on the full size Burrell water pump that I've based my re-designed water pump on. The full size pump has a 'PET' cock into the dead space, which presumably can be loosened to let the air out if the pump won't start.

Andrew

[John FieldingParticipant @johnfielding34086]

The "anti-airlock pin" was a fad started by LBSC back in the early days. The theory goes that when you compress water the entrained air gets squeezed out and causes an airlock. Not a problem on full size pumps but apparently was with smaller plunger pumps used on model locos etc. Never been able to fathom the physics of the method!

[Anonymous]

Posted by John Fielding on 17/04/2016 13:29:54:

The "anti-airlock pin" was a fad started by LBSC back in the early days. The theory goes that when you compress water the entrained air gets squeezed out and causes an airlock. Not a problem on full size pumps…

That's odd? When I was re-designing my Burrell water pump there was quite an extensive discussion of water pumps on the TractionTalk forum, including one professional pump designer. At least some of the full size engines and portables discussed had PET cocks to over come airlocks and help the pump start. So, in full size at least, that rather pre-dates LBSC.

Andrew

[Paul LousickParticipant @paullousick59116]

Thank you gentlemen for the advice about pumps. I think that I will make the end of the piston flat and add a small pet cock to the top of the cover plate on the pump.

There is one on the full size Fowler which I drive for purging air from the system which works OK. The problem being that it sprayed water into the driving cabin over the operator so piped it to discharge to the side of the engine. It is used for not only bleeding air but to confirm if the pump is actually working and if there is still water in the tender tank. (Also good for spraying onlookers standing on the side of the road with water.)

Paul.

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