Southworth Engines Boiler Feed Pump

[NickG]

I know!  There's not a great deal left to do on the Poppin and electric loco, just a matter of grabbing the bull by the horns really. I've then got a list on Word that I keep chopping and changing. If I go the Mabel route I'll be asking lots of advice and for a loan of your formers if possible! Our new boiler inspector pretty much condemned the old mabel boiler and probably rightly so, don't think it's worth messing about with. The sweet pea is tempting though as it's a relatively simple engine - there's a lot of parts to make, but probably the most difficult part for a lot of people (boiler) is sat there in a box all done.

I've got a project planned for some time in the future that would use a Sweet pea boiler

sounds interesting!

Nick

[sbwhart]

No Problem with the Mabel formers I can get them to you via the internal post to you if you want them.

Stew

[madjackghengis]

Really great job on the feed pump, Stew, very fine work, and it looks very nice with the castings all in all.  Look forward to seeing it pumping into a boiler, the real test in the end.  I am going to have to go through this log again, and get a better look at that valving, I wished I could've been there to watch with you.    Cheers, Jack

[doubletop]

I’ve just finished making one of these pumps and although this is an old thread I thought we may as well keep all the information together..



It looks like its going to do what I need it to, and be able to feed a boiler at 90psi. Here it is running on 20psi air pressure and giving 60-70 psi of water pressure. 0.5” piston and 0.25” ram gives a theoretical pressure gain of 4. With losses I’m getting a gain of just over 3 so if I run it at 30psi it looks like it will to the job

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Stu pointed out some errors on the drawings and I have some more to share. He pointed out the error with part 6 and the bore for the 0 ring was too deep. Its also the wrong diameter. The O rings supplied are 0.25 x 0.375” with 0.625” section. So the easy way is to just bore the hole is a 3/8” slot drill. I found making them 0.060” deep was sufficient that it didn’t cause the piston to bind. This applies to parts 6 and 22

The castings are very soft and I blew my valve chest off the cylinder trying to run at 30psi. drilling the holes for the 10ba studs only 0.075 deep is just not enough. However, if the holes for the cylinder ends are drilled at PCD of 0.065” then the holes for the ends caps and the valve chest can be as deep as you like (within reason) as they don’t get in each others way. I did mine 0.35” deep. (Spacing to the valve chest is 0.6” and a PCD of 0.650 gives a spacing of 0.403” which mean 0.1” between the hole centers, just enough for 10ba)

This is where the dimensions on part 5 are wrong



A 0.5” spacing isn’t a PCD of 0.650, radius of 0.325”. The 0.5” spacing gives a PCD of 0.707” and the holes will clash with the valve chest holes as they are only 0.05” apart.

 I also did a PowerPoint to show how it works, attached below

Hope that helps somebody

Pete

[tom osselton]

Stew


nice work

what with your pussy faux pas now we have "fag" paper  what will our friends across the pond think "gay paper" 

So dandruff would be fairy dust then! !   

[OldMetaller]

Hi guys, I'm really glad this old thread has been reopened, as I bought the castings for this feed pump from the new owner of Southworth Engines a year or so ago, and scared myself to death!  Much too complicated for a newbie like me, I thought, but now with this thread, I may just steel myself and have a go at it!

Thanks for such an informative build thread!

Regards,

John.

[Stilldrillin]

Hi guys, I'm really glad this old thread has been reopened, as I bought the castings for this feed pump from the new owner of Southworth Engines a year or so ago, and scared myself to death!  Much too complicated for a newbie like me, I thought, but now with this thread, I may just steel myself and have a go at it!

Thanks for such an informative build thread!

Regards,

John.

Hello, Young Man! 

Don't forget, we need a build log. With pictures! 

 

David D

[doubletop]

John

One point I'm going to make about the approach Stew took to the pump. And this isn't a criticism as there are many ways to skin a cat.

I'm not sure why he drilled the ports this way



When they could have easily been done at this point of the machining process.



A 3mm drill to start, then a 7/32" slot drill, tap the 1/4" x40 thread and finish with a 1/8" reamer and then guaranteed nice sharp and square faces for the valves.

Good luck with the build and let us know how you get on. As I found looking at the kit of parts doesn't get the job done. Everything looks quite small at first but getting stuck in and cutting metal you soon get used to working on this small scale

Pete

[sbwhart]

I'm not sure either 

 

Stew

[Steam Geek]

I am in the process of ordering the castings to make up a feed pump for my Achilles, tired of messing around with injectors and want something reliable.

Also a test of how accurate my machining is

[doubletop]

I had this running  fine on air but when the input pressure was raised it would just stop and vent through to the exhaust . That implied to me that one of the two valves were lifting. My first thought was the slide valve as it doesn't have any form of crosshead and the only thing keeping the valve rod in line is the thickness of the valve chest wall. On the bigger version the valve rod extends through the top of the valve chest so I thought I'd give modifying it go. Here's the list of changes I made to the various parts.

#18 Slide Valve nut - make it 1/8" thick and drill 1.6mm rather than tap 10ba. on the top edge drill and tap 10ba for a grub screw to hold the valve rod

#15 Valve Rod -  make 2.5" and 1.8" from one end file a small flat for the grub screw

#17 Slide valve - make 0.1" lateral slot now 0.13"

#2 Valve Chest - repeat valve gland on top face. Remember to offset to the correct side to match the gland on the lower face.

#4,4A Cover top/bottom - make two items 4A note there is a drawing error here the No50 hole isn't on the centre line its offset to match the offset on the valve chest.

You'll need another 1/16" x 3/16" O ring. my kit came with two.

The trickiest bit was the 10ba grub screw as its only 0.1” long.. Rather than trying to put a slot in a 10ba rod. I turned down the head of a countersunk 10ba screw and the threaded the end. It then comes with a ready-made slot.





Here’s the valve chest  assembled with the extended valve rod coming out the top of the valve chest.



As would be expected the slide valve is kept well in line. However on re-assembly and re-test the problem of the venting wasn’t resolved. So it had to be a problem with the shuttle valve. Checking it was quite a loose fit and able to lift some way off the port face. If you use the 1/64” hallite gasket as suggested in the plans then the lift is an additional 15thou. Although in an earlier post I’d suggested using and anaerobic gasket I found you couldn’t guarantee any gasket not oozing in to the valve chest under the shuttle valve. And there’s no way to check.

If you look at the attached .pdf file you can see the clearance for the shuttle valve to lift is is 32thou I’d suggest both should be no more than 10 thou. That what I’ve made mine to be. The 0.090” dimension on part 14 should be 0.115”. My pump now behaves itself and I’ve fitted to my loco.



And it runs this it it pumping water slowly against 90psi boiler pressure

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I had it at the track today and it was ticking away happily to itself all afternoon. And was adequately pumping water when I upped the pace

Hope that helps somebody

Pete

[NickG]

Thats's great Pete, glad it's working well. Well done.

[alanfrost]

I'm gearing up to build the pump this winter during the long Vermont winter The castings and appropriate diameters of stainless steel rod are sitting on the bench and I have spent hours reviewing the postings in this thread so many thanks to all of the contributors. Does anyone have photographs or input on machining the butterfly valves?

[alanfrost]

I'm answering my own question here as I decided to make the butterfly valves. 

Turned the 0.125 dia wing section stem to a length of 0.14 then formed the undercut positioning the parting tool against the shoulder. 
Turned the 45deg valve seat and then cut off last inch of stock which was reversed in chuck, faced and center drilled.
The 0.1 spring mount was then turned to facilitate holding the valve in the rotary table chuck to machine the valve wings after which the waste was cut of and the spring locator stub was filed to length.
 

[alanfrost]

forming undercut

[alanfrost]

Turning valve face

[alanfrost]

Turning spring locator

[alanfrost]

milling valve wings

[alanfrost]

finished valves

[doubletop]

Alan

You made a nice job of those valves. I had a few failed attempts, but that was me trying to be smart and grind the 45deg angles with a diamond disc on my tool an cutter grinder. It seemed like a good idea at the time as I've always had trouble seating home made safety valves. I did it your way in the end and they work fine. I think using a 7/32" slot drill in one operation to cut the valve seats and the tapping size for the 1/4 x 40 threads contributed to the success.
 
Pete

[alanfrost]

Thanks for the compliment. I suspect the degree of surface finish on a valve face my be dependent on the pressure and viscosity of the fluid being contained as well as the dimensions of the transfer passage. You would certainly grind the valve faces for an internal combustion engine where pressures and temperatures are high but the viscosity of the intake air and exhaust gases are low. The water pump valves I made did hold air pressure but in practice any backflow on the intake side probably offers more resistance to flow than the output pressure needed to feed the boiler.     

[alanfrost]

My pump is up and running but I have only run it on air so far. I made liberal changes to thread sizes from those in the design substituting #2-56 for many of the 10 BA locations. Getting BA taps and dies is not easy in the USA with many sizes not being available on this side of the pond. Fortunately I inherited a good collection of BA taps and dies from my father but am still missing some from my collection.   Getting the exhaust valve timing adjusted is certainly a labor of love and start up was initially erratic but I traced that to having been too energetic with polishing the shuttle valve spindle and creating too much clearance for it to hold pressure and move the valve body.  I also had problems with the valves seating and made some changes to the height of the valve body to making it the same thickness as the valve chest with the gasket material providing the working clearance.  As other have commented the exhaust valves floating cross head seemed a trifle sloppy and I extended the 1/16 inch rod through the top of the valve chest to provide better control of the cross head's movement, Thanks to Bob Potter for providing two 1/16 ID O rings with the casting kit.    

I increased the thickness of  the valve chest top and bottom cover to better allow even compression of the gaskets in those locations.  I also modified the cross head design to accommodate a #2-56 cap screw making it stand proud of the valve chest face and used a thicker back plate with a slot milled to provide a track for the cap screw head to run in. 

[Steam Geek]

When you are machining the castings what tollerances are you aiming to achieve ? 2 thou ?

[alanfrost]

Posted video of pump working on air on  YouTube.  Use "alan frost steam boiler pump" as search string to locate.

[dsquire]

Alan

Here is the link to your video. This will save the members from having to search for it. Hope you don't mind me putting it in here.

    [ Invalid YouTube link ]

Cheers 

Don