Axle Driven Feed Pump for the Beginner's Locomotive
Axle Driven Feed Pump for the Beginner's Locomotive
An 0-4-0 Switcher of Simple Design in 3/4 inch Scale
Victoria Society of Model Engineers
The Miniature Locomotive, March-April 1954
This item had best be made and fitted now before we get involved in boiler work. You will notice the pump is not very large being only 3/8 inch x 3/8 inch but the engine is small and with 3 inch wheels it will pump as much water to the mile as a 5 inch drivered Atlantic with a 5/8 inch stroke pump which pretty well evens things up. While a big pump is handy to get the water up quick you can overdo it when the boiler is small, it may take a chill.
The pump shown is fabricated from round and square brass and I doubt if any time would be saved if a casting were used.
The barrel is made from 1/2 inch diameter stock and is 1-3/8 inch over all. Chuck, turn down 3/16 inch of it to 7/16 inch diameter. Reverse and screw cut a 32 thread per inch for 9/16 inch on it. Center, drill 5/16 inch, open out to 23/64 inch and team 3/8 inch. If no reamer, bore as smooth as possible until a bit of 3/8 inch bronze or stainless steel will just slide in. The penalty for a sloppy fit is frequent re-packing of the gland. While the lathe is set up for 32 threads we may as well make the gland and oval mounting flange. The flange is cut from 1/8 inch brass plate (steel would do) 1-1/4 inch by 7/8 inch. In the center put a punch mark and set same running reasonably true. Center, drill 15/32 inch and screw cut to fit barrel.
The gland can be made from 9/16 inch hex brass, but if you're like me I wouldn't find a bit of 9/16 inch hex in my stock pile so I'd just turn it from 5/8 inch round. Divide into six parts and file the hex. If your lathe has no dividing marks on it, by all means divide the front face of the back gear into six and center punch.
Then fit up a pointer to line up with these punch marks. This is extremely useful for making hexs. The gland is only 3/8 inch long and the hex left and the outer 1/4 inch turned off, which looks much neater. Drill 3/8 inch for 7/16 inch in. Open out to 15/32 inch, 5/16 inch deep and screw to fit the barrel. Part off.
The valve box is made from 5/8 inch square brass with an overall length of 1-1/4 inch. Turn down 1/8 inch of it to 1/4 inch diameter to spigot into the delivery valve box. Center, drill 7/64 inch for 7/8 inch depth and ream 1/8 inch. Take the merest scrape of a facing cut off this spigot to insure an even true knife edge seat for the ball. Reverse, center, drill 3/8 inch with a 1/4 inch drill (which will meet the 7/64 inch hole). Take a facing cut off the end to form a true joint surface for the suction valve seat. Turn the end to 5/8 inch round for 1/2 inch long. In the middle of one of the flats drill a 7/16 inch hole to take the barrel. This can be a drill press job and the hole 1/2 inch deep.
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