small pump

As well as model engineering I fly model planes. i have just bought an engine that runs on petrol oil mix so the pumps that are used for glow fuel cannot be used. I have to buy petrol friendly pipes etc

I want to add a little hand operated pump alongside a can of fuel to fill the plane ( yes I know I can buy them but one made by me would look better on the field)

i know that Stuart etc do castings for water pumps but I feel I can make from my own materials. What i cannot find on the internet are designs for the valves. I only have to move a cupful of fuel each time so i do not want something enormous.

I seem to recall having book with designs for a ball bearing with a spring. But springs might breakdown in petrol. In addition I do not need fuel leaking everywhere so the piston needs to be a good fit, as do the valves

Can any one direct me to a source for free designs please.

Edited By Sam Longley 1 on 09/01/2016 09:40:59

Why would springs break down in petrol? Certainly no more likely than the ball!

Fuel proof O ring on the piston, and ball valve held in place by gravity, shouldn't need a spring.

Ian S C

Sam,

I restore Lister stationary engines and some of them are fitted with a plunger pump to pump the petrol from the tank to the Carburetor, it is constructed from a brass material with a hardened steel plunger, this also has a spring to return the plunger when pressed down, the seal is a grease coated piece of string or an o ring of the right dimensions.

There are two steel or brass balls fitted one on the inlet and one on the outlet which have no springs and rely totally on the fuel pressure to keep them seated when they need to be used, my pumps stay in the same plain but depending how you use yours they may need light springs to hold them in place, stainless would be best. I hope this helps you.

Martin P

I know you want to make your own but- Buy a mechanical fuel pump, lever operated, as used on older cars, they are quite cheap. Then make a nice box for it with a handle on the lever.

This is a small fuel pump, I'll see if I can dig out my sketch where I redesigned it to be more scale like. The lift up plunger is just above

Or the water coolant pump off the same engine would work with a bit of Tygon fuel line

Though I would just fill a squeze refueling bottle with a funnel from the petrol can and use the refueling bottle if you only need small amounts

Edited By JasonB on 09/01/2016 11:36:25

Jason,

Miniature version of my Lister pumps.

Martin P

One thing about valves that helps instead of a spring is something to limit the lift of the ball so that it gets back on its seat more easily not having gone off to the end of the pipe. Another angle might be like the large catering coffee pots that are sealed and the pump pressurises the air in the container to push the contents out.

Sam, I fly r/c helis including a gasser and while I use petrol tubing on the bird itself I use an 'ordinary' cheap rotary hand pump to fuel it with silicone tuibiong. the same pump gets used for the glow birds and lasts a few seasons.

While i applaud the idea of a diy build some things aren't worth it. If you want to go ahead then it might be worth looking at the principles of medical peristaltic pumps. Or just use gravity.

Rubber tube and bulb as used on outboard engines.

I use an old lever grease gun head as a small pump.

I know a number of people have suggested buying something & i do have the rotary pump suggested above for my nitro planes. I also use a hand pump on one of my yachts inboard engine. JasonB's little pump is brilliant & i could cut some tufnol gears to a crank to get it pumping fast

It just seems like a nice little project to try & a chance to extend my skills. I think I will give it a go just for the " non flying" days

Edited By Sam Longley 1 on 13/01/2016 19:20:44

Edited By Sam Longley 1 on 13/01/2016 19:21:41

Petrol dissolves oil and rapidly evaporates, leaving clean, bright, vulnerable steel. Steel springs in petrol uses always go rusty as a result.

Would a bronze spring suit your needs?

Bronze springs are certainly OK for gasoline/petrol but stainless are more commonplace and easier to find. There are MILLIONS of stainless steel springs immersed in gasoline/petrol right at this moment all over the world. In gasoline pumps at filling stations, in fuel lines to hold filters in place, in carburetors and fuel injectors....

No need to look for exotic stuff - brass bronze stainless are all OK for gasoline/petrol service. If you have any rubber parts in your system though make sure they are rated for gasoline/petrol service.

Re pump speed - for ball lift pumps the balls need some time to lift and fall between strokes, so very high speeds may affect their operation. Just mentioning it because you had mentioned speeding the pump up with gearing. Might work, might not. I'd vote for a simple crank or lever driving a displacement plunger and not bother with gearing it. One further suggestion would be to plan easy tool and finger access to the caps over the balls and springs for easy service should some crud get into it. Also, a fine filter of bronze mesh on the inlet would be cheap insurance to help keep crud out of your pump. JD