I am restoring several single barrel pumps at the moment. If these pumps have no check valves in the pump assembly then how did our grandfathers actually pump up the tires? Each stroke up and down inflates and deflates. They sell separate check valves today which go between pump hose end and the valve stem, BUT did they have these then? Is there a trick other than removing the weight of the car with a Jack?
There is usually a check valve built into the hose connection at the bottom of the barrel.This may be a very small ball bearing and is easily lost when cleaning up an old pump.
Wow I didn't think about needing a check valve. Does anyone know what it should look like on the standard single barrel brass pump? Is it just a ball and then the hose fitted over the top?
I know the double barrel pumps have a check valve. I wasn't aware the single barrel pumps did.
I have seen them with the little ball built into hose connection and also just loose in the base housing.
Is there something holding the ball in place? Does anyone have a drawing? I have obtained three sizes of steel balls (bike wheel bearings) for this purpose but need to find out proper placement in order to get them working correctly. Is there a retaining wire or washer? Is there a place at the bottom of the metal hose connector? Is the ball simply in the hose itself and is sucked down on the up-draw of the plunger?
Surely the tyre valve itself stops air escaping on the upstroke of the pump. The pump itself is 'recharged' with air on the upstroke by air finding its way past the leather cup-shaped piston. Because of the shape of the leather, when the handle is depressed and the piston starts on its downward stroke, the leather is pressed outwards to form a seal with the barrel of the pump. In that way the leather piston is a brilliant design because it is also its own valve.
Dane, that does not work. In order to inflate the tube the valve must be depressed so the valve is open and can blow back.
Tire pumps need check valves. There is most likely no one, correct answer for where exactly the check valve goes and how it's retained, (or not retained). I'm sure the design varies between manufacturers. However, it is usually in the base of the pump.
I know the tire valve needs to be depressed. I have a pump out in the barn that we used regularly on wagon tires. The tip was missing the little gizmo that pushed down the valve when the tip was screwed onto the stem. We managed to pump air into the tires but MAN what a chore. I keep the old pump around to remind me to be thankful for my modern compressor.
I have added some photos to my Photo Bucket of the Ford check valve. They may be a bit out of order but if you click on them I have added a title:
Perhaps U.S.tyres (or even tires) are built differently to the ones that I have used for 50 plus years, but following from my previous description, as the pressure in the cylinder of the pump builds up to exceed the pressure already in the tyre, the pump pressure forces the tyre valve open to admit that air.
I'd venture to guess that any piston pump, be it for air or for liquid, needs two check valves of some sort, one on the inlet and one on the outlet. I'm not sure about T air pumps, but others that I have worked on had a cup shaped leather washer on the piston. On the up stroke, air comes past the leather but on the down stroke it pushes the leather against the cylinder wall and seals, just as Dane said above. Then there needs to be a second check valve on the outlet side to keep the pressure in the tire from just pushing the piston back up. Again, I'm not familiar with T pumps, but every other one I've ever seen held the schraeder valve open when it was attached to the tire. I've never tried to push air past a closed schraeder valve. Maybe it could be done, but I think holding it open and having a built in check valve in the pump is a better idea and is certainly the way the ones I have seen work.
Thanks Mark. It all makes sense now--the ball falls in the hole to keep the "tire air" from escaping, and the spring keeps the ball from blocking the flow from the pump to the tire when the pump handle is depressed. The "pump air" forces down the Schrader valve in the tube. Correct?
Thanks for the photos Mark. I have a pump that looks like yours but the outlet end that came with it has no "gizmo" to depress the valve in the tube. Is this the correct part?
Thank you Mark. I believe that answered the question clearly. The ball also looks to be either the 1/8 size Bering or the .177 caliber BB gun BB. I will try this with my 4 pumps and check the results..
I also noticed that the "Schrader" connectors on the tire end of the tubes mostly are 'missing' the valve depression stem to open the tire valve.. They have the pictured hole as above but no 'gizmo'. Does anyone have these screw on ends (original) that do have the depression stem in them? If not then the theory that the pumped pressure itself opens the valve on the tire must have some validity. Or the depression stems were so badly mounted that they tended to fall out and get lost (unlikely).
I just checked the size of the ball and spring. The ball is .245 dia the spring is .175 dia with a free length of 3/8". I do not have the original hose end for the the stem.
There may never have been a piece in that fitting to open the valve and might have relied on the air pressure from the pump to do the job. The tube valve is a one way valve and the compressed air may have been enough to overcome the spring pressure and let air into the tube. Just guessing on that. The tube valve would then act as a 2ed check valve.