What to use for packing an air pump

[Reno Speedster]

I am rebuilding a two tube air pump to go in my 23. I don’t plan to use it, but I would like it to work. I need to pack the top of the small tube. Has anyone done this and if yes’s, what did you use?

[Allan]

Is there supposed to be any packing there? I am not familiar with two tube pumps, but there is no packing on a single tube pump.

Allan from down under.

[Reno Speedster]

Yeah, on the two tube pump the big tube pushes air into the small tube on the down stroke and the small tube pushes air into the tire on the upstroke. You need packing around the rod at the top of the small tube or all the air leaks out.

[Allan]

Morgan, have I got it right? The large tube plunger must have a standard leather cup bucket which is pushed against the sidewall under compression so it pushes air into the small tube. That displaced air has to bypass another cupped leather bucket on the small tube shaft, meaning that washer is installed other way round to the first one. This would allow the air to pass into the smaller tube under some compression when the handle is right down. This would mean the air in the small tube must be sealed in at the top of the tube prior to the upstroke. On the upstroke the leather cup at the bottom of the small tube forces air into the tyre. Might the seal you are enquiring about be a leather seal with a flange around the shaft, sort of the reverse of the other seals which seal on the tubes?

Allan from down under.

[George Mills]

See we are not getting too many replies and advices...

Last double barrel that I rebuilt I used the teflon valve stem packing string like an old school plumber would use on a water valve on the small barrel seal. Took a couple of tries as it would try to extrude up the plunger stem above the nut...I would just cut the visual 'hernia' off flush and add more under the cap. It eventually stopped extruding.

I'm sure there is a better way. I 'think' the extrusion issue came about that the ID of the bonnet nut and the OD of the stem shaft leave a little too much gap...a brass washer closing most of that gap 'might' have made it a once and done proposition.

Good Luck,

Please post what you do and the results...I'm planning on doing another complete tool kit for a 19-23 this next winter, and if a better way exists...I'm all ears.

[jiminbartow]

If you go to Snyder’s and do a search for pumps, they have graphite packing. They also have rebuild kits for tire pumps.

IMG_8604.jpeg (50.28 KiB) Viewed 1636 times

IMG_8603.jpeg (27.76 KiB) Viewed 1636 times

[schwabd1]

Here's some pics of a of the top of a Bridgeport No 5 I happened to have off a pump. You can see how the top of the pump and the nut squishes the packing. The "antique" packing seems to look like it is oil soaked leather.

[Reno Speedster]

Thanks for the follow up guys.

Allan, your description of how this two tube pump works is spot on.

I got this pump and in addition to the standard worn out leather cup seals, the threaded portion of the cast iron top on the small tube was broken. I made another one of steel and silver soldered it in. So now I now have good threads. The packing goes inside the threaded part and is compressed by a hollow bolt of sorts (that allows the rods to pass through) that compresses the packing. I still need some cup seals and a new hose so it’s still in bits. I have been thinking about making the cup seals (not a tough job) but I might order them.

Here is a photo of the top of the small tube I fixed. The round top is the new part I made.

I added a couple of shots of the repair in progress.

[jab35]

Morgan: Nice work there. My experience with 2-stage hand pumps has been that the pump rod on the small cylinder has to be perfect, any pits or surface roughness will quickly destroy the upper seal. jb

[Reno Speedster]

That makes sense. I plan on polishing the rod and if it’s rough, I can replace it.

As I said I don’t plan on using it, but I wanted a pump to go in the car.