Foot pump?

[Antoni]

Lada Cars used to be supplied with stirrup pumps.

If you use a stirrup pump your whole upper body mass must oscillate vertically, but when I use my ancient and excellent 'Kismet Popular' foot pump on my car only my leg mass has to move, the leg muscles involved in the process are relatively powerful.

Why have I never seen a foot pump for pcp airguns?

[derekm]

Too short a stroke maybe?

[Phil Russell]

Interesting question and I guess the answer lies within several considerations of car tyres only needing c. 30psi (just over 2 bar) and the fact that even a foot pump can be somewhat unstable to pump.
A stirrup pump is inherently more stable and I suspect the force you can apply in the simple 'stirrup pump' motion is higher than knee pumping.

Interesting though ... I wonder if anyone will try to make one .. but I doubt if the wide bore, short length design would work ... maybe need some lateral thought to get the required stroke for a multi stage pump.
Cheers, Phil

[Antoni]

The degree of compression is just down to the dead volume at the end of the stroke. If a single stage 'long thin' pump works , why not a 'short fat' pump using the higher degree of force you can get from your leg pushing against your static upper body mass?

Yes foot pumps are less stable, but that's why I specified my ancient British made foot pump, it's heavily built and stays solid as you use it. The cheap light-weight Chinese rubbish I carry in the boot wobbles a bit but will do its job when really needed.

It would be very easy to design a really stable foot pump.

[Phil Russell]

There is a world of difference between the stirrup pumps used for air cylinders and a car tyre foot pump. As above, car pumps are only used for maybe 2 bar ... Ok say 6 bar or so if you include cycle tyres... but still much less than the 200bar of an air rifle. The rifle pumps are multistage to provide the gearing needed to compress the air volume to the required pressure.
The greatest pressure you can exert on a foot pump depends on your weight ... as the area in the pump increases then the pressure decreases to equalise the pressure of you acting on the pump.
So ... gearing; achieved by using multiple compression stages. Maybe a foot pump one could be developed. Have a go ....

Cheers, Phil

[angrybear]

The degree of compression is just down to the dead volume at the end of the stroke. If a single stage 'long thin' pump works , why not a 'short fat' pump using the higher degree of force you can get from your leg pushing against your static upper body mass?

Yes foot pumps are less stable, but that's why I specified my ancient British made foot pump, it's heavily built and stays solid as you use it. The cheap light-weight Chinese rubbish I carry in the boot wobbles a bit but will do its job when really needed.

It would be very easy to design a really stable foot pump.

The whole concept of high pressure hydraulics & pneumatics revolves around the small surface area of the "pump" compared to the large surface area (or volume) of the ram doing the work, or cylinder storing the pressure, so no, a short fat pump will not work.

[Antoni]

The whole concept of high pressure hydraulics & pneumatics revolves around the small surface area of the "pump" compared to the large surface area (or volume) of the ram doing the work, or cylinder storing the pressure, so no, a short fat pump will not work.

I think it would work if there was a 'mechanical advantage' designed into the way the piston is driven into the 'difficult end' at the last few percent of the stroke.

I was not aware that airgun stirrup pumps were multi-stage. The one I had a go with didn't seem to be - it was very simple.

My original point is that the effort can be done more efficiently from a human ergonomic point of view. It could be done more efficiently in terms of human effort with a bit of mechanical design effort. Look how cleverly modern wind-screen wipers work - not the old-fasioned wiper on a pinion, but a relatively simple arrangement of 'pantograph' levers which make the wipers cover more area of the wind-screen.

The brains behind designing and manufacturing such a system would be the job of them wot can.

Innovation.

Then the Chinese would copy it and everybody would be able to afford it 'till it failed and they had to buy another one.

[Shed tuner]

The whole concept of high pressure hydraulics & pneumatics revolves around the small surface area of the "pump" compared to the large surface area (or volume) of the ram doing the work, or cylinder storing the pressure, so no, a short fat pump will not work.

I think that's probably true.

Why not, for example, build a really compact springer with a 100mm diameter cylinder and a 10mm stroke ? same thing in reverse.. longer strokes with smaller diameters are much more efficient at higher pressures.

Same with a short stroke foot pump - fine for an air matress, not for 200 BAR...

[brassbanjo]

Lada Cars used to be supplied with stirrup pumps.

If you use a stirrup pump your whole upper body mass must oscillate vertically, but when I use my ancient and excellent 'Kismet Popular' foot pump on my car only my leg mass has to move, the leg muscles involved in the process are relatively powerful.

Why have I never seen a foot pump for pcp airguns?

Airgun pumps are 3 stage and there is compression in both directions - you have to push down but also have to pull back up.

If you did build a footpump with 3-stage compression you could push down with the foot but I don't see how you could pull back up?

[Antoni]

No you wouldn't be able to pull up with a foot-pump.

The stirrup pump I 'had a go with' to charge my friends air rifle worked in the downward direction only, no effort was needed to raise the handle other than raising my torso. It did fully charge the rifle and I did have to go to his bathroom for a freshen-up afterward.

[bezzer]

You won't match the power you can put into a stirrup pump with simple foot power. You can't use more than the one foot/leg so wouldn't be able to get anywhere near decent power into it and keep your balance. The only way to use foot/leg power would be to have something like an excercise leg press machine where you could sit and use the full power of both legs to work a pump....the downsides being the space needed and the cost which would no doubt be more than a decent compressor.

[Antoni]

You won't match the power you can put into a stirrup pump with simple foot power. You can't use more than the one foot/leg so wouldn't be able to get anywhere near decent power into it and keep your balance. The only way to use foot/leg power would be to have something like an excercise leg press machine where you could sit and use the full power of both legs to work a pump....the downsides being the space needed and the cost which would no doubt be more than a decent compressor.

Maybe the Lada Car company were right in their decision to issue a stirrup pump then.

But you can alternate the use of your left and right leg when operating a foot pump. I always do.

I haven't seen a killer reason yet for a foot airgun pump not being feasible.

[bezzer]

But you can alternate the use of your left and right leg when operating a foot pump. I always do.

I haven't seen a killer reason yet for a foot airgun pump not being feasible.

Nothing to do with alternating at all, you will never get the power needed pushing down with one foot whilst keeping your balance which is one big killer reason. Then you can add all the others already mentioned which you seem to be just totally ignoring.

[brassbanjo]

Maybe the Lada Car company were right in their decision to issue a stirrup pump then.

But you can alternate the use of your left and right leg when operating a foot pump. I always do.

I haven't seen a killer reason yet for a foot airgun pump not being feasible.

Crosman at one point were going to bring out an "improved" pump that was going to make things easier:

https://airgun-explorer.tumblr.com/p...-psi-hand-pump

but it seems to have died a death

[Antoni]

Nothing to do with alternating at all, you will never get the power needed pushing down with one foot whilst keeping your balance which is one big killer reason. Then you can add all the others already mentioned which you seem to be just totally ignoring.

No, really, I'm not at all ignoring the contributions to this thread.

Your legs are powerful and you have two of them. They can be used one at a time. The power absorbed from each stroke can be designed to be friendly to leg power. Using leg power means less wasted energy in raising and lowering upper body mass.

That's the point of this point. Now I'll shut up for a bit.