Solving pump-pistol issues

[Brian the brain]

Lately I have been pondering over some exotic idea's.

One came from my desire to build a compact pump pistol.
While an integrated pump offers free pressure and a sense of independance it has a downside.
Lets take some crosman pistols as an example..

The disadvantage in terms of compactness ,of the well known Crosman 1377 pump models ( I owned one)to me, is that the pistol is longer than it's cousin, the CO2 bulb powered 2240.

Ofcourse, this is due to the room the pump assembly takes up.

I came up with a rather exotic idea.
Why not cut off the front leaving the checkvalve as the most forward part...and sleeve a housing over it.
machine some O-rings in the original reservoir and by sliding the sleeve forward, have it suck in air.Push it back and air will be compressed into the reservoir...right?

this means the pistol can be shorter with the sleeve compressed.
A lever, in my concept an extended triggerguard would pull back the outer sleeve and basically work just as well as the traditional pump lever.
It's all just flipped around and reversed.
Ofcourse I don't mean to do so with a crossman, I'd rather build my own pistol along the lines of my lever action.

I figured a barrel sleeve on top of the external pumpsleeve would offer stability...and function as a breechloader opportunity.
This could really work well in a single stroke pump design, if you could live with the lower powerlevels.
In that case you could have it load a projectile automatically apon each ( single) stroke


The same idea would help to keep a pump up- linear hammer design fairly short.
Offcourse the lever could be placed back over a shoulderstock if you'd like to.

Another plus ( I think) is that you'll have no slots cut out of the tube.
So I present:

The EX-tegrated pump:

[jackssmirkingrevenge]

Lately I have been pondering over some exotic idea's.

That alone is great to hear, seriously

I like it, the chamber though would have to be pretty small diameter in order to make the forces viable for manual pumping. Also, it's quite a short stroke so that's a lot of pumping to get the sort of bar one usually expects from your projects...

Remember that the Crosman 1377 has a tiny, one shot chamber:



If you want more than one shot from yours, that's going to be quite a bit of exercise...

[Brian the brain]

I like it, the chamber though would have to be pretty small diameter in order to make the forces viable for manual pumping. Also, it's quite a short stroke so that's a lot of pumping to get the sort of bar one usually expects from your projects...

A logical response..

The forces involved can be overcome with enough leverage.
A 25-30mm diameter should pose no problem from what I've learned with the Lever-action.
( did I ever nickname that one?)

The drawing is by no means to scale..
The distance between the front of the checkvalve and the connection to the barrel could easily be up to 15cm.

With an expected stroke of about 11 cm I'd say it would surpass my latest build when it comes to pumpvolume.

It remains to be seen how much leverage would suffice and how short the stroke can be to still be effective.

It doesn't have to have multishot capacity from a single filling.
I'd do 20-30 pumps per shot if I had to in order to get the compactness.

all dimensions aside, the EXtegrated pump idea will still eliminate the need for the usual added pump length.

The simplest solution would be a detachable pump, but I want the best of both worlds when I know it's possible.

In my marriage I'd like the same ...wife says that's not gonna happen...In this case I set the rules..

[jackssmirkingrevenge]

If it's for a single shot, more than viable. If you need some machined parts on the cheap let me know and I'll see what I can do

[Brian the brain]

I just got another piece of brass roundbar..
As you can expect I design my stuff based on what I can buy or make myself.

at the moment I have no need for milled stuff.
A lathe I got..

Thanks for the offer...one of these days I'll take it!
Even if it is just to have a real "JSR" piece.

As I said...I'm pondering over several idea's.
One of them is to completely redo Old Shat with the knowlegde, skills and tools I have today.
Several versions have crossed my mind.

A balanced hammervalve ( different design this time) version, one where the QEv and hammervalve combo stays, but the reservoir runs back into the shoulderstock.
That would make leveraction a very easy feat.
Girandoni flipped on it's side and a lever working the breechblock..

Another would be a "not so"rifle with traditional integrated pump , but using the ( heavy duty) barrel as the pumparm to minimise parts and create a loading opportunity at the same time.
( barrel swings up so breech is exposed)

I like a "minimal"approach
Whenever I can do the same with less, get a part to multitask or get results in a smaller package I'm happy.
Bulk should be a choice, not the result of a lack of insight or design capabilities..

[dahakka]

nice to see you BTB
as usual , i don't understand your drawing , but still exiting

[jackssmirkingrevenge]

If it's just for single shot, why not forget about the lever and just use a small bore pump? You can get to silly pressures in a small chamber, and as we know small volume high pressure vields more power than large volume low pressure.

Remember this? https://sites.google.com/site/inov8ived ... icropistol

Say you used a tiny bore, 3mm. Taking it to 400 bar will require less than 30kg of force...

Actually, now that I have machine tools to go with my SCUBA tank, a "proper" HPA (in the 200-300 bar operating range) launcher is long overdue... so many projects, so little time!

[Brian the brain]

If it's just for single shot, why not forget about the lever and just use a small bore pump? You can get to silly pressures in a small chamber, and as we know small volume high pressure vields more power than large volume low pressure.

I think your missing the point....

Same reservoir volume with a similar amount of strokes to reach a similar pressure without the extra length.
That's the idea.


If you remember my "pirate pistol"...a short coax basically..?
I remember using the barrel as the pumptube and the piston as a checkvalve...Pretty simple idea..

IT TOOK FOREVER!!
And still the short stroke and diameter meant low endpressure.
Dead volume and loss weigh heavily when things are small...

[jackssmirkingrevenge]

Same reservoir volume with a similar amount of strokes to reach a similar pressure without the extra length.
That's the idea.

Fair point, I'm just averse to levers I guess

If you remember my "pirate pistol"...a short coax basically..?
I remember using the barrel as the pumptube and the piston as a checkvalve...Pretty simple idea..

That's brilliant! Bloody hell, if the pump head is flat dead volume would be practically zero!

I had to dig upthe thread to check if I had missed it but it doesn't seem you mentioned it.

Might not be practical for a largish bore short barrel, but for say a 0.22 with a 15 inch barrel...

[Brian the brain]

It was annoying to insert that floating O-ring...it kept popping out on the up stroke and I never really reached anything close to the pressure I had hoped for.

Seemed like ..futile to me.

now that I think about it...the piston head was probably not made that well..lots of O-ring travel and built-in dead space..


Why don't you machine one with as little dead space as possible
worlds smallest checkvalve NO O-ring slack..rounded out O-ring groove perhaps..

A compression cap over a threaded muzzle would prevent the piston popping out.

Just think how sweet that would look on a musket style coax..

[Lockednloaded]

That's amazing, with a small enough chamber and a long enough barrel, you could fill it just by loading the gun with an o-ringed ram-rod (assuming the dead space from the ammo wouldn't interfere too much)

[jackssmirkingrevenge]

That's amazing, with a small enough chamber and a long enough barrel, you could fill it just by loading the gun with an o-ringed ram-rod

That's exactly what came to mind.

(assuming the dead space from the ammo wouldn't interfere too much)

In the interests of safety and practicality I would imagine projectile loading takes place after the thing has been charged.

now that I think about it...the piston head was probably not made that well..lots of O-ring travel and built-in dead space..

Sounds like this was the case.

Why don't you machine one with as little dead space as possible
worlds smallest checkvalve NO O-ring slack..rounded out O-ring groove perhaps..

A compression cap over a threaded muzzle would prevent the piston popping out.

Just think how sweet that would look on a musket style coax..

Not a huge fan of muskets, but I've been wanting to make a pneumatic Welrod for ages...



Let's see, a 30cm long 5.5mm ID barrel, that's around 7mL. Let's say 5mL chamber + pilot volume, assuming no dead space and no heat losses, every stroke should give us around 20 psi in the chamber, so that's at least 50 strokes to reach 1,000 psi - but at that pressure, that's around 16kg of force that is needed. Bu way of comparison, a shock pump at 400 psi needs around 22kg at the bottom of the stroke.

Tempted, but with 4500 psi on tap from my SCUBA, not sure if its worth it.

Also, at these sort of pressures using a schrader as a pilot would need a lot of force that would likely damage the stem. On the other hand, if you're not filling with a pump but through the barrel, you don't have to include a schrader... hmmm...

edit: What if you use a QDV, and incorporate a check valve (a schrader will do...) into the piston opening to the face...

Here's a quick sketch (based on an old Labtec QDV drawing ):

[wyz2285]

If I remember correctly, a schrader´s open pressure is around 1bar, the piston of the QDV would have opened with that pressure in front of it? Unless a locking mechanism on the trigger rod to temporally hold the piston in place.

[jackssmirkingrevenge]

If I remember correctly, a schrader´s open pressure is around 1bar

Actually more around 4 bar... I just put that there as an example, but a custom check valve with much lower cracking pressure can easily be made with a steel ball and an o-ring

Unless a locking mechanism on the trigger rod to temporally hold the piston in place.

The way I see it, you would be resting the launcher on a hard surface while pumping, properly designed this would keep the piston in place.

I'm tempted to make this but every time I think about a single shot pneumatic the thought comes to me that "If I made this a hybrid instead, it would be more powerful..."

[wyz2285]

Actually more around 4 bar

Not my case then my was around 15 psi.

"If I made this a hybrid instead, it would be more powerful..."

Well, a hybrid you need to care about the fuel, for a solid pneumatic, you just have to keep pumping, specially we are talking about a intergrated pump, for a hybrid you need to carry around a bottle of fuel and a syringe.