SpudFiles

I've got to put myself up on this (future) epic topic as well and contribute the the 6 more pages that are coming.

Nice work BTB.

As a mod I should delete your non contributing contribution.


Thanks for all the kind words people.
I'll do a full auto when I get a chance to do so.There is a reason I'm wispering in all the vids, you know...
Hence the 20 seconds...

Maybe this weekend during daytime if I can get the mag working....

It sounds like an actual machinegun so...I don't want to push my luck..

But don;t count on a minute of firing..If I'm lucky I'll be able to fit 20-30 bb's in the mag..

That should be about..what? 4 -5 seconds?

Edit:
Darn!
With a muzzleloaded projectile the ram doesn't hit back like it should.
I moved back the port in the barrel to get more time and I took off the beefy spring and replaced it with a lighter one.
(edit again: that didn't do it but I've got it now!..I think...)

Trouble is, there is a little too much friction on the O-rings of the ram so it has trouble resetting.
Shoving it back and forth seems to make it smoother so I guess I have some shoving to do...like 150 repetitions...

But once it runs smooth the lighter spring is much better.It takes very little force to pull it back now.

Trouble is, there is a little too much friction on the O-rings of the ram so it has trouble resetting.

are they lubricated??

anyway I'd expect something opposite - there should be more recoil when you use ammo... I must say it's surprising

Too much air escaping around the projectile? There is a difference between blocking the barrel and using ammo that doesn't really seal the barrel.
Perhaps some sort of choke on the muzzle is in order.

Brian the brain wrote:Darn!
With a muzzleloaded projectile the ram doesn't hit back like it should.
I moved back the port in the barrel to get more tie and I took off the beefy spring and replaced it with a lighter one.

Trouble is, there is a little too much friction on the O-rings of the ram so it has trouble resetting.
Shoving it back and forth seems to make it smoother so I guess I have some shoving to do...like 150 repetitions...

But once it runs smooth the lighter spring is much better.It takes very little force to pull it back now.

I was wondering if this would happen.

With the barrel jammed all the energy of the air blast was going to the ram.

With the barrel open the pressure drops off much faster so the ram has a lot less force on it.

You could try moving the porting for the ram further back (not sure if that's what you just said you did) or lengthening the barrel (or both) to increase the time the ram has under pressure so it can get the force needed to recock.

Also for consideration, the ram could be made larger (in diameter) so there is more surface area for the pressure to work on.

You're already working on reducing friction and fiddling with the springs.


Poland_Spud, it's the pressure in the barrel and how long it's pressurised for that works the mechanism not the recoil. That's why blocking the barrel is much more effective than using ammo, gives much higher pressure for much longer.

With the barrel jammed all the energy of the air blast was going to the ram.
With the barrel open the pressure drops off much faster.

Exactly!

The ram does work, it just has less force and less travel.( hey that kinda solves the dangerous moving parts...)

This means the QD has to be supersmooth and the part that unlocks it has to be closer to it.
I'll change the QD for a stepped sleeve&bb one we have at work.They should release better under pressure.I forked up this one trying to file out the grooves..wich made it release...all the time..
Too much! Darn!

Oh well.
I did however upgrade the ram.It is completely sealed with floating O-rings, both on the barrel and in between the tubes, reducing the friction by a tonne.
Also, I have taken some of the pressure off the springs so it needs less force to retract and reduced the rams length and thereby dead volume.
So upping the efficienty of the ram while reducing friction.

It seemed to work well enough to knock open a smooth QD, but not the one I had.Under pressure it was too hard to open really..
It was working fine with an open fitting in the muzzle though..So I'm close..Maybe just a longer muzzle tip will do..


So..I'm doing a lot of finetuning for now.
I won;t be surprised if I have to switch to a longer barrel as the time the ram has to do it's dirty work is freaking shrt.
So short even I won't even write short.That would be too long, see?

As hotwired has indicated, there are a lot of things that come into play, but also means a lot of things can still be changed so I'll work it out eventually..

Possible tweaking methods:
Longer barrel
Heavier projectile
Larger diameter ram
Better QD
checkvalve ( flex-hose) over the inlet to the ram
More pressure
Weaker ram return spring


Just a little bummed out I have to go out and buy a special QD for it...so far it was all free..

Longer barrel and larger ram are the two methods of wich I'm sure they'll solve it...but those will also be the last ones for me to try....

@Hotwired

it's the pressure in the barrel and how long it's pressurised for that works the mechanism

lol thx for assuming I didn't know that...
I meant that 'the ram recoils'... though I didn't notice that the barrel was plugged


given the fact that typically it takes about 7-8 ms for ammo to travel down the barrel there is really little time for air to flow to the ram and overcome inertia of it
so I'd say that the simplest solution might be using the inertia to your own advantage... just remove the ram, forget about bolt locking and put a much stronger spring behind the bolt...

this isn't the AK47... so we can't expect to get several thousand psi acting on the gas ram... so I assume that the pure blow-back would suit it better

I'm not sure why you need the locking bolt QD etc. Why not just have the arm of the gas ram link to a bolt housed in a tube extending behind.
The gas ram would start the bolt moving and then the exposed face of the bolt would be forced back by the air.
With a spring behind the bolt retained by a capped pipe it would surely get the job done.

*cough cough*

just remove the ram, forget about bolt locking

That is an absolute ingenius solution.
That will surely solve the fiddling with the ram and boltlock.
Just NOT have them

In fact I think I'll go for a single shot ballvalve cannon instead!
But what if the ballvalve fails?
I'll just stick to throwing rocks...
:violent1:


Hahahaha..
The whole quest is to get them working.I'm not trying to just build a working gun.
I want to explore this concept and hopefully get it to work well.
if not, there is no point to it..
I

Why not just have the arm of the gas ram link to a bolt housed in a tube extending behind.

That would be the last resort.But only if the inertia of the ram is helpful in keeping the bolt closed for long enough..

The gas ram would start the bolt moving and then the exposed face of the bolt would be forced back by the air.

Wouln;t that be the other way around as the air reaches the bolt first...

I'm not sure why you need the locking bolt QD etc.

That's why..

The epoxy-orc wrote:
*cough cough*

Just waiting for me to fail huh..

I've got so many option to make it work I won't give up.

Imagine the first guy trying to build an automobile.
What if he'd encounter a small engine problem, he had to tweak the engine a bit...

And he would think: Maybe I'll just strap it to a horse and be done!

???

I'm all for taking advise...but I gave a list of possible solutions and all you guys seem to advise me is " give up"

You should all be spanked.. and spanked hard!
Except ofcourse JSR, because he is into that sorta thing..

Muhahahaha

Imagine the first guy trying to build an automobile

lol the point is you're not the guy who tries to build a car
(one that works and does stuff that cars do)

you're the guy who wants to build one with square tires
(gas ram and delayed blow-back)

Brian the brain wrote:Just waiting for me to fail huh..

I don't want you to fail (though it's only fair you take up a bit of the share of fail on this forum, now that you're a mod and everything ) - I still think the sleeve is a good idea and will not require locking. If you're worried about jams, you could have an internal sleeve instead of an external one like I illustrated in the diagram (though technically if it was running inside the barrel it would no longer be a sleeve but anyway, semantics...)

You should all be spanked.. and spanked hard!
Except of course JSR, because he is into that sorta thing...

I have no secrets on this forum

What's wrong with square tires???
The wheels match..I don't see the problem...




Anyway..too busy right now rebuilding my totalled scooter.
All it needs is some bondo and...the crownplate wich holds the forks to be realigned.
Thankfully my neighbour has a complete shop to do it.He's a restaurator of (70 year) old motorcycles.
He does this all the time.
So far for a total loss..30 euro's and it;s good as new..
Well..all flat black...


More about the gun:

I'll try and fix either my stubborn-ness or the system..by trying to complete the cannon, when the scooter is done..

Wether I fail or succeed, I will have proven a point.
This project will tell if gasram-boltlock has any future.

( edit: I have lengthened the barrel, wich I said I would do last..
This time I can see the ram respond, but it lacks force to unlock the bolt...so...I need a bigger diameter ram.The exposed surface area is quite small really. Going to a 40 mm ram will give me about 5 times the force)

I know the simple bolt does work excellent.
This was the most important discovery I made..
It is very easy to convert this thing to pump action now.


We'll see how it works out..

Blow-forward instead of blow-back.

For example, when most people think about putting square wheels on a car, they think it is a bad idea, because it would lead to a number of mechanical problems. However, by using lateral thinking, someone could say that perhaps a suspension system would be designed that could support a car with square wheels, since all four wheels would have a predictable "bump" as the car moves. As you can see, lateral thinking got rid of the concept that cars with square wheels would have engineering problems.

And then they came up with active suspension

Have you tried the system with no spring at all, just as a single shot ?
I had no O-rings on the gas piston just silicon grease and only needed an elastic band to return the piston. Maybe a consideration for the new ram. Also the bolt lock shape gave the ram a mechanical force multiplier through leverage, not sure how that could be used with the quick disconnect.
The bolt and ram have to be as light as possible to get the most acceleration from the start.

How much porting is there to the gas ram ? Flow restrictions will definitely be a problem with fast moving projectiles.

And yes I must agree this the locked bolt system is great for pump action, lever action etc..