Open Question: Would you buy, at around $800 a newly built Giss_ Actioned

[Oldgringo]

Nope, I'd rather have a new truck.   

[HectorMedina]

GOOD that we all keep our sense of humour.

At present we are examining all our options. Some projects are further along than others and have a higher probability of success, so they will get priority, some others are not urgent, but are important, and so, they will get done, just not straightaway.

I cannot give you a lot more details, but next year SHOT Show should be a very interesting year and IWA will see a lot of attention on notable improvements to the airgun technology.

Keep your fingers crossed and keep insisting on this.

;-)








HM

[dan_house]

soooooo... I have between _now_ and the SHOT show to save up?

Please keep us posted!!

[Gear_Junkie]

I'm looking forward to hearing more...

[Scotchmo]

Side lever. I prefer the unencumbered barrel of a side lever.

11-12fpe minimum.

I would be interested as it's similar to a project that I started but abandoned (technical difficulties). I used a single piston and a counter-mass (like a D75).

[Mole2017]

Side lever. I prefer the unencumbered barrel of a side lever.

11-12fpe minimum.

I would be interested as it's similar to a project that I started but abandoned (technical difficulties). I used a single piston and a counter-mass (like a D75).

...

I think I'd drop the rack and pinion in favor of an aramid string/cable, e.g. spectra. Less noise and wear and tear.  You might even be able to introduce some mechanical advantage to reduce the size of the counter-mass, e.g. use a pulley. The tricky part is to make it double acting to properly couple the two masses, especially when the active piston starts decelerating at the end of the stroke--you can't push a string. I think that would end up with a loop and a couple of idlers...it could get pretty weird.

Maybe let the counter-mass act on an air cushion at the end of its stroke as well, just to act as a brake? That may not have to be perfect to be effective.

Oh, or maybe replace the rack and pinion with band drives using aramid bands instead of metal bands. (Some old hard drives used this as a zero backlash method of moving the read heads with rotary stepper motor.)

Hmm...that might make a few of us crank up the simulations to see what kind of forces are acting the strings or racks or whatever coupling you come up with...

Is there an advantage of the Giss system over a sled system like the Diana 54?

[Seanh]

I would have an interest. Definitely would need to be a side Cocker. I don't shoot from a bench and less to Simply sight in the gun. Under lever and break barrel both require me to change my shooting position in order to cock the rifle side lever I can stay in my shooting position prone,  sitting or standing.

I would be looking at a dual power design already suggested.  Maybe short stroking the spring / gas piston. Possibly a multi cock design or appropriate valving of the second piston.

Personally, weight is not an issue for me. But I can see where can be for those smaller in stature.   I think a realistic weight for something like this is going to be closer the 10 lb for Quality build and keeping the price point.

If it does come with sights I'd like to see the site moved from the middle of the rifle to the back of the receiver and offer a globe front sight.

[Scotchmo]

Side lever. I prefer the unencumbered barrel of a side lever.

11-12fpe minimum.

I would be interested as it's similar to a project that I started but abandoned (technical difficulties). I used a single piston and a counter-mass (like a D75).

...

I think I'd drop the rack and pinion in favor of an aramid string/cable, e.g. spectra. Less noise and wear and tear.  You might even be able to introduce some mechanical advantage to reduce the size of the counter-mass, e.g. use a pulley. The tricky part is to make it double acting to properly couple the two masses, especially when the active piston starts decelerating at the end of the stroke--you can't push a string. I think that would end up with a loop and a couple of idlers...it could get pretty weird.

Maybe let the counter-mass act on an air cushion at the end of its stroke as well, just to act as a brake? That may not have to be perfect to be effective.

Oh, or maybe replace the rack and pinion with band drives using aramid bands instead of metal bands. (Some old hard drives used this as a zero backlash method of moving the read heads with rotary stepper motor.)

Hmm...that might make a few of us crank up the simulations to see what kind of forces are acting the strings or racks or whatever coupling you come up with...

Is there an advantage of the Giss system over a sled system like the Diana 54?

The single piston with counter-mass has some unique problems. The forces involved are a lot higher than you would at first think. The Diana 75 type mechanism was used in relatively low energy guns so it was doable. Even at 12fpe, the linkage system is problematic, though possible with the right manufacturing capability. On my design, I had designed one of the main parts of the rack/linkage to be carbon fiber but was not able to produce a satisfactory part. Everything else I came up with was too weak and/or too heavy. A true Giss system like the Whiscombe, uses two opposing pistons that are geared together. The two pistons see equal force so the gearing mostly synchronizes them. They see a lot lower stress.

On a single piston system with counter-mass, any additional cushion added to intercept the counter-mass steals energy that would otherwise have compressed the air and propelled the pellet - so efficiency suffers.

The sled system subjects the scopes to higher accelerations than a normal piston gun. There are work arounds like the Diana Bullseye mount. The Giss system does not stress the scope.

[fwbsport]

Nope, I'd rather have a new truck.   

+2

[HectorMedina]

Interesting ideas, but the single acting piston has been discarded.

Reason is simple: If you want a swept volume with a minimum of size and weight, you need BOTH pistons to do work.
IF the currently existing Giss System rifles (DIANA 60, 65, 66 and 75) were of the "coming at each other" variety instead of the "going away from each other" variety we would already have 11 ft-lbs guns, just because the mass, spring force and swept volume actually doing work would double.

Not so sure about the side cocking, one of the ideas is to create a break-barrel with dual cocking levers, just that one would push and the other would pull.

The easiest embodiment is the underlever.

We'll see.

And if anyone thinks they can get a new truck for less than $1,000 . . . perhaps they are looking at different brands than what I am seeing.

;-)









HM

[Scotchmo]

Interesting ideas, but the single acting piston has been discarded.

Reason is simple: If you want a swept volume with a minimum of size and weight, you need BOTH pistons to do work.
IF the currently existing Giss System rifles (DIANA 60, 65, 66 and 75) were of the "coming at each other" variety instead of the "going away from each other" variety we would already have 11 ft-lbs guns, just because the mass, spring force and swept volume actually doing work would double.

Not so sure about the side cocking, one of the ideas is to create a break-barrel with dual cocking levers, just that one would push and the other would pull.

The easiest embodiment is the underlever.

We'll see.

And if anyone thinks they can get a new truck for less than $1,000 . . . perhaps they are looking at different brands than what I am seeing.

;-)









HM

"...If you want a swept volume with a minimum of size and weight, you need BOTH pistons to do work...."

+1

"...IF the currently existing Giss System rifles (DIANA 60, 65, 66 and 75) were of the "coming at each other" variety instead of the "going away from each other" variety we would already have 11 ft-lbs guns, just because the mass, spring force and swept volume actually doing work would double...."

The Giss System patent shows two pistons "coming at each other" and synchronized by a rack and pinion. The 60, 65, 66, and 75 have a single piston and a counter-mass "going away from each other". Though they too are synchronized by a rack and pinion, they do not appear to be a "Giss System". I don't know if they had there own patent, but they look like a unique system.

"Not so sure about the side cocking, one of the ideas is to create a break-barrel with dual cocking levers, just that one would push and the other would pull...."

There were some interesting build threads on the machine board a few years back. The designs had a dual piston that used a forward/backward sidelever. They had a simultaneous sear release though no other synchronizing mechanism.

The dual piston semi-bullpup configuration has some advantages.

https://www.gatewaytoairguns.org/GTA/index.php?topic=58977.msg568590#msg568590

[HectorMedina]

Scott;

Yes there are several Giss patents. Simply because Kurt Giss was one the head designers for DIANA after WWII.
The most interesting one for our modern purposes is # 2,938,513 under USPTO numbering of May 31, 1960, but there are patents going way back to 1956 with different variations.

The MAIN advantage of a semi-bullpup cofiguration is the simplification of the trigger system.

Interesting thread by American Airguns, and definitely on the right track. I wonder/ Do you know if a prototype ever got built?

Keep well and thanks!






HM

[Scotchmo]

Scott;

Yes there are several Giss patents. Simply because Kurt Giss was one the head designers for DIANA after WWII.
The most interesting one for our modern purposes is # 2,938,513 under USPTO numbering of May 31, 1960, but there are patents going way back to 1956 with different variations.

The MAIN advantage of a semi-bullpup cofiguration is the simplification of the trigger system.

Interesting thread by American Airguns, and definitely on the right track. I wonder/ Do you know if a prototype ever got built?

Keep well and thanks!






HM

He did build a prototype, but not the bullpup.

https://www.gatewaytoairguns.org/GTA/index.php?topic=25115.0

I guess the independent pistons balanced out well and did not require the rack and pinion for synchronization. The large bore diameter required heavy pistons. He never got the fpe that he was going for, but it was still over 12fpe.

[HectorMedina]

Thanks for the link, Scott!

As was evident from the result, as masterful as the embodiment was, it strayed too much from established parameters to work well.

I found particularly troubling the idea of charging gas springs to 1,200 and then 2.400 PSI for yields of 20 "ísh" ft-lbs. in 0.22" cal.

One of the projects we are working on right now as high priority tells me that you do not need more than 900 PSI / 62 BAR to reach 20 ft-lbs in 0.22"cal with less than 40 lbs of peak cocking force in a SINGLE piston architecture /135 degrees cocking arc, 30 mm's bore/100 mm's stroke. Working with double pistons, we should be able to keep the key numbers but by splitting the stroke the lock time should halve and recoil should go away.

Synchronizing pinions and racks are also vital to a good working gun in the long run.

Lots of really masterful machining in that thread, but totally unfeasible as an industrial product. Compliments to QV Tom, and thanks to you for the lesson!

Keep well and shoot straight!






HM

[fwbsport]

Thanks for the link, Scott!

As was evident from the result, as masterful as the embodiment was, it strayed too much from established parameters to work well.

I found particularly troubling the idea of charging gas springs to 1,200 and then 2.400 PSI for yields of 20 "ísh" ft-lbs. in 0.22" cal.

One of the projects we are working on right now as high priority tells me that you do not need more than 900 PSI / 62 BAR to reach 20 ft-lbs in 0.22"cal with less than 40 lbs of peak cocking force in a SINGLE piston architecture /135 degrees cocking arc, 30 mm's bore/100 mm's stroke. Working with double pistons, we should be able to keep the key numbers but by splitting the stroke the lock time should halve and recoil should go away.

Synchronizing pinions and racks are also vital to a good working gun in the long run.

Lots of really masterful machining in that thread, but totally unfeasible as an industrial product. Compliments to QV Tom, and thanks to you for the lesson!

Keep well and shoot straight!






HM

Now about that truck......

[Scotchmo]

...
I found particularly troubling the idea of charging gas springs to 1,200 and then 2.400 PSI for yields of 20 "ísh" ft-lbs. in 0.22" cal.

One of the projects we are working on right now as high priority tells me that you do not need more than 900 PSI / 62 BAR to reach 20 ft-lbs in 0.22"cal ...
...

Whether it needs 900psi or 1200psi to achieve a certain force would be a function of the shaft diameter. So either could work.

In a gas spring, the shaft cross section area x psi determines the force in pounds.

[HectorMedina]

...
I found particularly troubling the idea of charging gas springs to 1,200 and then 2.400 PSI for yields of 20 "ísh" ft-lbs. in 0.22" cal.

One of the projects we are working on right now as high priority tells me that you do not need more than 900 PSI / 62 BAR to reach 20 ft-lbs in 0.22"cal ...
...

Whether it needs 900psi or 1200psi to achieve a certain force would be a function of the shaft diameter. So either could work.

In a gas spring, the shaft cross section area x psi determines the force in pounds.

Yes and no.

Yes in the sense that in a perfect world the maths are "pure", once you get into the realities of tolerances, frictions (static and dynamic) and starting pressures in the gas spring hysteresis cycle, there are differences that can account for up to half of the energy returned. So you may need 1.5 times the input "work" to get the same returned energy.
Like in this case. IIUC, 2,300 PSI's returned barely 25 ft-lbs; 2.5 times the pressure for 25% more muzzle energy is too high a price to pay, IMHO.

Given the current technology, we know we can charge a gas spring to 4,500 PSI, but what good would that be if the gas spring so charged is not efficient, and above all impossible for a person to cock the action?

We also know that we can get 20 ft-lbs from a spring charged to 22 BAR, but again, that is also not a practical weight rifle because the stem is only part of the equation, there is a piston head at the end of the stem inside the cylinder.

Keep well and shoot straight!







HM

[Scotchmo]

I did quite a bit of research and experimenting with gas springs in piston guns. Though gas springs have some advantages, I now prefer wire springs for my target rifles.

Because of the likely trigger configuration, this new design could probably use either gas springs or wire springs.

[HectorMedina]

I did quite a bit of research and experimenting with gas springs in piston guns. Though gas springs have some advantages, I now prefer wire springs for my target rifles.

Because of the likely trigger configuration, this new design could probably use either gas springs or wire springs.

You are right. Steel springs are still more efficient.
For example, comparing exactly the same architecture and ONLY changing the nature of the spring, we need 25# of peak cocking force for a 12 ft-lbs yield, while only needing 20# of peak cocking force with a steel spring and an ABP device.

BUT, the quality of the shot cycle is so much superior using the gas spring that I deem it a worthwhile trade-off.

Let me put it this way:
If a "conventional" 34 kicks at 100, the ABP version kicks at 40, but the GasRam system kicks at 25.

We are looking at using just one trigger type for all guns, and that requires re-thinking EVERYTHING inside the guns.
That's what keeps me extremely busy and sometimes awake at nights, LOL!

As I said, SHOT and IWA 2020 are going to be VERY interesting.

😉

Keep well and shoot straight!



HM

[MartyMcFly]

Hector,

Since you are rethinking “EVERYTHING” about the internals of a spring gun I was wondering what your thoughts are about friction reduction inside the compression chamber. I ask because for the most part the largest change in airgun design pertaining to friction reduction appears to be the use of moly for lubricants and use of self lubricating seals. Sadly, these improvements are often an aftermarket fix. Is DIANA considering any other friction reduction methods, such as coating the compression chamber, trigger sear, or piston contact points with something more advanced like Teflon? I have no clue about the cost vs. benefit, but thought it worth asking the question to gain more insight.

-Marty