N-Tec to coilspring - how feasible?

[Toxylon]

How feasible is it, technically speaking, to make an N-Tec gasram Diana (350) use a coiled mainspring for a power source?

Hector has a case on his site about turning a coilspring Diana into an N-tec one, with the attendant fitting of the larger trigger casing of the N-Tec system etc., but how about the other way around: keeping the gasram piston, trigger and receiver, and just fitting a rear guide and a mainspring in there?

British tuners have commented on how even the HW90 can be easily converted into a fine coilspring gun, but how about them Dianas? Worst case, there's a substantial structural / dimensional difference between the trigger block fronts against which the rear guide needs to fit. Best case, there is no difference, and things really are straight-forward.

One potential hitch is if the N-Tec piston has a much different ID than the coilspring 350 pistons: the gas strut doesn't need much any space, compared to a coilspring.

I guess this question has Hector's name written all over it, but any insight will be appreciated. There are N-Tec owners here, some of whom must've taken theirs apart.

[Roadworthy]

It should be a fairly simple conversion.  The trigger group is different in the N-Tec models compared to the coil spring models as the coil spring models have a latching rod in the center of the piston for the trigger to grab when cocked.  The gas spring models have a side latching piston to allow the gas spring to take up the internal space.  I do not know the internal diameter of an N-Tec piston so you might wish to measure to ensure clearance for a coil spring.  The outside diameter of a standard Diana spring is about 0.822".  Of course the piston internal diameter would be slightly greater to allow a fit.  Good luck on your project.

[Toxylon]

Thanks, Thomas

Yeah, the side latching piston is a feature not seen on quality coilspring guns, but it's pretty common in the lower price bracket: Gamos and Cometas, and I'm sure many of their Chinese copies / versions, are side latchers, even with coilsprings.

The gasram heads I've seen look quite small. I think there might be a receiver of sorts inside the piston for the gasram head to fit in. This would need to go for the conversion to work.

I don't think the N-Tec piston is actually really small in ID, since such a steel piston would weigh a ton, given the 28mm chamber bore. But even the coilspring 350 piston is snug enough that it doesn't accomodate a Titan #14 without removing the piston liner (and piston weight), so fractions matter.

Apart from the above, the compression space might be an issue. Gasram guns generally have longer strokes than coilspring guns, although this is something spacing should be able to deal with.

[Yogi]

This may help?

https://www.pyramydair.com/model-schematic/m/diana-340-n-tec-premium-air-rifle/3513

-Y

[mikeyb]

Is there a reason for the conversion?
While I've had Hatsan Vortex air springs fail I haven't experienced any Nitrogen Gas Spring failures yet. Has the N-Tec gas spring failed?
If N-Tec is still working well, what is the goal (desired results) from a conversion to coil spring?

Gas springs have very specific hard limits on active length, max compression length, and preload length. Coil springs are much more forgiving until coil bound.

From the schematic alone it looks like a fairly simple project to convert to a coil spring. Making a spring guide and spacers should be easy if you have a lathe with a little more effort if you only have a drill press.

The biggest difficulty I see is finding a suitable spring. MAX OD (when fully compressed) will need to fit inside piston. Wire diameter, coil pitch, and overall length will determine springs stored energy and resulting best-case muzzle energy. I use ME=0.3xSE and usually get results that are surprisingly close.

If it were my project I would first open up my N-Tec and take several critical measurements. I'd then try to find a spring OD that might fit. Over here the company Vortek (http://vortekproducts.com/ourstore/index.php?route=product/category&path=64) sells a fair selection of springs. I've purchased a few max length (max coils open ended) springs for similar experimental conversions.

Once I had a spring in hand that "might" work I'd make a custom spring guide with a snug fit "for that spring". Installation and testing would follow.

It would be a fun project for me :-)

Edit: The trigger latch/holding forces for a coil spring powerplant are usually LARGER than those for a gas spring. I suspect the trigger parts have more than enough design overhead to handle the increased forces/stress, but it is worth noting that these forces will be larger.

[Toxylon]

Thanks, guys

I don't have the N-Tec yet. This is a query about if I want to get one, for other reasons (ie., a gun that is desireable for the hogsback walnut stock etc. rather than the powerplant, and affordable).

N-Tec 350 Mags have proven the nastiest cocking springers around. Users report these guns as way harder to cock than a Hatsan 135 - many have been relegated to wallhanger duties only because of this. It's not about the peak cocking force, but the cocking curve.

Hector himself described the gasram 350: "It's one of those "Dial it to 11" things that never should have happened."

Personally, I have zero issues with the heaviest-cocking coilspring guns, but can't deal with even mid-power gasrams.

While N-Tec rams are much more reliable than most others, they fail as well, mostly from O-ring failure , I think, and are very costly to impossible to replace, now that the N-Tec line has been discontinued for quite some time. You can't just pump some nitrogen in there after switching the O-rings.

Were I to get the N-Tec, I would most certainly shoot it as is, to see for myself what it's about, but there is a barely above zero chance I would keep using it as is, hence the conversion discussion.

[HectorMedina]

You called the Devil . . . .??
Of course you know that your soul is in danger.
Muwahahahahahahaha!

OK, guys, first of all, let me clarify that the NTec gas spring is alive and well. You can still get them. Expensive? Hmmmm, have you seen how much a Venom spring and guide costs? About the same, so, expensive is a relative term.

Second, the conversion can be as complete or as "econo-minded" as the shooter wants. ¿Why?  Because DIANA already has done the work for you! They are the EMS internals
You are talking break barrel vs break barrel, the conversion does NOT work for sliding compression chamber (SCC) guns.

Don't want to buy DIANA parts? OK, then it becomes a little more complicated, but still perfectly doable.

So, let's start with a FULL conversion:
You get the T06 piston for the 350 and the T06 trigger (Non NTec), you get a Titan #14 spring (for full power), or a Titan #1 (slightly lower, but still good power with medium-light pellets), or a Titan #4 spring (high power with heavy pellets), turn the guide to the spring of your choice, change the piston, the trigger, and the guide; and you're done. You will have the NTec Piston, Gas spring, and trigger that you can keep or sell to recoup part of the project's cost.

An "Eco" conversion:
Turn a forward / inside guide out of steel to lodge the spring into the right location for the NTec piston, then turn a polymer rear guide to keep the rear of the spring in place, the forward guide needs to telescope into the rear guide as snugly as possible without drag. It has to be so dimensioned that it uses the "well" where the NTec gas spring screws into the trigger block, and needs to guide the piston into the proper latching position.  It does NOT have to screw into the trigger holding nut, just fit properly into the "well".
If the rear guide has been properly dimensioned the NTec piston will latch into the NTec trigger, even without the rigid guidance of the screwed in gas spring.

So, there you are. Nothing too sophisticated about it. Three ways of accomplishing your wish.

And now, if you will please sign in the dotted line, I'll go away and take the sulphur smell with me.

>;-)







HM

[Toxylon]

Huge thanks, Hector!

This was maybe the 50th time your answer gave ample tools for this Diana home smith.

As a project, I'd be much more interested in an N-Tec / coilspring Frankenstein gun than a T06-equipped gun with just the stock (if that) differentiating it from regular coilspring T06 guns. After all, I already have a T06 coilspring 350.