7,5 Joules V-Mach für HW 97 sinnvoll?

Nein, aber vielleicht die LM in Wernsdorf

Wenn die Lanes in Wernsdorf für 16 J zugelassen sind, könnte man einen Termin festlegen...

Jetzt hab ich die Antwort auf die Frage gefunden, warum es in meiner HW 97 KT mit 7,5 V-Mach Kit so rappelt:

Zitat

Transfer port tuning:

77 and 97, the TP is around 6mm long. Normally it can range from 2.9 to 3.2mm depending on year of manufacture etc. Now because the TP is so short you can tune it to around 4mm. Do NOT use a drill for this, it has to be reamed out and be parallel and true...invest in the right tools to do the job

Why can it be taken out to 4mm and be ok?

It has to do with the static compression, because the TP is short the SCR (Static Compression Ratio) is high, on a 25mm piston standard gun with standard stroke it is over 800:1. So we can open the TP to increase flow and still retain a high SCR...so increasing power, or delivering the same power with less spring.

What does the SCR do?

Well roughly it gives you an indication where the piston will bounce, it also will give you an indication of how high the pressure pulse will be the piston delivers. High SCR thru a narrow port will produce a high pressure pulse but also the piston will bounce further away from the breech....so a stiffer spring may be needed.

You can tune piston bounce with the SCR...by opening the TP, you can also tune the piston bounce with piston weight.

The goal when tuning a springer is to get the piston to halt with little to no bounce just before the breech, the TP has good flow and the pellet gives the velocity you require with a given spring pressure. Consider a stock factory supplied Diana 52 in UK spec factory supplied....go shoot one...it will rattle all the fillings out your teeth...why?

Diana fit the guns with long springs, the spring will deliver some serious grunt, the D52 and for that matter most Diana air rifles have 4mm dia TP, in the case of the D52 its 4mm and 6mm long adding in the breech seal...BUT they add a thin restrictor washer with a 2mm hole right behind the breech seal.
What this does is massively increase the SCR, even with a piston weighing 300g+ and a spring that will deliver way over 16j the rifles deliver around 10.5 or 15J, but the piston bounces back and forth violently and the shot cycle is utterly horrid. The SCR on a D52 is over 1500:1 for those wondering.
So, most people remove the restrictor and cut the spring down...it shoots a little nicer, but you still get piston bounce, and this happens a lot on the HW80 also..here is why.

The D52 and HW80 are FAC guns, the pistons weigh 300g+ and the rifles have large swept volumes. When you chops the springs down or fit short stiff springs you end up with little to zero preload. This is bad...infact seriously bad and here is why. The piston has to resist the SCR to stop bouncing, it can only do this if there is still a reasonable amount of spring force acting upon it. So you tune an 80 and you end up with a spring with 4mm preload total, when you shoot the gun the piston flies forward, it has high inertia but the SCR eventually overcomes it and pushes the piston backwards, the issue is there is little to no pressure being applied by the spring...so the piston bounces...usually back and forth 2 or 3 times. In the case of the Diana 52, because its a massively efficient rifle the spring is actually thinner than an 80 spring and you still end up with little to no preload on an 11foe gun and the shot cycle is equally as horrid in this state of tune.

So...whats the cure....LESS SWEPT VOLUME...optimised TP and a spring that delivers the right amount of preload to counter bounce and allow the piston to settle to rest and give that dull thud shot cycle we all like.
In the case of the 97 and 77, the 26mm piston guns have more swept volume and a heavier piston, the 26mm pistons weigh in around 265g where the 25mm pistons weight in around 230g, the 25mm pistons with 81mm stroke in .177 work best with a TP around 3.6 to 3.9mm. If you short stroke to 75mm and increase weight to say 250g then a 3.9mm TP works best.
For the 26mm guns, 74mm for .177 with a 3.6 to 3.9mm TP and 70mm same size TP as .177 BUT this all depends on piston weight. if lightened to 250g the TP may be slightly smaller, if light weight then the larger TP will help the piston not bounce so much. On 26mm guns it looks like even shorter stroke may be possible but i have not tested down below 70mm as yet, 75mm x 25mm bore = 36.8CC and this is found at 69mm stroke on a 26mm bore...i set 70 just to be sure. I use 75mm for .177 25mm with 250g pistons, and 82mm stroke on 235g pistons.

So, transfer port tuning all depends on the amount of air, the size of the piston, the weight of the piston and the stroke the piston has....so what is the optimum SCR?

T 20 brought tot he table the idea of the SCR, to measure it accurately you need to consider all the lost volume within the parachute style seals etc we use but as a rough rule T 20 was advising 300:1. I found this fine for the 10mm long and 15mm long TP guns but the short TP guns like the 97 and 77 I use 450:1 or so...ignoring lost volume and just using this equation.

swept volume/transfer port volume = SCR:1

Last..a few lads on here talk about springs in their guns with no preload...if the spring had no preload then the spring would rattle in the gun, the piston would bounce like crazy and the gun would be horrid to shoot.
To measure the true preload, install the spring into the gun and measure how far you have to screw the trigger block in fully home on an 80 or 97 etc, or how far you have to push the trigger block in on a 95, on average V-mach springs usually have around 20 to 30mm preload on a HW springer, the OEM springs often have anything from 30mm to 60mm preload...I personally like at least 50mm preload on a spring and will often fit longer weaker springs to get it...it makes for a nicer shot cycle

One last thing while im rattling on, whats more efficient..IE what needs less or more spring....177, .22 or .25?

Well again it comes down to swept volume but also pellet weight. I sleeve HW80's to 25mm, i found when doing this the optimum stroke for a .22 is 70mm, for a .177 its 75mm (this for 250 to 260g pistons) but when i tried a 70mm piston with a .25 barrel...the power went down....but .25 is more efficient, or so they say
Fact is I had to go to 75mm to get the power back and im considering going to 79mm stroke to make life a bit easier for the spring.
So this brings up why stock 80's seem to do so well as .25's, well i still feel they have to heavy a piston and to much swept volume but that heavy 25cal pellet seems to soak it up and work well with the sub12 setup that feels very lazy in .22 and .177. Ultimately however I know from setting up an old HW85 with 280g piston and 70mm stoke the shot cycle in .25 can be super sweet using a lot less air.

One last point, barrel length also comes into this, shorter does not = better, i tested 8 inch upto 19inch on a .22 and .177 80, by far the best is 16inch (410mm) for sub 12, in the case of the 95 get the old style muzzle break gun and not the shorter version with the silencer...much better rifles

Alles anzeigen

Quelle: Weihrauchs Owner Forum

Das da bei dir in K2 nix rappelt, weiss ich. Durfte neulich auf dem Platz auch mit so einem Traum schiessen

Zitat von MarcKA

Bau mal auseinander und guck was kaputt ist.

Ich kenne so viele Gewehre mit 7,5J-V Mach-Kit bei denen nix rappelt.

Rappeln ist übertrieben, eher lustlos

@ Ladehemmung
Ok Wird Zeit, dass ich meine WBK bald hab

Zitat von Eisenschwein

Wicasa, wäre nicht 'ne Steyr oder ein anderer Presslüfter was für dich?

Hatte neulich viel Spass mit nem richtigen Preller

Ich finde Presslüfter faszinierend, mag aber eher einfache und robuste Technik. Wird wohl eher auf einen Karabiner hinauslaufen ;^)

Zitat von jaques gustou

Bin schon auf die Threads gespannt, die Du dann mit dem 16Joule V-Mach startest.

Wahrscheinlich nicht in diesem Forum

Es ging mir nicht darum, den Transferport zu verändern. Ich wollte, vielleicht ungeschickt, darauf hinweisen, dass ein Federkolbengewehr aufeinander abgestimmt ist oder sein sollte. Da unsere deutschen Druckluftwaffen überwiegend für den ausländischen Markt hergestellt werden und dort in der Regel höhere Mündungsenergien zulässig sind, gehe ich davon aus, dass diese Waffen darauf speziell optimiert sind. Der Einbau einer schwächeren Feder zerstört meiner Meinung nach die Abstimmung einer solchen Waffe.
Ein relativ harter Schlag auf den Hülsenboden, auch mit V-Mach Kit, ist dann die Folge.
Eigentlich wollte ich genau über diesen Punkt hier diskutieren. Der englische Artikel über die optimale Abstimmung einer Federkolbendruckluftwaffe hatte mich in meiner Annahme bestärkt.

Ok danke, dann muss ich wohl aufmachen und nachsehen