dual wire hammer spring (video uploaded)

[shorty]

So,
I have not really had any comments or requests about my dual wire hammer spring except for RDsail and Moorepower so I figured I would post a small video (you may call it a little review).

4 pellets grains, HS 0 to 8, HS5 and VAS wide open. I put the HT to 5 to simulate a stock gen2 .22 cal. If I make the HT at 0, the .22  25.39 jsb will hit 50 fpe with the little garage mods I did to the valve and Transfer sleeve (see DIY valve post). The spring is the kicker not the valve or tp mods.

The reason for the HS0 was to show that even a heavily modded marauder can be tamed with the turn of a wrench while still being a beast.

Starting pressure was 3000psi or 3100psi. I never over charge the gun.



If you want one, you know where to find me.

[Monkeydad1969]

Ok Shorty...explain and are there any dual wire springs for the Disco?  Nice results.

Joe

[shorty]

I guess I can make them for a disco but I don't have a disco or disco spring to copy and or test out. I guess I can make any kind of spring with the right wire and mandrel.

[daveb50]

I would be interested in a dual wire Disco spring also.

[Monkeydad1969]

Here you go, got this off an older thread:

diameter: .289"
overall length: 2.252"
wire diameter: .035"
# coils: 15


I can send you a spring if need be...I nominate myself to test a dual wire Disco hammer spring...

Joe

[shorty]

Monkey and Dave,
I can see this being a different thread since I am trying to get a few people to go and try out my marauder spring but, If making a disco spring helps in my quest to fund for a lathe, then so be it.

On with the disco spring ( I am in ).
I can work off those dimensions to make that spring. I have a couple comments and more questions.

Comments:
Holy moly, is that O/D of that spring really that size ?

Questions:
Are you guys running an inside spring guide ? If so, what is the diameter of it ?
What is the actual hammer travel ? How for do you have to cock the gun ? (I am looking for actual compression of spring when cocked)
What is the actual distance from hammer spring seat to inside of hammer when at rest (not cocked)? ( I am looking for "true" free length of spring).

More comments:
When running the spring calculator the stock spring should be approximately a 8.77 lb spring at free length. I have some .047" PH material that I use for the marauder and when I punch those numbers in to the calculator (single wire) we should see 31lbs at free length.

That being said,
A dual wire spring would not work due to it would yield over 50 lbs of force ( I think). So, I have an idea.

I have a feeling that there is preload on this stock spring at 2.25 inches long.If I make the spring with approximately 8 to 10 active coils and then close wind 4 turns on both side of the spring ( something like that ) this should allow for a spring that is 2.25 inches long that can be trimmed back on the non-active coils to allow for tuning (0 to negative preload) which should still yield a much higher compression force than stock. I've observed ( with the help of some others) that the negative preload at the same compression force always increases shot count (well in my case with the marauder).

Tell me what you think. I'll start looking for a mandrel. By the way, my wife is starting to get perturbed that I keep sending these springs out free. She's the shipping and handling girl. So we would have to work something out.

[Monkeydad1969]

Here you go, got this off an older thread:

diameter: .289"
overall length: 2.252"
wire diameter: .035"
# coils: 15


I can send you a spring if need be...I nominate myself to test a dual wire Disco hammer spring...

Joe

Hey shorty,

I pulled a Disco spring and these are better measurements---again I pulled the other dimensions off an old thread:

diameter: .294"
overall length: 1.75"
wire diameter: .035"
# coils: 15
inner diameter:  .218"

I don't know the other measurements.  I will shoot Rsterne a PM and see if he will chime in.  He is in the know a whole heck of more than I.

Joe

[rsterne]

There are tons of springs available that will fit the Disco.... If you go too heavy, you can break the handle on the bolt because the gun gets too hard to cock.... The solution is to cut a slot into the side of the receiver, and make a custom hammer with side cocking handle.... Rear cockers have been done, but I find them awkward to use, but you can add weight to the cocking knob.... A stock Disco hammer travel is only 0.58".... It is relative easy to get 0.70", more difficult to get more (many changes required).... The hole in the hammer and rear cap is 5/16", so the maximum spring OD is 0.30".... There is no internal guide on a stock Disco....

There is no magic about hammer springs.... Springs are a very simple device for storing energy.... They have a spring rate, measured in lb./in., a free length, a compressed length (when the coils are touching), and a maximum travel (free length - compressed length).... If they are preloaded, they have an initial force, and when compressed, they have a final force.... The energy released is the travel times the average force over that travel.... Yes, you can make progressive springs, and have a different "feel" during the cocking stroke, but the basic Physics remains unchanged.... One of my biggest peeves is when somebody calls a spring a "10#" or "15#" spring when they are talking about spring rate, which is measured in lb./in....

Bob

[Monkeydad1969]

Thank you, Bob.

Joe

[shorty]

That's exactly the information I was looking for. Thanks Rstrene. Your are absolutely correct about Lbs/in vs calling spring by # only. As for me, I think there is a lot of magic in springs.

So here is the first cut. I can't believe how small this spring is compared to a stock marauder spring. .196" mandrel using .0475" PH material. 10 active coils and 3 non active coils (on each side). Total length 1.5 inches. O/D .29"
Spring rate: 19.98 Lbs/inch

[shorty]

I think this is the closest I am going to get.

2 inch length
.0475" PH wire
12 active coils and 2 on each side non active (for tuning purposes)
.29" OD
Spring rate: 16.6 lbs/in

I think the .04" wire spring at 1.75" has a 13.9lbs/in spring rate.

[rsterne]

Had a look at the video.... Not too difficult to do at 3000 psi with a short, stiff spring.... The key is to be able to change the preload (in lbs.) over a wide range.... I have several springs that can do the same thing in different PCPs.... I don't find it a particularly useful way of tuning, unless you want to tune for a different pressure range....

What is not shown is what happens over a string.... With maximum preload, the strings will tend towards first shot fastest and then declining.... With no preload, the valve is starting out nearly valve locked (so of course the velocity is low), and the velocity will increase as the pressure drops.... a LOT.... Showing details of the shot strings, and the pressure range over which you can produce about a 4% ES, is much more important.... Statistics are like a Bikini.... what they reveal is enticing, but what they conceal is vital....

I like the idea of having some close-wound coils at the end on the Disco spring so that it can be cut to length instead of needing an adjuster.... but personally would prefer using an adjuster so that if I change my mind I have that option.... Stripping apart the back of the gun to change the tune is not that much fun, IMO....

Bob

[shorty]

Here's the stat's for the marauder spring. They were done when I did the valve mods. Yup you are right again about using this spring. You tune the gun to fill pressue and hammer spring alone. Possibly fine tuning with the HT.

[rsterne]

As I said, the velocity at HS 0 increased a lot as the pressure dropped from 3000 psi.... according to your data from ~330 fps to ~885 fps (at ~ 1700 psi?).... Don't get me wrong, I'm not saying you don't have a good spring design.... I just don't think much of the marketing approach....

Bob

[shorty]

My latest tune is for 12 to 15 fpe for 140 shots with a fill pressure of 2000psi down to 1000psi.

The dual wire spring is a little bit strange when tuning.There are 2 ways to achieve 0 preload.

1 way is to have HT at 0 and HS at 0, cock the bolt back and leave it back. Turn the HS CW until the bolt stops moving forward. The  other way is to leave HS at 0 and adjust HT from 0 to 8 with 1 turn increments until the highest fps is achieved.

What kind of shot string would you be looking for? I have about 2 hrs to play right now. I have tins of 14.3,18.13, and 25.39's.

[rsterne]

The strings advertised in your .pdf file are great.... especially the efficiency achieved.... I'm not "looking" for anything, as I don't have an MRod.... I was asked to comment on the video, and I did so....

Bob

[shorty]

Your right, Iam terrible at selling something

Iam not understanding.

The video was ( shots taken in this order )
3000psi
HS0
25.39
21.4
18.13
14.3
Then adjusted HS to 8
25.39
21.4
18.13
14.3
25.39
Ending pressure: maybe 2900psi. Couldn't tell, the gauge hardly moved.

No shot strings where performed. Wanted to show that this spring is capable of the entire range of a spring less than stock and more the stock can be used in the gun without changing springs. All in one spring.

[shorty]

I see a lot of people wanting 6,10,12,15,and 17 lb/in springs. Why bother buying all these springs when 1 will do the same. And actually can hit 20+lbs/inch. All with out changing your spring out. Just adjusting the HS the dual wire spring can run the whole range of those 5 springs.

[rsterne]

Your HS 0 shot with the 14.3 gr. was 331.7 fps.... The 70 shot string you shot with the 14.3 gr at HS 0 peaked at 885.2 fps.... Who knows how many shots it would have taken to drop from 3000 psi down to where 2200 where you started that string.... It doesn't matter, because nobody would ever do that.... That was my point, that the gun doesn't really drop down to 332 fps in terms of usable power from 1080 fps (which the 14.3 gr. did in the video at maximum preload), just from reducing the preload.... At 3000 psi, yes.... but not in terms of practical usage.... There is a difference between "capable of" and "usable range of power", and I think marketing using the former is insulting to the members here.... but that's just my opinion....

I agree that you don't need a bunch of different springs to achieve different tunes.... Any short, stiff spring can do that.... However it is critical that guys realize that when you drastically back off on the hammer spring you also need to reduce the fill pressure.... Your video "implies" otherwise.... that you can detune from 50 FPE to 3 FPE with just reducing preload.... While that is "technically" correct, anyone expecting to have a useful number of consistent shots at 3 FPE by just adjusting the preload would be disappointed.... That is what I meant by "questionable marketing"....

Bob

[shorty]

My intentions are not to insult anyone. I am just having a hard time figuring out what I have to show for the capabilities that some may want.

I'll run 2 strings at 20 shots to see what the ES% would be for 25.39 JSB's. One at just below max and one around 10fpe at 3000 psi. I hope this will clear up some of my confusion.