The Twin spring system (TSS)/ and tuning thread for TSS

[customcutter]

Subscribed, I love being a fly on the wall.  New to all this in the last 6 months so I've got a lot of learnin' to do.  Thanks for all the info that is so freely shared on this site...

[Hobbyman2007]

I'm presently using two springs in a BT65 . It did lower the cocking effort and lowered my ES . I don't however have the dual adjustments for preload and gap. This may just be the answer to heavy cocking effort . Because I'm not equipped with any machining tools and have been using existing end caps /power adjuster spring lengths this makes cocking harder than I like . I have a modified disco that I need to bump the power up to 60fpe from 20 fpe for some slugs . I'll be sure to try the two spring set up . Thanks for the heads up Travis .

[Buldawg76]

Travis
I will have to agree with Bob on the springs being counter wound would prevent any hang up or coil snagging from being able to occur. I know you say you have not experienced any that you know of but then also you cannot see the two springs in action inside the tube and hammer cavities that and the shot strings don't show any evidence of it being an issue. That does not mean its not occurring to some extent but not showing up in the strings.

The counter wound springs have been used in high performance engines for several decades now and either the inner spring is counter wound to the outer or  the inner is a flat ribbon style spring but still is counter wound to the outer and generally stiffer than the outer as well to control spring oscillations in high revving engines.

It would be real beneficial if there was a way to watch the springs in action when cocked and released to confirm or deny the issue of snagging or hanging up in use. Possibly cut a window in the tube to use a camera to film the real time action when being fired and then replay in slow motion to observe the interaction between inner and outer springs.

Just some thoughts in my head rolling around.

Mike

[CraigH]

The development work that comes from great hobbyists is truly remarkable.  I am always impressed.   

[lloyd-ss]

Travis, Great idea and it looks super simple, but a clever and novel approach. Addertooth's comment about Q-Spoiling does explain the physics behind why it works, and after all, all of our efforts can be defined by various physics and dynamics laws, principals, and equations.  There is sooooo much science in airguns!  It is very difficult to come up with an invention that is totally new, novel, and non-obvious, but coming up with a new "application" for an existing principal is where the real cleverness is required. The SSG and now the TS-FF are two very clever applications.  My hat is off to Bob and Travis.

Addertooth, your suggestion of fixing the hammer is good, but the devil is in the details. Making chambers within the hammer will be a lot more complicated than a pair of contra-wound springs. But with Tungsten's density of 2.2 times that of steel, the necessary amount might not be too great. I have a small can of Tungsten shavings that I have collected over the years but they seem to want to pack, rather than stay mobile. Individual drilled passages (like a Gatling gun) filled with light silicone oil and small lead shot?
The dead blow hammer sounds very clever and deserves investigation, but I don't want to side track Travis' thread, which is in itself very clever. 
Lloyd

[TF89]

Indeed all these ideas are great.  I tried the (home brew) SSG and was able to get good results, however adjusting was difficult and hard to get repeatably if I made any adjustments. The increase in effort to cock it convinced me to go back to the spring adjuster.  I'm sure most of that was/is because I  don't have a drill press and getting holes straight and center is hard to accomplish in hardened steel. 

All that to say, the two spring idea sounds like it is another cool and simple way to achieve some serious benefit.  Thank you for sharing your ideas Travis.

[oldpro]

Travis
I will have to agree with Bob on the springs being counter wound would prevent any hang up or coil snagging from being able to occur. I know you say you have not experienced any that you know of but then also you cannot see the two springs in action inside the tube and hammer cavities that and the shot strings don't show any evidence of it being an issue. That does not mean its not occurring to some extent but not showing up in the strings.

The counter wound springs have been used in high performance engines for several decades now and either the inner spring is counter wound to the outer or  the inner is a flat ribbon style spring but still is counter wound to the outer and generally stiffer than the outer as well to control spring oscillations in high revving engines.

It would be real beneficial if there was a way to watch the springs in action when cocked and released to confirm or deny the issue of snagging or hanging up in use. Possibly cut a window in the tube to use a camera to film the real time action when being fired and then replay in slow motion to observe the interaction between inner and outer springs.

Just some thoughts in my head rolling around.

Mike

I have no doubt Bobs correct about counter wound spring and I will source one today I was simply using what I had in the shop.

[FuzzyGrub]

Mike

Mike, I did many a compression outside of the tube.  Again, what I had was different amount of coils and spring guide.  With the springs shown in Travis pictures, the coil spacing looks near equal, so agree he may encounter more than I did.

[mobilehomer]

Possibly a sleeve between the two made from .005 shim stock? Just a thought.

[Hobbyman2007]

Well I spent the morning drilling , tapping and measuring. Made a crude version using a disco end cap .BUST ... there simply isn't enough room with the parts I have on hand . It may work with an aftermarket RVA used on the 22xx since it extends the room for a longer spring combination .its back to the drawing board for now.

[shorty]

Pretty cool Travis. If you have trouble sourcing anything for a specific wire diameter or spring size you can count on me.

1.8 efficiency is pretty darn good for just a spring swap. I have got over the 1.8 with the dual wire spring at power levels between 30fpe and 35fpe on my regulated 25 marauder and nearly 1.94 with the 22 at 20fpe.

I am sure combined with a light weight hammer you will see better results.

Since this marauder platform is at it's highest efficiency with a SSG or SSS I have been trying to get into the talon and condor platform using this same methodology. For some reason those guns have a very poor efficiency but out power just about anything.
I only say this because of the limiting factor of the 20" marauder barrel. Now put in a 24" or 26" barrel and efficiency will go over the 2.0 mark at the same power level.

I have a feeling that the talon or condor can nearly double their shot count with the proper spring. It appears as if they have the same problem were as there is a limited space for ID and OD and they still use pre-load to power up or decrease fill pressure to get a fairly stable shot string.

I just need to get one of those condors to start messing around with.

[FuzzyGrub]

What kind of ratio between the two springs?  lbs per inch  Are they about equal? or the inner 25% etc, lighter?  The 22 mrod that I did the double spring on is reg'ed, but could start experimenting on.  Ie both springs currently end just before hammer hits poppet with one of Scott's LW hammers.  But, as you would expect, cocking is rather hard.

[oldpro]

What kind of ratio between the two springs?  lbs per inch  Are they about equal? or the inner 25% etc, lighter?  The 22 mrod that I did the double spring on is reg'ed, but could start experimenting on.  Ie both springs currently end just before hammer hits poppet with one of Scott's LW hammers.  But, as you would expect, cocking is rather hard.

I moved the spring adjuster to the end of the spring cap like I did on the SSG this frees up a lot of space and lets the stock spring set slack with the hammer not touching the valve poppet then on the inside of the stock spring I put in a slightly stiffer spring and will be trying to find one thats counter wound. I then tension only the inner spring till I get my desired FPS but both can be adjusted as well as the striker in the hammer though I left mine fully retracted  to get the most spring travel.

[rsterne]

The only way to significantly reduce the cocking effort while incorporating a gap between a spring and the hammer is to use a longer, softer spring, and that requires more room to install it.... Many complain about an SSG being harder to cock and while that can be the case when you try and install one in the existing space inside a gun, that was never part of the original design.... A properly designed and installed SSG is easier to cock, not harder, but it does take up more length, which can require a different end cap, unless there is lots of spare room inside like in a QB....

I think Travis' idea needs to be researched, analyzed and developed, and may indeed prove to be an improvement over the SSG or SSS (short stiff spring).... Just looking at the mechanics, it uses two springs, one with a gap and the other with adjustable preload.... How hard it is to cock will depend on the ratio of forces of the two springs, and how well it attenuates hammer bounce will also depend on that.... The stiffer the outer spring is, the less hammer bounce, but the harder to cock at the end of the stroke, when the springs have the greatest compression.... Think of it as a blend of shorty's SSS and a conventional preloaded hammer spring.... It still has preload against the valve stem when uncocked (if I understand it correctly).... so it is better to think about it that way than as working like a SSG, which has no preload when uncocked.... The cocking effort will start off easier, but get harder towards the end of the stroke....

If the outer spring is extremely light, the inner one is doing most of the work, and the chance of hammer bounce will be little changed, it is working little different than a conventional preloaded (ie stock) spring.... It the outer spring is many times stiffer than the inner, then it is working more like a short stiff spring with a gap.... for a given hammer energy it will be harder to cock.... As the stiffness of the outer spring increases, the gun will get progressively harder to cock at the end of the stroke, for a given hammer energy.... Now if the installation creates more room for the springs, then the cocking force can be reduced, just as would happen with an SSG....

Dead blow hammers are interesting, and I understand have been tried.... They work by causing a second, slightly delayed (a matter of microseconds), internal impact between the inner weight and the rebounding hammer head.... and are intended to work in an elastic collision such as steel on steel.... The bounce in airgun hammers is not an elastic collision, it is created when energy is stored in the open poppet, and returned to the hammer as the poppet closes.... This happens over a much longer time scale than a single hammer strike on a rigid object.... The poppet is actually "pushing back" on the hammer, it is not a simple matter of the hammer rebounding elastically from a rigid stem.... I think that difference may cause a dead blow hammer to react quite differently in an airgun than you might expect....

Using a shim between the two springs seems simple on the face of it.... but where does that (tubular) shim go when the springs are compressed?....

Travis, you state you gained room compared to your SSG installation.... Did you also gain length compared to a stock MRod installation?....

Bob

[FuzzyGrub]

What kind of ratio between the two springs?  lbs per inch  Are they about equal? or the inner 25% etc, lighter?  The 22 mrod that I did the double spring on is reg'ed, but could start experimenting on.  Ie both springs currently end just before hammer hits poppet with one of Scott's LW hammers.  But, as you would expect, cocking is rather hard.

I moved the spring adjuster to the end of the spring cap like I did on the SSG this frees up a lot of space and lets the stock spring set slack with the hammer not touching the valve poppet then on the inside of the stock spring I put in a slightly stiffer spring and will be trying to find one thats counter wound. I then tension only the inner spring till I get my desired FPS but both can be adjusted as well as the striker in the hammer though I left mine fully retracted  to get the most spring travel.

Travis, that is what I did on that gun.  Drilled out the endcap and threaded all the way through, then drill relief so the larger spring can move back further. 

[shorty]

Dual wire spring as Addertooth has described instead of short stiff spring. There is something there too.

I could never find a conventional spring at the dimensions needed to simulate it. Except for a .057" PH material milled ( flattened ) to a 3:1 aspect ratio ( yes flat wire or ribbon wire) wound at 7 active turns. Good ES but very hard to cock.

IMO, if gap is the same (SSG or TS) for negative preload - then cocking force should be the same for given power level. Too me, it's not hammer bounce that we are eliminating, it is pressure against the valve stem at compression and extension that allows the excess dwell (not rebounding hammer bounce).

Elastic and in-elastic collision do occur and change everything. This is where the control comes into play which I have never been able to prove.

[shorty]

The biggest issue I see with Travis's set up is blocking the air path from the hammer spring adjuster. This changes everything.

Scott introduced me to this and yes, you can change almost 50fps if you cover the hole at the hammer spring adjuster with your thumb.

Funny how things work but, I am glad to see the changes in systems.

[oldpro]

The biggest issue I see with Travis's set up is blocking the air path from the hammer spring adjuster. This changes everything.

Scott introduced me to this and yes, you can change almost 50fps if you cover the hole at the hammer spring adjuster with your thumb.

Funny how things work but, I am glad to see the changes in systems.

Its vented ill show pics in a few

[oldpro]

Ok I changed out the springs and went to softer middle spring and counter wound with slightly stiffer than stock outside spring. Still easy as pie to cock and here's my first run with this set up with modified stock valve and Nylon MDS hammer.

[oldpro]

I couldnt figure out how to get data from phone app to post without sending to myself and snaping screen shots. Anyone know a better way??? On a iphone 6s