Tuning Thrust bearing

[boscoebrea]

As spring gun tuner,do you tune each springer differenty.meaning if you have tuned a lot of say R-9s, do you just do R-9 s the same way,or do you tune each springer as if were one of a kind?
Like when I install a JM tune kit,a certain kit can fit all models of a specified tune kit.
I guess what I am getting at; my JM Tune kit will make a noticable difference,but a custom tune will make my springer the best it can be. I could ask how much better .and a reply like how mush is it worth to me?

 

[Mycapt65]

To take this a bit deeper ....
It is not the rotation of spring when it can do so freely threw out its stroke travel, it just winds up and unwinds freely .... IT IS WHEN the friction at either end of spring allows rotational tension to build up due to a LACK OF rotation that at some point breaks free and violently corrects this stored torque energy to release the tension that it effects accuracy. Newtons 3rd law of physics once more being of equal & opposing reaction. Spring releases energy in rotation one direction, it imposes reaction forces the other direction.
Now mass of the containment vessel ( The gun itself ) absorbs a very large part of this ... but it there none the less if / when a spring is bound up held from free rotation and breaks free suddenly.

Physics 101 ...

I will agree that smoothing the little rotation that's there is a prudent thing and will help smooth the guns overall fuction. But springs don't really wind up as much as people here think. Do my experiment yourself and you'll see. The amount of rotation at the spring ends is very minimal.

As an auto mechanic and railroad machinist I've worked with coil springs from automotive engine valves springs to giant coil springs that holds trains up. Trust me airgun people put waaay too much emphasis on the effects of spring rotation. Nothing trick or fancy is needed to negate it. A delrin top hat and you're done.

 

[Bedrock Bob]

When I re-assembled my HW97k the guide had pretty good friction on the breech. It turned the spring when I turned the plug. The friction against the tophat/slip washer/piston was a lot more than I'd expected. It took some torque to turn it under spring tension. It will take much more when its cocked.

No doubt there is still some twisting force transmitted to the rifle. The spring has to work against a lot of friction to unwind even with slip washers and delrin interfaces. It moves but it dosent move "freely". The spring is pushing against the guides when cocking and dragging them when it unwinds.

 

[A.G.R]

As spring gun tuner,do you tune each springer differenty.meaning if you have tuned a lot of say R-9s, do you just do R-9 s the same way,or do you tune each springer as if were one of a kind?
Like when I install a JM tune kit,a certain kit can fit all models of a specified tune kit.
I guess what I am getting at; my JM Tune kit will make a noticable difference,but a custom tune will make my springer the best it can be. I could ask how much better .and a reply like how mush is it worth to me?

Kits are the beginning of the tune. Not every gun responds to the kit the same. That’s where magic happens. Kit dropping can help but it’s 50% of the total output and performance.

 

[Motorhead]

When I re-assembled my HW97k the guide had pretty good friction on the breech. It turned the spring when I turned the plug. The friction against the tophat/slip washer/piston was a lot more than I'd expected. It took some torque to turn it under spring tension. It will take much more when its cocked.

No doubt there is still some twisting force transmitted to the rifle. The spring has to work against a lot of friction to unwind even with slip washers and delrin interfaces. It moves but it dosent move "freely". The spring is pushing against the guides when cocking and dragging them when it unwinds.

Ideally ... Think Chinese finger trap.
As you cock rifle the spring coils open up slightly under compression and drag is no longer present on guide. When discharging the same having free motion just until piston is about to bottom out the coils come back into contact with guide and put on the brakes lets say stopping any secondary spring shuttering / vibration .... Perfect !!

 

[Bedrock Bob]

Ideally ... Think Chinese finger trap.
As you cock rifle the spring coils open up slightly under compression and drag is no longer present on guide. When discharging the same having free motion just until piston is about to bottom out the coils come back into contact with guide and put on the brakes lets say stopping any secondary spring shuttering / vibration .... Perfect !!

Yes. But I was talking about friction at the end of the spring resisting rotation. As those coils open up the spring rotates...or tries to.

The spring opens up on the guide shaft when it compresses. But the compression increases friction at the top hat and guide base that resists rotation. So some of that moment is transmitted to the rifle as "twist".

 

[Motorhead]

Yes. But I was talking about friction at the end of the spring resisting rotation. As those coils open up the spring rotates...or tries to.

The spring opens up on the guide shaft when it compresses. But the compression increases friction at the top hat and guide that resists rotation. So some of that moment is transmitted to the rifle as "twist".

If spring is allowed to rotate the entire time the last bit of stroke where spring grabs onto guide any torque present has the other end rotate.
Ideally and in most designs the spring can rotate at both ends so stoppage at one end ( Guide as your stating ) it still is a non issue.

If the spring was mechanically anchored at both ends there would be no applied torque either, as the containment is still within the same frame work of the gun.
Read post 36 again as to HOW & WHY the Torque of a rotation bound up tensioned spring can create motion.

 

[Bedrock Bob]

If spring is allowed to rotate the entire time the last bit of stroke where spring grabs onto guide any torque present has the other end rotate.
Ideally and in most designs the spring can rotate at both ends so stoppage at one end ( Guide as your stating ) it still is a non issue.

If the spring was mechanically anchored at both ends there would be no applied torque either, as the containment is still within the same frame work of the gun.
Read post 36 again as to HOW & WHY the Torque of a rotation bound up tensioned spring can create motion.

The spring can rotate at both ends. But it takes force to rotate it. It's not free spinning. Under preload it takes quite a bit of torque to rotate.

I get exactly what you are saying. But the spring isn't "free" at both ends. Yes it moves. But it takes force to move it. That force is transmitted to the rifle.

The kit I used has delrin "slip washers" at both ends of the spring. You can grease those up good and stuff the spring in there and things don't spin easily. It takes some torque to get the tophat to spin in the piston. It will move. It will not move "freely" under compression. There is friction there.

When you cock it it's going to take more force to spin it. When you shoot and the spring rotates it's going to take some force to do that. That force is transmitted to the rifle.

It's not about the spring grabbing the guide shaft. It's about the spring rotating at either end. The spring under preload takes quite a bit of rotational force to turn the tophat in the piston on a delrin slip washer. And the same exact thing at the guide end. Even though both ends are "free" to spin they don't spin "freely". It takes some torque.

 

[Motorhead]

Any thing under tension is seldom freely moved.
Bob, don't over think it.

My explanations were strictly FYI educational .... no need to reinvent the wheel

 

[JamieUK]

The spring can rotate at both ends. But it takes force to rotate it. It's not free spinning. Under preload it takes quite a bit of torque to rotate.

I get exactly what you are saying. But the spring isn't "free" at both ends. Yes it moves. But it takes force to move it. That force is transmitted to the rifle.

The kit I used has delrin "slip washers" at both ends of the spring. You can grease those up good and stuff the spring in there and things don't spin easily. It takes some torque to get the tophat to spin in the piston. It will move. It will not move "freely" under compression. There is friction there.

When you cock it it's going to take more force to spin it. When you shoot and the spring rotates it's going to take some force to do that. That force is transmitted to the rifle.

It's not about the spring grabbing the guide shaft. It's about the spring rotating at either end. The spring under preload takes quite a bit of rotational force to turn the tophat in the piston on a delrin slip washer. And the same exact thing at the guide end. Even though both ends are "free" to spin they don't spin "freely". It takes some torque.

I believe you are correct. Slip washers/ correct polishing and lubing limit the transmission (and what we can feel) but it still happens.....just not enough to notice anymore, and as motorhead says, doesn't really need over thinking.

Getting down to very small details though....I think seal fit/ design, friction, preload and piston mass might play a role here too (I mentioned seal fit/ resistance earlier, but was partially dismissed). I built a test rig a while back (a basic monotube layout with a crosman barrel running centrally through the cylinder, a twin oring sealed piston, reverse firing, basically allowing me to adjust the barrel in and out from the probe loading breech so I could test a different transfer port layout). This is how the components looked within the comp tube-

(This pic was pre cutting the spring, wasn't running 100mm preload!)

The delrin guide rides against phosphor bronze, the oilon top hat rides against it too. The piston nose was also phosphor bronze. It had slip washers, polished 90deg spring ends and a free rotating piston.

Due to it having a small ish cylinder bore (23mm) and long stroke/ light piston, it was lubed with krytox to prevent/ limit dieseling. The orings ran the absolute minium of crush.

All in all, I felt I'd done everything I could (within my limits) to promote free movement, yet it torqued, and worse than any action I've felt before. I could only really summise 3 things that would cause it (not fact, just a best guess).

1- the twin Oring piston seals, due to the nature of how they work, had two points at which to 'grab' at the action....the cylinder ID (like any other seal) but also onto the OD of the barrel.

2- high preload. I was also testing/ looking for high efficiency from this rig, which meant running a light spring/ high ish preload. This of course translated into more initial 'stored' spring twist in the cocking phase.

3- piston mass. I started off with a very light (90gr) piston, and progressively added weight (in steps whilst adjusting transfer port). 'I guess' the lighter a piston is, the less fight it can put up against the initial spring torque, so as the piston rotates with the spring and the seal/ seals grab at the action, more is transfered out.

No facts or statements implied with this, and any torque transferred was exaggerated due to it being held in hand (no stock). All I can say for sure though is as I progressively added weight to the piston, the torque reduced. It was the opposite of what I thought would happen.

Im no scientist however and might be on the wrong track alltogether (would welcome PM's from anyone who may know better)
So...make of this what you will.....

 

[beerthief]

When teaching mechanics around spring tech a simple question asked is WHAT IS A COIL SPRING ? .... in 4 words or less
Answer ... "Radially Wound Torsion Bar"
How do torsion bars work ? ... They rotate down there length storing and compressing motion energy wanting to return to a relaxed position.
How does a coil spring work ? ... They rotate the wire there wound from down there entire free coil length when either in compression or expansion wanting to return to a relaxed position.

Sadly Steel springs fatigue and ultimately fail as the motion at the molecular binding level of the steel breaks down just as if taking a piece of metal working it back-n-forth it work hardens and finally fractures.
Spring steels while designed for the task, fail is a similar fashion due to fatigue caused by motion over over and over again.

* VIBRATION after the shot cycle is still working the steel !!!! and why twangy vibrating spring piston air guns are harder on springs than tuned ones on fitted guides and spring thrust washers that allow free motion. As a springs violent torque rotation if present is a secondary vibration same as post shot spring twang .... Both add additional wear & tear to the spring steel.

Just sharing on this rainy day ...

How did you know it is raining here ? 3/31/25 07:19 Holy crap your psychic . thanks for the read with AM coffee .

 

[beerthief]

Using Derlin top hat or SS washers / grease is just a simpler thrust bearing .

Guess i will just have to get my Diana Giss rifle rebuilt .

 

[Bedrock Bob]

I believe you are correct. Slip washers/ correct polishing and lubing limit the transmission (and what we can feel) but it still happens.....just not enough to notice anymore, and as motorhead says, doesn't really need over thinking.

Getting down to very small details though....I think seal fit/ design, friction, preload and piston mass might play a role here too (I mentioned seal fit/ resistance earlier, but was partially dismissed). I built a test rig a while back (a basic monotube layout with a crosman barrel running centrally through the cylinder, a twin oring sealed piston, reverse firing, basically allowing me to adjust the barrel in and out from the probe loading breech so I could test a different transfer port layout). This is how the components looked within the comp tube-

View attachment 551616

(This pic was pre cutting the spring, wasn't running 100mm preload!)

The delrin guide rides against phosphor bronze, the oilon top hat rides against it too. The piston nose was also phosphor bronze. It had slip washers, polished 90deg spring ends and a free rotating piston.

Due to it having a small ish cylinder bore (23mm) and long stroke/ light piston, it was lubed with krytox to prevent/ limit dieseling. The orings ran the absolute minium of crush.

All in all, I felt I'd done everything I could (within my limits) to promote free movement, yet it torqued, and worse than any action I've felt before. I could only really summise 3 things that would cause it (not fact, just a best guess).

1- the twin Oring piston seals, due to the nature of how they work, had two points at which to 'grab' at the action....the cylinder ID (like any other seal) but also onto the OD of the barrel.

2- high preload. I was also testing/ looking for high efficiency from this rig, which meant running a light spring/ high ish preload. This of course translated into more initial 'stored' spring twist in the cocking phase.

3- piston mass. I started off with a very light (90gr) piston, and progressively added weight (in steps whilst adjusting transfer port). 'I guess' the lighter a piston is, the less fight it can put up against the initial spring torque, so as the piston rotates with the spring and the seal/ seals grab at the action, more is transfered out.

No facts or statements implied with this, and any torque transferred was exaggerated due to it being held in hand (no stock). All I can say for sure though is as I progressively added weight to the piston, the torque reduced. It was the opposite of what I thought would happen.

Im no scientist however and might be on the wrong track alltogether (would welcome PM's from anyone who may know better)
So...make of this what you will.....

Seems to me if the piston rotated with the spring there would be more spinning mass=torque. The piston is at least the weight of the spring. So in my addled brain the twist would increase.

Yes, the amount of spring torque is dependant on the resistance to it "twisting". So the more torque it takes to turn the spring the more that is transmitted to the gun.

I don't think pointing that out is overthinking it. It is what it is. Even if it's not noticeable in the shot cycle. I'm not suggesting "re inventing the wheel" at all. I'm simply pointing out that no matter what guides or slip washers you use there is still some torque. Probably a lot more than most guys think.

I know I was surprised at how much torque it took to spin the tophat on that slip washer. I had assumed the torque would be minimal. I had pondered that question when rebuilding my break barrels. But the way they go together the friction is not obvious. When I did the 97 the design of the plug allowed me to feel how much torque there was. I was surprised how much.

Even with delrin giblets and plenty of moly the spring is going to fight to unwind. It may make no difference in the shot cycle at all. But then again it might. You would have to re invent the wheel to find out.

I thought since we were discussing friction at the spring/piston interface my observations might spur some discussion. I don't think I am alone in believing the kits eliminated spring torque. I don't think I'm alone being surprised that they don't. At least not to the degree I had visualized.

 

[A.G.R]

Seems to me if the piston rotated with the spring there would be more spinning mass=torque. The piston is at least the weight of the spring. So in my addled brain the twist would increase.

Yes, the amount of spring torque is dependant on the resistance to it "twisting". So the more torque it takes to turn the spring the more that is transmitted to the gun.

I don't think pointing that out is overthinking it. It is what it is. Even if it's not noticeable in the shot cycle. I'm not suggesting "re inventing the wheel" at all. I'm simply pointing out that no matter what guides or slip washers you use there is still some torque. Probably a lot more than most guys think.

I know I was surprised at how much torque it took to spin the tophat on that slip washer. I had assumed the torque would be minimal. I had pondered that question when rebuilding my break barrels. But the way they go together the friction is not obvious. When I did the 97 the design of the plug allowed me to feel how much torque there was. I was surprised how much.

Even with delrin giblets and plenty of moly the spring is going to fight to unwind. It may make no difference in the shot cycle at all. But then again it might. You would have to re invent the wheel to find out.

I thought since we were discussing friction at the spring/piston interface my observations might spur some discussion. I don't think I am alone in believing the kits eliminated spring torque. I don't think I'm alone being surprised that they don't. At least not to the degree I had visualized.

as you stated. NO MATER WHAT YOU DO

THE SPRING IS GONNA TWIST. ..

The spring is 25% of the total tune in a build. Kit dropping will tame a factory gun but it’s gonna twist. Just more controlled. The back pressure of the piston and the seal as well as port size can control the rate of it spinning or accelerating and rebounding. That’s where magic is made. Drop a kit get 50% of what actually can be done to the gun.
not For power either.