GTA
All Springer/NP/PCP Air Gun Discussion General => Air Gun Gate => Topic started by: Ronno6 on September 22, 2022, 12:57:43 PM
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It appears that replacing the Reaxix gas rem in my Umarex Octane is not currently possible.
I need to understand the design considerations of converting to a coil spring powerplant.
The Reaxis ram is 18mm OD and the fully extended length is 330mm.
The rod is 150mm long,and has an available stroke length of 137mm.
When installed, the ran had very minimal preload from what I can tell.
The ID of the spring tube (then wall metal tube inside the piston) is a tad over 20mm.
I understand that a coil spring will increase in OD as it is compressed.
If I consider using a coil spring, how would I translate these dimensions??
I would think that a coil would require about 3" of preload in round numbers, without giving consideration to the spring rate and actual preload required.
That's gettng on up to a spring of just over 400mm in free length.
I am not finding that anywhere.....
So, I have to believe that a combination of spring length and a suitable spacer to make up the difference is required?
As there is so much that I do not (currently) know, what other considerations will factor in??
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If I cannot find a single spring long enough, can I stack 2 shorter ones?
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An engineer at Suspa offered to make one custom for $105.00.......
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An engineer at Suspa offered to make one custom for $105.00.......
I hope he understands that your application needs the gas spring to be undamped.
How much to have a custom coil spring made? McMaster has a wide range of parts and materials, but often at double the best price. They can ship you a custom made steel spring, but probably at twice the price of that gas spring - assuming the gas spring meets your requirements: https://www.mcmaster.com/coil-springs/spring-type~compression/made-to-order-compression-springs/ (https://www.mcmaster.com/coil-springs/spring-type~compression/made-to-order-compression-springs/)
I have to believe that there is coil spring stock that can be cut to your required length. This link takes you to 3/4" OD spring stock (because that seems most common for airgun steel springs, near the 18 mm gas spring body you mentioned). You can step back and select whatever OD you want from the dropdown menu: https://www.mcmaster.com/spring-stock/od~3-4/ (https://www.mcmaster.com/spring-stock/od~3-4/)
You should know the installed and compressed length (and the spring rate you are trying to achieve); so there are a few ways to approach this: https://www.mcmaster.com/spring-stock/maximum-load~range~~-5637010442429/ (https://www.mcmaster.com/spring-stock/maximum-load~range~~-5637010442429/)
It may be that the ID is the most important diameter to fit (a non-existent guide?). Or the OD needs to be a slip fit in the piston ID when the spring is compressed. What spring OD/ID/wire diameter combinations are available may dictate your choices. A spring manufacturer no doubt would have more options.
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As a mechanical buyer for 25+ years I have purchased many made-to-print springs of many different types.
I am (well, used to be) familiar with spring design parameters.
Material is something which I have not seen mentioned.
Music wire?
Chrome vanadium?
Chrome silicon?
Valve spring wire?
I used to know people at many spring manufacturers, but, as I retired 18 years ago, they are probably gone now...
Yes, the app engineer and I discussed the need for no internal damping.....that feature would preclude the use of any of their stock gas springs.
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Possibly helpful links:
https://www.pyramydair.com/blog/2008/10/hw-55-tyrolean-part-5-how-to-measure-a-spring/ (https://www.pyramydair.com/blog/2008/10/hw-55-tyrolean-part-5-how-to-measure-a-spring/)
https://www.customairseals.com/air-rifle-spring-cutting-procedure/ (https://www.customairseals.com/air-rifle-spring-cutting-procedure/)
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Perhaps duplicating the original gas spring is the simplest, because it eliminates the "missing guide" problem that a steel spring would introduce.
I assume that you contacted Umarex and Pyramyd Air for a replacement gas spring. It certainly sounds like you know where to look.
You could contact Hector Medina via PM. He could advise you on spring material selection. And on sources for complete springs, or about spring stock that can be cut to length.
https://www.gatewaytoairguns.org/GTA/index.php?action=profile;u=21540 (https://www.gatewaytoairguns.org/GTA/index.php?action=profile;u=21540)
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Possibly helpful links:
https://www.pyramydair.com/blog/2008/10/hw-55-tyrolean-part-5-how-to-measure-a-spring/ (https://www.pyramydair.com/blog/2008/10/hw-55-tyrolean-part-5-how-to-measure-a-spring/)
https://www.customairseals.com/air-rifle-spring-cutting-procedure/ (https://www.customairseals.com/air-rifle-spring-cutting-procedure/)
Excellent!
Thanks...
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Apart from Hector Medina, contact Ron (Bayman) about spring material selection:
https://www.gatewaytoairguns.org/GTA/index.php?action=profile;u=21540 (https://www.gatewaytoairguns.org/GTA/index.php?action=profile;u=21540)
https://www.gatewaytoairguns.org/GTA/index.php?action=profile;u=33840 (https://www.gatewaytoairguns.org/GTA/index.php?action=profile;u=33840)
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Apart from Hector Medina, contact Ron (Bayman) about spring material selection:
https://www.gatewaytoairguns.org/GTA/index.php?action=profile;u=21540 (https://www.gatewaytoairguns.org/GTA/index.php?action=profile;u=21540)
https://www.gatewaytoairguns.org/GTA/index.php?action=profile;u=33840 (https://www.gatewaytoairguns.org/GTA/index.php?action=profile;u=33840)
Will do...
Thanks!
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Using this 3/4" OD stock,
my rough calculations arrive at a total spring force of 72# when cocked.
Sounds like it is almost appropriate ??
What I don't see is the c-c coil spacing....
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Ron,
I think 72 lb cocked is rather low. I would expect perhaps triple that, depending on airgun power. What is the rated power of your Octane?
If your rated power is 20 FPE, the energy in the cocked spring is typically 3 times that. 60 FPE stored over a 4" piston stroke would indicated 60 x 3 = 180 lb average force. So, depending on the spring rate, the force at full cock could be much more than 180 lb. For a gas spring, the force at the start and end of the stroke are much closer, than for the typical steel spring.
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Ron,
I think 72 lb cocked is rather low. I would expect perhaps triple that, depending on airgun power. What is the rated power of your Octane?
If your rated power is 20 FPE, the energy in the cocked spring is typically 3 times that. 60 FPE stored over a 4" piston stroke would indicated 60 x 3 = 180 lb average force. So, depending on the spring rate, the force at full cock could be much more than 180 lb. For a gas spring, the force at the start and end of the stroke are much closer, than for the typical steel spring.
A cursory search gave me a fpe of 18.32
The McMaster 3/4" OD x 36" coil was 3.8lb/in if I recall..
Shortening the 36" coil to 15" would bring the rate to 9.12lb/in.
With a 2.5" preload and 5.43" stroke force would be the 72lb/in.
One Vortek spring suggested has a rate of 48lb/in.....quite a difference........
More stuff to learn!
Max stroke length of the gas piston is 5.43"
I do not know how much if that is actually utilized in the rifle.
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From nondeliberate memory; round numbers for a 15 FPE springer would be 100 lb preload and 200 lb cocked.
That means that for a 4" stroke, the spring rate would be 25 lb per inch. Proportionally more for a shorter stroke. A 3" stroke would suggest a 33.3 lb per inch rate.
I sent a PM to Hector and Ron. It is up to them to weigh in, if they have time and inclination.
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Thanks for the invite Peter. This stuff is out of my wheel house. I'm not familiar with the gun and I can't say for sure but the avaliable stroke and spring length sound very long to me. I'm wondering if part of both those lengths was just space taken up by the ram body and not actually used stroke. That space perhaps could be taken up by a dummy plug and a more readily available shorter spring used.
I'm just spit balling here. Without seeing the original guts of what were working with here I'm probably of little use. I do wonder if the gun itself is worth re-engineering it. That can only be determined by the owner.
Be well
Ron
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Thanks Ron
I agree that the original gas spring travel is not the same as the actual piston stroke.
Do you have an opinion about steel spring material choices - listed above by the OP? Quoted below:
Music wire?
Chrome vanadium?
Chrome silicon?
Valve spring wire?
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To measure actual effective stroke length, the piston position when held by the sear and piston fully forward need to be measured.
Yes, the piston must be able to over travel far enough back on cocking to engage the sear. So, that extra movement must not be impeded with a new spring, steel or gas. If there is an auto-safety, that travel needs to be considered as well.
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Thanks for the invite Peter. This stuff is out of my wheel house. I'm not familiar with the gun and I can't say for sure but the avaliable stroke and spring length sound very long to me. I'm wondering if part of both those lengths was just space taken up by the ram body and not actually used stroke. That space perhaps could be taken up by a dummy plug and a more readily available shorter spring used.
I'm just spit balling here. Without seeing the original guts of what were working with here I'm probably of little use. I do wonder if the gun itself is worth re-engineering it. That can only be determined by the owner.
Be well
Ron
Mr. Ron,
Thanks for chiming in...
I will endeavor to take some practical measurements.
The available stroke IS very long, and that is the crux of the issue.
The original gas ram is a tad over 13" in length, 7-1/4" L cylinder; 5-7/8" L rod, and 1/2" of rod exposed at full compression.
If not used, I have a hard time understanding any manufacturer procuring such a long ram, and the compression tube and linkage to accommodate it if not fully utilized..
As for the rifle, a Umarex Octane is not a particularly valuable gun; I am going thru this exercise as an opportunity to learn...hopefully something about airguns...
I have this drive to fix things that are broken, especially when improvisation is involved. Akin to mounting a washing machine engine on a Piper Cub...
Ron,too....
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Find out what the actual stroke is. Measure the end of the compression tube to the trigger latch. Then measure the piston from the face of the seal to the trigger latch receptacle. Subtract that piston length from the first measurement and that will tell you what the actual stroke is.
You can't use the ram because afaik we don't know how much dead space it takes up with the ram body and any possible preload combined.
Once you know your stroke length, you can shop for appropriate springs. You may not need a crazy long spring.
Also does the trigger latch look compatible for a spring? Piston weight or lack of may come into play as well.
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Find out what the actual stroke is. Measure the end of the compression tube to the trigger latch. Then measure the piston from the face of the seal to the trigger latch receptacle. Subtract that piston length from the first measurement and that will tell you what the actual stroke is.
You can't use the ram because afaik we don't know how much dead space it takes up with the ram body and any possible preload combined.
Once you know your stroke length, you can shop for appropriate springs. You may not need a crazy long spring.
Also does the trigger latch look compatible for a spring? Piston weight or lack of may come into play as well.
That was easy enough, almost.
The stroke to the latched position of the sear is 4 3/4"
The sear has a slot for the pivot pin that will require ana dditional .100 travel to latch, probably due ti the auto safety ??
So, I would say that the actual stroke is 4.85"
Maybe the N-forcer Mini MF19-125 will fit the bill........... 19mm OD x 4.92" stroke.........
It is extremely close, however. .007" isn't much wiggle room...
I will need to get very exact with the measurements....
Piston I.D is .935" without the sleeve....
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The piston id is pretty average. What's the cylinder bore out of curiosity? What's the distance from the inside face of the piston to the rear of the piston?
Did I say pictures would help A LOT?
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The piston id is pretty average. What's the cylinder bore out of curiosity? What's the distance from the inside face of the piston to the rear of the piston?
Did I say pictures would help A LOT?
OK. I may have goofed... again.
Here is a pic of the piston
If the square hole is the sear laltch point, then the stroke is only 3 3/8", and I can indeed use a Crosman NP2 ram..
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If the square hole is the sear laltch point, then the stroke is only 3 3/8"...
You quoted the Vortek spring at 48 lbf/in., and the stroke at 3.375"
If PS = piston stroke, PL = preload (both in inches), and SP = spring rate in lbf/in.
Spring energy to the piston in ft. lb. is ((PS+PL^2) - (PL^2)) x SR /24.
So, with one inch of preload, that would be ((3.375 + 1)^2 - (1^2)) x 48 / 24 = 36 ft. lb., which would put muzzle energy somewhere in the 12 ft. lb. range. With 2" of preload, that would rise to 49.7 ft. lb. to the piston, nearer 16 ft. lb. at the muzzle.
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If the square hole is the sear laltch point, then the stroke is only 3 3/8"...
You quoted the Vortek spring at 48 lbf/in., and the stroke at 3.375"
If PS = piston stroke, PL = preload (both in inches), and SP = spring rate in lbf/in.
Spring energy to the piston in ft. lb. is ((PS+PL^2) - (PL^2)) x SR /24.
So, with one inch of preload, that would be ((3.375 + 1)^2 - (1^2)) x 48 / 24 = 36 ft. lb., which would put muzzle energy somewhere in the 12 ft. lb. range. With 2" of preload, that would rise to 49.7 ft. lb. to the piston, nearer 16 ft. lb. at the muzzle.
The spring rate sill increase if the spring is shortened.......
I am going to do a partial mock assembly of the piston and cocking linkage to see if I can't get an accurate stroke dimension.
It baffles my mind that a manufacturer would spec a long stroke spring, then utilize only 70% of the available stroke.
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OK. I may have goofed... again.
Here is a pic of the piston
If the square hole is the sear laltch point, then the stroke is only 3 3/8", and I can indeed use a Crosman NP2 ram..
I think we are overcomplicating things here.
IIRC, the Re-Axis models were the first to take into account that as far as gas spring life was concerned, it was better to put the body of the gas spring into the piston and use the rod at a centering washer at the rear.
If so, then the main issue is not which spring to use, but how to design the two part guide that needs to guide the spring when the piston has no stem.
Yes, that square notch at the rear is what locks into the trigger sear/ramp. When the trigger breaks the sear/ramp drops and the piston flies forward.
IF the ID of the piston is 0.935" , then I would use a Titan #2 (894" ID, 0.610"ID, 0.142 WD, 30 coils, LAR -unset- 11.46")
And then adjust the rear outside guide as well as the front inside guide to match the needs.
Of course you could make a dual diameter guide and just use it at the front, but it would probably be too heavy if made of solid steel.
You can use a hollow guide and lighten the weight of the guide.
If you do this and you get too little power, then there are longer springs, but I am afraid that 3.375" for stroke is not a lot. If you use the above mentioned spring, it will compress to 80% of solid, so that is a good duty cycle for a normal life.
Remember when you have the liberty to choose the spring ALWAYS choose the largest OD you can fit into the piston.
While it is true that springs expand upon compression, it is rare that a spring expands by more than 0.015".
AND, unless you know that the spring is made of valve spring steel (usually Si-Va), it is not worth the effort.
HTH, keep us posted!
HM
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Thanks for the very specific and useful information, Hector.
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Thank you, Hector, and Peter for inviting a couple of experts into the conversation.
I am going to do a partial reassembly of the cocking mechanism and the piston so that I can nail down for sure the stroke length.
I am still asea at the thought that a manufacturer would spec a long stroke gas ram then use only 70% of the available stroke.
If this is typical, then other manufacturers must have really short strokes in their gas ram equipped rifles.
Maybe gas rams follow some of the same design considerations of coil springs??
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Remember when you have the liberty to choose the spring ALWAYS choose the largest OD you can fit into the piston.
While it is true that springs expand upon compression, it is rare that a spring expands by more than 0.015".
AND, unless you know that the spring is made of valve spring steel (usually Si-Va), it is not worth the effort.
HTH, keep us posted!
HM
Should the sleeve be eliminated?
The sleeve had an ID of about .81" IIRC.......
What is the purpose of the sleeve?
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Give this palce a call.
https://www.airrifleheadquarters.com/page/page/251327.htm (https://www.airrifleheadquarters.com/page/page/251327.htm)
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Give this palce a call.
https://www.airrifleheadquarters.com/page/page/251327.htm (https://www.airrifleheadquarters.com/page/page/251327.htm)
Mr. James does not include a phone #, and pretty definitely states that, "If you don't see it, we don't have it."
I have talked with Tom at Vortek.
Nice guy!
I am going to provide him with data he requested to see if he can develop a PB-4 kit for the Octane.
Stay tuned.......
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Do you have the stuff to machine a few parts?
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Do you have the stuff to machine a few parts?
Yessirree...........
Logan 820 metal lathe for starters.......
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I'll give you a trick I use to measure actual stroke length without all the math.
I have a failed Crosman Gas piston from a Gun i fixed for a guy long ago.
I drilled a small hole in it so it travels easily.
I put that in a gun with clay to hold it in place then cock the gun.
Once taken out? I have a exact measurement of stroke and can make parts to adapt springs or Gas Rams.
And before anyone says that's Brillent?
It's just lazy.
;D
Work smarter. Not harder.
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I have a pretty good handle on the stroke length now.
I put the piston in the compression chamber all the way forward, then measures the distance from the sear latch slot in the piston back to the sear in it's rearward position.
Using a digital caliper that dimension measured 3.25"
Now, I wish I understood why Umarex used such a long stroke ram in an application with a much shorter stroke.....
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Here's a image that shows some mods for adapting Gas Rams.
That's for Crosman Gas Rams to early Hatsan Spring Guns.
(https://www.gatewaytoairguns.org/GTA/MGalleryItem.php?id=8656)
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Thanks, Mr. Jeff.
I adapted a Crosman NP ram into a Hatsan Striker last year, but those 2 were close in specs.
This Reaxis is a horse of a different color.......
Mr. Tom at Vortek said there was more to it than just the stroke length, but he would not elaborate....
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A Gas Ram does not require as much preload as a Wire Spring as a start.
I've taken Gas ram guns down and rebuilt with no compressor.
I'd not suggest trying that with out a good spring compressor!
I had one get away from me once. I don't want to EVER go through that again!
So I built a Spring Compressor using a scissor jack found in many cars.
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A Gas Ram does not require as much preload as a Wire Spring as a start.
I've taken Gas ram guns down and rebuilt with no compressor.
I'd not suggest trying that with out a good spring compressor!
I had one get away from me once. I don't want to EVER go through that again!
So I built a Spring Compressor using a scissor jack found in many cars.
I made one by turning the OD of a piece of 3/4" pipe to fit 1" scope rings, and threaded a beam clamp on the end.
Works great!
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I don't trust rings to hold a Spring with a 3 inch preload.
But that's just me.
I tried that and I have a set of rings showing a near fail so stopped using it.
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I don't trust rings to hold a Spring with a 3 inch preload.
But that's just me.
I tried that and I have a set of rings showing a near fail so stopped using it.
After that caveat I may machine a longer pipe so that I can put the sliding pipe clamp on the breech block end,
and use the scope rings as a guide, allowing the pipe to slide in them.
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I'll take a picture of my set up.
You might like it.
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I have a Sun Optics spring compressor. But before I found a good sale price I had one of them scissor jacks on the ready to make Jeffs style, since then I have found other uses for it, such as sticking it in the dash of a Ram Pickup to expand some metal to fit a new stereo. ;D
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Okee dokee,
Yet another re-measurement....
I have been educated on where the sear is actually s'posed to be located.
The piston will actually telescope over the nose of the butt plug.
Now, with everything in its proper position, the stroke measures right at 5"
Now the piston stroke length makes more sense
As I have not as yet found a gas ram with sufficient stroke length, looks like a coil conversion is in the offing.
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OK. Had a picture uploaded here forever!
(https://www.gatewaytoairguns.org/GTA/MGalleryItem.php?id=5646)
It's mounted to a swinging TV stand so I swing it under my basement steps when not using it.
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That looks as elegant as my Crosman pumper assembly jig.....
And probably works as well!
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It don't have to be pretty. It just has to work right?
;D
And total cost is $0 as everything was scrap or found parts.
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It don't have to be pretty. It just has to work right?
;D
And total cost is $0 as everything was scrap or found parts.
True dat!
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Now that I am closing in on a suitable mainspring,
piston mass comes into play.
The Reaxix gas spring was utilized in a rod-rear configuration.
I am still not certain that there is an advantage to that, as I am uncertain that the body has more mass than the rod.
Anyway, how does the mass of a coil spring figure into this equation?
Should I use a longer spring with no mass adding components such as a top hat?
Or, use a shorter spring with spacers??
If that, how much mass in the piston?
Will that need to be heavier than the mass of the main spring of the same length??
Details, details, details.........
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Now you are overthinking the problem ;-)
Coil springs have mass and the one I just measured weighs more than an equivalent gas spring. At least part of the spring mass contributes to moving/piston mass. It's not as easy to calculate the ratio as it is with the gas spring, but the difference is small and precise calculations are a wasted effort.
The piston provides the BULK of the moving mass so any changes made are small fraction of that mass. Adding/subtracting some small amount of moving mass MAY shift rifle performance to slightly prefer heavier or lighter pellets. But you will not determine that until you can shoot a whole bunch of different pellets and log significant data to confirm a performance difference.
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I tend to do that...
I knew that the spring added mass to the equation, but I also know that they do not release their force
at a constant rate, bit rather oscillate during rapid extension......
'Anyway, I'm gonna purchase the longer Vortek spring and go from there....
Recommendations on amount of preload??
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Pretty sure that has been talked about somewhere.
Bob or Lloyd could give you the exact math on all that.
Mostly when they do? I get a head ache as it's WAY above this balding head.
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Pretty sure that has been talked about somewhere.
Bob or Lloyd could give you the exact math on all that.
Mostly when they do? I get a head ache as it's WAY above this balding head.
You should stand on a milk crate.....
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I tend to do that...
I knew that the spring added mass to the equation, but I also know that they do not release their force
at a constant rate, bit rather oscillate during rapid extension......
'Anyway, I'm gonna purchase the longer Vortek spring and go from there....
Recommendations on amount of preload??
Yes, coil spring force does change a lot more than a gas spring over the expansion distance. BUT energy under the curve is the SAME for both springs so ME of the rifle is essentially the same as well. Longitudinal oscillation waves occur in a coil spring from both the start & stop shock impulses, but these are well dampened by a good spring guide.
BALLPARK calculation indicates 840142-44 spring could store enough energy to get you 24fpe ME if you start with a 2" preload and a 4.8" stroke. Actual ME depends on many other factors so this is only an approximate starting point.
edit: I like to start with longest spring (& largest preload) possible and cut coils until the desired ME is attained. Sometimes that results in a harsh shooting rifle. Usually cutting a couple more coils reduces the ME a couple fpe and the shot cycle improves. This slight "de-tuning" can provide a shot-cycle sweet-spot where the rifle becomes comfortable to shoot. When you are comfortable shooting a springer it usually improves accuracy.
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That's where I will start the process.
Do the ends need to be closed and ground, or just ground to square??
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Buy whichever spring you choose closed and ground flat to start. Observe & photo ends so you know what they look like new.
If necessary to cut spring suggest one or two coils(max) at a time and reclose-temper-grindflat ends before retesting in rifle.
Many online and youtube sources showing how to cut-heat-reclose-temper-grindflat main-spring ends.
I use angle grinder(cut), propane torch(heat), needle nose pliers(bend), old motor oil(temper & surface treatment), 1" belt sander(flatten), and fine grit wet-dry sandpapaer(polish).
Best wishes :-)
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Remember when you have the liberty to choose the spring ALWAYS choose the largest OD you can fit into the piston.
While it is true that springs expand upon compression, it is rare that a spring expands by more than 0.015".
AND, unless you know that the spring is made of valve spring steel (usually Si-Va), it is not worth the effort.
HTH, keep us posted!
HM
Should the sleeve be eliminated?
The sleeve had an ID of about .81" IIRC.......
What is the purpose of the sleeve?
A "sleeve" with an ID of 0.810" for a Piston's ID of 0.935" is not a sleeve; it is a bushing.
And that gives you an inkling of why the manufacturer uses only a fraction of the total available stroke. Using the total stroke would raise the pressure beyond acceptable limits for the seals.
Remember that gas springs start from a fairly high pressure (ORings seal better with substantial pressure and they more often fail when working at low pressures) and, because of that the elevation of pressure inside the gas spring is fairly small, the force is fairly constant (compared with the steel spring that has a linear relation that starts at a very low value).
In steel spring'ed guns, there is a preload, at most of about 2½" in most cases, but, even at the stated rates, this only means a starting point of about 60-70 # And the top force of the spring in magnum airguns is usually in the 200 - 300 # range (nothing too new since crossbows have operated more or less in the same region for the last 2,500 years).
THE reason to put the body into the piston and let the stem of the gas spring abut the trigger unit is basically that internally lubed systems that are not continually active, tend to have all their lubes deposit into the lowermost portion of the architecture.
If you use the body-backwards of most architectures, the stem becomes a "dry" region and the seals suffer accordingly.
Putting the body of the gas spring into the piston now reverses the behaviour and the point where all the lubes accumulate is the stem.
All seals are lubed at all times, and they will last longer.
This is why I recommend standing the DIANA NTec rifles on the muzzle when you are putting them away for a long time (more than 2 weeks). There have been all kind of jokes about this, but believe me it works.
There are other steps that you need to take to protect a gas spring'ed rifle, but in your case that would be "Tuesday morning quarterbacking" because the gas spring has already failed.
Remove the "sleeve" you have and get some hard plastic material where you can fashion a real sleeve from (the tubes that are used to ship the Titan springs are particularly good for this), and use it as a piston "liner" glued with some tar to the inside of the piston's walls.
Make sure you leave the cocking lever channel clear, and that there is enough space for the steel spring to expand.
The purpose of a true piston liner is to prevent the steel spring form contacting the inside of the piston's body and making noises.
There is NO OTHER REAL USEFULLNESS.
Get the suggested spring and start designing the guides. Once you have a WORKING gun we can think about refinements.
JMHO
HM
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Thank you, Mr. Hector.
FWIW, once I understood the sear location, I measured the stroke at 5"
There is 1/4" of preload. So, the gas ram stroke length of 5 3/8" is pretty doggone close....
I have ordered a Vortek 840142-41 spring.
.840" OD, .142" wire diameter 41 coils closed,ground and polished at 14" OAL.
This is to replace the gas ram that was 13" OAL but have to give up 1" at the end plug as the tube that projects 1" forward is too small to accommodate
the spring ,721" ID, .858" OD
I will make a spring guide to fit into the end plug, then extend forward.
Maybe a tophat for the front inside the piston ??
The sleeve is actually .845" ID, but too tight for the spring. I will use plastic of appropriate thickness, maybe about .030" ??
The sleeve wall thickness is .018"
I believe this spring has a rate in the 48# range, so 2 1/2" or preload will be about 120#, and cocked force of about 360...
That may me too much....dunno
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Thank you, Mr. Hector.
FWIW, once I understood the sear location, I measured the stroke at 5"
There is 1/4" of preload. So, the gas ram stroke length of 5 3/8" is pretty doggone close....
I have ordered a Vortek 840142-41 spring.
.840" OD, .142" wire diameter 41 coils closed,ground and polished at 14" OAL.
This is to replace the gas ram that was 13" OAL but have to give up 1" at the end plug as the tube that projects 1" forward is too small to accommodate
the spring ,721" ID, .858" OD
I will make a spring guide to fit into the end plug, then extend forward.
Maybe a tophat for the front inside the piston ??
The sleeve is actually .845" ID, but too tight for the spring. I will use plastic of appropriate thickness, maybe about .030" ??
The sleeve wall thickness is .018"
I believe this spring has a rate in the 48# range, so 2 1/2" or preload will be about 120#, and cocked force of about 360...
That may me too much....dunno
Lots of questions about the choice, but, we'll see what happens.
Keep us posted not only on the initial results, but also about what happens at shot #1,000; 2,000; 3,000; etc.
HM
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I've got a couple springs here I'll give you to play with if you'd like.
Better to screw up an old spring outta the Gate then a New one.
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Thank you, Mr. Hector.
FWIW, once I understood the sear location, I measured the stroke at 5"
There is 1/4" of preload. So, the gas ram stroke length of 5 3/8" is pretty doggone close....
I have ordered a Vortek 840142-41 spring.
.840" OD, .142" wire diameter 41 coils closed,ground and polished at 14" OAL.
This is to replace the gas ram that was 13" OAL but have to give up 1" at the end plug as the tube that projects 1" forward is too small to accommodate
the spring ,721" ID, .858" OD
I will make a spring guide to fit into the end plug, then extend forward.
Maybe a tophat for the front inside the piston ??
The sleeve is actually .845" ID, but too tight for the spring. I will use plastic of appropriate thickness, maybe about .030" ??
The sleeve wall thickness is .018"
I believe this spring has a rate in the 48# range, so 2 1/2" or preload will be about 120#, and cocked force of about 360...
That may me too much....dunno
Lots of questions about the choice, but, we'll see what happens.
Keep us posted not only on the initial results, but also about what happens at shot #1,000; 2,000; 3,000; etc.
HM
The Vortek spring was recommended by mikeyb...BUT
Nothing is etched in stone...........I can try the one you suggested or ..........??
As the stroke turned out to be 5", the longer spring may be beneficial.
I am a touch leery about giving up the 1" at the end due to the end plug.....I can make a new one if necessary.
Ron
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I've got a couple springs here I'll give you to play with if you'd like.
Better to screw up an old spring outta the Gate then a New one.
Thanks for the ogger, Mr. Jeff.
Whacha got??
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I got one from a Hatsan Mod 95, and a crosman spring also.
I'll get the specs for you. May not be what you need but gives you something to practice on.
And I'm cleaning out a bunch of stuff and hate to just trash it.
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I got one from a Hatsan Mod 95, and a crosman spring also.
I'll get the specs for you. May not be what you need but gives you something to practice on.
And I'm cleaning out a bunch of stuff and hate to just trash it.
Sounds like a plan.
You don't perchance have a cocking lever for a Daisy 856/860 ??
Thanks...
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No. I probably don't have the cocking lever. Think I only have 1 Daisy.
And that's a 106
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Thank you, Mr. Hector.
FWIW, once I understood the sear location, I measured the stroke at 5"
There is 1/4" of preload. So, the gas ram stroke length of 5 3/8" is pretty doggone close....
I have ordered a Vortek 840142-41 spring.
.840" OD, .142" wire diameter 41 coils closed,ground and polished at 14" OAL.
This is to replace the gas ram that was 13" OAL but have to give up 1" at the end plug as the tube that projects 1" forward is too small to accommodate
the spring ,721" ID, .858" OD
I will make a spring guide to fit into the end plug, then extend forward.
Maybe a tophat for the front inside the piston ??
The sleeve is actually .845" ID, but too tight for the spring. I will use plastic of appropriate thickness, maybe about .030" ??
The sleeve wall thickness is .018"
I believe this spring has a rate in the 48# range, so 2 1/2" or preload will be about 120#, and cocked force of about 360...
That may me too much....dunno
Lots of questions about the choice, but, we'll see what happens.
Keep us posted not only on the initial results, but also about what happens at shot #1,000; 2,000; 3,000; etc.
HM
The Vortek spring was recommended by mikeyb...BUT
Nothing is etched in stone...........I can try the one you suggested or ..........??
As the stroke turned out to be 5", the longer spring may be beneficial.
I am a touch leery about giving up the 1" at the end due to the end plug.....I can make a new one if necessary.
Ron
There are even longer springs in the Titan lineup.
If you can chuck the rear end plug in a 4 jaw chuck and center it correctly, this COULD work as a part of your guide system.
In these conversions you need TWO part guides (at least). Imagine a full length TopHat, to say it in a simple way.
This rear end plug could be the end that holds the spring in place and centers the travelling guide to a proper position to ensure that the hook/ramp locks into square hollow of the piston.
I am serious when I say that any spring will do, at this point it is unimportant. What WILL define the future usefulness of the rifle is how accurate and smooth it can be, forget the power at this point.
The accuracy and usefulness of these conversions is dictated by the guides and end-plug's architecture.
It took us many tests to come up with the right mixture of length, weight, weight distribution, and tolerances in the guide system to achieve the EMS system (that is, essentially, a steel spring version of a NATIVE gas spring version). We experienced many premature spring breakages, many "twisty" springs, many poor shot cycles. Everything seems easy once you understand it and it has been done, before that . . . it's a different story.
If your trigger has a sliding hook, like the Walther Century Varmint, it will be more tolerant of misalignments at the sear latching point, but if it has a ramp, like the DIANA T06 NTec, then tolerances at this instant in the cocking cycle will be critical.
I would take Privateer's generous offer and just get started.
JMHO
HM