Designing a Spring Compressor

[Methuselah]

I'll post a pic or two when I finish building it, but was wanting to know if 2" of travel in releasing spring (or ram) travel will be enough, and if not, will it be enough to handle the rest of the travel by hand?  If it matters the three are Hatsan 125, Remington Express, and D34.  All three need work...

[Roadworthy]

Two inches of travel should be adequate for most guns.  If you install a new spring which hasn't been set you will probably be looking at four inches of travel.  The cure for that - set the spring before attempting to install it.  This is only a problem with new springs.

[BenjiHunter]

"set the spring"
What does that mean?

[Roadworthy]

Setting the spring (also known as scragging) has to do with changing the spring length, which would happen over time in the airgun.  A brand new spring may be difficult to install as it will be too long.  If you compress the spring to the point of being coil bound and leave it for about four hours before removing the pressure it will assume its working length.

Read the article for more information:

https://www.pyramydair.com/blog/2012/03/resizing-a-mainspring/

[BenjiHunter]

Thank you.

[Doug Wall]

Two inches is not nearly enough!!! Consider that the end block is set in a couple of inches, and I've worked on guns with about 3-4 inches of spring pre-load. Trying to "handle the rest of the travel by hand" would be a real pain, and potentially dangerous (slip with a heavily loaded spring!). I would go with at least six inches of travel (I have about 7" on mine).

[T-Higgs]

I truly believe you need more travel to work safely, especially on the 125. I would change the design so the pressing feature is adjustable and has a longer throw.

[Methuselah]

Two inches is not nearly enough!!! Consider that the end block is set in a couple of inches, and I've worked on guns with about 3-4 inches of spring pre-load. Trying to "handle the rest of the travel by hand" would be a real pain, and potentially dangerous (slip with a heavily loaded spring!). I would go with at least six inches of travel (I have about 7" on mine).

Well, I don't have to use it for the ones that need more than I will have, but a picture is worth a thousand words, so after the controlled release of 2" I'll be able to "slip" the yoke holding the breach end another inch or two and after that if it isn't possible to handle the load by hand with brute force then I'll know the contraption I've built can't handle the reassembly --- in that case I'd have to call it a design failure or if the ending pressure is not too bad, fix it to slip more.  Got most of it built, some supplies still missing but available locally, so will post the pic when it's finished.

Thanks all for the input!

BTW, 4" preload, does that apply to the three airguns I listed?  Hatsan 125, Remington Express, Diana (RWS) 34?  I know I've seen comments the D34 can be done without a compressor, but the Hatsan gets done first, before the warranty runs out I need to find out why FPE went from 28 to 24'#.  Great comments on setting the spring first too    Didn't think about that one!  Surely the two with springs aren't going to hold up forever...

[Back_Roads]

 Definitely the Hatsan 125 will need the 4" its a monster of a spring . gas springs when blown have no or little resistance but the new ones do put up a fight too. so yes re-design your project. I used a cheap 8"  C clamp to build a quickie version to replace gas ram in a Crosman MTR this spring. <~ pun not intended

[Booger]

I know I've seen comments the D34 can be done without a compressor.

SAFETY FIRST. The D34 does need a spring compressor. Yes I have seen it done without a compressor, but safety first. I even had a friend who would use a spring compressor on a TX200 because it makes things easier and less chance to scratch a customer's rifle.

[Roadworthy]

Two inches of travel is suitable for a gas strut powered gun but that's about it.  They typically have less than a half inch of preload.

Two inches is MARGINAL for a Diana 34.  It can be made to work but you have to work at it.  There are two pins holding it together.  I can tighten the clamp and remove both pins then start backing off the pressure.  When it is far enough back to put pin number two into hole number one I secure the action and readjust my stops.  Then I can resume pressure, remove the pin and back it off.  Reassembly is the reverse - a two step process.  I really need to rebuild my compressor.

I have no idea how much spring is in a Hatsan 125.  Due to the power the gun produces I suspect it's a very strong spring.  The Diana 34 or a TX 200 CAN be done without a spring compressor, though reassembly can be a real problem - compressing the spring and attempting to align everything at the same time.

The simple cure would be to use a properly designed spring compressor with threads adequate to go at least four inches and six inches would probably be better.

[T-Higgs]

125 Spring is a beast. My compressor has lots of travel and that spring still puckers certain parts of my anatomy!

[T-Higgs]

This was fairly easy and cheap. There will be many many designs on GTA that work well and won't break the bank.
http://www.gatewaytoairguns.org/GTA/index.php?action=dlattach;topic=89592.0;attach=116182;image

[Privateer]

I use an old scissor jack from a small car.
Gives me more then enuff travel for any springer!
Plus you can find them all over the place!
I've got 5 or 6 of them I've found.

[Methuselah]

This was fairly easy and cheap. There will be many many designs on GTA that work well and won't break the bank.
http://www.gatewaytoairguns.org/GTA/index.php?action=dlattach;topic=89592.0;attach=116182;image

The Hatan's a gas ram.  I did have a c-clamp I could have cut up but didn't want to have to hack-saw it and then drill mounting holes, so instead I bought this push-pull clamp:

http://www.gatewaytoairguns.org/GTA/index.php?topic=101808.msg961208#msg961208

The clamp is rated 500#, hope that's enough.  I think fill pressure on the Hatsan ram is 1900 psi.  The end bracket is 1/8" thick steel.  Anyway, almost finished then will post some pictures (before I try to use it!)

[Methuselah]

Sorry --- down and dirty after losing 30 minues to error ...

gun disassembled bad seal blahblahblah

6 pics ... now 1.  Back needs to be changed to "loose your post"... sigh

[Methuselah]

error:  empty body...

[Methuselah]

not empty

[Methuselah]

Hatsan 125 had about 1/2" to 1" of preload on the ram.

More later, getting stink-eye from daughter to get off puter...

[avator]

I would build it for more than 2". It's better to have more than you need than not enough and have to build it again. You never know what guns you may want to use it on in the future.