Sleeving springs with plastic milk jugs, any updated info?

[Broadside]

I'd read a couple posts on the topic, both being months old, and I wasn't sure if resurrecting them would be OK or not.

Just asking for any updated from those who have done it. Any issues? I'd thought the sleeve would need to be slotted for the cocking lever foot, as did others, but had seen where the entire spring was being "wrapped". Is the foot sliding across the liner causing and wear issues, possibly shaving plastic particles?

I made a sleeve for mine this AM, and am curious about clearances. The plastic is .016, piston ID .850, and spring OD .770, which leaves .080 clearance between the spring and piston, and less the .032 for the plastic leaves roughly .050 (.048 to be exact). Just after cutting, and installing the plastic, I was wondering about how tight was too tight (for lack of a better term). The spring (when inserted and piston pointed seal-up) would allow gravity to slowly allow it to slip out of the piston. After just taking the measurements (hours after assembling spting in piston with liner), I noticed things seem to have "relaxed" a bit, and the fit seems quite a bit better.

Anybody care to share pros/cons of doing this mod or any updates at all (since months have past since some members have done it and there didn't seem to be any updates)? Thanks!

 

[cnjl3]

You are talking about the "Poor man's Delrin Spring Guide"
http://www.gatewaytoairguns.org/GTA/index.php/topic,8330.msg68150.html#msg68150
Sounds easy enough and I will eventually give it a try since I don't own a lathe.
I have read good reports about it.  The above link says no appreciable wear within two years and about a thousand shots. I too would like to hear of report/updates on this process.

[Sfttailrdr46]

You are talking about the "Poor man's Delrin Spring Guide"
http://www.gatewaytoairguns.org/GTA/index.php/topic,8330.msg68150.html#msg68150
Sounds easy enough and I will eventually give it a try since I don't own a lathe.
I have read good reports about it.  The above link says no appreciable wear within two years and about a thousand shots. I too would like to hear of report/updates on this process.

Mark 611 did one and posted results on the German airgun gate

[cnjl3]

Yes, I saw that - sure sounds like it is worth the trouble of opening up an AG and trying it out.

[Sfttailrdr46]

I believe if you follow the thread there are some initial results posted also other threads after I buy a chrono I'll start posting my tune results. Just too busy adding toys to my collection right now to spend on a chrono

[Petey]

You adjust the clearance with the width...... trim the plastic to 3/4 the length of the guide and adjust the width so the spring requires some pressure being pushed over the guide. Once assembled you should be able to move the spring up and down on the guide using about 5 pounds of force... no real need to be exact about it .
 
Works fine and simple as all can be to do....Use a green Mt dew or Sprite bottle for the spring...Milk jug or alike for the piston.

Have Fun!

Petey

[Mark 611]

 

[Broadside]

Carlos- Yes, that was one of the posts I'd read, and did in fact miss the fact where he'd stated doing it 2 years ago (DOH!), so thanks for bringing that front and center.

As far as any adjustments, I may just try some experimentation on sizes. I suppose one day I'll spring for a chronograph as well, just to know which direction any changes are making.

Something I'd just noticed, I had already cleaned-up the spring ends by stoning. I also have to mention one thing, that the internals of my Silent Cat didn't seem too awful bad as far as tolerances and burrs. That said, I'm talking from a realistic standpoint of working an an inexpensive mass-produced product. I honestly expected worse.

Anyway, it didn't take much stoning to clean the spring ends, and (being a noob) I was under the assumption this was to allow the spring to screw/unscrew on the shoulder of the tophat during compression/decompression. After stoning, it was a noticeably smoother feel when twisting the 2 together even without being lubed.

I took a penny, and traced around it on another piece of milk carton, and placed the disc into the piston and inserted the tophat on the end of the spring. While I somewhat compressed the spring into the piston (by hand), I twisted the spring and noticed the tophat stayed stationary on the spring, and it (tophat) spun in conjunction with the spring.

If that's the case, wouldn't it do the same in the piston, without the plastic disc (and after being lubed)?  Or is it totally different situation at full compression (as in being cocked) with additional force being applied? 

Would there be any mechanical advantage of one over the other, meaning the spring moving with the tophat staying stationary, or the tophat twisting against the inside of the piston?  Thanks!

[Bullit]

What do you do with the sacrificial pieces that get cut/rubbed off during use?  A straight coil spring generally expands (in width), as it is compressed.   A tight fitting stud on the I.D.  will allow the spring to expand while cocking it, and then "capture" it when it releases.  PTFE isn't the best for such hard thrusts.
Stainless steel will do much better.   You can have a fine fitting Tophat that rotates, and there's nothing wrong in my book there.  Free rotation means no torque.

[Broadside]

What do you do with the sacrificial pieces that get cut/rubbed off during use?  A spring expands as it is compressed.   A tight fitting stud on the I.D.  will allow the spring to expand while cocking it, and then "capture" it when it releases.
You can have a fine fitting Tophat that still rotates, and there's nothing wrong in my book there.

That was part of my OP, concern for any particles being shaved-loose, the member who'd done the mod 2 years ago hasn't stated it being an issue, so I don't know. Perhaps by the time it ever became an issue, it would be time for maintenance anyway?

OK, on the rest, bear with me, I understand as the spring compresses/decompresses, it expands/contracts (which was what I meant by saying screwing/unscrewing), but not understanding how that applies to what I'd ask? Meaning it's the pressure of the spring end on the shoulder of the tophat "locking" the 2-together under pressure/compression, since the spring is "unscrewing" or expanding, correct?

I can take the spring and tophat out of the piston, tip the spring over, and the tophat will fall right out, so it's not a tight fit by any means. Are you saying it should be? Thanks!

[Motorhead]

Another source for plastic that personally feel a better choice than milk jug / soda bottle  is using already round thin wall plastic tubing.

Can be found  in M&M christmas candy etc ... Packaging that contain long small diameter parts get packaged in the stuff.
being it starts out round generally 1 1/4 - 1 1/2" cutting to correct diameter is simply a cut down it's length and remove what needed to have ends butt inside piston cavity.

Just a suggestion ... nuttin more

[Bullit]

Yeah, those were shade tree posts that got beat to hllll by the elder tuners.  Snug up the stud fit on the spring, and within the piston.  Make sure everything rotates as free as possible.  This "isolates the spring twist", eliminates torquing and rattling by keeping it from touching sides and staying centered.  I'm sure you get the idea here.
Edit:  I can't spell 

[Bullit]

The only "plasic" type that I know of that can hold up to severe thrust or rubbing damage is called "UHMW".   It's ultra high molecular weight polyethelene.  I use it alot.  But for  common folk, it's expensive.  Not being snooty here, but rather, frugal.  Stainless polished washers with lube does the same for this job.