Stripping my s/h 0.22 Remington Express Compact

[evert]

That’s interesting evert, I wonder if there’s an optimum seal resistance ? If when I’ve got it apart I could push the piston back to its ‘at rest’ position, remove the spring, find a steel tube that fits over the piston rod then fit a plate to the top on which I could place weights. Weighing the tube and plate I can then mount the cylinder vertically in a clamp and start adding weights til the piston moves.

Might be an interesting experiment

That experiment will give some useful insight. It would be interesting to se how power changes with different seal resistance.
I'd guess that there's different "best" seal resistance for different types of seals and guns. Some seals have thin sealing lips that expand when pessurized, this probably causes a lot of friction that you cant detect with the sliding test.
I prefer to try different seals from different makers before sizing.
You can often find one that fits and does what you want without removing any material if you have several to choose from.
But that big box of seals costs a bit of money.....

[Mr.Fixit-Norm]

Yes it would be quite expensive to experiment with seals from different sources ! The new one I bought was from the Chambers air gun spares site and was listed as 28.6mm, and is identical in size, colour, price and part number to the Diana 34 seal !

Maybe a Diana 34 seal from a different manufacturer would be worth a go ?

The thing is the cylinder measures 28.0mm maximum and I was wondering if 28.6mm is too big to even wear in ?

I sized it down to approx 28.4mm thinking this would be safe ( the old one that came out was 28.2mm.), but are there any guns with a seal at 28.2 or 28.4 as std ?

Something else I was wondering, both the HW35k I recently worked on and the Remington have similar internal setups and both have springs with top hats and rear spring guide, both have slip washers and new piston seals and are lubed with ‘bumslide’

The Remington has absolutely no twang whatsoever and if you didn’t see it shoot but heard it, you’d think it was a precharged gun or gas ram
The 35 on the other hand still has a slight but noticeable twang ? The only thing I could think of that could be making a difference is that the Remy has an external metal spring guide between the spring and the inside of the piston, could this be creating additional twang dampening ?

Norm.

[Shed tuner]

the Remy has an external metal spring guide between the spring and the inside of the piston, could this be creating additional twang dampening ?

Norm.

yes, which is why lots of us fit them

[Mr.Fixit-Norm]

yes, which is why lots of us fit them

Ahh right, so I was on the right track then , do you have any info on material to use and any measurements ? I’d be quite interested in making and fitting one

Also any snags and pitfalls to avoid would be good as well

Cheers,

Norm

[TonyL]

Ahh right, so I was on the right track then , do you have any info on material to use and any measurements ? I’d be quite interested in making and fitting one

Also any snags and pitfalls to avoid would be good as well

Cheers,

Norm

A wide choice of materials, Norm.. The "connoisseur's choice" would, most likely, be shim steel. But many successful and effective sleeves come from PTFE sheet (usually 0.5mm), plastic bottles, beer and soft drinks cans (mostly aluminium these days) and a few steel ones. Pretty sure Jon has advocated WD40 cans before, as they're steel and, therefore, harder wearing. Don't have them fitting too tightly and bear in mind that the spring's diameter will increase slightly when compressed. Some generous castellations to keep in place and a nice thrust washer to protect the sleeve and give a bearing surface.

[evert]

yes, which is why lots of us fit them

Yes, spring sleeves can be helpful to reduce vibration.... but as I have ranted about earlier, well fitted internal guides may be better, as they isolate the spring better from the piston.
Why add thrust washers to isolate spring rotation from the gun, and then create contact between the sides of the spring and the piston???

[Mr.Fixit-Norm]

yes, which is why lots of us fit them

I meant to ask this as well the other day, do you make them a complete cylinder or do you have to leave the bit clear where the cocking slot is ?

Cheers,

Norm

[Shed tuner]

I meant to ask this as well the other day, do you make them a complete cylinder or do you have to leave the bit clear where the cocking slot is ?

Cheers,

Norm

complete, with the join on the opposite side to the cocking slot. a small gap at the join is fine - an over-lap is not.
The cocking shoe shoudl ride on the cocking slot, and not dig into the sleeve. If it does, smooth the cocking shoe, as it would be gouging into the spring too.. then fit a new sleeve

Have you made that 15 g steel TH yet ?

[Mr.Fixit-Norm]

complete, with the join on the opposite side to the cocking slot. a small gap at the join is fine - an over-lap is not.
The cocking shoe shoudl ride on the cocking slot, and not dig into the sleeve. If it does, smooth the cocking shoe, as it would be gouging into the spring too.. then fit a new sleeve

Have you made that 15 g steel TH yet ?

Thanks for the info, I did wonder if it could be a complete cylinder as I’m sure I’d seen pics of homemade ones that had a slot that matched the cocking one ?
It’ll be a lot stronger as a complete cylinder. I was wondering about joining it, I did think about using tin and once rolled to the right dimension, make a butt joint with say a 0.5mm gap and solder it then carefully file it back ?

I did find a specialist company that made very thin walled stainless tube ( 0.5mm wall thickness ) any size in 0.5mm increments up to 35mm, I was going to ring them next week with a plausible story and see if I could get a 100mm long ‘sample’

I did make the steel top hat after a load of hassle with my lathe It’s a 1945 Myford 3 1/2 M series and it’s been playing up. It didn’t matter how sharp or how I set up the tools/ speed, it would start to chatter really badly when cutting, even if just a fine cut. The problem was two fold, the headstock bearings needed adjustment and it was only obvious when I loosened the belt drive and found about 0.5mm of up down movement at the Chuck

My mate Tony found an original Drummond manual pdf online which covered the bearing adjustment ( they’re tapered phosphor bronze ones and tighten up facing away from each other ! )

Having done that ( 3 times ) it was still chattering a bit and I think it’s because the 5” Chronos Chuck I bought to replace the worn original, is really too far away from the bearing. If I fit the low profile Crown 4 jaw Chuck ( which has its own issues ) it doesn’t chatter at all but this Chuck has damaged scroll screws - try finding a set of them on the net, it’s a bit like trying to find hens teeth buried in rocking horse poo somewhere in a large haystack

Anyway, I got it good enough to make a top hat but due to the size constants it only weights 10g

I’m going to fit it tomorrow and see what happens, I’ll also strip the HW35 and measure it up for a piston guide

Phew,

Norm

[Shed tuner]

cool, even 10g will help. if you can add a steel washer/disc weight so much the better, but try just the TH first.

Don't over think the piston sleeve - just a rolled up tube (beer can, wd40 can, plastic bottle, ptfe sheet, whatever) stuffed in there will work perfectly for years. Spend the time you save adjusting your headstock bearings

[TonyL]

That’s interesting evert, I wonder if there’s an optimum seal resistance ? If when I’ve got it apart I could push the piston back to its ‘at rest’ position, remove the spring, find a steel tube that fits over the piston rod then fit a plate to the top on which I could place weights. Weighing the tube and plate I can then mount the cylinder vertically in a clamp and start adding weights til the piston moves.

Might be an interesting experiment

That experiment will give some useful insight. It would be interesting to se how power changes with different seal resistance.
I'd guess that there's different "best" seal resistance for different types of seals and guns. Some seals have thin sealing lips that expand when pessurized, this probably causes a lot of friction that you cant detect with the sliding test.
I prefer to try different seals from different makers before sizing.
You can often find one that fits and does what you want without removing any material if you have several to choose from.
But that big box of seals costs a bit of money.....

That would, most definitely, be a most interesting investigation, chaps. As evert says, I think there would be different optimal resistance with different types of seal. Generally, we've just gone by "feel" previously.

[Mr.Fixit-Norm]

That experiment will give some useful insight. It would be interesting to se how power changes with different seal resistance.
I'd guess that there's different "best" seal resistance for different types of seals and guns. Some seals have thin sealing lips that expand when pessurized, this probably causes a lot of friction that you cant detect with the sliding test.
I prefer to try different seals from different makers before sizing.
You can often find one that fits and does what you want without removing any material if you have several to choose from.
But that big box of seals costs a bit of money.....

Hi Evert,
Sorry but due to the issues I had with the piston sleeve / spring and time constraints, I didn’t really have time to start fabricating a resistance checking device but if it gets stripped again I definitely will

Norm

[Phil Russell]

Re: seal resistance.
That would make fascinating readings. I suspect that optimal seal resistance will also be influenced by the power being generated by the spring and also, of course, by any lubrication on the seal that influences its resistance against the cylinder wall.
Cheers, Phil

[evert]

Seal resistance experiments is interesting, but as stated earlier, there are some variables that are difficult to measure, like friction under pressure, and how different seal materials react to pressure.

And powerful guns with heavy springs are less sensitive to seal resistance.