Can a short spring go coilbound?

[look no hands]

Hi all,

Simple quick question, can a short spring go coilbound?

Cheers

Pete

[TonyL]

It will if it's compressed enough, Pete.

So......what you on about?

[tinbum]

Spring room divided by wire thickness equals maximum number of coils

[CapitalBee]

You have to compare material thickness and number of coils really, rather than length. Sometimes , when fitting custom guides and top hats the over all length of the two exceeds the stroke length, especially if slip washers are added.

[Hsing-ee]

Theobens have the Devil's fingers inside them and can make strange things happen. You ever seen another rifle with a giant circlip holding the power in? There's a reason for that ....

[rancidtom]

A spring can become coil bound if the expansion in the spring diameter due to linear compression causes the coils to bind on the inside diameter of the piston. This can happen even when there is still space between the coils. The best way to test this is to compress the spring to the cocked length using a spring compressor and measure the outer diameter of the compressed coils, if it is greater than the inner diameter of the piston it will bind in the piston before the rifle can cock. Either use a smaller OD spring (and suitable spring guide/top hat) or open up the ID of the piston if practical.

[look no hands]

Theobens have the Devil's fingers inside them and can make strange things happen. You ever seen another rifle with a giant circlip holding the power in? There's a reason for that ....

Theoben is on the back burner now mate, it's the Airsporter this time.

Bit of a strange one this one, when I received my Diana 34 a few years ago it came with a Vortek kit (not fitted) which I was told by the previous owner, that the rifle wouldn't cock with the kit fitted, I fitted it and he was correct, you could cock the barrel almost to the point where it should be catching the sears but it just had this soft resistance (as if plastic was hitting plastic), anyway that kit was put aside and forgot about and another kit fitted, roll on a few years and I was reading the thread going at the moment about are Vortek kits any good and I thought I'd see if my kit would fit in my Airsporter RB2 as the internal dimensions and lay out are almost the same, remembering the Diana 28mm piston seal will fit earlier 28mm Airsporters and Mercs, the RB2 being 29mm though being fitted with the later BSA parachute style piston seal, the kit indeed does fit, the outer sleeve even fits inside the piston but you just have to remove the BSA plastic piston sleeve, all that was needed was the rear part of the spring guide trimming down a few mm's to fit inside the trigger block, there is hardly any preload when fitting the kit and it's a simple case of pushing the trigger block housing on by hand (in needs to be pushed down about 4-5mm) and then the two side bolts put in (no massive thread to engage and turn on this baby), trouble is the gun won't cock, the central piston road comes through into the trigger housing but the sear just won't engage, I trimmed off a bit of the rear guide thinking it was hitting the top hat on full compression and it did look like the rod was coming through the housing a bit more but alas no engagement, I've checked the spring and it looks like it's not been shortened as both ends look really nicely done (as if done by the factory), now all I can think of is either the kit is a dud (having the wrong spring fitted), its had the spring shortened by someone in the past and they've done a really neat job or someone has requested the kit to be a certain power and the spring was shortened by Vortek but not tested and sent to the customer and nothing done about it, that's the problem with not knowing about its history. I'll see if I've got another spring that will fit the kit, if not I'll get a new guide made up for the original BSA spring.

It's all fun and a little frustrating but a learning curve.

Pete

[Hsing-ee]

Theoben is on the back burner now mate, it's the Airsporter this time.

Bit of a strange one this one, when I received my Diana 34 a few years ago it came with a Vortek kit (not fitted) which I was told by the previous owner, that the rifle wouldn't cock with the kit fitted, I fitted it and he was correct, you could cock the barrel almost to the point where it should be catching the sears but it just had this soft resistance (as if plastic was hitting plastic), anyway that kit was put aside and forgot about and another kit fitted, roll on a few years and I was reading the thread going at the moment about are Vortek kits any good and I thought I'd see if my kit would fit in my Airsporter RB2 as the internal dimensions and lay out are almost the same, remembering the Diana 28mm piston seal will fit earlier 28mm Airsporters and Mercs, the RB2 being 29mm though being fitted with the later BSA parachute style piston seal, the kit indeed does fit, the outer sleeve even fits inside the piston but you just have to remove the BSA plastic piston sleeve, all that was needed was the rear part of the spring guide trimming down a few mm's to fit inside the trigger block, there is hardly any preload when fitting the kit and it's a simple case of pushing the trigger block housing on by hand (in needs to be pushed down about 4-5mm) and then the two side bolts put in (no massive thread to engage and turn on this baby), trouble is the gun won't cock, the central piston road comes through into the trigger housing but the sear just won't engage, I trimmed off a bit of the rear guide thinking it was hitting the top hat on full compression and it did look like the rod was coming through the housing a bit more but alas no engagement, I've checked the spring and it looks like it's not been shortened as both ends look really nicely done (as if done by the factory), now all I can think of is either the kit is a dud (having the wrong spring fitted), its had the spring shortened by someone in the past and they've done a really neat job or someone has requested the kit to be a certain power and the spring was shortened by Vortek but not tested and sent to the customer and nothing done about it, that's the problem with not knowing about its history. I'll see if I've got another spring that will fit the kit, if not I'll get a new guide made up for the original BSA spring.

It's all fun and a little frustrating but a learning curve.

Pete

When I had my Vortek kit for my HW30 I had the same problem, but I cannot for the life of me remember how I fixed it. There is some washer or spacer or something that stops the piston cming back the few extra mm needed. Keep going at it, you will find the answer.

[look no hands]

When I had my Vortek kit for my HW30 I had the same problem, but I cannot for the life of me remember how I fixed it. There is some washer or spacer or something that stops the piston cming back the few extra mm needed. Keep going at it, you will find the answer.

I've just removed a thing blue rubber washer type thing from inside the outer tube and it very nearly engages, I'm just in the process of drilling out the middle of a Welsh Willy Supersport tuning kit and hopefully that will fit

Pete

[TonyL]

Sounds like you're getting there, Pete.

The other night I came across an article on the Pyramydair Blog re mainspring shortening / scragging. Well worth a quick look at and you could measure the length of the compressed spring in a tool as detailed there (and also in one of Jim's articles in the past).

[maximus]

Does it work with no spring in, then you know if it's the spring or not.

[look no hands]

Does it work with no spring in, then you know if it's the spring or not.

I'm not even going to reply to that

Pete

[TonyL]

Does it work with no spring in, then you know if it's the spring or not.

I'm not even going to reply to that

Pete

Don't think he quite meant it like that, Pete.

Have you managed to sort it yet?

[look no hands]

Don't think he quite meant it like that, Pete.

Have you managed to sort it yet?

Nope, I even took the top hat off and a couple of delrin washers in the bottom of the piston to see if that was causing the problem but it still won't catch the sears, the sear is moving as the piston rod comes through the trigger housing but it just won't trip it onto the rod

Pete

[maximus]

I'm not even going to reply to that

Pete

I meant will the sears engage with just the guides in situ. Then you know if it's the guides or the spring, process of elimination init.