Using A Very Very Short Spring

[Nathan1991 25]

Hey guys,

 

As many already know I have recently bust a mainspring in my hw35. The break is closer to one end and around 6 coils has detached. I noticed that the spring was extremely stiff and I couldn't help but wonder what would happen if I re-finished the snapped end and used nylon spacers in the place of the detached coils and placed it back in. I am experienced at airgun repairs but sometimes curiosity takes over I thought it could produce a more efficient stroke due to the less coil resonance as it releases its energy. I dunno might just be being silly any comments welcome guys as long as there not to harsh.

 

ATB Nathan

[moxy 617]

Try it, you wont know until you do

[Nathan1991 25]

I know moxy your right, in theory it should work it just means the duration and distance of spring travel is reduced so it would produce a more responsive stroke if you know what I mean

[moxy 617]

Did you chrono it before the spring broke, and did it kick like a mule?

[Nathan1991 25]

Yeah it was chronod and was 9.8 before the break, I would love to get it into the 11's and also keep the low recoil but due to the 35mm stoke length it's proving to be very difficult

[barrywhite 282]

did you heat the spring in your gun. if you did that is most probably why your spring snapped heat treating a spring is an exact thing .I once read someone claimed to get a very good shot cycle from a very tuned old bsa meteor .they made a different piston, changed the sweep volume, lots of thing I cannot remember but one thing they did that gave superior performance was a very short ox type spring when fitted it had little to no preload but the piston was weighty .

[Nathan1991 25]

That's interesting about the piston and yeah when i first got the rifle it was majorly oversprung so I removed around 5 coils, collapsed them using a blowtorch and quenched it in oil. I then refinished the spring until it matched the weihrauch end. I might start totally experimenting to see exactly what can be achieved

[barrywhite 282]

I have wondered how good this collapsing a spring is going to be .To harden and temper spring steel the metal of the hole spring has to be heated to an exact temperature and cooled fast then the hole spring is heated to another temperature then cooled fast .these temperatures are exact .The process is called hardening and tempering .heating the metal randomly will change the properties of the spring . The hardening and tempering can be a little different with metals of different alloys but the process is still similar and random heating and cooling of a finished spring will destroy it .thats what I have been taught and understand .

[Nathan1991 25]

Good evening Barrywhite,

 

This may be why the spring snapped after resizing. What is your opinion on installing an exceptionally short spring (16 coils)? And making up the lost space with steel capped with nylon. Could it produce a more efficient cycle do you think?

ATB Nathan

[barrywhite 282]

if you put weight and packing into the piston it may work , but the rest of your spring may fail .you wont know until you try if you have an xs springs or an ox spring I would think you have a chance .

[Nathan1991 25]

That's what I thought, cheers Barrywhite

[Tron 173]

Nathan, the HW 35 is quite capable of 11fp+ the real limiting factor on that model is the length of the transfer port plus the swept cylinder capacity. Because of those facts fitting a strong spring usually makes for sharp recoil because the piston doesent have that last bit of air cushion to prevent piston crash. I believe you will have to work out if is worth going the spacer route or maybe just get a shorter stiff spring that just preloads the piston by the length of 2 coils or so. Good luck.

[Nathan1991 25]

Hi tron,

 

Thanks for your reply, To increase sweep length there is a huge amount of complex work that would need to be done which includes reducing piston sear length and increasing the cocking lever length. You could be right about the recoil and it may be the best idea to buy a new spring.

 

ATB Nathan

[nicknack 0]

I had a HW once - super looking thing in walnut but was very low power ...the spring was 'right' and full length ....but only gave 5ft/lbs . I toyed with all manner of theories , but in this case , I think nlyon may not be sufficient . If you are replaacing spring length by this much I am guessing asI have never tried this [ but have pondered the same myslef ] , possibly a soild bar of ally or brass with a nlyon finish may be better when compressed ?

[rubbergajo 0]

There are so many other variables at play that I would prefer to fix the wheel over reinventing it.