Hammer spring spec.

[Deejayuu]

Thanks for looking. Is there a standard spring for FAC please? Realise there's a balancing act with other factors but curious 'cos this Rapid has some bits missing and is FAC registered.
Spring length/rate would be an excellent, for me, start point

[Squinty]

yes and no.
iirc a full length single spring  is
72mm x 12.7 o/d x 1.42 wire 17 coils.
and dual rate.. coils closer at one end.
And that's a tad long

Kev and others order from the original supplier, you can go to Lee Spring ect and buy stock springs of similar dimensions but none of the ones I tried were quite right.

Can get better results from valves and airflow than by smashing it with a strong spring.

[Squinty]

BTW as yet I haven't chanced upon a rate for hammer or exhaust valve springs.
I asked KevG and his reply was... I just order mine from the original supplier.

A couple of years ago Bucketboy on t'other forum arranged a group buy from Vincent Springs.
I found the new hammer springs a tad firm for both sub-12 and FAC.
Could say the old springs have softened up but how would you order spring 'X' but with 15 years of scragging

Before you go down that route.....TRRobbs springs are awful.
The Vincent springs compress straight - linear, TRRs are too stiff, bow out and have a twang.

[Deejayuu]

Thanks, Squinty, for the full, informative, support.

[Deejayuu]

Squinty. I Assume the progressive rate spring needs close coils at adjuster end to give higher acceleration from rest.

[angrybear]

My last build I fitted one of TRR's short springs from a set I bought 8-10 years ago.
It's about 20mm too short, so un-cocked you can hear it sliding about inside, but it actually shoots fantastically 

[Squinty]

Squinty. I Assume the progressive rate spring needs close coils at adjuster end to give higher acceleration from rest.

you're probably right.
I assumed it was for less preload tension.
Shorter/longer- you can vary the hammer cycle depending on which end the close coils go.

My last build I fitted one of TRR's short springs from a set I bought 8-10 years ago.
It's about 20mm too short, so un-cocked you can hear it sliding about inside, but it actually shoots fantastically 

My mk2 177 spring is about 47mm, any less and Kev's double-tap bottomed out on its guide.