E3650 spring

[jrboon]

I would like to know if anyone knows the ft. lbs it takes to compress the E3650 spring or away to safely measure it?

[longislandhunter]

I've seen a Paul Capello video where he used a bathroom scale to measure the force to cock a rifle,,,, although I must admit it looked a little "awkward" to me.  

I can tell you that I've replaced a couple of the springs in my GAMO rifles with the E3650 and the cocking effort feels almost identical to what the stock spring felt like.....  maybe just a little lighter.  

Jeff

[jrboon]

I am wanting to find the ft.lbs to compress the E3650 spring not in the rifle.

[RedFeather]

How the Cardews did it in "From Trigger To Target":

Bore a hole in the top of you workbench, etc, to accept a long, threaded rod. Run the rod down through the spring and cap it off with a plate and nut. Screw an attachment on to the bottom of the rod to which you add weights. (Assume they used standard barbell plates.) Add until the spring is compressed. I would also use some sort of inner sleeve to keep the spring from becoming chewed by the rod's threads if it started to kink.

[djmyers]

Same thing redfeather said but you can also use a long eye bolt. Hook a digital fish scale to the eye and pull till compressed if you don't have weights. My scale has a handle big enough for my foot to go through, might need that I've never compressed one of these.

[shady816]

you know i never would have thought about that redfeather and djmyers but bothe ideas combined and a sort of comealong atached to the eye bolt to crank it down withe the bow scale would easily and safly make such a reading.

[michael90t]

it would have to be a pretty stout scale... I would guess its close to 150 or so pounds LOL

[shady816]

a scale used to measure compound dows draw weight would do it or a deer hanging scale both of which are inexspensive

[kiwi]

Post the specs and I will tell yer what its rate is...
free length / compressed length/number of coils/ wire dia / OD..
arround 140 would be a good bet

[RedFeather]

Stacking weight plates is a lot easier if you have some available. You could also try to search on the spring's specs.

[LongIslandArcher]

Jeff, direct in-line force to compress the spring is different than the force created by a cocking lever.  Whereas it takes 30 lbs of force to compress a gas ram (for example) with a cocking lever, I couldn't even compress the gas ram more than an inch when I put my entire body weight (165 lbs) directly over it.

[jrboon]

35 coils and wire .120

[kiwi]

JM - E3650 spring

ID - 0.515
OD - 0.755
coils - 35
wire Dia - 0.120
stacked length - 4.200 inches
spring rate - 32.5 lbs per every inch of compression

.........................................................
JM next closest  "more power"...

Universal 30 - 128

ID - 0.535
OD - 0.791
Coils - 30
wire Dia - 0.128
Stacked length - 3.841 inches
Spring rate - 43.1 lbs per every inch of compression

I could only work out the rate as a per inch figger..As I don't know the preloaded length
and fully compressed length of your gun....

As a rule of thumb..The more coils the softer the spring is for the same wire Dia...
 "leaverage angles on the wire"

Pete

[jrboon]

I tested today and I took the Gamo Big Cat spring and the Gamo Viper spring both took 180 lbs to compress to 98- 99% of their compression.
The E3690 spring was the same 180 lbs.
Now with this said my testing was not done with thousands of dollar equipment.
I fabricated a heavy metal dual post frame for which a 3" (bore) air cylinder set on top with a 16" stroke it was a little big a 2" cylinder would have done fine, apply pressure and watch the spring and scale.
At about 98-99% compression ( could see day light between coils ) my scale read 180 lbs and the air pressure gauge had 26 psi which when you do the math it comes up 183 lbs..
I know you want to know how I retained the spring.
I measured the id of the springs and used a .5 inche rod 14" long with a .250 thick x 1.00 OD washer welded on it.
This rod slides inside of another rod with a bore that is a little bit bigger which is attached to the piston rod of the air cylinder.
But like I said this is what I could come up with. Not laboratory testing.

[kiwi]

jrboon - 4/18/2010  3:47 AM

I tested today and I took the Gamo Big Cat spring and the Gamo Viper spring both took 180 lbs to compress to 98- 99% of their compression.
The E3690 spring was the same 180 lbs.
Now with this said my testing was not done with thousands of dollar equipment.
I fabricated a heavy metal dual post frame for which a 3" (bore) air cylinder set on top with a 16" stroke it was a little big a 2" cylinder would have done fine, apply pressure and watch the spring and scale.
At about 98-99% compression ( could see day light between coils ) my scale read 180 lbs and the air pressure gauge had 26 psi which when you do the math it comes up 183 lbs..
I know you want to know how I retained the spring.
I measured the id of the springs and used a .5 inche rod 14" long with a .250 thick x 1.00 OD washer welded on it.
This rod slides inside of another rod with a bore that is a little bit bigger which is attached to the piston rod of the air cylinder.
But like I said this is what I could come up with. Not laboratory testing.

WOW..I ran you numbers over my spring programme.....In some ways it exsplains a lot...
why  air gun springs fail/brake from time to time & lose power after a while...where most springs can run for 20+
years with next to know drop in force....

To get your numbers  I had to raise the temper rate on the programme up to 7.3 thats very high
compaired to the normal defalt setting of 6.8....
7.3 requires a normalizeing process of 9 hours at 310 degs....

Yep I think your numbers are right..And that exsplaines why air gun springs fail or lose power
To get the power from a spring of air gun size the temper has to be pushed to near the limit......

Pete