Running Springs In Series

[5252]

I'm new to modifying guns (and this board), but not coil springs. I read through some of the FAQ threads on springs.

I haven't seen anybody report about running two different weight spring in series. Maybe I just didn't search good enough. Anyways, has anybody done this?

In my non-gun world (racing cars), you often use a "main" spring (high rate) and a "tender" spring in series, seated with a little spacer between the two to mate them together (end to end).

Here's the math:

M = main spring rate

T = tender spring rate

Initial rate = (M*T) / (M+T)

Example:

M = 12

T = 6

(6*12) / (6+12) = 4

Summary: The initial rate of two springs in series is less than the rate of the lightest one.

There is, however an inflection point (bump in rate) to the higher rate spring (in this case 12) after the lower rate spring is fully compressed.

The lower rate spring is typically a flat-wire spring, optimized for coil bind. I noticed that in my CZ SP-01 the stock spring is a flat-wire type. The Wolff springs I've purchased are standard wire.

Either way, it makes sense to me that it would be preferable to deal with the inflection point in two-spring setup than to rely on a buffer (e.g. "bump stop"). The buffer is really nothing more that a second spring, but of a much greater rate.

If you could set up the gun with two springs in series where the main spring almost (but never does) coil bind, the felt recoil should be minimized. I don't, however, know if this is possible.

And yes, I'm sure this is what the fancy spring systems are probably doing. Bottom line, though, I think I'll machine up some spacers/seats and start experimenting.

[BritinUSA]

This is pretty much the way that the STI RecoilMaster and Sprinco recoil reducers work.

Wolff make variable strength springs that work in a similar fashion, they unlock quicker and slow the slide down toward the end of travel due to the increased tension at the end.

[5252]

This is pretty much the way that the STI RecoilMaster and Sprinco recoil reducers work.

Wolff make variable strength springs that work in a similar fashion, they unlock quicker and slow the slide down toward the end of travel due to the increased tension at the end.

Yep, makes sense. What doesn't is the cost. If a simple spacer works well, then we're looking at a trivial expense. And the ability to "tune" it to your needs. I'll certainly report back with details as I pursue this.

Edited August 3, 2006 by 5252

[shred]

I know people have toyed with them.. seems like the problem often is the reverse plug is long enough that it will disagree with spacer washers-- it almost completely covers the spring in full travel, so unless the second rate spring is very short or nested with the first a-la Sprinco and STI, it may bind on the spacer. If you make the spacer small enough diameter then loose spring ends can escape over it and tie everything up.

[.40AET]

I was bored 2 winters ago and played around with this idea. At least the springs are cheap. I couldn't get something reliable enough to trust in competition. Not to mention, it didn't feel that much different than a standard spring.

Have fun with it.

[eric nielsen]

Do a search on Recoilmaster and Sprinco & you'll find where a few people did try that. I remember the trial & error part, don't recall hearing back about a successful setup.

That search will also turn up a gut-wrenching variety of horror stories. I read thru them for more than 2 days and at the end I was quite happy to use a 9lb Wolff spring and one EGW buff for Open division.

[Front Man]

The variable motocross springs we used back "In The Day" work just like the variable wolf springs we use in our blasters today.

Maico Rules!

Damn, it's 2006 not 1981!

FM

Edited August 4, 2006 by Front Man

[Josh Biondi]

try with recoil master or Sprinco......

[Larry White]

You cant tune anything until you can make it do the same thing every time. A IMSI recoil spring in the correct wt. with a plain steel guide rod is the most bullet proof set up out there.-------Larry