On Mon, 14 Dec 2009 13:41:54 -0600, "Pete C."
wrote:


I need help in selecting an extension spring to counterbalance most of a
3.5# load over a hair less than 1" of travel. The 3.5# load needs to
rest solidly against the bottom stop at rest, and I need most of the
3.5# load counterbalanced through the 1" stroke, so it seems I need a
spring where the rate will not change significantly over that 1" travel.
I have a good amount of room to mount a fairly long spring, up to about
5" contracted length.

I see plenty of springs on McMaster to choose from, but I'd like to be
able to order the correct spring the first time.

Thanks!

You want the spring with the lowest spring rate (pounds/inch) that
will support your load in the space available. Some of the spring mfrs
have selection tools online that make it easier to zero in on a spring
than McMaster. This will give you enough information to go back to
McMaster to see if they carry something close enough.

For example:
http://www.centuryspring.com/Century...ion_search.jsp

Associated Spring and Lee Spring are two other places to check.

--
Ned Simmons