I was working on cleaning up the main gear, and was going to install a new coiled spring (p/n83302-40). I happened to measure the relaxed old spring at 4.7 inches. The new spring is only 4.5 inches long. So either a) the old spring is the wrong one, or b) the new spring was mis-marked, or c) the old spring stretched out which didn't appear to be the case as the coils were still tight. Any thoughts from our resident experts?

PatD

did you measure the OAL of the coils or the OAL of the spring...? 0.200" on a 4.5" spring is a tolerance that doesn't really surprise me. Most current spring technology is about 10,000 years old IMHO. Matt Kurke laughed at me, but I installed my last ones with the use of the shoestring out of the pair of New Balances I was wearing that day.

Jim

I measured just the coils.

John at Webco responded with "The only documented measurement I have is for the spring with a load test. At a tension load of 12 pounds the spring should be extended to 7-7/16 (+/- 1/8") for a service limit." I will be checking that this morning.

PatD

John is correct... static measurement for springs is incorrect... correct testing is a load test. If you think about it... you probably have 40 to 50 wraps on the static spring. The wire tolerance is probably +/- 0.002... 50 wraps with a 0.002 difference in wire diameter is 0.100" alone. Then if the set up person measures the load test and adjusts a partial wrap... it adds more variability to the static condition.

Considering the age of our aircraft... I would think that a wider tolerance on the load spec would exist. (And I would also expect you have a spec of stretching to a length and measuring load versus measuring load and then determining the resultant OAL.)