The International Cessna^® 170 Association

I am reading the IPC Pg 554 Fig 29-11

From the illustration I am noticing that the main spring has two bends formed at time of mfg.

The question now arises. The main spring sometimes breaks due to an imprint forced by the leaf above the main ( pg 54 Fig 29-12 0542105.)

Question where does the break actual occur? What is the distance from actual break to the natural lower bend in original spring?

Has anyone kept both parts of a broken spring?

Would you measure the broken spring part and advise?

Mine and all the other springs I've seen all look the same. Broke an the lower bend. May or may not have started by a stress riser caused by the upper spring. The spring will look fine one minute and the next it's broke in two. Usually happens in motion. Mine broke while my aircraft was tied down. My experience is unusual and if there had been a number associated with that break I'd have used it to play the lottery.

I'm sure a broken spring has been pictured here before. If I can find my broken one I'll post a picture.

]Bruce, thank you for insightful post.

A number of persons have apparently purchased the replacement main leaf just for prevention. Anticipation on a 60 year old active spring component.

Thus the question. Are there pictures of stress mark risers imprinted on the main leaf replaced?.

Your comment seemed to tie in stress at lower bend or a stress riser induced by upper leaf.

I guess at the end itis simply a time in service factor that would tell owner to replace.

When I replaced mine on 81D, there was a distinct wear mark on the main spring where the second spring ends.
I didnt take any photos tho and the spring had an unknown number of hours.

On 95D, I have the old main spring with about 900 hours on it - no noticeable wear marks.

A lot of factors will go into spring wear - the number of hours is probably the least important although easiest to measure.
I wheel land on paved surfaces so the spring gets very little wear compared to someone that three points it onto a river bank or taxis on unimproved surfaces.

But, its a cheap enough part to replace every 500 or so hours.

MoonlightVFR wrote:]...

Thus the question. Are there pictures of stress mark risers imprinted on the main leaf replaced?.
....

The above photo just looked like mine did . I was lucky to see there was a crack there but hadn't broken through . Why we started to look closely ? The bolts were rusty (corroded) and loose. All replaced with new and peace of mind . It's a blue aircraft and it faster than a red ones. All the upper springs were rounded edged .

ghostflyer wrote:.... It's a blue aircraft and it faster than a red ones. ... .

Only in the Land of Oz.