Re-engineering the Shift Spring

[nobleswood]

 

Will the springs need any post-treatment?

 

 

I doubt it will need stress relief. Most springs aren't. We'll find out after a few 10s of thousands shifts., *assuming* the gearbox of my little low speed motor holds up.

Chuck,

Did you rig up a test bed motor that will operate the gearshift some 10s of thousands of times to test the new spring ?

[swooshdave]

 

Chuck,

Did you rig up a test bed motor that will operate the gearshift some 10s of thousands of times to test the new spring ?

 

 

He said this morning that he would work on it over the holidays.

[Chuck]

We had company this weekend, but got out there and hit it this afternoon. Found some bearing bronze bushings, I'd already made one for the lever pivot, forgot to take a picture. Made the cam.

2017-11-25_04-52-34 by Charles Stottlemyer, on Flickr

2017-11-25_04-52-52 by Charles Stottlemyer, on Flickr

Trial fit up and everything works. Even a blind hog finds an acorn now and then. 

2017-11-25_04-52-09 by Charles Stottlemyer, on Flickr

Made a coupler out of some ever present Delrin.. no picture again.. and hooked it up.

Here are the springs to test. The Guzzi spring is in the center, .080" springs at the bottom, .071 springs at the top. Various amounts of preload.

2017-11-25_05-45-36 by Charles Stottlemyer, on Flickr

Merrily clacking away, shifting 8600 times per hour.

2017-11-25_04-51-30 by Charles Stottlemyer, on Flickr

Liberally squirted a mix of STP and 15-15 syn on moving stuff.

I hope this isn't just a test of my low speed motor or gearbox.    It was getting pretty warm after a half hour, so put a box fan on high pointed at the whole works, and now just have to be patient. 

Any takers on how long the Guzzi spring will go?   

[nobleswood]

My question was not about when he was going to but was he going to.

 

Chuck approaches these tasks with such a professionalism that I can’t help

but grin about how he tackles the problems that We encourage him into.

 

I enjoy learning from the man and his well documented tinkering. Thanks !

[footgoose]

metallurgy question. Do hot and cold cycles affect strength/life? not that the tranny gets that hot.

[Chuck]

metallurgy question. Do hot and cold cycles affect strength/life? not that the tranny gets that hot.

 

Yes, they do. Generally, it's for the better, though. In aluminum. Not so much for spring steel.   Stress relieving temp is about 350-400 F. I seriously doubt that the spring in a transmission gets that hot, though. That reminds me, It's been a little over 17000 shifts, now.. maybe I better go out an take a look.

[docc]

We've moved waaaaaaaaaaaaaaaaaaaaaaay past hammers here, boys!

 

Makes me want to load up all my fire extinguishers in the Jeep and head north . . .

[brubache]

I have no words.  Wow.

[Scud]

Were you testing one of the new springs with 2.5 +/- coils? 

 

I'll guess the original spring breaks at 15,000 shifts. Total WAG. And I bet the ones with thinner wire and 2.5 coils will go beyond 75,000 shifts. Again, total WAG... but thought I'd throw something out there for entertainment value. That, and bumbling along until Chuck couldn't stand it anymore and decided to take over are my two primary contributions.  

[Chuck]

Stop the presses. I went out to check on it before going to bed, and had a squeak from the gearbox. Maybe (hopefully) just low on oil, and not a gearbox rebuild.   

At any rate, shut it off and will look at it today. At that point, the Guzzi spring still looked good, surprisingly enough to me. 5 hours so far.

[docc]

Does this spring deflect the same direction/distance on both the upshift and downshift?

[Chuck]

No, it is almost completely relaxed on the upshift.

[Chuck]

Scud.. if you had installed the spring you sent me, you wouldn't have broken it. It now has over 100000 shifts, and seems to be indestructible. I'll let it go all night and see what happens. 

[Scud]

Well, hopefully the one that went in the LeMans is the same and it will be trouble-free for the new owner. Does it even show signs of fatigue? Each spring I have replaced had relaxed/deformed a bit - making it look like about 1.6 coils instead of 1.5.

 

I bought a few springs from various sources. I wish now I could say which spring was from which source - but I didn't keep track. And not all springs break, right? Some people have plenty of miles with no failures. Part of the issue could be defects in materials and/or workmanship (such a tool mark at the bend).

 

It still seems that we have identified a flaw with the over-extension of the spring, which is worth correcting. If memory serves me, I have broken three of these with only about 30,000 miles on V11s. Those aren't good odds for a crippling and inconvenient failure. 

[Chuck]

 

Does it even show signs of fatigue? Each spring I have replaced had relaxed/deformed a bit - making it look like about 1.6 coils instead of 1.5.

No. (!!) Believe me, I'm surprised. I toyed with putting it in the preselector and testing how much spring pressure it had, but decided to wait until tomorrow morning if it hasn't broken. Honestly, I would never have believed it would go this long. It's eating up my steel lever, and just keeps on clacking..