Re-engineering the Shift Spring

[Chuck]

 

Gave up this afternoon at 289386. It wasn't going to break.

One thing that is difficult to design against is vibrations. Could the spring buzz itself to death? Are there any wear marks where the spring sits in the shifter mechanism?

If, for example the spring resonates at 4000rpm, then the fatigue cycle count could get into very high numbers without much shifting. Changing the resonance frequency could make a steel spring last forever if the design stresses were below the fatigue limit. A resonance change could come from different thickness wire, different length spring, different oil in gbox. 

Just a thought. I know it doesn't help your design, but it may explain why you can't break that spring by shift cycles alone.

 

Interesting thought, but beyond my meager ability to test.

Wear marks? Very subtle. I had to look at the used one with a 10X glass to make sure it wasn't new when I first looked at it. Then, when I took the new one out of Scud's preselector, I could see the old one was sacked when placed side by side.

[Chuck]

Sorry, I've been slackin today.. and will continue slackin until this stretch of warm weather goes away.

[Lucky Phil]

I'm tracking and learning. So the .071" wire with 10 degrees less than 2.5 coils (890 degrees of coil). While this configuration gives less torsion on downshifts, it gives more on upshifts... so the torsion is more uniform across the range. That's what we get with a little more "preload" on a thinner wire. Is that right?

 

My oldest daughter's boyfriend is studying mechanical engineering. He is entertained by this topic... too bad he is not a motorcyclist.

 

Thats not a bad srike rate Scud, 2 out of 3. Mechanical engineer,entertained, you can work on the missing piece:)

I've said more than once that I dont need to be the smartest guy around because I know smart people to ask. This thread proves it.

 

Ciao 

[Scud]

The boy surfs though, so we can give him 3 out of 4.

 

@Chuck - keep slacking (which I hope means riding) during the good weather.

 

I will gladly install a prototype spring in my Scura and go give it a real-world test. It might take me a while to get to 200,000 shifts... But, I think I could temporarily mount a mechanical counter on the sub-frame so it counts the upshifts in real-world riding. I assume there would be different shifts per mile in twisty mountain roads vs. commuting vs. touring.

[Chuck]

I can send you my best guess spring if you want to do some real world testing. Right now, I'm riding (fabulous day today) and doing an annual inspection on the Colt. My lovely assistant helped me get the cowling off without damage this afternoon   to start on the "powerplant" part of the inspection.

2017-11-29_08-08-00 by Charles Stottlemyer, on Flickr

[docc]

* Now, I'm havin' trouble feelin' sorry for ya there, buddy. Ya had me goin' for a while . . . *

[Lucky Phil]

I can send you my best guess spring if you want to do some real world testing. Right now, I'm riding (fabulous day today) and doing an annual inspection on the Colt. My lovely assistant helped me get the cowling off without damage this afternoon   to start on the "powerplant" part of the inspection.

2017-11-29_08-08-00 by Charles Stottlemyer, on Flickr

Chuck, check the engine oil qty, there's none on the floor, must have run out:) 

 

Ciao

[Lucky Phil]

The boy surfs though, so we can give him 3 out of 4.

 

@Chuck - keep slacking (which I hope means riding) during the good weather.

 

I will gladly install a prototype spring in my Scura and go give it a real-world test. It might take me a while to get to 200,000 shifts... But, I think I could temporarily mount a mechanical counter on the sub-frame so it counts the upshifts in real-world riding. I assume there would be different shifts per mile in twisty mountain roads vs. commuting vs. touring.

Yea, extra points for surfing, I can see that. Same as points for playing Guitar and speaking a second language:) None of which I can do, or the surfing for that matter.

 

Ciao

[Chuck]

 

Chuck, check the engine oil qty, there's none on the floor, must have run out:)

this engine is amazing. When I bought the project, it had the original engine. 1800 hours since new, 300 since a top overhaul, and had been sitting for years. Because of the cam sitting high in the case, they rust cams and lifters when not in use.  It was of practically no value. cheap. (Guzzi content)  I pulled it apart, cleaned light surface rust off the cam and lifters, reassembled with all new gaskets, put an oil filter mod on it, and it runs like new. Burns a quart in 14 hours.   Doesn't leak. (!) Sometimes, you get the bear..

[Lucky Phil]

 

 

Chuck, check the engine oil qty, there's none on the floor, must have run out:)

this engine is amazing. When I bought the project, it had the original engine. 1800 hours since new, 300 since a top overhaul, and had been sitting for years. Because of the cam sitting high in the case, they rust cams and lifters when not in use.  It was of practically no value. cheap. (Guzzi content)  I pulled it apart, cleaned light surface rust off the cam and lifters, reassembled with all new gaskets, put an oil filter mod on it, and it runs like new. Burns a quart in 14 hours.   Doesn't leak. (!) Sometimes, you get the bear..

 

Sound like you got a good one there Chuck, unlike the old P&W radials I worked on as an apprentice. They used to leak more oil than they burnt. If they weren't leaking you got worried:)

 

Ciao

[gstallons]

That is comforting .

[Chuck]

 

 

 

Chuck, check the engine oil qty, there's none on the floor, must have run out:)

this engine is amazing. When I bought the project, it had the original engine. 1800 hours since new, 300 since a top overhaul, and had been sitting for years. Because of the cam sitting high in the case, they rust cams and lifters when not in use.  It was of practically no value. cheap. (Guzzi content)  I pulled it apart, cleaned light surface rust off the cam and lifters, reassembled with all new gaskets, put an oil filter mod on it, and it runs like new. Burns a quart in 14 hours.   Doesn't leak. (!) Sometimes, you get the bear..

 

Sound like you got a good one there Chuck, unlike the old P&W radials I worked on as an apprentice. They used to leak more oil than they burnt. If they weren't leaking you got worried:)

 

Ciao

 

Oh, I have a radial in the shop. It's a 90 hp Lambert. 1930. It was overhauled, test run, oil drained and pickled in the late 90s. Supposedly, there's no oil in it, but there are a *lot* of oil spots under it.    

[Chuck]

Ok, back at it. It was too cold to play this morning. Welded a couple of wear pads on the lever, and am currently testing the limit of the .071 spring wire. It has 28 degrees of preload, and maximum safe travel is 60 degrees, according to the spring calculator. 28+39=67, so we'll see if this sucker breaks or takes a set.

The Guzzi 080 spring with 1 1/2 coils has 1250 grams of pressure on the pawl in neutral, and essentially nothing at the limits of the upshift.

This spring has 1150 grams in neutral and I haven't measured at the limit of travel, but it's substantial. 

The .071 spring with 5 degrees preload has 700 grams of pressure, and still has positive pressure on the upshift.

I'm thinking that we'll probably end up with an .071 spring with 10-15 degrees preload. We'll see how well the over stressed test works out.

2017-12-01_12-05-29 by Charles Stottlemyer, on Flickr

 

I hear the Scura calling. Time to go for a ride. 

 

[Scud]

Again... this is just so interesting. Again... thank-you.

 

It is almost impossible to resist the Scura's call. But unlike the false promises in the sirens' songs, the Scura delivers.

[swooshdave]

Again... this is just so interesting. Again... thank-you.

 

It is almost impossible to resist the Scura's call. But unlike the false promises in the sirens' songs, the Scura delivers.

 

Until the spring or clutch breaks.