Re-engineering the Shift Spring

[footgoose]

 

 

50 for $50 is very optimistic.    

 

Uhh, yeah. Early on in this project, I think Scud was talking around $300 to get 25 made. I'm guessing the world demand is somewhere between 50-100.   There's not a lot of money to be made on Guzzi parts.. MGCycle wants $8.63 for it.

 

 

 

50-100 is just what I would guess as well. and $300 for 25pc sounds very reasonable. I would imagine a set up charge is involved too.

[Scud]

It was $300 for 50 springs, and $400 for 100 springs. This was to duplicate the original spring. I assume the price would go up a little for thinner wire with an extra loop (coil) - but maybe not. I think the expense is mostly in the labor.

 

Chuck - maybe you and I could talk about it next week after I get home from my trip.

 

I wonder if that place could make us a batch of sidestand wire loop thingies at the same time?

[Lucky Phil]

 

 

50 for $50 is very optimistic.    

 

Uhh, yeah. Early on in this project, I think Scud was talking around $300 to get 25 made. I'm guessing the world demand is somewhere between 50-100.   There's not a lot of money to be made on Guzzi parts.. MGCycle wants $8.63 for it.

 

Well I'll take 3, one for my fitted gearbox, 1 for my spare gearbox and 1 as a spare. I love spares. So thats 97 for the rest of the world:) 

 

Ciao

[Chuck]

It was $300 for 50 springs, and $400 for 100 springs. This was to duplicate the original spring. I assume the price would go up a little for thinner wire with an extra loop (coil) - but maybe not. I think the expense is mostly in the labor.

 

Chuck - maybe you and I could talk about it next week after I get home from my trip.

 

I wonder if that place could make us a batch of sidestand wire loop thingies at the same time?

For a low volume job like this, the money is in the setup. The wire is almost free. They probably have computerized coil winders, so not much labor once set up. That's how that 9 cents apiece for 20,000 parts factors in.

 

 

So $20 for a spring that won’t brake? 

 Oh, I'd make them all day for 20 bucks apiece.. but that sounds like work. Had a job.. 

Look, we don't even know if they will work in the real world yet. Our Southwestern testing division is on holiday..

[Chuck]

Final testing this morning on the Lifetime Guaranteed Imperishable Pawl Spring ™.

 

First, the stock Guzzi spring:

In neutral, 1750 grams

Upshift 500 grams

Downshift off the scale, but my fish scale   says 5 lbs. That translates to 2268 grams.

 

Now, the sacked 17000 mile Guzzi spring:

Neutral 1100 grams

Upshift.. absolutely nothing.

Downshift 2000 grams.

 

LGIPS: 

Neutral 850 grams

Upshift 400 grams

Downshift 1250 grams

 

Pretty easy to see why the Guzzi spring breaks on the down shift..and why the lever occasionally doesn't return to neutral on the downshift. There is a *lot* of pressure on the selector shaft. (no. 27 in the parts breakout) on the downshift.

 

I'll make a couple for Scud and keep this one for the Mighty Scura.

"King.. this case is closed."  

Maybe

[swooshdave]

I wonder if that place could make us a batch of sidestand wire loop thingies at the same time?

 

I wouldn't want those made unless they were better than the stock ones.

[swooshdave]

Final testing this morning on the Lifetime Guaranteed Imperishable Pawl Spring ™.

 

First, the stock Guzzi spring:

In neutral, 1750 grams

Upshift 500 grams

Downshift off the scale, but my fish scale   says 5 lbs. That translates to 2268 grams.

 

Now, the sacked 17000 mile Guzzi spring:

Neutral 1100 grams

Upshift.. absolutely nothing.

Downshift 2000 grams.

 

LGIPS: 

Neutral 850 grams

Upshift 400 grams

Downshift 1250 grams

 

Pretty easy to see why the Guzzi spring breaks on the down shift..and why the lever occasionally doesn't return to neutral on the downshift. There is a *lot* of pressure on the selector shaft. (no. 27 in the parts breakout) on the downshift.

 

I'll make a couple for Scud and keep this one for the Mighty Scura.

"King.. this case is closed."  

Maybe

 

So none of them have broke with your test rig?

[Chuck]

 

Final testing this morning on the Lifetime Guaranteed Imperishable Pawl Spring ™.

 

First, the stock Guzzi spring:

In neutral, 1750 grams

Upshift 500 grams

Downshift off the scale, but my fish scale   says 5 lbs. That translates to 2268 grams.

 

Now, the sacked 17000 mile Guzzi spring:

Neutral 1100 grams

Upshift.. absolutely nothing.

Downshift 2000 grams.

 

LGIPS: 

Neutral 850 grams

Upshift 400 grams

Downshift 1250 grams

 

Pretty easy to see why the Guzzi spring breaks on the down shift..and why the lever occasionally doesn't return to neutral on the downshift. There is a *lot* of pressure on the selector shaft. (no. 27 in the parts breakout) on the downshift.

 

I'll make a couple for Scud and keep this one for the Mighty Scura.

"King.. this case is closed."  

Maybe

 

So none of them have broke with your test rig?

 

Nope, but I *think* the original would have if it hadn't worn the test fixture down. 

Or not. Some springs don't seem to break.

Certainly, it is being driven well beyond what is considered "safe travel"  by engineering data. *Not* a good design.

The .071 spring is well within limits, and *I think* strong enough to do the job. 

Our Southwest "proving grounds" will tell us whether is is or not. 

[Scud]

I put the new spring in today. And here is the tale of three springs:

 

Top: New, super groovy custom hand-made by Chuck with just under 2.5 coils.

 

Middle: New Spring

 

Bottom: Spring I took out of the Scura - which probably has less than 2,000 miles and already showing sign of fatigue.

 

 

Turns out the Scura had a 16mm boss on the arm - but my spare pre-selector had a boss with 15mm. So I swapped them.

 

Also note how the short arm on the spring had cut in the metal on this part. When I previously did the polishing of the shift parts (per Lucky Phil's instructions) I neglected this part.

 

 

Polished part with rounded edge and new spring in place....

 

 

And what we really care about... does it work?

 

Yup. The good news is that I can't tell any difference in the shifting - and it was shifting great before. I am optimistic that we have solved this problem. My test ride was just 6 miles to do an errand. I will attempt to get in a few more miles ASAP.

 

 

[footgoose]

The "cut" in the arm worn in by the old spring was at least partially the result of the bind from the oversized boss. Good thing you got it out of there. The new spring with the extra coil, should be far less stressed, at least in the coil area. But that's not where they're breaking. It's usually on the shorter straight bit, near the tight bend (hook) isn't it? That's where the functioning abuse occurs it seems, as indicated by the cut, and the typical breakage. Torsion pressure combined with a twist at every shift. I'll bet that area will also benefit from some relief from the extra coil.

Wouldn't it be nice if, instead of hooking over the arm as it does, that end could ride perpendicular to a polished cylinder, like the other end does? Over thinking?

[Scud]

The short arm is one of two failure points, and I don't know which is more common. But Chuck noticed that the 90-degree bend in the short arm was tighter than "allowed" for that thickness of wire. He took care to give a bigger radius that bend on his new design. That, along with the extra coil and the thinner wire should solve the problem - especially if each person who installs one takes the time to smooth out the sharp edges on the stamped steel parts where the springs make contact.

 

That is an interesting thought about using another cylinder to eliminate the 90-degree bend - but that would require a higher degree of skill/customization than simply replacing the spring.

[Chuck]

Great news, Scud! Ilove it when a plan comes together. More field testing needs to be done, but I'm cautiously optimistic, too.

Here are the reasons for the design of the new spring.

(!) The reason for the breakage on the end. The Guzzi spring radius was stock thickness. Standard minimum bend radius is 1 1/2 times stock thickness. If you scroll back to the picture of the test fixture where I tested the new spring, I shimmed it out so only the end of the hook was on the pawl.. putting more torque on that hook. A more than worst case scenario. I also lengthened the short arm .1" to get it away from the radius where Scud shows the wear. I'm pretty sure that is the reason for the occasional shift lever sticking down on a down shift.

(2) Breaking at the coil is a no brainer. Guzzi is driving the spring 39 degrees. The spring calculator says safe travel is 30.48 degrees from memory. The new spring is well within safe travel. You can see the effect of over driving the spring in the picture Scud posted. By this time, there is *no* spring pressure on the upshift, and the eccentric adjustment controls how well it shifts.

Off to breakfast. Carry on, Mr. Scudder.

[Scud]

It occurs to me that the many changes to the pre-selector over the years were not needed. All that was needed was a better spring. My 2002 preselector has no eccentric to adjust the pawl lever - and with the new spring in place, that lever doesn't bounce up and hit the fixed pin anyway. The new spring applies more even pressure on upshifts and downshifts - more than stock on the upshifts and less than stock on the downshifts. I didn't miss any shifts... more testing soon... then I'll order a batch for us.

[footgoose]

Thanks for 'splainin that Chuck. And thanks Scud for getting this under testing so quickly, and documenting.

[motortouring]

Can I still jump in for 2 pieces?