Chuck

Scud.. if Footgoose thinks a 25% reduction in spring pressure is causing the quick shift issue we should hold up on making the new springs. We're over that..

The bend radius for music wire is 1 1/2 X the diameter. On the one I have, it is 1X diameter. That could be why they are breaking there.

Sounds like a plan. Don't forget the 1 1/2 dia bend radius on the short leg.

I want a spring that won't break, too. Let's go with the 895 degrees. I'll split the cost with you so if this is a bust we each only lose one fiddy. I think it's worth the gamble. Oh.. I don't suppose they'd make a couple so we could test to destruction before the order? If we *knew* they would work, we could order more than 25.

You would look good on it, Scud..

Ok using 1.52 active coils, the rate is only lowered fractionally @33.22 N-mm/degree Safe travel is 30.89 degrees. I'll be back with what smaller wire could do. Edit: Ok, I'm back. Using .071" wire with 2 1/2 active coils, which gives (in my opinion) enough clearance to not bind.. and is readily available. Rate is 20.68 N-mm/degree Safe travel 49.51 degrees. That sucker wouldn't break.. if it is strong enough to do the job. That would be 1.8 inch lbs per degree compared to 2.9 with the 2mm spring. What do you think?

Here's the spring I preemptively replaced at about 16000 miles. As you can see, it is already at 12 degrees deformation from over travel. It would have broken sooner or later. Probably sooner. I would say that even at 15 degrees, we would be operating at the limits of the spring. If we are going to go to all this trouble (fun, actually) we should come up with something that won't break in normal service. I'd like to see a good safety margin. How about stacking some feeler gauges in there to see the biggest diameter wire we can use? Then we can plug 2 1/2 coils in the calculator and see how much torque it would have with the smaller diameter wire. 2017-11-09_10-39-44 by Charles Stottlemyer, on Flickr My gut feeling is if we can't get another turn, we should at least explore the extension spring.. even though it would involve considerably more development to come up with something the home mechanic could do.

Well, now at least we know why they are breaking at both places. Normally Guzzi engineering is good (except for 4V valve trains) Maybe the same guy designed this spring, too? I take it there is no room to wind another coil on it?

Scud was right, it has 1 1/2 active coils. My bad.. That changes the Guzzi spring to a safe travel of 30.48 degrees. This is using the ASTM A228 piano wire.

Piano or music wire definitely has standards. All I've been saying is detailed in my ancient (naturally) copy of the mechanic's bible. The composition of the alloy, and how it is manufactured. There is a whole chapter on making springs. This stuff isn't rocket science. It's been known before the turn of the last century. 2017-11-08_12-50-01 by Charles Stottlemyer, on Flickr

Ah, one other thing. I was thinking that if we solved the breaking at the coil by whatever method.. why is it breaking at the bend on the short end? I wonder what minimum bend radius on music wire should be.. so looked it up. 1 1/2 stock thickness. The one I have is .078" as nearly as I can measure, so is well *under* the minimum bend radius of 3 mm. (.118") That could explain it.

^^^^^Where did you come up with that? Uhhh, there are standards for piano wire that have to be met. For instance for 304 stainless wire.. If there were no standards, making a spring would be a crap shoot.

Just for giggles, I ran the numbers with 2 active coils instead of 1 and got 48 degrees safe rotation. Don't know if there is room for that or not.

Ok, here is some preliminary data. The stock Guzzi spring wire is 2mm dia. Spring rate/degree is 45.1 Nmm. Torque max is 1036.8 Nmm. Max safe travel 22.9 degrees. Running the numbers on .005" bigger in diameter: Max safe travel 20.91 degrees .005" smaller.. 24.04 degrees. Interestingly, common music wire is only good to 300 degrees F, while stainless 304 is 570 F. So. Before we can go any farther, we need to know how many degrees of rotation the preselector uses..

What makes you say that? It "appears" to be the new 6 speed. (?) But then, we are looking at a prototype..

Great idea! After all, we know Guzzis are all about lightness.

Do you have a spring on hand that you could measure and use their online calculator? If not, I could post some measurements. I think that with your experience you might make a better decision than I would. I'm kind of limited to: "Here's a spring. Can you make me one just it, but better?" Yeah, I do. It's used, though. Actually, "just like it but better" could very well be the answer. Higher spec wire, maybe better coil winding machinery. I don't have access to a spring winder any more, and making them on a mandrel on the lathe is a PITA. I'll make that today's project.. if I get time. Quite a bit going on right now. I have a new pup out in the shop and oiler nozzles to make.

The V9, when introduced. had a boss in the center like they were planning a 4V from the beginning. I've read 5V..maybe. A new LeMans would be what it takes to get me to open my wallet, but I may be too old to ride it by the time it comes to fruition. I'm still waiting on the Ippo.

I have some experience with springs..

That helps but you also need to know what material and tempering you want. One of the things you can calculate on a torsion spring is music wire.. that's what Scud is looking at. Thought it might give an optimum dia. etc.

This might be instructive.. https://www.acxesspring.com/torsion-spring-calculator-instructions.html

Piano wire would be good. I think I smell something,too.. oh, it's just a smellfie. I'd go with the spring manufacturer's recommendation. Piano wire, music wire.. same same. https://www.mcmaster.com/#piano-wire/=1a5kz24

In this thread alone, there are pictures of the spring breaking in different places. That hints at a metallurgy/heat treat problem to me. A simple spring like this should be able to be wound from music wire, and be bullet proof, I would think.

Probably translates to twin cylinder 5 valve. If so.. I hope they have finally gotten it right.

"If" there is room, an O ring on the pedestal would cure that leak. Probably, that isn't an issue if we decide to go this way. I think Chuck to do the post on the selector cover "right" you're going to need to spot face the cover around the hole so the post sits perpendicular. If you do that then the post can have a wide integral flange that can be sealed effectivley with some loctite or sealant on the flange face. Not that keen on the post bolting to the less than flat internal cover plate face. Ciao Spot facing would be ideal of course. That was why I mentioned an O ring groove in the pedestal. We're still too early in this "design meeting" to worry about that, yet.