Broken Shift Spring

[hgravelpha@aol.com]

I work for McMaster-Carr Supply Company and I can have our supplier manufacture this spring in a small batch quantity. I can have them manufacture to our specs, i.e. stronger material and larger wire diameter. I just need to know the right part number to order from Guzzi so I can send it to my manufacturer. I will also need help from you all on what improvements should be made to this spring before I have a batch produced. If the cost is relatively inexpensive, I will make these as a gift to you all. If the cost is beyond a couple dollars each, then I would have to shift the cost to you. The initial batch have to be more than 50 each.

[Baldini]

Thanks for the offer .

 

Part no is: 04 23 83 00

 

Re modifications, I'd be happy w/ same design if it didn't break!

 

Ir's not clear why the springs break. Material, manufacture or design? Maybe a thicker material is necessary. Can that be done w/ same design w/o making it stiffer?The spring material could not be thicker than the width of the pin it locates against on the ratchet arm.

 

It may be that the spring would be less stressed if the radius of the 90 degree bend was larger.The spring tends to slide sideways in use, away from the plate it locates on at it's lower end. A larger radius on the 90degree bend at this point would make it slide further (there is nothing to retain the spring on the plate if it slides too far). However, a larger radius here, with the short arm continuing thru 180degrees, so that the spring wraps around the back of the plate would mean it couldn't slide right off. The plate edge could also then be radiused ?

 

I'm no engineer, any other comments ? Anyone got one apart at the moment?

 

Cheers, KB, Cymru

 

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[Guest captain nemo]

This sounds fantastic. If we could as a group create a proper design for this lemon item it would be a great help to not only us, but the millions of poor souls who will one day come here with their many many problems. I have my wallet right here. Let's all do this.

 

In fact, think of it: If this company can redo THIS part, what else could they redesign according to OUR specs? We have some good thinkers here. Perhaps this is a source we should check out.

[jrt]

That is very kind of you. Thanks for looking into it. I would certainly be willing to buy one or several if you have them made.

 

Cheers,

Jason

[docc]

I'm still of the opinion if we make one spring we should make a set of three.

[Paul Minnaert]

I do have a special made spring. I got that from Roland Wienberger. What is different, is the small end thats angled at 90 degree, the curve is much wider made.

[Baldini]

Paul,

 

Do you think it is the design, the material, or both that is at fault in the original spring? Was the spring known to fail on the Daytona?

If the radius on your spring was continued thru 180 degrees & stopped it would provide a more secure location, the larger radius will encourage the spring towards the edge of the plate in use. What do you think?

Is your spring heavier gauge? It appears to have an extra coil? Have you many miles on one? Are they available?

 

Thanks, KB, Cymru

[hgravelpha@aol.com]

Paul, If your spring is a better design, can I borrow it so my supplier can copy it. My supplier is in the east, so this process may take several weeks.

[Paul Minnaert]

I think the spring is originaly bent to sharp. And there is an aditional coil. The gauge is the same. This spring is only on the 6 speed boxes. so not on the daytona. But I bought a scura with clutch problems, and got an extra spring with it. Roland, who made it, has driven several thouand miles with it, without problem.

Since I'm in europe, I don't want to ship the spring, the post might loose it. I can make a drawing. And I still have the original spring in my 6 speed box, I want to keep the spring nearby,just in case:-)

[docc]

may take several weeks.

"several weeks" : a phrase used by Guzzisti meaning " in the blink of an eye."

[hgravelpha@aol.com]

I will order the part today. My supplier suggested that we use 1065, 1080 to 1090 carbon steel with a phosphate and oil finish. The specs on these wires are - max temperature 300 F. and the tensile strength is 147,000 - 399,000 psi. He also recommended type 316/316L stainless steel if it was in a corrosive area. The specs are max temperature 400 F and the tensile strength is 312,000 psi. I'm thinking we should use 316 stainless. Now I have to wait for the Guzzi dealer to send me my spring so I can send it to my supplier. Please give me your $.02 about the type of steel to use.

[Baldini]

What does your supplier think of this spring design in this application - if well made, is it up to the job or does it need redesigning?

 

Unfortunately I know nothing about metallurgy - maybe someone else out there? The spring is within the gearbox so I wouldn't have thought corrosion would be an issue.

 

Thanks for your efforts, KB, Cymru

[docc]

The first metal seems to have such a broad range in tensile strength. If we are going to the trouble i think we should build the best spring possible.

 

Again, if I were taking my box apart again I would want to relace all three springs and the follower for the indexing pawl ( " MG: neutral indicator") While no one has reported any trouble with the 'middle' spring i still maintain the strength of the 'right' spring is suspect perhaps contributing to false neutrals and missed gears so often reported.

 

What would it take to make a new set of springs?

 

I will be happy to donate the stock parts as I have them in hand and can send them tomorrow.

[emry]

While my orginal spring has yet to break; 5.5k miles, ( I Know I need to ride more often) I would happily chip in to help the development of the bike.

I would think that the 316L would be overkill, the corroison properties are the main benefits and usually only out weight the cost when that property is needed. The 1065 or the 1090 should work just fine, both are often used for automotive valve and suspension coil springs respectivly.

Just another note, tensile strength denotes how much force it takes to lengthen or stretch the given material, not break it. Yeild stregth is the amount of force it take to permently deform a sample and Ultimate stregth is just that. (Anyone got a welder handy )

Does anyone have a picture of a failed spring for us to look at or a description of where the failure normally occurs?

[Guest northend]

Is this spring the cause of my shifter sometimes sticking in the down

position???

 

Sometimes under hard acceleration or down shifting. Usually poping

the clutch a little frees it up

 

If this is the case, should'nt the spring be a bit stiffer???

 

Regardless put me down for a set .