Re-engineering the Shift Spring

[Chuck]

Yes.

[motortouring]

 

It's just play money, Docc, and everyone knows that play money doesn't count.

Count my PlayMoney in, then . . .

 

Seriously, though, if the product doesn't fit the working drawing, the manufacturer *should* square it away, yes?

With docc

 

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[Lucky Phil]

I'm with the share any additional cost and do it right position, so count me in on that. I mean "should be ok" has its place but when you're trying to overcome a cronic issue its not really where you want to be.

 

 

Ciao

[Chuck]

The old tool room adage, "There is never time to do it right, but always time to do it over" applies. Certainly 15 degrees too much coil is cause for rejection. We have enough experience with an over driven spring.

[swooshdave]

The old tool room adage, "There is never time to do it right, but always time to do it over" applies. Certainly 15 degrees too much coil is cause for rejection. We have enough experience with an over driven spring.

 

I wonder if the manufacturer stated what their production tolerances were?

[Scud]

I think the manufacturer will work with us. The rep responded by e-mail that they have a 10 degree production tolerance. I measured that they were off by 15 degrees, so they are beyond their own stated tolerance.  He offered to rework the original material, but I don't think we should accept that - I think we need to prove this design with material that has been shaped only one time. 

 

I'll try to talk with him tomorrow and figure out the options.  Given the difficulty of replacing this spring, and the "chronic" nature of the problem, I think a re-run with new material is our best bet.

 

Perhaps we should be prepared to pay a little extra if we also want the arm shorter.

[Nick]

Chuck (and Scud), I don't believe this community is going to stand for either of you eating the cost of anything. 

Agree. Why not use the total cost for the two runs to calculate the final "retail" for the spring? Hell, we are getting free labor anyway 

[Chuck]

Another old tool room saying.. "The guy that can smile when things are going wrong has found someone else to blame it on."

Just talked to Scud, and he is going to send me some springs to measure and see what we have.

Let's not get in too much of a hurry. Only one guy that I know of has his bike apart waiting for a new spring.

 

I should have just bit the bullet and made them.. sounded like work at the time, though.

[Lucky Phil]

Another old tool room saying.. "The guy that can smile when things are going wrong has found someone else to blame it on."

Just talked to Scud, and he is going to send me some springs to measure and see what we have.

Let's not get in too much of a hurry. Only one guy that I know of has his bike apart waiting for a new spring.

 

I should have just bit the bullet and made them.. sounded like work at the time, though.

While we're on old addages chuck, how about "nothing is impossible to the man that doesnt have to do it himself". I love a meandering thread. As long as it teaches you something:)

 

Ciao

[swooshdave]

Another old tool room saying.. "The guy that can smile when things are going wrong has found someone else to blame it on."

Just talked to Scud, and he is going to send me some springs to measure and see what we have.

Let's not get in too much of a hurry. Only one guy that I know of has his bike apart waiting for a new spring.

 

I should have just bit the bullet and made them.. sounded like work at the time, though.

 

 

We all work on our own bikes because we want to do it right, or at least as right as we know how to do. That way there's no one else to blame.

[swooshdave]

I think the manufacturer will work with us. The rep responded by e-mail that they have a 10 degree production tolerance. I measured that they were off by 15 degrees, so they are beyond their own stated tolerance.  He offered to rework the original material, but I don't think we should accept that - I think we need to prove this design with material that has been shaped only one time. 

 

I'll try to talk with him tomorrow and figure out the options.  Given the difficulty of replacing this spring, and the "chronic" nature of the problem, I think a re-run with new material is our best bet.

 

Perhaps we should be prepared to pay a little extra if we also want the arm shorter.

 

It may have helped to show them the part installed so they could understand which tolerances they could or could not play with. I assume you just provided them the drawing?

[Scud]

Swooshdave: "I assume you just provided them the drawing?"

 

 

 

No, I sent the drawing and one of the springs that Chuck made. The manufacturer messed up the angle, but we may have messed up the spec on the arm length - or the wrong angle had something to do with the way the length was measured. I'm sending Chuck a few of the new springs and the two parts that the spring fits into. Chuck will figure it out and we will persevere till the springs are right.

[Chuck]

[emry]

This is up in my office, but there is 3 more images and the titles are slightly different. Give me a day or two and I'll post it. It brings me back to the real world really quick when things go awol.  

 

 

[Chuck]

Ok, I see the problem. Scud sent me some springs to check. See the red line on the cad drawing and the box at the top left saying length .7?

2018-01-30_10-23-08 by Charles Stottlemyer, on Flickr

My bad. I intended to tag the end of the line when dimensioning it, not the center of the spring. That's why when I scaled the spring I'd made for the last time before sending the whole works back to Scud I marked out the .62 dimension and said .7    There is no excuse for that. Sorry.

Just the same, it would work ok. It just sits there and doesn't move through the full travel and more. Here is the assembly at coil bind.

2018-01-30_10-25-42 by Charles Stottlemyer, on Flickr

However, the angle is way out of spec. We asked for 15 degrees, and you can see it is 31. 

2018-01-30_10-24-55 by Charles Stottlemyer, on Flickr

That is unacceptable because it will drive the spring past it's "safe travel." My gut feeling is if the manufacturer could wind another 15 degrees on it, they would be ok.

Just the same, I'd like to make another run and make everything *right* including the ID of the spring. I asked for .660/.670" and it is .682. Again, that shouldn't hurt anything.. but it's out of the spec that was calculated. It will apply a (very) little less torque.

Maybe they will give us a break on another run because of one of the most important specs being out of tolerance?

There's a reason for that swing set cartoon..