Spring Twang

Hmm, sounds like you will have already thought of the obvious.

Is the spring under tension at all times? If not, it should be, this will help stop any rattle.

I'd maybe try a bit of plastic tube over the shaft so it sits between spring and shaft...of course, then you need to get the right plastic to suit the application ...but it is a quick tryout.

Try winding it tighter ...or loser, a tighter winding may add enough friction to stop the twang.

Is it a resonance problem? Try a longer softer spring or shorter stiffer one? (or vice versa!)

mmmm so many variables...so little time.

Sorry if this is just tooo obvious.

Good luck.

More info on the ecoat process please?

Max temp.

time?

Teflon sleeve may work.

Ecoat process, according to the supplier, should not reach temps above 400 degrees

throughout. With 1 hour and 10mins. in the oven.

Hi Lisa,

More info please.

Is the rattle due to resonance or does it occur when the sprung mass comes to a stop? Is there any damping at the stop point?

John

Lisa,

If the vibration is caused by resonance, you might consider an idea like the following. It's based on the dual springs used on intake and exhaust valves to prevent valve float.

If the problem occurrs when the sprung mass stops, there are, as I'm sure you know, many vibration isolator pad manufacturers around

John.

I have searched the web on end and have been unable to find supplier.

I have also tried: random split tubing (this looses it's shape once cut) radiator hoses, piping wrap to apply after coating. All have been rejected: due to walking off the spring or squeaks against the polyurethane foam bun. (application is for a head restraint mechanism)

The one supplier I received the "silicone" sample to try, I question. I think it should have withstood the ecoat process.

Thanks,

Lisa

The twang is exhibited at the stop point.

No dampening, other than an option to apply some kind of split tube to the spring

after coating.

I was hoping for some kind of design fix with the spring. If there is an industry standard or something.

I'm not getting much help from the supplier. I'm nowhere near an expert.

Thanks

I know zilch on this topic but was curious. I notice you're in Detroit so maybe know a lot about springs etc. Would a change of spring material allow an increase of coil separation and thus lead to noise reduction ? I came across this . I have no idea if it has relevance , but thought I'd offer up a starter since it's the weekend and you may not get any inspiration 'till folk are back up on Monday. This is way out of my field , so I won't follow how thing go (too many subscribed lines). In the remote possibility you need more info , you'll find me via the avatar. Best of luck , I'm sure somebody on CR4 has a good suggestion. Kris

Is the spring laterally retained to prevent coil-to-coil friction on torsion? How much rotation per cycle? How much endplay? If oiling eases the sound, you may be suffering from coil wind friction, and locking a lateral length with a thrust washer might help. I mention this because of the appearance of the freedom of the side arm.

RichH

Any oil/ wax is removed during the ecoat process.

I think due to the cleaning process or the high temps.

Could you elaborate on a thrust washer?

The center angle probably is places in a hole in the shaft. The external leg appears to be tensioned against another shaft, with no linear anchorage. The spring was wound tightly, with no space between coils. When the coils wrap, the side of each coil "rubs" against the next and previous coil. I believe your wire guage was 2.54 mm. 300 degrees of rotation means that every cycle causes an additional 5/6 of a turn, adding a mere 2.12 mm to the length of the spring. If the length of the spring were held at 3 mm or more greater than the spring length as placed, the coils would not "rub" against each other. An easy diagnostic to check if this is the problem would be to oil the coil to see if that silences the twang. If it does, then you are suffering coil to coil rub, and the spring then needs to be linearly anchored to include the added 5/6 of a coil without needing to move linearly nor rub.

Think of an overhead sectional garage door. The torsion spring needs to be A: Oiled frequently, or B:extended linearly to a length that will include the added 6 or 8 coils added on wind. Considering the minimal length of your added coil length, merely placing a stop clamp or grove on the restraining rod would give sufficient freedom to minimize the coil to coil pressure without adding excessive twist to the free end of the coil.

This would also have the benefit of keeping the internal shaft hook under pressure, another possible source of your twang.

RichH