Suspension tapes

[Clive HartlandParticipant @clivehartland94829]

[Clive HartlandParticipant @clivehartland94829]

I have aquired a quantity of suspension tapes which measure 0.07mm thick by 1mm wide and are 35mm long.

Having no use for them I ask if there is anyone else interested as I am loathe to throw away.

Clive

[Michael GilliganParticipant @michaelgilligan61133]

I would certainly be interested in a few of those, Clive

Thanks for the thought

MichaelG.

[Clive HartlandParticipant @clivehartland94829]

OK Michael, just PM your address and I will shift a few to you. 10, 20, 30 or more- please indicate.

Clive

[wheeltapperParticipant @wheeltapper]

I might be interested if I knew what the darn things were.

how about a clue Clive.

Roy.

[Clive HartlandParticipant @clivehartland94829]

Roy, suspension tapes are used to support pendulums and compensator bodies. The physical appearance is a polished strand of uniform shape and size. They have low stretch and will return to the original setting position after movement. You may have seen them in those clocks that have a rotating pendulum, a novelty clock. They are also used in Gyros to transmit power to the gyro as they have very little torsional effect. I hope this answers your question or someone else can elaborate on them.

Clive

[Michael GilliganParticipant @michaelgilligan61133]

Good summary, Clive

'though it's worth mentioning that the suspension springs for "400 Day" clocks [a.k.a. Anniversary clocks] are much longer, and a little wider, than the ones you have.

MichaelG.

.

Edit: here is the horolovar web-page

Edited By Michael Gilligan on 21/02/2014 10:03:13

[wheeltapperParticipant @wheeltapper]

Thanks Clive, something else I've learnt.

I can't think of a use for any tho, so I'll pass .

cheers

Roy.

[Ian PParticipant @ianp]

Clive, I am a bit intrigued now. I dont have any use for the tapes you are kindly giving away but it started me thinking if this the sort of material that would have been used to suspend 'taut band' moving coil meters?

Then I wondered why plain round wire would not have worked just as well, as its just a torsion spring really.

What material are the ones you have made from?

Lastly, how does a short flat strip of metal cope with the rotation of the gyro (gimbal)

Ian P

[Neil WyattModerator @neilwyatt]

> Then I wondered why plain round wire would not have worked just as well, as its just a torsion spring really.

At a guess if you clamp both ends of a flat tape in two parallel clamps, you know there is no torsion in the undistorted tape. You have no way of knowing if a round wire has a twist in it.

Neil

[Ian PParticipant @ianp]

Neil

I suppose it all depends on what is being suspended. If its is for a moving coil meter then the torsional resistance to twist is the whole idea.

There will be no twist in round wire once its allowed to rotate and settle in its natural position (assuming its just a single wire, clamped at the top and tensioned with a weight attached at the bottom end.

Ian P

[MICHAEL WILLIAMSParticipant @michaelwilliams41215]

I don’t specifically know about suspension tapes but in general :

A flat torsion spring has a ‘home’ position – if clamped on a flat at the top and rotator is clamped on a flat at the bottom then you know where the equilibrium position is .

For the same amount of metal :

A flat torsion spring is much more flexible than a round one but can still carry the same axial load .

A flat torsion spring has slightly more intrinsic damping than a round one .

MikeW

[Clive HartlandParticipant @clivehartland94829]

When I worked on suspended Gyros the suspension tape was at least 100mm long. In the non running position a spring loaded base was lifted up and supported the gyro body to save the tape from damage. ie. gravity.

Once started the gyro motor was slowly released and it would start to precession and then the motor was switched off and allowed to run down and the gyro would end up in a stasis position and this was the point where you adjusted the tape mount to turn whichever way to bring the optical viewing scale to zero, this could take a few hours of starting and stopping and resting.

By this method the swing either side of zero was equal and this was timed over a certain period and the swings got less and using a calculation Magnetic North was established at the position of the gyro. This magnetic North varied all over the place as it was affected by mettalic ore deposits or nearby railways etc.There is a natural undulation of the magnetic lines across the globe.

Uses were underground for mapping tunnels and for aligning aircraft navigation instrument and the weapon systems. Used on submarines to align the nav. system accurately. Also in times past to accurately locate the position of Artillery Batteries for accurate shooting.

All this is now pretty well overridden by Sat. Nav. systems.

The type of gyro was called the Rellensman system, there are other types out there.

Things that I found that affected the tapes are, oil on them, a kinked tape and a badly clamped tape end where it was not square to the mount. This was quite common and enough for me to check before any test on gyros coming in for test or repair.

Clive

[Michael GilliganParticipant @michaelgilligan61133]

Posted by MICHAEL WILLIAMS on 21/02/2014 20:24:45:

… For the same amount of metal :
A flat torsion spring is much more flexible than a round one but can still carry the same axial load .

.

… and that's why the ribbon shape is used in the clocks, etc.

It may not be intuitively obvious, but a circular cross-section is much stiffer in torsion than a thin ribbon of the same cross-sectional area. [Ref: Polar Moment of Inertia] … It also suffers a large change of stiffness for small change in diameter; making it difficult to produce to a particular spring-rate: The ribbon, by comparison can be "tuned" more easily; either by thinning it, or narrowing it.

MichaelG.

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