Spray on rubber coating

[Ian PParticipant @ianp]

Posted by Robert Dodds on 20/11/2012 18:15:48:

Les,

Could I have ever imagined when I penned my original enquiry for a rubbery coating that it would bring forth such a range of alternative solutions?.

I did say that the wire was pulled through and the capstan provides the pull.

The whole thing is part of a wire winding device and the capstan drive pulls wire of a bulk reel, 100mm dia x125 wide 2kg in weight but varying through the draw off of wire and equally varying inertia characteristics.

From the capstan the wire is taken through a series of pulleys that create a buffer length of wire that copes with the cyclic demands of the winder (Av draw off rate 0.3m /sec but instantaneous wire velocity is varying from 0 to 0.6m/sec at a rate of approx 3 cycles/sec in a pseudo sinusoidal way.

The buffer mechanism is linked by sensors to the capstan drive motor and regulates the capstan speed to match demand. (As long as the wire doesn't slip)

The original configuration did rely on a nipping drive with a Hellerman shrink sleeve on the driven wheel but the wire cut through the sleeve very quickly so I had to move on from that.

I'm not looking for a total redesign of the system, rather a simple, reliable increase in friction characteristic over the wire on tufnol combo.

I'm hoping the improved design using a rubber band, as mentioned earlier will prove sufficient, but if you can identify a easily applied tough rubber coating I would still consider it as an option.

Bob D

Bob D

I am not trying to be pedantic but your original post did not say the capstan was doing the pulling. What you actually said was,

'Posted on 16/11/2012 14:14:27:'

I need a coating to go on a capstan wheel to increase the friction drive on a 0.004" steel wire being pulled through it.

<snipped>

Heres hoping

Bob D'

I read that as meaning the wire was being pulled through it ( the capstan?)

I have not looked up the true definition of capstan but on a complex bit of machinery with rollers. idlers, jockeys and assorted other wheels guiding the raw material, the name that designers and instruction manual writers use seem to vary like the weather.

Anyway, your rubber band method will most probably solve the problem and that is the main thing. Actually Tufnol seems an odd choice to get the best grip, I think plain steel would work better, its fine for locomotives after all.

Ian P

[Les Jones 1Participant @lesjones1]

Hi Bob,
The fact that the wire has knots in it make the problem more difficult. I was thinking of suggesting that the capstan had a "V" groove for the wire to run in of such a depth that the depth that the wire was just above the surface of the capstan. One or more ball bearings could press the wire into the groove which would increase the friction. This would not work with the knots in the wire. One suggestion that might work would be to have two or more capstans with the wire passing round 300 degrees on each one. Each capstan would need to be driven by belt or gear coupling.

Les.

[Robert DoddsParticipant @robertdodds43397]

Ian,

Tufnol is quite a versatile material and I'd got some at the right size so it got used! I don't think it had been invented when locomotives first came on line so it wasn't really given a chance but when it comes to grip your man on the loco up Snowdon doesn't rely on his steel wheels for grip!!

You questioned the exact meaning of "capstan" I must admit to have grown up with the word and done the usual experiment with a capstan drum and rope at college to prove friction theory but never questioned it's appropriateness in this instance.

Looking up capstan in Wiki made me realise that the Navies of the world speak yet more languages than mere designers and manual writers.

My capstan should be termed a windlass as it runs on a horizontal axis but looking at Anchor Windlass I see that it tells me more about reaching "the bitter end" and slipping anchor and I also know now that a Hawsepipe is not something used by a Yorkshireman to clean his car and as far as I can tell I don't have a spurling pipe although I have got a couple of previously unmentioned close wound spring tubes down which the wire passes and these prevent the wire getting into a robble as it unreels because the original reeling of the wire set a curl into the wire. This needs containing or else the wire will run up into a freely made kink, and as it draws tighter, form into one of the annoying knots that snag round the "windlass"

Bob D

[Ian PParticipant @ianp]

Bob

I feel very mildly admonished, but cleverer all the same! (since I have looked it up, after I had posted)

Ian P

[SteveWParticipant @stevew54046]

Normal way might be to wrap wire round more than once. Sorry if someone else has suggested that.

SteveW

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