I'm restoring an old tape recorder. The capstan flywheel is very lightly
pitted. I'd like to polish this out.
What would be a suitable polish? Or if it's likely to be too hard for a
polish, could it perhaps be sanded first?
It will need to be the very finest abrasive paper, because it needs to
have an extremely smooth surface.
It doesnt have to be THAT smooth.
However the trouble is, that anything you take off it will slow the tape
Th 'pro' approah wuld be to get the spindle off and make a new one, or
turn it down and fit a machined sleeve to it.
But for non critical applications, go to Halfords and get some wet and
dry of the finest grade - about 600 grit, cut strips and simply wind
round the capstan while running.
You can use jewellers rouge or valve grinding compound or even T-cut for
a final polish.
It would help if you properly described what bit you are actually talking
about. Do you mean the peripheral surface of the part the tape wraps round,
against which it is held by a pinch wheel and thus pulled past the recording
If so then I'd leave it alone unless the pits have sharp edges which might
damage the tape. The capstan surface should be almost mirror smooth. Some of
the advice you've been given such as 180 grit it bleedin' absurd. 180 grit
is rough as a dog's arse. 1000 grit is what you'd call a fine grit but even
that, or in fact any grade of abrasive paper will destroy the original
finish. You get surfaces that smooth by fine polishing with things like high
speed felt mops containing very mild abrasives in a slurry form.
If you remove material and decrease the capstan's diameter then the tape
speed will slow down NOT speed up. This is hardly rocket surgery. Smaller
diameter = lower peripheral speed for a given diameter not the reverse. It's
the capstan that drives the tape not vice versa!
If you remove the pits then the tape will no longer run at the right speed
which is fairly pointless. You'll also never remove them without machining
even if they're only a few thou deep. You can't polish off large amounts of
metal like that by hand and have any hope of keeping the capstan truly
circular. I've spent half a lifetime polishing crankshaft journals in race
engines so I know what it takes to remove a given amount of metal and what
surface finish you end up with. Half a thou is a shed load to remove by any
sort of polishing even when you're rotating the part on a lathe. You're
normally only talking about the odd tenth of a thou or even fractions of a
tenth for the final polishing operation.
The most I'd do just to make sure the pits didn't have sharp edges is go
over the surface very lightly with a fine metal polish, or even toothpaste,
and a cloth. Try on an old capstan first to make sure that even this doesn't
just lead to scratches.
He did. He said it's the flywheel. You then spend the rest of your post
ranting about the capstan. Perhaps you could spend slightly less time
being angry and slightly more time reading?
If he reduces the diameter of the flywheel and the flywheel is driven by
a belt then reducing the diameter of the flywheel will speed the tape
Piddling about with the flywheel and flatting it in an attempt to remove
pits (which is just about inevitable if one does it by hand) will
introduce "wow". It depends if the aim is to have a working tape
recorder or a pretty one that doesn't function properly.
If something is driven by a belt then it's a pulley not a flywheel! It might
well be a pulley that's attached to a flywheel but it clearly isn't the same
thing. So you clearly don't know for sure which bit he/she is talking about
either. Until he/she makes clear which bit is being discussed, what it's
made of, whether it's functional or decorative, whether it contacts the tape
or a belt or not we're all pissing in the wind here.
I think this is one of your saddest moments. In the past I've always
respected you posts but in this case you've hit rock bottom. I have no
intention to go into the semantics of flywheels, belts and pulley. You're
both grasping on so little information it's unbelievable. We still don't
have a clue whether it's significant the flywheel has pits or if it's made
smaller will alter the speed of the tape. You're both pissing in the wind
upstream. I prefer downstream myself, then it less likely to come back and
You are a rude and churlish person who I have no interest in squabbling with
A) because it's Xmas and B) because I gave up doing that many years ago on
Usenet after realising it was pointless and there's always someone new who
wants to troll or bicker. If you don't mind I'll just pop you in the
killfile instead and talk to the grownups, some of whom are no doubt
familiar with the extent of my engineering background.
You proved that you didn't know what you were rattling on about. Like
most LoudMouths, you assumed instead of thinking. And if your skills
with a kill-file match your other talents you'll be reading this.
Heck, you're too dumb to realise that Outhouse Excess doesn't have a
Perhaps you should check out Dave's site - his engineering expertise isn't
in question. And well engineered tape recorders don't use rubber band
drives anyway. That's reserved for the bottom of the market.
*Depression is merely anger without enthusiasm *
Dave Plowman firstname.lastname@example.org London SW
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