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Vintage Tape (Audio), Cassette, Wire and Magnetic Disc Recorders and Players Open-reel tape recorders, cassette recorders, 8-track players etc.

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Old 5th Oct 2019, 1:12 pm   #1
Dorian27
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Default Measuring tape recorder belts

Can any one please tell me how do I measure a tape belt if it hasn't broken please do I. Bend it in half and then double it etc mm doubled or something else
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Old 5th Oct 2019, 4:22 pm   #2
paulsherwin
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Default Re: Measuring tape recorder belts

Lay it flat and measure the length. Double the measured length to get the circumference. A bit of algebra gets you the radius, which doubled gives you the diameter. Belts are normally sold by circumference or diameter.

https://en.wikipedia.org/wiki/Circumference
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Old 5th Oct 2019, 10:55 pm   #3
joebog1
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Default Re: Measuring tape recorder belts

Its exactly as Paul has explained. Here is an Australian catalogue page showing exactly that in pictures. I have not cropped the scan to show some of the belts available. There are three such pages in the catalogue, so many belts are still available.

Joe
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File Type: pdf Belts.pdf (392.8 KB, 96 views)
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Old 6th Oct 2019, 12:30 am   #4
Trigon.
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Default Re: Measuring tape recorder belts

With thicker belts or o-rings the doubling up method can be difficult to do accurately.

An alternative method is to place two coins inside the belt on a flat surface, pull the coins apart to tighten the belt to the required tension, and measure the distance between the coins.

If the diameter of the coins is 'D' and the clear distance between coins is 'H', then the inside circumference of the belt is made up of two straight sections, each (D/2 + H + D/2) = (H+D) long, plus two half circle sections of diameter 'D', each (pi*D/2).

So the circumference = 2*(D+H) + pi*D

The inside diameter of the belt is then (circumference/pi)

Cheers
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Old 6th Oct 2019, 4:22 pm   #5
Dorian27
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Default Re: Measuring tape recorder belts

Thank you everyone most grateful
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Old 6th Oct 2019, 5:35 pm   #6
McMurdo
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Default Re: Measuring tape recorder belts

make sure you dont order a belt that has the same circumference as the old stretched one, or you'll just end up with two the same!
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Old 10th Oct 2019, 5:06 pm   #7
radiotechnician
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Default Re: Measuring tape recorder belts

Back in the days of VCR repair, I purchased a device made of
cardboard which measured belts. It is like a slide rule, with two
posts, which held the belt under slight tension. There were other
measuring means for thickness as well. It came from the parts
house I was using in the 90s.

It was fine for most belts, but useless for the long belt
in the Philips vacuum tube recorders.
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Old 10th Oct 2019, 5:34 pm   #8
Radio_Dave
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Default Re: Measuring tape recorder belts

Quote:
Originally Posted by McMurdo View Post
make sure you dont order a belt that has the same circumference as the old stretched one, or you'll just end up with two the same!
Good point! I tie thin cord around the pulleys, cut it off, measure it and then deduct 10% to get the belt size

David
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Old 10th Oct 2019, 5:56 pm   #9
electrogram
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Default Re: Measuring tape recorder belts

I was going to say the same as above, but 10% seems too much, I do about 3%
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Old 1st Dec 2019, 12:51 pm   #10
BrianAllen
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Default Re: Measuring tape recorder belts

I agree with last post, I calculated about 5%.

Anyway, I had no success supergluing the belt/cord material that I purchased, so ended up buying new belts for my Philips N4308, which incidentally were so much more expensive than listed by our Australian friend, joebog1 in the attached pdf.
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