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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 25th Oct 2019, 8:24 pm   #1
Ted Kendall
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Default Fostex R8 pulleys

A hardy perennial, this, but I'm raising it because I have an R8 in front of me with pulley problems and want to see if there are any new ideas.

This machine drives each spool hub via a toothed belt and pulley from its own motor. The motor pulley is of softish plastic and is a push fit on the smooth motor shaft. Sooner or later, the pulley starts to slip, usually (but not in this case) because the boss cracks.

The various approaches seem to be :

Stick the pulley to the shaft with Superglue (too permanent?) or threadlock (doesn't work - I've tried it). What adhesive is likely to work?

Clamp the boss with a collar - I haven't yet found one small or shallow enough.

Burr the motor shaft and hope it grips.

Fit an aftermarket metal pulley - expensive, and maybe injurious to the belt.

Needless to say, actual Fostex replacement bits are made of the purest unobtainium. The pulleys on the present machine are undamaged but slip under heavy load.
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Old 26th Oct 2019, 1:43 am   #2
jamesperrett
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Default Re: Fostex R8 pulleys

Would 3D printing a new pulley be a possibility?
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Old 26th Oct 2019, 5:28 am   #3
TIMTAPE
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Default Re: Fostex R8 pulleys

It's been a while since I've had this issue, and on the Fostex I've not tried this, but if the boss is accessible I've sometimes wound multiple turns of bare wire around it, trying to tension the wire while winding it on. Then glue the ends of the wire to maintain the tension. I've used this on plastic parts which have a friction fit onto a steel shaft in VCR's but which have started to slip.

This has worked best when the boss has already cracked and the wire helps compress the boss back to original ID. Not sure if it would help if the plastic hasn't cracked.
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Old 27th Oct 2019, 11:50 am   #4
Michael Maurice
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Default Re: Fostex R8 pulleys

What I normally do is burr the boss and the shaft, then use a bit of araldite. I know its permanent but it works!
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Old 28th Oct 2019, 10:25 am   #5
Max Ripple
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Default Re: Fostex R8 pulleys

I found some metal collar's that were ideal,from a model shop I think.
I also had to drill through the plastic hub and use a longer grub screw though,to achieve "metal to metal" contact.
The problem seems to be due to the motor not being able to stop quick enough when the brakes are applied ?
The metal version replacement hubs do seem to be the best solution,but they are relatively expensive of course.
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Old 29th Oct 2019, 12:03 pm   #6
Max Ripple
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Default Re: Fostex R8 pulleys

I found the info on the collar's that I used!

They came from a company called Technobot's (very comprehensive website too) and their order ref is : 4609-050.

As mentioned earlier,I found that I needed to drill into the side of the plastic hub,then use a longer (3mm) allen screw to secure the hub to the shaft.

Nick
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Old Yesterday, 8:10 am   #7
Ted Kendall
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Default Re: Fostex R8 pulleys

Thanks all - in the end I went for old-fashioned Araldite and burring shaft and pulley - at touch inelegant, maybe, but effective.
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