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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 20th Apr 2017, 11:00 am   #1
G8BBZ
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Default Slow Motion Drive Problem

I have a receiver (Redifon R408) with a problem slow motion drive. The drive operates by means of a friction contact between a smooth rubber coated drive wheel and a smooth plain steel idler. At some stage in its life, the drive mechanism has been lubricated rather generously, resulting in the drive wheel and idler both being liberally coated in oil. As a result, the friction between the two is not enough to transmit the drive - hence no slow motion.
I obviously need to get rid of the oil and this is simple enough for the plain steel idler but I am wary of using any solvent on the rubber coated wheel in case it affects the rubber - I am calling it rubber but don't actually know what the material is, other than it must have rubber like properties.
Any thoughts on a safe way to get rid of the oil and restore the friction surface?
cheers
Peter G8BBZ
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Old 20th Apr 2017, 11:10 am   #2
Boater Sam
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Default Re: Slow Motion Drive Problem

Isopropanol alcohol should not harm the rubber if used with caution. I would clean it well and then apply talcum powder over a few days to soak up any oil that seeps out of the rubber . When no more is seen to be darkening the talc, wash it again in isopropanol.
A slight softening of the surface may be advantageous.
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Old 20th Apr 2017, 11:13 am   #3
carnivalpete
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Default Re: Slow Motion Drive Problem

With knowing what the ''rubber'' material is, soap and water would obviously be the safest. I assume you don't want to consider dismantling. Can you reach the wheel with a cotton bud stick and soapy water? pete
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Old 20th Apr 2017, 11:57 am   #4
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Default Re: Slow Motion Drive Problem

I'd try a few drops of fairy-liquid or similar dishwashing detergent massaged directly into the rubber wheel, then left for a while to do its thing, then wash off. Without knowing the precise version of 'rubber' used I wouldn't start using any more-aggressive organic solvents (I had bad experiences of using Acetone on parts of an ancient VCR: some drive-pulleys were almost instantly reduced to blobs of black-stuff with a consistency like chewing gum).

You may need to repeat several times as more of the absorbed oily contaminant diffuses up out of the surface of the rubber.
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Old 20th Apr 2017, 12:55 pm   #5
merlinmaxwell
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Default Re: Slow Motion Drive Problem

If the 'rubber' doesn't melt with a touch of a soldering iron, boil it for a while in clothes detergent.
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Old 20th Apr 2017, 11:04 pm   #6
emeritus
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Default Re: Slow Motion Drive Problem

I used to have a Eumig 8mm cine projector that had what sounds like a similar arrangement of steel wheel and rubber-coated disc to provide variable speed control by adjusting the radial position of contact. It used to slip in the position of normal speed as the rubber had lost its grip. Following a hint on this forum I applied some household Glycerine to the rubber, and it did indeed restore the grip. If you find it still slips after cleaning, this might help. I just smeared Glycerine over the surface of the rubber, left it for about 10 mins, and then cleaned it off.
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Old 21st Apr 2017, 9:59 am   #7
G8BBZ
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Default Re: Slow Motion Drive Problem

Hi All,
Many thanks for the insights and tips. Hope to get to it this weekend.
cheers
Peter G8BBZ
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