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-   -   Using a grommet as a gear ! (https://www.vintage-radio.net/forum/showthread.php?t=141885)

Goldieoldie 3rd Dec 2017 9:01 pm

Using a grommet as a gear !
 
1 Attachment(s)
Hi
I thought u would share this with you
I was repairing a small transistor radio where one of the tuning gears had fallen apart
Not have a suitable gear ( it fitted on a 6mm splined shaft ) I cut a gromet in halve and positioned it so it engaged with the cog driving the cap
Although It was a tight fit on the shaft I added some evo stick to hold it in place
It works a treat ! It's even started to cut its own teeth into the gromet
Prob won't last for ever but has restored an old radio to working condition which I think is what our hobby is all about
Cheers Pete

Reelman 3rd Dec 2017 9:39 pm

Re: Using a gromet as a gear !
 
Nice!
Getting it working is what it is all about, sometimes a bodge is the only way to achieve it.
I wonder if I could do the same for the 70’s Grundig cassette mechanisms...
Peter

slidertogrid 4th Dec 2017 6:54 pm

Re: Using a gromet as a gear !
 
Ingenious ! I have a 1950's clockwork toy with a stripped gear. I will give this a try!
:thumbsup:
Rich.

G6Tanuki 4th Dec 2017 7:18 pm

Re: Using a gromet as a gear !
 
I like it! Very much in the "make do and mend" spirit.

In the past I did something similar to replace a gear by making up two SRBP 'cheeks' to fit on the spindle and packing the gap between them with Milliput, then coating the other gear with Vaseline and using slow rotation to cut teeth in the Milliput as it hardened.

Lloyd 1985 4th Dec 2017 9:16 pm

Re: Using a gromet as a gear !
 
Nice!

I used heat shrink in a Sony cassette deck on a gear that engages the heads during playback, the gear was made of a plastic that had the consistency of a lump of hard cheese! It stripped itself when I first tried it out, heat shrink gave it just enough grip to make it work.

Regards,
Lloyd

camtechman 5th Dec 2017 4:22 pm

Re: Using a gromet as a gear !
 
Reelman,

Quote:

I wonder if I could do the same for the 70’s Grundig cassette mechanisms...
I've got an odd sheet of firm rubber, about the thickness of the Grundig gear, can't remember where I got it from but now, encouraged by Goldieoldie's success, I'm going to experiment with making "That Gear".

Will report later, I'm even going to order some more No11 blades for my Swann Morton scalpel (and some Band-Aids for my fingers !)

dseymo1 5th Dec 2017 9:39 pm

Re: Using a gromet as a gear !
 
Perhaps traditional rubber tap washers could be pressed into similar service.

Karen O 5th Dec 2017 9:43 pm

Re: Using a gromet as a gear !
 
I once made a makeshift slow motion control that used a grommet pressing against a metal tuning dial.

deliverance 6th Dec 2017 2:33 pm

Re: Using a gromet as a gear !
 
Simple but effective nice one

Nymrod121 7th Dec 2017 4:20 pm

Re: Using a gromet as a gear !
 
Brilliant! :thumbsup:

The BBC Audio Test Set EP14/1 in all variants has a similar arrangement for the frequency set control. A (flywheel-equipped) spindle has a rubber grommet that presses against the surface of an aluminium disc connected to the Wien Bridge oscillator's air-spaced capacitor. It serves as a 'mitre box' * and reduction gear combined.

Guy




* (any bus enthusiasts out there will know this is a 'Bristol VRT transmission' term ;) )

Argus25 8th Dec 2017 12:10 am

Re: Using a grommet as a gear !
 
Good repair if you are stuck on a space ship or on moon base alpha with no spares and very few tools, the ingenuity might save the day.

Many tuning mechanisms that have gears rather than some sort of friction drive did it because the vanes of the variable capacitor required to have some fixed registration with the tuning dial-knob or tuning pointer (I'm not sure if this is so in your radio). In these cases it is necessary to replace or re-manufacture the missing gear if the dial-station pointer system is to work properly.

Old clocks, electric or mechanical, can be a good source of small gear wheels to jimmy up a repair, if a gear set is required. In the days of watch & clock making the local repairer would machine one up for a good price, but those days appear long gone.

Lloyd 1985 8th Dec 2017 3:41 pm

Re: Using a grommet as a gear !
 
I'm hoping that decent quality 3D printing will eventually become as affordable as photo printing is now, I've measured up the gear that I need for the Sony cassette deck, just need to be able to manufacture a good replacement! Strangely, on a slightly later Mk2 version of the deck that particular gear had been done away with and replaced by 2 wheels with belts instead. I guess it was probably a problematic part for Sony, so they redesigned it.

Regards,
Lloyd

FrankB 10th Dec 2017 8:15 am

Re: Using a grommet as a gear !
 
I have used neoprene fuel line to replace the rubber friction drive on the tuning shaft of an Atwater Kent model 55. Last I heard, it was still working , and that was 15 years back.
Using rubber as a "friction slip drive" was common in a few U.S. made radios.

Some were odd cast parts, and a real pain to replace or repair so they worked reliably.
I honestly had forgotten about using a grommet. Thanks for the reminder!


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