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Restoring decayed gears


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#1 caution

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Posted 14 September 2019 - 06:04 PM

I was asked to see if I could reproduce a couple of deck gears that decayed. You know the ones, they're kinda rubbery to reduce vibrations, but the chemicals doing the softening escape over the years, reducing its strength to that of an almond - scrapes away and cracks apart very easily.

One broke during shipment despite excellent packing, but I got all measurements after reassembling it. A lot of time spent with a jewelers loupe and caliper, re-re-checking and adjusting until I zeroed in on something nice and close. I wasn't able to get their exact shape from any gear design tools, so I drew them manually, doing a 50/50 overlay with images to confirm. My camera aim isn't 100% straight so there's some perspective misalignment and sides of teeth visible, but still good enough to confirm.  Based on how they're meshing in the first pic, it will be a close fit and may need adjustment if it ends up on the high side.

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#2 Reli

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Posted 14 September 2019 - 06:13 PM

Nice, was this for a Philips or Grundig?



#3 caution

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Posted 14 September 2019 - 08:17 PM

Hey thanks. It's from one of Grundig's Party Centers.



#4 ralrein1

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Posted 16 September 2019 - 12:09 AM

Very cool. Can't wait to see it when its fixed.

#5 Fatdog

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Posted 16 September 2019 - 11:45 AM

Wow!  Your abilities never cease to amaze me, Eric.  :bow:



#6 Rimmer36

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Posted 18 September 2019 - 08:31 AM

Wow!  Your abilities never cease to amaze me, Eric.  :bow:

this, superb as usual



#7 BoomboxLover48

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Posted 20 September 2019 - 10:51 AM

Eric the Magician is always at work!  :-D  :yes:



#8 caution

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Posted 20 September 2019 - 12:18 PM

Thanks guys! Crossing my fingers, they're printing now.



#9 MesaAZGuy

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Posted 20 September 2019 - 10:33 PM

I admire the talent you guys have.



#10 caution

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Posted 04 October 2019 - 02:20 AM

I attached a few to save costs, so when they arrived I had to sand off the sprues. I bored out the holes a bit since they were intentionally undersized to let me create a smoother surface inside. Winner! The teeth mesh as expected.

 

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#11 Superduper

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Posted 04 October 2019 - 02:24 AM

Fantastic work! Eric is 3D magician.

#12 docs

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Posted 04 October 2019 - 04:52 AM

Bloody legend.



#13 BoomboxLover48

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Posted 04 October 2019 - 06:28 AM

That is AMAZING! :jawdrop:  :bow:



#14 trippy1313

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Posted 05 October 2019 - 09:32 AM

Dude. Wow.

#15 baddboybill

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Posted 05 October 2019 - 01:18 PM

That is very cool Eric!!!

#16 geoffhartwell

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Posted 06 October 2019 - 02:51 AM

wow, great work



#17 caution

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Posted 16 October 2019 - 01:54 AM

Thanks guys. Despite being tedious at times, measuring over and over to be absolutely certain, there's a lot of satisfaction bringing these parts back from the dead.

 

Bill was nice enough to send me the notorioius Magnavox gear, it's printing now, fingers crossed!! The overlay image shows the outer teeth off by about a degree, but it doesn't matter. The gears that mesh with it turn independently.

 

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#18 Superduper

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Posted 16 October 2019 - 02:11 AM

Hmm, interesting. Just curious, if the number of teeth is the same, how can they be off by a degree? Each circle has exactly 360* right so as long as the # of teeth is the same, I’m thinking the rotational spacing should be the same too?

#19 docs

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Posted 16 October 2019 - 02:27 AM

Thinking with there being an angle too, that would affect the spacing accuracy too. Not sure but very nice work.



#20 caution

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Posted 16 October 2019 - 02:43 AM

Yeah, the angle makes it a little tougher because the shape you see at the surface is a 30-degree cross section of what you need to sketch out for the tooth. Spacing them apart evenly is easy, but the shape of the tooth takes more time to get right. I had to use a jeweler's loupe to get close enough. You can see in the green pic how the gaps between the teeth aren't quite enough, so I had to adjust the shape a bit to make a bigger gap. I would imagine their shape needs to be nearly perfect to avoid vibrations and noise, like if the gap is too much the gears may chatter a bit, but if it's too little, it might jam up or break.

 

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#21 docs

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Posted 16 October 2019 - 02:51 AM

Eric, does it remain that angle all the way round or do the teeth straighten off? It's hard to tell.



#22 caution

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Posted 16 October 2019 - 09:05 AM

Hmm, interesting. Just curious, if the number of teeth is the same, how can they be off by a degree? Each circle has exactly 360* right so as long as the # of teeth is the same, I’m thinking the rotational spacing should be the same too?

 

Exactly. The inner and outer teeth are independently drawn, they just didn't end up at the same rotation as the original gear. Actually the outers are off more than that, I turned it for the pic but didn't get it exact



Eric, does it remain that angle all the way round or do the teeth straighten off? It's hard to tell.

 

Yeah. Each tooth is the same rotation of 30 degrees



Angled views can be deceiving because of the way the program adjusts for perspective. Here's a shot of the blue gear above, from straight above, compared to the original. The gap actually looks a little smaller

 

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#23 docs

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Posted 16 October 2019 - 09:48 AM

Got ya, painstaking and difficult, makes your effort even more stunning.

#24 caution

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Posted 05 November 2019 - 01:19 PM

I've sent out three of these to members, but haven't received any feedback yet.

If you're interested in trying one, I have two left. First come first serve.

 

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#25 Superduper

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Posted 05 November 2019 - 06:03 PM

I don’t have that Boombox to try. All that talk years ago about Humpty Dumpty gears discouraged me from considering that model(s).