cracked nylon gear repair

[maxhifi]

Have a gear with a crack in it. I've read here that nothing works, but then I started watching Youtube videos about people using superglue with baking soda as filler. Is this more too good to be true nonsense, or is it a real fix? Anyone have any anecdotal experience to share?

 

[dondoucette]

Sorry no experience there but I have been using my 3D printer to make parts for a while now.

 

[maxhifi]

Sorry no experience there but I have been using my 3D printer to make parts for a while now.

Is there a lot of effort involved in building a model?

 

[northpaw]

Not much sticks to nylon. You don't say what the gear is from, but sometimes, you can get lucky if the same kind of gear is used in other applications (see posts by dgwojo):

http://audiokarma.org/forums/index....00-dvd-cd-player-repair-advice-needed.107687/

 

[maxhifi]

Not much sticks to nylon. You don't say what the gear is from, but sometimes, you can get lucky if the same kind of gear is used in other applications (see posts by dgwojo):

http://audiokarma.org/forums/index....00-dvd-cd-player-repair-advice-needed.107687/

It's a cassette deck, the gear is the one which flips the head around when it changes sides. Unfortunately not a common spur gear, and it's a fairly obscure sankyo mechanism used apparently only in a couple sansui decks. I contacted an eBay seller who reproduces gears, by some proprietary process, not 3d printing. I'm going to send it to him and see what comes back. I suspect he's making a mold and casting a new one out of epoxy resin, but that's just a theory. This deck is one of those "tough dog" repairs which would be a write off if I was doing it for anyone except myself.

 

[fernarias]

I repaired a nylon gear on my printer that had a crack by melting the plastic into a v grove on both sides and then filling the v grove with additional melted nylon. I did that in 2016 and the printer still prints (at least until another gear goes). I've also seen youtubers make new hears with a 3d printer.

 

[ghazzer]

Don't lose the pieces of the original gear. That may be you only hope for constructing a model, which will be needed before a new gear can be made.

 

[ETLS]

Nylon is pretty tough. If it is thick enough you could drill, tap and set screw it.

 

[Binkman]

this may work though is it worth the price?
https://tbbonding.com/product/basic-poly-plastic-kits/

no affiliation but I like looking up stuff.

a pic would help.. I've used fine copper wire and my solder iron to melt-stitch a nylon seam-crack but the gear wasn't tiny.

 

[maxhifi]

 

[maxhifi]

There you go. What happens is when it hits the crack, it jumps a couple teeth, and eventually gets all out of position after a few cycles. It's the gear which flips the head around, in an auto-reverse tape deck. Outer diameter is 9mm.

I'm going to get that eBay guy to make a copy of it, and see how it works out. I think he's got a good system, he's selling replacement gears for all sorts of old tape decks, and the price is 20 Euros for him to do all the work. I know for sure that I'd be paying myself pennies an hour to beat that price.

 

[ghazzer]

That gear looks like it has been through the wringer. Several times!

 

[cpt_paranoia]

I'd start by cleaning it so you can actually see what's what... That's got to be the filthiest nylon gear I've seen...

 

[pishta]

I'm going to try and cast one from lead with a Gelatin/glycerin mold and a lost wax casting in plaster. Well see if it is fine enough in detail to work. Its a 16 tooth .248 inch Sony Auto-reverse head spur gear. Lead is hard enough and has a low melting point. If it doesnt come out , just remelt it, same with the mold material.

 

[Pio1980]

Nylon may be rebonded with the right agent, but the acetal plastics used in most applications like this aren't bondable afaik.

 

[sKiZo]

Betcha someone here could make some bucks 3D printing this sort of thing. Send in what's left of the original, and get a shiny new one in the mail ... kewl beans! ;-}

 

[ghazzer]

I made detailed measurements of my PL-570 gear, then spent a lot of trial and error to construct solid models using TurboCad Pro and SolidWorks. But my cracked gear was in much better condition than yours. I had some excellent help from other AKers an was able to et a 3D printed gear that meshes with the other gears.

Some people can do a 3D laser measurement of an object and create an .STL file that could be 3D printed. However, that would be an (almost) exact copy of your gear in post #10. The .STL file can be imported into a solid modeling program, and significant work on your part could create a symmetrical model that is mathematically correct. Some of the dimensions may have to be tweaked to make the new gear mesh.

This may be a little much for a one off - - -

 

[maxhifi]

I ended up putting this thing on a shelf and forgetting about it... I kind of lost interest after not figuring out a decent way to repair it

 

[parman]

I ended up putting this thing on a shelf and forgetting about it... I kind of lost interest after not figuring out a decent way to repair it

I had a Yamaha deck with a Sankyo transport, once it started acting up there was no saving it. I did get it going a few times but it was never right

 

[maxhifi]

I had a Yamaha deck with a Sankyo transport, once it started acting up there was no saving it. I did get it going a few times but it was never right

On this one the capstan motors are both bad, because it was left ON for probably years on end. Because of the way these transports are made, the motors are a different speed than the common replacements. I finally found some new motors, but then the cracked gear happened and I decided this thing is not worth all the effort.