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My Menacing Molly from Spirit Halloween needs a new 'neck' gear that swings her head forwards and back (before she leans backwards). I've tried to contact Spirit Halloween several times over the last few months but I never received a reply from their support. I don't want to replace the whole prop just for a plastic gear.. I looked on amazon at multipacks of plastic replacement gears but none of them look to accommodate a square shaft like this one has. Does anyone know where I might be able to find a replacement?

~16 mm diameter
~2.5 mm square shaft hole
I think there is 18 teeth, it's hard to tell being some are chewed up

Molly120190420_103729.jpg
Molly220190420_103708.jpg
 

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I hate plastic parts for gears. Hope you can find a replacement gear for her. I'm not familar with Menancing Molly (love the name though). Might be helpful for people to see what she looks like.
 

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Yeah, you're not gonna get any help from Spirit on parts, they don't sell them and don't know where to get them. Those props all come from China so when they break, you're on your own. Don't mean to be a buzz kill but that's how it is. Anyway, good luck!
 

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Thinking that posting this thread on the Props forum might garner a few more responses.

Do you know anyone with a 3-D printer and some programing skills? It looks like you could scan and then replicate the good half and flip with a simple CAD program.
 

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Ah a crown gear. Name seems appropriate. But what kind of shaft shape is that it sits on? Don't think it's a cylinder. Not even sure it's square. Likely some specialty part the manufacturer chose to make it difficult to repair or prevent other manufacturers from copying without putting some money into it.
 

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If you can't find the kind that has a hole with the flat spot on it, you can drill a small hole in that collar of plastic on top of the gear and put a small screw there on the flat of the shaft to affix it and let it work with it.
 

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Discussion Starter #10
Ah a crown gear. Name seems appropriate. But what kind of shaft shape is that it sits on? Don't think it's a cylinder. Not even sure it's square. Likely some specialty part the manufacturer chose to make it difficult to repair or prevent other manufacturers from copying without putting some money into it.
It's hard to see in the picture, but the shaft is perfectly square.
 

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Thinking that posting this thread on the Props forum might garner a few more responses.

Do you know anyone with a 3-D printer and some programing skills? It looks like you could scan and then replicate the good half and flip with a simple CAD program.
I don't know anyone that has a 3D printer. I had thought of getting one but I never had a solid reason to get one other than it will be cool to play around with. Now I wish I had one!
 

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It's hard to see in the picture, but the shaft is perfectly square.
...and you put that in the original post... I am blind... lol

The round holed gears would still work. I'd suggest drilling that hole and affixing it with two screws. Four for the best security.
 

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Discussion Starter #13
Crown gear.. good to know! I'l poke around on amazon and see if I can find something. I was thinking a hobby shop might have something too. Thank you!
 

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Crown gear.. good to know! I'l poke around on amazon and see if I can find something. I was thinking a hobby shop might have something too. Thank you!
I work at a hobby shop. You may have a chance at a hobby shop but it would be pretty spotty at best.

I am pretty sure I have some of these in stock at my shop, but I am not there at the moment...
There is a company we order from and they have bags of gears like these. I'll throw a link here for you to check out. If your local shop can get these for you, they'd work pretty well. These are DEFINITELY for round shafts and you'll have to come up with a way to secure them to the shaft you're using.

http://www.hobbylinc.com/htm/svm/svm101.htm

These definitely won't work, I wanted you to see the companies packaging.

Those are also for a smaller shaft (By a teensy bit, but still smaller) and I've sold these for projects like this before. If your local shop has this companies stuff, you've a chance to order the other bags of gears from them.

-Mike
 

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It's hard to see in the picture, but the shaft is perfectly square.
I see two kind of blue lines on the side of the shaft to the left of the full gear teeth in the second photo and couldn't tell if they indicated angled or curved metal and a reflection off of it. The top photo however does looks like a flat side (broken teeth side of the gear).

A "D" shaft makes sense to prevent slipping and I've seen that especially when used with a knob (such as a volume knob) attached to the top of the shaft.
 

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I did a quick sketch in Fusion 360 of the main parts to show how it can be done for 3d printing....Here's a quick 20 second youtube video to show the main components....
https://www.youtube.com/watch?v=JqR8AF0aqyo
You can make the hole any shape you want...The dimensions aren't right and I only made 1 tooth but I just wanted to show how it is possible....If 3d printing I would separate the disk with teeth and the spacer below it so you wouldn't have to use any support when printing and just glue the 2 together...The square hole is where the torque is going to be applied so simply gluing the 2 together would be fine....I would print in ABS since it's fairly strong.....ZR
 

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I agree about the 3D printer.. My son has one and was able to make me many things that I needed and could not find.. I just checked and there are many online stores that do 3D printing for a fee.. Might be worth checking out..
 

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I have a coffee cup insert for my car that is a 3D printed item and I know there are different plastics that can be used to create products with the printers based on things like temperature during use, etc. Wonder however if for something like a gear that would get a lot of pressure or use (and the original already had the teeth broken off) that this option would be a good one as opposed to something that was produced in another manner. I can see making prop parts like eyeballs, hands, but question something like a gear. Just really not familiar with 3D printing but hate to see him spend money getting one made (assume setup and materials costs would be the bulk of the cost) and still have basically the same issue afterwards.
 

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I have a coffee cup insert for my car that is a 3D printed item and I know there are different plastics that can be used to create products with the printers based on things like temperature during use, etc. Wonder however if for something like a gear that would get a lot of pressure or use (and the original already had the teeth broken off) that this option would be a good one as opposed to something that was produced in another manner. I can see making prop parts like eyeballs, hands, but question something like a gear. Just really not familiar with 3D printing but hate to see him spend money getting one made (assume setup and materials costs would be the bulk of the cost) and still have basically the same issue afterwards.
To be clear, I wasn't suggesting 3d printing as the solution in this case....If someone doesn't already have a 3d printer to begin with, it's not practical at all but since someone suggested maybe it's possible with 3d printing, I just wanted to affirm it could be done and also why I said "I just wanted to show how it is possible"....As for strength, people are making working gears all the time....The problem with using a harder substance like nylon to make a new gear is the rest of the working gears are plastic and the nylon would chew away at the remaining gears it touches....I'm not sure how long a newly printed plastic gear would last but we're talking about cheap Spirit mechanics that aren't going to last long anyway....If a person already had the printer and basic knowledge of the software (like the free autodesk Fusion 360 I used), it would be a natural progression to try to use it to make a gear....Another nice thing about having the setup is having the ability to easily print a second, third, etc... After you've made the file, it's a button push away to make another....If the prop has a certain gear as a weak point that keeps breaking, you could get more seasons out of it by replacing that one gear....One thing's for sure though, your not going to call up Spirit and get a replacement part!....But yeah, I think anyone that is interested in 3d printing should realize, it takes a long time to figure everything out....Your not going to unbox it and start printing your own personalized files....When I first wanted one, my wife said " I can't think of anything I'd ever want you to print"....Now she has a list....LOL....ZR
 

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Depending on the printer, you can also print in nylon. It requires tweaks, but you can print a very solid part.

The most important part with gears is the mesh between them. If you have them slightly too far away, or slightly too snugged up to one another, they'll wear out quicker. Getting that right is usually as simple as using a piece of paper to set that up.

If you cut a slip of paper up, and try to run it between the two gears, there are three possible outcomes;

1: it's too snug and the piece of paper won't go through them.
2: it's too loose and it doesn't leave crisp zigzags in the paper.
3: it's right, and it lets the paper through, but makes CRISP zigzags in the paper.

Usually I use a dollar bill as the linen it's made out of is a bit thicker than typing paper and allows a little more backlash and tends to allow better durability of gears.

-Mike
 
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