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How to make gearbox

Making gearbox out of random plastic gears and small motor.

How to make gearboxes out of random plastic gears:

 This tutorial shows how to make simple and small plastic gearbox with gear ratio about 1:100. Ratio can vary. This gearbox is good for stepper motors and other stolen motors what don't have their own gearboxes.


1. Why & what?

Building gearboxes is pain in the ass. Don't try it, it is not possible. Try to build gearboxes only when you are very poor and/or bored.


2.  What is needed?

First you have to own some thingies. All what you need in the list of importance:

* minimum 4 gears (if i say gear, i mean big and small gear attached to each other. And their teeth have to match. plastic is good. and you can get them from toys, scrapyards etc.)

* motor (DC, AC, stepper, whatever.)

* about 10x10cm(3"x3") plexi glass or other kind of plastic sheet (aluminium if you are grazy. you can get plastic from random places)

* bolts, nuts

* some tools (drill, something to cut plastic sheets, screwdriver)


3. How?

First: Take smallest gear you can find and find a way to put it on your motor shaft. Good way is drilling a bit smaller hole in and press it on. If gear fits and comes off perfectly then use some superglue. If you don't have small gear then take bigger gear with small one attached and cut off the smaller gear. If cutting off fails or is too risky then you can use big gear with smaller one.

Small gear:

 Cutting gears:

Motor with gear:

 Motor with gearbox. Double gear on motos shaft.

Second: Find a way to connect piece of plastic and your motor. It would be super if your motor had screwholes like mine. Plastic sheet should be about 5mm thick. It is possible to use thinner ones but it will only make life harder. Plastic sheet should be at 90 degrees angle from motor shaft. This plastic sheet will hold all gearbox shafts.

Third: Prepare gears. Find 1-3 double gears (small and big one attached to each other) and find one bigger one too. Big one is for output shaft and has to be at least 3mm bigger than rest of gears. I use one double gear. Then decide how big shafts to use and drill your gears according to that. I use 2mm bolt for shaft and output shaft will be 3mm bolt. Drilling have to be almost perfect. If hole is angled or too big, you have to take new gear.

Fourth: Put first gear in place (big part of gear against small gear on motor shaft), and mark place for shaft. Then drill your shaft hole and fasten a bolt to there. And no, bold will not rotate! Bolts never do. Less rotating shafts = more chance of success. After drilling, putting your plastic piece back to place and placeing gears on shafts you will probably spot that you have failed and gears will not move to right place. This can be fixed. To fix that drill plastic thingy screw holes wider and attach plastic thingy a bit further. Don't touch the shaft hole because shaft has to be strong. If you want more gears then attach more shafts.



 Failiure - gears don't match

Now, hole is not round.


Fifth: Prepare the output shaft. Drill hole for it. Attach gear strongly to shaft. When you find that hole for shaft is too close then drill it a bit wider. If all gears match and run well then attach output shaft well to plastic.

Output shaft:

All assembled:

Final: Make cover for your gearbox. It is important because all rotating shafts must be attached to gearbox from at least two places. Also it helps to keep gears in their place. If cover is complete and gearbox is assembled then all should be done!



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none of the images display?

not that anyone has ever SEEN it...



 Rue Mohr


if u found a motor with no thread holes for the bolts and showed how 2 make the holes. XD that whould be kool

I just joined and I'm still learning the ropes on this site. Here is an arm I built using the above method. Nearly all the parts, (except the aluminum bar stock), came from junked VCR's.





This arm was built about 10 years ago as a "proof of concept" to show what could be accomplished for $10.00. As stated previously, with the exception of some aluminum and misc. hardware, all the parts came from junked VCR's. The elbo joint, (shown below), is spring loaded so it offers no load to the elbo motor.

Elbo joint and driver chips.

The gripper is lined with conductive foam which forms the input to a comparator so the grip strength can be controlled.

The gripper also has an LED and photo transistor so it will close automatically when an object is within the gripper, but only to the extent the comparator lets it. The gripper is also spring loaded to open and the pull cable closes it. At maximum settings, it can crush an empty pop can. Every motor, gear, sensor, and motor driver chip came from VCR's

That's a pretty cool arm. You ought to give some details about it in it's own post! Nice work!
Is is endeed!!! I would love to see details too!! 

A better way to make your shafts / axels, is to use sections from a cheap telescopic antenna like a walkie talkie. They come in a variety of diameters, are already polished, and are pretty much free. Once inserted in place, just cut them off with a beefy pair of cutters and the end is crimped so it doesn't come out. I've used this method to make geartrains for arms and it's really simple.



I too have tried making my own gearboxes with some success. I used aluminium channel. As long as you lined up the holse just right and drilled at 90 degrees (I used a drill press for this) then the result was small and strong. I even glued in some small bearings from RC cars.

And I thought this was almost an impossible thing to do... you've made it possible from now on!!

good work ;)