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One of the most difficult and yet common mechanical systems is a gear train. A great way to transmit mechanical power from one place to another or to increase or decrease power (torque) or increase or decrease the speed of something.

The problems are always that to make efficient gears needs quite a lot of drawing and mathematical skill as well as the ability to machine complex shapes.

For a lot of amateur work it isn't necessary to have maximum efficiency and therefore we can get away with a much easier to make, even with hand tools, system.

A gear is basically a series of teeth on a wheel.

http://automata.co.uk/gears.htm

provides a very good explanation of how gears work and how to work out gear ratios.

(Note in the diagram above they have labeled an incorrect number of teeth on the gears - sorry)

Step 1: Formula and Maths (the bad news)


Formula for drawing and making gear teeth are all over the web BUT they seem, to the beginner, very complicated.

from http://www.engineersedge.com/gear_formula.htm

So I decided to simplify the issue and it works very well at both large scale and small scale. At small scale it works best with machine cutting with laser cutters for example when very small gears can successfully be made this way.

<p>I have a 53mm diameter robot arm. The shaft of the servo that rotates it is off-center, obviously inside the arm. The distance from the shaft center to the arm is about 17mm. Therefore the diameter of the pinion gear will be around 34mm. In order for the arm to rotate centered (without blocking the interior wire passages with an attached artificial shaft) is to create inward facing teeth - an internal spur gear with an outer diameter of 53mm. So in the real world, these are the parameters we begin with:</p><p>Maximum diameter of confinement: 53mm</p><p>Pinion gear diameter: 34mm</p><p>So now the question is how many teeth each of the gears should have. I have not found the maths for this anywhere on the internet. This is a real world example, and I claim that all the lessons on how to build gears ignore the most crucial factor when determining the number of teeth for each gear: The confinement area.</p><p>Can anyone please help who actually has real world experience (so you can relate to building gears other than classroom theory)? Thanks.</p>
<p>1. This idea works well for simple low tec and low force gears. You have to select the tooth circle size to suite the diameter you require. It may not be possible to get all sizes to fit as the gear teeth must be the same size on each gear which now defines the diameters of other gears.</p><p>2. I am a honors degree qualified engineer I somehow resent the suggestion I don't have real world experience. I worked in various high tec Industries for 28 years before becoming a teacher. I could do your calculations for you if I have all the relevant information but I won't you should be able to take the information given and turn it into what you want - That's called understanding,.</p><p>3. IF you want to manufacture &quot;real&quot; gears then you need to follow some of the links I supplied particularly the </p><p><a href="http://woodgears.ca/gear_cutting/template.html">http://woodgears.ca/gear_cutting/template.html</a></p><p>link which is a gear calculator package. You will find many on line that should you be able to input the correct parameters will generate gear tooth patterns for you.</p><p>IF your unable to cut the gears that any competent engineering shop should be able to cut them to your specification.</p>
<p>This doesn't make any sense. I have two specific diameters. I need to calculate the number of teeth to make the teeth mate. One diameter is 34mm and the other is 53mm. These are not negotiable for my project. The 34mm gear is an external toothed spur gear and the 54mm gear is an internal toothed spur gear. So the question everyone must be asking is, what is the maths required to calculate the two integers? If you don't care what size each gear is, then you are not needing actual gears for a real world application. Please explain the calculation of how many teeth are required for any two gear sizes in a way that results in the teeth mating accurately. Like I said, my ratio is 34:53, external spur pinion and internal driven spur wheel.</p>
<p>You know what, I think you are entirely obfuscating what you think you want. Upon rereading your comment you just need a gearing RATIO of 34:54, and you think that what this means is the diameters are 34mm to 54mm, they would be if two circles could spin (they wouldn't, you'd be off by a factor, besides the point). <br><br>You want 34 TEETH to 54 TEETH which is a different diameter. Odds are you'll need to have multiple stages, but otherwise you want a .6296 ratio. So if you had a 8.18t pinion gear you'd want a 13t pinion gear. Play with the numbers and you realize you can go with a 10t pinion and a 17t spur gear, that comes pretty close to what you want, that being said you need to come up with your own solution, or provide more details on your needs. That is after all why people pay engineers. </p>
<p>That's unfortunately not how the real world works. A &quot;real world application&quot; would involve the engineer planning a little ahead of time ;)<br><br>Two gears meshing has a lot of very specific requirements. Not only is that not how a 34:53 gear made, the exterior gear would have to be non-circular in order to spin around (or the middle gear is not circular). </p><p>If you are looking for two gears like that I would suggest a custom gear solution, it'll cost $1,000 to a few thousand each pair. </p><p>Otherwise, work your system around. There are plenty of compact gear ratios like planetary sun and moon gears that might only set you back a few hundred if you don't want to just use metal spur gears over multiple stages.<br></p><p>http://www.rushgears.com/ has a great collection of all the possibilities while using spur gears. </p>
<p><a href="http://woodgears.ca/gear_cutting/template.html">http://woodgears.ca/gear_cutting/template.html</a></p><p>may better suit you</p>
<p>I don&acute;t know how did you learn to count in school, but it seem to be that the small gear has got only 5 teeth (a 5 5 cavities, wich do not count as teeth). The same happens with the drawing of your explanations</p>
<p>Dude, if YOU didn't understand his wording, the insult is unnecessary. Just ask what he meant or look elsewhere, but saying that he wasn't taught how to count is unnecessary and just shows your incompetence and ignorance.</p>
<p>Thanks.</p>
<p>I don't understand this. Can you please tell me, possibly in simpler terms how to make a gear or a set of gears?</p>
<p>How can I describe this easier?</p><p>Sort out the number of teeth you need</p><p>Decide on either the diameter of the gear or size of the teeth this will allow you to do the calculations - Divide the length of the circumference of the gear by the number of teeth this will tell you how big the circle needs to be.</p><p>Or you can try here</p><p><a href="http://woodgears.ca/gear_cutting/template.html">http://woodgears.ca/gear_cutting/template.html</a></p>
<p>If you want to make your own wood tool yourself just look for woodprix website. There is all you need to make it :)</p>
<p>I don&acute;t know how did you learn to count in school, but it seem to be that the small gear has got only 5 teeth (a 5 5 cavities, wich do not count as teeth). The same happens with the drawing of your explanations</p>
I learned to count very well thanks. <br>However I perhaps did not express the idea quite as succinctly or precisely as I should have.<br><br>Text corrected.<br><br>(i will restrain myself from commenting on your spelling.)
<p>hallo sir</p><p>im going to attempt making my own 90 degree diff gears/ these will hopfully be driven by the wind for very small tasks. time is never a factor in my world. but i want to drive small machines and follow in the old steam fly wheel way/ wether water or wind. and in my city we have an endliss suply of wind. i wish to be able to put a saw blade to a log and let it carve its way threw. yes im nuts. thats why i dont mined trying differant opptions. any advice you could offer i would be humbled. ta rolfo</p>
<p><a href="http://www.vintageprojects.com/machine-shop/power-hacksaw-plans.html">http://www.vintageprojects.com/machine-shop/power-...</a></p><p>A good sound plan to build a powered saw.</p><p>If you want to try wooden gears you may be better off looking at how wind mills and water mill gears were made. Yes they were wood and they did withstand heavy loads (at low speeds) so you may be able to do this.</p><p>I would reduce the speed of the wind mill by using pulleys and belts rather then gears as wood gears at very high speeds are less reliable.</p><p>Accuracy will be important to get a smooth running system.</p><p><a href="https://www.google.co.uk/search?q=water+mill+wooden+gears&biw=1920&bih=953&source=lnms&tbm=isch&sa=X&ved=0CAYQ_AUoAWoVChMI0vGSwez7yAIVC1wUCh2zBwC1">https://www.google.co.uk/search?q=water+mill+woode...</a></p>
Thank you very much!!! Excelent tutorial
<p>congratulations on an absolutely brilliant idea for making gears not merely easily but ridiculously easy. Your design may be used for all sizes of gears and almost in all metals which are workable by hand tools. These circular teeth gears are not to be considered as some sort of apology for the real thing. These gears are the &quot;real' thing. Absolutely superb for craft work, working models and just about any device or mechanism requiring gear sets. If they are greased or even run dry the operate totally satisfactorily. I have used your design for the knee joint on a brace. Congratulations and all the very best to you.</p>
<p>Your welcome - Enjoy.</p>
<p>Thanks for sharing! If you need PDFs with technical documentation see our <a href="http://www.varvel.com/en/download/catalogues" rel="nofollow">gearboxes catalog</a> or get in touch for CAD models!</p>
<p>This is great, thanks! I will try this design on my 3d printer. I am trying to use gears to help kids in 6th grade understand ratios and proportions with a hands on application. Love that it includes a lot of circle calculations. Any suggestions on simple applications of these gears?</p>
<p>You could always make a simple drive train, using about 2 big gears and 2 small gears to make a slow input into a faster output.</p>
<p>I got the program Gearotic and it has changed the way how I draw gears it has made it so simple, Check it out.</p>
if making gears is too difficult, you can use sprockets like I made here:<br>http://www.instructables.com/id/simple-wooden-sprocket-without-cnc-machines/<br><br>but good work rickharris
I'm intersted in making gears and I've read somewhere that gears are the hardest mechanical components to make without proper tools.Your instructable is good and teaching from this point of view.
Thanks - To make correctly shaped gears is a little more complicated - there are lots of on line calculators and explanations of why they are that shape.<br><br>This is a way to make gears at home that for low pressure system work quite well. <br><br>large size you can make with a drill and round file, smaller sizes really need some kind of machine to cut them. A laser cutter works very well as in my picture.<br><br>thanks again.<br>
Nice article, <br><br>Just bear in mind, there are very good reasons why gears have the profiles they really do !
:-) Yes I know - BUT for much hobby use the sinusoidal gear if not heavily stressed works as well and is much easier to construct with very basic tools.<br><br>Remember for hundreds of years Windmill manufacturers got by with simple squirel cage and pin gears.
You'd like Mathias Wandle's gear generator Rick. Steve has it, it's brilliant.<br> <br> <a href="http://woodgears.ca/gear_cutting/template.html">http://woodgears.ca/gear_cutting/template.html</a><br>
Yes I have seen that and used it - Works great and his wood work is fantastic. <br><br>There are other sites that provide gear drawing software as well - I believe inkscape has a gear drawing engine in it .<br><br>This is just a very simple way for someone to do it with basic compass and pencil tools.
I'm a big fan of Wandle's site it is defiantly worth looking at
Very useful.-

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Bio: Retired technology teacher - 2 kids, I have an Hons deg in Design and Technology - 28 years as Computer systems engineer Trained as Electronics engineer in ... More »
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