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K'nex Gear Ratios Answered

What Ratios Do the K'nex Gears Produce?

I have noticed there have been a lot of questions about gears for k'nex models and in particular, engines but there have been no documents or information on what the different gear combinations actually convert the input speed to.

On the document attached there are the worked out combinations and what the speed produced is, but you will notice that the combinations only go up to three gears; this is because if you have only three different gears, you will have to repeat atleast one gear therefore the ratio would be able to be created using less gears as intended. 

The new file has now been uploaded.

I hope this helps.




3 years ago

This is useful, Im surprised I hadn't seen this earlier.


3 years ago

I just need a 1:2 gear ratio or my clock.

This is great to make available-- just the three-gear table is not necessary. The B+M+S is exactly the same as the two gear B+S [the slight difference you have is rounding error].

To get additional gear ratios, you have to build gear trains by locking two different sized gears together on a single rod.

IE, lock a medium and small gear on a rod [lets call it SM to follow the notation in this document. Connect that up as :

M + SM + S and then you'll have the M+S [2.429] ratio times the M+S ratio [2.429] = 5.90:1 -- which gives you almost exactly the same as the B+S ratio, but without using a big [and on ebay, expensive] gear.

On my desk, I have a gear train that is:
B + SB + SB +SB +S = 5.86 x 5.86 x 5.86 x 5.86 = 1179:1

The left-most big gear is almost impossible to turn [a little grease would probably help that], but the right-most gears turn extremely fast... spinning the right-most small gear as fast as I can moves the left-most gear almost imperceptibly slow... :)

I did have another BS in there, but couldn't move it at all [almost 7000:1]

This is straight up amazing. Thanks very much!

Nice. Was that done through observation or math formulas? You would probably want to list the number of teeth in each gear to help with the description of small, medium, and big gear.

It was done through a Maths formula to work out the amount of rotations produced from one rotation of the input gear, and thanks for the advice I will update the file ASAP.