The crank is used to convert rotary motion to reciprocating or oscillating motion. With careful timing it can also be used to convert motion the other way... from reciprocating to rotary.

The throw of the reciprocating motion is determined by the offset of the crank

Make your own working crank mechanism. Download and make this model and find out about cranks first hand. More info...


Monday 11th Oct 2010 17:37

im doing this in tech in school its really hard

Monday 11th Oct 2010 19:05


robives's picture

Anything you want to know? I might be able to help. 


Tuesday 19th Oct 2010 19:33

Aha, so are we. It's so hard!

I don't understand most of it :P

Thursday 21st Oct 2010 03:03


Hello Rob

I am a Technology teacher in New Zealand who teaches a Automata unit to yr 9 students (13-14 yrs old). I have found your resources to be fantastic in helping the students to understand mechanisms. The photo is a Automaton by one of my students, it is a 'Shuffler' ('shuffle' is a type of dance) and it uses a crank and lever mechanism.

Thursday 21st Oct 2010 13:06


robives's picture

Fantastic! Thanks for sending in the picture, that shuffler looks great.

Tuesday 2nd Nov 2010 18:47

hi rob, do you know what type of movement this mechanism moves in please???? x

Tuesday 2nd Nov 2010 20:27


robives's picture

I'm presuming you are talking about the photo sent on by DCJ ? I'm not sure but it looks like it might be a crank slider. Wire crank in the box, wire push rod from the crank, up through a hole in the box top connected to the dancer. Is that right DCJ?

Wednesday 3rd Nov 2010 12:01

Hey just wanted to say thankyou very much for this extremely usefull Website, im using it to help me gain a good understanding of that different type of mechanisms that i could feature in the product that im designing. this site has really helped me with my tech coursework, keep up the good work !!

Wednesday 3rd Nov 2010 19:01


robives's picture

Thanks! Glad to be of service :-)

Saturday 6th Nov 2010 12:16

hi rob im making a golf ball dispenser and i was wondering if u knew wat type of mechanism i could use so that one ball comes out at a time?

Friday 26th Nov 2010 17:05

Hi there! I would just like to ask, is crank a suitable mechanism on a model that has a train track with a train going from left to right and vice versa?

Friday 26th Nov 2010 23:00


robives's picture

You could use a crank to make a train go back and forth but the motion would be limited to the length of throw of the crank.  A pulley or belt drive might be a better solution

Friday 4th Feb 2011 02:54


Yes, the mechanism is a crank, the wire pass thru a restricted hole that makes the legs move in a circular movement. The motion of the legs is quick in its lateral movement giving the 'shuffler / jerking' effect to the dance.

On an aside note, the school subscription sounds like a great idea.

Monday 7th Feb 2011 08:22


Hi Rob,

I need to design a mechanism that convert reciprocating motion to rotary motion. I have several ideas for

the other way, but this conversion is a little difficult.

It says above, that With careful timing the crank can be used to convert that kind of motion.

What does it mean? How can I do that? if the motion is coming from the left, the wheel is not doing a

complete round.


Monday 7th Feb 2011 16:26


robives's picture

@yasminh This is basically what a piston does. You are correct that the motion is not powered all the way round. Push the piston and the wheel will rotate half way round, the piston then relies on the momentum of the rotating wheel to keep it moving back to the start position.

Tuesday 17th May 2011 10:08

Hey robives, your website is great, it is so simple and cuts out all the bull.

Have you considered making an electronics site ?

Sunday 22nd May 2011 16:39

What kind of mechanism would I need for a flying pig?

Monday 23rd May 2011 05:54


robives's picture

The Flying Pig uses a crank slider mechanism.

Thursday 23rd Jun 2011 02:20

rotary motion transfered to reciprocating motion as I understand it.

Wednesday 19th Oct 2011 19:26

i don't get this

Wednesday 23rd Nov 2011 02:26

Gah! I thought I already found what I was looking for in the quick return mechanism but this crank animation is very similar. In the animation above where the movement is converted to swinging an arc, is the left-right to right-left movement swinging at the same rate? or is one slower than the other?

Wednesday 23rd Nov 2011 02:31

Between this and the quick return mechanism...(using the animation above) is the left-right to right-left motion moving at the same rate?

Wednesday 18th Jan 2012 19:06

heya im stuck on drawing a diagram for my flying horse im using the crank any clues?

You might be better with a crank slider - RI

Saturday 21st Jan 2012 17:54


Rob, I am doing a school project on mechanisms, but I can't think or find any examples of a product (object/item) which uses this mechanism. Can you help me?


P.S. This website is so cool and has been a great help!

How about a mechanical hacksaw or windscreen wiper blades?- RI

Sunday 22nd Jan 2012 15:42


Thank you so much! 


Tuesday 29th May 2012 19:04

Is there a crank on a bike and where is it and what is its function 

Thanks :)

The crank on the bike is the pedal. It is used to convert downward force from the leg into rotary motion in the wheels - RI

Sunday 10th Jun 2012 14:13

Rob could you tell me some examples, in which a crank is used in.

Bicycle pedal, petrol and steam engines, mechanical hacksaw, windscreen wipers... - RI

Thursday 27th Sep 2012 11:50

Hi Rob i just want to say that you are a amazing person with great taste in mechanisms and clothing.

P.S i like your glasses

P.S.S what are cranks used in 

yours sincerly joseph

Saturday 3rd Nov 2012 12:41

thank you for this great site. i am 12 years old and doing automata in D.T. and this perfect for me, and i highly recommend this site to any one doing automata.

Sunday 27th Jan 2013 14:30

Hi Rob I need to convert circular motion to vertical straight up and down movement, how do I do this?

Try using a crank mechanism like the video clip at the top of the page, turn it through 90 degrees and the piston would move up and down rather than side to side. - RI

Sunday 6th Oct 2013 14:57


I want to use this pattern to move a sculpture ( that weights about 300gr) and has a 40 cm rod, how big does the connecting rod needs to be ? How can I calculate this?


Thank you


What range of movement do you want? - RI

Saturday 19th Oct 2013 18:05

what is the throw and offset

The throw is the total distance moved back and forth, the offset is half that. - RI

Tuesday 24th Jun 2014 13:00


Why dont people create an account it saves robbie having to approve requests every two minutes go on give it a go and sign up


Thanks A Bunch


Wednesday 12th Nov 2014 05:17

I am trying to convert the oscillating movement of the crank to rotary movement, and it seems impossible. Any suggestions?

Yes, you'll need a flywheel. A heavy wheel that will keep turning when the crank is at the extremes of its movement. - RI