Core Electronics Forum

Rack and pinion for Parallax servo

hi everyone!

I have this Parallax servo: Parallax Feedback 360° High Speed Servo - Parallax

What I want is for it to basically drive a rack and pinion to create linear motion. So what I am looking for is an off the shelf pinion gear for this servo (apparently 25t splined 6mm shaft) and ideally a rack to go with it (though I might be able to 3D print the rack worst case).

Any ideas on part/supplier?

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Hi Kaveh
Try Google “rack and pinion linear actuator” or try Linear Actuator – Vevor AU.
Most seem to be complete with motor or there are several screw types around. I think RS Components seem to advertise the “rack” bit on the Google search page but without being able to open the web page (I use a Mac with Safari browser which won’t have anything to do with Java or Adobe Flash) I have no idea. I can open these pages with Firefox but have not got the time at the moment and this is something you can do yourself anyway.
Cheers Bob

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Hi Robert,

Thanks for the pointers I will have a look.

I noticed there appears to be some sort of standard when it comes to their sizing, for example looking at Rack and Pinion Drives | Statewide Bearings, it shows a table of ‘gear sizes’ e.g. “Spur Gears 0.3 to 18 Module”. Is ‘module’ a sizing standard and if so, what equivalent size is the Parallax?

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“Module” I have no idea. Might be related to gear teeth. I just don’t know and would be guessing.

What is the attraction in using a continuous servo. I would have thought steppers would be the go for this application. Although having said that I/we have no idea what you are doing here and you have not indicated.

You obviously have a 3D printer. Have a look at that. They makers have done exactly what you are trying to do, convert rotary motion to linear. You may get some ideas here.
Cheers Bob

Hi Kaveh.
Google “spur gear module”. Lots of information and u-tube videos.
Cheers Bob

Hi Bob,

Thanks for the input, will do some more research in those areas and look at steppers again. We are trying to build something that cuts food but needs some decent force and steppers didnt seem to be able to handle it, but i’ll look again.

Hi Kaveh
How about a geared motor with a disc on the output shaft. This could then be attached to the horizontal rack (for want of a better word) by some sort of connecting rod so the whole thing acts as a crank which drives the “rack” back and forward. This has the advantage that there is no need to reverse the motor making driving said motor easier.
Cheers Bob

Thats a very interesting idea and gets around the need to obtain positional information from the stepper motor or servo! Let me have a think on it :slight_smile:

Thanks again!

Should work. The disc diameter or the distance from centre to con rod connection point will determine the stroke length. Could be made variable with a selection of attaching holes.
Cheers Bob

Yup… This could be a winner - will get to work!

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