vindi93
Posts: 16
Joined: Fri Jan 18, 2019 11:14 am

Rack and pinion

Sun Mar 03, 2019 10:41 pm

Hi im new to this automation part of things. Im looking at using my stepper motor with a rack and pinion setup. My stepper motors shaft is 7mm. on trying to find a spur gear to fit it i find MOD1 sizes which seems to replace TPI. Am i right in thinking a MOD1 spur gear will fit a MOD1 rack?

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Gavinmc42
Posts: 3146
Joined: Wed Aug 28, 2013 3:31 am

Re: Rack and pinion

Mon Mar 04, 2019 2:48 am

Yep Mod1 gears will fit Mod1 rack.
Module gears are easy to figure out.
10 tooth mod1 is 10mm diameter when meshed.
However with a rack it is Pi x mod x teeth distance travelled per revolution.
10 teeth 1 rev = 31.4159...mm

You may need something above 15, 16 teeth to allow for that shaft size.

SDP/SI is my first port of call for specs, many places stock their parts.
https://www.sdp-si.com/

7mm is a bit of an old shaft size, 6mm, 1/4" and 8mm are more common.
Easy enough to get smaller hole size and drill it out.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

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OutoftheBOTS
Posts: 711
Joined: Tue Aug 01, 2017 10:06 am

Re: Rack and pinion

Mon Mar 04, 2019 3:29 am

Just out of interest why are you using a rack and pinion over a lead screw or belt pulley??

There is tons of buy off the shelf and plug and play of these 2 systems

here is example of belt driver for a linear actuator https://www.aliexpress.com/item/Durable ... st=ae803_5

here is example of lead screw linear actuator https://www.aliexpress.com/item/NEW-Ope ... st=ae803_5

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Gavinmc42
Posts: 3146
Joined: Wed Aug 28, 2013 3:31 am

Re: Rack and pinion

Mon Mar 04, 2019 5:35 am

Just out of interest why are you using a rack and pinion over a lead screw or belt pulley??
Rack and pinion is quite common for the messier cutter, tolerant of dirt etc
http://www.shopbottools.com/mProducts/ShopBotdesign.htm

I have even seen toothbelts as a sort of rack, the belt is fixed at each end.
I'm dancing on Rainbows.
Raspberries are not Apples or Oranges

vindi93
Posts: 16
Joined: Fri Jan 18, 2019 11:14 am

Re: Rack and pinion

Mon Mar 04, 2019 10:29 pm

i am building an automated fish feeder so i dont really want a lead screw design as it needs to be fairly compact but still run a linear motion.

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