Author Topic: Tracked Drive Robot - Where to find a 65 tooth 1/2" pitch #40 chain sprocket?  (Read 1375 times)

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Offline ubiqtusTopic starter

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Greetings fellow roboteers and happy Independence Day!   

Forum and robot newbie here. This is only my second robot, counting the ultrasonic sensor attached to a headless raspberry pi that I pushed around on a skateboard.  Nevertheless, I'm willing to fail miserably in exchange for the excitement in 'punching above my weight class'  and am very appreciative of this site, including the invaluable info and advice I've found on this forum. 

My current project I'm working on is building 2' x 3' tracked robot that I can climb 7" x 11 1/2" stairs at a 31 degree incline. 

What's brought me here today is that I cannot seem to find a particular drive component I need.  My design calls for an appx 1 lb 65 tooth 1/2" pitch (#40) sprocket (chain ring). My internet searches generally lead to sprockets that are too small, or too heavy. 

The reason I need one this size
1) The wheel I am using it for is appx 10.5" diameter (for climbing stairs)
2) The best part I can find to use for treads use 1/2" #40 chain for drive:
843-K200 CHAIN specs:

I wonder:
- Since I can find suitable sprockets with a different pitch, would I have better luck finding different treads? 
- Any places that will provide 2 custom sprockets without requiring me to mortgage my house (though, building my own CNC machine is rather enticing)?

Thanks - and happy 4th everyone!

Offline waltr

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Check McMaster-Carr.

Offline jwatte

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Having two custom sprockets made does not require mortgaging your house, and is cheaper than building your own CNC capable of cutting aluminum or titanium (assuming steel is too heavy for you.)

I'd look perhaps at rapidgears.com, which cuts gears of various kinds to order.

Another option is to send drawings to an machining house. Yes, you'll pay hundreds, but probably not thousands, especially if you can make the drawings yourself first in something like Inventor (there's a free 30-day trial.)

Finally, consider 3D printing. I think 3D printing in steel or nylon will be a little to expensive, heavy, and/or fragile for you, but at least consider looking at Shapeways.com and see what it would be. Nylon is $1.40/cc; steel is $8/cc.

Offline ubiqtusTopic starter

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Thanks waltr and JWatte for the suggestions.  The shapeways.com site looks interesting if I ever get around to designing custom CAD parts. 

I was inspired to Google further and found a GoKart supplier that should fit the bill for a little over $100 for the pair plus shipping:


Now I just have to break out the moolah and start building the thing   8)

I have an 11" plastic wheel that I'm going mold a trench for the sprocket and chain, saw in half, and then glue back together like a sandwich (can add some bolts for strength if needed).  It might be an epic fail, but if it works, I'll have a kick ass front wheel drive for my tracked bot.

A few helpful links I came across regarding chains and sprockets just to share:
Chain guide: http://jleibovitch.tripod.com/id240.htm
sprocket guide: https://www.applied.com/static/catalog/pdfs/allsprockets_e132_e174.pdf (pg. e-153)
Thanks again,
« Last Edit: July 05, 2013, 06:20:23 PM by ubiqtus »


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