Hi Crusher!
I used the Spur gear generator add-in in Fusion 360 to generate the gear, but there are also many online generators:
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http://geargenerator.com/
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https://woodgears.ca/gear_cutting/template.html
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http://hessmer.org/gears/InvoluteSpurGearBuilder.html
For my main gear, these are the parameters:
- Diametral pitch: 3.175 cm (1.25 inches)
- Number of teeth: 44
- Pressure angle: 20
For the pinion gear it's the same parameters but just 7 teeth.
Then I used the 50 rpm (no load) gear motor to drive these gears to get the wanted swing speed:
- 50 RPM * ( 7 / 44) = 7.95 RPM (no load)
The swing speed from the CAT 390F official specifications is 6.2, so with load I believe my speed matches that pretty well.
I did it like this mostly because I couldn't find a gear ring that would fit and also in a way that I could cut it on my CNC. I wanted an internal gear, but my cutting bits for my CNC aren't small enough to cut inner gears, so it had to be an external gear. But I think external gears look cool, though, so all was not lost. :-)
Later I've been thinking that I should rather not cut the gears myself, but use some more time to find gear rings on the net that I could use.
I'm really happy about the track pads. They really hold up great! Not one have broken so far, even as the machine now weighs 30kg (60lbs). I was initially planning to mill them all from aluminum, but now I'm thinking that if some break, I just print some new ones.
On my 3D printer, it takes about two days of continuous printing to print 80 track pads. I have a Makerbot Replicator 2X.
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http://store.makerbot.com/replicator2x
But that's quite an old 3D printer. I think these days, you can get better offers. The only important thing is that you can print ABS, because it's so much tougher than PLA (less brittle). And you need a heated build plate for ABS printing. Maybe one of these could do the job:
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Ultimaker 2
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Zortrax M200 Pro
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FlashForge Creator Pro
I've not tried any of them, but I've heard some good things about them and the specs look ok. There's probably lots of reviews on youtube.
Best regards,
Stein :-)