Quote:
Originally Posted by JeremyLansing
Well, I guess you learn something new every day. How long were these around in the kit of parts? Those threads are from 2002, were they used any other year? Did people use the "built in" output shafts much, or did they typically stick something else on top of it? 36 diametral pitch seems like it would be difficult to source parts for, especially before the proliferation of FRC specific suppliers.
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The Atwood version of the CIM was only in the 2002 kit; teams received a matching cluster gear, which they often modified to suit their gearbox arrangement. Some also bought trailer jack kits to get further matching reductions. The motor gear is ridiculously difficult to match with off-the-shelf gears, not so much because of the pitch (because 36 diametral pitch is fairly close to 0.7 module,
1 which is available—though not always reliably or cheaply—from a couple suppliers), but because of the 25° pressure angle (20° is common for metric gears; 14.5° and 20° are common for Imperial gears). Note also that 2002 rules were very restrictive about which suppliers could be used. No matching gears were available from Small Parts (now Amazon Supply), and no other finished gear vendors were permitted. Gears could be cut from stock that was on the permitted additional hardware list. I believe custom gears cut by wire EDM were used by several teams.
From 2003 onward, versions with an Ø8 mm shaft were provided. (There are actually several almost-identical versions, depending on the year. Some differ in part number, because CIM makes them either for FIRST or for vendors who cater to several markets; some versions are physically different, mainly in the keyway profile.)
1 The pitches (36 vs. 36.2857) are close enough to probably work with a centre distance adjustment, but not exactly ideal.