Although functionally the same, our drivetrains are very different at the part level. 254 makes no parts for us, and we make no parts for them. We're certainly buddies with 254 (and they/968/60 certainly inspired our design style), but we each run our own show.
What I meant by the same geometry, was the same overall gear setup. We don't use AM's stock shifter setup. We get dog gears custom cut each year per whatever ratio we need. It's a pretty simple operation for a CNC, so sponsors are willing to do it.
I also left this out of my previous reply, but it's possible to make this style drivetrain with zero CNC equipment (more parts on our current drivetrain are made on manuals than you would think); 973 did that from 2005-2008 (single speed through 2007, SuperShifters in 2008).
Quote:
Originally Posted by JesseK
I get that 'sprint distance' concept; it's why I made my "gearing vs time" charts in my recent calculator. Other than that, a couple of things --
I was under the impression, from talking to kids on all 3 teams, that the drive train gearing between 254, 973, & 1868 were identical. Due to the collaborative nature of the machine shop setup (which is great, imo) I presumed many discussions and similar conclusions were made.
I'm having difficulty getting the geometry for less than 18ft/s correct by using 3.5" wheels, the 15:48 & 28:35 combos for the shifting stage, and 11:40 for the first stage; this is why the presumptions were made. It's easy to get less than 18ft/s after adding a 3rd stage, but that's extra weight/inefficiency. Increasing the 40T gear on the first stage interferes with the dog gear; decreasing the 11T pinion further to a 10T pinion without increasing the 40T gear causes the CIMs to touch (at least). For anyone wishing to use the COTS solutions from AndyMark without extra milling on the gears for the dog gear setup (such as my team), this is what we'd have to use.
So really, I have difficulty in understanding how you get the dimensions needed for 13.5 ft/s in the same geometry (2 stages of reduction); it doesn't work out for me.
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