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Originally Posted by Cory
Minor nitpick, but in the gear closest to us, when you try to machine what you've shown, unless you use an incredibly small endmill and make about 500 passes, you're going to end up with a round hole, and not a square pocket like you've drawn (even doing all that, it'd still be a filleted square)
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The same is true for all the cutouts in the plates (assuming the material will be removed with an endmill).
Also, I still think this can be made a good bit smaller/lighter/cheaper (about $40 in two gearboxes). Here's how.
Keep the 12T gears on the CIMs and have them both meshing with a 40T gear (instead of the 60T). Then the 40T gear meshes with the current 30T gear (no change). This concludes high gear. The CIMs will just barely fit side by side but they should definitely fit (I calculate .080 between them).
Then on the same shaft as the new 40T gear, put a 25T gear (to replace the current 45T gear there). It meshes with the current 45T dog gear. (no change) this concludes low gear.
So basically, replace the 60T with a 40T and replace the 45T non-dog-gear with a 25T.
This will give you a difference of 2.4:1 between high and low gear as opposed to your current Version Three 2:1 difference. The 2.4:1 difference could give you something like 13fps and 5.4fps.
Of course you will have to redesign your plates for the new center to center distances, but you seem to whip out new versions very quickly so I don't think it would be much of a problem.
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Originally Posted by Holtzman
I just skimmed the other two threads, and didn't see anything about this(correct me if I'm wrong), but instead of putting 8 lightening holes in each plate, why don't you just use thinner plates? I'd suggest 3/16 for the CIM side, and 1/8 for the sprocket side.
That will take out more weight than all your lightening holes, and save you time in the process.
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I know the AndyMark transmission uses .090 plates and several people have reported no problems, but in previous years I have seen dog shifting transmissions with 1/8" plates all wavy at the end of the competition. I think a 3/16" plate would be fine, but if you use traditional bearings (like the highly-recommended-by-me SPI BRF-06 and BRF-08) they will stick out beyond the plates. For Arefin's design, this would be an issue on the CIM plate but the outer plate probably wouldn't matter.
Bearings that are thicker than the plate they are in seem to work just fine (as shown by the AM and 2004 968 transmissions) but to me it just doesn't seem right.
Of course you could always start with a 1/4" plate and mill it down thinner where there are no bearings, but that is a lot of extra work.