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Originally Posted by Arefin Bari
High Gear max output RPM – 742.50
Low Gear max output RPM – 185.63
108’s 2003 transmission had all the reduction done inside and output was the wheel. We had a lot of problem with that transmission. It broke quite a few times, bent a lot of shafts. Let’s put it this way… we took apart and put together that transmission 16 times at Florida regional. Personally I don’t like to do inside reductions, because it gives me an option to put the transmission wherever I want on the chassis.
I am not worried about the weights. It’s 5 pounds, and I think I can kill 10 pounds on transmission out of 120 pounds. Yes, every ounce helps. Maybe I shave the gears more, maybe will do some CNC on the plate. But that is after I know the transmission works perfectly.
I didn’t understand your question about the dog. If you were asking why it is not inline all the way, its because I left it out in the drawing so everyone could see what the dog looks like. In reality the dog will be engaged with the gear at all time while running.
No I am not using any bearings. I am doing it just like any other dog shifter where you have a pin that is moving the dog back and forth with the pneumatics.
Tooth counts:
Cim Motor – 12 tooth… meshes with 60 tooth gear… on the same shaft there is a 30 tooth…. Next shaft over (shifting) another 30 and a 60 tooth. output of the transmission there is a 10 tooth sprocket. Easy and simple.
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First, I'm not quite sure I'm understanding your ratios. In high gear, is this the sequence 12T meshes with 60T that meshes with 30T and dog engages 30T to output shaft? If so, you are looking at a much higher output rpm than 742. More like 2120. If how I understand the setup is the way it actually is, the 60 tooth gear is merely a means of transferring power in high gear. It provides no reduction. To me, it looks like your high gear reduction is 30:12. If what I have said is true (and it might not be, I could just be really missing something, but I think it is) then I get 530 rpm for your low gear. Were the rpms you quoted after your external chain reduction?
That aside, I'd like to know a little bit more about the 2003 transmission. Do you have a picture of it? As far as direct drive goes, that is a very good point that without it you can put the transmission in many more places. Personally, I like to avoid the extra chain to tension, but it is all a matter of preference. There are benefits and detriments to both ways.
For weight, does the 5lb include motors? If so, that is excellent. Even if not, you are still doing okay. Our HexaMax gearbox was a beast 13lbs each (including the three motors).
For the shape of the dog (the shape of the actual green dog, not the position of it on the hex shaft), I'm curious as to why it is not something like in this picture
http://www.team696.org/hexamax_ratios.jpg where the dog fingers/protrusions are timed to be inline. Back to back fingers and back to back pockets instead of finger back to pocket like you currently have.
Finally, I know how the actual dog shifting works (I designed/built one -- that was fun
) but my question was with regard to the gears with the dog pockets. They cannot be rigidly fixed to the shaft. They must have some provision to spin freely. In your design, what is that provision?
Looks good. Keep making progress and one day soon, hopefully you'll have a bunch of shiny new parts fresh out of the machine.