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Originally Posted by sanddrag
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. |
Let me give it a try one more time. On the cim motor output I put 12 tooth gear on. which meshes wtih the 60 tooth gear, as the same shaft as the 60 tooth gear there is a 30 tooth gear (1st shaft). Next shaft over (2nd shaft) I have another 30 and 60 tooth gear. the 60 meshes with 30 and the 30 meshes with the 60. The configuration shown in the picture is for a robot with 4" wheels (wheels would have a 24 tooth sprocket on it).
I don't remember the whole configuration of 2003 transmission by heart (its been a while). I don't even have any pictures either to share wtih you.
The transmission (without the motors) weighs 5 pounds.
I wanted to try something new. If you look at different transmission, every single dog doesn't look like team 696's dog shifter. There are a lot of other options and other way you can design it and still accomplish the same thing.
On the last shaft (where the shifting is taking place), the gears has pockets (yes it needs to be done with a CNC), the dog sits perfectly inside the pockets of the gears. The gear pockets and the dog is also a bit champfered so it engages better.
Thank you for you comments and suggestions.
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Originally Posted by John V. Neun
It is exciting to see someone post something that looks like it could actually be built.
Excellent job Arefin, you've come a loooong way!
It is apparent you've put some serious time in on this design.
Of course... now you know my advice for the next step.
Keep tweaking/tuning!
The shifter may need a little bit more work. As others have said, you may be able to get some more weight out of it; but making up a quick lightening pattern for a gear is something that can be done later.
Props, for making both gearbox plates identical (and also for accomplishing the entire design with only 3 different gear sizes!). Two plates, 2 shafts... simple and elegant. It shows you've put some thought into the design. (As opposed to some transmissions, which contain 20 different plates, some of which cannot be made outside of the magical world of "inventor").
If you tell me you've got a print-package made up, I may just wet myself.
Kudos,
Can't wait to see the next revision. (No, you're not done yet. You still have 4 months.)
-John
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I didn't want to make another post... so just editing this one.
The credits for this transmission goes to John V. Neun and Andy Baker, the two who taught me how to design a gearbox.
Yes John, the transmission needs a lot of work. But I had something to show to the community. I wanted input from everyone, so I could use them while modifying this.
I am not happy with this transmission just yet... V.2 is yet to come...