Slickest drive transmission yet...

[artic_raven]

i am sorta new to all of this. would it be possible for someone to e-mail me an inventor file for a 2 speed transmission. that would help us out alot!! also if its possible please send the specs of the transmision (i.e. gear ratios)

thank you!!!

[sanddrag]

Originally Posted by artic_raven

i am sorta new to all of this. would it be possible for someone to e-mail me an inventor file for a 2 speed transmission. that would help us out alot!! also if its possible please send the specs of the transmision (i.e. gear ratios)

thank you!!!

Have you looked in the whitepapers? There is a lot of info there.

[ChuckDickerson]

Is there any timeframe on when the companion automation software paper will be available? Our team would really like to see how you automated the shifting. Will it be available soon so that we may decide if it is something we can tackle this year or not? Even just some pieces of code would be helpful at this point.

Thanks!
Chuck D.

[cabbagekid2]

I too would love to see the code for the automatic transmission. Would any team be willing to post the automatic transmission portion of their code on this site? Even pseudocode would be helpful with our designs since we have never attempted this before. Thanks!

[Jim Zondag]

I have posted the design for the Killer Bees' 4 speed transmission on the White Papers board. Because the Inventor Files are so big, I could not post them all here, they are available for Download from the Killer Bees Website at http://www.ndprep.org/robotics/archive.htm.

[JVN]

Jim,
GREAT paper! Thanks for sharing.
I'm sure this will help out quite a few teams in the 2005 season.

I love the way you illustrate the power curve comparison for a 2 speed vs. 4 speed design. This is something I will show our students to help them understand these principles.

Thanks again,
John

[Billfred]

If I were drooling any more, I would short out my laptop. Great work!

[sanddrag]

I used to not like gears slamming into other gears, but I've seen it done so much that now I'm starting to really like this thing. It is totally not the way I would design a transmission, but the way I would design it would require twice as much time to build. This thing can be busted out in a few good nights at the machine shop. I really like the simplicity.

Do you have any (could you make some) pseudo-code on how it is programmed to shift?

[1028_Machinist]

Having a shifting transmission is deffinatly a helpfull and worthwile modification; especially when you don't even have to worry about shifting. The only problem that i can see that might go wrong is that if you hit something at full speed and the wheel speed sensor gets knocked off or is rendered unable to sense wheel speed, you would be stuck in the gear that the robot was in before the sensor was disabled. Especially if you were in 4th gear. That battery might not last much longer!

[Nitroxextreme]

Originally Posted by 1028_Machinist

Having a shifting transmission is deffinatly a helpfull and worthwile modification; especially when you don't even have to worry about shifting. The only problem that i can see that might go wrong is that if you hit something at full speed and the wheel speed sensor gets knocked off or is rendered unable to sense wheel speed, you would be stuck in the gear that the robot was in before the sensor was disabled. Especially if you were in 4th gear. That battery might not last much longer!

What do u mean by wheel speed sensor
which sensor is that?
Isn't it built into the motor?

off topic:
has anyone built that spacer for the single sprocket
if so where did u find a diagram and what matters to use

[Paul H]

In response to the above posts:

artic_raven: Cut one of these in half and you have a VERY easy to machine 2 speed transmission, not to mention tiny and light.

DeepWater and cabbagekid2: I have no idea if Jim intends on posting a software whitepaper, and if so, when.

1028_Machinist: There is no wheel speed sensor. If you look at the whitepaper, the output speed is measured by a shaft encoder. That is what the automation uses. If you knock that loose, I don't think you'd have to worry about driving around in any gear....I don't think you'd be driving around at all. You can put a manual override if you want, though.

Nitroxextreme: Wheel speed sensor would be a banner sensor (light sensor) aimed at a tone wheel. A tone wheel is basically just white and black stripes, and the banner sensor reads how fast the wheel is going by "seeing" the change between white and black as the wheel rotates. In our design, there is no wheel speed sensor, just a shaft encoder which reads how fast the output shaft of the transmission is spinning. There is no sensor built into the motor.

[sanddrag]

This is a nice easy to manufacture transmission design but the problem is that there is very little->no reduction. In high gear it is 1:1 which means you have to use some external reduction like a Dewalt drill gearbox and on the input end then maybe some sprockets and chains on the output end. Don't forget about all this stuff when looking at how light and small it is. What you see in the picture is not the only part.

[kc8nod]

I'll repeat my question from the other thread here since I haven't seen the software paper yet. Now that the season has kicked-off, I expect the last thing on your mind is documenting last year's work.

Jim, could you answer some general questions about how your software works?
1. Is shifting based on RPM alone? What other factors are used to determine when to shift? Current? Voltage? The commanded PWM value? To put it another way, are the shift points fixed, or are they different when you are accelerating at 50% throttle?

2. I assume there is some kind of hysteresis. Is it a simple pair of shift-up/shift-down values? Or do you add something like a "dwell time"?

3. Do the left and right transmissions shift at the same time? I'd imagine that keeping both sides in the same gear would make it easier to match speeds and keep the 'bot going in a straight line.

Of course I don't expect you to give away all your secrets, Gracious Professionalism or no. But some general guidance about the operation of the shifting software would be helpful.

Once again, great job 33! It's a sweet design.