Slickest drive transmission yet...

[Paul H]

The lead engineer, Jim Zondag, is in the process of moving into a new house and is swamped at work from what I hear. I'll talk to him at the Sweet Repeat (October 9th) and see when he's planning on posting the papers.

[Gus]

Originally Posted by Jim Zondag

Thanks, I'm glad everyone likes our design.
We have made two speed transmissions for the past several years. Each year we try to make them simpler and smaller. I found that with the kind of high/low shift range that I like to have (3:1 or more) that the robot would tend to lurch severely if you downshifted at high speeds. I really want to make a 3 speed with an intermediate gear to help this. It turned out it was easier to build a 4 speed than a 3 speed ( its really two small two-speeds in series). We focused the design around reliablity and ease of construction, the demo unit on display was made entirely by high school students in a few evenings using no special tooling.
Once I had a design with 4 gears I was pretty much forced to automate the shifting in order to keep from overloading the driver. I talked with a few Automatic Transmission experts at DaimlerChrysler on how to do a shift scheduler and viola....a fully automatic electronic robot transmission.
It really is pretty neat, providing a nearly flat power output across a very wide RPM band with a 5:1 total shift span.
I plan on posting the design and engineering here as soon as I get a good set of drawings made up (I'm not a CAD guy, I made the ones in the robot from a napkin sketch).

Would it be possible to get a drawing or photo's of this transmission. It sounds perfect. Thanks Gus

[Paul H]

Originally Posted by Gus

Would it be possible to get a drawing or photo's of this transmission. It sounds perfect. Thanks Gus

The whitepaper is coming in a month or two hopefully. It'll include CAD drawings, instructions on construction, and a generecized(sp?) version of our automation code. All you have to do is install the sensors and download the code and your transmission will be automatic...or at least that's the plan.

[TD78]

Team 33 was right across the way from our pit in Atlanta and I was over there any spare second I got to look at that demo board. When I first found out that they had constructed an automatic transmission, I freaked out. Seeing the transmission in person was something else though. Unfortunately I never got a chance to look inside their robot and see that articulated chassis that allowed them to climb the platform. I've been wanting to design my own drivetrain for the last year or so but with the lack of foundation knowledge and facilities it hasn't quite happened yet. With the new robotics club I helped start at URI hopefully it won't be long now.

I'll be awaiting for that whitepaper with great anticipation. You were without a doubt my favorite robot this season. Good luck at any off-season comps and keep up the good work!

-Tom

[ZACH P.]

Hey guys, any news on that whitepaper yet?

[Jim Zondag]

Well, I finally learned Inventor well enough to draw this transmisison up,
I will be posting this with full details in the white papers soon. here is a sneak peak.

[Elgin Clock]

Originally Posted by dlavery

Thank you very much for the kind words. Working with the team to design that transmission was a lot of fun, and we learned a lot!

-dave

BTW, Dave and the rest of the crew over on Team 116, here is our version of your designed gearbox and tranny!

http://www.pbase.com/image/26818929

[Mike K]

Just Remember to Use Hard Metal!!!!

[Paul H]

Hardened Steel is what he means. We ground down our high gear on one gearbox in Detroit.

[Elgin Clock]

Originally Posted by Elgin Clock

BTW, Dave and the rest of the crew over on Team 116, here is our version of your designed gearbox and tranny!

http://www.pbase.com/image/26818929

Apparently I got bad rep point for showing Gracious Professionalism and "hijacking this thread" to thank a team for their gearbox design we used this year.

If any one wants the name of this person who is against Gracious Professionalism and against thanking other teams, PM me.

[techtiger1]

Originally Posted by dlavery

I loved the CVT designs that have popped up a few times in recent years. But with ones like the ThunderChickens design, we could only look on with envy and the realization that it was a design we could not build without a much better fabrication capability. That is why the Killer Bees design is so brilliant - they get a similar level of performance (particularly with the automatic shifting function), but you don't need any high-end tooling to put it together. Just about anyone with access to a moderate high school shop can build it. In that respect, it is a truly elegant design.

-dave

Does anyone have that design on 217 I would much appreciate to take a look at it.Considering you guys really keep the drive train under wraps. I would also like to know the extent of the manufacturing needed for a cvt design. This is because i am not familiar with the system. Thank you and Dave you are so right 33 does have the slickest drive transmission yet.

[RogerR]

Originally Posted by techtiger1

Does anyone have that design on 217 I would much appreciate to take a look at it.Considering you guys really keep the drive train under wraps. I would also like to know the extent of the manufacturing needed for a cvt design. This is because i am not familiar with the system. Thank you and Dave you are so right 33 does have the slickest drive transmission yet

the 217 drive train and transmission is not a true CVT, but rather a modified planetary (most people refer to it as a "CCT"-Crazy Chicken Transmission). the thunderchicken website has a white paper on the CCT with an explanation a BOM and some part files.

[ChuckDickerson]

Jim,

Thank you for posting the white paper on the Killer Bees 2004 4 speed automatic transmission! The paper is excellent! I have read, re-read, and studied the paper and all of the CAD drawings until I think I just about have all of the dimensions memorized! I am amazed at the elegant simplicity of the transmission. It is truly a work of art! Our team has never built any type of multispeed transmission before but I think we might give it a try this year. We have been gathering the various parts and materials in the BOM in your white paper and are working on building a prototype to play with and see if we think it will be something we can tackle for the robot this year. Hopes are high! Needless to say, we are eagerly awaiting the companion software paper on the automatic shifting code. In the mean time I have 4 specific questions that I hope you or someone here on CD can answer.

1) The BOM in the paper calls for qty 4 3/8" wave washers. I have studied all of the drawings and can't seem to figure out where they go. What am I missing?

2) The BOM also calls for qty 16 5/16" aluminum washers which are used on the shift shafts. Is there a reason these should be aluminum (other than to save a tiny amount of weight) or could we just use standard steel or stainless steel washers? I ask because I assume there must be a reason you specify aluminum but I just don't understand at this time and that would be one less special item we have to order. Maybe it will become clear when we get the prototype/test gearbox built.

3) I am sure that this will be covered in the companion software paper but I am wondering about the Grayhill 61K64 64 pulse per revolution encoders. The 61K64 encoders have output pins designed for a PC board, which seems rather inconvenient to use on a robot unless the interface to the controller requires additional circuitry not covered in this paper. Digikey also sells a 61K128-050 encoder which appears dimensionally equivalent in all of the critical dimensions but is 128 pulses per revolution and has a cable output which seems like it might be easier to wire up than PC board pins. Is there any reason a 128 PPR encoder wouldn't work just as good or better than a 64 PPR encoder? Since these are about $50 each I haven't ordered any yet until I am sure the 61K128-050 will work.

4) In the paper you mention that you had some of the gear/shaft assemblies hardened after welding. Could you provide more specifics on the hardening process you used? Our machine shop says they can heat treat "up to 2000 degrees" but need to know what "process" you used. This is not my area I am just trying to pass along the question from the machine shop guys. Is this a special process that must be sent out to a special heat treater or is it something we can do ourselves? If it must be sent out where do we send it and about how much does it cost?

Again, thank you very much for posting the white paper on the transmission. I think there are many teams drooling over it!

Thanks,
Chuck

[Jim Zondag]

Deepwater, Thanks for the compliments: to answer your questions:
1. The wave washers are used as needed to take up lateral slop in the assembly. If you make everything perfectly, you don't need them. If you have student welders and lathe operators like I do, you may find you need some.
2. You can use steel washers if you like. We typically use aluminum washers for everything on FIRST robots. It is amazing how much easy weight you can save if you have hundreds of washers on you machine.
3. The Grayhill sensor is just a suggestion...you can use any similar device here. The number of counts per revolution you choose will depend on much resolution you need/want. I like this one and we made a interconnect so that we can disconnect it right at the transmission.
4. Hardening, I had our heat-treat lab do this for us....I told them to make them hard and they did. Being a programmer I am somewhat ignorant on the details of metallurgy...another great opportunity to learn through FIRST! I will get details and reply later.

[JVN]

Originally Posted by Jim Zondag

4. Hardening, I had our heat-treat lab do this for us....I told them to make them hard and they did. Being a programmer I am somewhat ignorant on the details of metallurgy...another great opportunity to learn through FIRST! I will get details and reply later.

Jim,
Funny you mention this.
Heat treating came up the other day in a 229 design discussion.

If you (or anyone else) knows more about this process.
Please share!

I have the vaguest understanding.
I'm especially interested in "home" heat treating. I think it is possible to temper a shaft using only a torch and a coffee can of oil. Is this true?

John