A few gearbox questions
 

Ok, first here is our gearbox setup. We combine the CIM's and the drill motors together in a very simple design where we matched the RPM's using gears and chains. More specifically we are using the drill motors inside their normal transmission supplied by the KOP, in low speed, with the backdrive-pins taken out and on the 15 clutch setting. Here are the questions:

1.) Are we really getting the full benefits of combining the 2 motors into one side because we are using the drill motor transmission supplied by the KOP. To me, it just doesnt make sence. As soon as the drill motor's transmission's clutch starts to click, the drill motors are not supplying any force any torque and its just like running the CIMs by themselves.

2.) Is it really hazardous to the drill motors to put the transmission in direct drive. We have burnt many a drill motor before but if the CIMs are helping it out, should this really be a concern?

3.) We are currently running all the motors through 30amp breakers because we did not have another 40 fuse box lying around. Could this cause problems?

4.) Is it possible to burn out the CIMs, if stall amperage is 50amp and its running through 30amp fuses.

Re: A few gearbox questions
 

The drill-transmission clutches can be set to the fully-locked setting, its that symbol past the highest number. If you geared it correctly and the motors are running in the same direction, you will benefit from increased power.

No, many teams have done it, just make sure you properly matched the speeds between motors as well as other minor things, like gear alignment and such. We've never really burnt a drill motor, we have melted the plastic brush housings and solder off of the leads. But usually a fan blowing over the drill fixes everything.

Not really, not until your motors start to stall and reach over 30 amps which is when the breakers will start cutting out. Nothing bad is going to happen to the motors.

Nope, that's what's the breakers are for, to protect your motors and electronics. They'll trip before the CIM reaches the 50amp stall current. Now, if you bypassed the entire thing and ran the CIM at stall for a long time, sure you'll burn it out, all motors will if you did.

Re: A few gearbox questions
 

Why leave the clutch on the motor. This whitepaper http://www.chiefdelphi.com/forums/pa...le&paperid=150
explains very nicley how to remove the clutch and housing, and lock the clutch plate from rotating. The drill motors and planetaries don't fit properly in the plastic kit mounts until you romove the clutch housing anyway. Plus this makes it lighter. With the clutch removed this is just a normal planetary gear set. So there is now reason your setup won't work.

Re: A few gearbox questions
 

On this point you are incorrect. The provided mounts were designed for the drill motor and clutch assembly and they fit quite well when assembled properly. Perhaps you made the above conclusion when you may have unknowingly assembled the motor/gearbox/clutch into the mount improperly. Many teams including top-level contenders such as 258 and 60 have used the drill motors as they come in the mounts they come with.

Also, I believe that whitepaper only shows how to take the gearbox apart and makes recommendations about improving it. It does not show how to do the procedure you outlined about removing the clutch and running without it.


Now back on topic...
If you are having a problem with the clutch slipping, the answer might not be to remove the clutch. The motor is under a lot of load from somewhere and that load is being "slipped" at the clutch. If you remove the clutch the load will be transferred back through the geartrain and the motor. You should remove this excessive load making the clutches slip, not remove the clutches themselves.

What you are trying to do with this drivetrain seems exactly like the Team 716 2003 single speed gearbox design posted in the whitepapers on this site. Teams 696 and 980 also used this design with much sucess in the 2004 season. I would recommend gearing it for a maximum free speed of 7-11 feet per second depending on what kind of torque you want.

Re: A few gearbox questions
 

Actually, if you remove the clutch, they WON'T work right with the standard drill mounts. There's two little metal tabs in the front of the transmission, on the face of the casing. They'll fall out if you dont cover the face of the transmission, and the drill motor doesn't seem to run as well.

Re: A few gearbox questions
 

Always lock the clutches, they will burn out if left unlocked and will become useless. Also, double check all the transmission bearings, gears, ect for any binding, and make sure everything is well lubricated. I like to use White Lithium grease because it's madee for metal-metal contact and won't drip on the playing field.

Re: A few gearbox questions
 

Actually, once you braze the clutch ring to the ratchet, you don't need those metal tabs, and you just take them out since they are just part of the clutch. It fits perfectly in the mounts then, and there is absolutely no worries about it slipping.

Re: A few gearbox questions
 

After replacing somewhere between 4 or 5 drill gearboxes last year, I decided to come up with a way to remove the clutch (only to find out that the white papers already had a awesome paper on doing just that). We had a gearbox that did the same thing as yours, combine the drill, and cim motor together, if I remember correctly, the output rpm's where around 222 (or so). I was in charge or building the gearboxes last year, and now this year again, I am building a prototype of a 4 speed automatic(and a variable high/low 8 speed automatic) transmission for testing before the season. After last years season was over, I must of designed 6 different gearboxes utilizing just the drill motor, and cim, no drill gearbox (just had to find .7 mod gears), but After visiting Clarkson - and crashing in JVN's room (thanks for the couch man), and many hours of Mario cart, did he reveal to me, pic-design, and there awesome selection of .7 mod gears. Now I have a notebook filled with designs, ideas, concept drawings, but my team wants to try a 4 sped automatic that another team designed, but then I added a final stage, one with a 1:1 ratio, and one with a 3:1 ratio for the ultimate pushing power. The only control the driver has is high, or low, the transmission will shift between the 4 gears as needed to optimize motor efficiency. So, I'm pretty excited about this design. But, we still do not know what new motor(s) will be available this year, along with what challenges we will be faced with this year.

Re: A few gearbox questions
 

Ahh the infamous couch of JVN and Eric O'Brien. If only you knew how many gearboxes have been designed on those very cushions.
We specialize in comfort and inspiration... and Mariokart, we're pretty good at that too.

It's not like PIC was a big secret. Maybe you should have taken the time to search Chief! Ahh well, better late than never ;).

Remember folks -- Design is iterative.
I've been through 3-4 different transmission designs just this fall!
(Had a lot of trouble finding one that could live up to the competition...)

Keep trying different things, until you find something that you're happy with.
John

PS - "In every project there comes a time to shoot the engineer and just build the thing."

Re: A few gearbox questions
 

I also have redesigned our gearbox several times this Fall. Even designed and built a dual motor Dewalt gearbox. Not that we are planning on using it this year but now we have a proven design that can be pulled and built. (I was going to say 'on the shelf' but then I realized what a mess that could start :D )

Eveyone should take John's quote to heart. I always advocate building and testing. The Dewalt gave us some trouble early, this would have been a disaster during build season, but now it is working fine.

Re: A few gearbox questions
 

we have a similar rig as u and our chips never overheated. However our drill motors did crap out on us a few times.

Re: A few gearbox questions
 

Did you find one? ;)

Re: A few gearbox questions
 

Actually...
I did!

Of course, even though I like my new design...
The real benefit of AndyMark is: no manufacturing time. It frees up resources to do other things (like reverse engineer it with some HS kids!)

So... we STILL might buy AM Shifters, even though we have a comparable design.

John

Re: A few gearbox questions
 

i was just wondering if anybody out there could point me to a website or tutorial that breaks down how to design a gearbox for beginners. like i dont know what information i need and how to pick gear ratios and all the basic things which i need to understand to design a gearbox which combines the chip motor and the drill motor with a hi-low transmission, and thats what i have been put in charge of this year. any help would be appreciated

Re: A few gearbox questions
 

The White Papers located on this site can get you started, here's a good one.
Also the Waterloo Regional Website's Technical Resource Page has information about drivetrains and related.
And not to forget, the FIRST Robotics main website has an archive of the 2004 FRC Workshops.

Hopefully these can get you started out, any additional questions feel free to ask on CD :)