Let me put my opinion like this:
When you take the drill motor peices out of the box and they fall apart all over the floor, it doesn't help raise your opinion on them.
I have always disliked the drills (for drive)
They just don't cut it when it comes to cometition. They break easily, they overheat easily...
Just hookup those CIM's and Drive Baby!

1. The drill motor has only one plastic part this year, the shifting gear. every other gear is metal.

2. The Atwoods will never be easier to mount than the drills.

[edit] To those who say the drills dont hack it: not true. The drill motor will take a thrashing and keep on working. If you have a good design, they wont break easily. From Florida to Cal Games in September last year, we didnt need to replace motors once, and we totally thrashed them. We had a very very powerful bot that had a fast top speed also, and we never overheated our motors.

the point: If ya do it right, the drills own. Only one thing owns more than drills: drills and chippys.[edit]

Cory

i couldn't agree more with that statement. even with the 1/2 drills this year, chippys are still more powerful, teams proved last year that pure chippy drive is strong enough if done correctly, we hope to prove that this year

We use the Chips, Drills, and Fishers this year. The Chips drive a 52 tooth gear directly and then the Fishers drive the 52 tooth with the stock 19 tooth and a new 15 tooth gear was pressed on the drill motor which also drives the 52 tooth. This combination allows the motors to match-up pretty close. A 32 tooth gear is mounted to the same shaft as the 52 tooth giving the first stage of our double reduction 9:1 final output. This drives a two speed 5:1 reduction planetary gear box that is pneumatically shifted. Top speed is about 18 feet per second.

We used Drill and Chip combination. We designed a very compact motor mount that mounted the two side by side, then calculated the proper gearing ratio (roughly 3.75:1) and build a small gear train that would match the free rotation RPM speed of the motors, and took that through the drill motor gearbox. We made a bet that there is a factor of safety of 2 in the drill gearbox, and from everything that I can see, this bet was a correct one.

The drill's reduction gearbox is locked into a single gear by means of custom fabricated aluminum rings. A second aluminum ring (which was a nightmare to fabricate) locked the clutch ring to the transmission body. It was a mating part designed to light press-fit the clutch body into, the entire assembly then slides backwards onto the plastic body to engage the two side tabs. To really secure things, we casted about half pound of JB-weld around the entire mess, then disassembled the transmission, degreased all the gears, and relubricated with teflon based lubricant (Triflow). It sounds like a brunch of screaming banshees when it runs, but the transmission was also running a lot faster.

We had some problems with our drivetrain with the amount of torque it generates. First, during our design, we under-estimated the amount of side forces that the helical gears would generate, given the amount of power we transmitted through the axle. During sudden accelerations, the bushings that held the gears in place would actually pop off bearings that had been press-fitted with Loctite RED. This was resolved with the addition of fender washers that took the load off the bearings and onto the side gear plates.

The second failure point was the reverse-engineered output shaft. We did reverse engineer the output shaft, but for testing we fitted a shaft into the little tab with a 10 ton press fit. After about an hour of drive time, the press fit sheared. We then tried tig-welding the tabs on, but no luck. A single piece axle design will fix the problem permanently.

This is what I've learned on bulding this year's drive train. This is the first year where our team (824, second year rookie ;-) ) attempted to build a custom transmission, so there were technical hurdles that we had to overcome:

* Understand press fits. The tolerances that you *have* to hold are absolutely CRUCIAL. +/- 0.0005" could mean the difference between a light press fit, a "deform the heck out of the bushing" press fit, a "My goodness, look the gear just split in half" press fit and a "Um, I can pop this out with my fingers" press fit.

* Understand the limits of methyl acryate binders such as loctite. Murphy's law of superglue applies. (It will only stick to things that you don't want it to stick to).

* Gear alignment is *CRITICAL*. Our team made extensive use of a half-pound dead blow hammer to lightly tap things into proper alignment (it *really* is a fine adjustment tool). Machining the tolerances required for a clean running drivetrain is not easy, even with master machinists, you *should* allow for some sort of adjustability for all your alignment. The efficiency that we got from this year's drive train was awesome. We drove for 20, 30 minutes on one battery charge - last year we were lucky if we got 15 minutes between battery switches.

Hope this helps. See you all on the fields,

-=- Terence

2003 Team 824 Drivetrain Team Leader

Ok everyone, I've stated my opinion before, but let me post some info to back it up now.
After competing at VCU here were several things we noticed:
1) We had no trouble pushing around robots w/ drill drive system
(We used CIMS, btw)
2) Several team's drill drives were completely useless by the second day of competition. There were several things that went wrong.
3) At the end of the Day, FIRST gave away all the parts from the "Broken Parts" booth. There were at least over 5 drill motors in the box by the time I got there. I couldn't tell why there were so many drills...
After further inspecting them, I found that each of the conductors that carry voltage to the main shaft of the motor are secured on BY PLASTIC PEICES. These pieces simply took a hit and broke off, rendering the entire motor useless.
In my opinion, the drills are just too much to worry about.
Our Drive (4wd CIM, Chain,10:1 Gear Ratio, 40 amps,8" skid-steer tires) this year was highly successful, and didn't give much trouble. The hardest part was taking a 5/8" shaft and drilling an 8 mm hole to fit onto the CIMs. Then, the sprocket went on the small shaft piece. The only good thing that came from the drill motor drive system this year was the fact that we used some of the mounts to lock our jack-shafts onto our Chassis.

Dual motor drive with 2 speed slush box
 

After one regional event complete and another close by, our gear box has worked very dependably. We are using the Atwood/Bosch combo coupled to an old style design Bosch planetary trans. The Atwood and the Bosch are geared to keep each at the optimum torque/ hpwer. We do not have any problems over heating either motor. If you are having trouble with heat, check yuor drivetrain resistance. Maybe you have a jumped chain or frozen bearing or some other heavy parastatic loss.

We have a couple JPEGS in the Gallery of the current tranny config.

Some other facts; Drag race style air shifting, Lenco style planetary section, modular shaft design for easy removal from drive train, Students can remove trans from chasis and tear down the planetary section in about 5 mins! Which we did at the Buckeye before the Alliance Selection began. Word of advice to all, make your systems easy to service and to install and remove from the chasis. Easy maintainence will go along way.:cool: