Image Discuss: Plan View of 27's Transmissions

[CD47-Bot]

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[KyleGreen]

whoa.. you probably get some serious power out of those, don't you?

[sanddrag]

They probably do have a lot of power with that setup. Too bad those little blue 16 gauge wires are going to melt. We've got 8 gauge finely stranded superflex wire on our 4 drive motors.

Also, isn't shifting with a four motor drive kind of overkill??? Nah

What kind of voltage drop do you get running in high gear?

[PMGRACER]

Thanks for the tip. In the few hours we ran the 'Bot before we shipped, the wires seemed fine. The drills seemed to get a little warm, but nothing to bad .

[Gadget470]

I'm willing to bet your shifter shifts a planetary gearset in the middle stage

[PMGRACER]

Good guess. Planetary gear sets may have more resistance than spur gearing, but you are able to have higher changes in ratio in a smaller space. There are some really cool trannies out this year. Many different approaches. I can't wait to see them all at the regionals and Houston.

I'm glad we finally went to pnuematics to shift. This new setup shifts quickly, and reliably. We never did have to much luck with servo-actuation last year.

The trans uses a slider ring similar in design to the Bosch ring, but made out of mild steel. I had the Chrysler machine shop EDM the teeth into the center, then I cut a 1.625 hex into the face which engages on the face of the housing. We designed the shift fork to use 4-48 thread allen heads turned down on the ends to .08 which ride in a .084 groove in the shift ring. The pins are spaced 120 degrees apart and suspend the shift ring on centerline. We are using the 1/2" stoke Bimba cylinders for shift actuation. One other item we had to address was the radial load the drivetrain applied to the output. So we are now using .500 Timken Tappered roller bearings to keep the shaft from wearing out the gearset.
PMGRACER

[Mark Garver]

What does one of those gearboxes weigh? My guess would be some where between 12 and 15 pounds? Also do you have output shalfs in different directions or do you have to change the speed of the drill motors (the difference of running one forward and one backwards) in programming?

Well if I don't get answers back I guess I will have to wait till competition. As Dr. joe stated in an earlier post, great job this year.

[Bduggan04]

Originally posted by Mark G
What does one of those gearboxes weigh? My guess would be some where between 12 and 15 pounds? Also do you have output shalfs in different directions or do you have to change the speed of the drill motors (the difference of running one forward and one backwards) in programming?

Well if I don't get answers back I guess I will have to wait till competition. As Dr. joe stated in an earlier post, great job this year.

The two gearboxes together only weigh 13.9 lbs. There are two different output shafts so that we don't have to change the program in any way. The motors are oriented the same way for both sides.

[f22flyboy]

Originally posted by PMGRACER


I had the Chrysler machine shop EDM the teeth into the center, then I cut a 1.625 hex into the face which engages on the face of the housing. We designed the shift fork to use 4-48 thread allen heads turned down on the ends to .08 which ride in a .084 groove in the shift ring. The pins are spaced 120 degrees apart and suspend the shift ring on centerline. We are using the 1/2" stoke Bimba cylinders for shift actuation. One other item we had to address was the radial load the drivetrain applied to the output. So we are now using .500 Timken Tappered roller bearings to keep the shaft from wearing out the gearset.
PMGRACER

now if only Chrysler would put that kind of engineering into their cars

[sevisehda]

It looks nice and compact, with the benefit of the motors working in unison it looks like one of the best tranny's I've seen so far this year.

Did you buy the planetary system as a whole, salvage parts from the bosch drills, or build it from parts?

[PMGRACER]

Hey thanks for the compliments guys! We did work hard on the system we have now. This is the 3rd generation of this design. We have reverse engineered the Bosch trans thouroughly. We feel it is an efficient design. Meaning we get the benefit of a high differential of ratio in a small space. The Bosch design seems to be quite robust. I'm sure the engineers at bosch never thought their simple design could take so much abuse!

We do use some of the gears from a stock Bosch trans, but everything else is scratch built. The stock output shaft used dowel pins for the final stage gears, we replaced them with .125 shoulder bolts. Obviously we scrapped the clutch. The next gen will use Timken Tappered roller bearings to deal with some of the radial loading we can't get rid of. The slider ring, as stated earlier, is a custom piece. Also gone is the plastic housing, with the wimpy teeth in the front which strip just by breathing wrong.

The Drill and Atwood motors are mounted in the same orientation to eliminate the torque steer you get when the motors run in oppisite directions. We just rotate the output shaft 180 degrees. If you look closely at the back of the units, you'll notice the output shaft sticks out. I call it the PTO shaft, becase there is a .187 female hex EDM burned through the shaft, so we could use the output to power other systems.

Shifting is very smooth. As I said earlier, the slider ring is suspended between 3 pins which kept it square to the shaft. The face looks like a 1 5/8" nut and the bore of the housing has a 1.652" "socket" milled into it. You need the .025 clearance for it to shift smoothly. However, there is no lash. Once engagerd there is no rattling noise.

BDuggan and his brother IDuggan can have the units out of the robot and torn down in about 10 minutes. With the Hex coupling, you don't have to tear apart the drivetrain to pull the trans. Once out of the 'Bot, remove 6 Allen bolts and the planetary section separtates from the power section.
PMGRACER

[austind27]

Originally posted by f22flyboy
now if only Chrysler would put that kind of engineering into their cars

Chrysler does put that kind of engineering into their cars, it's called a Mercedes Benz.