What motors power your drivetrain?
 

I deleted my original thread because I realized a flaw in my thinking. (Don't worry, no one replied. Unless.... j/k)

As a result of some heated discussions in my team, I though I'd ask the collective FIRSTers.

Q: What motors do you plan to power your drivetrain? Is it a hybrid system with more than one type of motors?

Before you respond, consider the following:
1. Power
2. Current draw
3. Ease of machining
4. and anything else I skipped

If you also give me some sort of reasons behind your thinking, it would help me out very much. Who knows, may be I'll even quote you at my next meeting! I'll be sure to let you know if I use your quotes.

C'mon. What are you waiting for. Go to the polls!

WE may be reconsidering the chalupas due to their heat problems...
If you don't know what I am talking about, run them for about 15 minutes no load and then burn your hand checking to see if it is running warm.

how exactly would you use the Atwood motors AND the fisherprice?

There's a couple of ways.

Gear the chalupas and FP motors to the same free speed RPM. Mate the 2 motors to a gearbox (that you've custom designed for this purpose) and then drive the wheels with the gearbox.

Gear the chalupas and FP motors to the same free speed RPM. Use 1 motor to drive each wheel (4 wheel drive).

But why use two motors to drive a gearbox when one would be sufficient?

What about those teams with more then one drive trains?

More than one drive train? As in a halftrack type device? Wheels and treads? Or something more exotic? Care to elaborate?

8 wheel drive train using 2 drill motors. thats alot of chain that we used and we use even more when we go to readjust / install a new motor since the motor never sits the same way twice :D

8 wheel drive
 

8 wheel drive?! i dont think so. true 8 wheel drive means you have one motor for each wheel not 2 spread across all 8. at least thats what ive been told

2 motors power our 8 wheels


left side 4 wheels 1 motor and about 3 dif sproket sizes
right side 4 wheels 1 motor and about 3 dif sproket sizes


and lots of steel chain.

Re: 8 wheel drive
 

Not necessarily. Would you say a 4-wheel drive robot is not "true 4-wheel drive" without independent motors for each wheel? Whether a robot is 2, 4, 6, or 8 wheel drive depends not on the number of motors, but the number of powered wheels.

TOBOR 5 uses the chalupa motors with a 30:1 gear ratio

Two Drills for the past 3 years.

Our 'bots have often focused on speed rather then beefy drive trains. The extra pushing power of a 4 motor drive would have been nice, but didn't really fit into our game plan. Two drills are the most bang for the buck (the buck being a number of things... weight, current, time). While being powerful, their transmission allows some flexibilty going into the match. With a third drill motor in the kit for a replacement, they make the perfect drive motor for most all FIRST 'bots. If you don't use the drills on your drive, I'd be very surprised.

So while having the Atwoods or FP motors running with the drills would have been very nice (and were planned for '02), those motors are either more usefull elsewere or were to heavy.

Chances are 95 will stick with the drills. What can I say? We have this thing about really heavy (complicated) ball pick up devices. At least we're good at something right?

-Andy

We've used 2 drills in 2001. In 2002 we tried to use 2 drills and 2 chias but we had some gear stripping problems so we ditched the Chias. In 2003, we will definitely have 2 drills and 2 Chias.:)

Note: The full name is Chiaphua.:)

Atwood and Drill, or at least it's what we did last year. This year we are thinking...
~Mr. Ivey

Hey wetzel, alot of teams do this, they have a primary drive system, and then a secondary (powerful) one, Like CHAOS- 131, they have a tanks system and wheeled, they just engage at different times



look at 157, 237, and 131 for examples


Badjokeguy

BOSCH & FP!!
 

We found the Drill and FP to well compliment each other (important on a swerve drivetrain) on our 4 independent drive modules, especially with the more powerful FP motors this year. We also kept the modules identical left to right so all the motors spun the same direction so that the drill timing was no longer an issue. We used the Chips for the boom that needed alot of power since it wasn't counterbalanced, also they are heavy!! Definately the Drills on the drive they are a perfect fit for that.

Re: BOSCH & FP!!
 

The drill motor has timing. Your kidding. We've been running it in reverse on one side this whole time. Can you elaborate a little more on this.

Drill motors are usually timed for better performance in the forward direction (for drill bits and inserting screws) so it has a little better performance in the forward direction. You could (depending on your robot design) see a slight curve in the driving of your robot because of this. Search the forum for Drill Motor timing, I know we have had discussions on it in the past and ways to correct it.

Matt

Okay thanks. I know runing motors with "negative timing" can lead to excessive heat, arcing, current draw, and wear. So, I'll go look fo those threads.

true 4 wheel
 

For the past 2 years our team has created independantly powered 4 wheel drive systems. In 2001 we used 2 drills and 2 fisher price, but we found that the gearboxes (plastic) kept burning teeth (although they could still run in some instances). In 2002 we used the new chipuas with the same drill syatem we had the year before. It took a while to match the chips to our drills but we got it and it worked fairly well. We never had any overheating problems because we hardly ever moved (lol stradegy always wins). We did notice however that the draw from the drills and chipuas was rather taxing on our batery. Because of this we opted for no pneumatics.

To date we have never worked on our 2002 bots drive train, and only a few post competition events have we had to change our our 2001 bot's gearboxes and one fisher price we burned out (the sleeve on the motor came back and covered the eexaust holes in the back and well lets just say the magic smoke came out).

the drill motors have 15% more power and speed in the forward dirrection, than they do in the reverse dirrection, last year (2002) we put both in the same dirrection, so we were able to go 15% faster in forward (the dirrection our tranny was designed to go) than we did in reverse. we also used the atwood in there to give it plenty of power

Re: BOSCH & FP!!
 

Hey- I've heard about swerve drivetrains and last year I saw Chief Delphi's bot- man did it ever drive sweet.. I've never heard any logic explaining how it works- could someone explain it to me or link me to a page.. Thanks..

Re: Re: BOSCH & FP!!
 

In a 'swerve' drivetrain each of the 4 wheels has the ability to pivot in the vertical axis. So far, Chief delphi (6 I think) holds the record for the most complex setups including the fully independent 4 wheels steer setup in 2001 using traingle tank treads where each of the 4 could pivot independently of each other. For our first attempt at 'swerve' last year we linked all four drive modules to each other so they pivoted together. Then you place a pot on one of them to pick up position. We converted the rectangular coordinates from the joystick to polar to get a vector that we wanted the wheels to point to. When it is all said and done a 4 wheel steer robot is extremely manuverable and can get out of very tight spaces. We took it a step further and made the drive modules easily replaceable or 'modular' an approach everyone should look into doing after we noticed the modules on wildstang 2001 and how they had spares ready to go in just minutes. For more info, I posted our gearboxes in the whitepapers and the full code for the steering on the Codex and various places on this site under the name pegasus.zip

Happy swerving, many teams can help you on this but each of us has a few secrets up our sleves :D

Re: Re: Re: BOSCH & FP!!
 

Thanks for explaining- unforunately I don't have any CAD programs at home so I can't access that .dwg file you had on the white papers.. Anyone have a pic I could look at?

Don't worry- I'm not part of the pit crew here and I'm also not spying for anyone.. Just a curious firstaholic here..



P.S.- That's a nice H2 you're in... sighs...

A good program for any of you at home for free is VoloView from Autodesk it lets you open and zoom in DWG files without having to buy a CAD package. YOu can not make changes but you can view them.

4 Atwoods!!
 

For 2002, we successfully used 1 Boesch and 1 Atwood geared to a common output. We geared the motors so that each were operating at 75% output. We never had a problem over heating the drills or the Atwoods. Accelleration was over 10 ft/sec when in high gear, and in low, gave us plenty of grunt to push or pull a few of the big dawgs around the block without overloading the motors and tripping the circut breaker. Depending on what tasks we will need to do in 2003, we will be able to tweak the gearing for higher torque or accellaration over 18 ft/sec. Of course I think it would be cool to have the bot do a big wheelstand as it launches out of the hole and throw out the laundry on the big end...but this is not drag racing....?:D

Just a thought ---- Did the winners of last year's Nationals have complicated 2 or 3 motor drives, or did they have simpler, more robust 1 motor drives geared appropriately, and driven well?

The 255 robot (2000 national champ) had 4 motors on the entire robot. FP for the 2 wheel drive, a van door to raise the basket/lift the robot, and a seat motor to open and close the baske door. Strategy, driver skill, reliability usually beat complex drive systems.

So stop bad mouthing the FPs - they will work fine for the Rookies.

I liked the FP's especially last years, they had great power and better cooling. We used them in the drivetrain also.

I don't know about the winners of Nationals, but I know my team did very well with a single-motor drive. We used one Chiaphua motor with a two-speed gearbox and never had any problems. We were one of the fastest and one of the most powerful robots around- all from a one-motor drive. It was all in the gearing. It goes to show, though, just like 255's did, that you don't have to be complex to be successful.

2 years ago (Bridge Balance year) 'da Bears did that on accident.

We swung our arm back and started goign forward to the balanced ramp. (Was balanced because it hit another team's bot on it's way down. Anyways, in a wheelie on our tank drive we were also bringing up the arm to vertical.

The sizes were justright so as we went forward (still in wheelie) we got on the bridge, arm finished it's forward motion (thus throwing center of gravity forward) and slammed down the bridge for us.


We have a video I took of this match somewhere..

How did it steer with only one motor?

It was one motor per side. I guess I left that part out. It would be a little hard to steer with one motor.

After last year's competition we spent part of the summer developing a new drive transmission design for our robot ED. The drive features a 1:4 ratio between low and high gears, 250rpm and 1000rpm peak power output speeds, up to 65 ft-lbs of torqe, uses the Bosch and Chiaphua motors found in the 2002 kit of parts, and an 8-millisecond response time to shift gears. The prinicpal feature is that the design can be constructed with hand tools, a lathe, and a mill. No CNC, wire EDM, castings, or carbon-carbon componsite construction capabilities are required (hopefully putting it within the reach of most teams)! We play-tested Version 1.0 of the drive system at the Maryland State Fair competition at the end of the summer, and refined Version 2.0 during the fall.

Rather than keep it as a secret, we are making the design available to any teams that want it. It is posted in the White Papers Section. Download it, build it, improve on it, or just look at the pretty pictures - it's all up to you. All we ask is that you let us know about any feedback, and if you do improve on the design, please post your improvements so the entire FIRST community may benefit and improve their capabilities. In the mean time, we are off thinking about Version 3.0 for the 2003 season...

-dave

As Big Mike siid- this past season we used the Chiaphuas (chalupas- atwoods- chihuahuas- whatever) to drive our wheels.

The biggest problems was getting the gears (of unusual configuration) to work with the normal gear types we had available.

The solution was to machine out a reg spec gear such that the bore of the arbor was minutely smaller than the external diameter of the motor arbor. Then we froze the motors and heated the gear such that the expansion/contraction of the two allowed for the shaft to snugly fit into the gear bore when pressed on. As the two slowly came back to room temperature thermal expansion and contraction formed a snug fit which never failed us.

Of course the gears were built into a configuration which came to about 32/1 if I recall and in the wheel housing the load is shifted to sprockets which actually drive the wheels. That way, in the event of something fouling the drive train, the weakest point is the chain and that is easily repaired.

We also designed our machine to grab two goals on the run. Our two extrudable hooks were preset by software to come out as we fly towards the gap between two goals. They sit on tracks in the chassis and are held forward by a shock absorber. So as the robot hits the goals and grabs them, the impact is shifted to the shocks and the chassis stays together. The momentum of the whole system now is moving forward and inertia slams the 290 lb system into whatever is in the way. Inertia can be a good thing!!

Sorry if this is long- I really like that machine!!

WC