i think you misunderstood. I didn’t mean putting a drill and a atwood together on a single drive train, i meant having each seperate wheel controlled by a seperate (singular) motor.
That’s us, except we went with the Fisher Price because they were smaller and coupled better (easier i guess) with the drills. We’re building our own transmissions for the first time and lemme tell you, it’s a BLAST!! Hopefully it’ll work out…we’ll see at San Jose!
lauren
*Originally posted by GregT *
**Its a programming nightmare either way, you just don’t know how bad it is when they are coupledAnd your efficiency does drop dramatically when coupling motors- they fight eachother - but who cares in a 2 min match?
Greg **
They don’t fight each other if you gear them to the same rpm. The efficiency doesn’t drop that much as long as you gear for the “sweet spot” in each of the motor curves.
As for programming goes, it’s no different. You could run both speed controllers off of one pwm and the programming is no different than it is for one motor.
*Originally posted by BBFIRSTCHICK *
**we have 2 on each side, and used gear ratios **
Same here.
(watch for pics to be uploaded soon)
*Originally posted by Harrison *
**Same here.(watch for pics to be uploaded soon) **
Harrison,
What do you use to switch from low to high gear…servos or pneumatics…or something else??
From the specs I saved, the Chiapua motors had just slightly less power (less than 10% differential) and a lot more torque. At stall, the Chiapua had 315 oz-in of torque. The 2002 drill motor was 650. mN-m at stall, which is about 92 oz-in. I’d expect 3 times the torque with all the copper and magnets in that big motor!
And don’t be fooled by the torque specs with the drill gearbox…I’m talking the motor only.
*Originally posted by Dick Linn *
**
And don’t be fooled by the torque specs with the drill gearbox…I’m talking the motor only. **
If you gear two different motors to have the same output speed, the one with more power will also have more torque. This does not necessarily mean the drill motor is a better choice because with both motors geared to the same speed the Chalupa motor will probably have a lower effective mass and accelerate faster.
For those of you using both the drill motors and the atwoods, I am wondering how you are planning on programming the motors. I ran into a few problems, we want to beable to use drill motors on the front and atwoods on the back, and basically moniter the wheels so one doesnt spin faster than the other. Basically we made a speed-o-meter and if one is spinning faster than the other, they correct themselves. Heres the problem, we wanted to use the pulsin command to moniter our hall effect senors, but as it turns out, pulsin isnt supported. Sigh… what to do. Any one have suggestions? am i going about this the wrong way? please respond
thanks
J.D.
*Originally posted by PyroPhin *
**you would have to team them… would be a programinig nightmare to get two different motors to go the same speed on each side of the bot~Pyro **
Actually, it isnt that hard. Look at 60. Relatively simple drive, worked great with independently powered wheels.
Cory
our team is using just the two drill motors and we can get across the field in about 6 seconds but we still have a ton of power
I like this year’s drills much more than previous years, they do feel almost as smooth as the atwoods (for driving) and are very backdrivable as well. Given good traction, they can also be very very pushy/powerful, and are extremely responsive (from what i’ve seen driving our chasis around).
its all about the gearing, this year were using 2 chips(atwood) and drills. We having been using this combo from last year and they have worked extremely well if geared correctly. This year we had to redesign our gear box because they chaged the motors and our gearing is simple and comes out to be 11:1 from the chips to the drills. we havent really given it a shot on the the carpet yet. Thouhg its working well.
we are using the 2 drills and it takes us 5 secs. at 1/3 speed to get up the ramp, at full we will fly over it. Our robot also puts up a big fight in a pullin contest with a 200 lbs person on our team. Anyone jus locking into either low or high?
Jon
I always liked the Atwoods, with proper gearing they can work wonders. The only reason I dont like the drills is that there tranny is mostly plastic. I dunno I just like simple parts that do simple tasks and work time after time. And the atwoods are very easy to mount, and they can take a huge beating and still work.
The Chiaphua is more powerful than the drill.
We accidently wired our combiner backwards and as soon as you put any substantial voltage to it, the chip would over power the drill. The breaker would trip every 1/2 second causing the robot to run in spurts…
Moral of the story: Never trust your sparkE’s… I mean, the Chip is more powerful…
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!
*Originally posted by Thunder360 *
**The only reason I dont like the drills is that there tranny is mostly plastic. I dunno I just like simple parts that do simple tasks and work time after time. And the atwoods are very easy to mount, and they can take a huge beating and still work. **
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The drill motor has only one plastic part this year, the shifting gear. every other gear is metal.
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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
*Originally posted by JVN *
**Moral of the story: Never trust your sparkE’s… I mean, the Chip is more powerful… **
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:
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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.
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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).
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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