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Madison 21-01-2008 18:57

pic: FRC488 Completed Drive Train
 

sdcantrell56 21-01-2008 18:57

Re: pic: FRC488 Completed Drive Train
 
So do you not have a way to tension the chains? Other then that it is so beautiful...so simple. O and aren't you a little worried about the chain wrap around the output sprocket?

Madison 21-01-2008 18:58

Re: pic: FRC488 Completed Drive Train
 
Quote:

Originally Posted by sdcantrell56 (Post 683059)
So do you not have a way to tension the chains? Other then that it is so beautiful...so simple.

There's a bolt at each of the four corners that pulls on the omni wheels and tensions the chain.

sdcantrell56 21-01-2008 18:59

Re: pic: FRC488 Completed Drive Train
 
Awesome! I was assuming you had some tensioning device

waialua359 21-01-2008 19:54

Re: pic: FRC488 Completed Drive Train
 
This looks very similar to what our drivetrain looks like except our electronics are in various places near its functions and using the andymark supershifters.
Nice work.

Matt H. 21-01-2008 20:03

Re: pic: FRC488 Completed Drive Train
 
How does this drive train incorporate this years mandatory bumpers?

billbo911 21-01-2008 20:06

Re: pic: FRC488 Completed Drive Train
 
Very nicely executed!
I was hoping to see the frame and wheel mounts you had up on CD earlier. That design really intrigued me. Either way, this looks really nice.

I must comment on the amount of chain wrap on the drive sprocket. With only this picture to judge by, I would say it looks a little suspect. I would be concerned about slippage under heavy load. If your testing proves otherwise, then you did a great job. Thanks for sharing.

Alex Cormier 21-01-2008 20:06

Re: pic: FRC488 Completed Drive Train
 
wow... i am amazed every year with your bases. Very elegant and simple yet effective.

Madison 21-01-2008 20:12

Re: pic: FRC488 Completed Drive Train
 
Quote:

Originally Posted by Matt H. (Post 683129)
How does this drive train incorporate this years mandatory bumpers?

We're planning on bumpers sitting between 3.5" and 8.5" from the floor -- and as such they land well above everything shown here except the wheels and motors. The bumpers, as a result, will be mounted to the super structure and spaced out beyond the wheels.

Quote:

Originally Posted by billbo911 (Post 683131)
Very nicely executed!
I was hoping to see the frame and wheel mounts you had up on CD earlier. That design really intrigued me. Either way, this looks really nice.

I must comment on the amount of chain wrap on the drive sprocket. With only this picture to judge by, I would say it looks a little suspect. I would be concerned about slippage under heavy load. If your testing proves otherwise, then you did a great job. Thanks for sharing.

We'll be adding an additional idler on the battery side of the motors to get a bit more chain wrap. Chain skips under high load using the default code, but not with our modified code that dampens the response during rapid input changes. Still, it's better to be safe than sorry, and the new idlers will go in as soon as we finish work mounting the structure.

Ben Piecuch 25-01-2008 14:26

Re: pic: FRC488 Completed Drive Train
 
Madison,

I like the simplicity and layout of your drivetrain. My question is, why are the front chains cantilevered so far inside? It seems to me that you could flip the gears 180 deg and move the chain out towards the rail, creating a slightly tighter package. Both of our #25 chain runs fit within an inch of the rails. Yours look to be hanging out much further than that. Overall, a great looking and performing drivetrain. Thanks,

Bengineer

Madison 25-01-2008 14:33

Re: pic: FRC488 Completed Drive Train
 
Quote:

Originally Posted by Ben Piecuch (Post 685718)
Madison,

I like the simplicity and layout of your drivetrain. My question is, why are the front chains cantilevered so far inside? It seems to me that you could flip the gears 180 deg and move the chain out towards the rail, creating a slightly tighter package. Both of our #25 chain runs fit within an inch of the rails. Yours look to be hanging out much further than that. Overall, a great looking and performing drivetrain. Thanks,

Bengineer

The back chains run from the Dewalt to 24 tooth sprockets on each wheel. The front chains are running around 18 tooth sprockets for no reason in particular.

On the middle axle, the hub diameter on the 24 tooth sprocket approaches the outer diameter of the 18 tooth sprockets -- so we had to turn them around to allow clearance for the chain. We could've ordered more 24 tooth sprockets, but I have about two dozen extra 18 tooth sprockets lying around from past projects, so we used those for convenience. As is typical of our robots, there's really nothing else down there, so they're not in the way of anything -- but they're also really easy to change if it becomes necessary.

AdamHeard 25-01-2008 14:41

Re: pic: FRC488 Completed Drive Train
 
What are the speeds of it? And the math/reasoning for one small CIM on each side (not criticizing, I trust you M, just curious)

Also, wouldn't swapping out the sprockets save you a few ounces of weight because of the shorter shafts it allows?

Madison 25-01-2008 14:55

Re: pic: FRC488 Completed Drive Train
 
Quote:

Originally Posted by AdamHeard (Post 685735)
What are the speeds of it? And the math/reasoning for one small CIM on each side (not criticizing, I trust you M, just curious)

Also, wouldn't swapping out the sprockets save you a few ounces of weight because of the shorter shafts it allows?

Third gear (6:1) is somewhere above 12 ft/s without the rest of the machine sitting on top of it. We added 26 lbs. worth of stuff to the top this week and it hasn't slowed appreciably, but I'm sure it will as we keep piling things on. Driving in this gear is considerably more like driving a race car than a robot. Cornering effectively requires a good feel for under and oversteer and it's possible to get something that resembles a power over happening through the turns. It's fun for me since I play a lot of racing video games, but maybe less so for folks who don't.

Second gear (8:1) is about 8 ft/s or so. This is a good speed that allows better control, but hopefully we won't use it too much.

First gear (24:1) is a monster. It's slow and powerful and will allow us to politely escort robots and trackballs out of the way without a second thought -- especially given how highly geared most robots will likely be. I think folks are considerably underestimating the frequency at which traffic jams will appear on the field.

We're using one CIM per side after good experiences with that arrangement last season. We don't typically play to push people off to a corner to begin with, so the extra power is better used elsewhere. A single CIM, coupled with the Dewalt, ought to give us plenty of versatility out on the field this season. The remaining two motors are used elsewhere to good effect.

Finally -- switching the sprockets wouldn't allow us to shorten the axles any since the hub would just be sitting on the opposite side. It's not worth the work, anyhow, and it appears as if we're doing just fine with weight this year.

TonyP 25-01-2008 22:57

Re: pic: FRC488 Completed Drive Train
 
It is a thing of beauty! I notice your programming cable facing up. You have a 90 degree adapter of some type installed. Can you give me a hint as to where you picked that up?

Thanks

Tony P
FRC2151

ALIBI 26-01-2008 08:36

Re: pic: FRC488 Completed Drive Train
 
Looks great. I have always wanted to try 6WD but we usually end up with 4WD. Please take a minute and try to put the MK Battery in your battery holder. Last year we had to ask a sponser to remake our battery holder because the MK Battery is slightly larger than prior years batteries. You may have enough room, I can not see exactly how it fits in and it would be easier to fix it now if you need to.

Jeff K. 26-01-2008 11:36

Re: pic: FRC488 Completed Drive Train
 
Looks good, a driving platform done back in the first week will be advantageous for the drivers. How many students designed this?

Also about the 90* serial adapters. Do you have one on the radio too? I'm not sure if that is exactly legal, but looks relatively clean.

PizzmasterP27 26-01-2008 12:01

Re: pic: FRC488 Completed Drive Train
 
It doesn't look like you are direct driving a wheel.
Do you have a back up plan if your chain falls off?
just wondering, because it would be hard to drive with one side...

Coach Norm 26-01-2008 12:14

Re: pic: FRC488 Completed Drive Train
 
Quote:

Originally Posted by M. Krass (Post 683139)
We're planning on bumpers sitting between 3.5" and 8.5" from the floor -- and as such they land well above everything shown here except the wheels and motors. The bumpers, as a result, will be mounted to the super structure and spaced out beyond the wheels.

I am a Rookie coach here, so correct me if I am wrong please, but I thought the bumpers had to be 2.5" off the ground.

Your design is very inspiring. I have students who are making a catalog of pictures for various designs. They had made direct reference to yours as something they want to try and build during the off season in terms of the dewalts and 6 wheel drive.

Madison 26-01-2008 12:57

Re: pic: FRC488 Completed Drive Train
 
Quote:

Originally Posted by TonyP (Post 686002)
It is a thing of beauty! I notice your programming cable facing up. You have a 90 degree adapter of some type installed. Can you give me a hint as to where you picked that up?

Thanks

Tony P
FRC2151

The adapters were purchased from www.l-com.com.

Quote:

Originally Posted by ALIBI (Post 686058)
Looks great. I have always wanted to try 6WD but we usually end up with 4WD. Please take a minute and try to put the MK Battery in your battery holder. Last year we had to ask a sponser to remake our battery holder because the MK Battery is slightly larger than prior years batteries. You may have enough room, I can not see exactly how it fits in and it would be easier to fix it now if you need to.

The new batteries fit after a bit of gentle suggestion.

Quote:

Originally Posted by Jeff K. (Post 686102)
Looks good, a driving platform done back in the first week will be advantageous for the drivers. How many students designed this?

Also about the 90* serial adapters. Do you have one on the radio too? I'm not sure if that is exactly legal, but looks relatively clean.

We're really happy to have had a lot of time to practice driving with this and to let the students get a feel for it. It'll be advantageous, we feel, and that's why we worked very hard to get it done as quickly as possible.

We had similar adapters on our RC last season and were able to pass inspection at three events. We're not expecting any difficulties this season, either, but you never can tell.

Quote:

Originally Posted by PizzmasterP27 (Post 686110)
It doesn't look like you are direct driving a wheel.
Do you have a back up plan if your chain falls off?
just wondering, because it would be hard to drive with one side...

I don't expect the chain will come off. The chain is aligned well and tensioned properly. It hasn't yet come off in testing on this chassis or its predecessor.

Quote:

Originally Posted by Coach Norm (Post 686115)
I am a Rookie coach here, so correct me if I am wrong please, but I thought the bumpers had to be 2.5" off the ground.

Your design is very inspiring. I have students who are making a catalog of pictures for various designs. They had made direct reference to yours as something they want to try and build during the off season in terms of the dewalts and 6 wheel drive.

Figure 8-2 in The Robot states "bumper must remain between 2.5 inches and 8.5 inches off the floor." Since the bumper is 5" tall, there's some play there for mounting things and so we'll probably move it up as high as it can go as a result.

The Nothing But Dewalt white paper here on CD is a great resource for teams interested in trying a project like this out. We made a handful of very small changes -- the sun gear pressfit, the servo mount and the overall mount -- that we'll probably detail later on in the year. Most of these changes were made to suit our capabilities better and so that we could feel like we put a little bit of thought into the design ;).


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