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 Innovating for the sake of innovating, reinventing the wheel is probably the second biggest pitfall you can fall into when designing an FRC robot, if the wheel is already a very optimized, good solution. - Chris is me [more] |
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By: Alex.Norton
New: 06-05-2007 16:15
Updated: 06-05-2007 16:15
Views: 1418 times
I took a lot of your advice on this one. The major changes that I have made for this one are:
1.When thinking about the manipulator control I found that I didn't have a good actuation without the fisher price so I wanted to pull those our of the system. I also wanted to get the control complexity down (didn't as much as the other system provided). So I changed the banebots to globes.
2. I really liked those magnetic encoders to I added gears and mounts for them. I didn't bother putting them in the model but there is nothing to indicate that they would not simply "snap" in.
3. Because I didn't need the turning motors above the modules anymore I can now run the motor wires out of the top so I needed my support to be a tube. For this I when from 1/2in ball bearings to sleeve bearings with a one inch diameter pipe that would be able to bolt into the module (still can't weld aluminum).
4. The arm in general. I actually wanted to ask some questions about this. My team has done a very similar arm in the past so I'm not worried about control but I didn't like the design that we used for the bottom of the arm because is didn't really fit into the rest of the frame so I was trying to make this part of the frame and I wanted it to be very compact with as few large pieces as possible.
To optimize all this I wanted the drive sprocket for the bottom part of the arm to be on the outside of the supports because I could use the same piece to mount both the arm and the motor. However, I wanted the sprocket to mount to the arm with bolts so that the torque wasn't being put on a shaft and to spread out the force. Of course this would mean that I needed a ~2.5in inside diameter bearing. For this I used three pieces of 1/4in polycarb and some delrin as the bearing surface. You can kind of see the mount on the far side of the arm. Would this work? How would it fail? How long would it last in you opinion?
I have never put a large amount of force on something like this and don't know how it would respond.
Thanks
Discussion
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06-05-2007 19:58
zander_108
Re: pic: A little more standard
I like your design.
However, a few questions;
How much does the entire robot base as pictured weigh?
How much does each wheel module with motor weigh?
keep up the good work
07-05-2007 19:46
Alex.Norton
Re: pic: A little more standard
thanks, the entire robot weighs 52 pounds with arm and modules, however, this does not include elctronics and chains which I bet adds to at least 20 pounds and could be more, so i think it would weigh between 70-90 pounds.
Each module with motor is 5.05 lbs.
thanks
08-05-2007 10:57
Greg Perkins
Re: pic: A little more standard
I'm having a hard time seeing what the benefits are with this design, all I can tell and assume is your going to have an issue with keeping those gearboxes safe. I also can tell that if you are rotating your wheels those gearboxes are going to rotate outside of the robot too, and thats just asking for trouble.
If I was designing this, I would mount 2 andymark or a custom shifter (or not) gearbox vertically inside the robot, and then run chains to each corner. Each module would have a shaft that ran down the tube, and mated bevel gears to the wheel shaft, then have just the wheels exposed
Other than that, the chassis and arm design looks good!
08-05-2007 20:11
dbell
Re: pic: A little more standard
looks great,
the gearboxes look a little wobbly to me. maybe they need better support?
and better protection too?
but on the whole, very nice.
16-05-2007 07:11
robostangs548
Re: pic: A little more standard
I love the design, but I still don't know if the floor to robot strength is going to be enough..... You have to think about the possibilities of.... Is that going to be strong enough to have something that weighs around 130 hitting you consecutive times, and is anything going to break. I do like the swivel steer ideas, but I am more of a person who builds my robots like a tank. That way, it is durable, easy to fix, and I don’t have to worry about it after every round. Other then that great design.
16-05-2007 12:32
Madison
Re: pic: A little more standard
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Originally Posted by robostangs548
I love the design, but I still don't know if the floor to robot strength is going to be enough..... You have to think about the possibilities of.... Is that going to be strong enough to have something that weighs around 130 hitting you consecutive times, and is anything going to break. I do like the swivel steer ideas, but I am more of a person who builds my robots like a tank. That way, it is durable, easy to fix, and I don’t have to worry about it after every round. Other then that great design.
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16-05-2007 15:48
Daniel_LaFleur
Re: pic: A little more standard
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Originally Posted by M. Krass
Without speaking about this design, particularly, I think it's worth mentioning that plenty of teams have had many, many successful seasons without building robots "like tanks." There's a thing or two to be said about graceful design and engineering and intelligently discerning which parts, assemblies and systems need to be more or less robust than others.
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I don't want to turn this into a "tanks vs miracle machine" debate. I just want to point out that you have to understand the strengths and weaknesses (yes they all have weaknesses) of your robot, and prepare to deal with those.
//back on topic
I'd love to see that drivetrain in action.
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