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This is my new Vex robot Speedy. It is a 2-speed robot that has 6 drive motors and theoretical top speeds of 1.8 fps (low gear) and 9.0 fps (high gear). It uses a single servo to shift both sides of the drive system simutaneously. It has encoders that will later be used to make it shift automatically.
It is currently untested and missing batteries and a controller. Hopefully it works.
More images at http://www.team498.org/imagesSpeedy.htm
10-06-2006 15:48
lukevanoort
That is one densely packed Vex 'bot! One question though, why are there PWMs sticking out of the top?
10-06-2006 15:51
Rohith Surampudi
ok, 2 things
Firstly...WOW
Secondly,did you take the time to figure out the gear ratio 
10-06-2006 16:07
Nuttyman54
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Originally Posted by Rohith Surampudi
ok, 2 things
Firstly...WOW Secondly,did you take the time to figure out the gear ratio ![]() |
10-06-2006 17:36
travis48elite
One word descirbes that "WOW", that is something I have never seen done to the vex kits.
10-06-2006 18:09
Alex Cormier
amazing man, amazing! Great design and all. How many metal, chain and gear kits does that comprise of? I can't wait to see more of your designs in the future.
10-06-2006 18:37
Rohith Surampudi
30 boxes of krispy kreme Doughnuts to anyone whose team replicates this with scale proportions(must be built as close to the maximum size constraints as possible) as their 2007 robot 
10-06-2006 20:34
Donut
Thanks for all the compliments everyone! This is my second attempt at a Vex bot, the first was designed as a mini for this year's game.
The PWMs are indeed sticking out due to a missing controller. When I was working on the bottom I didn't want them to sit underneath the metal (since it was on its side for bottom work), so they are all twist tied to the top to keep them out of the way.
It has a number of gearings to transfer the power, but overall it has a 2:3 gear ratio in low gear and a 2:15 gear ratio in high gear.
I am worried about it being top heavy since there are 6 motors attached to the top layer, but with a battery and controller on the bottom I think it will balance out okay.
It uses up gears from the standard kit and one expansion gear kit (2 12-tooths, 8 36-tooths, and 6 60-tooths). It uses two chain kits though; I think you could get enough sprockets from one, but it uses so much chain that I only had 2 inches of chain left from both kits combined (this after moving the encoders closer to one side so I had enough chain). It uses 2 metal kits, but if you're willing to cut many of the long pieces and shafts to length it could easily be done with 1.
Speedy is 9" L, 11" W, and 8.5" H, if anyone wants to try
You'd have really big encoders doing that...
10-06-2006 21:32
Bill_Hancoc|
Originally Posted by Rohith Surampudi
30 boxes of krispy kreme Doughnuts to anyone whose team replicates this with scale proportions(must be built as close to the maximum size constraints as possible) as their 2007 robot
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10-06-2006 21:45
artdutra04
Very cool - I like it! Once this is done, I would love to see video of it shifting from low gear to high gear.
Just don't forget about gear train efficiencies. It looks like there are eight gear/chain reductions per side, and all those losses can all really add up. Each Vex gear reduction will only be about 90-95% efficient, while each Vex chain reduction will be about 95% efficient. 
10-06-2006 22:30
i_am_Doug|
Originally Posted by Bill_Hancoc
I that possible with the weight constraint???
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thinking about this makes my brain tickle!
10-06-2006 22:43
Kyle Love
Im betting that when it takes off it flips backwards.
Use the metal struts as anti-tipping bars...they work great.
11-06-2006 00:05
Donut
I'm willing to bet if you made the gears out of plastic still, you might be able to make an FRC bot like this. But if they're metal... those gears would be HUGE.
I am extremely worried about efficiency of the transmissions killing the motor power on this. There are 4 reductions from the closest motor to the first wheel, but there's an extra reduction added for each motor, and another for the omni-wheel (the vex encoder's just thrown on the end, I don't think that takes much power to run).
I just attached the radio, controller, and battery pack tonight. The battery pack is attached to the bottom because it lowers the CG tremendously and I had no where else to put it. It leaves me with slightly under 1/2" of ground clearance though, so no off-roading excursions are planned for Speedy.
12-06-2006 22:33
Donut
Okay, Speedy officially started running today. Some problems I have encountered...
1. High gear is geared too high, it has so little power it can barely accelerate and can't turn the robot in high gear
2. The robot will not shift into high gear while moving
I will be changing the overall gearing lower to fix the first problem, and I hope the second one will just take care of itself. The transmission shifts into either gear while stationary, and shifts from high to low on the fly, but won't shift from low to high on the fly.
Video will come when I can get it working better.
27-06-2006 00:26
RyanN|
Originally Posted by artdutra04
Very cool - I like it! Once this is done, I would love to see video of it shifting from low gear to high gear.
Just don't forget about gear train efficiencies. It looks like there are eight gear/chain reductions per side, and all those losses can all really add up. Each Vex gear reduction will only be about 90-95% efficient, while each Vex chain reduction will be about 95% efficient. ![]() |
19-07-2006 18:12
TheOtherGuy
wow. just like everyone else said. very interesting
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Originally Posted by Donut
I am worried about it being top heavy since there are 6 motors attached to the top layer, but with a battery and controller on the bottom I think it will balance out okay.
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Originally Posted by Donut
It uses up gears from the standard kit and one expansion gear kit (2 12-tooths, 8 36-tooths, and 6 60-tooths). It uses two chain kits though; I think you could get enough sprockets from one, but it uses so much chain that I only had 2 inches of chain left from both kits combined (this after moving the encoders closer to one side so I had enough chain). It uses 2 metal kits, but if you're willing to cut many of the long pieces and shafts to length it could easily be done with 1.
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19-07-2006 19:23
Donut
I didn't use the Vex battery as it was more difficult to connect. I haven't really tried to drain the batteries purposely or anything, but I can guarantee it runs perfectly fine for at least 5 minutes under heavy driving.