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As it's approaching the dog days of summer, this can only mean one thing: summer break is over. It's time to start building robots again. 
Like a Lemming being driven to the sea, today I had a strong urge to build a robot. Not just any robot, but one which is new and innovative. Naturally, I wanted to set the stakes higher than before. For your dining pleasure tonight, here's a custom Vex drivetrain concept using a beefier motor and a worm gear. 
Since this bad boy likes to suck over an amp of current, I cannot power it solely off the PWM ports - I needed to power it using a speed controller. In this case, it was a spare Victor 883 that I had lying around my house.
I don't know it I'll finish this robot, as all I really wanted to do was test the concept of seamlessly integrating non-Vex-legal parts into Vex robots. This is just a teaser for my next project which I am working on right now, which takes a Vex/non-Vex hybrid idea to the next level. 
(Note: These are not VexLABS parts; these were parts that I was able to find in middle-school-age Tech Ed Teacher curriculum catalogs.)
Discussion
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29-07-2006 22:14
Jeremiah Johnson
Re: pic: Vex Teaser: What's Art been up to lately?
Wow... I've never seen anything like this before. A worm gear driving the 32-tooth (?) gear right to the wheel. Hm... how well does it work? Does the worm gear ever slip from the Vex gear?
29-07-2006 22:23
Jay H 237
Re: pic: Vex Teaser: What's Art been up to lately?
Are you going to set this frame up as two or four wheel drive? Or do you just have other plans?
Be sure to post pics of the finished project. 
29-07-2006 23:51
artdutra04
Re: pic: Vex Teaser: What's Art been up to lately?
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Originally Posted by Jay H 237
Are you going to set this frame up as two or four wheel drive? Or do you just have other plans?
Be sure to post pics of the finished project. |
The motor here has a fairly high amount of torque for something it's size. Under a moderate load it runs at about 2,500 rpm, which is geared down through the worm gear 36:1 to about 69.4 rpm. Just to see how powerful it was, I geared it down an additional stage (using two 60t and two 12t gears, so as to split the load between them) using a 5:1 reduction. It was practically impossible to stop the output shaft of the stump-pulling second reduction.
At the moment I am working on a much more complicated design that mechanically will calculate the difference between two input shafts. For example if both shafts were rotating CCW at the same RPM, the difference between the two would be zero. But if the two input shafts were moving at different speeds the output shaft would rotate in one direction (CW if shaft A is faster, and CCW is shaft B is faster) at a speed proportional to the difference of the two shafts.
30-07-2006 00:23
Dan Petrovic
Re: pic: Vex Teaser: What's Art been up to lately?
Where did you get the worm gears?
I was a bit frustrated at the lack of worm gears when my arm kept backdriving when I picked up mini tetras.
30-07-2006 01:11
artdutra04
Re: pic: Vex Teaser: What's Art been up to lately?
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Originally Posted by InfernoX14
Where did you get the worm gears?
I was a bit frustrated at the lack of worm gears when my arm kept backdriving when I picked up mini tetras. |
Note: I bought them about two years ago for another project, so I'm not sure if they still carry the exact same gears.
Any 24 pitch (or close enough) gear can mesh with Vex gears...
30-07-2006 15:49
John Gutmann
Re: pic: Vex Teaser: What's Art been up to lately?
you can also go to kelvin
16-11-2006 23:29
jgraber
Re: pic: Vex Teaser: What's Art been up to lately?
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Originally Posted by artdutra04
...
At the moment I am working on a much more complicated design that mechanically will calculate the difference between two input shafts. For example if both shafts were rotating CCW at the same RPM, the difference between the two would be zero. But if the two input shafts were moving at different speeds the output shaft would rotate in one direction (CW if shaft A is faster, and CCW is shaft B is faster) at a speed proportional to the difference of the two shafts. |
Were you able to make a "South Pointing Chariot"?
Was it to make your holonomic drive "driver centric"?
Links from here might give you some ideas on differentials.
http://en.wikipedia.org/wiki/South_Pointing_Chariot
I thought the screwdrive one has some promise due to no requirement for bevel or planetary gears. You might also consider just doing the integration computationally, based on optical wheel encoders on the drive wheels or drag wheels.
17-11-2006 08:26
artdutra04
Re: pic: Vex Teaser: What's Art been up to lately?
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Originally Posted by jgraber
Nice work on the worm gear. Now that it is a few months later, how did it go?
Were you able to make a "South Pointing Chariot"? |
| Was it to make your holonomic drive "driver centric"? |
| You might also consider just doing the integration computationally, based on optical wheel encoders on the drive wheels or drag wheels. |
13-01-2007 23:46
Jared W
Re: pic: Vex Teaser: What's Art been up to lately?
hey
hows it coming?
I'd really like to see a movie of the bot in action.
To see how much faster a bigger motor will be.
I hope next season Vex will release beefier motors for torque or speed.
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