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Subject: 
Re: Using one motor to do 2 things...
Newsgroups: 
lugnet.robotics
Date: 
Fri, 27 Oct 2000 20:39:27 GMT
Viewed: 
463 times
  
Stupid me I just thought of another problem that makes this an engineering
impossiblity (I think).

How to reverse directions of the left/right action?  It seems making the
forward/backward motion and the left/right motion on the same motor is mutually
exclusive.

Is this right? :(

Looks like RCX #2.....


In lugnet.robotics, Mike McFarlane writes:
Hi Jason

It's a Friday night and my mind has disengaged so I've not totally thought
these through, but you could try a combination of ratchets and directional
gearboxes (as seen in the Unofficial guide to Lego Mindstorms by J Knudsen).
Basically you have one input shaft and two output shafts. The input shaft
drives a swinging arm and the drive train. So if you turn the motor one way
then the swinging arm moves to one side and drives output shaft 1 and if you
turn the motor the other way then the arm swings in the other direction and
drives output shaft 2. You could also try a ratchet on one axle so if you
reverse then the wheel on that side is locked (as in Robo 2 in RIS 1.0
Constructopedia) or possibly a ratchet onto a differential.

Anyway, just some thoughts for you to try. I'm sure someone else will give
you a more detailed plan or as normal some nice person normally has the idea
on a website somewhere. This isn't a particularly uncommom problem. Can I
extole the virtues of another RCX though - much more fun ;-).

Mike

In lugnet.robotics, Jason Rowoldt writes:
Hello Mindstorms fans,

I am suffering through a bit of an engineering block.  Let me explain:

I had an idea to build a drivetrain that will provide both front/back • movement
and left/right(turning) movement off one motor.  My question is: is this
possible?  It's hard to draw this in ASCII so let me try to explain.

* If you use a motor for front/back, you can configure an axle to also • provide
left/right movement through an (I'm not sure of the technical name here)
inverse of the gear (one of the gears that has teeth only on one side).  But • if
you do this, it means that anytime your chassis is going say, forward, it is
also going, say, left.  In the other direction, the chassis will go backwards
and right.  This will cause the chassis to do continual 3-point turnarounds.

*The way to overcome this is to disengage the gear that makes the axle (and
thus wheels through rods) from the main drivetrain (the part that makes the
chassis go forward/reverse).  However, I cannot think of a way to do this
without another motor.

The short question of this is: Is there any way to use one motor to do both
forward/reverse and turning capability?  Since the RCX has only 3 output • ports
and I need 2 other outputs for something else, that means buying another RCX.
$$$$:(

Looking forward to any ideas from the experienced LEGO engineers out there.

Jason, building a protoype battle robot.



Message has 3 Replies:
  Re: Using one motor to do 2 things...
 
(...) I think it would be very difficult to get workable bidirectional control of 2 things from one motor. However, it is quite possible to multiplex motors so you can do many more then 2 things from 2 motors. For example, you can have one motor (...) (24 years ago, 27-Oct-00, to lugnet.robotics)
  Re: Using one motor to do 2 things...
 
I don't know if this will help, but i'm currently working on a device that lets one motor drive four seperate axles. Downside is that it's one direction only, and only one axle can be used at one time. Howerver, you could use an extra gear to make (...) (24 years ago, 27-Oct-00, to lugnet.robotics)
  Re: Using one motor to do 2 things...
 
Could you do something with this trick? (URL) (24 years ago, 27-Oct-00, to lugnet.robotics)

Message is in Reply To:
  Re: Using one motor to do 2 things...
 
Hi Jason It's a Friday night and my mind has disengaged so I've not totally thought these through, but you could try a combination of ratchets and directional gearboxes (as seen in the Unofficial guide to Lego Mindstorms by J Knudsen). Basically you (...) (24 years ago, 27-Oct-00, to lugnet.robotics)

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