Re: Minibot climb rate
 

A house "4 way" switch will reverse the motors...

Re: Minibot climb rate
 

*blinks*
I hadn't even heard of four way switches. That's even better!

Re: Minibot climb rate
 

4 way switches are use in rooms where lights are controlled from more than two places at once. The first two locations use 3 way's and the 3rd "or more" use 4 way's. The switch has 4 terminals on it . In one position it connects across. In the other position in cross the terminals. Great for reversing DC motors.

Re: Minibot climb rate
 

Our minibot got to the top of the pole today in 4 seconds. I'd love to share the video, but its "Top secret Confidential" stuff right now :yikes:

Re: Minibot climb rate
 

Food for thought...4 way switches will indeed help you reverse your motors but there is a cost. Even stripped down they are relatively heavy and also one must consider the rate of the descent and the endpoint velocity as your bot strikes the base platform. Not sure what the effect on the field element will be. Has anyone tested a motor aided return to the base platform?

Re: Minibot climb rate
 

wouldn't a simple resistor on the switch be enough to make it drive slower in one direction but not effect the upwards movement?

Re: Minibot climb rate
 

If resistors & diodes were allowed, perhaps when combined with a diode this would work fine.

Re: Minibot climb rate
 

gah! of course in my haste to develop a simple easy solution i forget to check the list of acceptable parts... ::rtm::

Re: Minibot climb rate
 

If you are intent on driving it down, you can switch the motors to be in series and this will at least cut the voltage in half for each motor which effectively cuts the power by 1/4 th.

But I can't imagine that the drag torque of these motors when properly geared for speed will be enough to hold the bot up the pole with no power. I don't have a number for the FTC motors but the vex 393 motors have about 1 inlb of drag torque or about 7 % of the Max torque. If the FTC are about the same % then you would only get about 21 oz in of drag per motor or a total of 42 oz in (2.6 inlb) for two motors. . The load torque for a 4 lb minibot would be 4*radius*gear_ratio which for a typical mini bot is 4*2*2 = 8 inlb. So I think the minibot should come down by its self with my assumptions.

Re: Minibot climb rate
 

I was thinking,
On->forward...contact->up... contact->off...gravity-> down.
on/off .12 lb 4 way .18 lb

Re: Minibot climb rate
 

4.5 second climb on first proto... time to lose some weight...

Re: Minibot climb rate
 

Perhaps it would also be useful to monitor wheel encoders as well. If the wheels travel 12 ft climbing a 10 ft pole, your problem isn't weight. Viewing the velocity and other derived values per wheel would be pretty interesting to evaluate different prototypes.

Greg McKaskle

Re: Minibot climb rate
 

are you allowed to use the surgical tubing on the mini bot????

Re: Minibot climb rate
 

You are absolutly correct that this information would be very usefull. The problem is, if you added the encoders and an NXT to capture that information, you would be radically changing the characteristics of the minibot. The data would not be relative to the actual performance of the bot in it's final configuration.

Re: Minibot climb rate
 

<R92> The following items are the only permitted materials for use on the MINIBOTS:
U. Rubber bands,
V. Surgical tubing,