Let's Make Robots!

Need help with a Torque issue (suggest motors or another method)

I'm purposely being vague because this is my next robot and I believe this to be my last issue to work through. I have the circuit working on a breadboard and this is the last piece in the physical build.


Blue plastic "gear" 



Gear on motor pushing on red peg


Side view of gear on peg


What I need is something that can push the peg down and then let go. The motor is supposed to spin the blue gear which pushes down the peg. When the gear turns shallow again it lets the peg pop back out. As long as the motor turns is is supposed to continually push the peg down and then let go. The problem is the motor doesn't have enough torque when supplied with 9volts. If I turn it by hand it works perfectly. Any ideas on a new motor or another method I can use. The problem is ground clearance isn't much since I am using the solarbotics black plastic wheel and this is on the bottom of the bot between the front axles. I do have some linear gears which I could try to hook up to a gear mounted on a servo, but I doubt that would be enough torque either. Any ideas for motors (I need 4 so cheap is preferred under $5 each) or another method?  Each robot has 2 pegs and I would like each peg to be controlled individually, but to make it would I would consider if they worked at the same time.

Thanks for the help! I was hoping to finish the build tonight so I could work on soldering the circuit, but alas lady luck is not on my side!

And yes Frits those ARE paint sticks and that IS a ton of hot glue!


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This (product range) may interest you in general: http://letsmakerobots.com/node/3531
Still a little pricey. I used 4 AA and got more movement than the 9 volt. I need to buy some more AA batteries and try 9volts worth of AAs. If that doesn't work I ordered motors from the picaxe site with 6 times the torque for 80 cents each.
Quote from Miga:"The surplus NanoMuscle NM70-Super is still available in large quantities. The NM70-Super provides 0.16" of stroke with 2 oz. output force. Prices start at $9.95 each in QTY 10."
That is still $100. Plus the dimentions are too big to fit underneath. It would have to sit so that it is too tall for the wheels. I may resort to it if I have to, but I can't afford $100 especially since I only need 4.
It appears the motor shaft is somewhat off-center of the plunger being pushed by the cam. I believe it would be more efficient for the shaft and cam to be aligned better, shaft directly above the cam. The force of the cam would be then applied more directly downward, rather than pushing the plunger to the side. Perhaps the plunger can be more easily moved since the motor appears glued in pretty good.

The problem is there are 3 "centers".

The center of the cam using the longest side, the center of the cam using the shortest side, and the center of the cam by weight. The hole is predrilled. The motor is underpowered because the peg has a spring in it to push it back out and had some weight attached. It would all be cleared up if I posted a picture of the top of the robot, but I'm not until it is done ;) Even though it is controlled by IR and thus not a robot by some standards, it still has me excited about showing it off when it is complete.

I meant the hole in the cam as the center, where the motor shaft is, to be aligned with the plunger for best effect. A roller or ball could be put on top of the cam to reduce friction even more.

 To get the tourque you nee, I recommend a geared motor. I couldn't be bothered to find the for under $5 for you. But the first place i looked had several different models for $5.75

 I hade the same problem with my walker and I'm now battling the GM7's..

/ vzz-clck-"Maneuver"

I was going to say the same, but I'm just barely learning about geared motors..