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Duane Benson
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Re: Motors
Duane Benson   10/25/2013 7:08:35 PM
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I do. No load 500 Rpm, 250 rpm at rated torque.

Aeroengineer
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Re: Motors
Aeroengineer   10/25/2013 6:59:14 PM
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Do you know what the no load speed of the motor is?

Duane Benson
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Re: What does "Torque: 0.78Kg-cm (rated load)" mean?
Duane Benson   10/25/2013 6:58:08 PM
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Caleb / Max - Mostly I'm working on putting in all of the features I accidentally left out of version 1.

Duane Benson
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Re: Motors
Duane Benson   10/25/2013 6:56:37 PM
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Aero - I've got a motor I'm dealing with (the one I emailed about) that produces 8.5 inch pounds of torque. The limited data I have gives a current of 16 Amps. I'm assuming that's stall current, but it doesn't say.

One of the challenges for me is translating the weight of a robot into power required to move it. It would have to consider weight, rolling resistance, desired acceleration a dn any amount of slope I might want. I suppose I qould emperically determine how much force it takes to move something, but that means I can't really design it until after I've designed and built it.

I'm not sure about a plastic adapter (from 4mm square shaft to something round). I don't know how well the plastic would hold up. Short of getting a piece of metal machined, I just had another thought. I could get a pair of flat L brackets and bolt the together suchb that they have a 4mm square in the middle and four ends sticking out that I could then bolt to a wheel or something. Does that sound workable?

Aeroengineer
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Re: Motors
Aeroengineer   10/25/2013 6:38:31 PM
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Duane,

 

No worries.  I really love DC and BLDC electric motors.  I have dedicated some amount of study to them.  DC electric motors are easier to understand and easier to control, but BLDC motors offer more power density and usually they have better efficiencies.  This is not always the case, but it is a good generalization. 

 

One thing, though that I have found by creating the simple chart that I described is that you can then you can back out how much torque you are actually using and then size your next round of motors more appropriately.  If you take your current motor and make that chart, and then you put the motor under the worst load that you are expecting, you can then measure the RPM of the motor (assuming that you have an encoder and some way to record this).  Once you have this RPM, you can go back to the chart you created and just fine on the line the value of the RPM.  You then read on the Y axis the torque.  Now you have a better estimate for your next round of motors.

 

Oh and did you get my email on how to solve your motor adaptor problem?  I think that it will work for you.  Let me know if you need any help getting that drawn up.  I can help out with that.

David Ashton
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Re: mercurial Max
David Ashton   10/25/2013 6:30:50 PM
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I think we all prefer the gruntled and consolate Max to the disgruntled and disconsolate one......

Duane Benson
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Re: Motors
Duane Benson   10/25/2013 6:29:50 PM
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Aero - This is great information. My brain is missing a lot in terms of all things mechanical. I tend to just guess with motors and end up with more power, weight and cost than I really need.

Caleb Kraft
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Re: What does "Torque: 0.78Kg-cm (rated load)" mean?
Caleb Kraft   10/25/2013 5:13:32 PM
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I only squeel like a schoolgirl when I get scared Max. Are you going to scare me with this? Oh also when I met Keepon.

Max The Magnificent
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Re: What does "Torque: 0.78Kg-cm (rated load)" mean?
Max The Magnificent   10/25/2013 4:50:22 PM
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@Caleb: I want to know what you guys are working on!

When you hear, you'll be squealing like a schoolgirl also :-)

Max The Magnificent
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Re: What does "Torque: 0.78Kg-cm (rated load)" mean?
Max The Magnificent   10/25/2013 4:49:30 PM
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@DrFPGA: From no happy dance to school girl squeal in about 30 seconds. You are one mercurial guy max.

Fortunately I'm blessed with a happy-go-lucky disposition -- plus it is Friday, and as soon as I get hom it will certainly be a case of the (beer) glass being more than half full (but not for long :-)

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