Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: karrotx on January 07, 2011, 01:19:49 PM
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Hello,
I've calculated the required torque for the motors to be around 2000oz-in. I need help finding motors that fit these requirements; what I've found is ridiculous price tags as well as current draw that's in the 100 A's.
Is there a motor that you would recommend that can get close to 2000oz-in of torque as well as draw less than 20amps?
If not, what do you recommend? I'm currently looking into motors that came up when searching "battlebot motors." What have you used?
I appreciate all advice!
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2000oz-in is a huge amount of torque. That's comparable to a car engine. Why do you need so much torque? Are you sure you calculated correctly?
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Besides what VegaObscura said:
Have you considered the output speed of the motor and whether a gear reduction is required?
Gear reduction increases Torque and decreases RPM.
I'm sure you may be able to find a motor/gear box to deliver that torque with 20A draw but at a very, very slow RPM.
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that's not a huge amount of torque and there should be plenty of choices when it come to finding motors , I cant point you in the right direction as I have no idea what type of motor you are looking for .
you may whant to look at NEMA type stepper motors . I have a few that give 1200 Oz in and only draw 6 amps at 80v .but only use a stepper if you really need one as they can be a bit tricky sometimes.
Another good source for motors is eBay ,I use it for research on what is available out there . look under >industrial>electric motors or just do a search on electric motors .
2000 Oz in = 14Nm
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Hi karrotx
Well you guessed it right...the battlebots motors will surely do the job. It's a very simple logic here. You need a high torque(i am guessing at high rpm) then you have two options to work with. Either supply huge current or voltage. Here check this one. I believe the LF model suits your needs.
http://www.pranshu.com/htm/pmdc_model_series/model_Lseries.htm (http://www.pranshu.com/htm/pmdc_model_series/model_Lseries.htm)
Good Luck.
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I'm not sure how you could determine requirements by the torque alone. I went through this for the first time recently and looked up some physics. You can have 2000 oz-in at 1 RPM or 1000 RPM and the difference in power requirements is 1000X.
To put things into perspective, I just got some 200 oz-in motors that turn 150 RPM @ 12V and 5A. If I then put that through a 10 to 1 gear reduction, I would have 2000 oz-in, which meets your requirements but is almost certainly not what you want because it would turn 15 RPM.
You need to know power to meet a requirement for a robot. You need both RPM and torque to know power. Car engines are compared in power.
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The relationship between power and torque is confusing .
Power is a product of torque and the annular speed (rpm ) given roughly with P = M(N.m) x 2π x annular speed.
when you design a bot (or anything)and need a motor you need to know how much torque is needed and at what rpm , this gives you the power needed .
Torque is the measure of the twisting force of a motor and if a motor does not have sufficient torque it will not do the job required no matter how much power it has .
Car engines are rated in power but you are looking at things in an entirely different perspective