Society of Robots - Robot Forum
Mechanics and Construction => Mechanics and Construction => Topic started by: Deffie on June 23, 2008, 02:06:21 PM
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Lets suppose i have this motor:
450W 24v
2500 rpm 1.9 nm
reduced by 35:1:
71 rpm 66 N/mt 6.7 kg/mt without considering losses
And lets plan our robotic platform:
Mass: 30 Kg
1.1 Mt/sec 3.9 km/h
0.5 m/sec accel.
75 % Efficency (the default)
10 degrees incline angle
0.3 meters wheel diameter
4 powered wheels
Rmf says:
12.6 kg/m/sec RMF
33 kg*m/sec
70 rpm motor rotation speed
And my motor:
6.7 kg/mt
71 rpm
7.9 RMF
Now:
One of these 450W drives an electric tricycle over 20 Mph with a man on it, which can weight 100kgs;
i'm using four of them for 30kg and RMF calculator says it is not possible.
Theres something wrong...help! :)
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Im not seeing where you calculated the 35:1 reduction...
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2500 rpm 1.9 nm
reduced by 35:1:
71 rpm 66 N/mt 6.7 kg/mt without considering losses
2500/35=71 rpm
1.9*35=66 Nm / 9.8 = 6.7Kg/m
This is how i calculated gearbox reduction but maybe i'm wrong...
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Ping!
Where is RMF calculator creator ?
:P
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One of these 450W drives an electric tricycle over 20 Mph with a man on it, which can weight 100kgs;
i'm using four of them for 30kg and RMF calculator says it is not possible.
The calculator doesn't say it isn't possible to drive a man around, only that it cannot go at the specs you entered. For example, did you measure the acceleration or incline angle or efficiency for that 20mph run? :P
Also, where did you get the rpm/torque data for the motor? To use it properly, you need to get it from a rpm to torque curve on the motor datasheet . . .
For example, you wrote the motor goes at 71rpm with a wheel diameter of .3 meters. If you do the math, that only comes out to 2.5 mph.
Waaaaay lower than your 20mph :P
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The calculator doesn't say it isn't possible to drive a man around, only that it cannot go at the specs you entered. For example, did you measure the acceleration or incline angle or efficiency for that 20mph run? :P
Please reread my post, i'm not aiming at 20mph, but 1.1 mt/sec -> 2.4 mph, 3.9 km/h which is about a walking human.
Also, where did you get the rpm/torque data for the motor? To use it properly, you need to get it from a rpm to torque curve on the motor datasheet . . .
I've got them from the motor's datasheet
For example, you wrote the motor goes at 71rpm with a wheel diameter of .3 meters. If you do the math, that only comes out to 2.5 mph.
Waaaaay lower than your 20mph :P
2.4 mph is just what i was expecting, Waaaaay similar to what you calculated :P
Take a look at this scooter http://www.electrikmotion.com/gt450main.htm , it is equipped with a 450w motor and with a man on it (80kgs ?) does 15 mph, lets assume it is optimstic, lets say 10 mph; why i cannot do that with four 450 watt motors and 30 kgs?
I just want to understand, i'm not saying your applet is wrong, i feel it useful and i just have to size motors for my project :)
Thank you,
Giacomo.
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It makes a claim of 15mph, but that doesn't really mean anything because it doesn't account for the weight of the rider or the incline or the desired rate of acceleration.
You need to account for everything in my calculator . . .