Robot DC motors

[alec_t]

Looks ok. A surprisingly low value. Good luck with the build. I wouldn't like to be anywhere near if the flywheel broke loose .

 

[alec_t]

Post deleted

 

[fortion]

alright so i have need an output of 12 W approx from DC motor . how much efficiency can i expect from DC brushed motor ?? is 50% a safe guess ??

 

[alec_t]

I don't know. Do some googling. Bear in mind that the motor will be more or less stalled for a lengthy period while getting the flywheel up to speed, so will draw a large current. I guess efficiency varies with rpm and load.

 

[fortion]

ok . got a really good deal on DC motor . A used DC motor of 24 V and 9.6 A with 450RPM . i'm guessing the efficiency to be around 50% . is it going to be enough ?

 

[fortion]

and the good thing is the motor cost was just 25 $ . a really good deal

 

[alec_t]

is it going to be enough ?

Time will tell .
BTW, is that 9.6A the current at max speed? If so the stall current will be MUCH greater.
You will need bigger batteries than 5Ah if you want more than a few minutes running time.

 

[fortion]

Time will tell .
You will need bigger batteries than 5Ah if you want more than a few minutes running time.

yup it is the current at max speed . i thought about using a 24V 7Ah batteries . think it will be enough . i only need them to run motor for 12 to 15 minutes

 

[alec_t]

If I were building this I would assume the average motor current would be ~20A, which means the 7Ah battery would be completely flattened in 7/20h = 20mins. You don't want to run a battery completely flat or you'll kill it. So 7Ah would not be enough for 12-15 mins in my opinion.
BTW, are you aware the gyro effect of that flywheel will be huge and make the robot impossible to steer unless the flywheel axis is vertical?

 

[fortion]

If I were building this I would assume the average motor current would be ~20A, which means the 7Ah battery would be completely flattened in 7/20h = 20mins. You don't want to run a battery completely flat or you'll kill it. So 7Ah would not be enough for 12-15 mins in my opinion.

ok i got that . will have to think of something else then . this is going to be problematic

 

[fortion]

BTW, are you aware the gyro effect of that flywheel will be huge and make the robot impossible to steer unless the flywheel axis is vertical?

YUP . i'm aware of that . the flywheel axis is going to be vertical . i am using bevel gears to change direction of rotation