Powering A Flywheel

SamR

Joined Mar 19, 2019
5,031
We had massive ~35° V-shaped steel rotors with blades in the body to disintegrate fat lighter stumps. They were about 8' in diameter and god only knows what they weighed. Operators watched an ammeter and held a dead man's switch in their hand for the 6' wide conveyor belt feeding the hopper for the "hogs". They would feed stumps into the hog and pretty much overload the hog and watch for the ammeter to drop back to the unload shaft amps before hitting the button to deliver another load. These were powered by ~900HP 460VAC motors. The antique starter overloads were cast iron grids that would get red hot under heavy loads and occasionally burn out. They got to be a pretty good judge about max loading as an overload burnout took several hours to clear and affected production which was to be avoided. You may want to incorporate a mA meter as part of the display.
 

MrChips

Joined Oct 2, 2009
30,706
I had a battery operated reel-to-reel tape recorder that used a governor on the motor spindle. When the motor was running too fast, centrifugal force would open a reed switch that would interrupt the current to the motor, a sort of mechanical PWM feedback controller.
 

Thread Starter

Cardinal799

Joined Feb 9, 2021
7
This device is meant to fit in the palm of your hand or be just a bit larger while still being handheld, so gearboxes and large circuit boards will not work. I ordered one of those geared hobby motors that runs at 150 RPM just to test out how well that works though.

You seem to have done your homework on flywheels. It is the rim that makes the difference with them, that, the way you explain it is how a flywheel for a machine is made, a thick rim with a thin center.

Is 9 volts a requirement? You said 9V battery in the OP. The regular 9V transistor radio battery, like the old PP3 type are a bad choice to run a motor,they are low amp hour. If 9V is a requirement you would be better off with using 6 flashlight batteries.
Yes, again for the sake of being handheld. I really hope that I can get this to work in some way off of a 9V battery, although I suppose I could include a liPo or some other rechargeable battery if that would get me better results with a similar size. What would be the relation between voltage and current with regard to the motor? Does a higher voltage mean it will spin faster while a higher current means it will supply more torque?

To maintain a constant speed with variable load seems to call for some feed back like a slotted disc, optical sensor, & assorted electronics. Reminds me of a desk display of a Jaguar speedometer which used a 20 slot disc with a slot detector with a variable input voltage to generate a PWM signal. 1 to 120 MPH.
For the sake of the project, since I need to do a cost analysis for this thing, I want to avoid using more advanced feedback mechanisms in order to keep costs down. Really it would not be the end of the world if the flywheel slows down by 5 or 15 RPM when under load, as long as it keeps moving at around the same speed and doesn't slow significantly.
 

Bernard

Joined Aug 7, 2008
5,784
Might take a look at a DC gear head motor by Pololu PN : 99-2202. 6V, 450 RPM no load, 10 X 12 X 26 mm. 4 AA or AAA batteries with simple 555 PWM ckt.
Motor also available from Jameco.
 

shortbus

Joined Sep 30, 2009
10,045
Does a higher voltage mean it will spin faster while a higher current means it will supply more torque?
Yes to both of them. The 9V pp3 will work but not for very long. You can find battery holders for 6 AAA or AA cells and make that the base, building the rest on top of it.

As to the "hold in the hand", can you push the envelope a little on the rules? By making it bigger and put a handle on it, so it's held by a handle, like a bucket or basket? Is this a school assignment/ challenge?
 

Thread Starter

Cardinal799

Joined Feb 9, 2021
7
Okay, so I got my parts in today. The geared motor is definitely what I needed. I think I need to order a 12V 330RPM rated motor for my final build. The PWM controller lets me go below that RPM value easily, and from what it looks like I need to use a motor rated above my 9V, instead of overpowering a 6V rated motor during normal operation. I can't test out how well this will work with a whole metal flywheel, that will be built later. Right now all I have are cut out cardboard circles that slip very easily, so I can't mess around with the resistance very much. Do the Polou motors work well? I think I will order from them because they also sell wheels that are about the diameter I need with a D-shaft hole already built in which will help with testing.

https://www.pololu.com/product/2997 Is there a way to use this as my PWM controller? This way I can wire my potentiometer somewhere else instead of it being on the board. Or would it be difficult to design a controller myself?
 

wayneh

Joined Sep 9, 2010
17,496
... it looks like I need to use a motor rated above my 9V, instead of overpowering a 6V rated motor during normal operation.
Check the voltage on the battery terminals when your motor is running. I'd be surprised if it's over 7V.

OTOH, it's fine to run a 12V motor at 9V. You won't get the rated torque but it'll run.
 

BobaMosfet

Joined Jul 1, 2009
2,110
Hi! I am working on a project for school. I am trying to find a way to power a metal flywheel (about 2.5" in diameter) off of a 9V battery using an electric motor. The speed should be variable with the use of either a potentiometer or a pair of buttons, between 100 and 300 RPM. The goal is to maintain a consistent speed even when there is some outside resistance against the flywheel edge (like a finger pressed against it), and the torque from the motor should be reasonably similar/consistent at both low and high speeds. This should be able to fit in the palm of your hand.

I have some knowledge of basic circuit components, not enough to know what my requirements would look like in order to design a functioning circuit though. I do want to learn for the sake of this project and I have a mentor to help me, but I do need some help first with figuring out what this circuit might involve. I am trying to stick to analog only to keep it simple, unless that doesn't actually make the circuit less complicated. I'm also wondering how many of these components I can find easily online. I also am not sure how to come up with the formulas I need in order to see what is going on physically, like how much energy will be taken out of the spinning flywheel when it encounters resistance and how that relates to the power coming from the motor. I can try to figure that out on my own though.

Any help would be greatly appreciated!
...and have you asked your instructor to help you with this? That _is_ what they are for.
 
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