View Full Version : Getting ready for the next season

07-21-2002, 05:43 PM
Hi everybody!
I want to thank everyone for a great FIRST season.

In the mean time to improve on my engineering knowledge I took on a project that involves testing different configurations of a flywheel. To start this project I will need to find a suitable motor to spin the flywheel and a generator with a resistor block to simulate load. From there the calculations for the flywheel will be made (Size, mass etc) and the different configurations tested. The problem is that there are so many companies offering motors and so few offering generators, that I got lost. I would appreciate any suggestions from you, the bright minds of FIRST.

For the power of a motor a figure of 1/3HP was thrown (Does any one by any chance have any idea on how to convert that into Watts?), since the power rating of the motor is the starting point Im open to suggestions in this aspect. The motor should be around 12V DC, since this is one of the most common voltages. The generator should have a rating comparable that of the motor, so it would be able to effectively provide the load on the flywheel. A built in tachometer would be a nice feature to have.

If anybody has any suggestions to where I could find those materials I would really appreciate it. I will keep posting the progress of the project once I get it started.

Thanks a lot for your support! :)


Tom Schindler
07-21-2002, 09:52 PM
1 HP = 746 watts..... so 1/3 hp = 248.6667 watts.


Andy Baker
07-22-2002, 09:24 AM
Here are some suggestions on where to get some of your needed stuff:

Flywheel - McMaster Carr has tons of metal wheels of different weights and sizes. If you don't want one to big (6" dia. and under), it looks like you can find one for under $30. Either go to McMaster Carr on the internet of find one of their handy catologs.

Generator - I'm not an expert in this area, for sure... but I'll provide another suggestion: I'm not sure about this, but I think that an automotive-type alternator may work for your needs. A typical car's alternator is probably too big for your use, but I assume that it provides the right type of output for what you want to do. Someone with more experience with smaller alternators may need to jump in here.

Tachometer - McMaster Carr also has a these, in a variety of styles.

Sorry I can't help more.

Andy B.

07-22-2002, 03:39 PM
I have noticed that some motors (Just plain motors, w/o any gear boxes and other mechanisms) seem to spin freely once un-powered while others seem
to stop. Or when spun by hand some continue rotating while others stop. It is very important for this experiment to get a motor that would not interfere with the rotation of the flywheel. I would appreciate if anyone could tell me how I could distinguish between two motor types.


07-23-2002, 06:01 PM
I think it has something to do with the strength of the magnets in the motors.

Andy A.
07-23-2002, 10:06 PM
Any motor will slow down after you remove power, all motors have some friction and resistence in them. To completly remove that influence, you'd need to some how use a clutch to disconnect the motor from the gearing. Or, even better, the flywheel from the gearing.

As for a generator... Why not just a D.C. motor? Put some resistors across the leads to simulate load. D.C. motors function just like generators in this way. This is probably cheaper then a generator.

One note, you should probably use a fuse or breaker in the resitor block... Other wise you might melt down some resistors and/or start a little fire.

-Andy A.

Matt Reiland
07-24-2002, 07:19 AM
You can get cheap digital tachometers from tower hobbies also they are used to check prop speed on air planes but should work on your test stand also.

07-24-2002, 11:15 AM
Anyone know where to get a decibel-ometer? To measure the volume of sound in decibels?

07-24-2002, 10:22 PM
Thanks Guys! I appreciate your support! I said the same thing to my mentor about the generator, but he said generators and motors are made differently. I guess he was probably thinking about an AC generator.


Matt Reiland
07-25-2002, 10:25 AM
You can get a sound meter at radio shack used for setting up Home theaters to a reference level, the analog meter is suggested and it is pretty inexpensive.