Window Motor vs. Fisher Price

[gabrielau23]

Hey guys,
I was doing some research on Window motors and Fisher Price motors, but the most comprehensive research I could find was a Chief Delphi thread from 2002. For say, an arm that needs to go nearly to the ground and then back up (think Logomotion), I was thinking of, if this game requires it, either a Fisher Price or a Window motor. What are you guys' thoughts on it? Are there any advantages to either motor? Also, under the category of Window motor. I was going through FIRST choice, and I found a Keyang window motor. Has anybody used it before with success? I think our team's only used the Denso's before. Thoughts on the Keyang as well? Thanks

[Ether]

Originally Posted by gabrielau23

Hey guys,
I was doing some research on Window motors and Fisher Price motors, but the most comprehensive research I could find was a Chief Delphi thread from 2002. For say, an arm that needs to go nearly to the ground and then back up (think Logomotion), I was thinking of, if this game requires it, either a Fisher Price or a Window motor. What are you guys' thoughts on it? Are there any advantages to either motor?

I depends on how much unbalanced torque is on the arm and how fast you want to move it.

The 2012 FRC-legal FP motors range in power from 172-292 watts.

The Denso window motors are 23 watts.

[Richard Wallace]

By fitting the Barbie gearbox with some kind of power take-off (example), it can be used to drive a winch, with plenty of power for an elevator.

As JVN and others have pointed out, by balancing an arm you can reduce the motor power requirements significantly, because the motor lifts only a gamepiece rather than the whole mechanism.

[gabrielau23]

Thanks guys! Richard, for the take-off you mentioned, the picture described the plug as "cast aluminum". Does that mean it was custom formed? Because I don't think our school has that capability. .
As for balancing the arm, I found an awesome thread on Chief Delphi here:
http://www.chiefdelphi.com/forums/sh...d.php?t=109795
I have some questions about that, but I'll go over to that thread for balancing the arm.

[EricH]

Originally Posted by gabrielau23

Thanks guys! Richard, for the take-off you mentioned, the picture described the plug as "cast aluminum". Does that mean it was custom formed? Because I don't think our school has that capability. .

Do you have a hacksaw? You can make your own by taking a block of aluminum of the right size and applying elbow grease (via hacksaw) to get the shape you need. You could also build them from wood, or use more advanced machines like a bandsaw or mill if you were to have those available.

[Ether]

Originally Posted by EricH

You can make your own by taking a block of aluminum of the right size and applying elbow grease (via hacksaw) to get the shape you need. You could also build them from wood, or use more advanced machines like a bandsaw or mill if you were to have those available.

... or cast your own. This stuff is super easy to use and quite tough when fully cured.

[Lil' Lavery]

Generally speaking, a window motor is probably going to be underpowered for a large arm*. At the same time, FP have a nasty tendency to burn up if you stall them, so you have to be careful with your arm design and transmission choices to avoid stalling a FP motor.




*Yes, I realize balancing can reduce the load on a motor.

[StevenB]

I don't mean disrespect here, but your question is similar to asking, "I'm trying to dig a hole, and it seems like spades and 50-ton CAT excavators are common. Which one is better?" The answer, clearly, is that they are different tools for different jobs. The catch is that you have to know what the job is.

Either motor can be used to drive an arm; it's just a matter of how quickly. As Ether pointed out, the FP motors are approximately ten times more powerful than the Denso motors. At the risk of tooting my own horn, please take a look at this: A FIRST Encounter with Physics. I wrote it specifically to answer these kinds of questions.

[gabrielau23]

@EricH, yeah our school has band saws and a mill. And we just found a pre-WWII lathe. I think we can do that.

@StevenB
Sorry about that. I had done my research and accidentally compared 2001 FP motors with current Densos.

@Lil' Lavery
So if there is an arm this year, the design MUST balance the arm if we plan to use FP motors, correct?

[Lil' Lavery]

Originally Posted by gabrielau23

@Lil' Lavery
So if there is an arm this year, the design MUST balance the arm if we plan to use FP motors, correct?

Not necessarily, but I certainly would suggest it. Balancing an arm would be a relatively simple and elegant solution to avoiding stalling a motor and opening yourself up to lower power motors.

The way that you'd typically stall an FP motor in an arm design would either stem from you under-gearing the motor or trying to hold the arm at a certain elevation. You can avoid the first issue with proper gearing. The latter can be avoided a number of ways. Balancing the arm would work. Using a transmission that doesn't backdrive easily, such as one incorporating anti-backdrive pins (DeWalt drill transmissions) or worm gears, would also work. A ratcheting joint could also do the trick, though you'd need to figure out a way to release the pawl in order to lower the arm. Or you could simply operate the arm to avoid the situation in the first place.