Drill motor change out question??

Posted by Dennis Hughes at 1/25/2001 7:01 AM EST

Other on team #27, Team Rush, from OSMTech Academy & MTA and TEXTRON Automotive.

Anyone have a good rule of thumb on when to change out a used drill motor? Meaning, how many hours or minutes of hard driving ( HOT motors ) can a motor take before efficiency begins to drop???

Posted by JVN at 1/25/2001 8:28 AM EST

Student on team #250, GE Dynamos - Capital District Robotics Team, from Shenendehowa High School and General Electric.

In Reply to: Drill motor change out question??
Posted by Dennis Hughes on 1/25/2001 7:01 AM EST:

: Anyone have a good rule of thumb on when to change out a used drill motor? Meaning, how many
hours or minutes of hard driving ( HOT motors ) can a motor take before efficiency begins to
drop???

Depends on what kind of conditions your running them under… Usually ours last about 45 minutes
before they get hot, after which we just stop the robot, let em cool for 20 minutes, then continue
testing.

We also weighted down a previous years robot with about 200 lbs. of weight and drove it
around/up the ramp. It only lasted about 20 minutes before it got REALLY hot. Those conditions
could never really be repeated in the competition.

Usually we don’t switch em out unless they get visibly slower/weaker (maybe once 3 years ago).
If you just give them a chance to cool, we found they don’t give you many problems. Gear boxes are
something completely different. Ever seen a liquid plasitc drill gearbox?
~John #250

Posted by Anton Abaya at 1/26/2001 8:51 AM EST

Coach on team #419, Rambots, from UMass Boston / BC High and NONE AT THE MOMENT! :(.

In Reply to: It varies…
Posted by JVN on 1/25/2001 8:28 AM EST:

: : Anyone have a good rule of thumb on when to change out a used drill motor? Meaning, how many
: hours or minutes of hard driving ( HOT motors ) can a motor take before efficiency begins to
: drop???

: Depends on what kind of conditions your running them under… Usually ours last about 45 minutes
: before they get hot, after which we just stop the robot, let em cool for 20 minutes, then continue
: testing.

: We also weighted down a previous years robot with about 200 lbs. of weight and drove it
: around/up the ramp. It only lasted about 20 minutes before it got REALLY hot. Those conditions
: could never really be repeated in the competition.

: Usually we don’t switch em out unless they get visibly slower/weaker (maybe once 3 years ago).
: If you just give them a chance to cool, we found they don’t give you many problems. Gear boxes are
: something completely different. Ever seen a liquid plasitc drill gearbox?
: ~John #250

although we never had problems last year because we made heatsinks that looked like wings, i was hoping to mount some muffin fans on them babies this year for the heck of it… will that solve the problem? or must i hide some liquid nitro in there somewhere?

-anton

Posted by Matt Leese at 1/26/2001 10:37 AM EST

Other on team #73, Tigerbolt, from Edison Technical HS and Alstom & Rochester Institute of Technology.

In Reply to: would muffin fans make the difference?
Posted by Anton Abaya on 1/26/2001 8:51 AM EST:

Muffin fans won’t SOLVE the problem. If you’re burning up lots of drills or gearboxes you’ve got a mechanical problem on your hands (remember it’s never the EE’s or CE’s fault ;). Installing Muffin fans will however help to cool the motors some. If the gearboxes are getting hot enough to melt the Muffin fan can’t put out enough air to cool them that much. However, if they’re heating up from general wear and tear than the Muffin fan can help a bit. So basically the Muffin fan can help but won’t solve your problem.

Matt

Posted by JVN at 1/26/2001 3:01 PM EST

Student on team #250, GE Dynamos - Capital District Robotics Team, from Shenendehowa High School and General Electric.

In Reply to: would muffin fans make the difference?
Posted by Anton Abaya on 1/26/2001 8:51 AM EST:

you really shouldn’t have a problem…although your heatsinks and fans might help…
if you really get desperate, and the robot starts melting itself every match…
just pop those motors out and pack em in ice…

~John

Posted by Matt Leese at 1/26/2001 9:27 PM EST

Other on team #73, Tigerbolt, from Edison Technical HS and Alstom & Rochester Institute of Technology.

In Reply to: Re: would muffin fans make the difference?
Posted by JVN on 1/26/2001 3:01 PM EST:

You’d want to be very carefully putting the motors into ice. The drastic temperature change can cause thermal shock which is a very bad thing for the motors.

Matt

Posted by Joe Johnson at 1/26/2001 9:52 PM EST

Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.

In Reply to: Re: would muffin fans make the difference?
Posted by Matt Leese on 1/26/2001 9:27 PM EST:

For years we have been using Freez-It from Chemtronics.

The intended purpose of the stuff is for “Anti-Static”
uses, but as a practical matter, it is more often used
as “Cool in can!”

The stuff is basically a residue free liquid that boils
at room temp and pressure. It comes out of the can as
a liquid but quickly evaporates.

As any Freshman Thermo student can tell you, the heat
to boil the liquid has to come from somewhere and in
our case, quite often it comes form wasted electrically
energy that has not gone to do useful stuff like spin
our wheels or lift our arms but rather has been
converted to thermal energy in the windings and
housings of our motors.

BOTTOM LINE: We thermal shock the beejeebers out of our
motors with no particular bad outcome as far as we have
been able to observe over 5 years.

I know that this is a controversial issue, but I call
'em how I see 'em.

Others will doubtless have differing opinions.

Joe J.

Posted by Matt Leese at 1/25/2001 10:18 AM EST

Other on team #73, Tigerbolt, from Edison Technical HS and Alstom & Rochester Institute of Technology.

In Reply to: Drill motor change out question??
Posted by Dennis Hughes on 1/25/2001 7:01 AM EST:

If there’s a well designed drive train than the drill motors really shouldn’t need to be changed. The only time drill motors start dieing is when too much load is put on them (either because of a bad gearing ratio or something like a side load). Then they can die rather quickly.

Matt

Posted by Joe Johnson at 1/25/2001 1:25 PM EST

Engineer on team #47, Chief Delphi, from Pontiac Central High School and Delphi Automotive Systems.

In Reply to: Drill motor change out question??
Posted by Dennis Hughes on 1/25/2001 7:01 AM EST:

We never change the motors of our machine once they are running just as a matter of course.

One year we really missed the ratio and we underestimated the amount of pushing we would have to do (the puck year!). That year, we used the burnt insulation test.

If the motor smelled like that pukey burnt laquer smell, we changed them out. Typically that would be after a regional, we never had any trouble in practice no matter how long we practiced.

By the way, for those who are driving with the Fisher Price Motors, we used them that year as well. You will be interested to know that these motors come with a built in “I have been over heated” indicator… …The fans melt off the armature shaft! Really. All that is left is a ring of fan blades that do not spin when the motor spins.

Low temps to us all!

Joe J.

P.S. I have never seen the fans melt off the drill motors by the way, no matter how badly we toasted the windings. JJ

Posted by Al Skierkiewicz at 1/28/2001 3:05 PM EST

Engineer on team #111, Wildstang, from Wheeling High & Rolling Meadows High and Motorola.

In Reply to: Drill motor change out question??
Posted by Dennis Hughes on 1/25/2001 7:01 AM EST:

Joe & et. all,
The fan on the Fisher Price Motor melted off the armature to us in Florida last year. Luckily it makes an unusual noise and one of our students persisted that something was wrong. He checked until he found it and sure enough the fan was laying down in one end. (we used this motor on the conveyor assy.) The motor had survived for two regionals and a day of nationals. There was very little smell until we opened it up.
The reality is the fan only is effective when the motor is running near design RPM but when under load it just cannot cool effectively. Both regionals were in the north in March as opposed to Florida in April. A visual inspection after each match is now part of our routine.
Fans on drive motors are always considered during practice and test.
Al