How much can the window assembly lift?

Posted by nuts4first.

Engineer on team #340, GRR - Greater Rochester Robotics, from Churchville-Chili and Nortel Networks.

Posted on 2/2/2000 5:13 PM MST

I’m at home so I can’t test this but…

How much can one window track & motor assembly lift in raw weight. That is, if you attach the assembly to a stable object how much can it lift off the ground?

Thanks,
-Nuts4first

Posted by Joe Johnson.   [PICTURE: SAME | NEW | HELP]

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

Posted on 2/2/2000 6:06 PM MST

In Reply to: How much can the window assembly lift? posted by nuts4first on 2/2/2000 5:13 PM MST:

Window lift motor is about an 12 N-m motor (stall torque).

The tape drive pinion is about 1.5 inches in diameter, .75 inches in diameter (sorry, that is 0.019 meters in radius).

At that radius, it will take 12/.019 Newtons to stop the motor (630 Newtons = 141 lbs).

But…

The tape drive is not 100% efficient so you have to take that into account.

I would guess that in tension, the window lift units should be about 70% efficient.

So…

How about 100 lbs?

Close enough to what I remember.

The units put out less when the tape is in compression. Perhaps 20 lbs less, especially if you bend the channel.

I hope this helps.

Joe J.

Posted by Thomas A. Frank.

Engineer on team #121, The Islanders/Rhode Warrior, from Middletown (RI) High School and Naval Undersea Warfare Center.

Posted on 2/3/2000 2:20 PM MST

In Reply to: Figure it out… posted by Joe Johnson on 2/2/2000 6:06 PM MST:

: How about 100 lbs?

Well, back in our Aquatread days, two of them in parallel attached to a small piece of angle (the infamous flipper, now banned like many of our better ideas, such as velcro on the wheels…) had no difficulty in lifting a robot off the floor…

Tom Frank

Posted by Daniel.

Coach on team #483, BORG, from Berkeley High School and NASA Ames & UC Berkeley.

Posted on 2/2/2000 6:17 PM MST

In Reply to: How much can the window assembly lift? posted by nuts4first on 2/2/2000 5:13 PM MST:

My team attached two window motors to a piece of plywood. I hung off as it lifted me off the ground to the pole. I weigh more than your robot will.

Posted by Tom Wible.   [PICTURE: SAME | NEW | HELP]

Coach on team #131, chaos, from central high school manchester and osram-sylvania.

Posted on 2/2/2000 7:08 PM MST

In Reply to: How much can the window assembly lift? posted by nuts4first on 2/2/2000 5:13 PM MST:

The window track can lift about 30 pounds straight up. No leverage, just weight.

Tom Wible
Team #131
C.H.A.O.S.

Posted by Joe Johnson.   [PICTURE: SAME | NEW | HELP]

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

Posted on 2/3/2000 6:03 PM MST

In Reply to: Re: How much can the window assembly lift? posted by Tom Wible on 2/2/2000 7:08 PM MST:

Tom,

Something seems wrong about that number of about 30 lbs.

Did you have the track lubed (inside and out)?

Tubes of lithium grease are almost within hands reach during build time.

Have others tried this lifting experiment?

We don’t use the tracks (most years) so I don’t have a reference.

Do tell.

Joe J.

Posted by Tom Wible.   [PICTURE: SAME | NEW | HELP]

Coach on team #131, chaos, from central high school manchester and osram-sylvania.

Posted on 2/3/2000 6:24 PM MST

In Reply to: Something seems wrong… posted by Joe Johnson on 2/3/2000 6:03 PM MST:

Last year we used two window track drives to elevate our robot. We did an experiment to see how much lifting power one of the window set ups had. We put the set up in a vise and tied weights to the plastic track. The motor was able to lift about 30 pounds of steel plate. If we added weight, it bogged. From that we gave our lifting mechanism a 2-1 leverage using the track drives, this was able to raise our robot up about 7 inches in 2-3 seconds. If you have any footage of the Nationals, you can see our chassis elevation system at work in the finals when we went up against team 88. After tearing into one of the window motors after last, year we found that the brushes do not make good contact with the commutator. This may account for the power output not being optimal. The brushes really need to be seated properly to get good current transfer to the armature. Of course it is not recommended that teams open up these motors.
The seat and window motors are two of the motors in the kit which have symetrical brush assemblies. Therefore they run equally well forward and reverse. This of course means that they are not optimized for forward operation and thier output suffers. The output from the reductions will be different in either direction, due to the performance characteristics of the worm drives. (I think!)

Tom Wible
Team #131

Posted by Michael Betts.

Engineer on team #177, Bobcat Robotics, from South Windsor High School and International Fuel Cells.

Posted on 2/4/2000 10:28 AM MST

In Reply to: Re: Something seems wrong… posted by Tom Wible on 2/3/2000 6:24 PM MST:

: Last year we used two window track drives to elevate our robot. We did an experiment to see how much lifting power one of the window set ups had. We put the set up in a vise and tied weights to the plastic track. The motor was able to lift about 30 pounds of steel plate. If we added weight, it bogged.

: Tom Wible
: Team #131

Team 177 did a similar experiment with similar results (30 lbs max for reliable operation) in the first year that we used the window motors (Toroid Terror???). My recollection of the details may be a little fuzzy as the test was performed by a Physics teacher and two students who have all ‘moved on’ since then. As I recall, above 30 pounds the motor got hot and performance degraded.

We have used 30 pounds as a design criteria ever since. It may be a tad conservative but we have had few problems over the years.

Mike

Posted by Greg Mills.

Engineer on team #16, Baxter Bomb Squad, from Mountain Home and Baxter Healthcare.

Posted on 2/4/2000 6:22 AM MST

In Reply to: Something seems wrong… posted by Joe Johnson on 2/3/2000 6:03 PM MST:

:
We mounted one on an overhead bridge and with a fresh battery could lift fifty pounds straght up without straining. I guess your definition of overloading would determine where to stop but 100 pounds is a significant strain. (We did this with an old unit.) So we feel that one can safely lift 75-80 lbs.

Posted by Charlie Affel.

Other on team #487, SPARTANS, from Springfield HS, Springfiled MontCo, PA and PEW Charitable Trust, Rohm & Haas, Yeager Industries.

Posted on 2/8/2000 7:17 AM MST

In Reply to: Re: How much can the window assembly lift? posted by Tom Wible on 2/2/2000 7:08 PM MST:

We made the experiment and got the following:
40#, 3.75 secs to move one foot @ less than 10 amps
45#, 4.5 secs for 1 foot @ less than 10 amps.
This was all that we felt we needed to operate the bottom of our scissors and fast enough so that we can double the mechanical advantage if needed