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R2-D2 Goes To Dover Comicon
#1
So, 

My first foray into the public was at Dover Comicon.  Her are some pics and lessons learned.

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After 20 minutes of "dancing" around R2 stopped moving properly.  When I got him home I found this damage.

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The temps on the motor melted the drive wheel.  Booo.  I am going to reprint in Nylon, Hopefully, this will solve the melting problem.  I'll keep ya'll updated.  


Eebel


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#2
looks great, your droid is amazing.
did you have a washer between your drive wheel by any chance?
was that printed in PLA? or ABS?
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#3
wow, that looks amazing. I wouldn't believe that was 3d printed looking at the pictures if it wasnt on this site.
I'm new to the site but I shall search for your build log.
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#4
It was printed in PETG. I did not use a washer. The only metal is the nut and bolt to attach it to the drive shaft.

Eebel
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#5
All electric motors will generate heat.
The insulation used in the windings of the motors are typically rated to 115-130 degree C.
Most electric motors used in industry have cooling fins on the outer frame of the motor and incorporate a fan to blow air over the fins to provide the required cooling.
The DC motors we are using don't have the cooling fins of a circulation fan.
This leaves us with the problem of either using materiales that have a very high melting point or provide an alternate cooling method for the motor.
PLA becomes soft at temperatures above 60 degree C, so its not going to last (Bummer looks like I will be reprinting that part)

If we go back to the build instructions, Michael does say it hasn't been tested under load. He printed in using Nylon, but then makes comment the for strength the ABS should be fine.
From a strength perspective, Michael is correct, however, Nylon may be the better choice for the temperature issue.
We also have the issue of not having any cooling for the motor, the heat has to go somewhere.
The motor sticks out of the back of the frame a bit, should we add some heat sinks as used by our 3D printers stepper driver chips and a small 30mm fan to help cool the motors when the start to get hot?

Just some food for thought.

Ohhh, and a great looking build.
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#6
(08-19-2018, 09:00 PM)Cyber_One Wrote: All electric motors will generate heat.
The insulation used in the windings of the motors are typically rated to 115-130 degree C.
Most electric motors used in industry have cooling fins on the outer frame of the motor and incorporate a fan to blow air over the fins to provide the required cooling.
The DC motors we are using don't have the cooling fins of a circulation fan.
This leaves us with the problem of either using materiales that have a very high melting point or provide an alternate cooling method for the motor.
PLA becomes soft at temperatures above 60 degree C, so its not going to last (Bummer looks like I will be reprinting that part)

If we go back to the build instructions, Michael does say it hasn't been tested under load.  He printed in using Nylon, but then makes comment the for strength the ABS should be fine.
From a strength perspective, Michael is correct, however, Nylon may be the better choice for the temperature issue.
We also have the issue of not having any cooling for the motor, the heat has to go somewhere.
The motor sticks out of the back of the frame a bit, should we add some heat sinks as used by our 3D printers stepper driver chips and a small 30mm fan to help cool the motors when the start to get hot?

Just some food for thought.

Ohhh, and a great looking build.

Thanks for the input and the compliment!

I was going to attack the problem three way. 

1. Use nylon parts.  I am using the alternate single drive belt models.  It prints very nicely if you stack the halves together and use supports.  This eliminates the need to try and glue the pieces later.

2. I am pulling SLA batteries out and putting in LiPos. I’m guessing this will be a 25-30 pound reduction in weight.  Which is about the same percentage in reduction in his total weight.  So, less work for the motors.

3. A cooling strategy.  I think it gets too toasty with the motors in the battery boxes.  I had not thought of adding fins. So thank you for that idea.  

Eebel
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#7
OK, so I ordered some 24V 50mm fans.  Since my Motors are 24V, I can tap off of my 24V power and run the fans continually when the 24V system is powered.  I am going to redesign the battery boxes with vent slots to allow for airflow.  My current plan is to put slits behind the battery straps for intake and mount the fan in the top rear with slots for output of hot air.  This pains me as the "real" R2 does not have visible cooling vents.  But physics trumps canon, I guess.

I reprinted the drive gear in nylon.  Since my Nylon mounts did not melt.  I am hoping this will be sturdy enough to survive.



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Lastly, I have built cooling fins.  However, I am not any kind of engineer and have no idea if what I did was nearly cosmetic or if it will have a thermodynamic effect.  I know it will be better than nothing.  But I suspect that the cooling fan will have more impact than the fins.  Does anyone have any insight on the physics here?

To build the fins, I made a paper template. I installed the clamp, then put the boot on first.  


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Then I cut the metal 22 gauge sheet metal and bent it.

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#8
could always get some pc heatsinks and just bend then around the outside and then glue then on.
https://www.ebay.com.au/itm/Aluminum-Hea...SwCtJaLgCf
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#9
My PLA motor gear died the moment I tried to first drive with them. Switched to nylon and they've been trucking along for nearly a year now.
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#10
(08-21-2018, 01:12 AM)jonhaag Wrote: My PLA motor gear died the moment I tried to first drive with them. Switched to nylon and they've been trucking along for nearly a year now.

Wow, that's good to know!

Eebel
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