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Tuesday, February 5, 2013

Motors for Haunt and Halloween Props

There has been a lot of talk about the shortage of electric motors for Halloween prop building since the supply of surplus wiper motors and vent motors has dried up.   For the January meeting of CalHaunts I put together the equivalent of a 10th grade science project to demonstrate some potential haunt prop motors.   After visiting all the usual sources of surplus parts (That post is coming) I gathered what I thought were the best candidates for electric motors to build into props.  Most are 12 volts and less than $20 dollars for the motor.

The benchmark project in mind was the classic Flying Crank Ghost.  Motors needed to be strong enough and slow enough to replace the $50 motor specified by phantasmechanics.

What we ended up with was 7 motors that seem to be good prop building candidates.  Six motors are 12 volts and one is 110 AC.  To demonstrate the available torque I modified each motor to accept a 6" crank arm and tested it using an 8 once weight.

To deal with motors with high RPM, I demonstrated two inexpensive PWM modules available from ebay.com to control motor speed.  (More information on Pulse Width Modulation controllers in a later post.)

Over the next few days I'll do a more detailed post on each motor.

Note:  Thanks to Dennis Griesser (of Wolfstone fame) for these photos and all the closeup photos of motors to come.  (Dennis - Could you please Photoshop away 20 pounds from me next time?)

Monday, February 4, 2013

PWM Controller for DC Motors

PWM DC Motor Speed Control 

Seller: t-mall
Price $9.99 including shipping from China
Search for: PWM DC Motor Speed Control 6A AMP 12-24V VOLT 13KHZ Controller Switch

For our purposes, a Pulse Width Modulation (PWM) controller allows you to dial in the speed of a DC motor.  This allows you slow down a high speed motor such as a wiper motor to power props at a lower speed.  For a technical explanation see the Wikipedia article (http://en.wikipedia.org/wiki/Pulse-width_modulation)   Basically you can slow down a motor without losing much torque or wasting power using a controller like this.
I just tested this PWM unit as was very please with results.   Wiring was a snap and this unit did not cause the motor to buzz annoyingly.  There was a high pitched noise on one of the motors tested but the volume was low.
Adding the module is very easy.   If you go with the usual convention that a motor is wired with the red (+) wire to the motor and the black (-) wire to ground of the motor.  Red to red, Black to black.  The PWM module adds one wire to the mix.   Now you connect the red motor to the red power wire and the red wire from the module.  Essentially you wire the red wire to both units.   The negative wire from the power source goes to the black wire of the module.   Now the blue wire from the module connects to the "-"  connection of the motor.   Actually the picture on the module does a better job explaining what to do...
At ten bucks adding a PWM module makes your prop motor much more controllable, allowing you do dial in the speed of your prop exactly.
I've tried some cheaper, 7 or 8 dollar controllers that cause a loud buzzing noise in the motor.   This one does not.   I will be testing several other controllers in the near future.

Thursday, January 31, 2013

Motor Test 5

AllElectronics.com DCM-351

Relatively powerful, low-current DC motor and gearbox with a 4.9" diameter plastic (nylon?) turntable with a rubber o-ring circumference that could be used to drive another wheel. Turntable can be removed from motor and rubber ring on turntable can be removed as well. Motor gearbox has a 5/16" diameter shaft that is flatted and splined.

  • 45RPM @ 24 Vdc, 60mA - operates at 12Vdc at 1/2 speed.
  • Drive motor - Mabuchi RS-380SH. 1.1" diameter x 1.67".
  • Gearbox - Molon #CHM-2435-1. 2.75" x 3.00" x 0.57" Threaded mounting holes in four corners. 5/16" diameter shaft, flatted and splined.
Price for one - $9.75 Shipping for 1 - 7.00
Price for ten - $9.75 each Shipping for 10 - $7.00

Medium Torque
Seller has good shipping policy
Good price
Good customer service
Seems happy in low torque continuous use
Electrical connection are very easy to get to.
This motor had enough torque at 12 volts to spin the 8oz test weight at high rpm with some strain.
Comes with 4.9" plastic wheel.  This should provide lots of easy way to drive loads.
Easy to mount using 4 existing through holes in the gearbox.

CONs -
A bit noisy under load
RPM a bit high at rated 24 volts
Output shaft a bit short

Modifications -
I removed the wheel from the drive shaft.  I did this to demonstrate how easy it was to adapt the ouput shaft.  I used a U-bolt to attach the crank arm to the shaft.  For this test I ran the motor at 12 volts.  RPM at 12 volts is a bit high for a FCG but for a spider or other animation this motor at 12 volts should be a good choice.

The ideal solution would be to use a PWM module with this motor and 24 volts.  This will give you good torque over a wide RPM range.

Comments - I have not tried this yet, but repacking the gearbox with a heavy (wheel bearing) type grease should reduce the noise level.

Wednesday, January 30, 2013

Motor Test 4


Surplus Center #5-1754

New, permanent magnet, right angle gearmotor. Cast aluminum gear housing with steel motor frame. Hollow square thru-drive output shaft. Two bolt rubber isolation mount. Two pin male integral Packard power connection (female half of plug not available from Surplus Center).
• Speed 500 RPM no load
• Speed 250 RPM at rated torque
• Voltage 12 DC
• Amperage 16 Amps
• Torque 8.5 in-lbs
• Rotation Reversible
• Duty Intermittent
• Mount 3/8" dia. two bolt on 2.2"centers
• Hollow Thru-shaft 5/32" (4 mm)
• Size 5-1/4" x 3-1/8" x 2-1/2"
• Shpg. 3 lbs.

Price for one - $13.99 Shipping for 1 - $11.98
Price for ten - $13.99 each Shipping for 10 - $24.51
  • Quiet
  • High Torque
  • Compact
  • Good mounting points
  • Electrical connection is relatively easy to get to. Will accept slightly modified push on crimp connectors
  • This motor had enough torque to spin the 8oz test weight at high rpm without strain.
  • Shipping for a single unit is relatively expensive.
  • Designed for intermittent use - See my comments below
  • The output of this motor is via a square shaft or hollow shaft.
  • High current requirements - I can't believe the posted spec.
  • If you add a crank arm it can interfere with the electrical connections.
Modifications -
I cut away shroud over the electrical connection with a hacksaw.  Then it was easy to use spade connectors to wire the motor. 
I screwed/beat a 10-32 screw into the round half of the shaft and used Locktite hold it.  Then I cut off the head of the screw and ran a lock nut down the shaft.  I then tapped and threaded the crank arm the 10-32 shaft.
Comments -
While designed for intermittent use, I've left this motor running for hours under light load with no sign of heating up.  This motor requires at least 2 amps of current at 12 volts to run.

The metal of the OE shaft seems pretty hard and I was unable to thread the inside of the hollow shaft.
The high RPM of this motor means you'll probably need a PWM controller to reduce the speed.  Motor buzzes when PWM is used at low speed.

I really wanted this motor to be the new big thing.   It is going to take someone coming up with a better means of getting the output shaft connected to the prop than I've come up with.  The 2+ amp current requirement forces a bigger (more expensive) walwart or power source.

Still, in a group buy situation; this motor could easily power a flying crank ghost.  Figure $10 for the power supply, $16.50 for the motor, and $10 for the PWM controller, you get an easy to control prop motor for under $40

Unverified rumor has it that for larger orders you can contact them directly and they will work with you on the shipping cost.

Tuesday, January 29, 2013

Prop Motor Test Three

EBay.com Synchronous Motor


Try searching on ebay.com for "synchronous motor 110"  This will get you a number of similar motors at various RPMs


Shaft Diameter: 7m
Shaft Length: 15mm
Working Voltage: AC 100-127V
Frequency: ~50/60Hz
Power: 4W
Speed: 8R/MIN
Weight: 0.9kgs
Price for one - $4.80 Shipping for 1 - $3.60
Price for ten - $4.80 each Shipping for 10 - $35.10

Designed for continuous use
Electrical connection is very easy to get to.   Wire nuts will make the connections easy.
It is fairly easy to adapt an arm to the shaft arrangement.
Mounting is easy using the two exposed mounting tabs.

Shipping for a single unit is relatively expensive.
Medium to low torque - This motor did not have enough torque to spin the 8oz test weight on a 6 inch arm. At max load (almost half way toward vertical) the motor reversed direction.

Modifications -
The output shaft is a smooth shaft with a perpendicular hole in it. I used the hollow threaded rod sold in the lamp department of home improvement store and drill a hole through the all-thread to match the hole in the output shaft.  I filled the hollow center of the threaded rod with hot melt glue and press the rod over the shaft.   I added a cotter pin through the holes.  The rod arm is secured between two nuts purcahsed in the lamp department.  Five dollars will buy you enough parts to modify 4 motors.

Comments - This motor functions like a stripped down reindeer motor.   My method of adding to the output shaft may cause problems in applications where the shaf and the rod must be totally co-linear.  This motor looks like a perfect candidate for a simple haunted Ouiji board.