Submitted by disneytoy on Sat, 10/02/2010 - 21:26
Posted in
Greetings!
i came to this forum not from a timelapse perspective but a more real time application for DSLRs. I can't afford the Kessler Cineslider with motor and controller. So i was familiar with the Arduino and what can easily be achieved. That led my to some amazing TL films. And now I "Need" to try this myself!
After some time researching different "dolly" systems, and lots of DIY projects which end up not giving enough details on hardware, motors etc.
Luckily, I have a surplus metal place up the street. I can buy Aluminum rods, extrusions, blocks for $2.15 LB. For my first attempt, I happen to already have a nice, rigid 5' aluminum extrusion I'd like to use.
I like Jay's design, and have watched his videos. I ordered I believe the same motor he uses in the Dynamic Perception Timelapse Dolly Stage Zero, a Dayton 8.75 RPM Gearmotor from Grainger. Not having much experience yet, I might as well follow in the footsteps of the expert:-)
So, there are a lot of surplus motors out there. in San Diego, we have several electronic liquidators. So I would appreciate some guidance, and affirmation if I am correct.
In the Dayton motor example, we have 8.75RPM, It is 1 amp power and generates 656 oz.in.
It clearly works in this application. Now if I go looking for other motors, for future projects, I'm guessing in the 8-10 RPM range is good. Faster is fine if I ratio it down with gears or pulley.
Is the key the 656 oz. in.? Is this the amount of power we need to move a dolly?
I have seen some motors that have the right RPMS, but don't specify the torque. But show say 0.10 amps at 12v. Can I conclude that this motor would be way underpowered for our application? Being 1/10th the amperage of the Dayton? Is that a fair appraisal?
Would as a rule of thumb when digging through a box of motors pay more attention to the AMPS as a guide? 4 amps would be overkill, while a 500 milliamp DC motor could not pull the dolly properly?
Is there a similar ballpark spec to look for regarding a stepper? I think my second project, a pan head would be a stepper motor.
While looking at the Kessler system, I noticed they offer 4 motors, described as 1:100, 1:200, 1:500 and a 1:1000 gear ratio. The 100 being for realtime moves, and the 500 and 1000 for TL. Am I confused in not understanding that since they don't specify the original RPMs of the motor, how can we compare thier 1:500 motor to another 1:500 geared motor? I did figure out which motor they sell in the elektraDRIVE 500 Series Motor Pod, can't find a supplier in the US but several sellers in the UK, it is a 940D SERIES PLANETRY (EPICYCLIC) METAL GEARBOX, 940D5161 (4.5v - 15v) RATIO 516:1, 21 RPM @ 12v 0.837 amps, I tried to calculate the torque but found 3.3nM???
940D SERIES PLANETRY (EPICYCLIC) METAL GEARBOX (RE 385 MOTOR)
So am I close now in understanding in the DC arena that something close to 1 amp will do the trick? And as attractive as some other motors may seem, a 200 milliamp motor is not going to work?
Sorry to go on so long. My head is throbbing trying to make sure I'm getting adequate hardware, and not wasting money.
Peace out!
And to Jay, keep up the great work! I'm an example of someone who crossed you path, got excited by your passion, and now I'm taking my own timelapse journey, soon at least:-)
Max
San Diego
So my hope is to build a test (inexpensive) rig for timelapse, then pursue a faster motor for regular shots. Maybe a pan head.
Max, Well, I'm not sure
Max,
Well, I'm not sure that's exactly the motor they use - as, well, that looks like any other DC motor with a gearbox *grin* I've got a bunch that look like that, but no idea what manufacturer/model they use, but that could be it for all I know!
Amperage is not, generally, the definition of power in and of its self. You can have a 100mA motor that can move a LOT of load, but at very low speeds due to a very low gearing. For example, there's a 0.45RPM gear motor made by Grainger that uses 100mA, but can move much more load than the 8.75RPM motor that uses 1A of power.
Generally, you can control two of these factors:
Max Speed, Torque, Power Draw, Cost
If you choose a high Max Speed, and a High Torque, you'll get high current draw, or high cost. If you choose low cost and low power draw, you'll sacrifice either speed or torque.
The 8.75RPM motor was chosen because it walked down the middle of the road, and it had a good speed range for timelapse. It came in at 1A power draw (at max load - DC brushed motors are always rated at max load on power draw, if you try to move more than they are rated at, they exceed max load and stall, possibly damaging the motor). They use less current with less load.
Of course, these motors have other issues at their price point, like they're louder than we'd like, but they get the job done at the right price, and many a successful rig has been built around them. For the purpose of noise and speed, they may not be right for a real-time application. (8.75 RPM with a 3" circumference pulley nets you a max speed of 26.25 inches per minute!)
!chris
That's good info. So the
That's good info. So the torque is not necessarily directly related to the AMPS. But a mix of speed and Amps.
Have you seen other 516:1 motors? in my searching, I camer up with that motor. it is the gear ration on the Kessler motor, the 500 series.
Can you describe the pluses and minus of DC vs. Stepper? i know how they are different. How the controllers are different. That Steppers are more accurate? Like in CNC applications.
Is there a benefit od one over the other in regards to range of speeds? I'm guessing that 8.7 RPM DC motor was chosen for Jay's dolly is cost?
Well, I'm excited. I will start off in you guy's footsteps. Then once I get a hanfg of this, there are a lot of motors to try.
thanks
again :-)
Max, Check out the article I
Max,
Check out the article I wrote on different motor types =) http://openmoco.org/node/179 I think that should answer some of your questions. The motor was chosen for our dolly (Jay and I run Dynamic Perception =) based on attempting to put together the lowest cost system for timelapse, with appropriate payload, power, and utility requirements. If we were targeting all kinds of video moco in the first release, we would've gone the stepper route, and had a higher price. We believe that all things are incremental, walking before running, and starting with a low-cost system that handle 80% of the needs at a low cost is the right way to go. We'll work on the other 20% for those that want to pay more =)
!chris