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Old Apr 08, 2012, 05:55 PM
Earthbound Skyhound
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United States, NC, Richlands
Joined Jun 2011
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Hi all;
I hope this isn't too off-topic, but I've spent near 2 hours searching without much success so, desperate times...yada yada.

Quite simply, I'm looking for some good simple plans to build an effective prop/motor (electric only) test stand of my own, using Eagle Tree data logging for recording performance. I've seen a few pictures & videos, but nothing I'd consider definitive. Oh and, I certainly am not considering being a competitor of our good 'Dr. Kiwi', by any means! I'm just a tinkerer, and love doing this kind of 'stuff'.

One concern I have - I'd like a good efficient but simple-to-make 'Universal' motor mounting method, if that sort of thing is feasible. Something that wouldn't require re-building the stand or changing mounts every time you turn around. My shortcoming in this regard is I haven't handled enough RC motors to know the various mounting methods I'll need to encompass.

And one further question. I'll be using a digital gram platform scale (the Harbor Freight Pittsburgh unit - I've seen used in several apps) and I've run some crude, hand-held tests with. Under input pressure, the readout is all over the place. I've set up a video-cam on a tripod next to the scale; after test run play it back and TRY to guesstimate an approximate average reading.....but am far from satisfied with this as a 'scientific' methodology. Any suggestions for obtaining a more accurate reading are VERY welcome, and I'd much prefer to leave the video part out of the process as exceedingly cumbersome!

Thanks a mlllion guys -- and again, hope this isn't too OT but the thread doesn't seem to be very busy lately anyway.
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Old Apr 08, 2012, 06:06 PM
just Some Useless Geek
Chicagoland
Joined Oct 2008
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One thing I can suggest for starters is to use a minimal test setup that puts the motor/prop directly on top of the scale in a pusher configuration. suspend the motor's wires in the least intrusive manner. Tare the scale.

As long as the sum of the motor mass and the thrust produced by spinning the prop isn't enough to overflow the scale you'll get direct thrust readings. You need to make sure the motor doesn't torque off the scale platform, yada yada, but I could see that working fairly well. I haven't tried this myself.

I've been playing with this idea for some time now and I'd like to see if I can get some decent readings off of my el cheapo Harbor Freight scales. I have a couple that report up to 500 grams and one that goes 5 keys. If the motor mount has some spongy or tacky stuff on the bottom side that should prevent it from moving around too much on the scale platform, so maybe this idea will work.
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Old Apr 08, 2012, 06:18 PM
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Quote:
Originally Posted by StarHopper44 View Post
...Quite simply, I'm looking for some good simple plans to build an effective prop/motor (electric only) test stand of my own...
Check this out:

http://www.wattflyer.com/forums/showthread.php?t=59325
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Old Apr 08, 2012, 06:23 PM
Earthbound Skyhound
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United States, NC, Richlands
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Quote:
Originally Posted by A Useless Geek View Post
One thing I can suggest for starters is to use a minimal test setup that puts the motor/prop directly on top of the scale in a pusher configuration. suspend the motor's wires in the least intrusive manner. Tare the scale. ...
The taring should go without saying, but that arrangement (pusher, directly[?] atop) I think would cause air intake problems (restricted), as opposed to tractor, causing ground effect lifting. I'd planned on going with the 'L' bracket with equalized legs method but, not sure of Dr. K's new configuration vis-a-vis the 'vertical' beam & what it entails -- which contributed to my asking here.

Thanks!
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Old Apr 08, 2012, 10:15 PM
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Chattanooga, Tennessee, United States
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I've been very pleased with the performance of my Ohaus Digital CS2000 Scale (though my 5000g unit died from some electronic failure). In my experience, vertical arrangements are inaccurate, and more importantly, with horizontal prop blades spinning in front of one's face, inherently far too dangerous.

My pusher prop arrangement has proven to be easy to use, reliable, safe, and accurate.... and in its present construction good for 400W or more. Obviously if you are testing 500W+ motors, props larger than 14", or monster EDFs... then you need a different design.

With just three or four types of mount I can accommodate virtually every type of motor.....and switching from one mount to another only entails undoing two mounting bolts!

http://www.rcgroups.com/forums/showt...t=thrust+stand
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Old Apr 09, 2012, 04:34 AM
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Antony (France)
Joined Sep 2003
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Quote:
Originally Posted by StarHopper44 View Post
Hi all;
I hope this isn't too off-topic, but I've spent near 2 hours searching without much success so, desperate times...yada yada.

Quite simply, I'm looking for some good simple plans to build an effective prop/motor (electric only) test stand of my own, using Eagle Tree data logging for recording performance. I've seen a few pictures & videos, but nothing I'd consider definitive. Oh and, I certainly am not considering being a competitor of our good 'Dr. Kiwi', by any means! I'm just a tinkerer, and love doing this kind of 'stuff'.

One concern I have - I'd like a good efficient but simple-to-make 'Universal' motor mounting method, if that sort of thing is feasible. Something that wouldn't require re-building the stand or changing mounts every time you turn around. My shortcoming in this regard is I haven't handled enough RC motors to know the various mounting methods I'll need to encompass.

And one further question. I'll be using a digital gram platform scale (the Harbor Freight Pittsburgh unit - I've seen used in several apps) and I've run some crude, hand-held tests with. Under input pressure, the readout is all over the place. I've set up a video-cam on a tripod next to the scale; after test run play it back and TRY to guesstimate an approximate average reading.....but am far from satisfied with this as a 'scientific' methodology. Any suggestions for obtaining a more accurate reading are VERY welcome, and I'd much prefer to leave the video part out of the process as exceedingly cumbersome!

Thanks a mlllion guys -- and again, hope this isn't too OT but the thread doesn't seem to be very busy lately anyway.
Hi
Here are some pictures of my mount
Two vertical M8 rods
Two tubes 8mm with wings
Several glass fiber plates for different patterns
Pivots are Igus polymer rings
Medusa weight scale
Louis
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Old Apr 09, 2012, 07:53 AM
homo ludens modellisticus
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The Netherlands, GE, Nijmegen
Joined Feb 2001
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Several test stand designs, a compilation, from very simple to very elaborate/$$$
http://www.rcgroups.com/forums/showt...ght=test+stand


Vriendelijke groeten Ron
diy motor tipsDrive Calculator
diy motor groupCumulus MFC
• Get a life ... get a Watt-meter!!! •
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Old Apr 09, 2012, 10:01 AM
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Thanks all - excellent references I can work from there.
FWIW, my plans (& intentions) are to build around a roofer's square -- pictured below in case you're not familiar with what they're called, tho I know everyone's seen one. Inexpensive, easily obtained, and they way they're made, plenty rigid so shouldn't undergo any in-test flexing or warping, and the flange along one leg should help accommodate a motor mounting platform. Already have two in fact - I might parallel stack them to accommodate fixturing....still thinking out the details.

And Dr. K -- I'll be staying fairly small on testing - maybe 'mid size' at best with few ultra-high performance testing, so size & huge props won't likely be an issue. This'll be more for motors I'd be flying, and I'm low-budget. (spelled 'p-o-o-r' 'm-a-n')

Haven't had a chance to read the links posted....is the problem with getting good scale readings covered in there?

Here's the 'heart' of my plans:
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Old Apr 09, 2012, 11:26 AM
just Some Useless Geek
Chicagoland
Joined Oct 2008
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Quote:
Originally Posted by StarHopper44 View Post
...that arrangement (pusher, directly[?] atop) I think would cause air intake problems (restricted), as opposed to tractor, causing ground effect lifting.
I would hope to offset the motor mount upwards a little to give the prop a chance to breath. If the scale is on top of some sort of pillar (doesn't need to be very tall) and the mounted motor is atop of that (doesn't need to be raised by much) then there shouldn't be much restriction to the flow of air the prop can draw. Hopefully.
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Old Apr 09, 2012, 12:02 PM
Earthbound Skyhound
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United States, NC, Richlands
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Quote:
Originally Posted by Ron van Sommeren View Post
Several test stand designs, a compilation, from very simple to very elaborate/$$$
http://www.rcgroups.com/forums/showt...ght=test+stand
Thanx especially for that wormhole to Cornucopialand, Ron!
It's sort've amazing I didn't find any of those in all my searching - not even a reference to any one of 'em, thru the 'Advanced Search' tool here. Which I did, honest! No, really!! Maybe wasn't "holding my mouth right", or somethin'.
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Old Apr 09, 2012, 01:38 PM
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Here's a few of my mounting arrangements for testing different styles of motor:
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Last edited by Dr Kiwi; Apr 09, 2012 at 01:51 PM.
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Old Apr 09, 2012, 02:41 PM
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Good Grief Dr. K! When will you be publishing a build-blog article on the cabinet you built to house all those mounts??

And I was entertaining thoughts of a 'u' shaped half-slice of ABS conduit along with a radiator hose clamp. And/or rubber bands. Lo-t-t-ts of rubber bands. *sigh* I should thank providence there won't be much variety (ie, all that many) motors being tested here, I guess.
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Old Apr 10, 2012, 05:21 PM
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Other than the Aeronaut beam mount which I need for larger motors, all these are basically a ply plate with a 10mmx10mm stick glued (and screwed) to it! For most motors I use various AXI (16mm centers) or Cobri (19mm centers) alloy stick mounts, and a variety of discs to accommodate X-mounted motors.

The EDF mounts are the most challenging.
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Old Apr 11, 2012, 01:58 PM
Cumulus Altimus
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KELLER TEXAS
Joined Feb 2002
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is there a calc that also carry's hyperion motors?folding props?
thanks
ben
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Old Apr 12, 2012, 06:27 AM
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I've wondered "things" about folding props myself. Like efficiency &c. I mounted some CF blades on a warmliner in exact same size & pitch; difference was like night & day!
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