How do YOU measure thrust?

JWarren · Oct 14, 2004, 06:06 PM

Hello all!

After giving much thought to measuring thrust on an electric setup and seeing many posts, scattered all over this forum as well as others. I wanted to get some input from the many forum members who have given their time and knowledge to help others and to also say thanks for all that help!

I am not looking for anything dealing with software here. I am looking for those devices which are used in actual testing by using the motor/prop setup and some type of guage to measure the thrust.

Myself, I have used the software programs to calculate intial setups before purchase and they have helped with a ballpark motor and prop setup for a particular plane. But generally, I find the motor/prop selection to be off in some way and another motor/prop selection was needed.

So, if you have a homemade device or one you have bought, which you use to measure thrust in real world testing, I would like to see a few examples. I am not really sure how to go about making one which will give an acurate result.

I have seen alot of debates on just how to make one, which is correct, I sure don't want see any of that here. So, please, NO fellow R/C'er bashing!

Thanks in advance for your post.

P.S. Pictures please! Some of the photos I have seen in the threads are outstanding by the way!

John

phat23 · Oct 14, 2004, 06:23 PM

http://www.rcgroups.com/forums/showt...=271490&page=1

See post #6. Made this setup in less than an hour with scrap wood and a cheap kitchen scale.

lensrc · Oct 14, 2004, 06:24 PM

Here is a pic of my thrust test bed. Tests are done in pusher mode. Works fine for brushless motors. If I need to do a tractor test I have a lever setup that I use with the same scale. I dont have a pic of it.

Len

Tom Frank · Oct 14, 2004, 06:36 PM

Here's mine:

http://www.rcgroups.com/forums/showthread.php?t=252722

Works great. The scale measures in either grams or pounds/ounces (to the nearest 1/10th oz). It doubles as a prop balancing rig as well.

crashingagain · Oct 14, 2004, 07:02 PM

Heres mine

Bill Mixon · Oct 14, 2004, 08:39 PM

Quote:

How do you measure thrust

I strap enough spare junk to the plane until it will only hover at full power, then weight the plane.

I have done that but seriously...
I use a long board suitable for the power system. (A 1X4 or 2X4 for bigger motors) The power system is mounted all the way at one end of the board. Next I place the board on something that it can pivot on top of. Then power up while sliding the board to find the "neutral" point. Power down and take a weight reading at the shaft.
Not perfect but it's quick and works.

Dr Kiwi · Oct 14, 2004, 09:14 PM

Here's my system complete with crude working drawing if you want to copy it!

http://www.rcgroups.com/forums/showt...t=Thrust+stand

Cheers, Phil

CAFplanekid · Oct 14, 2004, 09:53 PM

Get on the Zone and ask or search for anything posted by Dr Kiwi, of course!

I really do need to get a test stand, though, but the Dr is a great resource for anyone without the tools to do it themselves.

Or I pull the plane vertical and hit the throttle, if it goes up for a long time my thrust measurement is 'Alot!'
Jonathan

Dr Kiwi · Oct 14, 2004, 10:07 PM

Dammit Jonathan, you can make a stand like mine in less than an hour for $5 in materials - get to it!

CAFplanekid · Oct 14, 2004, 10:36 PM

I know, I really need to do it. I also need a whattmeter and I would be set. I guesss I should get it done this weekend and sell something for a whattmeter.
Jonathan

Tres Wright · Oct 14, 2004, 10:50 PM

Here's mine. Pretty fancy, huh?

The top one was the first one I rigged up, it was actually my balance stand which I would tape down to the scale and then tape a rod with a motor mount across it. Problem is I was always taking it apart and putting it back together depending on whether I was balancing planes or doing thrust tests. I finally built a permanent stand out of CF rods (bottom pic). I use an old feather receiver and just let everything hang off to the side as in the top pic. Then when I'm ready to test I turn on the scale. It automatically zeroes out all the weight, so when I power up the motor the scale reading is giving me thrust only. Very simple, but it works great.

Tres Wright · Oct 14, 2004, 10:53 PM

BTW, I tape the stand to the scale when I'm doing tests. The rods are set far enough apart to where I can run a 14" prop. The height is enough that I can change props without removing the motor from the stand. I've used it to test EDFs by taping the EDF to the mount. I've also checked IPS gearboxes, I have a smaller mount that screws to the big mount for those.

Dr Kiwi · Oct 14, 2004, 10:54 PM

Jonathan, if you like to fool with computers, get the Medusa Power Analyzer Plus, with the cable link for your laptop and you can graph amps/volts/watts etc. More displacement activity!

Cheers, Phil

JWarren · Oct 15, 2004, 11:19 AM

Thanks to everyone who has posted so far! I did'nt think I would get this many responces. I have ordered a scale and have a design in mind. As soon as the scale arrives I will start building and share in this thread.

Thanks again

John

Dr Kiwi · Oct 15, 2004, 11:24 AM

Here's mine with an "adapter block" for EDF 40's and EDF 50's.

Cheers, Phil

Oct 14, 2004, 06:06 PM	#1
JWarren Just one more plane! Join Date: Aug 2004 Location: Port Saint Lucie, Florida, United States Posts: 2,537	How do YOU measure thrust? Hello all! After giving much thought to measuring thrust on an electric setup and seeing many posts, scattered all over this forum as well as others. I wanted to get some input from the many forum members who have given their time and knowledge to help others and to also say thanks for all that help! I am not looking for anything dealing with software here. I am looking for those devices which are used in actual testing by using the motor/prop setup and some type of guage to measure the thrust. Myself, I have used the software programs to calculate intial setups before purchase and they have helped with a ballpark motor and prop setup for a particular plane. But generally, I find the motor/prop selection to be off in some way and another motor/prop selection was needed. So, if you have a homemade device or one you have bought, which you use to measure thrust in real world testing, I would like to see a few examples. I am not really sure how to go about making one which will give an acurate result. I have seen alot of debates on just how to make one, which is correct, I sure don't want see any of that here. So, please, NO fellow R/C'er bashing! Thanks in advance for your post. P.S. Pictures please! Some of the photos I have seen in the threads are outstanding by the way! John

Oct 14, 2004, 06:24 PM	#3
lensrc Kickin It Ol'Skool Join Date: Nov 2001 Location: Kansas City area Posts: 2,715	My setup Here is a pic of my thrust test bed. Tests are done in pusher mode. Works fine for brushless motors. If I need to do a tractor test I have a lever setup that I use with the same scale. I dont have a pic of it. Len Attached Thumbnails 87.8 KB · Views: 2490

Oct 14, 2004, 07:02 PM	#5
crashingagain Registered User Join Date: Nov 2003 Location: Sacramento Posts: 945	Heres mine Attached Thumbnails 23.4 KB · Views: 2200 17.8 KB · Views: 1725

Oct 14, 2004, 09:53 PM	#8
CAFplanekid De-Brushed user Join Date: Dec 2002 Location: Midland, Tx / W. Lafayette, Ind. Posts: 2,895	Get on the Zone and ask or search for anything posted by Dr Kiwi, of course! I really do need to get a test stand, though, but the Dr is a great resource for anyone without the tools to do it themselves. Or I pull the plane vertical and hit the throttle, if it goes up for a long time my thrust measurement is 'Alot!' Jonathan Last edited by CAFplanekid; Oct 14, 2004 at 09:55 PM.

Oct 14, 2004, 10:50 PM	#11
Tres Wright Live to ride... and fly! Join Date: Mar 2002 Location: Forney, TX Posts: 13,063	Here's mine. Pretty fancy, huh? The top one was the first one I rigged up, it was actually my balance stand which I would tape down to the scale and then tape a rod with a motor mount across it. Problem is I was always taking it apart and putting it back together depending on whether I was balancing planes or doing thrust tests. I finally built a permanent stand out of CF rods (bottom pic). I use an old feather receiver and just let everything hang off to the side as in the top pic. Then when I'm ready to test I turn on the scale. It automatically zeroes out all the weight, so when I power up the motor the scale reading is giving me thrust only. Very simple, but it works great. Attached Thumbnails 59.0 KB · Views: 2057 60.0 KB · Views: 1777

Oct 14, 2004, 06:23 PM	#2
phat23 Average User Join Date: Aug 2003 Location: Bakersfield, California Posts: 1,533	http://www.rcgroups.com/forums/showt...=271490&page=1 See post #6. Made this setup in less than an hour with scrap wood and a cheap kitchen scale.

Oct 14, 2004, 06:36 PM	#4
Tom Frank Dance the skies... Join Date: Dec 2003 Location: Sammamish, WA Posts: 5,991	Here's mine: http://www.rcgroups.com/forums/showthread.php?t=252722 Works great. The scale measures in either grams or pounds/ounces (to the nearest 1/10th oz). It doubles as a prop balancing rig as well.

Oct 14, 2004, 09:14 PM	#7
Dr Kiwi Registered User Join Date: May 2003 Location: Chattanooga, Tennessee, United States Posts: 19,922	Here's my system complete with crude working drawing if you want to copy it! http://www.rcgroups.com/forums/showt...t=Thrust+stand Cheers, Phil

Oct 14, 2004, 10:07 PM	#9
Dr Kiwi Registered User Join Date: May 2003 Location: Chattanooga, Tennessee, United States Posts: 19,922	Dammit Jonathan, you can make a stand like mine in less than an hour for $5 in materials - get to it!

Oct 14, 2004, 10:36 PM	#10
CAFplanekid De-Brushed user Join Date: Dec 2002 Location: Midland, Tx / W. Lafayette, Ind. Posts: 2,895	I know, I really need to do it. I also need a whattmeter and I would be set. I guesss I should get it done this weekend and sell something for a whattmeter. Jonathan

Oct 14, 2004, 10:53 PM	#12
Tres Wright Live to ride... and fly! Join Date: Mar 2002 Location: Forney, TX Posts: 13,063	BTW, I tape the stand to the scale when I'm doing tests. The rods are set far enough apart to where I can run a 14" prop. The height is enough that I can change props without removing the motor from the stand. I've used it to test EDFs by taping the EDF to the mount. I've also checked IPS gearboxes, I have a smaller mount that screws to the big mount for those.

Oct 14, 2004, 10:54 PM	#13
Dr Kiwi Registered User Join Date: May 2003 Location: Chattanooga, Tennessee, United States Posts: 19,922	Jonathan, if you like to fool with computers, get the Medusa Power Analyzer Plus, with the cable link for your laptop and you can graph amps/volts/watts etc. More displacement activity! Cheers, Phil

Oct 15, 2004, 11:19 AM	#14
JWarren Just one more plane! Join Date: Aug 2004 Location: Port Saint Lucie, Florida, United States Posts: 2,537	Thanks to everyone who has posted so far! I did'nt think I would get this many responces. I have ordered a scale and have a design in mind. As soon as the scale arrives I will start building and share in this thread. Thanks again John

Oct 15, 2004, 11:24 AM	#15
Dr Kiwi Registered User Join Date: May 2003 Location: Chattanooga, Tennessee, United States Posts: 19,922	Here's mine with an "adapter block" for EDF 40's and EDF 50's. Cheers, Phil

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