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The Homebuilt Dynamometer (Dyno)Thread!!!

The Homebuilt Dynamometer (Dyno)Thread!!!

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Old 02-10-2018, 11:23 AM
  #91  
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Hi all

I made some improvements, now measuring current, voltage and efficiency.
Some problem of noise remains.

Attached images: new display view and measure setup.
Attached Thumbnails The Homebuilt Dynamometer (Dyno)Thread!!!-display.jpg   The Homebuilt Dynamometer (Dyno)Thread!!!-setup.jpg  
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Old 02-10-2018, 12:05 PM
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Originally Posted by augu View Post
Hi all

I made some improvements, now measuring current, voltage and efficiency.
Some problem of noise remains.

Attached images: new display view and measure setup.
That's beautiful!

How many data points or what sampling rate are you using?
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Old 02-10-2018, 02:32 PM
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Graph has about twelve points, equispaced in rpm. Sampling is interrupt driven.
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Old 02-10-2018, 02:33 PM
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... about twenty points, pardon. The limit is the memory.
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Old 04-14-2018, 07:26 AM
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Hello guys,

tryin to get get back into rc racing after 6 years. I have now got most of the stuff to get back racing but a lot has moved on since I was last racing. I have build a homemade dyno cause I'm tight and do not want to burn my way through some motors while I work out boost and turbo settings.

My dyno is a pully system more for safety so the flywheel is balanced better and doesn't come off if not secured correctly. I will try to post a picture when I have enough post to upload. I know I think adds in some error but for my needs it should be sufficient.

i have watched some videos from nick Adams using dyno data for setting boost settings and have a question around the flywheel set up and differences which I'm hoping you can advise on. The inertia of my fly wheel is 0.000419 kgm2s2 and when I run tests on several motors my peak power for 30deg timing is about 7.2k rpm for a 13.5t motor. When I watched nick Adams video for a 13.5t fantom motor his peak power was at 10.5k rpm at the same timing. I know the dyno systems are different but does the inertia of the flywheel influence the rpm of the peak power?
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Old 04-14-2018, 08:27 AM
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Inertia will only affect the spin up time of the flywheel. Couple things it could be, correcting RPM for your pulley ratio or the voltage you are testing at. Image below is a 13.5T motor tested with 2S batt, direct drive flywheel (inertia is 63 gm-mm2). Hope this helps.
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Old 04-14-2018, 02:19 PM
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Thanks bob. The pulley ratio is 2:1 so the speed of the flywheel is not as intense. I was wondering about the ratio on my detection system which is eagle tree with magnetic sensor. I have compared the rpm values with the brushless sensor connected directly to the motor to ensure I am representing the true rpm of the motor. The low rpm was shocking for the magnetic system with the eagle tree even though the Amps and volts were changing the rpm was the same for 0.5s at the start. I was using 2s charged with 12A and volts was 8.1-8.2 for the tests.

I have tried to use to use your software for the analysis but the curves of my data are difficult to model like you show on your YouTube videos so I have been using an excel file from old posts from John statham (I think his name was). Not sure if I need a better file to calculate my values.
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Old 04-14-2018, 06:43 PM
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If you want email me a data file I'll see if I can process it. Send it to [email protected].
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Old 04-15-2018, 01:37 AM
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Thanks bob email sent
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Old 04-15-2018, 05:54 PM
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Maybe take a close look at your pulley system. Pullies are notoriously inefficient. It may seem small, but compared to direct drive, and the fact you are looking at high rpm may be a factor. Also double check where inertia is used in your power calculations. The reflected inertia of a flywheel is affected by the square of the gear ratio. With a 2:1 ratio, that would mean the inertia observed by the motor shaft is 1/4 the flywheel inertia. Use Google and the search term "reflected inertia" to see the concept (if you are unfamiliar), and to check my work.
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Old 04-16-2018, 03:19 PM
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Thanks mick

bob has corrected me on this as I was not taking this into account. I now also have the corrected rpms so am in the ball park with other 13.5t results I have seen. Hopefully I can now collect some data I can use to help with setting boost.

with the data I collect is it best to use the peak power and peak efficiencies to set up boost and turbo like I have seen on nick Adams video or as previous post have discussed use the torque data?
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