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Old 07-21-2010, 10:02 PM   #226
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Yes-they are permanent magnet DC motors. The current is pulsed at high frequency to control speed, though. There are different types of winds like the Delta wind popular in Europe, but they are still DC.
John
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Old 11-09-2010, 09:28 AM   #227
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John

It's been quite some time since anyone posted here, so hopefully you catch up with this.

You emailed me a copy of your spreadsheet a couple months back, thanks! Just finally getting started with my whole dyno/data logging project. We have a group from our club that will be working together on this. To keep everyone on the same page we will be following the "testing" outline below.

1) On the Sentry Dyno - test all of our relevant motor/timing combinations.

2) Process each set of data through your spreadsheet to establish baseline data for each configuration.

3) Establish predicted gearing values for each configuration

4) Install Sentry in the car and make comparative runs based on the dyno studies. Attempt to optimize in-car data to the baseline dyno data.

This should get us as close as possible to being able to use the maximum each configuration is capable of. Of course we still have to put a smooth run together from the transmitter end of things or it really doesn't much matter.
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Old 11-10-2010, 12:41 PM   #228
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Good luck. I look forward to some posted results.
john
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Old 11-15-2010, 12:04 PM   #229
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John,

Forgive my recall on my Physics formulas, it's been awhile.

For my testing calculations I need to have an accurate Moment of Inertia for the Flywheel and rotor. My recall keeps looking like : MI = 1/2 (M)ass*(r)adius ^2? Mass should be measured in kg?

I am testing 1S 3.7v brushless 17.5 and 13.5 with ROAR 12.3mm & 12.5mm rotors. This is for 1/12th and WGT classes, onroad - carpet, dynoed on an aluminum fantom flywheel.

Thanks in advance!

Aaron
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Old 11-15-2010, 02:18 PM   #230
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That would be the correct formula and units.
John
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Old 12-03-2010, 08:55 PM   #231
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any new up dated imfo on these dynos?

Last edited by impdog; 12-03-2010 at 08:57 PM. Reason: wording
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Old 04-20-2011, 03:59 PM   #232
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Homade Dyno Reaches Production

McPappy Brushless Motor and Gear Dyno

The homemade brushless motor dyno described in the following thread has now reached Production. McPappy –The makers of a deluxe oval pan car The Dart 2.5 have taken on this challenge.

The McPappy Dyno package includes everything in photo 1, which I just received. You supply a speed controller (the one from your car will work fine) A servo tester to start and stop the test (or your transmitter and receiver), a Novak Sentry for data acquisition, and your test motor.
The most accurate data will be obtained by spinning up the supplied flywheel until near max RPM. The sentry will gather the data, you will copy and paste it onto the supplied (shareware) spreadsheet that was written in the thread above by Matnin and Myself. A power curve will be generated with an accurate Maximum Power calculated.

The dyno has additional flexibility. You can run your 21.5 slave motor which is hooked up to a bank of resistors with the test motor. An approximate power will be calculated which should be very helpful for comparison testing.

Additionally, the test motor can power the slave through a set of gears. We have all guessed at the power loss in a single set of gears (12% or so). Now a precise test will be available. You might be able to see if there is any noticeable difference in friction between the big pinion big spur vs little pinion and little spur of the same ratio.

These latter two test are not included in the software as yet. This is my task at present.

The following pictures 2-5 show McPappy’s Prototype Dyno which may differ slightly with my build.

Follow the slave motor development right here. Please feel free to add your input. This is the plan

Run a motor with the flywheel and get an accurate power curve including efficiency.
Use Electrical Formulas to calculate the power output of the slave. The sentry has the ability to test volts and amps accross the resistors. Use an efficiency number from an RPM chart to correct the power for losses. Once accomplished this should get us a quick power number and may work better with the Sentrys data aquisition rate.
John




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Old 04-20-2011, 04:22 PM   #233
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John - have u tried the eagle tree data logger as an alternative to the novak sentry?
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Old 04-20-2011, 05:22 PM   #234
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Hanulec- I have not personally used the
Eagle Tree For Data Aquisition. I think I went to the web site once and thought it suitable, but not better. If you have used it please make a post. Data aquisition rate is somewhat of a problem when running a flywheel test. We get 10 data points a second. With a powerful motor a lot happens in that first second. Especially with the Fantom aluminum flywheel. What we do is just use the middle part of the test which is quite smooth for our flywheel run and also use a heavier flywheel on less powerful motors.
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Old 04-20-2011, 05:32 PM   #235
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I have - but not outside of running car on the track. I haven't done the comparison .. and was hoping u had some insight ..
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Old 04-20-2011, 05:40 PM   #236
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I believe the eagle tree data eLogger v4 can do up to 50 samples per second.
I had the v3 eLogger yet promptly returned it because I couldn't get consistent rpm data.
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Old 04-20-2011, 06:00 PM   #237
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Quote:
Originally Posted by Magnet Top View Post
I believe the eagle tree data eLogger v4 can do up to 50 samples per second.
I had the v3 eLogger yet promptly returned it because I couldn't get consistent rpm data.
did u try the brushless rpm sensor or the optical. we've had better luck w/ the optical.
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Old 04-20-2011, 06:22 PM   #238
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I checked the Eagle tree site again. Here are some notes.

High speed logging at up to 50Hz (increased from 10Hz).

This means and increase from 10 data points a second to 50 points a second. Very Nice, but it is version 4 which you may or may not have. The car version has an adjustable data rate.


Compatible with excell

This means you can cut and paste data from the logger output into excell. This means you could use it instead of the Sentry.
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Old 04-20-2011, 06:22 PM   #239
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Hanulec, Magnet top-Tahnks for the posts.
I used the brushless sensor exclusively on the Sentry. It worked very well.
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Old 04-20-2011, 06:26 PM   #240
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Quote:
Originally Posted by hanulec View Post
did u try the brushless rpm sensor or the optical. we've had better luck w/ the optical.
I only tried the brushless rpm sensor and saw that others had issues on their forum so I gave up quickly. Thanks for the heads up, maybe I'll give it another try.
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