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Old 09-24-2009, 07:09 PM   #196
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have you tested a 21.5 with a 2s lipo? were buildin a chassis/ motor dyno with the sentry. and i just finished reading all the info posted in the last 13 pages and all i can sey is wow. thats alot of info to look at in all.
were planning on using alumimum disks and neo magnets to simulate resistance. (lenz LAW)
it increases resistance as rpm increases. so it should be a good start point.
with no friction .
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Old 10-01-2009, 12:03 PM   #197
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I'm not sure what you're trying to accomplish with a magnetic brake, some kind of controlled load simulation?

In the control system industry there are many kinds of brakes available for building assembly lines and factory machines. If load control is required for small systems an electrically modulated magnetic brake is one solution.

Here is a magnetic brake used on airplanes from a 9V battery for on/off braking, but something like this could be used for controlled braking if properly designed and rated for use with the Sentry Dyno.

http://www.hobby-lobby.com/wheels.htmBrake.htm
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Old 10-01-2009, 05:17 PM   #198
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thats nice but that has friction and using LENZI'S law nothing touches just magnetic force of the neo around the aluminum. so it never changes
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Old 10-02-2009, 12:44 PM   #199
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What do you intend to accomplish in terms of test and measurement using a light flywheel and fixed torque brake? That part is not clear ...
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Old 10-02-2009, 01:14 PM   #200
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On real dyno's the use the eddy current brake to hold a specific RPM and load. that way you can monitor at steady state instead of always changing conditions like a simple inertial dyno. Probably of more use for IC engines where you need to adjust AF and spark for load and RPM.

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Old 10-03-2009, 09:40 AM   #201
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With the newer speedo's some things are adjusted on a time delay. Because of this a transient measurement is actually more useful at the moment.

Rather than using an eddy current brake set-up you might want to look at building a flywheel that has adjustable weight. Full scale this is normally some extra disc sections that are pinned to the main flywheel.

Best case is to match the acceleration of the flywheel to how the car performs on the track. Normally less weight for small tracks and more weight for big tracks.
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Old 10-03-2009, 01:28 PM   #202
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The main use I see for a brake is to measure current draw at a simulated load condition. For example, someone here was trying to simulate current draw at top speed on the Velodrome using an old brush motor in generator mode with a high power resistor to simulate a steady load. The problem then becomes setting the right value of the load which is a function of actual friction in the driveline and air drag. However, ballpark measurements are sometimes useful too.

The only problem I see with tuning for peak power on a flywheel dyno is that, in some systems, more power translates to less on track performance, since in a "fuel efficiency" race it may be more important to stay high on the battery curve near the end to avoid power fade. This was more critical with NiMH because the internal resistance climbs more rapidly than with LiPO, as far as I can tell from some data posted around the web.
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Old 01-02-2010, 02:59 PM   #203
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I'm bumping this thread and posting an excellent four page discussion of the problems inherent in taking analog-to-digital measurements using a PC oscilloscope to measure nerve signals. The same principles apply to using a data acquisition module in general:

http://www.funjournal.org/downloads/GeorgeJUNEf06.pdf
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Old 01-29-2010, 12:23 PM   #204
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could someone upload some more engine vs engine power figures please.

if you have.
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Old 03-13-2010, 06:57 PM   #205
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Hey guys, Ive found this thread and found it quite interesting lots of information. A lot of the info is for using flywheel dynos, but would it be useful to have or make some kind of dyno used for real cars, the ones you would sit the car on spinning wheels/pulleys such as something similar to the pic attached, using the Novak sentry data logger information to get readings, would this be usefull or accurate or has anybody made such a similar type??
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Old 03-14-2010, 04:58 AM   #206
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PSE used to make a chassis dyno but it did not measure torque. A few guys have made there own chassis dyno based on the PSE unit but using the Novak Sentry for data logging.

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Old 03-14-2010, 09:30 AM   #207
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Kw = (Nm*RPM)/9550

If you got the power and rpm torque is easy.

sounds weird to only know the max power and not knowing the rpm or torque.
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Old 03-14-2010, 10:57 AM   #208
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Quote:
Originally Posted by MatsNorway View Post
Kw = (Nm*RPM)/9550

If you got the power and rpm torque is easy.

sounds weird to only know the max power and not knowing the rpm or torque.
Measuring the power going in is relatively easy. Problem is that the motor isn't 100% efficient. The only way to know the mechanical power is to measure torque and RPM.

We're using the electric power in and the mechanical power out to show efficiency.
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Old 03-24-2010, 06:37 PM   #209
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Quote:
would it be useful to have or make some kind of dyno used for real cars, the ones you would sit the car on spinning wheels/pulleys
Something like this one (I know - it's a bit rough as yet).

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.
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Old 04-27-2010, 09:54 PM   #210
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I've been toying around with my Fantom dyno using my recently acquired Tekin RS and a few 17.5 motors. The latest Tekin software is impressive and blows the LRP SPX out of the water. Has anyone figured out how to monitor efficiency with the Fantom Dyno yet?
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