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Old 06-04-2010, 03:45 PM   #211
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DamoRC,

That's a neat little device. What are you using for a PC interface? I might build a small prototype and scale it up to dyno my little brother's midget race cars. How do you measure torque and identify Max power?

The primary problem with a chassis dyno is picking a flywheel load as a reasonable approximation of the road load (the mass of the chassis reflects to the engine/motor through the gearbox and tire ratio). I think on track performance in a specified gear and tire radius is best simulated via a proper flywheel inertia in the dyno itself.
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Old 06-04-2010, 05:07 PM   #212
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Quote:
Originally Posted by SystemTheory View Post
DamoRC,

That's a neat little device. What are you using for a PC interface? I might build a small prototype and scale it up to dyno my little brother's midget race cars. How do you measure torque and identify Max power?

The primary problem with a chassis dyno is picking a flywheel load as a reasonable approximation of the road load (the mass of the chassis reflects to the engine/motor through the gearbox and tire ratio). I think on track performance in a specified gear and tire radius is best simulated via a proper flywheel inertia in the dyno itself.
The Novak Sentry Logger has a usb interface.
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Old 06-05-2010, 09:40 PM   #213
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@systemtheory

Thanks.

The interface to PC is simply through the microphone jack. You can find some details on the build and the software for download the website:

(oops - I tried to post a link to the website but I do not have enough posts on the forum to be permitted this privelege - the site is listed in the "More Info" section of the Youtube video.

All the system really measures is the RPM of the rollers. Everything else is calculated based on the various weights and dimensions of the rollers and wheels. The software in the vid is an early version and, because of the noise in the system, those max torque and power numbers are unreliable (there is more discussion of this at the website with some curve fitting solutions). I am working on a version of the software that will perform the curve fitting. I would also like to develop a wattmeter with a pulsed output. This could be connected to the second side of the stereo mic input so you could measure the electrical power consumption at the same time that you are measuring the mechanical output of the car.

With respect to the flywheel load - it is possible to pick a roller configuration (mass, diameter etc) that matches your car weight so that you can reflect real world conditions. The only thing you are missing is the aerodynamic drag which you can approximate in when you crunch the data. I like this approach exactly because you are including transmission losses etc in the measurement.
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Old 06-06-2010, 01:57 AM   #214
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Hello,

How can I direct an ESC (servo) via PC (usb) to simulate some laps on a rollerbench ? Where can I find some info about this ? Software, integrated circuit, example, ....

Thanks.
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Old 06-08-2010, 11:36 PM   #215
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evolution1,

Servo control is cheap and easy over USB:

http://www.pololu.com/catalog/product/1350

However study the resources page and users manual before you purchase, to see if you can script throttle profiles to suit your needs. The PC control interface is now the hard part of these projects and a good interface is not cheap or easy to find.

I think one could learn alot from such a project, but getting accurate track performance simulation is very challenging. The dyno must produce the same mechanical loads you would see on the track to thermally stress the battery and motor at each operating point, a nearly impossible task without accurate physical measurements and active braking in the dyno rollers to simulate wind resistance.

My brother runs typically an oval with a 250cc or 750 cc motorcycle engine on his cars, and a single engine pull on the dyno with proper flywheel to match the load exiting a corner would improve engine tuning and gearbox tuning, I suspect. However it is an ambitious project so I might build a scale system to shake down the electronics and test my physics models. With the 250cc cars humidity has a big impact on the methanol fuel tuning so the dyno may not have sufficient "input" controls to give repeatable results ...
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Old 06-09-2010, 07:12 AM   #216
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Default Fantom dyno software

Hi,

I acquired a Fantom dyno, but need software for it. Is there any source for the original, or any other available software that would work reasonably well with it?

Thanks
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Old 06-09-2010, 12:40 PM   #217
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Quote:
Originally Posted by SystemTheory View Post
evolution1,

Servo control is cheap and easy over USB:

http://www.pololu.com/catalog/product/1350

However study the resources page and users manual before you purchase, to see if you can script throttle profiles to suit your needs. The PC control interface is now the hard part of these projects and a good interface is not cheap or easy to find.

...
Thanks for the info.
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Old 06-11-2010, 09:52 PM   #218
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Default Fantom dyno software

Hi, anyone have any info as to where I might obtain the Fanton Dyno software? Any substitutes that would work?

Thanks


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Hi,

I acquired a Fantom dyno, but need software for it. Is there any source for the original, or any other available software that would work reasonably well with it?

Thanks
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Old 06-12-2010, 11:07 AM   #219
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oldrcr-Send me an e-mail. I will try to e-mail a copy. [email protected]

Here are a couple of spy shots of Roy's particularly nice recent Sentry Dyno. Hopefully some results might be posted.
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Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-dyno1.jpg   Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-dyno2.jpg  
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Old 06-23-2010, 11:24 AM   #220
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I thought I would repost this here as this gearing maximum power for average speed was discussed earlier in this thread but on the oval.
Gearing
The best way to gear your car is to start with a fast guys gearing. Some other things to note. An electric motor has its peak power at about 1/2 of its maxium amp draw. Amp draw at peak power is usually a big number and results in a lot of motor heating as we strive to gear the motor for peak power. So another trick we use is a temp gun and gear for 160-180 F. This should not be an absolute as on some tiny tracks you may just have to gear lower and not develop so much heat. In low traction you will not develop as much heat either.

Gearing Maximum Power at the Average Speed
I have used this method on the oval to good success. I thought I would explain it here as it turns out my TC4 is geared pretty close to this after some trial and error gear testing on the track and in my driveway.

I paced out my runline on the track with a 3 foot pace, 82 paces, 246 ft run line. A good lap is 10.4 seconds. Dividing gives my average speed of 23.6 ft/s (16 miles per hour). I will change this to inches per min for convenience

23.6 ft/s x 12in/1ft x 60s/1min = 16992 in/min

If I divide this by the wheels circumference I will get average wheel RPM

wheel circumference = (diameter x pi)
16992 in/min / (2.375 x 3.14) = 2280 RPM

Now to see what my wheel RPM is at Maximum Power. I look at the dyno sheet at the Red line. It peaks pretty close to 10,000 RPM, Maybe just a little past. If I divide this by my gear ratio I will get my wheel RPM at max power.
10,000 / 4.72

2118 RPM

My average wheel RPM is 2280 That is within 7% of my Wheel RPM at max power. To get closer I should gear up.

10,000/2280 = 4.38

Anyway the concept would work to gear maximum power at the average speed even on this small touring car track. Note that this dyno run came from my homemade novak Sentry dyno that we developed on a thread by the same name. Most 13.5 motors are going to be very similar to this one where they develop maximum power. I am running a speed passion 13.5. It would be interesting to get a dyno run. I stole the dynos speed control for this car, though, so its not so convenient.

Maximum Amp Draw
Check out that green line, amp draw. Our sentrys were specifically modified to get good number here up to 220 amps or so. This motor is pulling 110 amps soon after startup. You need good connectors and fat wire to get this to the motor. You only achieve this on the track with good traction.

John
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Last edited by John Stranahan; 06-23-2010 at 12:06 PM.
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Old 07-02-2010, 01:19 PM   #221
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Hello John Stranahan,

How You calculate power, torque and efficientie (see dyno sheet) with Novak Sentry data ? Program ?
All info welcome.

Tia.
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Old 07-02-2010, 04:26 PM   #222
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I have a spreadsheet that I co wrote that does the calculations from a set of data points gathered by the Sentry. Be happy to send you a copy. Send an e-mail request to [email protected]
John
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Old 07-21-2010, 02:19 AM   #223
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Ive been following this thread for quite some time now and I wanted to ask you guys regarding these new generation ESCs that have turbocharger, supercharger-like effects in them. Is it possible to increase the RPM of the motors (with these new generation ESCs) beyond the kV rating of the motors? Please correct me if Im wrong, Ive read that the max possible RPM of a motor is dependant upon the applied voltage and also the motor kV rating.
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Old 07-21-2010, 11:19 AM   #224
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I believe the answer is yes. The boost and turbo functions affect motor timing. Motor timing does affect RPM. More timing more RPM. The main benefit of Boost is to shift the power vs RPM hump to the right. That means there is more power at higher RPM. For Boost you are supposed to add boost to an RPM threshold that occurs only on the straight. This increases top speed. It sacrifices some efficiency from our dyno testing, so the motor runs a little hotter.
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Old 07-21-2010, 07:03 PM   #225
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Thanks a lot Ill be getting the Novak sentry and a laptop in the distant future as a telemetry device.. when exactly I dunno: Are that the BL motors we use mostly are wye-winding, totally DC motors? (need to research back on my old college textbooks, my theory has rusted terribly) Thanks again for the help. BL motors!! here I come!!
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