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Search: Posts Made By: SystemTheory
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06-08-2010, 10:36 PM
Replies: 344
Views: 160,502
Posted By SystemTheory

evolution1, Servo control is cheap and easy...

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...
06-04-2010, 02:45 PM
Replies: 344
Views: 160,502
Posted By SystemTheory

DamoRC, That's a neat little device. What...

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...
01-02-2010, 01:59 PM
Replies: 344
Views: 160,502
Posted By SystemTheory

I'm bumping this thread and posting an excellent...

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...
10-08-2009, 03:38 PM
Replies: 2
Views: 648
Posted By SystemTheory

What he said above. Also in electric...

What he said above.

Also in electric aviation and high velocity cars you'll see motors driven by 4s or 6s LiPO packs, which have very high voltage.

Generally a high voltage motor has more...
10-08-2009, 03:21 PM
Replies: 11
Views: 902
Posted By SystemTheory

Let's say everyone is using a spec battery and...

Let's say everyone is using a spec battery and motor. Then everyone has about the same "power to weight" ratio in the basic power plant. If this is a brush motor (I suspect), then we can get into...
10-07-2009, 04:35 PM
Replies: 49
Views: 5,915
Posted By SystemTheory

Right - I did confuse capacity C and C-rate of...

Right - I did confuse capacity C and C-rate of discharge up there. So for proper C-rate testing, one would take the label capacity C from the maker of the pack. Charge and discharge the pack at...
10-07-2009, 04:13 PM
Replies: 49
Views: 5,915
Posted By SystemTheory

How do you measure the IR? I used a 1-amp...

How do you measure the IR?

I used a 1-amp current regulator and digital meter that reads millivolts to measure voltage drop under modest regulated load, but the error of the meter in the millivolt...
10-07-2009, 02:27 PM
Replies: 49
Views: 5,915
Posted By SystemTheory

linger, I do not understand why a proper...

linger,

I do not understand why a proper C-rating requires 20 charge/discharge cycles, and why does the discharge rate need to increase with more cycles?

A few years ago you could buy matched...
10-03-2009, 12:28 PM
Replies: 344
Views: 160,502
Posted By SystemTheory

The main use I see for a brake is to measure...

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...
10-02-2009, 11:44 AM
Replies: 344
Views: 160,502
Posted By SystemTheory

What do you intend to accomplish in terms of test...

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 ...
10-01-2009, 11:03 AM
Replies: 344
Views: 160,502
Posted By SystemTheory

I'm not sure what you're trying to accomplish...

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...
08-14-2009, 04:37 PM
Replies: 23
Views: 1,791
Posted By SystemTheory

Is it worth the cost? Definitely not in stock...

Is it worth the cost? Definitely not in stock racing

I missed the part about beefing up wires and connectors.

Summarizing what I see above, if the battery is actually higher C with lower...
08-13-2009, 02:11 PM
Replies: 23
Views: 1,791
Posted By SystemTheory

There is a diminishing return curve in terms of...

There is a diminishing return curve in terms of acceleration torque and peak mechanical power but I'd need some motor resistance data to generate a typical plot from a 2s Lipo voltage source with...
08-05-2009, 06:19 PM
Replies: 15
Views: 2,749
Posted By SystemTheory

Due to heat dissipation and other physical...

Due to heat dissipation and other physical limitations, most devices must operate within the SOA, the Safe Operating Area. This is an area imposed on the volt-ampere characteristic for a DC device,...
07-31-2009, 05:33 PM
Replies: 58
Views: 25,723
Posted By SystemTheory

In a brush motor the peak mechanical output power...

In a brush motor the peak mechanical output power (shaft power) is 1/4 the starting electrical power input. Electrical power peaks at zero rpm and goes down exponentially as the rpm and reverse-emf...
07-25-2009, 02:21 PM
Replies: 58
Views: 25,723
Posted By SystemTheory

My godson reminds me to question information...

My godson reminds me to question information posted on Wikipedia, since you don't know the source of the edits. He has a good teacher ...

Reading this thread reminds me of the Skin Effect. A...
07-09-2009, 01:55 PM
Replies: 344
Views: 160,502
Posted By SystemTheory

Access, I agree with your comments. I think...

Access,

I agree with your comments. I think +/- 1{mph} was the resolution of one speed gun specification I read, but I can't recall the make and model. This is obviously a bigger percentage error...
07-07-2009, 05:38 PM
Replies: 344
Views: 160,502
Posted By SystemTheory

Brute Force Gearbox Study - Corrected

The graphic shows corrections to my code in the left panel, and an additional block of code to plot John's ratios against my estimated 1/10 car parameters.

This model suggests the opposite of...
07-06-2009, 01:35 PM
Replies: 344
Views: 160,502
Posted By SystemTheory

Brute Force Maximum Velocity Gearbox Study

The attached graphic is a load line analysis to predict top speed for a wide range of installed gear ratios. There is a sweet spot in terms of "salt flat" gearing, but note, this does not include a...
07-05-2009, 01:39 PM
Replies: 344
Views: 160,502
Posted By SystemTheory

The graphs look right based on a cursory review....

The graphs look right based on a cursory review. I agree that as the speed reducing gear ratio, G, goes down the top speed in a frictionless system goes up, assuming a constant tire radius r.

But...
07-02-2009, 04:55 PM
Replies: 344
Views: 160,502
Posted By SystemTheory

This new development sounds promising. I'm eager...

This new development sounds promising. I'm eager to see how it pans out.

I'm going to revisit my study of the sweet spot in the gear ratio. Maybe I can come up with a closed formula that predicts...
06-24-2009, 05:52 PM
Replies: 26
Views: 26,426
Posted By SystemTheory

In terms of system parameters, what does an...

In terms of system parameters, what does an optimized Full Scale car look like? It has the lowest mass and the highest power to weight ratio. It has the stickiest possible tires and makes the most...
06-10-2009, 11:45 AM
Replies: 152
Views: 17,343
Posted By SystemTheory

Xtreme RC Cars July 2009 has an article on...

Xtreme RC Cars July 2009 has an article on C-rating and impact of internal resistance on acceleration curves in a standardized system. Only thing I would like to see is more system data about the car...
06-05-2009, 01:03 PM
Replies: 344
Views: 160,502
Posted By SystemTheory

Noise in the three phase switching system of a...

Noise in the three phase switching system of a brushless motor occurs on both the power supply bus (inductive voltage spikes) and due to radio frequency induction (antenna effects picking up radio...
05-31-2009, 06:03 PM
Replies: 344
Views: 160,502
Posted By SystemTheory

Bob thanks for the information. If the model...

Bob thanks for the information.

If the model doesn't account for current/torque limiting during electronic commutation in the speed controller, which I suspect is necessary to protect the coils...
Showing results 1 to 25 of 139
 


 
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