Burties 'special apparatus' (RC dyno) lives

[Burtie]

Dyno frame.jpg (154.03 KiB) Viewed 1116 times

Dyno display.jpg (47.99 KiB) Viewed 1116 times

http://www.youtube.com/watch?v=nFZ5Gnm9Dws


Burtie

[Burtie]

Hopefully I will be collecting some data from this apparatus soon.

I will then be able to bore the pants off you all with many, many, graphs and plots and theories etc...

[Burtie]

I forgot to point out. one of the most important components, you might be wondering about;

The cardboard and paper structure in the background, is designed to prevent the generator from spraying grease all the way up the curtains.

[Miles]

[Arlo1]

Very cool!

[Burtie]

It is turning out to be quite of work to get this all functioning well, but it is all coming on slowly.

Dyno wth bulbs.jpg (247.32 KiB) Viewed 985 times

There are now two solutions for the electrical load on the generator:

1) I have added a 2nd controller to allow regeneration from the generator back into the power source. This seems to work ok, and we can recover about half the electrical energy we put into driving the motor.
So, for a 1kw input from the PSUs, I can drive the motor with 2kw.
The disadvantage is that the regen from this Xiechang controller is not variable except by reflashing the parameters, which is a hassle.
I am also concerned that this method may possibly introduce some unpredictable torque ripple, making the whole dyno run roughly.

2) I have built an array of 12v 50w halogen bulbs, which can be configured in several ways ( Delta or Wye, and 12v or 24v), to provide different loads for a given speed.
The whole array is capable of dissipating a maximum of about 2kw of electrical energy, and does a good job of heating my room during this cold weather

http://www.youtube.com/watch?v=xhPR8mAKgVk


Burtie

[adrian_sm]

This looks fantastic. I want one.

You mentioned you were decoding the display info to get data out of the watt meter. Jonas (Umejopa) reverse engineered the turnigy watt meter code. He modified it to act as a throttle interface between a hall throttle and a RC ESC, including amp limitting etc. So you might be able to tweak the code to your needs if you want. Note: I think the newer Watt Meter models have changed uP, so may only work on old models.

Here is a link to the first post he made publishing the code: memberlist.php?mode=viewprofile&u=16563

I have also noticed that the Amp readings are reported inaccurately at low amps, reporting too low a reading. So if this is your main power measurement, you may want to check calibration.

Keep up the outstanding work.

- Adrian

[liveforphysics]

I love your amazing work Burtie!!! This is awesome!

More data!

[acuteaero]

Very cool. This is the killer tool for developing and testing motor control hardware!

Looks like the load cell you're using is one of the cheap ones from eBay seller scale_bargains . Is it? That's what I was thinking about using on my project over here http://endless-sphere.com/forums/viewtopic.php?f=30&t=36803

I'm guessing you're not using their A/D USB board- are you using one of their little amplifier/exciter boards? Or how otherwise are you managing the excitiation/signal conditioning?

Thanks! And again- awesome project!

[Doctorbass]

Awsome!..

and for those who would like a great ebike front lamp.. think about it

[johnrobholmes]

Very cool, love the torque arm setup!

[Burtie]

Thanks guys, glad you like it.


Adrian, thanks for the tips on the Turnigy watt meter. I will be sure to check the calibration of the sensors before I take any of the readings too seriously.

Acuteaero, Yes the load cell stuff comes from the cheap source on ebay (search for 'load cell kit' ). It uses parts from the 25lb kit.

The microprocessor, and usb link of the kit are not useable for this job, because the firmware wont output any readings unless the load on the cell is absolutely constant (which it never will be on an operating dyno).

The front end of the kit uses an Avia HX711 chip which is a combined instumentation amp and autonomous 24 bit ADC. You can find a summary data sheet for it on the internet:
http://www.aviaic.com/UpLoadFile/hx711_brief_en.pdf

If you look at the kit pcb, you can find two tracks carrying clock and serial data going from this chip (pin 11 +12) to the processor.
You will need to connect your own microprocessor to these clock and data lines to capture the 24bit data which is transmitted 11 times a second.
You will then need to write your own filtering and scaling/calibration functions.

Burtie

PS I like your approach of using a car alternator as the generator and varying the field current to change the load, -very neat

[E-racer]

This thing rocks! i just noticed it. Any clue what the peak power rpm is for a 6 turn delta 80-100?

[Burtie]

This thing rocks! i just noticed it. Any clue what the peak power rpm is for a 6 turn delta 80-100?

Surely the faster it spins, the more power you can make, all else being equal ?

[E-racer]

This thing rocks! i just noticed it. Any clue what the peak power rpm is for a 6 turn delta 80-100?

Surely the faster it spins, the more power you can make, all else being equal ?

I've found that is not the case when running a NV cvt. If i set the transmission to hold 5000 rpm my bike is slower than if i set it to 4000. My butt dyno says that 4000rpm +/-500rpm seems to feel about the same. I'd love to really know where all the power is.

[Arlo1]

This thing rocks! i just noticed it. Any clue what the peak power rpm is for a 6 turn delta 80-100?

Surely the faster it spins, the more power you can make, all else being equal ?

I think I read someware there dont like over 10000 rpm so I would think 8-9000 will be where the peak power is. I think with optimal voltage any 80-100 is ~7kw peak!

[Burtie]

Yes, I guess when considering the whole system, taking into account the system battery voltage, and the controller limits and controller limiting mechanisms, there will be an optimum rpm for maximum power output.

For this question, I think it is needed to consider the whole system rather than the motor in isolation.

[Green Machine]

So i was at the astro flight motor factory the other day and i noticed they had built a similar dyno to test their motors. It was the coolest machine i saw in the whole factory.

However they were using a water brake on theirs, and a torque sensing unit. I think Burtie's design is probably better and much cheaper to build.

I really want to build one of these dynos so that i can test different motor set ups for climbing up pikes...also for testing efficiency of different motors, and getting real data on how reliable and efficient each motor is..even hub motors.

[acuteaero]

I really want to build one of these dynos

Hey Eric- don't know if you saw the thread I started a while back- viewtopic.php?f=30&t=36803 I wrote a bit about the different types of dynos (waterbrake, etc) there. I am going to finish my dyno up in the next few weeks-ish... in order to do some RC motor testing primarily to get PaulD's bike running reliably. I'm right in your neighborhood- if you're interested you'd certainly be invited to check it out when I get it going. I have some 80100 motors, some 6364 motors and an Astro 3210 to run tests with... Burtie also supplied some details about his software/hardware setup in that thread. Speaking of which...

Sorry for the little thread-jacking there...

[Burtie]

Burtie, is that custom software you are using to get those torque and efficiency readings?

Yes, the Electrcal power in, RPM and Torque data from the various sensors, is all read by a PIC18 u-processor, running custom firmware.
The data from the sensors is filtered and sent out on a serial link.

There is a custom c# application running on the PC that reads the serial data and displays it. This application also calculates efficiency figures and averages, and provides the user with the facilities to calibrate/scale the sensors.


Unfortunately some of the hardware is cobbled together with odd bits from my electronics junk box, so it would not be easy to replicate exactly.
(This is the particular processor board I used: http://www.futurlec.com/ET-PIC_Stamp.shtml )

Burtie