R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Electric On-Road

Reply
 
Thread Tools Search this Thread
Old 04-22-2009, 01:25 PM   #76
Tech Adept
 
Join Date: Mar 2009
Location: Metro New York
Posts: 139
Default

Oval Track Map Update

Estimated acceleration points, braking points, and turning points now appear on the top section of the attached track map.
Attached Thumbnails
Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-ovalrunlines01.png  
SystemTheory is offline   Reply With Quote
Old 04-22-2009, 08:03 PM   #77
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

0.000000413kgm^2s^2 =armature inertia

I'll see if I can work up some other of your requested constants.

Sentry Dyno
work proceeds. The digikey 200 A sensor came in. I decided the best install would be to put it in the same little circuit board the original came in. I desoldered the large shunts first then the 3 small leads from the sensor. I cleaned the small holes out with an X-acto knife point. The new device slid right in when I bent the shunts. According to the wrapping this is a static electricity sensitive device. I imagine the little capacitor on the circuit board may help it be more robust after installation. Anyway I discharged myself on the barrel of the soldering iron before it got hot and proceeded. Here are some pics. Wish me luck. I have a new GTB in as well to test on the 3.5 motor.
Attached Thumbnails
Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-200-amp-sensor-ready-solder-.jpg   Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-200-amp-sensor-place-002.jpg   Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-200-amp-sensor-place-001.jpg  
__________________
[email protected]
TeamCRC.com Mikes-HobbyShop.com
John Stranahan is offline   Reply With Quote
Old 04-22-2009, 08:26 PM   #78
Tech Fanatic
 
Join Date: Jun 2006
Posts: 872
Trader Rating: 35 (100%+)
Default

I am VERY interested to see if this works,

Matt
__________________
High Desert Raceplace, Grand Jct CO, Sanwa Exzes Plus Stick Radio, Spektrum,Thunderpower 230g, Modified Tri-Nut Novak GTB2, Ballistic 4.5t 550, 5.83lb SCTE Ten, Novak Sentry Brushless Dyno, Crossweight Setup Station, Junsi 20A power supply Icharger 20A Charger,TP610C, 22B, Novak Edge, Novak 13.5, SC10, Havoc Pro SC XDrive, Ballistic 17.5 Matthew Joseph Cordova
mattnin is offline   Reply With Quote
Old 04-22-2009, 09:12 PM   #79
Tech Adept
 
Join Date: Mar 2009
Location: Metro New York
Posts: 139
Default

John,

Current sensor looks good. Hope it works as a drop in replacement.

I ran my engineering simulator with zero system inertia, zero driveline damping, and the 1/10 scale Dodge Viper aerodynamic model. The Oval line car accelerates from 24{mph} to 33+{mph} in about 0.5{s} and < 20{ft}. It is looking pretty good as a track performance confirmation of 135{W} on the Sentry.
SystemTheory is offline   Reply With Quote
Old 04-23-2009, 12:14 AM   #80
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Thanks guys. I may accelerate a set of tires and rear axle with a huge gear and see if we can experimentally determine the inertia by selecting an inertia that makes the power curve match.




Digikey 200 Amp Sensor Tests
We have liftoff
Here is some amperage data from a GTB running an LRP 3.5
Corrected Current amps
15
18
146
194
182
220
216
213
203
196
185
171
150
146
137
129
122
116
111
106
100
96

I ran a 30 amp discharge test through the Turbo thirty which I think is an extremely accurate instrument. Discharge numbers recorded were in the mid fourteens. Perfect. I went ahead and threw in a conversion factor as well as a multiplier of 2.0813. This factor and the digikey sensor was used to get these amp draw readings. I think because they are more in the proper range and because a calibration run was done that they are accurate. Now you might wonder why there are so high. I expected higher numbers from the GTB. There is less active timing going on. We are now getting a realistic 200 amp draw when we open the throttle on the bad boy motor. Note that all my previous test were done on an LRP sphere competition with a worlds cooling set that made it look like a TC edition. It was not. I will test a TC edition tomorrow on one of these hot motors.


I had some trouble. The GTB would not accelerate this motor smoothly on the dyno with an aluminum flywheel. I changed the sensor wire. I changed the motor, I got rid of the astroflight servo tester, Finally I used the "speed" setting on the radio and receiver setup and turned the speed down to -40. This opens throttle on a ramp. Then it ran smoothly. Note that this motor and speedo work flawlessly on the track with no abnormal setting. I will try a GTB motor tomorrow to see if that's the problem

We are getting great amp readings now. Thanks Joe (System Theory) for the part numbers.

I collected no RPM data on this run due to my troubles. I left the RPM sensor off.
__________________
[email protected]
TeamCRC.com Mikes-HobbyShop.com

Last edited by John Stranahan; 04-23-2009 at 12:25 AM.
John Stranahan is offline   Reply With Quote
Old 04-23-2009, 02:41 AM   #81
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

GTB and LRP 3.5

Here is the Dyno output
This motor actually reached 60600 RPM with this controller. The power at 575 W is about 15 Watts output higher than with the LRP spere competition (not the TC edition).

I believe the funny shape of the amp curve before 9000 RPM is the result of the radio ramp
Attached Thumbnails
Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-gtb-lrp-3-5-4-23-2009001.jpg  
__________________
[email protected]
TeamCRC.com Mikes-HobbyShop.com
John Stranahan is offline   Reply With Quote
Old 04-23-2009, 06:24 PM   #82
Tech Adept
 
Join Date: Mar 2009
Location: Metro New York
Posts: 139
Default

John,

The current sensor output looks really good after 15,000 rpm. I am not sure if the sensor pegs the current at the top rail when the Hall element saturates at high flux density, or if it might create a spurious lower current reading? Something to consider in your future tests.

A "chassis dyno" could be built from an accurate timer and a ramp:

http://solomon.physics.sc.edu/~tedes...mo/demo12.html

where one would neglect driveline friction and air resistance by keeping the exit velocity low and increasing the precision of the roll down timer. The fastest time occurs for a block sliding down a proverbial frictionless plane.
SystemTheory is offline   Reply With Quote
Old 04-23-2009, 09:47 PM   #83
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

System Theory - Take a look at this first graph. Only the second point pegs the amp meter at 220 amps. All the other numbers are slightly below. The amp curve is now typical because I am using a GTB controller with less active timing. Also no throttle ramp was needed to obtain absolutely smooth acceleration from a full stop.


Novak GTB, Novak velocity 3.5R VS LRP sphere Competition TC edition and X 12 3.5 R

Finally The Sentry Dyno is to the point where serious and accurate comparisons can be made on powerful motors.

This first comparison is with a Novak GTB and the Novak velocity 3.5. These are first generation items. I have had the motor a long time and used it a lot in the wide pan car. The marriage of the two is perfect. The second items in the comparison are the LRP TC edition speed control and second powerful generation LRP X12. This motor has been run once in my touring car. Again this is a happy marriage. There is plenty of traction for all the power that is available.

If you look at figure one The Novak by itself The chart shows peak power of 524 W. I manually input the highest RPM now looking at the raw data file, the motor reached 61224 RPM. The pitch is really screaming, but the sound level is very tolerable and smooth due to the floating motor mount.

Notice the green line is amps on this graph. It rises to a quick peak and then tapers off as the motor spins up and reverse voltage is built up. The shape is very similar to the stock motor I posted previously but now its up at 220 amps. That second green point pegs the amp meter at 220 (there is a peak on the line) and then there is a slow reduction (the line goes down). This is the typical amp curve a motor would have if no active timing was used.

The third chart shows the LRP TC edition running the X12 3.5. The motor reaches a screaming highest measured 68965 RPM. Higher than the older Novak motor. It also reaches a remarkable 675 Watts. That's just a remarkable 100 Watt increase over their old X11 3.5 and 150 W more than Novak's older Velocity 3.5

Note the amp draw at the beginning (the green line) is non typical. I have had to use a throttle ramp which slows slightly the application of full throttle (similar to a throttle roll on we talk about). This was necessary to eliminate some stuttering on full throttle on the dyno. On the track the motor is delightfully smooth and free of this effect.

Note that Novak has a new ballistic series of motors. I have a 3.5 on backorder with Novak. I'll test it when received.

Now I just have to see if I can run 5 minutes with this new LRP 3.5. The higher 60% efficiency (yellow line on right hand figure) suggest that I can.
Attached Thumbnails
Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-novak-gtb-velocity-3-5.jpg   Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-lrp-vs-novak-3-5s.jpg   Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-lrp-tc-edition-lrp-x12-3-5003.jpg  
__________________
[email protected]
TeamCRC.com Mikes-HobbyShop.com

Last edited by John Stranahan; 04-24-2009 at 03:07 PM.
John Stranahan is offline   Reply With Quote
Old 04-24-2009, 09:18 AM   #84
Tech Master
 
pejota's Avatar
 
Join Date: Apr 2008
Location: Vero Beach, FL
Posts: 1,022
Trader Rating: 12 (100%+)
Default

John

After this current test can one conclude that the newer Brushless ESCs can and will outperform older technology? I'm thinking along the lines of people running in stock and spec classes. If we all ran the same battery and motor would there be a noticable difference in peformance solely because of the ESC?

The Tekin RS series of ESCs are what come to mind. They have programable timing which in theory provides more power. If i had one it would be in the mail for testing but i only have the GTB and 21.5 combo for my VTA car.

Thanks for the testing and keep up the great work!
pejota is offline   Reply With Quote
Old 04-24-2009, 10:41 AM   #85
Tech Fanatic
 
Join Date: Jun 2006
Posts: 872
Trader Rating: 35 (100%+)
Default

Programmable timing does not necessarily provide more power. Adjusting timing changes the power band and can result in a loss of power if done incorrectly.
__________________
High Desert Raceplace, Grand Jct CO, Sanwa Exzes Plus Stick Radio, Spektrum,Thunderpower 230g, Modified Tri-Nut Novak GTB2, Ballistic 4.5t 550, 5.83lb SCTE Ten, Novak Sentry Brushless Dyno, Crossweight Setup Station, Junsi 20A power supply Icharger 20A Charger,TP610C, 22B, Novak Edge, Novak 13.5, SC10, Havoc Pro SC XDrive, Ballistic 17.5 Matthew Joseph Cordova
mattnin is offline   Reply With Quote
Old 04-24-2009, 10:42 AM   #86
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Pejota-This I can tell from this one motor test. If you want a spec class to be even, the motor brand and series of the motor should be specified until the supply is exhausted.

As far as speed controls I don't find the exact test you are looking for in about 40 recent dyno runs. Maybe in a week when my new dyno is up and running I will do this test. GTB vs LRP on the same motor.

I have always found that speed controls make more difference with stock motors and high traction. In this case you want the best speed control of any brand or you want to specify a lesser speed control of only one brand. In my recent testing I find less effect from active timing (boost) on the stock motors in the LRP series of speed control. This makes it more equal to the GTB with stock motors.

In track testing open mod TC with 3.5s there is little difference in performance between the GTB and LRP TC edition. There is a difference in heat evolved in the speed control. I believe the active timing is reducing amp draw at low RPM (high amps) and increasing amp draw at high RPM in the LRP series. The LRP TC edition speed control seems to run cooler and have thermal shutdowns less often. There may be other secrets that help this.

Battery Test on the Sentry Dyno
I compared my FMA Revolution 5000 mA-h pack which are 1 year old and have over 60 hard TC cycles on them to a newer Track Power 5400 Gold case pack that I have been using on the dyno. Here is a pic of the printout. I have only shown power and amp draw. Notice the two lower lines green and blue are almost identical idicating very similar amp draw. The highest lines with the boxes shows the power output with the Track power pack is clearly superior by 75 watts at peak power. I scanned the voltages at peak power and as expected the new pack just has higher voltage at peak power than the old pack. Similar test could be done with different brands of packs if I were made of money.

I guess I will be racing the gold pack. I probably need two for open mod TC as they are highly drained when a heat is finished. When the FMA pack was new, discharge test showed that the finishing order on these two batteries would be reversed with FMA putting out the most voltage and power. 60 + mod TC cycles is a lot of wear and tear. The FMA still feels very good on the track.

Note we started a new spec class. The motor brand and wind was specified as well as the Brand and Size of battery. The speed control was left open. Reason, see the graph above and below.

The dyno is off back to Colorado. Thanks Matt.
Attached Thumbnails
Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-fma-vs-thunder-power-lrp-tc-x12-3-5001.jpg  
__________________
[email protected]
TeamCRC.com Mikes-HobbyShop.com

Last edited by John Stranahan; 04-24-2009 at 03:11 PM.
John Stranahan is offline   Reply With Quote
Old 04-24-2009, 05:15 PM   #87
Tech Elite
 
hacker's Avatar
 
Join Date: Mar 2009
Location: Vic, Australia
Posts: 3,136
Trader Rating: 141 (100%+)
Default

excellent work your doing here John.

It would be good if people could send in their batteries, esc, motors for testing.

Also, not a dig at you for your selection of lipo, or the manufacturer, but the 16c lipo you are using seem ancient compared to the 35-40c lipos that are out now. I would be interested in seeying if the 35-40c lipos would make a difference to spec class's.
hacker is offline   Reply With Quote
Old 04-24-2009, 10:09 PM   #88
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

And I thought my ancient Trackpower 5400 mA-h LiPo was doing a great job pumping out that 675 W with the LRP X 12 3.5, also pumping out in excess of 220 ampere bursts.

I thought I would discuss this c rating. At 16C the Trackpower can be discharged at an average of 86.4 amperes. This means the connectors that connect the multiple cells, and the very thin conductor which is sandwiched onto each layer of the cell will not flash vaporize with this much average discharge starting in a relatively cool lab and discharged on a machine.

So how can I build a 32 C cell. I take the thin conductor sandwiched onto each layer and double its thickness, and I take the stainless steel ribbon which is about 1/2 inch wide and joins the cell ends to your terminal block and either double its thickness or double its width. I make sure the terminals in the battery can withstand 168 amps. Now when I do this I reduce the resistance from conductors in the battery a little, but just a little. Like adding a couple inches of 12 gauge instead of 14 gauge. This does not amount to much. For mod this is of little use. In fact I leave the 14 gauge for mod. The chemistry in fact may need to be changed to tolerate the additional heat from the higher discharge rate. It is not neccesarily changed in a manner that produces more voltage although that probably is a goal as well. The chemistry in the cell is what makes the car go faster. I would rather see you reporting the average voltage on a 35 amp discharge. That is what will make your stock motor sing. More volts. If you look at my battery test, the only difference between the new and old pack is the new pack delivered more volts once the motor got to peak power. The increased voltage (about .12V) was worth 50 Watts. Both packs had identical voltage at the start of the test. 8.21 V.

I agree that you will lose fewer volts in the cell connectors with a higher c rated pack, but it would be nice if it also produced more volts to start with.

I am running mod TC. My highest average amps is about 45. It might be 50 amps with my new motor and great traction. This means I am well within the capabilities of the Trackpower. Any higher and the motor will catch fire in Houston. The lifetime and performance on any new pack I try is such a gamble. I have tried many.

I did think about purchasing the 40c pack from SMC for a second pack. I am not doing it because it is 40c. I would be doing it to test the voltage on discharge, performance in the mod TC, and maybe another run on the dyno and long term performance. Give me time. My dyno is out of commission for a week awaiting an amp sensor. Matt's should be ready to fire back up in a few days.

Here is a quote from Danny at SMC to finish up this post. Comparing a lower c to a 40c pack.

"I'm not saying that it's better but were seeing that it's as good and I know it's confusing and trust me we find this strange but that is what were seeing on the track.

When we test higher C rate packs in higher amp draw conditions the higher C rate is better but in the 13.5 class it seems like theres not enough amp draw to make a difference. This means you can save 35 bucks and get a 6000 and be very competitive.
__________________
www.smc-racing.com
__________________
[email protected]
TeamCRC.com Mikes-HobbyShop.com

Last edited by John Stranahan; 05-01-2009 at 05:56 PM.
John Stranahan is offline   Reply With Quote
Old 04-25-2009, 08:49 PM   #89
Tech Elite
 
Join Date: Aug 2002
Location: Houston, Texas
Posts: 3,777
Trader Rating: 27 (100%+)
Send a message via AIM to John Stranahan
Default

Novak Sentry Dyno Motor Mount
I used parts from my dyno chassis to make a World GT car so here is a new mount that is more bare bones. It can consist of as little as a T-plate, and an Associated RC12 motor plate (that is used on the 1/10 scales as well). The top plate and center shock are probably optional. I used one because I had one extra. Instead of side shocks and springs, I installed the T-plate tweak screws. You can see the righthand tweak screw in the first photo at the front of the t-plate. The top plate can be cut away like CRC Gen X models. This greatly improves motor changing speed. I used an old partially broken CRC Pantoura Bottom Plate and drilled and counterunk two new holes to mount the T-plate. Then I sanded away the parts that I did not need. The T-plate touches the motor plate. Material forward of that needed to be removed from the pod bottom plate. Now you can just bolt this T-plate through its pivot balls onto a thin modeling plywood, old pan car chassis, or the edge of the work bench. The motion allowed lets the motor run much smoother and, I believe, adds to the precision of the measurement as no harmonic vibrations which may change from run to run are big enough now to rob power. I countersunk two holes on the reversed motor plate for flat head 3 mm screws. I removed extra pod material that might rub the flywheel on LRP motors which have a shorter shaft. I want a full contact hookup on the flywheel to the shaft to get the truest rotation.

I await my amp sensor harness from Stormer, along with a new SMC 6000 mA-h pack. But it is not the 40c one. It is 28c. I will give it a test on the dyno.
Attached Thumbnails
Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-sentry-dyno-002.jpg   Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-sentry-dyno-003.jpg  
__________________
[email protected]
TeamCRC.com Mikes-HobbyShop.com
John Stranahan is offline   Reply With Quote
Old 04-26-2009, 09:03 AM   #90
Tech Adept
 
Join Date: Mar 2009
Location: Metro New York
Posts: 139
Default

Flat Oval Lap Time Study Using Sentry Dyno Results

1. Oval Track Map with Estimated Acceleration and Braking Points:

http://www.rctech.net/forum/5718382-post76.html

According to John lap times are 4.1{s} up to 4.4{s} average on both lines. Top speed ~32{mph} on a radar gun.

2. Basic Cornering Model:

http://www.rctech.net/forum/5694203-post37.html

Oval cars on the outside line with centripital acceleraton aC = 2.2g take both half-circle segments in time t = 2.97{s} at velocity v = 22.8{mph}. This time can theoreticallly remain constant across the fastest or slowest laps since it occurs at part throttle well below peak available power.

3. Novak 13.5 on 4 Cell NiMH Torque-Speed Curve

John sent this in spreadsheet. It is not on this thread. 135{W} peak power.

4. Maximum Acceleration Model:

http://www.rctech.net/forum/5717938-post75.html

Note three velocity feedback signals in the motor curve, drag, and driveline friction. Due to reverse voltage in the motor driving force at the axle goes down as the speed goes up.

5. Graph 1 for Acceleration, Velocity, Postion

Acceleration is 1.1g's down to 0.68g's over 19{ft} straight. Velocity peaks at 32{mph}.

6. Graph 2 for Torque-Speed and Power Curves

Operating point in the motor goes from left to right over time on these curves.

7. Graph 3 for Motor Power, Power in Mass m, Estimated Drag Power

Power versus time shown with drag power negative. In this model I kept inertia and friction in the driveline at zero. Subtract drag power from motor power to get power used to accelerate mass m from v = 23 up to 32{mph}.

8. Estimated Lap Time Analysis:

Lap time = 2 x 1.49{s} + 2 x 0.47{s} = 3.92{s}

Does not include braking time so 4.1{s} fast lap looks reasonable and as power fades due to motor heat or less volts in battery 4.4{s} average laps are reasonable due to less power available to accelerate in each straight.

9. Simulator Input File

: eCar Acceleration Model
Dyno Curve & Car Input Data in Standard SI Units ----------
T /TAB/ FILE=Novak; :read torque-speed table to T
Tw = T(ws); ::[N-m] torque-speed source
Js = 4E-7; ::[kg-m^2] source inertia
G = 2.0; ::[#] gear ratio
Je = 0; ::[kg-m^2] eq. driveline inertia
J = 0; ::[kg-m^2] inertia per tire
r = 28m; ::[m] tire radius
m = 1.16 ::[kg] car mass
rho = 1.229; ::[kg/m^3] air density
Cd = 0.4; ::[#] drag coefficient
Af = 1.79E-02; ::[m^2] frontal area
b = 0; ::[N-m-s/rad] driveline damping
vI = 22.75/2.23; ::[m/s] initial velocity
tF = .47; ::[s] final time
Attached Thumbnails
Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-ovalcar01.png   Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-ovalcar02.png   Dyno, Homemade, Using a Novak Sentry Data Logger, Continued, The Experimental Thread.-ovalcar03.png  
SystemTheory is offline   Reply With Quote
Reply

Similar Threads
Thread Thread Starter Forum Replies Last Post
KARZ Calgary xrayroooahhhh Canadian R/C Scene 19114 12-01-2017 01:26 PM
CRC Battle Axe, GenXPro 10, 1/10th pan, Brushless, Lipo,4c, Road, Oval,TipsandTricks John Stranahan Electric On-Road 1776 03-01-2016 01:18 PM
Novak Sentry as Brushless Dyno mattnin Electric On-Road 132 01-29-2010 05:53 PM



Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off



All times are GMT -7. It is currently 11:29 PM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net