R/C Tech Forums

Go Back   R/C Tech Forums > General Forums > Radio and Electronics

Like Tree2Likes
Reply
 
Thread Tools Search this Thread
Old 11-25-2014, 08:48 PM   #46
Tech Champion
 
DARKSIDE's Avatar
 
Join Date: Mar 2008
Location: Nashville-Memphis
Posts: 8,444
Trader Rating: 2 (100%+)
Default

I love this thing...I havent put it down since Sunday...well worth the $$$$ and love having the simple things that make life a little easier...

Thanks EA
__________________
Myron "BATTMAN" Kinnard
Team Associated/Reedy Powered/PROTOform
2017 U.S.VTA+ Southern Nationals in Music City U.S.A.
Sept 21-24th @ Thunder RC Raceway
1172 Park Ave, Murfreesboro, TN 37129
DARKSIDE is offline   Reply With Quote
Old 11-26-2014, 04:10 AM   #47
Tech Elite
 
howardcano's Avatar
 
Join Date: Jan 2012
Location: Olathe, KS
Posts: 3,543
Trader Rating: 35 (100%+)
Default

Quote:
Originally Posted by Slapmaster6000 View Post
I just picked up one of these units. It's the one the reads to 50*. I have decided that I will make readings at 40 and 45 as well as 50, and if I have to, I can estimate 55 and 60. Sure it would be nice to actually see it, but I will manage.

Everything I race is 1s, so the voltage tested at is double. It won't run on 4.2v. Again, I will manage. EA: do you think the KV and Amps are linear to the voltage input? Or do KV and amps follow a different curve in relation to voltage? Its all relative, just curious.
Hi Brian,

I hope EA doesn't mind me chiming in here!

Extrapolating kV and current draw past 50 degrees is a challenge. The results are very non-linear; everything really skyrockets at higher timing settings. I don't know what the curve is, but maybe someone here can give us the closest mathematical approximation to it (total guess: tangent?).

kV does not change with voltage. Half the voltage will give you half the RPM, which is the same kV.

Strangely enough, free-running amp draw also doesn't change much with voltage. Frictional and hysteresis losses are approximately linear with RPM, so 1/2 voltage will give about 1/2 the power loss. Since the voltage has already been halved, the current will remain the same to give 1/2 the power loss.
__________________
Howard Cano
When race results are re-calculated using the IOF (Index Of Fun), I always win.
1993 ROAR 1/8 Pan National Champion
howardcano is offline   Reply With Quote
Old 11-26-2014, 01:13 PM   #48
Tech Elite
 
DesertRat's Avatar
R/C Tech Elite Subscriber
 
Join Date: Mar 2011
Location: Sniffin the 'Sauce Fumes
Posts: 2,571
Trader Rating: 1 (100%+)
Default

Well I hope this thing will tell me some useful information, because I just ordered mine. Maybe it will change how I run all of my stock motors, which is crank the timing to the stop and gear for lap times at mid-race.
__________________
I race toy cars for fun. If I need to explain, you'll never understand.
Current rides: Diggity DC4 Chassis #10. Losi JRX-S Type R. CRC Xi (retired), CRC Altered Ego Aluminum Chassis. Associated B4 based dirt oval late model.
WTB: Carpet racing in Arizona.
DesertRat is online now   Reply With Quote
Old 11-26-2014, 02:13 PM   #49
Team EAM
 
EAMotorsports's Avatar
 
Join Date: Dec 2001
Location: Murfreesboro, TN
Posts: 9,063
Trader Rating: 79 (100%+)
Send a message via AIM to EAMotorsports
Default

Quote:
Originally Posted by howardcano View Post
Hi Brian,

I hope EA doesn't mind me chiming in here!

Extrapolating kV and current draw past 50 degrees is a challenge. The results are very non-linear; everything really skyrockets at higher timing settings. I don't know what the curve is, but maybe someone here can give us the closest mathematical approximation to it (total guess: tangent?).

kV does not change with voltage. Half the voltage will give you half the RPM, which is the same kV.

Strangely enough, free-running amp draw also doesn't change much with voltage. Frictional and hysteresis losses are approximately linear with RPM, so 1/2 voltage will give about 1/2 the power loss. Since the voltage has already been halved, the current will remain the same to give 1/2 the power loss.
Howard,

Your information never bothers me at all! You have more knowledge about this type of stuff than just about anyone in RC so your input is always welcome! Thanks!

EA
__________________
Contact Us
Team EAM, Our Facebook
Xray | RCAmerica | Hudy | Apex RC | RC Mission | Killer Concepts | AVID | Hobbywing.
EAMotorsports is offline   Reply With Quote
Old 11-27-2014, 09:47 AM   #50
Tech Apprentice
 
Mikkel_R's Avatar
 
Join Date: Jun 2010
Location: UK
Posts: 80
Default

Hello,

Does anyone have an idea what the maximum current draw of a 13.5 with no load at max rpm and timing would be?

Thanks Michael
Mikkel_R is offline   Reply With Quote
Old 11-28-2014, 10:55 AM   #51
Tech Elite
 
Slapmaster6000's Avatar
 
Join Date: Sep 2004
Location: Edmonds, Wash.
Posts: 3,008
Trader Rating: 16 (100%+)
Default

Ah, I feel like I am getting my "geek" on with this tool. I've already filled up several sheets of paper with recordings and formulas. Howard, thanks for response with big words! I wanted to test that answer with some data on my end and wondered how I could do that. The VX1 records max rpm. Not real convenient to do, but I did it. Took 3 samples at 4.1 volts. Put an Amp meter inline on the battery. And you are absolutely correct, that amperage is relatively unchanged from 4.2 to 8.4. From my residential wiring days and the classroom training, they taught us that as voltage increases, amperage decreases if the load is fixed. Its the reason that heat or hot water run off of 240v as it will operate more efficiently and on smaller gauge wire. Apparently this doesn't carry over to brushless motor operation.

So I had a motor display 2783 KV on the GForce @ 8.3v. If I were to correct that for 4.2v, I would multiply the KV by 1S voltage, you get 11688 free spin rpm.

From the VX1, I get 9730 max rpm on that same motor. So divide max rpm by pack voltage (4.1v) and I get 2373KV.

The amperage is the same from the GForce at 8.3v and the from the amp meter at 4.1v

So there is a slight difference in KV rating. Of course where I am going with this is to see if I can go from motor A to motor B with a little calculation and come up with identical performance on the track. I know that won't happen, but its worth a shot.

I'd like to see a power or a hp #. Just because you see a big KV # doesn't mean the motor makes more power. Wattage (volt x amps) is not going to reveal anything useful, is it?

So far, I've been able to identify a bum bearing and see the results improve. I've played with rotor to sensor shimming and witnessed the changes. I guess my goal would be: gather some data, calculate that this motor with this timing with this gear should be optimal. I'm open to any suggestions at this time.

I'll take my pocket protector off now.
__________________
Stay dialed my friends!
www.slapmastertools.com
Team Roche USA
Team Orca orcharc.com
Slapmaster6000 is offline   Reply With Quote
Old 11-28-2014, 11:04 AM   #52
Tech Elite
 
Slapmaster6000's Avatar
 
Join Date: Sep 2004
Location: Edmonds, Wash.
Posts: 3,008
Trader Rating: 16 (100%+)
Default

Howard, just for show, I tested a motor every 5* starting at 25* just to see where the amps went nuts.

25* @ 0.9a
30* @ 1.2a
35* @ 1.4a
40* @ 1.8a
45* @ 2.3a
50* @ 5.5a
__________________
Stay dialed my friends!
www.slapmastertools.com
Team Roche USA
Team Orca orcharc.com
Slapmaster6000 is offline   Reply With Quote
Old 11-28-2014, 12:44 PM   #53
Tech Elite
 
howardcano's Avatar
 
Join Date: Jan 2012
Location: Olathe, KS
Posts: 3,543
Trader Rating: 35 (100%+)
Default

Quote:
Originally Posted by Slapmaster6000 View Post
Ah, I feel like I am getting my "geek" on with this tool. I've already filled up several sheets of paper with recordings and formulas. Howard, thanks for response with big words! I wanted to test that answer with some data on my end and wondered how I could do that. The VX1 records max rpm. Not real convenient to do, but I did it. Took 3 samples at 4.1 volts. Put an Amp meter inline on the battery. And you are absolutely correct, that amperage is relatively unchanged from 4.2 to 8.4. From my residential wiring days and the classroom training, they taught us that as voltage increases, amperage decreases if the load is fixed. Its the reason that heat or hot water run off of 240v as it will operate more efficiently and on smaller gauge wire. Apparently this doesn't carry over to brushless motor operation.

So I had a motor display 2783 KV on the GForce @ 8.3v. If I were to correct that for 4.2v, I would multiply the KV by 1S voltage, you get 11688 free spin rpm.

From the VX1, I get 9730 max rpm on that same motor. So divide max rpm by pack voltage (4.1v) and I get 2373KV.

The amperage is the same from the GForce at 8.3v and the from the amp meter at 4.1v

So there is a slight difference in KV rating. Of course where I am going with this is to see if I can go from motor A to motor B with a little calculation and come up with identical performance on the track. I know that won't happen, but its worth a shot.

I'd like to see a power or a hp #. Just because you see a big KV # doesn't mean the motor makes more power. Wattage (volt x amps) is not going to reveal anything useful, is it?

So far, I've been able to identify a bum bearing and see the results improve. I've played with rotor to sensor shimming and witnessed the changes. I guess my goal would be: gather some data, calculate that this motor with this timing with this gear should be optimal. I'm open to any suggestions at this time.

I'll take my pocket protector off now.
It's always fun to talk shop with you, Brian!

It sounds like something is just not right with the motor checker when running at low voltage. (EDIT: no, see below) For comparison, I just ran a ThunderPower 17.5 (timing=38 indicated) from 1s and 2s batteries. The ESC was a Novak Edge, using a Novak Smart Boost as the regulator on 1s, and the internal regulator on 2s. Here's my data:

Voltage RPM Calculated kV
3.815 9930 2603
7.57 19410 2564

As you can see, the kV was virtually unchanged: about 1.5% different, most of which I would attribute to the voltmeter accuracy. Your numbers vary by 17%, which is a little more than I would expect. But I'm not sure how accurate your voltage measurements are.

You are right, measuring power consumption at no load is of very limited value.

EDIT: Duh, silly me, the motor checker runs in sensorless mode, and you were using a VX1 for 1s testing, which I'm guessing was running in sensored mode. That explains the difference in kV. You'd get the same kV if you set the motor timing to zero.
__________________
Howard Cano
When race results are re-calculated using the IOF (Index Of Fun), I always win.
1993 ROAR 1/8 Pan National Champion

Last edited by howardcano; 11-28-2014 at 01:19 PM.
howardcano is offline   Reply With Quote
Old 11-28-2014, 01:26 PM   #54
Tech Elite
 
howardcano's Avatar
 
Join Date: Jan 2012
Location: Olathe, KS
Posts: 3,543
Trader Rating: 35 (100%+)
Default

Quote:
Originally Posted by Slapmaster6000 View Post
Howard, just for show, I tested a motor every 5* starting at 25* just to see where the amps went nuts.

25* @ 0.9a
30* @ 1.2a
35* @ 1.4a
40* @ 1.8a
45* @ 2.3a
50* @ 5.5a
The current and the RPMs both go nuts together, too... kind of like being married.

I did a quickie check of your current data. It has a reasonable fit to my guess of a tangent up to 45 degrees, but no higher.
__________________
Howard Cano
When race results are re-calculated using the IOF (Index Of Fun), I always win.
1993 ROAR 1/8 Pan National Champion

Last edited by howardcano; 11-28-2014 at 01:45 PM.
howardcano is offline   Reply With Quote
Old 11-28-2014, 06:50 PM   #55
Tech Master
 
big al's Avatar
 
Join Date: Jan 2002
Location: Olympia,Wa
Posts: 1,025
Trader Rating: 10 (100%+)
Default

Hey guys, I've long wondered what effect rotor shimming has on overall power. I realize that this thread is for the motor checker, but this thread clearly has a higher collective IQ than the majority of other threads, and I would like to capitalize on this. I've always just pulled the necessary shims to allow the rotor to find its own electrified center. Is this wrong? Any info is appreciated!
__________________
TA05 gen 1.... the real OG.
I'm not a racer, I just crush a lot.
17.5- Spec-r S1~ Scale Spec- VBC Ghost EVO ~ GT2- TA05 ~ GT3- TB03 ~ F1-F104
Keepin' it real with my M11x
big al is offline   Reply With Quote
Old 11-28-2014, 10:36 PM   #56
Tech Elite
 
Slapmaster6000's Avatar
 
Join Date: Sep 2004
Location: Edmonds, Wash.
Posts: 3,008
Trader Rating: 16 (100%+)
Default

All I can say at this point, nothing seems to be consistent. I went through a pile of 13.5's today. I would make some recordings to baseline, then make some alterations and retest. Some improve, some not and I am not even sure that I am seeing different numbers as a reduction. At this time, I am just fooling around and making numbers. I don't know if I am making good numbers, bad numbers or just different numbers. Until I can come up with a solid load test, I won't know if I am making forward progress. I can pop in a 12.3 rotor and get a higher KV rating then a 12.5 rotor. But I know that 12.5 will let me pull another tooth and be faster at the end. Yes, a 12.3 rotor should produce a higher KV, but is it making more power? Some motors I have magnetically centered the rotor and then moved the sensor board closer. Some improve, some don't. I have not come up with a cookie cutter formula for building motors. So Big Al, sorry buddy. I don't have that answer.

At least not yet.
__________________
Stay dialed my friends!
www.slapmastertools.com
Team Roche USA
Team Orca orcharc.com
Slapmaster6000 is offline   Reply With Quote
Old 11-29-2014, 01:39 AM   #57
Tech Champion
 
RC MARKET's Avatar
 
Join Date: Feb 2007
Location: HK
Posts: 6,155
Trader Rating: 12 (100%+)
Default

can choice SKYRC with bester price
Attached Thumbnails
G-Force Motor Checker-sk-500020-01.jpg  
RC MARKET is offline   Reply With Quote
Old 11-29-2014, 07:26 AM   #58
Tech Master
 
Join Date: Aug 2002
Location: Nor-Cal
Posts: 1,843
Trader Rating: 17 (100%+)
Default

Quote:
Originally Posted by Slapmaster6000 View Post
All I can say at this point, nothing seems to be consistent. I went through a pile of 13.5's today. I would make some recordings to baseline, then make some alterations and retest. Some improve, some not and I am not even sure that I am seeing different numbers as a reduction. At this time, I am just fooling around and making numbers. I don't know if I am making good numbers, bad numbers or just different numbers. Until I can come up with a solid load test, I won't know if I am making forward progress. I can pop in a 12.3 rotor and get a higher KV rating then a 12.5 rotor. But I know that 12.5 will let me pull another tooth and be faster at the end. Yes, a 12.3 rotor should produce a higher KV, but is it making more power? Some motors I have magnetically centered the rotor and then moved the sensor board closer. Some improve, some don't. I have not come up with a cookie cutter formula for building motors. So Big Al, sorry buddy. I don't have that answer.

At least not yet.
I have not been able to make a 12.3 rotor (in our current motor) make more power on either my Turbo Dyno or my Fantom. After several tries, I scrapped the idea and moved on. 12.3 = more RPM and more efficiency, but not more Torque or Watts.

As always, YMMV.
__________________
SMC ( www.smc-racing.com the only place to order your batteries online.), Awesomatix, Gonzo Paints, BN Racing

"Imitation is the sincerest form of flattery."
Advil is offline   Reply With Quote
Old 11-29-2014, 04:28 PM   #59
Tech Master
 
big al's Avatar
 
Join Date: Jan 2002
Location: Olympia,Wa
Posts: 1,025
Trader Rating: 10 (100%+)
Default

Quote:
Originally Posted by Slapmaster6000 View Post
All I can say at this point, nothing seems to be consistent. I went through a pile of 13.5's today. I would make some recordings to baseline, then make some alterations and retest. Some improve, some not and I am not even sure that I am seeing different numbers as a reduction. At this time, I am just fooling around and making numbers. I don't know if I am making good numbers, bad numbers or just different numbers. Until I can come up with a solid load test, I won't know if I am making forward progress. I can pop in a 12.3 rotor and get a higher KV rating then a 12.5 rotor. But I know that 12.5 will let me pull another tooth and be faster at the end. Yes, a 12.3 rotor should produce a higher KV, but is it making more power? Some motors I have magnetically centered the rotor and then moved the sensor board closer. Some improve, some don't. I have not come up with a cookie cutter formula for building motors. So Big Al, sorry buddy. I don't have that answer.

At least not yet.
No worries, Brian! I'm just trying to broaden my brushless horizons. I sometimes miss the old brushed days... digging in to my secret stash of brushes, and polishing comms.
I'll eventually make it to the community center, too many packages to deliver this time of year!
__________________
TA05 gen 1.... the real OG.
I'm not a racer, I just crush a lot.
17.5- Spec-r S1~ Scale Spec- VBC Ghost EVO ~ GT2- TA05 ~ GT3- TB03 ~ F1-F104
Keepin' it real with my M11x
big al is offline   Reply With Quote
Old 12-03-2014, 05:12 AM   #60
Tech Adept
 
Join Date: May 2009
Location: italy
Posts: 198
Default

Ciao AE,
i sent you a pm

Max
__________________
Touring: WRC STX
F1: WRC F-ONE 200 and 180 mm
ESC:Viper VTX10R; Motor: too many; Radio: Sanwa MT4

Don't follow me.... at the end of the straight there is the hairpin and my wall.....

Last edited by mtaddei; 12-03-2014 at 06:46 AM.
mtaddei is offline   Reply With Quote
Reply



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 04:39 PM.


Powered By: vBulletin v3.9.2.1
Privacy Policy | Terms of Use | Advertise Content © 2001-2011 RCTech.net