Direct Drive to Diff E Revo Build

[aqwut]

Originally Posted by sikeston34m

The 5S1P 4000mah run lasted a little less than 20 minutes. These are older 10C cells. I've ran them pretty hard all summer in the E maxx, so I doubt they are quite putting out 4000mah anymore. I bought these batteries in Feb.

Battery temps are 120 degrees. Motor is at 100 degrees and the ESC is 115 degrees. All still well within range.

The 5S Lipo setup runs exactly like the 6S1P A123 setup. I couldn't really tell any difference as far as performance goes.

I'll try 6S 4000mah Lipo next. We should see some real gains then.

What's Amps is that motor rated for?...

[sikeston34m]

Originally Posted by aqwut

What's Amps is that motor rated for?...

Here are the specs from the Manufacturer's website.


4120/14 Specifications
No. of cells 12 - 16
4 - 5 Li-Poly
RPM/V 660 RMP/V
Max. efficiency 85%
Max. efficiency current 20 - 40 A (>82%)
No load current / 10 V 2 A
Current capacity 55 A/60 s
Internal Resistance 41 mohm
Dimensions (diameter. x lenght) 49,8x55,5 mm
Shaft diameter 6 mm
Weight with cables 320 g

The addition of the cooling fan increases it's current handling ability I believe.

[sikeston34m]

The 6S 4000mah Lipo run lasted 22 minutes. Motor is at 105 degrees. Batteries are at 102 degrees and the ESC is at 115 degrees.

I think the Monster Pro 125 would suit the 6S setup better. I believe I seen the 80amp thermal while running WOT in the grass. First time for this, I was a little shocked and puzzled.

This is harder to control. Severe Tire Swelling and a large increase in Top Speed. I believe we have surpassed the 60 mph mark. I was running on the outer road by the interstate. I can almost keep up with traffic!

It will wheelie at speed now, especially in the grass. It will spin all 4 of them on the asphalt.

I'm very impressed with the motor temps. The fan seems to be working to keep temps low. Seeing the fan as an option is alot of the reason why I decided to go with AXI. I think this motor can do well even on 7S Lipo.

I love the Revo. It handles so much better than the E maxx especially at high speed. The suspension is so much better.

[johnrobholmes]

I don't know if theory alone can explain this well, there are so many variables. When any phase is excited, delta energizes all three coils at a time whereas Wye only excites two. If kv is the same between termination styles the amp draw will be the same, and since kt and amp draw will be the same the motor torque will also be the same.


Change the magnet count or stator count- motor power will change. Change the size of the motor, motor power will change. Change the winding of the motor, motor power only changes in respect to voltage.

[sikeston34m]

Originally Posted by johnrobholmes

I don't know if theory alone can explain this well, there are so many variables. When any phase is excited, delta energizes all three coils at a time whereas Wye only excites two. If kv is the same between termination styles the amp draw will be the same, and since kt and amp draw will be the same the motor torque will also be the same.


Change the magnet count or stator count- motor power will change. Change the size of the motor, motor power will change. Change the winding of the motor, motor power only changes in respect to voltage.

Yes, there are many variables.

Total Power output also changes in respect to Amp draw. Total watts of power.

The way I understand it, on a 12 pole motor:

A Delta Winding has 4 poles energized at a time.

A Wye Winding has 8 poles energized at a time. but they are 4 x 2. 4 sets of 2. The amp draw is lower for identical turns because the pairs of windings are in series to each other. This drops the amp draw by 1.73 times along with the kv. but raises the torque by 1.73 times.

I guess what I'm really wondering is, if we drop turns to raise the kv back up in a wye winding, will we retain the added torque bonus along with the improved EMF feedback?

Here's what Lucien had to say about this when we were discussing a high kv wind on a 4045 Scorpion motor. (note: 700kv wye wind will be easier on a 4130)

Here's what I asked him:
"Would it be possible to wind a 4045 to around 800kv using larger diameter wire, such as 22 awg, using a wye termination for a 1.73 torque bonus? (Minimize copper losses and keep operating temps to a minimum?) I noticed that with a wye termination, it uses 8 magnets, 8 poles at any given time. I'm not too concerned about amp draw or total efficiency at this point. I'm just looking to have some fun and learn more about 3 phase windings and how they perform."

Here's his answer:

"It would be very tough to wind a 4045 with a Kv of 800, especially with a Wye wind. THe current 4045-10 has a Kv of 360, the 4045-12 has a Kv of 315, and the 4045-17 has a Kv of 270. These are Delta wind motors, so if you switch to a Wye, the Kv will be lowered by a factor of 1.73. A 4-turn Delta would have a Kv of about 800, but you would have to wind about 50 parallel strands to get enough copper in the slots.

The larger motors are made to run on 10-12 Li-Po cells to be able to get enough power to run the motor, and that is why they have a much lower Kv.

Think that over and let me know what you think."

I keep notes on all the information I've collected.

Now keep in mind that the 50 strands that he is referring to is 31awg. Total Cross Section area of the wind and total resistence is what we need to look at. In other words, we can use a much larger Ga. wire and eliminate the whole 50 strands thing.

I'm sure the end product of what I'm trying to put together will DEFINATELY be a high amp draw motor. But that's ok, that's what I want. Total Watts is Total power.

I want to run this on 4S Lipo or more. It's ok if it draws 100 to 150 amps continous.

I asked AXI about motor kits for the people who want to wind their own motors. Maybe they have those.

[johnrobholmes]

If you raised the kv back up to negate the wye termination, you would indeed lose the torque bonus.

Kt = 1352.4 / Kv By this formula the torque constant and kv are directly related for any and all electric motors. Like I said before, if the overall construction of the motor is not changed the power of the motor wont change. Different terminations or winds only change the voltage and amperage that the motor will produce said power. The torque curve won't change, the wattage wont change, the motor is still the same motor.

I have fought this issue with guys at RCC for a while now. People thing a 65t motor will produce more torque than a 55t motor. Geared for the same wheelspeed they will produce the same torque and power if the rpm of the motor is also the same. This means a different voltage for the two setups. On the flipside, if gearing and voltage is held constant the 55t will have more power since it spins faster and has a higher amp draw. A third example is when wheelspeed is kept the same through different gearing with fixed voltage. A 35t motor on 3s lipo geared way down will have a ton more power than a 65t on 3s lipo geared for the same wheelspeed. Lower turns, but more torque through amperage and gearing. In your case you cannot change the gearing except with tire changes, so we have one less variable to deal with.

Between two identical motors with different winding:
Same gearing, same wheelspeed (indicates same rpm at motor), different voltages to hit said rpm. If the vehicle hits 60mph it will take the same wattage no matter what the motor if vehicle weight is constant. Same power, just at different voltages.


The aspect we are really going for is a better low speed commutation of the motor, correct?. Although the motor will have the same performance capability no matter what wind or termination, the ESC might do better with certain ones.


The 4045 is a huge motor. Getting a kv so high will be very tricky.

[sikeston34m]

I understand what you're saying where different winds of brushed inrunner motors are concerned and I aggree with you completely.

Outrunner motors are different creatures with more magnets floating around. In the Delta, when the 4 magnets are being attracted to their energized poles, the other 10 magnets are just waiting their turn to do their work.

What makes me wonder, 8 magnets versus 4? My theory is, the 8 will win the tug of war.

If I'm wrong, then I just am. But if I'm right, why aren't they building them this way? For one thing, heat buildup. Wouldn't the heat be 1.73 times greater also? I'm willing to try this, since the motor in the Revo has ran so cool.

But yes, even if it's just the better low speed commutation of the motor. That would definately be a benefit worth pursuing.

[johnrobholmes]

Originally Posted by sikeston34m

Outrunner motors are different creatures with more magnets floating around.

They act no different than any other motor type. They are just permanent magnet motor and abide by the same rules as inrunners and brushed motors alike.

Even if one of us is wrong in our assumptions, it is still a great conversation! Until we get some real quantitative testing done we can't do much more than chat about it anyway.

[sikeston34m]

Yes it is a GREAT conversation. You bring things to the forefront that I haven't considered.

I would like to stick with the AXI motor because of the cooling fan that I've mounted to the rear of it. Hopefully, AXI will answer my email soon.

Even if I can just get a Delta wound 4130 that makes 700kv, it will outperform this 4120 since it's stator/magnets are 10mm longer. It will make more torque.

The Revo runs well. It's powerful and efficient. I'm happy with top speeds and even the low speed driveability. I just want some more torque with the same top speeds. Along with the extra torque will come more acceleration.

With the 4S 5000mah Lipos, RTR weight is 10lbs 3 ounces.

I think more outrunner power can be had on the 4S setup with a custom higher kv wind on the 4130 motor.

The 4130 motor would match the top speed of the 4120, possibly even more, if I had the ESC and Lipo's to put it on 8S to 10S. But even then, we are talking more weight.

I'm really considering going with the Quark 125 amp Monster Pro. I should see a performance improvement because of the increased current handling ability. It also has less resistence accross it's power board.

[johnrobholmes]

I can barely imagine what kind of power a 4030 will put down. It will be interesting to see if the gearing or rollout threshold for startup will can be changed much with the extra motor size. Getting any more speed from your revo as-is takes a taller tire,hotter wind motor, or higher voltage. I really think the simplicity will help understand the limits of sensorless motor control.

[johnrobholmes]

If you have 14 magnets you have to stick with LRK or dLRK. http://www.southernsoaringclub.org.za/

Where did you find the wire? I need some with a coating I can count on.

[sikeston34m]

Originally Posted by johnrobholmes

If you have 14 magnets you have to stick with LRK or dLRK. http://www.southernsoaringclub.org.za/

Where did you find the wire? I need some with a coating I can count on.

Is there a different magnet arrangement for this 12 pole wind? Thanks for the website, I'll check it out.

I got a 500ft spool of 200C from this Ebay seller. Looks like the last 500ft spool they had listed. I'm sure if you drop them a line, they have more.

http://search.ebay.com/_W0QQsassZswordandtreasure

[sikeston34m]

OK, Now I THINK I understand!

The winding pattern I displayed earlier is for a 12N16P configuration. 16 magnets.

I discovered this after ALOT of digging and research. Here's the wind that I believe I need to go with. Please correct me if I'm wrong.

The Wye termination will connect the ends marked "ende"

I also did some reading through a translator about the scorpion 3032 that this german guy wound. He has test results displayed there.

It is an 8 turn with a wye connection. 550kv. I'm sure that is a torque monster.

[johnrobholmes]

Yeah, that is how I am doing mine. If you have more room between the stator and back plate of the can LRK winding works, but most 12 slot hobby motors are meant to be wound dLRK like that pic shows. The scorpion motors can't be wound LRK, not enough room lengthwise.

The powercroco site is awesome, I wish my german was better.

[sikeston34m]

I wonder what size wire he is using. He does it all with only one strand!