Direct Drive to Diff E Revo Build - RC-Monster Forums

sikeston34m · 12.01.2007, 10:12 PM

Quote:

Originally Posted by BL_RV0

i wouldnt get the 125b, it has the same overheating issues that the 80b does, unless you do the mod, but that voids your warranty.

I'm pushing alot of power through the 80b, and I know there is some seperation from the heat sink inside. I've had it apart a bunch of times.

The Monster Pro 125 has a higher rating because it has more FET's on the power card. This also means less resistence, so more power flow.

I really like the Quark line, mods or no mods.

johnrobholmes · 12.02.2007, 08:53 AM

I switched to 5 strands of 22 awg wire. Crikey it is hard to wind tight! Took more than an hour for one phase of the motor, only 2 left. With all this work I will leave all 6 ends open so I can switch from D to Y termination on the fly. Just so happens that a 8D on 3s is almost exactly the same rpm as an 8Y on 5s (wattage should be the same too). Time to test this kv VS startup torque thing.

sikeston34m · 12.02.2007, 05:42 PM

Quote:

Originally Posted by johnrobholmes

I switched to 5 strands of 22 awg wire. Crikey it is hard to wind tight! Took more than an hour for one phase of the motor, only 2 left. With all this work I will leave all 6 ends open so I can switch from D to Y termination on the fly. Just so happens that a 8D on 3s is almost exactly the same rpm as an 8Y on 5s (wattage should be the same too). Time to test this kv VS startup torque thing.

I've been doing some more research about this on my own.

Delta has 1.72 times the kv as Wye Termination but draws 1.72 times the amps.

Wye has 1.72 times the torque as Delta, but draws 1.72 times less amps.

SO, correct me if I'm wrong, but to make the Wye termination put out the same wattage and KV, You must use 1.72 less winds on the stator.

There are two big advantages of the Wye termination IMO.

1. More Torque! 1.72 times as much torque. I think this is mainly due to the fact that 8 magnets/poles are in use at any given time, rather than 4 magnets/poles on the Delta.

2. More EFM feedback to the ESC at lower rpm's. I just discovered this today as I was reading about this. The Wye should run/start MUCH better in a Car/Truck Application.

I'm thinking about taking a short cut to the entire winding/experimenting thing. AXI motors says "If you have a custom motor in mind, do not hesitate to contact us."

I think I'm going to ask them if they can do a custom wind for me. I want a 4130/8 with a Wye Termination. I want to shoot for 700kv and with a Wye Termination, this should be a BEAST!

johnrobholmes · 12.02.2007, 06:15 PM

That is correct, a delta terminated motor needs 1.72x the winds to match a Wye terminated motors KV. The D termination has less resistance since there are two parallel current paths in any phase.

I think you are getting a bit ahead of yourself on the torque though. While yes you will have 1.72x the torque with a Wye termination (per amp), the amp draw will go down. If you don't change your voltage the torque (and wattage) will actually be lower since torque and amp draw are directly proportional. If you volt back up to the same motor speed your torque will again be the same, but at a lower amp draw since the kt is of higher value with a lower kv motor. A 1200 watt motor is a 1200 watt motor, and the torque curve is almost perfectly linear for a permanent magnet motor no matter what the wind or termination.

The increase in EFM feedback should be correct though, plus higher voltage motors give better feedback anyway. Although the motor doesn't have higher torque, the ESC should see the motor better in effect making more efficient use of the torque.

It really wouldn't be hard to take a motor apart and just change the termination.

sikeston34m · 07:24 PM

Quote:

Originally Posted by johnrobholmes

That is correct, a delta terminated motor needs 1.72x the winds to match a Wye terminated motors KV. The D termination has less resistance since there are two parallel current paths in any phase.

I think you are getting a bit ahead of yourself on the torque though. While yes you will have 1.72x the torque with a Wye termination (per amp), the amp draw will go down. If you don't change your voltage the torque (and wattage) will actually be lower since torque and amp draw are directly proportional. If you volt back up to the same motor speed your torque will again be the same, but at a lower amp draw since the kt is of higher value with a lower kv motor. A 1200 watt motor is a 1200 watt motor, and the torque curve is almost perfectly linear for a permanent magnet motor no matter what the wind or termination.

The increase in EFM feedback should be correct though, plus higher voltage motors give better feedback anyway. Although the motor doesn't have higher torque, the ESC should see the motor better in effect making more efficient use of the torque.

It really wouldn't be hard to take a motor apart and just change the termination.

I feel like there must be a good torque bonus if only based on the fact that it's pulling on 8 magnets with each phase instead of 4.

Yes motor timing will be more accurate especially at low speeds.

I've thought about taking one apart and changing the termination, but let's look at an example.

The 4120/14 that I'm running is 660kv. By using the same 14 turn winding and changing the termination, I'm cutting the kv to 384kv. Even though torque would be increased by 1.72 times, the 384 kv isn't enough to do the trick. Unless I wanna go HV. Hmmmmmmm.........there's an idea!

The is where more strands and less turns comes in.

I plan on consulting with the winding guys at AXI about this. Let's see what they say.

sikeston34m · 12.02.2007, 08:03 PM

John, there is alot of valuable motor building information here.

Just trying to pass along some tools that I plan on using.

http://www.bavaria-direct.co.za:80/m...motor_info.htm

sikeston34m · 12.02.2007, 08:08 PM

One thing that I thought was very interesting is at the bottom of that page. It's how to figure the kv of any motor that's already built.

"Drive your motor with a power drill.
Measure RPM and voltage generated.

Kv = RPM / voltage"

I spun the 4130 at 930rpm with a drill. It was feeding 2.9 volts into a volt meter on the AC scale.

930rpm/2.9volts= 320kv

Pretty close to the factory rating of 305kv! Which maybe with the load of the motor, the drill wasn't quite spinning at 930rpm. I think this is a good quick method though.