Farfle joins the MENS club

[Farfle]

About to start winding, and have a few questions. the origional wind made 480 rpm at 48v, so 10 rpm/v. Im aiming for 30rpm/v, the original wind was 31 turns of 2 paralell strands of 18awg in delta. so, to get about 3x the kv, ill need 12 paralelled strands with 5 turns 6x less turns to get 3x the kv as the stator is twice as wide. BUT, that's in delta, so in wye that would be 3 turns of 20 paralelled strands that's a phase wire that's 5awg im worried about the lack of resistance and inductance this beast will have.

[Biff]

Did your controller have field weakening (or over speed) before?

If not you might want to increase your turns back up to 5 turns

If you want around 3000 RPM maximum and plan on using field weakening controller, like the Sevcon Gen4, I would target spinning 2500 No-load without field weakening, if you are planing on running the Sevcon Gen4, the max nominal voltage you will have is 104V, and you want to run that if you want the best performance out of that controller, so I would target 2500RPM/104V is about 24RPM/V or only about 2.4x the KV of the original Motor.

To follow your original math, you had 31 turns, and you doubled the thickness of the stator so you would need 15.5 turns to get the same KV, you want 3x the kv so 5turns, then switching to Wye decreases by 1.73x which would end up with 1.8x the Kv of the original Motor

4 turns WYE shoudl give 2.2x the Kv of the original Motor

3turns WYE should give 3x the Kv of the original Motor.

Based on that I woudl go with 4 turns.

Lets look a the torque numbers though and see what you really want
In other threads you can find that Kt (Nm / A) is equal to 9.549/kv , so a 4 turn WYE,double wide motor with 2.2x the original KV would in theory have 22RPM/V = 0.434Nm / A. I know that RMS amps and DC Volts and stuff are all confusing, but from what I have experianced that conversion works pretty good at predicting Torque / Phase RMS apms as reported by a Sevcon controller. So a Size2 with 250RMS phase amp limit gives 108Nm of torque. With a 20" OD rear tire, you would get about 120kph at 2000 RPM, which sounds about right, maybe a little high for most of the kart tracks and be fun on the road. So you would want a 2:3 ratio on your gearing so 3000 motor RPM = 2000 Wheel RPM, that would multiply your torque at your rear wheel by 3/2, so rear wheel torque is 150Nm. With a 20" OD tire 10"radius (0.254m) that woudl be 590N of force to the ground .. 590N is about 130pounds force. I imagine you and your bike will weight something like 260lbs all up, so that would only give you about 0.5G acceleration. at 1/2G acceleartion your theoretical 0-60 time is around 5.5Seconds, which isn't bad, but it won't make you crap your pants which I think is what you are going for. To do that you would need to upgrade to a larger controller, or go to more turns, maybe 5, and sacrifice power available at top speed, or gear a little shorter which would be easier on your motor / controller, but would certainly limit your top speed.

All this math was done quickly so I could surely have made a mistake .. please check it over and tell me what you think.

-ryan

[Emoto]

Farfle
ive only wound 1 rc motor and its been a while but this might be worth a look http://www.bavaria-direct.co.za/models/motor_info.htm

[Farfle]

Farfle
ive only wound 1 rc motor and its been a while but this might be worth a look http://www.bavaria-direct.co.za/models/motor_info.htm

Thanks man, there are some useful calculators in there.

[toolman2]

Did your controller have field weakening (or over speed) before?

If not you might want to increase your turns back up to 5 turns

If you want around 3000 RPM maximum and plan on using field weakening controller, like the Sevcon Gen4, I would target spinning 2500 No-load without field weakening, if you are planing on running the Sevcon Gen4, the max nominal voltage you will have is 104V, and you want to run that if you want the best performance out of that controller, so I would target 2500RPM/104V is about 24RPM/V or only about 2.4x the KV of the original Motor.

To follow your original math, you had 31 turns, and you doubled the thickness of the stator so you would need 15.5 turns to get the same KV, you want 3x the kv so 5turns, then switching to Wye decreases by 1.73x which would end up with 1.8x the Kv of the original Motor

4 turns WYE shoudl give 2.2x the Kv of the original Motor

3turns WYE should give 3x the Kv of the original Motor.

Based on that I woudl go with 4 turns.

Lets look a the torque numbers though and see what you really want
In other threads you can find that Kt (Nm / A) is equal to 9.549/kv , so a 4 turn WYE,double wide motor with 2.2x the original KV would in theory have 22RPM/V = 0.434Nm / A. I know that RMS amps and DC Volts and stuff are all confusing, but from what I have experianced that conversion works pretty good at predicting Torque / Phase RMS apms as reported by a Sevcon controller. So a Size2 with 250RMS phase amp limit gives 108Nm of torque. With a 20" OD rear tire, you would get about 120kph at 2000 RPM, which sounds about right, maybe a little high for most of the kart tracks and be fun on the road. So you would want a 2:3 ratio on your gearing so 3000 motor RPM = 2000 Wheel RPM, that would multiply your torque at your rear wheel by 3/2, so rear wheel torque is 150Nm. With a 20" OD tire 10"radius (0.254m) that woudl be 590N of force to the ground .. 590N is about 130pounds force. I imagine you and your bike will weight something like 260lbs all up, so that would only give you about 0.5G acceleration. at 1/2G acceleartion your theoretical 0-60 time is around 5.5Seconds, which isn't bad, but it won't make you crap your pants which I think is what you are going for. To do that you would need to upgrade to a larger controller, or go to more turns, maybe 5, and sacrifice power available at top speed, or gear a little shorter which would be easier on your motor / controller, but would certainly limit your top speed.

All this math was done quickly so I could surely have made a mistake .. please check it over and tell me what you think.

-ryan

that is good info right there, it may appear hard going but well worth a few re-reads to soak it up, quite impressive to begin with just a couple of bits of data about a motor that doesn't exist yet and end with a good ballpark 0-60 time -it all adds up right to me. fine work biff!

[Farfle]

Thanks much, 4 turn wye it is. Im starting winding, so will see how many paralleled strands I can cram in this motor.

[Farfle]

After attempting to wind for 6 hours, and actually winding for 2 hours, I am 1/6 done. SOOO much faster than the dual pie.
also, my method on turning a 400 foot spool into a 15 paralell strand.

[Biff]

Looking Good. What paper are you using? Have you fire-tested it? I like to hold a lighter up to a sample and see what it does. All the paper I have used barely supports fire once started, and usually has some sort of melty-plastic type drops.

-ryan

[Farfle]

its calandered 410 nomex I got from bigmoose, which has been pretty impervious to anything so far.

[Farfle]

19 hours in, im getting better at this:

[AussieJester]

Good stuff Farfle makes my hands quiver just looking at it, used twin stand on my turnigy ca100 rewind, leather glove on one hand puling the wire taught, I don't look forward to future rewind that's for sure...I like the method you have used to terminate the ends of wires, looking sharp'.

KiM

[Farfle]

Haha, thanks mate. Turns out that the stator is now too wide to fit in the can, end turns are bigger than I figured. So I am making some shims that will space the can out further. Going to be a tight squeeze into the bike now.

[nechaus]

very very nice,
its inspiring me to build a race bike, and actually spend the time and make something that looks reasonable and rides well

damm im keen to see some videos of this thing running...


Something about your bike design that i just love... i like the color to
100% respect for doing the windings yourself, you did such a good job.
Id feel like i would need to do a week of fingering buckets of sand to toughen up my fingers

So what will the final weight be of the bike loaded up ? how much does the motor weigh?

[nechaus]

Are you going to use pedals as well ? haha
is it an ebike or an emotorbike

[Farfle]

very very nice,
its inspiring me to build a race bike, and actually spend the time and make something that looks reasonable and rides well

damm im keen to see some videos of this thing running...


Something about your bike design that i just love... i like the color to
100% respect for doing the windings yourself, you did such a good job.
Id feel like i would need to do a week of fingering buckets of sand to toughen up my fingers

So what will the final weight be of the bike loaded up ? how much does the motor weigh?

Thanks man not sure about the all up weight, should be somewhere around 110 pounds, as for the motor, it's no lightweight right now it's about 30 pounds, but doesn't have phase wires or hall sensors/wires yet

[Farfle]

here's some pics on a somewhat pessimistic scale.

[neptronix]

That thing is going to rip. can't wait for video.

[Farfle]

I got the last set of assembly screws in place. There's thirty two 3 mm screws that hold the can halves onto the magnet rings, and the magnet rings together. Murphy must not have been watching though, because we didn't break a single 2.5mm bit, or that itty bitty little tap, or have the bit wander and drill thru a magnet, or anything else that could have gone wrong. all thats left to do is wire the halls, and the phase wires, and it will be ready. now just have to wait for the laser cutting shop to get the rear sprocket back to me, and will be rollable under power!

[Farfle]

all wired up and ready to go, 3 strands of 6 awg out the axle and halls are all wired up. All there is left to do is modify my motor assembly tool, and get the ventilation going, but hopefully will get it assembled today.

[dbaker]

Beautiful work

[Farfle]

IIIT LIVES!!! kinda... in fits and starts...

[Miles]

Well done! Looking forward to seeing it spin.

[hydro-one]

So , have you got it on yet????

[Farfle]

Working on it. Motor mounts are yet to be made, and I have no idea when the sprockets and chain are going to show up.

[Kingfish]

I like the forced perspective - it's larger than life

Fingers-crossed/Excited for you, KF