[ruckus]

Originally Posted by DavidDymaxion

I'm curious as to how you decided on BLDC. Are you worried about overheating and demagnetizing the magnets?

All motor types can be damaged by excessive heat, current, or rpm. Proper cooling is a must. Liquid cooling is the only option for serious hp/tq per pound. Current and rpm limiting is also required on all motors.

I also looked around at the various technologies and decided to go high voltage BLDC on the awd supercar (watch out Crodriver ). Induction motors don't seem to match the torque, and air-cooled brushed dc just isn't an option any more after having one. The biggest limitation (of BLDC) is the low rpm. The bigger ones tend to only go 5000rpm. You've got to have a serious overdrive or some monster tires to go 200mph at 5000rpm.

Great minds think alike. ha ha...

I think mine has a lower budget though. Currently looking at the Scott Drive BLDC which is only about $5500 for motor and controller. It doesn't match the EVO for torque, holy monsters those are some big numbers! You can see the spec sheet here: http://www.greenstage.co.nz/PDFs/Scott_Drive_100.pdf
I am seeing if they can pump it up to 640+ (mention anything about 720 or 800 and folks just look at you funny).
Cheers!

[toddshotrods]

Originally Posted by ruckus

...I also looked around at the various technologies and decided to go high voltage BLDC on the awd supercar (watch out Crodriver ). Induction motors don't seem to match the torque, and air-cooled brushed dc just isn't an option any more after having one...

I do still love brushed DC, just for certain applications - like budget drivers and drag racing. For the Model E, I ultimately want something designed more for sustained power delivery, and less environmentally sensitive, as opposed to brute force at all costs. I wish I had the budget to pursue an all-out drag car too - it would be series DC, with Warp 11HVs and a Shiva.

AC is the ultimate for general commuter purposes. Sealed, (usually) liquid cooled, high-tech, no magnets to destroy, inherently safer (controller failure), etc. I get why the manufacturers lean towards it. Not my choice for max performance, but a dragbike with dual AC20s (Tron) has dipped into the 9s on 120v...

Originally Posted by ruckus

...The biggest limitation (of BLDC) is the low rpm. The bigger ones tend to only go 5000rpm. You've got to have a serious overdrive or some monster tires to go 200mph at 5000rpm...

Agreed. I was actually a bit disappointed to find the 5K rpm limit on the EVOs. Either and overdrive and/or extremely lightweight and a numerically low final drive. With the kind of torque these things produce, at relatively low current levels, it's theoretically possible to build a really light vehicle that can accelerate really hard and fast while geared for speed - that's what we'll try first. With direct drive, <2:1 final drive, and 32" diameter tires, the math says over 200mph. Not to complicated for a salt flats setup, a bit more challenging in a standing mile.

Originally Posted by ruckus

...Currently looking at the Scott Drive BLDC which is only about $5500 for motor and controller...

Look nice - I wasn't familiar with Scott Drive. Good luck ruckus!

[DavidDymaxion]

... and then there's switched reluctance ...

Anyway, not doubting you Ruckus about water cooling but wanted to understand the why of it better. I've heard that air cooling actually takes less air flow than water cooling for cars. Looking at VW bugs and old Porsches I could believe it.

I know OEMs love water cooling, but they also love complexity and super quiet cars, too. Is water cooling really better or chosen for other reasons?

Originally Posted by ruckus

All motor types can be damaged by excessive heat, current, or rpm. Proper cooling is a must. Liquid cooling is the only option for serious hp/tq per pound. Current and rpm limiting is also required on all motors.

I also looked around at the various technologies and decided to go high voltage BLDC on the awd supercar (watch out Crodriver ). Induction motors don't seem to match the torque, and air-cooled brushed dc just isn't an option any more after having one. The biggest limitation (of BLDC) is the low rpm. The bigger ones tend to only go 5000rpm. You've got to have a serious overdrive or some monster tires to go 200mph at 5000rpm.

Great minds think alike. ha ha...

I think mine has a lower budget though. Currently looking at the Scott Drive BLDC which is only about $5500 for motor and controller. It doesn't match the EVO for torque, holy monsters those are some big numbers! You can see the spec sheet here: http://www.greenstage.co.nz/PDFs/Scott_Drive_100.pdf
I am seeing if they can pump it up to 640+ (mention anything about 720 or 800 and folks just look at you funny).
Cheers!

[toddshotrods]

Originally Posted by DavidDymaxion

... and then there's switched reluctance ...

Anyway, not doubting you Ruckus about water cooling but wanted to understand the why of it better. I've heard that air cooling actually takes less air flow than water cooling for cars. Looking at VW bugs and old Porsches I could believe it.

I know OEMs love water cooling, but they also love complexity and super quiet cars, too. Is water cooling really better or chosen for other reasons?

I've actually seen data comparing the ability of water and air to transfer heat, but don't remember anything about what I saw! IMO, the biggest advantage of water cooling is it's a closed loop system. It's really easy to control and predict - still ultimately requires airflow though. Then there's the fact that you can actually flow water inside the engine or motor, in sealed passages. That might be possible with air, but getting enough surface area (typically fins) to transfer the heat to the air would be challenging in there.

I happen to like both. I just made the decision to convert my water-cooled ICE motorcycle to electric because of the incredibly over-complicated system Kawasaki used to keep it cool. Nothing beats an old air-cooled motorcycle, to me. The fins and simplicity are integral components of what constitutes a bike, to me. I'm not ignorant to the feeling of all that radiated heat flowing off those fins on a 90-degree Midwest summer day though; and distinctly remember sticking a bare hand near the fins every so often to make sure it was still okay. I still wouldn't trade it for anything.

On my daily driver (car), water cooling is worth it's weight in gold. Watching it almost silently hold the engine at the recommended temperature, whether I'm blowing down the highway or stuck in city traffic, is a convenience that - again - I wouldn't trade for anything.

Short answer = I think "better" is highly subjective and relative...

Need to find some "scientific" data comparing the heat transfer properties of water and air, to spice up this conversation...

http://en.wikipedia.org/wiki/Heat_transfer_coefficient

http://www.physicsforums.com/showthread.php?t=293733

http://www.engineeringtoolbox.com/ov...ent-d_434.html

http://www.calculator.org/property.a...%20coefficient

[JRP3]

All cooling is ultimately "air" cooling, fluid can just be a convenient intermediary transfer mechanism. Sometimes it's worth the added complexity, sometimes it's not. Sometimes it's not even possible, as in a series DC motor.

[ruckus]

Originally Posted by JRP3

All cooling is ultimately "air" cooling, fluid can just be a convenient intermediary transfer mechanism.

A very good and correct statement.

I think the real issue here is density. Power density creates heat density. Liquid has the density to carry a large amount of heat from a very tiny space (inside an electric motor) and move it to where there is convenient large space (radiator).

Air cooling is awesomely simple and effective for low hp/lb ratios. But raise the power density and air cooling becomes lacking. All popular controllers have already figured this out.

Bigger and louder blowers can be used, but a huge amount of air (35X) must be moved to get equivalent cooling to a very small amount of liquid.

Originally Posted by JRP3

Sometimes it's not even possible, as in a series DC motor.

And thus they cannot compete in hp/lb with liquid cooled motors.

[toddshotrods]

Originally Posted by ruckus

...And thus they cannot compete in hp/lb with liquid cooled motors.

I agree with everything you said except that. In theory, I get your point. In practice, series DC is currently king of the hill. The problem is it's best done in a "burst". If you tried to sustain that level of power, with series DC, cooling would certainly become an issue. There's only so much air you can force through that restricted space.

[JRP3]

Yes, it's more a power over time issue, not so much a problem in a sub 9 drag

[ruckus]

Originally Posted by toddshotrods

If you tried to sustain that level of power, with series DC, cooling would certainly become an issue. There's only so much air you can force through that restricted space.

Absolutely correct. Like driving on the highway or climbing long grades... (here in MT we have some doozies).

How many air-cooled top-fuel dragsters are there? NASCAR? Formula 1? Nope.

air-cooled 50hp VW? yep.

It's power density = heat density. Even blown air is 'slow' to remove heat compared to liquid. And noisy noisy noisy.

Of course, sometimes you must work with what you have (I'm putting a blower on the Jag ).

Edit- some interesting figures..
The 11" Kostov brushed DC air-cooled motor is listed by Rebirth Auto at .286 hp/lb continuous (40kw).
The high-voltage version of the Scott Drive BLDC water-cooled motor is .43 hp/lb continuous (60kw). That is 50% more!

[toddshotrods]

Time to get serious about hashing out the Inhaler Model E's way forward, and the first step in that process was to get the motor in position. The plan we're experimenting with here is for a street-legal, single-seater (sort of, more on that later), hot rod. Now that I have Schism to exercise my creativity with, we can concentrate on making this little hot rod everything it needs to be to fulfill its mission. So NHRA, SCTA, SCCA - we're going to dot our I's and cross our T's.

Imagine this with a Top Fuel/Funny Car style upper cage assembly, and with roll cage tubes snaking around in every conceivable direction. The idea is to run a transmission/transfer case of some sort off the drive end of the (low RPM 13") motor, offset to the center and sending power down the center line of the vehicle to front and rear diffs. More details to come...




One of the Team members is about to graduate with a four-year degree in Industrial Design. Tonight, I told him to take a crack at this car, and show me what type of ideas he has/develops for it.