[luminarycrush]

Hey Ruckus,

I'm interested in the group buy. I rode in Peter Thompson's 914 this past weekend with the 40kw BLDC motor and was impressed, even with the Chinese controller which seems to have some issues.

I have a completely disassembled 914 that has been waiting for a motor/controller decision to start the conversion process. I also will be helping a friend convert a Karman Ghia so I'll probably use the same general system for both cars (probably different sized motors).

I tried to send you a PM but it's not showing up in my 'sent messages' folder so I wanted to make sure you received my inquiry.

Thanks - Jason

[Bowser330]

updates please

[ruckus]

Sorry, hay season on the ranch here in Montana. Been on the swather and still have a lot to bale and pick up before the rain hits...

I think we are at the 5-motor price, but have yet to achieve the 10-motor price. Still, that means shipping/customs for free. not bad.

Will update soon...

[Jan]

Hi Ruckus, which motor is it going to be? Or are you going to get several different motors?

[ruckus]

Originally Posted by Jan

Hi Ruckus, which motor is it going to be? Or are you going to get several different motors?

Hello,
Each person can choose the motor they want from the list for the group purchase. I am going with the 55kw continuous rated motor for my testing. The 600+v controller is still in development. When it becomes available I will order the 60kw high-voltage motor for testing. By then I should have a decent amount of data at 400v for comparison. They are really the same motor with a different gauge wire and number of wraps used in the winding.

I will probably test it direct drive to the rear axle to get a feeling for how that kind of setup works. A 1990 Eagle Talon will be the test vehicle.



Ultimately, though, I will be moving to AWD and full race chassis. Something like this:


or this:


If you watch some of Crodriver's vids it is clear that AWD is needed to put the torque down without undue wheel spin.

Cheers

[Bowser330]

i am not sure if you were inferring this method, however, you could hook motor up to the AWD transmission in the Talon and use the transmission to help you study the power delivery at different ratios e.g. in different gears....in the end you may end up wanting to keep the transmission, the only reason Tesla and the other OEMs get away with one is the ability of the motors to spin 10,000+rpm, where as most of the motors available to the DIY conversion market can only spin up to 5000rpm.

[Jan]

Originally Posted by Bowser330

...the only reason Tesla and the other OEMs get away with one is the ability of the motors to spin 10,000+rpm, where as most of the motors available to the DIY conversion market can only spin up to 5000rpm.

I prefer a motor with max 5000 rpm but with double the torque of the 10000 rpm motor. It's probably haevier, but easier to use. No extra gearing down.

[ruckus]

Originally Posted by Jan

I prefer a motor with max 5000 rpm but with double the torque of the 10000 rpm motor. It's probably haevier, but easier to use. No extra gearing down.

Couldn't agree more. Except the heavy part. If the exact same motor is wound for a lower rpm it will simply have more torque. This means better acceleration for the same weight (plus or minus a beer can).

Originally Posted by Bowser330

...in the end you may end up wanting to keep the transmission, the only reason Tesla and the other OEMs get away without one is the ability of the motors to spin 10,000+rpm, where as most of the motors available to the DIY conversion market can only spin up to 5000rpm.

Yes, fully agree, I am very hip to trannys and transfer cases in all their forms. However, the Talon sitting in the driveway has neither. But is IS free and just sitting there whispering in my ear each time I pass by...

The top speed with 5000 rpm is 105mph and with 6000 rpm is 125 mph. We will find out what it will do... Don't forget they DO make larger tires.

Don't worry, the Talon (DSM) is just a motor/controller/battery test rig. If a component passes muster it will be potentially employed in the AWD race platform which will use a tranny/transfer unless it ends up dual motor/dual diff. But that is off-topic for this motor thread. I will post build threads when the time is right.

A direct differential drive is actually a good tester since almost every car out there is direct in 4th gear. This provides a somewhat comparable power/torque test condition among various different vehicles. (if you also consider tire radius, axle ratio, and vehicle weight/drag).

Under continuous high-mph conditions (Le Mans, Daytona, Mille-Miglia etc.) I am fairly confident the stock (55kw) Scott Drive would eat a stock 11" brushed motor (35kw) for lunch. However, once you get into highly-modded and race-prepped vehicles using dry ice, turbo cooling fans, and other advanced cooling methods, then all bets are off. The best prepped vehicle will win, regardless of design configuration.

Cheers

[Coulomb]

Originally Posted by Jan

I prefer a motor with max 5000 rpm but with double the torque of the 10000 rpm motor. It's probably heavier, but easier to use. No extra gearing down.

Except that if you want the same top speed, you have to use a diff (or overall fixed transmission ratio) that is higher (less tall, numerically lower ratio), which will bring your torque down to the same as with the 10 000 rpm motor. But if you are retaining or using a multi-speed transmission, I agree it's easier to use a motor with a top speed around 5000 to 6000 rpm.

If you achieve the higher motor torque by winding it for double the number of poles (e.g. 2-pole to 4-pole, or 4-pole to 8-pole), the weight should not change significantly.

[ Edit: this last statement is wrong, as Major points out in a few posts. I should know better: "Motor torque is approximately proportional to size". Say it again, Coulomb, and keep repeating it till you don't forget! ]

[ruckus]

Well, before we get into a high vs. low rpm war, please everyone consider that power is power, regardless of the rpm. A low-rpm motor needs to be geared up, and a high-rpm motor needs to be geared down.

The real question is what works with the engineering already present in the vehicle? Most vehicles are designed to be happy between 2000 and 4000 rpm, so that is the optimum rpm the electric motor should be wound for as well.

The faster you spin a tranny, the more hp is lost. This is a simple fact. Not only is more hp lost at high rpm, but there is increased mechanical wear and increased likelihood of failure (not to mention the noise pollution).

Low-torque, high-rpm motors are just not well suited for conversions. If you could get 6:1 or 8:1 differential gears then they would be fine if yo wanted to put up with all that racket).

Think of it this way. In a brushless motor the only wear component is the bearings. If you take the same bearing and run it a double the rpm you will get half the life (actually much less). That is not a winning proposition.

This fact is very well quantified in hydraulic pump/motor literature where they chart bearing life against rpm. It decreases dramatically with increased rpm.