Okay... but if I understand your illustration correctly you're showing this motor mounted directly on the axle, so there is no gearing and the drive ratio of motor to wheel is 1:1. You can't choose the gear ratio when you have no gears.High inertia and torque should only affect the axle and speed is determined by motor RPM and gear ratio.
Although the sheet's file name says "750", it's actually for the 750R... I assume it's the 750R that you want.The motor I am considering is Yasa 750 http://www.lightswitchracing.com/YASA-750-Product-Sheet.pdf and the battery is two of these Lone Star 100V in series.
Synchronous permanent magnet motors are preferred over induction by every current manufacturer of production road-going EVs (now including Tesla Motors, starting with the Model 3), so I don't think the PM design should be a surprise. I'm pretty sure it makes a good motor.i was hoping it would be an AC induction motor, but looking at the patent,
https://encrypted.google.com/patents/EP2773023A1?cl=und , it appears to be a permanent magnet motor. These would probably make a better generator than a motor due to the high back emf generated
Yes, at low voltage the motor hits the power-limited (rather than torque-limited) mode at a relatively low speed... but it keeps working at that constant power to the top of it's operating range. This is not substantially different from an induction motor. The Tesla Model S motors hit this transition about one-third of the way up their speed range.At 200 V the back emf causes the torque to start rolling off at only 625 RPM and the maximum power is on the order of 56 kW.
I agree that this "pancake" and axial-flux motor design is intended for high-torque and lower-speed applications; this makes it appropriate to directly drive the dragster's axle, but if a reduction drive were used a more common lower-torque/higher-speed radial-flux motor would be a more obvious choice.If you have to add a gearbox then you probably lose any possible benefit to the axial flux package.
That's an interesting observation. I wouldn't usually look to the Board of Directors for technical expertise in a corporation. Whatever one might think of the technical qualifications and motivations of the people involved, this isn't a startup offering vapourware - they appear to have built motors which have worked in at least project (concept, prototype, race) cars by legitimate manufacturers.Their website had no information about the motor technology or any details, and i'm suspicious of any technical abilities when their board has engineers who started companies to trade in carbon credits. Two thumbs down for me.
Yes, every controller to drive this motor - like every AC motor including induction designs - will be a 3-phase variable frequency inverter. I'm pretty sure that tropes is looking for more specific information than this.As far as electrical controllers, you could probably find a used variable frequency inverter that would work to drive the motor.
Thanks - all I had found was the 18" minimum for Jr. Dragster (not Comp). To make the best of the limited torque, I assume that you'll run the shortest allowed tire... and you're still going to use less than 2/3 of the motor's speed range.The final ratio is determined by tire diameter. Minimum tire diameter for NHRA Jr Comp class is 22"
Sorry, that wouldn't be me. Hopefully someone in that business will notice this discussion.Now could you build for me an inverter/controller that would handle 400V 600amps. I would prefer heat sink rather than liquid cooled.
A valid concern (rotational inertia stores energy which then isn't kinetic energy of the car's speed), but a Jr. Comp run takes about 8 seconds (fast for a car down the 1/8th mile, but not much time to spin up a motor), so I don't think accelerating the motor will be a concern.There are large axial-flux motors used in oil well drilling that provide lots of torque, not sure about how the acceleration or speed would play out for a dragster due to the high inertia of the pancake design.
True, but kennybobby is just running through the physical reality of the work to be done by the motor, which depends on the change in velocity. The 130 mph was the result of an axle speed which I calculated for 18" tires, but with 22" tires, so it's not relevant... and I realize that even 110 mph is not necessarily the trap speed.Drag racing is about E.T. not mph. Jr Comp cars are restricted to 6.90 seconds or slower based on either an e.t. dial-your own or heads-up basis; breakout rules apply. In qualified events, no racer can qualify quicker than 6.900. Any racer running faster than 110.00 mph at any time during an event is disqualified
If you try to calculate elapsed time based on a constant power level, you will also need to define a maximum rate of acceleration (or tractive force), since otherwise you will be assuming infinite (and thus impossible) acceleration at zero speed.Most Jr Comp cars weigh 550 - 600 lbs. plus driver.
Calculate E.T.: 755 pounds and HP of 114 (85 kW)
Fortunately the car with driver is about two-thirds of the expected 1000 pounds, so this 533 lb-ft of torque, ideally producing 581 pounds of force at the road, is good for about 0.7 g of acceleration... and 10% better with a change of tires to 20" tall. That's not going to be enough... which is the second problem with the constant-acceleration calculation.At 400 Arms the motor makes 553 ft-lbs of torque off the line, so on 22" tires that would provide about .5g acceleration.
Yes. Motor rpm, which is shaft rpm in this configuration.Are you referring to the motor RPM ?
I had calculated roughly 2000 rpm assuming a smaller tire than 22".2000 RPM, 22" tire, 1:1 final drive ratio = 130mph
It might be worth a tire change, since with the direct drive you've lost the ability to trade off between torque and speed with gearing.The shortest allowed tire is actually 20" but the Jr Comp car I am looking at is wearing M&H 9.0 x 22.0 -13 tires...
... the Jr Comp car I am looking at
...weighs about 600 lbs. with a Suzuki engine without driver.
Realistically, how will the weight of the motor, controller/inverter, batteries, and wiring, compare with the weight of the engine and drive (chain and sprockets or whatever) and fuel system?Most Jr Comp cars weigh 550 - 600 lbs. plus driver.
Calculate E.T.: 755 pounds and HP of 114 (85 kW)
I'm thinking of a calculator which is specifically for electric vehicles. If I can find it again, I'll share a link to it.Drag racers have been collecting data for decades. I have at least four sites favourited on my laptop. They are however meant for ICE vehicles and most are for 1/4 mile.
That's the easy part. Motor torque multiplied by gear reduction (1 in this case) divided by tire radius is force (under 600 pounds in this case). Force divided by mass is acceleration (2/3 of one g in this case).The Yasa motor produces about 550 ft/lbs. of torque. I was hoping this would be enough to launch the dragster.
Sure, you can think of the fuel tank plus engine as the power source, transmission and final drive as the transmission system. Then in the electric version the battery is the power source, the motor and whatever gearing you use is the transmission system. There are other ways to think of the equivalency, but that one can work well for weight and packaging.One obstacle I had to overcome 10 years ago when converting ICE to electric is the idea of replacing the engine with a motor. I now think more about replacing the engine with a battery and adding to the drive train with a motor.
Well, larger motors do generally produce more power, if they are set up to run at their optimal speed. This is why my concern with a configuration that runs a motor designed to go to over 3000 rpm at only 2000 rpm and less. It will never take full advantage of the motor's capabilities.I realise that large motors do not produce more power; higher voltage does. Now, as you point out, I must deal with the thought of losing torque by eliminating gear reduction.
I am thankful for all members of this forum who have done the math and lead me to Plan B which is to revert back to a design which requires some gear reduction.http://www.lightswitchracing.com/round.MOVEliminating gearing doesn't so much lose torque, as lose the opportunity to choose your tradeoff between torque and speed. Since available motors are all capable of higher speed than the car's wheel speed (even at the end of the run), hitting the desired tradeoff will always require some gear reduction.