MemberDecember 5, 2021 at 11:20 am
Found this on Traxial, the new subsidiary of Magnax. They are developing yokeless axial flux motors. Less material, higher torque, up to 20% more range. Then this article on in-wheel motors or so called hub-motors: https://www.traxial.com/blog/lets-talk-about-in-wheel-motors/
In short: exposure to all kind of weather influences, salt, shocks and vibrations resulting in far less longevity……
What must I think of this. Is this hub motor a good idea or a bad idea in the long run?
MemberDecember 5, 2021 at 11:55 am
They made a couple videos going into the testing conducted on the in-wheel motors – they’re clearly thinking about the same hazards you are. After watching those, I’m not tremendously concerned.
They also claimed that some fancy electronics will help minimize the effects of high unsprung weight. They’re also obviously going to great lengths to reduce motor (and entire wheel assembly) weight. I’ll be very interested in what impartial reviews conclude regarding whether that challenge has been sufficiently tamed.
MemberDecember 5, 2021 at 12:32 pm
There are benefits and drawbacks to be considered and I am sure the engineering teams at Aptera and Elaphe are considering them far more comprehensively than I might hope to. Granting that part of the appeal is the novelty, I remain committed to supporting their proving the mettle of the current approach. Looking forward to seeing a lot more proofing of the ideas with the beta testing. Finally, since there are liable to be thousands of vehicles on the road before my number comes up, there will likely be all sorts of operator reviews to peruse before writing the final check for my own.
ModeratorDecember 5, 2021 at 12:45 pm
Elzo, one big advantage of the hub motors in the Aptera is the vehicle does not need the weight, the expense, nor the inherent power losses of a transmission. Nevertheless, the hub motor trade-off’s you do mention are real.
MemberDecember 5, 2021 at 12:46 pm
I have not found much mention of the interior space advantage of in-wheel motors. It seems to me that could be considerable, especially in small vehicles like Aptera or something like the proposed, smallest, Tesla. Even if it was just more frunk/trunk space.
MemberDecember 5, 2021 at 1:35 pm
For the Aptera , a powertrain combining a 1 or 2-speed gearbox with a inboard yokeless axial flux motor could offer superior efficiency in the smallest possible package.(sorry Frunk…). Off course I know that they will not change their intended Elaphe in wheel motors . But maybe eventually something to consider, especially if a four wheel Aptera is coming one day. It would also offer the possibility to decouple motors if necessary..
MemberDecember 5, 2021 at 1:57 pm
For this Old Maintenance Engineer, the advantages outweigh the Disadvantages by Quite a bit.
No Aero-Disturbing, Weighty, Twistable Halfshafts, with those troublesome, Complicated and HEAVY Constant Velocity Joints that require Maintenance. No Differential, No Driveshaft Bisecting the Cockpit, No Transmission, with all those Whirling parts and Bearings, and Relatively High Speed Bearings. Those Parts in the Driveshaft/Transmission System all have Rotational Inertia, Resisting Change (Like Acceleration and Braking).
I’ll bet that (even with things arranged as “Equal as Possible”) the Polar Moment of Inertia of the Wheelmotor vehicle is Less (Thus More Responsive in “Avoid the Mooose!” Maneuvers).
With all the Weight savings of the Wheelmotor System, I’ll bet that the Wheel, Motor and Tire Weight is Equal or maybe even less than The Bigger and Heavier Driveshaft arrangement at the corners. These APTERA Folks are Truly Following Colin Chapman’s (Of LOTUS Fame) Admonition: “Add Lightness!” – Really, Just a Repeat of How Ettore Bugatti Beat the Giants of Racing Long ago.
MemberDecember 5, 2021 at 2:06 pm
But Guy did you see this wonder of technology? Much of what you mention is not present is this config. It is a rather new and innovative approach: https://www.traxial.com
MemberDecember 5, 2021 at 2:35 pm
Still has Half-Shafts, and with 100 % Torque of Electric Motors, the CV Joints are gonna Be Big and Heavy. Ever had a CV Joint go bad? HalfShaft? Both are CatsAfterMes! Additionally, looks like they give up Thrust Vectoring – a wonderful capability.
And, Why add In something that WILL NOT Make the 100,000 Mile mark without Several Services, and A Replacement or Three.
MemberDecember 5, 2021 at 3:28 pm
What you see is the schtick that comes from the arrogance that we do things right at (insert car brand) and anyone who does anything different is wrong.
While there is a hit to handling and comfort from increased unsprung weight, the reality is that for 100 years the auto makers used heavy steel and even wood wheels and, if you’re looking at trends … the trend has been toward a dramatic increase in unsprung weight in traditional automobiles by the increase in wheel and tire diameters.
The reality is that with the in-wheel motors, while they do add weight, largely because they replace the disk brake and rotor result in a minor increase in unsprung weight if designed properly. We’re talking about less than 10-12 pound penalty for in-wheel motors; a figure that would be almost immediately surpassed by changing the tires and wheels from 16″ to 19″ rims.
Every vehicle with a suspension has ‘unsprung’ weight consisting of the tire, wheel, lower suspension arm and other components and the difference in handling, research has shown, is quite minimal with in-wheel motors which, with in general, carry about a 10-percent penalty when you figure the net difference between the suspension component weight.
If unsprung weight were a big deal, no one would ever do something like create an ornate hub cap.
In regard the extra exposure of dirt, grit, etc. and the danger of a dramatically shortened use life for the electric motor is also exaggerated.
The danger that in-wheel motors face is the same as wheel bearings basically face every day. Sure, if you hit a curb, you’ll likely be looking at a front wheel bearing in 20,000 miles if not sooner and that kind of problem is possible for an in-wheel motor … except the in-wheel motor, unlike the cheap front wheel bearing … is engineered for a greater strength than the simple wheel bearing.
Still the bearing even in an ICE vehicles wheel, is designed to keep dirt, grit and other issues at bay but, the electric motor, because it only has friction at these bearing points, promises to be more robust in repelling mother nature because it is engineered better than a $16 wheel bearing.
I think the point here is that the challenges of designing an in-wheel motor do hold the prospect of more maintenance for the part that if it were inboard, but that inboard motor also drives eight + CV joints that don’t exist on a car with an in-wheel motor. It will have the same number of wheel bearings as the in-board EV and to that you have to add drive shafts, reduction gears and a whole host of other ‘breakable parts’ that are totally eliminated by the in-wheel motor.
Ultimately, a vehicle with in-wheel motors will have significantly fewer parts than an in-board motor vehicle and can be expected to be more reliable as a result.
What those folks talking down in-wheel motors are exhibiting is confirmation bias; they’re just justifying their decisions on how they decided to build cars and since so few cars are built challenging that bias, those clutching their confirmation bias are gripping it with the same logic, will and intent as their choice to own a gun despite the statistics that shows that your chance of dying of gun violence is like 150 percent greater than someone who owns no gun.
All that aside, if the boys in San Diego have done their jobs, the few flubs ultimately discovered may be considered endearing features and some adventuresome Aptera owner will completely wear out an in-wheel motor at 625,000 miles traveled while the guy with the inboard, gloats at the 750,000 mile life of his motor.
MemberDecember 6, 2021 at 9:38 am
Still wondering why Ford ditched the idea for the F150….
MemberDecember 6, 2021 at 10:37 am
In board motors can be arbitrarily large which is very important for a truck that has to haul 10,000lb loads. Wheel motors need to be as light as possible which limits the amount of power they can handle. An Aptera is the polar opposite of an F150, it’s 1/3rd of the weight of the F150, has 1/3 of the drag, and it will never haul anything. That makes wheel motors a good fit for it’s application.
MemberDecember 6, 2021 at 11:17 am
We may yet get to see how hub motors work in a pickup truck if Lordstown Motors (or rather Foxcon) ever produces their pickup.
MemberDecember 6, 2021 at 11:26 am
You mean the truck that ran the Baja 40.
ModeratorDecember 6, 2021 at 12:18 pm
George, your post was very informative and thorough. I continue to expand my EV knowledge with contributions like this from forum members. Thanks.
MemberDecember 6, 2021 at 11:49 am
Well I read all the replies and opinions. let me state very clearly: I am not against in wheel motors, absolutely not. But seeing this recent research with the axial flux motor config of Traxial. (significantly lower weight, much higher torque and substantially increased range efficiency made me really wonder if an inboard or a near wheel motor could also be a suitable solution especially for the aptera.(three or four wheeled) I am not an expert and many of the above are, so maybe they are completely right with all their arguments and I am just a bit anxious about a motor on the outside of the vehicle with high voltage wires moving and bending and a fast turning wheel….????
MemberDecember 6, 2021 at 4:05 pm
Traxial compared with old EV motors that were both heavy and inefficient to get their claimed 20% range improvement. Modern radial flux motors are better than that. Elaphe claims a 92.5% motor/seal efficiency. The Traxial prototype got 91-96% efficiency. The power density of the Elaphe motor itself is lower, but the power density of the entire drivetrain is similar. Both Traxial and Elaphe use a larger radius than traditional radial flux motors, so torque is good on both. Elaphe does require more motor controllers in the simplest case, but the same for the IWD (independent wheel drive) case. I think most EV’s will end up being IWD with only a small electromechanical emergency/parking friction brake.