Unsprung mass of an f150??
Just preordered my aptera and started looking at the specs, claim was a wheel motor that does not add hardly any unsprung weight. I thought i should fact check that. Turns out its complex, the motor/break/bearing hub is 33kg(72.6lbs).
Dossier | Elaphe L1500 in-wheel motor - E-Mobility Engineering
This requires a 19" rim and tire. The claim is 17.6 kg (38.7lbs) of added weight is considered "almost nothing". This is true if you are using the motor on an SUV as intended. The issue is we have a light weight vehicle compounding the problem as well as modern EVs that have very low unsprung mass like the model 3. This is the benchmark we should at least try to reach.
Heres what i want, start with a light tire thats near its designed working load. I picked a geo metro tire. Then think like apple and make a tire wheel motor unit thats all combined.
Redesign
Basically we create a geared wheel motor with 4 rc helicopter motors.
https://www.kdedirect.com/products/kde700xf-455-g3
this motor is 1.45 lbs and 17hp peak, turns at 25,000 rpm and hits 96 % efficiency.
Next we combine the rim and hub motor into one, this allows for a far lighter design because the rim has to withstand offset loading. For brakes we attach the disc to the motor, at 25000 rpm theres almost zero torque and we have 4 so theres redundancy meaning we can reduce all unneeded weight.
As for gear life/noise/efficiency Herring bone gears are very long life, near silent and over 99% efficient. A proper designed oilless system should easily hit 10 million miles because the gears are rolling instead of sliding like normal hypoid gears. Making the ring gear from a non conductive material would be a really good move as teslas suffer from edm (electrical discharge machining). All motors with conductive bearings or gears have this issue, its just that digital motor drives cause more edm for a given frequency and use of new transistors like SiC or GaN allow 100x higher switching frequency. This means nonconductive gears and bearings are preferred.
I like gearless hub motors but we cant let them kill the performance of a good car. I don't want the ride of an old pickup truck!
I think they will use the M700 motors. The L1500 are to big.
They are using M700 judging by the power output. It's 23kg. You're omitting weight of driveshafts, wheel bearings, etc, from your calculations, which are important parts of unsprung weight and which will be lighter than the Model 3's due to generative design and lower car weight. They've already stated the performance as designed is excellent. I'd also expect the arrangement Aptera is using to have a beneficial effect on noise isolation.
And those helicopter motors and around 9 horsepower for any acceleration beyond 2 seconds. An automotive application is way out of spec for them.
Get rid of the wheel motors, disc brake more massive hub and all that with simple inboard motor and brakes and add a driveshaft for lowest unsprung weight for MUCH better handling. With regen/braking motor and low vehicle mass, could mean lifetime brakes especially if kept out of the weather. That mush mass on a wheel and the shock to the motors and all is going to be a bigger issue than a small driveshaft with CV Joints, less massive hub assy, and a more appropriate wheel/tire combination which is not dictated by the brake caliper and wheel motor.
Bit late for getting rid of the in-wheel motors in this model. That ship has sailed. The Aptera's main parts (body, motors, suspension) have been designed and tested in simulations over a year ago. All that's left to decide are relatively small parts, select some parts vendors, tweak the suspension and cooling system based on real world tests, complete the software and continue testing. We'll soon see for ourselves how their design decisions work out.
Have you seen the interview this last week with the motor company folks? Those in-wheel motors have been under development and testing for over a decade and have some impressive specs.
Completely wrong way to build an electric vehicle, just sayin'.
The weight estimates above are way off. Aptera is using a 6kg (13lb) 16" wheel with a standard 195/45R16 tire (Continental Pro Contact) weighing 17 lbs. This wheel/tire combination is 30lbs lighter than the 19-20" wheels/tires on many sports cars. They probably also save ~20 lbs unsprung weight by omitting axles/CV joints and using smaller brake rotors/calipers. So the unsprung weight ends up close to that of many relatively lightweight sports cars that have good handling and a reasonable ride. Admittedly, most sports cars would be better off with smaller wheels, but the difference is solvable with proper spring rates. In addition, hub motors have an advantage in total weight and center of mass height compared to body mounted motors.
The hub, springs and shocks a arms can all be reduced in size and weight if there is not the additional weight of a rotor, calipers motor and increased wheel size and tire weight. It would seem the savings on all the suspension would come at the cost of adding the weight of a single cv joint and lightweight driveshaft while the other cv would be sprung weight and about half the shaft itself as well. Decreased motor wiring costs and the flexing of these wires is eliminated too. increased protection of the motor from the elements and wheel dynamics. Less danger of electrical issues in an accident when the motor wiring is severed and grounded in a fender bender, and if you are worried about aerodynamics on a round shaft you could inclose it in a tube which is aerodynamic but any drag would really be small considering you already have the tie rod in the airflow.would love to discuss some choices and the 1000 mile battery is really not necessary as it was difficult to drive 500 miles a day when I was 20 let alone 50, and since 1). most people have to go to the bathroom and eat and stretch, and 2). the car charges so quickly and 3). if this is a second car, most people will take their bigger car on trips if the Aptera isnt the most comfortable/quiet/ smooth/ easy to drive car in the world and if you ever have driven small cars as I have, Bugeye, Taunus, MG Midget, Healey 100, Mini Cooper (original), Isetta, smart, MINI, FIAT, and scooters etc, drivers on the road are very blind to the smaller vehicles. Here's a free idea, instead of a light on the dash powered by a proximity sensor on the wheel spat to alert the driver of a pending crash just hook the sensor to an air horn to scare the car next to you if he encroaches into your space...
Interesting idea, though development time may delay rollout of the first vehicles.
BTW... what is the unsprung weight of a F150 pickup truck?
Why do you ask? Unsprung weight is only important when related to total vehicle weight
@paulp1232002 I was just curious... and the original post title referenced a F150, for some reason.
Not intended to come across as a troll.
The Aptera 2e used a motor in the body, like most electric cars. I see the hub motors as a huge upgrade (torque vectoring, center of mass, ease of service, increased payload weight, etc.), but you can make an engineering case either way. Putting the motors in the body would require a stronger, heavier suspension design to deal with the added sprung weight. My current car is a Mazda MX-5, so the Aptera would be my much larger, long-range trip car with 5 times the cargo space of my Miata. The Aptera is not a small vehicle; it is much wider at the wheels and almost as long as a Tesla Model 3. With the good aero, composite body, and separated front wheels, I expect it to be quieter than most cars on the highway. There are 250, 400, and 600 mile versions if you don't want the weight/cost of the 1000 mile version.
Also keep in mind that the pneumatic tires are also a suspension system, and arguably more important than the linkage system we refer to as suspension. And as far as the tire is concerned, everything except he tire tread is sprung mass.
@Eprotiva
Getting back to your original post... how about having some of the suggested small motors freewheel when all the power is not needed. I haven't done the calculations, but I suspect that only a few horsepower, thus only a few motors, would be needed to tool slowly around town while all of the motors would be needed for quick acceleration or cruising at top speed.
Intermittently turning some of the motors off when not needed would reduce the power requirements, reduce scavenger losses, greatly extend motor life, and reduce motor noise. Just thinking.
For clarity I am assuming that your original sketch shows four small motors colored in red meshing with an internal herringbone spur gear. The motors would have to be non-cogging for this extension of your idea to be most beneficial.