Top speed set at 110 mph; why not 125?Posted by george-hughes on August 26, 2021 at 10:13 am
The top speed for the Aptera is electronically limited to 110 mph. Given the rapid acceleration, Rousch suspension and exceptional, industry leading aerodynamics, it seems the 110 mph, while certainly adequate for road use, is probably quite a bit limited from its true potential.
It may be so far below its potential top speed as to challenge folks to defeat the limiting.
I think that 125 mph top speed would be just high enough to blunt the incentive to boost that ‘setting’ …. unless there are other reasons.
For instance, the first ‘aerodynamic’ NASCAR stock car was the ’60-70 Dodge Charger needed that big ‘wing’ airfoil on the back of the racer to keep it on the track.
Nathan Armstrong said that the Aptera became ‘more efficient’ the faster it runs, suggesting that the it may take fewer KW/mile to run 125 miles in an hour than 110 miles in an hour. That would suggest the higher top speed would benefit efficiency.
Now we all know that speed is usually a big negative in regard efficiency but still performance is a key part of the value proposition.
I’m just curious why the 110 mph figure was chosen. I mean my Spark EV is governed to a maximum of 90 mph. For many reasons I think the Aptera will be more capable at that and higher speeds but the top speed capability seems so arbitrary.
The point being, if the choice is arbitrary, I would prefer the 125 mph (or 124) over the 110 unless, of course, there is some reason like the Aptera becomes ‘too light’ to stay on the road over 110 … or you want to put 112 mph rated tires on the car because higher top-speed rating will cost more.
- This discussion was modified 11 months, 3 weeks ago by bbelcamino.
- 28 Replies
- MemberAugust 26, 2021 at 10:41 am
It could be a limitation of the motors or the cooling system, my money is on the cooling system. They are trying to use skin cooling instead of a radiator, that trades off reduced drag for cooling efficiency. If you want to race it then you’ll probably need to beef up the cooling and hack the software to remove the speed limit. They claim that right to repair is one of their objectives which I would interpret as meaning that some if not all of the software will be open source, if they do that it won’t be hard to remove the limitation.
- MemberAugust 26, 2021 at 10:42 am
I assume that this is a RPM limitation on the motors. I know with the Chevy Spark that you mentioned, that was the reason for the speed limitation (and the fact the battery would die in 5 minutes at that speed).
I personally have no desire to drive this thing over 110MPH, so I’m okay with that. In fact, I’d prefer the opposite, set the upper limit to 110, but give me a way to limit lower (which I would only use for kids if I let them drive it).
- ModeratorAugust 26, 2021 at 11:39 am
This was discussed in the previous forum – the Elaphe motors provide this limit and I assume Aptera is fine to live within those limits.
- MemberAugust 26, 2021 at 12:38 pm
George, as indicated in other posts on this thread, it is a limit based on the motor technology. Personally, I don’t care since I have never driven where it was practical or lawful to even drive 110 MPH nor would I want to be on a highway with someone that does.
I owned a Lamborghini Diablo (Yes I am ashamed now) had a top speed of 200MPH. I never drove it more than 85.
- MemberAugust 26, 2021 at 6:30 pm
Usually the car’s top speed rating is limited by the tire speed rating. Admittedly, probably the only place that I would drive 125MPH would be the drag strip. But that is one of the appeals of the tri-motor Aptera. Having a quick 1/4 mile time and higher speed shows off the power to weight ratio and aerodynamics. Obviously the Aptera’s key goals with the tires are having very low rolling resistance to increase EV range and efficiency. But it is also important to try and have grippy tires, for sporty acceleration, braking and cornering. I’m generally not a big supporter of higher top speeds, but it’s nice to have the capability to go 125MPH, as long as it doesn’t hurt Aptera’s other efficiency goals.
- MemberAugust 27, 2021 at 10:17 pm
On the old forum, there was an explanation that the motor controller can’t switch quickly enough to achieve rotation above 115 mph. If you want to go faster, you’ll need to get a wheel and tire combination that has a much larger circumference. I don’t think the wheel pants will fit that. Without them, the combination of increased aerodynamic drag and reduced apparent torque may well prevent reaching anything above 100 mph.
- MemberAugust 28, 2021 at 6:55 am
Elaphe lists the top speed of their M700 motor (Aptera uses this as the basis for the motors) at 1500 RPMs. The tire size used is rotating at 1460 RPMs when doing 100 MPH. I think to go faster you may be into higher voltage, improved insulation, higher frequencies, and number of motor poles. After the first 20,000 sell then Elaphe or Aptera may address a higher motor speed. I would like to see higher potential speed and tracking the Aptera, but at this point hoping for a productive 2022.
- MemberOctober 15, 2021 at 3:35 pm
Paul Evans on his 27August Post in this string answered the question correctly finding the answer in the old(Previous site/forum FAQ.) It is a limitation of the motor controller’s capacity to change the flux. For a great tutorial on axial flux motors and an understanding of the complexity of changing flux, Paul Evans has posted a video in the Axial Flux thread on this forum.
- MemberOctober 16, 2021 at 10:08 pm
Why not 90? I’m good with 90. Maybe even 85, remember those days where the speedos only went to 85.
- MemberOctober 18, 2021 at 3:46 am
The Aptera has to be saleable to the largest number of people.
Most people want reliability, economy, off the mark acceleration and a reasonably high top speed. The current setup seems to have an excellent balance. Plenty of acceleration 0-60mph in 3.5 seconds. Plenty of speed if you don’t want to lose your drivers license. Unparalleled fuel economy.
The car is right how it is.
- MemberMarch 3, 2022 at 2:22 am
Maybe people driving on unlimited speed roads would be interested in a higher top speed, however I think most Aptera buyers are interested in the efficiency.
- MemberMarch 28, 2022 at 12:57 pm
Since Aptera isn’t a regular car, this conversation makes me wonder if the Aptera body shape is neutral aerodynamically. Or set to be negative or positive down-force-wise. That would also greatly impact stability at high speeds.
- MemberMarch 28, 2022 at 2:52 pm
Hopefully someone will have the reference, I can’t find it in my notes but IIRC Aptera stated that with the aerodynamics design something like 20-25 lbs. of downforce at speed.
- MemberMarch 28, 2022 at 3:11 pm
You remember correctly
Thank you for this question! I look forward to getting you a more in-depth answer from our Engineers. For now, I can let you know: Our advanced aerodynamic shape and the vehicle’s ability to slip through the air have some real benefits! You barely feel semi trucks as you just slip through their turbulence; the vehicle does not generate lift at speed. For people concerned about stability at high speeds; Downforce on the rear of the vehicle is about 25 pounds at 65MPH.
- MemberDecember 22, 2022 at 5:51 pm
Yes, Steve said it in an old video interview, and that was the downforce at 65 for the alpha models. We don’t know if that was retained in the delta design.
- MemberMay 28, 2022 at 7:34 pm
Can anyone point me to some efficiency figures over a speed range above normal posted limits? Ultimately all the way to 200mph or max mechanical stock limits.
Will Aptera do periodic land speed runs just to get such data on th books, I wonder?
- MemberMay 28, 2022 at 8:16 pm
Aptera is limited to 110 mph due to wheel motor control constraints.
The information you want is not available. The Aptera is currently in the beta test stage. Real world efficiency will be documented during testing of a near production version, but certainly not above the 110 mph speed limit.
Current performance data is best available engineering projection via high resolution engineering simulation. the testing will be to verify the projected performance.
- MemberMay 28, 2022 at 8:25 pm
Understood. Can anyone point me to some engineering simulation data? Perhaps?
- This reply was modified 1 year, 4 months ago by RYAN FULCHER.
- MemberMay 29, 2022 at 1:17 am
The long answer is the Elaphe M700 motor reaches a maximum speed of 1500RPM at the voltage that it is designed to run at.
It is designed to run inside a 15-16 inch rim.
Allow me to assume a tyre diameter of 23 inches.
A 23 inch tyre has a circumference of (Pi x diameter x 25.4mm) = 1835mm.
Maximum speed across the ground is 1835mm/rev x 1500rev/minute
Maximum speed across the ground is 2752977mm/min
Or max speed is 2.75km/minute
in Km/hour this is 2.75/minute x 60 minutes = 165km/hour
Converted to miles/hour = 102.5 miles/hour.
I don’t know what motor they are actually using or the actual tyre diameter …. If you need more info, look up the correct numbers and plug them into the calculation above.
- This reply was modified 1 year, 4 months ago by Llewellyn Evans.
- MemberMay 30, 2022 at 5:28 pm
Besides the motor controller switching speed limit there are also thermal limits on the inverter, motors, and battery pack as those all generate heat and the power flow at higher speeds may run up against the Aptera’s ability to maintain homeostasis and constantly sink that heat elsewhere. You also have limits on the tires, not just on g-force stresses but also traction and braking for whatever the engineers are comfortable with for a panic stop from that speed. I’m sure you could appreciate how disheartening it might be if you try to panic stop and then melt the brakes in the process. Don’t forget that the friction pads are encased under the dome of the hub motor and probably has restricted airflow.
At least the Aptera generates some downforce at speed instead of lifting.
In any case, they’re speccing 110 MPH for now and for a very large percentage of worldwide driving scenarios that’s sufficient. I have no expectation of them testing at speeds higher than that for extended durations.
- MemberJune 26, 2022 at 8:05 am
In the USA, people can “normally” cruise at 5 mph above the posted speed limit without risk of speeding ticket.
Intra-state roads (state roads with stoplights & signs) speeds most often are limited to 55 MPH so people cruise at 60 without ticket worries.
Inter-state (federal highway system with dedicated on & off ramps to merge into high speed traffic safely) speeds are normally between 70-80 MPH so 75-85 MPH cruise is normal.
In the USA, above 90 MPH is considered dangerous & stupid unless you are on a race track. The Aptera is designed for EFFICIENCY, not for racing.
That being said, I’m my opinion the Aptera’s highway range and efficiency should be calculated, tuned and advertised for 75 MPH not 55 MPH.
- MemberJuly 11, 2022 at 6:16 am
Don’t forget that the deflection of body parts can also play into speed limits as stated in the last few videos. The wheel pants have gone through numerous iterations due to shaking, flapping or deformation.
In the video, the engineer talks about frequencies (as they increase) and not speed but I’d imagine he’s talking the results of such at speeds.
- MemberDecember 22, 2022 at 4:47 pm
Reading this older thread has sparked a question. Will Aptera be visible to police radar guns? I remember an officer acquaintance of mine telling me 15 years ago that his system had trouble getting an accurate reading on certain newer model cars because they had more rounded edges. Not to encourage the speed demons in the group, but perhaps pretty stealthy. Any patrol officers out there want to give us your opinion?
- MemberDecember 22, 2022 at 5:36 pm
Police in juridictions where I live and travel use laser speed guns/devices. Aptera will not defeat them nor do I think an Aptera will defeat radar based speed guns/devices. Easy to test the first time you drive your Aptera (Within the speed limit 😁 of course) on a road where there is a “Your speed is” device is positioned.
- This reply was modified 9 months, 1 week ago by Jonah Jorgenson. Reason: update content
- MemberDecember 22, 2022 at 5:06 pm
I must admit, it had crossed my mind. 😉 But I believe stealth is more than simply lacking hard straight edges and corners. The material itself is also designed to absorb rather than reflect EM transmissions. We will likely find out when an Aptera driver passes one of those “your speed is ___” devices which aren’t difficult to find these days.
- MemberDecember 23, 2022 at 7:31 am
I’m sure it won’t be invisible. But I look forward to testing if it affects accuracy. (At least that will be my defense).
- ModeratorJanuary 21, 2023 at 5:55 am
With the revised specs released with the Launch Edition, the top speed has been lowered to 101MPH.
- MemberJanuary 21, 2023 at 5:59 am
This still doesn’t affect my plans for how to drive the thing.