Tricycle or reverse-trike wheel layout?
Electric motor for a super efficient tandem car
Hello, I am new here. My name is Julien, and I am building a super efficient tandem car. For now, the prototype has a CdA of around .14 (no lift), it has 3 wheels (rear drive), it weights around 600kg (passengers included), it wont have so much range beacause of the 10kwh battery and as I said this is a 2 seats car. I still have some aero analysis to do but I am close to the final design. Yet, I am looking for an electric motor wich could propulse the car. Theoretically, the car needs 4kw to reach 100km/h. So I dont need too much power and I don't want the car to be fast. I just want to show that it is possible to do efficient vehicules. The ideal power of the motor should be between 15-20 to 40Kw. Do you know of accessible engines that produce these powers ? What do you think of AGNI engines ?
Kind regards,
Julien
Kind regards,
Julien
1 - 20 of 20 Posts
Reverse-trike wheel, with a bike suspension and a single motor.
Use a Hub, in-wheel motor, they are very efficient, some have interesting functions with a proper controller: electronic reverse, Cruise Control, 3 speeds and of course Regen breaking, I'm finishing a 3-wheel 1955 Messerschmitt conversion, 10 KWh [email protected] will provide 60+MPH and 60+Mile range
What in-wheel motor do you use ? I looked after some of these, but there are very few.
Trikes are horribly inefficient - you cant package the people and the required "bits" in as small a package as you can with a four wheeler
The only advantage to a trike is that it avoids most of the safety requirements
The only advantage to a trike is that it avoids most of the safety requirements
No they are not, 3 wheels (reverse trike) reduce the quantity of friction, the quantity of turbulance, it is simpler (no need of a torque vectoring program), it is far more aerodynamic than a regular 4 wheel car (in my case) and this is cheaper. Take a look at the aptera, it consumes 5kw/100km with all the safety equipement.
Yep - the Aptera is a SCAMNo they are not, 3 wheels (reverse trike) reduce the quantity of friction, the quantity of turbulance, it is simpler (no need of a torque vectoring program), it is far more aerodynamic than a regular 4 wheel car (in my case) and this is cheaper. Take a look at the aptera, it consumes 5kw/100km with all the safety equipement.
Its what people who do not understand aerodynamics think an aerodynamic car should look like - no safety equipment and that power consumption was at 20 mph
Yet, my car has a CdA of .14, I think I am starting to understand aerodynamic. The aerodynamic is the most important thing on a car to reach low consumption. So why a reverse trike is not efficient as you say ?
Why the aptera is a scam ? It has a Cd of .12 (dont know the frontal area).
Why the aptera is a scam ? It has a Cd of .12 (dont know the frontal area).
The mere fact that you are talking about a "very aerodynamic car" and the Cd shows that you don't understand the aerodynamicsYet, my car has a CdA of .14, I think I am starting to understand aerodynamic. The aerodynamic is the most important thing on a car to reach low consumption. So why a reverse trike is not efficient as you say ?
Why the aptera is a scam ? It has a Cd of .12 (dont know the frontal area).
Which is EXACTLY where I was 25 years ago when I was asked to help with a solar racer!!
I found an excellent book on very aerodynamic vehicles - I left my copy with the School when I went back to the UK - and I have regretted it ever since
A "Streamlined" car has the "streamlines" join up at the back - this means that the drag is ALL skin effect - there is zero "form drag" -
the frontal area then becomes irrelevant - at that point its the "wetted area" that is relevant
Look at solar racers
Way back in the early days they looked like the Aptera - until the aerodynamicists got involved!!
Our "Solar Stealth" - won the "World Championship" (World Championship of American High Schools) two years running
Yes its just a "High School car" - and 25 years ago
Once you get the shape right then frontal area becomes irrelevant - but the detail bits about the edges and (most important) about where the wheels come out become critical
The problem with a three wheeler is that the single back wheel gets in the way! - it eats the space you want for the people
AND as all of the roll resistance must now be provided by the two wheels on the front they have to be further apart!!
The Aptera is 88 inches wide - 16 inches WIDER than a Model 3 - which is NOT a narrow car
The old mini which was a four seater (unlike the two seater Aptera) was 56 inches wide - a whopping 32 inches narrower !!
The .14 CdA is .15 Cd * .93m^2 frontal area.
This is a tandem, so the cokpit is very narrow. The front wheels are the same as the aptera, covered up. My car is about 1.7m wide for 4 metters long. The main probleme with the aptera as you said is this : the car is way to much big and wide beacause of the two front seats. As I said this is a tandem, so the rear wheel doesn't make any troubles exept for the trunk. The car ends up very low beacause of a duck tail (55cm), no space for other peoples.
And, I want to make a 2 seats car, not a 4 seats car.
Yes, the rear wheel has a Crr multiplied almost per 2. But if I had a 2 rear wheels the quantity of friction with the road will increase, the twin motors or the singles motors with a differential will increase the mecanic power dissipation in thermal energy.
This is a tandem, so the cokpit is very narrow. The front wheels are the same as the aptera, covered up. My car is about 1.7m wide for 4 metters long. The main probleme with the aptera as you said is this : the car is way to much big and wide beacause of the two front seats. As I said this is a tandem, so the rear wheel doesn't make any troubles exept for the trunk. The car ends up very low beacause of a duck tail (55cm), no space for other peoples.
And, I want to make a 2 seats car, not a 4 seats car.
Yes, the rear wheel has a Crr multiplied almost per 2. But if I had a 2 rear wheels the quantity of friction with the road will increase, the twin motors or the singles motors with a differential will increase the mecanic power dissipation in thermal energy.
Twin motors or an axle will lose you a lot less than the massive aerodynamic losses associated with the "Three Object" (as opposed to a single shape) of a fuselage and outrigger wheelsThe .14 CdA is .15 Cd * .93m^2 frontal area.
This is a tandem, so the cokpit is very narrow. The front wheels are the same as the aptera, covered up. My car is about 1.7m wide for 4 metters long. The main probleme with the aptera as you said is this : the car is way to much big and wide beacause of the two front seats. As I said this is a tandem, so the rear wheel doesn't make any troubles exept for the trunk. The car ends up very low beacause of a duck tail (55cm), no space for other peoples.
And, I want to make a 2 seats car, not a 4 seats car.
Yes, the rear wheel has a Crr multiplied almost per 2. But if I had a 2 rear wheels the quantity of friction with the road will increase, the twin motors or the singles motors with a differential will increase the mecanic power dissipation in thermal energy.
I.7 meters is 66 inches - 10 inches wider than a four seater mini - and at 4 meters in length its a meter longer
1.7 meters is just a wee bit narrower than my "Device" - using Subaru mechanicals
The actual width needed is not as much down to the tandem cockpit as down to the simple physics of going around a corner
If you do want to make an efficient three wheeler how about a leaning trike - one that leans into corners like a motorbike - THEN you can make it a lot narrower - and it can still be high enough to be easily visible
Anyway, do you know an electric motors wich can provide 15-40Kw (axial flux, or in-wheel) ?
Thank you
Thank you
The rolling resistance is the same, arguably higher, on a trike than a quad due to higher sidewall loads on the tires.
Rolling resistance is determined by weight and tires, not wheel count as intuition suggests you might.
If your Cd and frontal area numbers are right, you win. This is what a trike arrangement brings to the party.
As far as Aero goes, modern aero design goes beyond nere Cd and FA.
I'd run a 8kW hub motor in each of the front wheels. Maybe a third in the rear if you need acceleration performance. Coordinating torque may get interesting vs a rear drive.
You can always go chain in the back and forget hubs - you don't lose a whole lot of power in a chain drive. Problem there is you lose volume and seating flexibility due to the motor placement.
Rolling resistance is determined by weight and tires, not wheel count as intuition suggests you might.
If your Cd and frontal area numbers are right, you win. This is what a trike arrangement brings to the party.
As far as Aero goes, modern aero design goes beyond nere Cd and FA.
I'd run a 8kW hub motor in each of the front wheels. Maybe a third in the rear if you need acceleration performance. Coordinating torque may get interesting vs a rear drive.
You can always go chain in the back and forget hubs - you don't lose a whole lot of power in a chain drive. Problem there is you lose volume and seating flexibility due to the motor placement.
Yes, only Cd and frontal area are important. The force for the air to go around 3 tear drops are traduced by the drag at the end, expressed by a force (Fd grows as longer as you accelerate). Lower is the drag, easier it is for the air to circulate. The weated area doesn't count beacause it is already included in the Cd.
Theoretically, front wheel drive is more efficient than rear wheel drive. 8kw hub on each wheel is an interesting setup.
Theoretically, front wheel drive is more efficient than rear wheel drive. 8kw hub on each wheel is an interesting setup.
Tear drops and Cd/FA are 1930's aero.
Modern sub-transonic aero goes beyond what you are using.
Modern sub-transonic aero goes beyond what you are using.
The word "teardrop shape" that I used was to simplified the general shape. It is way more complexe than that.
I don't know sub-sonic aero, I only use some good old theory, and it seems it works ! I could do better if I was a professional.
However, if you had some theory about modern aerodynamic, I will read it with pleasure !
I don't know sub-sonic aero, I only use some good old theory, and it seems it works ! I could do better if I was a professional.
However, if you had some theory about modern aerodynamic, I will read it with pleasure !
I have told you the "Theory" - the FACTS about dragThe word "teardrop shape" that I used was to simplified the general shape. It is way more complexe than that.
I don't know sub-sonic aero, I only use some good old theory, and it seems it works ! I could do better if I was a professional.
However, if you had some theory about modern aerodynamic, I will read it with pleasure !
When you have a streamlined shape the frontal AREA becomes irrelevant - the wetted area is all important
Your 1930's aero was out of date by the 40's
The problem with your "three teardrops" is at the intersections - the drag from the intersections will be HIGHER that you would think
QSMOTORs are affordable and they have a broad catalog for everyone to choose. Protean has been around for many years, perhaps the best in-wheel motor for high end apps in the world, but they are close just like Tesla/OEM, they don't sell to small business I've done about 40 car conversions using both AC and DC motors retaining stock transmission, with and without clutch, using all sort of batteries. IMO the in-wheel hub motors that I've used in bikes/scooters are very efficient, there are no losses. The trike little car has not been finished yet so I can not share pros and cons. I'd use the same kind of motors (in-wheel) for small cars like the beautiful Smart. I'm not interested in conversions for racing, where most enthusiasts abuse both: motors and cells, killing them quickly, burning a lot of money. I provide day to day solutions, range and years of satisfaction. Example: most "High-End" controllers for DC Series are way too expensive, look at the Zilla, the only survivor around, their prices are really crazy, or the obsolete/extinct EVnetics Soliton 1 or the Shiva, I've seen those controllers killed many motors, from ADC to Warps to Kostovs to GE's, but they got fun for some months... instead of years.What in-wheel motor do you use ? I looked after some of these, but there are very few.
In wheel or hub motors are a sign that the company concerned does not listen to its engineers
The problem is that Torque is (very roughly) proportional to motor weight
So sensible companies like Tesla (and just about everybody) use a motor that is about 40kg and a reduction gearbox - about 8:1 - to get the same torque as a motor weighing 300 kg
Added to that a hub or in wheel motor is unsprung weight !!!! - to be avoided if at all possible
For a bicycle hub motors are fine - for a car they are bloody usless
The problem is that Torque is (very roughly) proportional to motor weight
So sensible companies like Tesla (and just about everybody) use a motor that is about 40kg and a reduction gearbox - about 8:1 - to get the same torque as a motor weighing 300 kg
Added to that a hub or in wheel motor is unsprung weight !!!! - to be avoided if at all possible
For a bicycle hub motors are fine - for a car they are bloody usless
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