That is it for Aptera

[Frank Lee]

http://ecomodder.com/forum/showthrea...rx-7115-2.html

Good guess- pilot, motorcyclist, bicyclist. The winds are almost always my nemesis.

1:180 odds of the wind being lined up with the car...

[Ken Fry]

Originally Posted by Frank Lee

Good guess- pilot, motorcyclist, bicyclist. The winds are almost always my nemesis.

Ah ha! Explains a lot. I do those things too, but for mental health purposes, I also sail. I used to be up north, but am not now. I built this to go fast on water, where it is hard to go three times wind speed:



But you, being a cold flatlander, should take up ice boating, where doing 4,5,6,7 times wind speed is pretty standard.

Where I live, the winds are about 1 knot when I go sailing... until I get near something I could hit, at which point the winds go to 45 knots gusting to 70, and I have to jump out of the way of the lighting strikes.

The idea is that sailing makes wind your friend -- rather than the foe it is while trying to get good mileage, while bicycling, while trying to make your motorcycle go straight, or trying to land near the runway. Good theory... but of course it doesn't work: there's hot and boring and there's terrifying. Nothing else.

1:180 odds of the wind being lined up with the car...

and 1:180 odds of the wind being a direct crosswind...

[aptizzle]

Hey Ken,

If you haven't read 'The Leading Edge' by Goro Tomai, you should. The less rolling resistance claim is a sum of all of the forces, tire forces, bearing windage losses, brake drag, etc.

Also, the loss equation for a tire is not a linear equation, but a second order to try and take into account the hysteresis losses......that is, there is more loss from than 4th tire vs just three discounting the other losses mentioned above.

It is a fantastic book and Goro was kind enough to converse with me to answer questions about different equations.

SteveF

Originally Posted by Ken Fry

The Aptera claim was something like this: "...and of course three wheels have less rolling resistance than four." That's incorrect, unless they are saying that the vehicle is lighter, and therefore has lower rolling resistance.

Three wheelers (aside from the side car arrangement) pick up the additional frontal area of the third wheel, whereas the rear wheels of a four-wheel car are in the wind shadow of the fronts.

[Ken Fry]

Originally Posted by aptizzle

Hey Ken,

If you haven't read 'The Leading Edge' by Goro Tomai, you should. The less rolling resistance claim is a sum of all of the forces, tire forces, bearing windage losses, brake drag, etc.

SteveF

Hi Steve,
Tamai's concerns are only vaguely applicable to the solar racer world and not applicable at all the the world of real cars. Bearing windage and even bearing seal drag (a separate effect with a different equation) taken together are not measurable, in any realistic sense. You can prove this to yourself by jacking up a car wheel and adding a one ounce weight to the rim. The heavy spot ends up at the bottom. If you have brake drag, this is not the case, but we should not have brake drag, in the pad-to-steel friction sense. (We can have aerodynamic brake drag, from the effect of the pads trying to shear off the boundary layer -- but that is better put into the category of aero drag, and is rarely modeled -- it is not an effect that you can separate from all the turbulence around the brake calipers.)

These types of drag are more than an order of magnitude smaller than the traditional rolling resistance, which is heavily dependent on tire construction and rubber compound. A 2000 lb car has circa 20 lb of rolling resistance: a couple ounces is not enough to worry about, let alone reliably calculate.

If you look at the Wikipedia article on solar racers, you will see that there is a term that could show an effect due to number of wheels, but that coefficient is 0, and the term drops out entirely in the "usefully simplified" performance equation:



So even in the esoteric solar racer world the term drops out... but especially in the real car world, things like bearing windage have no effect in the difference in rolling resistance between 3-wheelers and 4-wheelers. (The main component of bearing drag, from ball and race deformation and skidding, scales with weight.)

You can pull a 1000 pound three wheeler and 1000 lb four wheeler across a shop floor and measure drag with a load cell or spring scale. Given tires with the same rolling resistance spec, the rolling resistance will be the same.

Regards,
Ken

[Arragonis]

Originally Posted by Ken Fry

...The real disadvantage to four wheels is that you are then a car, and are playing in a market where a $billion to develop a single new model is standard, and Aptera's 24 million in funding is a rounding error. You can expect to spend millions in crash testing.

You raise two points here.

Firstly crash testing is something worth having IMHO, it has improved safety even if it did lead to cars being like tanks for a long time before engineers got crash testing time and improved on design without adding so much weight.

And secondly if 3 wheelers worked really well, why isn't a maker out there promoting them, outside concepts of course ? If they did then they wouldn't sell. You could put this down to education of the marketplace, but lets come back to that later.

Originally Posted by Ken Fry

Three-legged stools are more stable than four-legged stools. Camera tripods are tripods for good reasons.

Stools and camera tripods don't move or go round corners. They also don't have suspensions allowing their "legs" to vary in length, or steering, or brakes. And if you put them on a slope, they tip over.

Originally Posted by Ken Fry

It's just a matter of engineering a three-wheeler to work right, as Morgan did in the 1930s.

You do know Morgan stopped making 3 wheelers in 1952 and had switched to 4 wheels for all of their new models long before then ?

Originally Posted by Ken Fry

The T-rex out-handles a Porsche.

In what way ? Do they have a GT team that demonstrates this ability ?

Originally Posted by Ken Fry

Jay Leno raved about the modern Morgan Three Wheeler.

I love it too (despite the carp engine choice), but its a toy not a practical car for most people.

This is the preserve of the 3 wheeler like the Aptera - its a toy for people who like unusual or extreme efficiency vehicles to play with. When they need to carry something, or someone, or need to go on a longer journey or need to go NOW in an emergency, then they will revert back to their normal car with a full complement of wheels, and seats, and a fuel tank that can be refilled and extend the range by 100% in minutes time and time again.

Most people don't have the space or money for a second vehicle so what they choose has to serve all purposes - commuter (1-up), family car (3 (or more) -up) and shopping getter (2-up with load). Occasionally it will be a holiday car (3 (or more) -up + load) too.

A Geo Metro (or modern equivalent) will do all of this out of the box, a TDI will do it and make better FE with some work.

If anyone wants to invest in one of these cars, I suggest putting your money into Italian Government Bonds - at least you may get 50% of your money back.

[user removed]

Aragonis, where I live in the US, I can scratch build a 3 wheel car and it is considered a motorcycle by our legal authorities. As Ken Fry posted earlier, if I add the 4th wheel the regulations change completely, including my having to provide several examples for crash testing and emissions testing before I could ever sell one to the public.

That is why I am building one with 3 wheels, as well as the fact that my scratch built prototype drive system will only require one example in the rear instead of two.

Cost to me to built one vehicle, probably $30-40K. Cost to build a 4 wheeler from scratch, probably several hundred million dollars.

One is doable, the other is impossible. I like to stick to things I can actually accomplish.

regards
Mech

[Ken Fry]

Originally Posted by Arragonis

Firstly crash testing is something worth having IMHO,

I agree. We've learned what works and the value of crash simulations.

And secondly if 3 wheelers worked really well, why isn't a maker out there promoting them, outside concepts of course ?

In the US, the cars most promoted are the most profitable ones. The manufacturers have little interest in small, efficient vehicles, because they are not as profitable as big luxurious vehicles. Nor, as demonstrated by sales numbers, is there widespread consumer interest in efficient cars. This was also the situation here in 1960. The VW Beetle (and especially its ad campaigns) changed the thinking of many people, eventually including Detroit. Gaining broad market acceptance for a three-wheeler will be every bit as difficult as introducing the VW was in 1960.

Stools and camera tripods don't move or go round corners. They also don't have suspensions allowing their "legs" to vary in length, or steering, or brakes. And if you put them on a slope, they tip over.

Of course, stools are not cars. Three legged stools can tip over. Four legged stools can tip over.

In what way ? Do they have a GT team that demonstrates this ability ?

It sustains higher cornering forces, according to road tests. The T-Rex is not a GT car.

This is the preserve of the 3 wheeler like the Aptera - its a toy for people who like unusual or extreme efficiency vehicles to play with.

Yes, it is much like a Prius in that sense. People who routinely tow boats need a bigger vehicle than a Prius. Strange as it may seem, though, many people are quite happy with the Prius, even if their neighbors have Ford Expeditions. In the US we have a category of vehicles that ride on only two wheels, and they sell remarkably well, too. We've found that no single vehicle meets the needs of all people.

Most people don't have the space or money for a second vehicle so what they choose has to serve all purposes - commuter (1-up), family car (3 (or more) -up) and shopping getter (2-up with load). Occasionally it will be a holiday car (3 (or more) -up + load) too.

This is not at all the case in the US. Many people have 2 or more vehicles in the family. We have almost the worst public transportation system in the world, so we drive everywhere. There is a strong market in all sorts of two-seaters, with the Mazda Miata, The Nissan 370Z, the Chevy Corvette, etc all being popular.

A Geo Metro (or modern equivalent) will do all of this out of the box, a TDI will do it and make better FE with some work.

While I think such cars are sensible, I am in a very small minority. 30,000 units a year is considered pretty good for our smallest cars, vs 300,000 a year (per model) for things like Honda Accords and Toyoya Camries. The pickup trucks have often sold 800,000 - 900,000 per major model.

[Frank Lee]

^Amen to all of that!

[Arragonis]

Originally Posted by Old Mechanic

Aragonis, where I live in the US, I can scratch build a 3 wheel car and it is considered a motorcycle by our legal authorities. As Ken Fry posted earlier, if I add the 4th wheel the regulations change completely, including my having to provide several examples for crash testing and emissions testing before I could ever sell one to the public.

Similar regulations are in place here, with the add on of an SVA test to make sure your car is basically safe to run on the roads. Thats how Morgan can think of making their 3-wheeler.

[Arragonis]

Just a quick tap, taking my non-towing Prius on a 500 mile round trip with all the family and luggage in it today...

Originally Posted by Ken Fry

I agree. We've learned what works and the value of crash simulations.

So why should someone selling one to someone else not have to do this ?

Originally Posted by Ken Fry

In the US, the cars most promoted are the most profitable ones. The manufacturers have little interest in small, efficient vehicles, because they are not as profitable as big luxurious vehicles. Nor, as demonstrated by sales numbers, is there widespread consumer interest in efficient cars. This was also the situation here in 1960. The VW Beetle (and especially its ad campaigns) changed the thinking of many people, eventually including Detroit. Gaining broad market acceptance for a three-wheeler will be every bit as difficult as introducing the VW was in 1960.

But they did - Metro etc. Plus of course the Yaris, Fiesta, Aveo, FIAT 500, Mini etc. etc.

Originally Posted by Ken Fry

Of course, stools are not cars. Three legged stools can tip over. Four legged stools can tip over.

So we agree, stools are not cars ?

Originally Posted by Ken Fry

It sustains higher cornering forces, according to road tests. The T-Rex is not a GT car.

Thats not handling, thats cornering G.

Originally Posted by Ken Fry

Yes, it is much like a Prius in that sense. People who routinely tow boats need a bigger vehicle than a Prius. Strange as it may seem, though, many people are quite happy with the Prius, even if their neighbors have Ford Expeditions. In the US we have a category of vehicles that ride on only two wheels, and they sell remarkably well, too. We've found that no single vehicle meets the needs of all people.

I'm going to combine this with below

Originally Posted by Ken Fry

This is not at all the case in the US. Many people have 2 or more vehicles in the family. We have almost the worst public transportation system in the world, so we drive everywhere. There is a strong market in all sorts of two-seaters, with the Mazda Miata, The Nissan 370Z, the Chevy Corvette, etc all being popular.

So these are a plaything then ? What about people in cities who don't have space for > 1 car.

Originally Posted by Ken Fry

While I think such cars are sensible, I am in a very small minority. 30,000 units a year is considered pretty good for our smallest cars, vs 300,000 a year (per model) for things like Honda Accords and Toyoya Camries. The pickup trucks have often sold 800,000 - 900,000 per major model.

The pickup is a US thing TBH, they sell some crew-cab Japanese Diesel ones (with silly names) here, but nobody buys one for home use. We manage just fine with Superminis.