What are the famous design failure cars?

[redpoint5]

Originally Posted by freebeard

The woman his age that waited on the sidelines for seven years took him right back. Myself on the other hand...

You were in line before her?

[freebeard]

I walked right into that one. I'm not sure I think I'd want my cra-cra ex back again, maybe.

On-topic, the 1970 Evinrude Lakester:

Jalopnik.com:Meet the Car That Gave Birth to a Boat

Done by Brook Stevens, the guy the did the Weinermobile.

[Galane]

The low front shot of the Lakester shows what looks like a simple square tube front axle. The boat may have been real but I bet the rest of it was just a pushmobile.

[RedDevil]

Does the boat have doors or do you enter the car through the windows?

Fantastic idea otherwise.

[euromodder]

Originally Posted by redpoint5

Did production swap the front and rear wheels? There's no excuse for engineering a trike with a single front wheel and dual rear.

In the C5 the rider sits very near the rear axle, which puts CoG close to the rear axle.

Velomobiles with reverse-trike config tend to topple as well
There the rider -and CoG- is relatively far aft

Benefits of trikes are small, and simply don't outweigh the drawbacks when speed goes up - along with their dynamic instability .

[Bicycle Bob]

Originally Posted by euromodder

In the C5 the rider sits very near the rear axle, which puts CoG close to the rear axle.

Velomobiles with reverse-trike config tend to topple as well
There the rider -and CoG- is relatively far aft

Benefits of trikes are small, and simply don't outweigh the drawbacks when speed goes up - along with their dynamic instability .

The Sinclair cg moves forward drastically with the brakes on. It requires vigorous hiking maneuvers by the rider in an emergency. These are precluded by the new canopy.

My velomobile has 25% of the weight on the single rear wheel, just enough to permit a hard stop downhill. I could have put the cg anywhere I wanted. In general, a trike should have a lower cg relative to its width, but a fine study by Paul Van Valkenburg found that they just have a strong tendency to understeer or oversteer at the end with two wheels.

I know of no reputable source that finds dynamic instability in trikes. They have done fine at Bonneville.

[redpoint5]

All I know is that our rudimentary steering system on the electric trike we made (2HP) was scary at 40MPH or above on a standard 1/4 mile oval running track. I've experienced both the under/oversteer problems mentioned above.

The other thing is we put brakes on the single small diameter rear wheel, to reduce complexity and cost of front brakes. Getting the car to pass inspection required a lot of shenanigans, such as reducing tire pressure to minimum, and scrubbing the front wheels side to side.

Trikes are a natural design concept when the goal is to make something as cheaply and as lightweight as possible, and lend themselves to an efficient teardrop shape aerodynamically. There's simply no reason I can think of to put the single wheel in front though. Even I got that one right as a high school kid.

[freebeard]

What cornering on three wheels might look like:



Somewhere along the line I picked up the notion that as long as the rear wheel tracks behind whichever front wheel is on the outside of the curve, there's no leverage for upsetting. [right/wrong?]

[redpoint5]

Having the rear wheels mounted at the outside edges of the vehicle still adds stability. In the car above, if there were just a single center-mounted rear wheel, it would be at much greater rolling potential. It places the burden of resisting rollover entirely on the front wheels, since a center-mounted wheel just acts as a fulcrum to pivot over.

4-wheels is the superior design for most passenger vehicle transportation needs. It maximizes utility and safety, while not significantly increasing cost.

[Bicycle Bob]

Originally Posted by redpoint5

All I know is that our rudimentary steering system on the electric trike we made (2HP) was scary at 40MPH or above on a standard 1/4 mile oval running track. I've experienced both the under/oversteer problems mentioned above.

The other thing is we put brakes on the single small diameter rear wheel, to reduce complexity and cost of front brakes. Getting the car to pass inspection required a lot of shenanigans, such as reducing tire pressure to minimum, and scrubbing the front wheels side to side.

Trikes are a natural design concept when the goal is to make something as cheaply and as lightweight as possible, and lend themselves to an efficient teardrop shape aerodynamically. There's simply no reason I can think of to put the single wheel in front though. Even I got that one right as a high school kid.

My trike was made with a deliberately flexible frame, lacked an anti-roll bar function, and had a high cg. https://www.compositesworld.com/colu...mobile-history It was always very well behaved except on washboard gravel, where the rear suspension had some unplanned freedom, and the one time I accidentally ran it with toe-out. We are used to cars steering and handling easily because we usually start with well engineered parts. With a fresh sheet of paper approach, there are many more pitfalls for any number of wheels. Steering geometry is not a trivial problem at speed.

One easy way to think about the stability problem is to imagine a tilting table. At 45 deg, it simulates a 1g load in that direction on the road. The cg has to be low and centered enough that it never hangs over a line between the lowest two tires. You can plan for a bit less angle to the side, and with low power, much less to the rear. Racers like deltas because they accelerate out of corners better. Nissan recently did well with a near-trike at Le Mans.

Trikes oversteer or understeer mainly because all the weight transfer has to happen at one end. It as if one anti-roll bar was missing on a car. In a corner, the very rare diamond wheel pattern tends to put all the weight on one wheel, and none on the steering wheels, giving it a very evil reputation.

Rear wheel steering turns out to be quite stable if you just use the geometry of a regular vehicle running in reverse, but add a steering damper. The damper catches transient upsets, while the geometry still tends to self-center in a steady turn. On a delta or 4-wheeler, though, you can get trapped against a curb, unable to initiate a turn away from it.