open planning new car

[Occasionally6]

Originally Posted by cosmick

You can do yours however you feel safe. Me, I see that new mass produced cars are designed to have a rigid occupant enclosure with crush zones before and aft. But the bumpers themselves mustn't crush. (State law for DIY vehicles.) So I can do likewise. Besides, the thinner the steel, the more difficult to weld.

There's nothing wrong with the concept but take a look at the section and wall thickness of those cars (with safety cages). They're not even close to equivalent to 2"x2"x1/4" and they're not using that material as efficiently as a true space frame. Even more important, the lightest of those cars weigh more than twice what you will be aiming for.

The protective cage needs to react the mass of the car against the crush structure at the acceleration it crushes at in an impact. If the car is half the mass, the cage needs only be half the strength. F=ma in practice.

If you look for it you can find data on survivable rates of deceleration for human bodies. The rates vary with direction (on the body) and duration.

The tricky bit is designing a structure that will crush at the desired rate. Some racecar series have a spec. crush structure, at least for the front of the car. You might like to look for those. (The most accessible is probably FSAE.)

[freebeard]

The design I proposed is a geodesic [prolate] sphere, which means maximum rigidity with minimum mass. By varying the member or skin thickness you can tailor the crushability.

And being spherical it would tend to richocet or deflect in any impact.

[cosmick]

[cosmick]

What, you guys want a narrowed Locost? I'd like to see it, but I won't build it. Mine needs to be driveable even after a crash, maybe except for a suspension / wheel / tire issue. Still, reuseable basic core.
What I'm needing is cutaway views, or plans, of the fronts of those old race cars that were still open-wheel on narrow tires. I'll post a pic or 2 in a few minutes.

[cosmick]

In this first pic, the rear car, #30, that you can just see the front of:

The front one looks daily useful, but also too bloated, plus with too much above the driver's shoulders.

Though this might be closer to my reality, if it had the grille opening larger:

But the driver seems too upright.

[cosmick]

I hope "fair use" covers my posting these. This next one looks like a shape I can make, and this nicely:

[cosmick]

Here's where I should be in less than a year:


And this also resembles my thoughts:

But again looks to have the driver too upright.

[cosmick]

Originally Posted by freebeard

Why not go to a 19" wheel? They were used on Ford and Chrysler in the 30s and MG in the 50s (w/ knock-off hubs). I think it was 28-31 Fords that had 4x19". You could fit BMW i3 tires that would be very appropriate for the vehicles weight, and they're 155-55/19 at 26" tall.

Thank you! Excellent info!

[cosmick]

Originally Posted by ksa8907

I love good brakes as much as anyone, but I think you're going to have such large brakes with such a light weight vehicle that... well... things could get interesting in a panic brake, not to mention locked brakes are less effective. I think you may have a more effective brake setup using high-performance pads and not the "discount special".

My old car, 2000 Dodge Intrepid, could lock the brakes no problem. that was with 16" wheels, 225 section tires, single piston calipers, 3500lbs.

I understand you may want big wheels, but lets not say that massive brakes are necessary. You wanting them is a good enough reason to have them.

They're a hindrance to MPG and to handling, lots of unsprung weight. I had an S-10 loaded, the front rotors were glowing orange at the bottom of the mountain, and those were stock 10.5" x 1" single-piston floating-caliper brakes. Not the stuff of Ferraris, but I didn't lose them.
However, I also rode one of my '78 Camaros ( I've had 3 of the '78s so far )
down a more moderate canyon, and totally lost all the braking power by the time I got to the bottom. Same brakes as the S-10, except 11". And any car can lock any size brakes, once, when they're around 70 defrees F.
I've experienced both ends of the spectrum, but neither of those were capable of use on a fast racetrack, where this single-seater may well see repeated 2g decel from over 190 MPH.
Now that I've found affordable Brembo 4-piston calipers, and discovered how to find matching rotor choices, I see no reason to surrender the peace of mind. That's how it seems to me. Building adapter brackets to mount the Brembos is easy. Brembos aren't the only best brakes, but they're better than anything cheaper.

[Big Dave]

I am completely in agreement with you about either a single seater or tandem seating vehicle. Frontal area is frontal area and really cannot be finessed like Cd. Obviously this is why high performance aircraft prefer tandem seating.

Do yourself a favor: call it a motorcycle. Much less regulatory hassle. 3 wheelers are almost universally considered motorcycles.

From an aero standpoint the “tadpole” wheel arrangement (2 front, 1 rear) is better as it lets your work to a very narrow wake area.

Here’s an idea I thought would work well with the tadpole arrangement.

Tilting Motor Works - High-performance trike kit for your Harley®

OK, this was developed for a motorcycle which presents an awful frontal area, but if you lengthen out the vehicle and have the driver sit low – behind the front wheels – you greatly reduce frontal area. Now this idea supposes the rider’s weight high above the roll axis and can be leaned with minimal effort. If you lower the riding position you lose all that moment needed to tilt the vehicle. You might need a hydraulic or electrical assist.

As for fairing it in you wind up with something like this.

Decopod Tri-Pod - an art deco aluminum bodied scooter from Randy Grubb

This thing is built on a Piaggio scooter with a narrow tadpole arrangement. Again it is clearly a motorcycle and too tall but again, it can be lowered. Notice he gets pretty good plan view shaping and with a canopy and a little more length to work with you could wind up with a very low-drag shape.

Grubb did not fair in the bottom but there’s no reason you couldn’t. Grubb is an artist, not an aerodynamicist.

Still with just a 150cc scooter engine/drivetrain his vehicle is low enough drag he can go fast enough survive on LA freeways. with a 600-900 cc engine it would be stupid fast.

As for mechanicals I always thought a Honda Gold Wing would be a good start. Very reliable and even has a reverse. Build you passenger compartment in front of the bike and apply a bulkhead to accommodate the tilting front end.

Seating position depends on how tough you are. Reclining is good for racers but after an hour your butt has had it. The bolt upright position common to pickup trucks is very comfortable even with relatively firm springs. I can drive my Ford all day long and still walk afterward. The trade-off is frontal area. Make your own value judgment.