Brake enhancer for emergency stopping

You should be asking this question in automotive fora, but I think the answer would be that there is no such substance.

An existing ABS system would be able to do the same thing--so far none has.

Good luck.

Forget the robotics--the search for that magic fluid would be a life's work in itself.

I respect your idea but I think the best posible way to stop a car in the shortest distance possible with the best handling posible will be a mechanical solution instead of a chemical solution.

I would be amazed if such a chemical can exist without being really bad for the environment.

The first thing you have to do is understand how a tire grabs the surface. Hint, it isn't what you learned in Physics 101. Tire grip is due to the energy that the tire uses to deform around the surface of the road. Think of the road as a sandpaper surface and the tire grabbing into the nooks and cranies.

Any goop is going to fill the nooks and cranies and decrease traction for a while, probably longer than the top will take.

How about a great light or flashbulb that can heat three quaters of the tire's surface up to optimal temperature?

Serious R/C car racers have some stuff that they put on their tires for more grip. Other than that it exists, I don't know anything about it. Check in one of their forums, Google, etc.

JM

Can you recommend a particular forum?

Not true. If you throw sand on an icy road, you can stop faster. So clearly such a substance exists: sand. But I am looking for something that also works on non-icy roads.

I am not sure I understand what you mean. Are you saying that an ABS does not decrease stopping distance? That is a suprising assertion.

The system I am envisioning would work in addition to an ABS. Brakes work using friction between the brake pads and the drum or disk. But in modern vechicles that is not what is limiting stopping power. The limit is the friction between the tire and the road.

Well, it doesn't have to be a fluid. One idea I thought about was to deploy small spikes, like children's jacks, but smaller, so they would embed in the tire but not far enough to puncture it, and made of very rigid material, like tungsten-steel. As the tire rotates, they would poke into the road surface, and increase the friction. This would work better on softer road surfaces (such as asphalt) and less well on hard surfaces (concrete), but we have a lot more asphalt roads than concrete. The vehicle's computer should have information about the road surface, and could choose not to deploy under some conditions.

Do you have any particular ideas in mind? I would like to hear them.

In modern vehicles the stopping power is limited by the friction in the tire-road interface. So any improvements fall into one of two categories:

1. Increase the tire-road friction
2. Something else

In the second category, I thought of a system that would fire a piton into the road surface, and then reel out a cable that would slow the vehicle. There are several disadvantages to this: It would damage the road surface (although much less than the damage to the vehicle if the collision was not avoided), and the deployed cable would be a safety hazard if not removed immediately. So the driver could not just detach from the cable and drive away.

Just look in all of them with "automobile", "car", "racing", etc in the title until you find one that is busy and seems to have people with technical knowledge.

If you throw sand on a non-icy road then you do _not_ stop faster. You are asking for an all purpose substance. If you find, patent it, and do even a half-assed job of marketing it you will become remarkably wealthy.

I am saying that if your magic substance existed an ABS system could decide when to apply it.

Yup.

This is how a studded snow tire works. They work very nicely on ice but they don't work as well as non-studded tires on dry pavement.

Doesn't work that way in the real world.

Drag chute, retrorocket, all kinds of ways to do this if your vehicle is at Bonneville with no other traffic for miles around. Now, consider your piton--the 18-wheeler behind you hits it, blows out a tire, control of the vehicle is lost, and instead of smashing the front end of your SUV on the Pinto in front of you you get clobbered from behind by 20 tons of liquid oxygen or whatever he's hauling.

You need to make up your mind--do you want to work on a robotic system or an alternative to convetional braking systems? They are different fields of expertise.

On icy roads, you can use sand. On clean, dry roads, tires work really well, and any sort of grit or adhesive will become a lubricant.

In summer, you might try using a jet of compressed air or other gas to clean the road ahead of the tire. This could clear away water and sand to prevent hydroplaning and slipping.

-- Matt

Don't they put some kind of high-friction goo-stuff on those huge back tires and/or the road just in front of the tires on dragsters? (this is to insure greater acceleration rather than greater decelleration, but it's effectively the same thing) A possible problem with this might be a conflict with "should be cheap" as in drag racing they're always willing to spend substantial money to make the difference between winning and losing.

This brings up the idea of having some continuous sensor(s) evaluate (using methods beyond the scope of this post) the condition of the road, and when a "stop car fast" request is made, immediately decide what, if anything, to spray or release onto the tires or road to aid in friction. This gets by your point 3), in that it won't make the conditions worse, because it won't be released on inappropriate road conditions.

Also, it only has to last 1/4 mile.

They run the car thru a pool of water, and then put 500 HP or so to it while the front brakes are on. The water lets the tires get spinning and soon there is a layer of melted rubber. Which gets the tires up to proper temperature for maximum grip.

More extreme than the heater I posted earlier upthread.

Nothing besides tire rubber on asphalt is going to be better.

The only way I can envision would be additional tires, or maybe a belt like a treadmill, tucked in the undercarraige of the car that deploy to increase the surface area of the road contact surfaces. This apparatus would then either have to have some kind of resistance to kinetic energy (flywheel, torsion) or a dynamic braking system too slow the vehicle.

Could be messy for the home mechanic working on his vehicle on jackstands and it deploys while he's under there!! :-(

-Will

No "high friction goo stuff". They used to use bleach during the burn-out, which is just heating the tires by spinning them. Now they use plain water.

The thing is, friction is proportional to the normal force, not to the contact area. All else being equal doubling the contact area does nothing. In the real world changing the contact area in either direction may increase, decrease, or have no effect on the frictional force depending on the details of what is happening at the contact surface. If the braking device used a different rubber compound optimized for stopping and not compromised to provide long service life it might allow for somewhat shorter stops, but I doubt that the gain would be really large.

I'm a bit puzzled as to what a flywheel or regenerative braking system would bring to the party, though, other than more weight and complexity in a system that is already too heavy and too complex.

DRIVE SLOWER, the you wont need it

Thinking about this, I think you're working the wrong end of the problem. The collision avoidance system should prevent a situation from arising such that increasing the static friction would be needed. This means making an ongoing assessment of the road surface and conditions and making allowances for a disparity of braking power between the CAS-equipped vehicle and the one ahead, as well as looking ahead of that vehicle and analyzing the traffic pattern to assess the possibility that it will collide with an immobile object.

Something that would IMO be highly beneficial would be an aft-looking analysis as well--stopping successfully in heavy fog for example is not the end of the game--to be safe you also need to clear the road surface completely as otherwise you risk being hit hard by something coming from behind (this is not an uncommon kind of collision in areas where heavy fog is frequent), and I think it would be worthwhile for the CAS to either do that or make a recommendation to the driver that it be done.

Now, someone may cut your CAS-equipped vehicle off and then manage somehow to stop suddenly, but in that case there would be only a narrow range of distances over which your increased-friction device would be of benefit--this would be an infrequently occurring scenario if your programming is good.

I think a more interesting problem is "edge of the road" analysis--seems to me your system should have "hit the ditch" as an option and that requires that it be able to assess the viability of the ditch as an escape zone.

As to how it's going to handle some idiot playing "chicken", I don't know if anybody has every come up with a proven survival strategy for that game.