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 Post subject: Super braking
PostPosted: Sun Oct 30, 2005 23:02 
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Normal vehicle braking is limited by the coefficient of friction between tyres and tarmac. the weight of the vehicle increases traction but also requires more traction to slow it down. these effects balance out.

It's possible that there would be a significant road safety benefit if we could have an emergency braking system that had brief higher performance.

Here are a few bonkers ideas to get the ball roling:

* A glue spray onto the tyres
* Upwards firing rockets that provide a downforce
* Forwards firing retro rocket
* Explosive launched ground anchor
* Parachute or other air brake
* Some sort of very high friction pad that drops down on a ram under the vehicle

Anyone got a realistic method for briefly increasing max braking effort?

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PostPosted: Sun Oct 30, 2005 23:06 
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If the car was appropriately equipped, and front wheel drive, it could engage reverse and go full power? With electronic control and overall speed sensing (NOT wheel linked, at least not *driven* wheel linked), this could declutch when speed was down below a certain speed.


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PostPosted: Sun Oct 30, 2005 23:08 
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Roger wrote:
If the car was appropriately equipped, and front wheel drive, it could engage reverse and go full power? With electronic control and overall speed sensing (NOT wheel linked, at least not *driven* wheel linked), this could declutch when speed was down below a certain speed.


still limited by tyre-road friction tho'


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PostPosted: Sun Oct 30, 2005 23:13 
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ed_m wrote:
Roger wrote:
If the car was appropriately equipped, and front wheel drive, it could engage reverse and go full power? With electronic control and overall speed sensing (NOT wheel linked, at least not *driven* wheel linked), this could declutch when speed was down below a certain speed.


still limited by tyre-road friction tho'


Ever seen drag racing? The blanket factor between tyre and tarmac after a burn out on the spot is dramatically higher.


Last edited by Roger on Sun Oct 30, 2005 23:14, edited 1 time in total.

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PostPosted: Sun Oct 30, 2005 23:14 
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dont like the glue.. sounds messy

like the rockets of course.... downside is presumeably single use, how do you decide when they're needed? get the driver to press a button? .. or rely on the looming collision detection/mitigation/avoidance systems to tell you?

dont think ground anchor or chute are very practical.

high friction pad is probably doable,.. well not even high friction, getting some more rubber on the road would help. if you designed the linkages right (leading arm type) it would lift the vehicle slightly, hence increasing the load on it hence lifting te vehicle a bit more etc. (like self servo on drum brakes).

if we're going for more rubber on the road, automated dropping of tyre pressure would have some effect.


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PostPosted: Sun Oct 30, 2005 23:15 
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Roger wrote:
ed_m wrote:
Roger wrote:
If the car was appropriately equipped, and front wheel drive, it could engage reverse and go full power? With electronic control and overall speed sensing (NOT wheel linked, at least not *driven* wheel linked), this could declutch when speed was down below a certain speed.


still limited by tyre-road friction tho'


Ever seen drag racing? The blanket factor between tyre and tarmac after a burn out on the spot is dramatically higher.


bit tricky to lay down rubber ahead of yourself isnt it ? ! :?


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 Post subject: Re: Super braking
PostPosted: Sun Oct 30, 2005 23:16 
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* Upwards firing rockets that provide a downforce
This is probably the most realistic (just like a drag racer). I can't think of anything better.


* Forwards firing retro rocket
Imagine the situation where a pedestrian steps out in front of such an equipped vehicle: if aimed at the pedestrian, the resulting jet-blast needed to bring 2 tonnes to a quick halt, would send them flying at much greater velocities than the car was previously travelling at - this not being particularly advantageous when they land against brickwall type objects!!!! :D

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 Post subject: Re: Super braking
PostPosted: Sun Oct 30, 2005 23:21 
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smeggy wrote:
* Forwards firing retro rocket
Imagine the situation where a pedestrian steps out in front of such an equipped vehicle: if aimed at the pedestrian, the resulting jet-blast needed to bring 2 tonnes to a quick halt, would send them flying at much greater velocities than the car was previously travelling at - this not being particularly advantageous when they land against brickwall type objects!!!! :D


:rotfl:

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 Post subject:
PostPosted: Sun Oct 30, 2005 23:23 
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I was thinking my "reverse gear thrust" would come in if the brake pedal was pushed "beyond full" - a bit like an auto-kick down - if a collision was in the offing. It may be that the thing would act as a preemptive airbag and only cut in if the ABS was already dib dib dibbing and the car's in-built front radar detector realised that it wasn't going to make it.

I like the idea of it being augmented with a drop in tyre PSI and further rubber. The further rubber should ideally be behind the front wheels so that it hits dry tarmac even in the wet, cleared by the front wheels. These pads would have to be independently sprung of course and maybe also electronically controlled dynamically to avoid any unexpected steering effects.


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 Post subject:
PostPosted: Sun Oct 30, 2005 23:31 
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ed_m wrote:
Roger wrote:
ed_m wrote:
Roger wrote:
If the car was appropriately equipped, and front wheel drive, it could engage reverse and go full power? With electronic control and overall speed sensing (NOT wheel linked, at least not *driven* wheel linked), this could declutch when speed was down below a certain speed.


still limited by tyre-road friction tho'


Ever seen drag racing? The blanket factor between tyre and tarmac after a burn out on the spot is dramatically higher.


bit tricky to lay down rubber ahead of yourself isnt it ? ! :?


Perhaps I need to research this a bit. I thought the idea was to get the tyre sticky so that it laid down rubber "better" as it accelerated. In fact, I think the laying down of rubber during reverse gear thrust (I like this name!) would be a disadvantage wouldn't it?


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PostPosted: Sun Oct 30, 2005 23:52 
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We have already discussed the system fitted to some Mercedes cars where the system detects emergency braking and increases system pressure to the maximum possible within tyre grip limits. This was developed because it turns out that most people don't push the brake pedal hard enough in an emergency (for various reasons both physical and psychological). So the biggest improvement we could make would be - fanfare - driver education and training. No technology needed.

I know this isn't the point of this thread but it just tumbled out of my brain. :wink:

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 Post subject:
PostPosted: Sun Oct 30, 2005 23:53 
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ed_m wrote:
dont like the glue.. sounds messy


There might be something water soluble - and a bit of glue would be much nicer to clean up than a bit of blood.

Or there might be a compound that would dry and flake or powder in a minute or two.

The glue spray is my favourite just now.

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 Post subject: Re: Super braking
PostPosted: Mon Oct 31, 2005 00:04 
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smeggy wrote:
* Forwards firing retro rocket
Imagine the situation where a pedestrian steps out in front of such an equipped vehicle: if aimed at the pedestrian, the resulting jet-blast needed to bring 2 tonnes to a quick halt, would send them flying at much greater velocities than the car was previously travelling at - this not being particularly advantageous when they land against brickwall type objects!!!! :D


More seriously... suppose it was mounted under the rear of the car with some sort of diffuser. We might be able to get quite a bit of assistance without jets of hot gas going beyond the front bumper.

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 Post subject: Re: Super braking
PostPosted: Mon Oct 31, 2005 00:21 
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SafeSpeed wrote:
More seriously... suppose it was mounted under the rear of the car with some sort of diffuser. We might be able to get quite a bit of assistance without jets of hot gas going beyond the front bumper.

There must be some velocity of gas from the front of the car for the retro effect to work; the diffuser will instead absorb this force from the jet thus applying a forward force to the car, hence negating the jet’s effectiveness – it’s rather like blowing into the sail of your boat to try to get yourself moving when at sea.

I think a good compromise would be to have the retro jet angled 45 degrees up, it will still achieve 71% extra downforce and 71% retro (deceleration) force - without 'blowing' pedestrians away :hehe:

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 Post subject:
PostPosted: Mon Oct 31, 2005 00:42 
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Easy. 3ft. long spike mounted under car and hinged at the back (but VERY firmly fastened to the hinge, which is also VERY firmly built into the car). Maybe this is what you meant by the "anchor" idea.
When applied, the front of the spike is (forcefully perhaps) dropped to the road, where it immediately gouges an anchor point. However, if it really works that well, then any car occupants would experience VERY (too?) rapid deceleration, or maybe the car would somersault :o

The deluxe version would have the hinge mechanism mounted on a telescopic rail that provided a few precious feet of deceleration distance.

Cartoon version: longer spike to pole-vault over the obstacle :lol:


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PostPosted: Mon Oct 31, 2005 00:43 
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Ok, I'll go along with the 45 degree angled jet, say laid along the "C" pillar lines of a typical hatchback car. When you actuate you get (say) 50% reverse thrust and 50% increased downforce, which would work particularly well as it would be at the rear of the car and cause a "squat" effect rather than a nosedive, bringing the rear tyres into play much more than normal.

Clearly this would need to be linked up to an EBA type system so that the newfound additional grip would actually be exploited.

Next problem is the propellant. Can any solid or liquid fuel ignite and produce controllable thrust within the sort of time frames required? I say controllable as I've got visions of the system being activated at low speed and continuing to propel the car backwards once it's stopped, like some sort of demented sorcerer's apprentice. :twisted: I've already discounted any form of turbine or jet, as clearly it's little use waiting "a few seconds" for it to spool up! How much energy can a small but ultra-high pressure air tank contain? <thinks: SCUBA tank?????>

Some other issues that spring to mind are what happens if it is inadvertedly deployed in normal driving? What if only one side "fires"? What happens if the driver has a need to go from full emergency braking back to full acceleration, eg if it now looks like there might be a chance of the car emerging from the sideroad actually passing behind?

Anyway, back to the general brainstorming thing, here's a further idea:

In dry conditions vehicle braking is pretty damn good, the much more important issue is driver response time. Really, the time braking performance becomes a major issue is when it is compromised by surface conditions, usually water.

So what can we do to make the wet road behave more like a dry one. At the moment the only thing we do is cut tread into tyres. How about (in ascending order of barminess?)...

1. v-shaped deflector "plough" that is deployed in front of each tyre, to fling standing water out of the way, so tyre gets a wet road to bite on, but not actually standing water.
2. some form of rotating sponge that gets similarly deployed, but actually absorbs the water off the road, extracts it from the sponge and flings it clear of the wheel, so tyre gets a moist road instead of a wet one,
3. Infra-red panel and / or flamethrower in advance of the contact patch, to vaporise anything left by 1 and 2.

With all three we could cross standing water with racing slicks, confident that if we need to stop we can get full dry weather performance.

I do so like brainstorming!!! :lol:

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 Post subject:
PostPosted: Mon Oct 31, 2005 00:51 
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Just had a crazy thought (and don't forget some brilliant inventions started out as "off the wall" ideas).
What if you were to build 3 or 4 standard airbags UNDER the car? Any clever mechanical / dynamics bods know how this would affect decelleration?


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PostPosted: Mon Oct 31, 2005 00:58 
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Standard airbags have holes in so all you'd get here is .. poof!

I'm warming to the glue idea.

The problem with all anchor type solutions is that if we achieve more than about 2g, you're probably better off taking a collision and deploying airbags.


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PostPosted: Mon Oct 31, 2005 01:08 
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Roger wrote:
Standard airbags have holes in so all you'd get here is .. poof!

And if they didn't all you'd get is "upforce", which is surely the opposite of what we are looking for!
Quote:
I'm warming to the glue idea.

Me too. Wonder if we could sprinkle a magic powder that would react instantly with any water on the road and erupt temporarily into a sticky foam to drive over? Sort of like a high-tech sanding box?
Quote:
The problem with all anchor type solutions is that if we achieve more than about 2g, you're probably better off taking a collision and deploying airbags.

Agreed. The more I think about it the more I'm leaning towards improving wet weather braking. What if we could aim to end up with 1g braking effort under all conditions?

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PostPosted: Mon Oct 31, 2005 02:22 
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supertramp wrote:
... When applied, the front of the spike is (forcefully perhaps) dropped to the road, where it immediately gouges an anchor point. However, if it really works that well, then any car occupants would experience VERY (too?) rapid deceleration, or maybe the car would somersault :o
...

Cartoon version: longer spike to pole-vault over the obstacle :lol:

It's been done... In the early 1900s when car brakes were primitive in the extreme, some cars were fitted with what was called a "Sprague Brake" - which was in essence a pointed pole fixed under the car and hinged at or near the back axle. In an emergency it could be dropped to dig into the road. Unfortunately, if the car had "run away", the normal result of dropping the Sprague was to cause the car to pole-vault violently and fire the occupants out. Not one of the world's greatest safety inventions.

Hmm... I wonder if it was invented by Mr Gatsonides's father? :lol:

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