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Comment: Re:Short yellow lights are a safety hazard (Score 1) 507

Actually, the mass of the vehicle doesn't really significantly impact the stopping distance on reasonably level grade.

See here.

Actually it does. There's a vastly different co-efficient of friction between the road and a semi vs. a car. Tyre compounds, center of mass and probably the most significant difference being how well the suspension keeps the tyres in contact with the road. The heavier the "unsprung mass" (all the components between the dampers/springs and the road) the more intertia and the less quickly the suspension will keep the tyres in contact. Trucks have very heavy suspension in comparison to a car, making them worse at stopping.

Comment: Re:There's nothing spectacular about the Rotary (Score 1) 359

by mk2mark (#37685752) Attached to: Mazda Stops Production of the Last Rotary Engine Powered Car

I beg to differ, rotary engines are easily the best design of the non reciprocating pistons and I don't think you're being fair to them.

Even if it was altogether true that they needed rebuilds that often it's still better than otto engines were doing at the same period in their development. Ditto for the fuel efficiency. While it is true that the higher output turbo engines can need rebuilds that often, I've heard of the naturally aspirated engines regularly running to 200-300k miles without a rebuild - and these motors still make around 100bhp/litre so they're reasonably stressed engines.

Comment: Re:Golf Diesel (Score 1) 576

by mk2mark (#34012794) Attached to: Mazda Claims 70 mpg For New Engine, No Hybrid Needed

I take offence to this. There are plenty of cars both in Europe and the States (and beyond) that are low powered by anyone's definition. The choice is there, and a reasonable statement is that a lower powered car will be cheaper. People can choose these cars if they wish. However, if they don't why does this amount to gross denial - and who are you to dictate someone's requirements to them? It's a perfectly valid argument that a more powerful car makes certain situations safer - this doesn't amount as you say to someone arguing that they can't drive on the freeway.

Also a Euro is a unit of currency, when you call me one it conjures an image of a die-hard republican spouting about commies - except the polar opposite. Although no less ignorant.

Comment: Re:How? (Score 1) 317

by mk2mark (#33262662) Attached to: Cambered Tires Can Improve Fuel Economy

A certain amount of negative camber is actually beneficial in the situation you describe. As you hit the brakes, the front of the car squats, which compresses the suspension which changes it's geometry. Generally under compression, this geometry change results in positive camber, or the tyres tops pointing outwards. If the tyres were cambered negatively beforehand, under squat the tyres approach a parallel state with the road below (assuming it's level).

Designing suspension geometry is an exercise in compromise. The question here is do you want your tyres parallel with the road under compression or not. Since under compression you're generally in a situation where you're testing the tyre's grip, it seems to me that a degree or 2 of negative camber is actually ideal.

Comment: Re:you can teach this stuff to them... (Score 1) 989

by mk2mark (#33041786) Attached to: Louisiana, Intelligent Design, and Science Classes
Just for the record there's a case for dinosaurs in the bible. Read the end of Job where he talks about the Behemoth and the Leviathan, or note the numerous mentions of "dragons"/taninim.

Your Sunday school teacher might have been full of crap, don't be fooled by the myopic views of others.
Biotech

First Halophile Potatoes Harvested 117

Posted by timothy
from the integrated-dill-is-the-next-step dept.
Razgorov Prikazka writes "A Dutch-based company from Groningen is trying to create a potato race that is able to survive in a saline environment. The first test-batch was just harvested (English translation of Dutch original) on the island Texel and seem to be in good shape. The company states that rising sea-levels will create a demand for halophile crops. I do wonder if one still has to put salt on ones potatoes when they are grown in salt water."

Comment: Re:Innovation! (Score 1) 525

by mk2mark (#30524926) Attached to: The Last GM Big-Block V-8 Rolls Off the Line
Who on earth modded this informative????

A V allows you package more displacement in to smaller overall volume or to have less car to package around given in engine. Weight savings from a V engine boosts handling performance and economy. Yet an inline engine will be cheaper than a V, due to one, block, single manifolds, two camshafts instead of four.

Since a v engine has twice as many heads how can it possibly weigh less or have more displacement for it's size?

V engines don't have the length of an inline engine, and are more cube shaped which tends to suit application to more engine bays.

Difference in power may come from firing order, and the path intake charge and exhaust gas take and a small reduction in friction in a Inline 4 or 6. Inline 6s can have a good cross flow set up for top end power when mounted longitudnally in a front engined car (short straight intake runners and 6 into 1 headers, make a good turbo platform. BMW, Nissan and Toyota have exploited this to great effect in racing and in road cars. Aftermarket Nissan Skyline motors with 6-1 turbo manifolds make whopping power.

I don't think I've ever seen a non-cross-flow v-engine. They're at least as suited to a cross-flow head as an inline engine.

Turbo engines are "suited" to 6-1 manifolds because there's very little advantage in tuning the exhaust of a turbo'd engine. The 6-1 manifold is chosen because of this and because it takes up less space. If pulse tuning was any use on a turbo engine, they'd all be 6-2-1 as in an n/a application you could tune the engine to produce torque as the turbo spools.

I'd also wager that Skylines make whopping power because of the "whopping" turbo.

In the end, V8s rose to greatnews because it was probably the best balance between a number of cylinders, dimensions, displacement etc. A four cylinder block is about as long as you want to go. Big displacement engines need a greater number of pistons to stop the piston speeds getting out of hand along with smoothness reasons. Eight cylinders is just right, for big power or a big engine.

Nonsense, you can counteract piston bore with the stroke of the engine to have whatever speed you wish. Eight cylinders were chosen probably more because this leads to a more suitable ratio between engine dimensions.

A inline 6, and a 90 degree V12 and a boxer six are probably the three ideal engines, having perfect balance. The greatest engine of them all on the balance of all considerations, including, cost, complexity and packaging is the inline four. That's why V8s are made out of two of them:

Wrong again. An inline 6 has primary and secondary harmonic balance - about as good as any engine could hope to have, but not perfect. A boxer 6 does not have this, usually a boxer is chosen for a low centre of gravity/space saving to slap a bunch of turbos on top. A v12 has the same balance as an inline 6 no matter what the angle is, 90 or otherwise. It's a little smoother because of the increase in fires per revolition.

American V8s most often really are just two inline four engines stuck together. Right down to the split-plane (cross-plane) crankshaft. Yes there are hack mechanics who have lopped off one bank of cylinders to make a inline four, it works. Unfortunatley cross-plane crankshafts have a lot of drawbacks including difficult to control vibration, unbalanced piston movement, poorer exhaust scavanging in certain exhaust configuartions and need for counterweights that add rotational inertia. Yes every American V8 you drove had a dirty kludge under the hood.

Inline 4's invariably have flat-plane cranks, so you've got that backwards too. Crossplane crank v8's have secondary balance, which actually means they're better balanced than flatplanes - Maybe you heard that flatplane's rev higher so thought this may be the reason they're better balanced? Not so, the reason for this is because of the lack of need for the large counterweights a crossplane has.

IMHO, a real V8 has a flat plane crankshaft. Truly the correct format for a V8, better firing order, more power, more balance and even better sound :)

Better is subjective, but the burble people love from v8 engines is only present in crossplane cranks. You can have this one though, because of v8 Ferrari's (although we all know the real Fezza engine is a v12).

Comment: Re:Of course, there is another solution (Score 1) 721

by mk2mark (#30113584) Attached to: Vatican Debates Possibility of Alien Life
Speaking as a christian, I absolutely agree with this point of view. I'm not going to disagree that my views are blatantly unscientific and radical, however I will disagree that I may be wrong. I don't say this to be confrontational, condescending or brash, the only reason I say it is to show the distinction (in my reasoning) between my scientific and religious views.

I wouldn't view myself as an unreasonable person, but events in my life and a very real relationship leave me in no doubt that what I believe is true - absolutely true. It's not scientific, but it's logical (to me at least).

APL hackers do it in the quad.

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