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Author Topic: How toxic is your car exhaust?  (Read 7854 times)
dhaslam
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« Reply #15 on: October 19, 2017, 04:57:59 PM »

It must have taken a lot of effort to design a test  that understates emissions  by eighteen times.   Perhaps they  could turn their attention to designing new breathalysers.
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djh
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« Reply #16 on: October 19, 2017, 10:50:47 PM »

We might understand the effects on living tissue of tyre particulates and their chemical composition, but is there much study of how to reduce them? For example, the cruder forms of self-steering rear axles create a shuffle motion of the (rear) tyres as the suspension articulates, wearing tyres faster. A simple change of design could reduce this wear, which amplified over millions of vehicles would be highly effective.

Great. I'm sure that finding ways to reduce especially HGV miles would also be useful. I have no problem with additional work, as I said.

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Citroen's hydropneumatic suspension is no more (unless you consider a few tractors) and genuinely active suspension is the preserve of the very few, most expensive cars. BOSE's linear electromagnetic motor system is bulky and as yet largely unproven, Tenneco's development of Chris Heyring's Kinetic Suspension - http://www.nauti-craft.com/chris_heyring.html - is well-proven, compact and inspired by Citroen's own system.

The fact that a suspension system has been replaced by yet another new system, doesn't mean the first one wasn't invented! It simply means there has been yet more change.

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Almost all cars made use passive steel suspension wedged between the wheelarms and body. It's crude, heavy, relies on distorting metal and attempts to serve more than one purpose in one massive compromise. Just as on horse-drawn coaches, there are tweaks and enhancements which have developed (Brougham coaches used multiple springs back in the 1800s, with different spring and damping rates for the ultimate body control, today VW group use polyurethane bushing for bump stops and magnetically-controlled reactive damping) but it's the same fundamental idea of relying on distorting metal and damping the motion to suit the road speed range.

By the same type of argument, horse carriages are exactly the same as horseless carriages. They're all made of solid materials, cut into shapes and fastened together. There are many other possibilities but engineering is by its nature a typeforming process, especially when constrained by cost.

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Springing supports a car's/horse-drawn coach's mass while maintaining travel in the springs and attempts to isolate the sprung mass from the unsprung as the wheels follow road bumps and undulations. There's a huge compromise in spring strength as payload is typically up to 40% of a modern vehicle's mass which creates all sorts of ride and handling problems, the lighter/more flexibly sprung the vehicle, the greater the problem. It therefore suits suspension engineers for a vehicle to be heavier and more stiffly sprung. The third function of springing on a motor car is to provide roll resistance, creating yet more compromise along with the corrupting influence of anti-sway/roll bars.

Good analysis, which illustrates what was and is clever about Citroen's approach. The roll resistance is more of a constraint on the engineering, since there's excellent roll resistance if there's no suspension.

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Leaf springs, torsion bars and coil springs all utilise the resistance to distortion and the elasticity of the material used, whether under a Tesla or a C17th coach. The compromises are more of a problem for motor cars since the speed are higher and cornering ability is dependent on springing, I imagine one of those Broughams could have been extremely comfortable given the large wheels, decent wheel base, padded seats and combination of multiple springs. Particulates would have been horse dander and resuspension of road dust by galloping hooves, away from concentrations of wood and coal smoke.

As I recall the problem with horses is mainly horseshit rather than dander, not to mention horse corpses. And it was precisely the development of electric trams and ICE cars that resolved it for a hundred years or so thanks to their continual development.

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If electric cars are to grow lighter and less powerful in order to improve air quality (as exhaust pollution drops lower and lower it's likely tyre particulates become a big issue) then suspension is one aspect of the which should be brought into the modern age, reducing tyre wear without losing grip or speed. With a simple EM rather than complex, expensive ICEs it's possible truly good suspension could become the focus for customers - it's perfectly easy to quantify passenger comfort and tyre loadings.

I don't know what proportion of emissions from tyres are caused by inadequacies in suspension compared to the proportion caused by friction during acceleration, braking and cornering or even rolling resistance but I'd be surprised if it was anywhere close. Which suggests to me that tyre design and other aspects of the vehicle might be more profitable places to start looking to reduce emissions.
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phoooby
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« Reply #17 on: October 20, 2017, 12:10:38 AM »

Hasn't this whole tyre pollution thing been slightly debunked by the fact that the primary article was written by an undergraduate from Edinburgh uni sponsored by an oil company?. I would imagine most of the stuff redistributed into the air is created by ICE cars so as their number reduce there will be less to distribute. Engine/exhaust emissions seem to be a lower lying fruit, especially as the tech is around now to solve the problem. Make cars smaller and lighter in 10-20 years time when they are transfusing to EV and pollution has been vastly reduced already. EV's will reduce in weight over time anyway as battery tech evolves so they may be heavier now but in 10-20 years time they could well be lighter so throwing the whole argument of heavy cars and non exhaust emissions out the window.
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RIT
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« Reply #18 on: October 20, 2017, 12:48:36 AM »

Hasn't this whole tyre pollution thing been slightly debunked by the fact that the primary article was written by an undergraduate from Edinburgh uni sponsored by an oil company?. I would imagine most of the stuff redistributed into the air is created by ICE cars so as their number reduce there will be less to distribute. Engine/exhaust emissions seem to be a lower lying fruit, especially as the tech is around now to solve the problem. Make cars smaller and lighter in 10-20 years time when they are transfusing to EV and pollution has been vastly reduced already. EV's will reduce in weight over time anyway as battery tech evolves so they may be heavier now but in 10-20 years time they could well be lighter so throwing the whole argument of heavy cars and non exhaust emissions out the window.

This is a report on the whole thing

    https://www.treehugger.com/cars/do-electric-cars-generate-much-particulate-pollution-gas-and-diesel-powered-cars.html

The comments include the following info/statement

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What is not known to most about the "study", is that is was conducted by a German inventor/small business owner of specialty hydraulic (fluid) hybrid technology patents and consulting company, and a 2nd year Edinburgh college student he hired as a summer intern to assist with the study and use the college's name to lend more legitimacy to the study - so no, it was not conducted by "scientists from the University of Edinburgh" as has been erroneously reported by various media outlets. (you can do your own online research into Peter Achten* and his company "INNAS - Fluid Power Innovation")

What is key to understanding why the study got the results they did, is that the vehicles selected for the weight comparison were cherry-picked (meaning certain minority ones selected even though some like the Honda Fit EV had even already been discontinued from the market, and other majority ones omitted, such as the globally best-selling mid-sized Nissan LEAF...which at ~3,200 pounds actually weighs insignificantly different than say a comparable sized Nissan Altima) This was likely in order to help ensure the the results of the study end up matching with the pre-determined outcome that the author wanted/had already decided it need to be (such as "Electric vehicles are 24% heavier"). Note that conversion-compliance built EVs (like the Fit EV) will always weigh more than purpose-designed ones (like the LEAF, BMW i3, Tesla, etc)

So why conduct such study? Because the author wants his hydraulic hybrid system to gain more notoriety and perhaps even incentives, and since it carries no "heavy" battery nor heavy motors, only fluids/tanks/pumps/pistons, he can tout that it has a lower weight than a standard hybrid or EV. Attacking the competition with "independent research" to back up one's claims of a superior product...in this case research he conveniently conducted himself. Smiley

Now understand, the first two paragraphs I wrote are completely verifiable as objective truth, though it is harder to do so with the 2nd paragraph about the cherry picking as the actual study is behind a pay-wall (clever, huh? Get the media to do the propaganda heavy lifting, pun intended, and hide the actual research methods and data)

The third paragraph is conjecture, we can't know without proof what motivated this hydraulic engineer to make his first foray into EV emissions research, but the circumstantial evidence is strong. Make up your own mind, but know, that this so-called research is as un-scientific, biased and flawed (remember: no actual cars were even tested!) as the day is long. It would not survive the peer-review process that actual emissions research is typically subjected to.

*Achten in his 2008's paper "A serial hydraulic hybrid drive train for off-road vehicles" wrote about the Toyota Prius electric-hybrid that its "electric drive train components result in an increased vehicle weight, which increases the fuel consumption of the vehicles" while claiming his hydraulic accumulators "have a high power density, much higher than electric batteries" per unit weight.
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« Reply #19 on: October 20, 2017, 02:24:25 PM »


I don't know what proportion of emissions from tyres are caused by inadequacies in suspension compared to the proportion caused by friction during acceleration, braking and cornering or even rolling resistance but I'd be surprised if it was anywhere close. Which suggests to me that tyre design and other aspects of the vehicle might be more profitable places to start looking to reduce emissions.

From anecdotal evidence, I think there could be a bigger effect than you suppose - driving on identical tyres, on similar roads, in a similar manner and in two broadly similar mass and output cars has resulted in about a quarter more miles from one than the other (the heavier, more powerful car wore its tyres more slowly). Both were working correctly, both modern designs (V70 D5 and Octavia TDi). Motorway miles are about a quarter to one third of the total. It's something I've noticed down the years, my Mercedes (E-class) and ancient (CX) Citroens were always remarkably gentle on tyres, VW group the opposite (especially those with torsion beams).

It's something which no doubt is a long way from being studied, tyre construction materials are much more likely to come under scrutiny. If real-world emissions were studied in a model by model basis, it could be a big problem for the likes of Tesla, for example.


Hasn't this whole tyre pollution thing been slightly debunked by the fact that the primary article was written by an undergraduate from Edinburgh uni sponsored by an oil company?. I would imagine most of the stuff redistributed into the air is created by ICE cars so as their number reduce there will be less to distribute. Engine/exhaust emissions seem to be a lower lying fruit, especially as the tech is around now to solve the problem. Make cars smaller and lighter in 10-20 years time when they are transfusing to EV and pollution has been vastly reduced already. EV's will reduce in weight over time anyway as battery tech evolves so they may be heavier now but in 10-20 years time they could well be lighter so throwing the whole argument of heavy cars and non exhaust emissions out the window.

There are scores of studies of non-exhaust emissions, the subject has been discussed in Parliamentary committees. The 'primary article' you mentionnwas a headline grabber but of little relevance because of the provenance and motivation.

https://www.theguardian.com/environment/2017/aug/04/fewer-cars-not-electric-cars-beat-air-pollution-says-top-uk-adviser-prof-frank-kelly was discussed in another thread and http://publications.jrc.ec.europa.eu/repository/bitstream/JRC89231/jrc89231-online%20final%20version%202.pdf is an interesting read.

There seems to be an attitude that since EVs are set to remove exhaust pollution from the road, non-exhaust pollution is something we can ignore, perhaps because brake dust is likely to reduce with EVs and there's a view tyre emissions can't be reduced or made less toxic, even though n/e emissions have been growing above the rate of vehicle miles (over a quarter since 1990).

Given more and more miles are covered every year, that EVs will use tyres more heavily unless lightweight design comes into fashion and these emissions are completely unrestricted but of known toxicity, why let air pollution stand still or increase after an initial dip, as the EV revolution rolls out?
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