171–180 of 316 posts
Former automotive engineer chiming in. "Tweels" have been around a long time, but have always failed in terms of "NVH" (noise, vibration, harshness). Michelin is claiming that this generation of tweels are appropriate for passenger cars, which means that they think they've solved the NVH problem. They seem to be marketing these alongside EVs, I wonder if they're only really intended for lighter, compact-style cars. (…
Don't get me wrong - I'd expect Michelin to have done some testing to see NVH is within tolerance levels right? Airless is really close to working for bikes. If I were commuting on a bike now I'd be comfortable going for it. The downsides - painfully hard installation, uphill resistance, ...etc. - will be worth it.
Works for me. Feels comfortable and fast. Is economic.
YMMV.
Former automotive engineer chiming in. "Tweels" have been around a long time, but have always failed in terms of "NVH" (noise, vibration, harshness). Michelin is claiming that this generation of tweels are appropriate for passenger cars, which means that they think they've solved the NVH problem. They seem to be marketing these alongside EVs, I wonder if they're only really intended for lighter, compact-style cars. (…
Don't get me wrong - I'd expect Michelin to have done some testing to see NVH is within tolerance levels right? Airless is really close to working for bikes. If I were commuting on a bike now I'd be comfortable going for it. The downsides - painfully hard installation, uphill resistance, ...etc. - will be worth it.
One easy way to picture this is: recall your last long road trip, or airplane flight, anything more than 3 hours or so. You get so tired after those, especially considering that you've only just sat still for a few hours. But in actuality your body is making hundreds of tiny corrections to posture each minute, in response to the vibrations of the vehicle, and that literally exhausts your muscles and nervous system. Now imagine that you make that car "5% more harsh" and redo the road trip; you will feel the compound effects of that additional harshness. Auto manufacturers take NVH very seriously, because it turns out to be a pretty big deal.
My point is that even if NVH comes back OK in the lab, they still will need a good deal of real world data with test subjects representative of the 'average driver' before they can make a determination.
Edit to add: I know of at least one case where the entire drivetrain of a vehicle was redesigned due to NVH.
Would these work on Mars rovers too?
Or how about bicycles?
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A lot of heavy equipment drives around with water-filled tires, so it's already there. Definitely not what you meant though.
Hmm, why water filled? I can't think of any advantages, but can think of downsides such as a massive increase in unsprung weight.
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Hmm, why water filled? I can't think of any advantages, but can think of downsides such as a massive increase in unsprung weight.
Water's basically incompressible, if some Michael Crichton book I read like 25 years ago is to be believed. My guess would be one or more of: the above; greater heat capacity; or, something to do with surface area vs. volume meaning that at a large enough size water in a tire is far lower-pressure and easier to contain than air at a high enough pressure to keep it inflated, and/or, relatedly, something to do with hea…
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Some EVs have mandatory sound emitters to not be fully silent (and thus dangerous). I thought it was weird harmonics from the synRM engine but it's synthetic and enforced by regulations.
I thought it was a plastic valence rubbing on something.
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I picked a gas car of comparable size. The Civic and Golf are much smaller than the Model 3.
The Civic is 2 inches shorter and 2 inches narrower than the Model 3, but it actually has a larger interior volume by one cubic foot. Size up to the Accord which is 8 inches longer and a half inch wider than a Model 3 (and 9ft^3 more interior space), and it still only weighs 3131-3362 lbs.
Really though, the Civic and Accord aren't competing with the Model 3. They're front wheel drive. They have less power and torque. They use struts for the front suspension. All of these measures save significant weight (and cost). That's why I picked the BMW 3 series. It's similar size, performance, and cost. If we look at other competitors to the Model 3 we get similar weights:
- Volvo S60: 3,724-4,468lbs. (The low number is front wheel drive. The high number is a plug-in hybrid.)
- Audi A4: 3,682-3,726lbs.
- Mercedes C-Class: 3,472-3,605lbs.
- Cadillac CT4: 3,422-3,616lbs.
- Volkswagen Passat: 3,014–3,794lbs. (The lighter versions are front wheel drive only. The heavier versions are hybrids.)
In general, fancier cars are heavier. Also safer cars tend to be heavier. Yes batteries are heavy, but so are engines, drivetrains, starter motors, turbochargers, exhaust systems, fuel tanks, and so on. Early electric cars were significantly heavier because they were based on combustion platforms. When EVs are designed from the ground up, the weight penalty is less than 10%. Vehicle models in the same market segment vary more than that, and some combustion vehicles are already heavier than their electric competitors. This will likely get better with time as battery technology improves.
The statement "EVs are heavier" is approximately as true as "AWD vehicles are heavier". All else equal it's more likely than not, but the difference is rarely enough to matter for any practical purpose.
1. https://www.caranddriver.com/honda/accord/specs/2021/honda_a...