What machinery are you working with? I gather weigh isn't an issue with it? The use of gear boxes with an ev allows you to use a smaller motor and keep the weight down. Direct drive is a possibility but you can end up with a heavier motor, slower acceleration time or reduced top end speed. The big plus with electric motors is the freedom they give designers, being smaller and reasonably self contained. We've argued about batteries before, they need to be at least half the weight that they are now to really take on the ICE, hopefully some of this new tech coming through will do this. Yes, I know Tesla is doing fine with standard cells etc etc but half a tonne of battery is tough to design around- although Tesla have managed it. How thick is the aluminium plate under the car? 5mm?
,
Jul 11, 9:16am
Except batteries don't need to be half the weight to take on ICES. There are already cars with over 500km of range using existing batteries. Battery cost is the issue at the moment, not weight. Other than high performance vehicles like Tesla's, which are from a new start up manufacturer which has had some clear quality control issues, I've never heard of a gear box failure in a production EV. I'm sure they happen but they're incredibly rare due to the tiny number of parts involved. When you have far fewer parts, these parts can be much beefier and still weigh the same amount as the complex gearbox on an ICEs.
apollo11,
Jul 11, 9:53am
OK, let's play a thought experiment. Let's say that Elon Musk has brought his design for the first Model S to you for approval, what design issues would you point out?
At the time he built it, I don't think there were really many people in the world qualified to say. Certainly not anyone here on this forum. However it exists, and drives pretty damn nicely, so other than quality control which isn't really a design issue, I'd say he got it pretty right.
apollo11,
Jul 11, 10:00am
So you can't look at the design and see any issues? I hope you don't design stuff for a living. Edit to add: I also think the S was a great piece of design, but there were a number of shortcomings they have tried to mitigate.
,
Jul 11, 10:12am
So obviously any design will have compromises, every machine ever made will require decisions to be made based on current technology, cost of manufacture, reliability and a whole host of other factors that effect how is put together. I'm not sure why you would think these issues were not a part of every design and manufacturing process for everything that's every been made. They're certainly not a show stopper for EVs. Yes I do lots of design in my business.
apollo11,
Jul 11, 10:16am
Exactly, so you should be able to see where the issues are.
,
Jul 11, 10:26am
No I'm not at all clear what you're getting at, these are the same issues which any design faces, they're not show stoppers at all, and your statements about the technology requirements before EVs are possible ICE replacements are factually incorrect.
apollo11,
Jul 11, 10:34am
What's the biggest design constraint of any product being designed for market? Edit: other than the laws of physics, which are a given.
,
Jul 11, 11:56am
I'm not sure you could say there's a biggest, there's a whole bunch that are required to line up before you can go to market, cost, reliability, safety.
apollo11,
Jul 11, 12:11pm
There is only one. Cost to manufacture- all else is secondary. Meaning that if money is unlimited, there is nothing that can't be made, although the product might cost a trillion dollars to buy. As we have seen with the Model 3, so far there hasn't been one car produced for $35000, and there won't be until battery prices fall. The easiest way of reducing the cost of batteries is to need less of them for the same range, ie they need to have better energy density, and we are seeing some of that coming through. Reducing the weight of the battery pack will also increase range, reduce component loading, potentially allow the use of less exotic metals and possibly allow for better battery placement. Currently where the battery pack sits now it is vulnerable to object penetration (hence the aluminium shield) and is susceptible to deformation in an accident. I could go on for ages but you get the idea.
I wonder if the designer ever looked at the Ford Pinto with the same mindset as you? Obviously not.
apollo11,
Jul 11, 1:19pm
Huh? The designers at the time were perfectly aware of the issues with the pinto. However the management decided that it would be more 'cost effective' to settle lawsuits with the families of the estimated number of dead, than the cost of re-design and re-tooling.
,
Jul 11, 2:21pm
Err yeah, but all of these issues have been solved. Tesla now has there batteries at around$100 per KwH and the rest of the industry will follow quickly. The battery pack is no more vulnerable to penetration than a fuel tank, it's just that not every fuel fire makes the news. Generally if you've penetrated your battery pack then you're probably dead anyway as you have hit something very very hard. It's a myth that there are more exotic materials in an EV than an ICE, sure you've got Cobalt and Lithium, but Cobalt is down to and 2% of the battery and that's probably the hardest one to get. Of course you only need them once rather than every time you fill the car up. Like all new technologies the first ones are expensive, but the price is falling fast. Also the massive operating cost savings mean that it doesn't take a genius to work out the purchase price doesn't have to be less or the same as an ICE.
The easiest way to make batteries cheaper has nothing to do with composition, it's about the economies of scale that can be gained with manufacturing.
apollo11,
Jul 11, 2:43pm
All of the Teslas except for the Model 3 have been aluminium bodied except for the model 3 - to keep weight down. More expensive, but OK on a luxury car. The model 3 has a mix of various tensile steels and some alloy too- it's going to probably require quite specialised repair. There is a large alloy plate under every Tesla because the batteries were deemed to be vulnerable to intrusion from stuff flicked up from the road, unlikely to happen- but Ford Pinto. The battery packs are going to be the Achilles heel until they can find a better cell. There is too much material tied up in the battery pack, 500kg for the bigger ones- and you can't amortise material costs. With their current battery technology I doubt very much that Tesla can compete with ICE on the criteria of range, features and price with their ev's. Yes with luxury cars they are close, but across the entire market they can't.
serf407,
Jul 11, 11:01pm
Tesla aim for china factory with half million a year vehicle production. https://nyti.ms/2KNltN0
harm_less,
Jul 12, 9:05am
This is the first of an excellent series of 4 panel discussions from the recent Fully Charged Live event in the UK. A wealth of information on historical, present and upcoming matters related to EVs and consumer self-generation: https://youtu.be/hCa3BD0Haew
billyfieldman,
Jul 14, 2:46pm
Safety wise, how do EVs such as Nissan Leaf compare with other cars? The Monash UCSR doesn't seem to list any EVs.
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