Punx0r said:
"design is design", well thanks for clarifying that... I'm not sure what you're on about any more. I tell you a sample piece of lifting equipment is destructively tested with failure point at 50 tonnes and you reply telling me metal parts fail at the yield point.
You're still on about this? Design is design, ultimate is ultimate, and yield is yield. They are specific terms, although "allowable" is interchangeable with "design" or even hyphenated.
Punx0r said:
I'm telling you, the failure point of a part (metal or otherwise) is usually determined by the application/user. It can be yield or it can be UTS. It is when it fails to function as required anymore.
lol, no it is most certainly not. Absolutely not. It's done by testing.
Punx0r said:
And the distinction between statics and dynamics is what? Just because it's a different chapter in your book doesn't they are non-overlapping domains in the real world. You've jumped from EV drivetrains to frames, to furniture, to bridges. Feel free to tell us which of those applications doesn't see dyanmic loads.
You aren't using proper terms so it's hard to follow.
"design" or "allowable" is based on your load parameters, stress, strain, deflection etc. If your shaft was designed to deliver 30MPa and the factor of safety is 3, the shaft, when tested, should not fail below 90MPa. In the case of cars this is by law.
You don't seem to understand that the design incorporates all of the
known variables and assumes things like fatigue. Your factor of safety cover
uncertainties, bad metal, poor welds etc.
This is why you don't see many changes to the drive train when you moderately increase hp. It isn't required. And since the amount of hp increase you see in an ICE is potentially much greater, as well as the stresses in an EV being developed at start-up, modifying the power train, which hardly ever happens in ICE, is much, much less likely to be necessary in an EV.
Unless some company puts a giant electric motor in a cheap and poorly designed EV, there shouldn't be much need for power train mods in EV's. That's not to say people won't do it. People do all kinds of unnecessary thing to cars. I'm just saying there shouldn't be a need for it.
Punx0r said:
A factor of safety is not "a sum", it is, depending on how it's expressed, a number (5) or a ratio (5:1). It is the product of a sum, it is not a sum itself.
lol, so what do you think it is a magic number that they pull out of a hat?
The safety factor is an algebraic sum. It's based on calculating several ratings.
Punx0r said:
I'm hoping you mean 2+2 is a sum, because "x" is a multiplication operator and "+" is the sum. Completely different things.
Punx0r said:
Once again, you are assuming only linear relationships between power/torque and any possible effect on the components. You are wrong.
That's because it is linear. fyi-shaft designs are based on torque, not hp. You obviously don't know this.
I'm not sure what other drive train components you're going on about. Linkages? Control arms? You're just tossing vague things out there and hoping something sticks.
Punx0r said:
Please, please, get this into your head: If you have a mass-produced component designed to handle x-load and you place a y-safety factor on it, that does not mean you can allow the user to load the part to x * y. Failures will occur. End of.
No, x*y would be the minimum. Usually based on something like 99.5% of time.
That's the end of that story. Get a book.
Punx0r said:
Indeed, it is possible. It's apparently used in aerospace. It comes with rigourous design, exhaustive testing and a diligent inspection and maintenance regime in service. All things required to ensure reliable operation when safety factors are low.
I don't know, I'm in automotive engineering not aerospace. They use other terms and other methods of calculating similar design requirements.
Reliability is the number of parts that fail given the design using a normal distribution. Again, it varies from industry to industry.
Punx0r said:
Lol, this is just funny now. For one, electric motors have a much better short-term overload capability compared to ICEs. Most motors will take a 5-10x overload for ~10 seconds (long enough to complete a 1/4 mile run). What ICE can do that?
BECAUSE THEY ARE MORE EFFICIENT. They have less moving parts and they don't have as many contact surfaces and as a result don't generate as much heat.
I'm sure this is something you will see in racing. But we aren't talking about racing are we? So try to stick on topic
Punx0r said:
Secondly, no you can't typically take an ICE vehicle with 250HP and safely boost it to 1000HP. Put down the crackpipe.
lol, go to a drag strip once in your life.
Punx0r said:
OK, you've clearly been hitting the pipe waaaay too hard.
YOU said an OEM manufacturer can take an EV designed for nominal motor output
You see, right there you did it again. Nominal load is a structural term which is like design, because the nominal load times the resistance factor is similar to the design load times the factor of safety. But you also seem to use it like "average", which is confusing, not only me but you as well.
(Yes, we're all smoking crack cocaine, haha)
Punx0r said:
and software enable a ludicrous mode with no changes required to anything. Myself and others in this thread keep trying to tell you all the different ways you are wrong, buit you won't listen. Once again, applying a factor of safety to a component design does not give you an indefinite overload capacity.
I NEVER SAID IT DID. Stop with the strawmen, it's boring.
This is simple. An axle is going to be designed for 100000N.m of torque, with a factor of safety of 3, that means it will not fail 99.5% of the time if it is loaded to 30 000N.m. That's the law.
That's tripling the load. A ludicrious mode is what, 30% increase in torque (and that's generous).
Now I know you're not good at math, but 0.3<<3 It's 1/10th. It's not good for the car, it's not advisable, it will reduce the lifespan of the part, but it is VERY POSSIBLE TO DO. That's your "fudge factor" at work.
Assuming you needed a FoS of 3 for federal regulations, you would then use something like 3.3, which again is usually covered in rounding.
You keep going on about the "real world" like cars aren't designed to be used in the real world. That's so not the case I find it hard to believe what you've been saying. It might seem hard to understand but the "ludicrous mode" is just a name, it's not ludicrious from a design standpoint. It's perfectly logical. Assuming you have the battery to support the mode.
Punx0r said:
Once again with the pipe... You might as well go and argue the sky isn't blue. Over-spec'ed, over-built equipment lasts longer. Have you ever built an Ebike, or just a regular bicycle?
The factor of safety is "over-spec", "over-built". You don't seem to know there's no difference. Pick up book.
Punx0r said:
Tell me this: why does lifting equipment for objects required a 5:1 safety factor but equipment for lifting people requires 10:1?
Obviously because the man-lift is designed to last longer.
Oh wait, that's what you're trying to say.
I would say in the event of failure the consequences are greater, so when calculating the factor of safety more emphasis is placed on this.
Punx0r said:
Right, so the design life on ye olde cars was a lot less, so any doesn't have to last that long before it's considered to have a large design margin... It's been a long time since you could overheat an ICE without causing serious damage and I don't recall Henry Ford using plastic suspension components. An example of that won't last 100 years even kept in an air-conditioned museum with zero miles on the clock.
I'm not sure what you mean by design margin.