The Electric Car
in [Design]
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From: MooseFET on 3 Aug 2007 03:58 On Aug 2, 8:12 pm, Eeyore <rabbitsfriendsandrelati...(a)hotmail.com> wrote: > MooseFET wrote: > > Eeyore wrote: > > > MooseFET wrote: > > > > On the highway, the engine gets connected directly to the wheels. > > > > This takes the sosses of the electric machines out of the picture. > > > > What losses ? Electric motors are highly efficient. > > > Yes exactly. The losses in the electric motors. > > They should be very low. Traction motors can be 90% efficient. Ok, take that number for the generator too. 90% * 90% = 81% so the losses from the electrical machines woule be: 100% - 81% = 19% A mechanical transmission is about 98% efficient. 100% - 98% = 2% The the advantage to the Toyota system comes out to be about: 19% - 2% = 17% Better fuel economy. > > > > > It also allows the engine and both motors to be used for passing power. > > > > At the cost and complexity of requiring a transmission. I just don't see any sense in it. > > > It gives about 15% better fuel economy on the highway and about double > > the merging power. > > Better than ..... what ? > > Double compared to .... what ? Scotch mist ? Using your number above we get 17% and double compared to the same size and weight of series only system.
From: MooseFET on 3 Aug 2007 04:03 On Aug 1, 7:58 pm, Eeyore <rabbitsfriendsandrelati...(a)hotmail.com> wrote: > MooseFET wrote: > > Eeyore wrote: > > > > The current hybrids also use skinny tyres to reduce rolling resistance. I hate to think > > > of the adverse effect on road holding. > > > There is basically no difference in the traction. Wide tires look > > cool but below a certain amount of force per unit area of rubber give > > no traction advantage. The traction loss in thing tires is because > > the force on the surface is high enough to rip bits of the rubber or > > the road loose. They modern materials in the tires are less subject > > to this problem. The cars we are talking about are quite light too. > > I'm not talking about traction, I'm talking about road holding / handling. I know American roads don't have corners (or at > least from the way US cars drive you'd think that was the case) but we do here. "Road holding" is the ability to "stay on the road" or "at the place on the road the driver wishes". If the tires are providing the needed traction and are stiff enough they have done their part of the job. Anything else is a suspension issue. The thin tires work just fine. They may not look cool but they don't cause any problems.
From: MooseFET on 3 Aug 2007 04:05 On Aug 2, 5:47 pm, JosephKK <joseph_barr...(a)sbcglobal.net> wrote: > Eeyore rabbitsfriendsandrelati...(a)hotmail.com posted to > sci.electronics.design: > > > > > > > MooseFET wrote: > > >> Eeyore wrote: > > >> > The current hybrids also use skinny tyres to reduce rolling > >> > resistance. I hate to think of the adverse effect on road > >> > holding. > > >> There is basically no difference in the traction. Wide tires > >> look cool but below a certain amount of force per unit area of > >> rubber give > >> no traction advantage. The traction loss in thing tires is > >> because the force on the surface is high enough to rip bits of > >> the rubber or > >> the road loose. They modern materials in the tires are less > >> subject > >> to this problem. The cars we are talking about are quite light > >> too. > > > I'm not talking about traction, I'm talking about road holding / > > handling. > > And just how, exactly, do you separate the two (dealing with tires > only)? Both are ultimately limited by friction limits. Too much flex can also be a problem with tires. The cool looking wide ones are usually worse in this area than the ones the makers put on.
From: MooseFET on 3 Aug 2007 04:07 On Aug 2, 7:51 pm, Eeyore <rabbitsfriendsandrelati...(a)hotmail.com> wrote: > JosephKK wrote: > > Eeyore rabbitsfriendsandrelati...(a)hotmail.com posted > > > MooseFET wrote: > > >> Eeyore wrote: > > > >> > The current hybrids also use skinny tyres to reduce rolling > > >> > resistance. I hate to think of the adverse effect on road > > >> > holding. > > > >> There is basically no difference in the traction. Wide tires > > >> look cool but below a certain amount of force per unit area of > > >> rubber give > > >> no traction advantage. The traction loss in thing tires is > > >> because the force on the surface is high enough to rip bits of > > >> the rubber or > > >> the road loose. They modern materials in the tires are less > > >> subject > > >> to this problem. The cars we are talking about are quite light > > >> too. > > > > I'm not talking about traction, I'm talking about road holding / > > > handling. > > > And just how, exactly, do you separate the two (dealing with tires > > only)? Both are ultimately limited by friction limits. > > Skinny tyres don't corner very well. Total nonsense! Exactly how do you think the skinny tires make the car not corner.
From: Eeyore on 3 Aug 2007 04:10
MooseFET wrote: > Eeyore wrote: > > MooseFET wrote: > > > Eeyore wrote: > > > > > > The current hybrids also use skinny tyres to reduce rolling resistance. I hate to think > > > > of the adverse effect on road holding. > > > > > There is basically no difference in the traction. Wide tires look > > > cool but below a certain amount of force per unit area of rubber give > > > no traction advantage. The traction loss in thing tires is because > > > the force on the surface is high enough to rip bits of the rubber or > > > the road loose. They modern materials in the tires are less subject > > > to this problem. The cars we are talking about are quite light too. > > > > I'm not talking about traction, I'm talking about road holding / handling. I know American roads don't have corners > (or at > least from the way US cars drive you'd think that was the case) but we do here. > > "Road holding" is the ability to "stay on the road" or "at the place > on the road the driver wishes". If the tires are providing the needed > traction and are stiff enough they have done their part of the job. > Anything else is a suspension issue. > > The thin tires work just fine. They may not look cool but they don't > cause any problems. So why don't all cars run on thin tyres then ? Graham |