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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#81
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O.T. electric cars - do they have gearboxes?
On 24/04/17 03:31, Johnny B Good wrote:
However, in order to maximise efficiency and power to weight performance of electric traction motors, you get the best performance using a high rpm motor[1] which basically precludes direct drive hub motor designs unless you're prepared to sacrifice top end performance for improved battery economy at more modest urban traffic speeds (you replace mechanical transmission losses with much lower electric cabling losses). [1] High rpm on account it uses less turns of heavier gauge copper in its windings, meaning reduced I squared R losses. But needs more current to achieve the same magnetic moment. No, what counts is magnetic reversals per second, times the iron mass. You can achieve that with a lot of poles, or a lot of RPM. Copper losses turn out to be pretty much independent of the configuration, and are a more a function of as you say RPM BUT its not 'RPM' that matters, its 'poles per second'. -- "Anyone who believes that the laws of physics are mere social conventions is invited to try transgressing those conventions from the windows of my apartment. (I live on the twenty-first floor.) " Alan Sokal |
#82
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O.T. electric cars - do they have gearboxes?
On Sunday, 23 April 2017 16:54:08 UTC+1, Nightjar wrote:
On 23-Apr-17 10:10 AM, Tim Streater wrote: In article , Nightjar wrote: .... Whatever you want to think, an R&D subsidiary of IAV Gmbh developed a small, lightweight steam engine, using modern technology throughout, that could be fitted into motor vehicles, although they see the initial application as being in auxiliary power units, particularly in third world countries. They claim fuel efficiency as being similar to a diesel engine. It uses catalytic heating to avoid flames, which keeps emissions down to very low levels, and can burn a very wide range of fuels. Steam is viable, even if that does not sit well with your world view. As I hinted at before, where is the condenser and how big does it have to be? You would have to ask the developers that. However, they have said that the engine could be fitted into a car, so they obviously don't think it is a serious problem. -- -- Colin Bignell The only successful steam condensers for increasing pressure differencewere fitted to locomotives in Siberia for Winter running. Others have been fitted to try to reduce water needed to be carried. But have little effect on efficiency. It's just not possible to reject that amount of heat on mobile steam engines |
#83
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O.T. electric cars - do they have gearboxes?
On Monday, 24 April 2017 07:39:14 UTC+1, harry wrote:
On Sunday, 23 April 2017 16:54:08 UTC+1, Nightjar wrote: On 23-Apr-17 10:10 AM, Tim Streater wrote: In article , Nightjar wrote: .... Whatever you want to think, an R&D subsidiary of IAV Gmbh developed a small, lightweight steam engine, using modern technology throughout, that could be fitted into motor vehicles, although they see the initial application as being in auxiliary power units, particularly in third world countries. They claim fuel efficiency as being similar to a diesel engine. It uses catalytic heating to avoid flames, which keeps emissions down to very low levels, and can burn a very wide range of fuels. Steam is viable, even if that does not sit well with your world view. As I hinted at before, where is the condenser and how big does it have to be? You would have to ask the developers that. However, they have said that the engine could be fitted into a car, so they obviously don't think it is a serious problem. -- -- Colin Bignell The only successful steam condensers for increasing pressure differencewere fitted to locomotives in Siberia for Winter running. Others have been fitted to try to reduce water needed to be carried. But have little effect on efficiency. It's just not possible to reject that amount of heat on mobile steam engines |
#84
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O.T. electric cars - do they have gearboxes?
On Sunday, 23 April 2017 21:37:09 UTC+1, Vir Campestris wrote:
On 23/04/2017 08:13, harry wrote: Higher steam temperatures results in less efficient boilers because the exiting combustion gases can be at no lower temperature than the stem. This turns out not to be the case. You can, for example, use the warm exhaust to preheat the incoming air & fuel. Andy The effect is negligible and leads ot all sorts of control problems. The specific heat of air is low. |
#85
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O.T. electric cars - do they have gearboxes?
On 23-Apr-17 9:57 AM, The Natural Philosopher wrote:
On 23/04/17 09:49, Nightjar wrote: Steam is viable, even if that does not sit well with your world view. Technically perhaps ...but economically? IC engines are good because you don't have to lug the fuel oxidant or the working fluid around. Its in huge supply as atmospheric oxygen and gases respectively. Once you are building a static installation though, steam predominates and is more efficient, because you can run huge condensers on the back end. And you have a variety of thermal sources that you can hook up - coal, oil gas, nuclear. The developers of the engine I mentioned see the main transport use to be in commercial vehicles in third world countries, where its multi-fuel capacity would allow more flexibility than a conventional ICE. -- -- Colin Bignell |
#86
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O.T. electric cars - do they have gearboxes?
On 24/04/17 09:55, Nightjar wrote:
On 23-Apr-17 9:57 AM, The Natural Philosopher wrote: On 23/04/17 09:49, Nightjar wrote: Steam is viable, even if that does not sit well with your world view. Technically perhaps ...but economically? IC engines are good because you don't have to lug the fuel oxidant or the working fluid around. Its in huge supply as atmospheric oxygen and gases respectively. Once you are building a static installation though, steam predominates and is more efficient, because you can run huge condensers on the back end. And you have a variety of thermal sources that you can hook up - coal, oil gas, nuclear. The developers of the engine I mentioned see the main transport use to be in commercial vehicles in third world countries, where its multi-fuel capacity would allow more flexibility than a conventional ICE. Ah. Like a traction engine. To go with the windmills. -- "I guess a rattlesnake ain't risponsible fer bein' a rattlesnake, but ah puts mah heel on um jess the same if'n I catches him around mah chillun". |
#87
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O.T. electric cars - do they have gearboxes?
On Thursday, April 20, 2017 at 8:11:00 AM UTC+1, Tim Watts wrote:
On 19/04/17 23:03, NY wrote: "DerbyBorn" wrote in message 2.236... Murmansk wrote in : I've just been for a ride in someone's Nissan Leaf - it was impressive, so quiet and amazing acceleration. Do electric cars have a gearbox (an automatic one I presume)? Or does the motor just run faster the faster you go? I was told by the owner the optimum speed for economy of battery usage is about 55mph. It doesn't sound like it's changing gear. No gearbox or clutch. Mainly because an electric motor, when correctly driven, can generate torque from zero speed and don't have such severe upper limits to the speed because there are no reciprocating parts which have to rapidly reverse direction. Not having a gearbox (automatic or manual) must make it much easier to drive because torque/acceleration is directly dependent on accelerator position and not a combination of that and gear ratio - you don't get gentle acceleration which suddenly becomes kick-in-the-back acceleration as the automatic transmission reacts to your gradually increasing accelerator position by suddenly deciding to change down in a situation where a manual driver would hold onto the present gear. I find this the hardest thing about automatics: I accelerate out of a roundabout and the car suddenly lurches forward so I ease off the throttle slightly and it changes back up - very difficult to hit the happy medium. It is also easier to build in torque limiting to any value, to prevent the car lurching forwards if you press the accelerator too hard when setting off from rest, or for a cruise control to also accelerate you briskly and yet smoothly from one speed (eg rest) to the another speed speed. The fact that (AFAIK) no cars implement this doesn't mean it's not possible to do. Not only - but motors can be geared virtually - by changing the number of poles. Say you have a 24 pole motor. By deciding how to drive the windings in phase or antiphase, you can pair off adjacent poles for an effective 12 pole, 8 pole, 6 pole etc setup. More poles = slower and higher torque, less poles = higher rpm. I have no idea if this method is used by any car motors but I think some trains do - you can hear the "whirrr... drop pitch whirrr" which I can only explain as pole changing as the motor is otherwise directly connected to the axel. I have also noticed that sound and imagined it to be due to exactly what you have described. A neat way of 'changing gear' electrically instead of mechanically. Robert Robert |
#88
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O.T. electric cars - do they have gearboxes?
On 24 Apr 2017 09:44:44 GMT, Huge wrote:
I have also noticed that sound and imagined it to be due to exactly what you have described. A neat way of 'changing gear' electrically instead of mechanically. Having listened to Tube trains "changing up" as they accelerate out of the station, and assuming that they can't possibly have mechanical gearboxes, The Germans and Austrians have tuned some of theirs. https://www.youtube.com/watch?v=U-nhr5H7mSU G.Harman |
#89
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O.T. electric cars - do they have gearboxes?
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#90
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O.T. electric cars - do they have gearboxes?
Nightjar wrote:
On 23-Apr-17 9:57 AM, The Natural Philosopher wrote: On 23/04/17 09:49, Nightjar wrote: Steam is viable, even if that does not sit well with your world view. Technically perhaps ...but economically? IC engines are good because you don't have to lug the fuel oxidant or the working fluid around. Its in huge supply as atmospheric oxygen and gases respectively. Once you are building a static installation though, steam predominates and is more efficient, because you can run huge condensers on the back end. And you have a variety of thermal sources that you can hook up - coal, oil gas, nuclear. The developers of the engine I mentioned see the main transport use to be in commercial vehicles in third world countries, where its multi-fuel capacity would allow more flexibility than a conventional ICE. Sounds like we're going back to charcoal burners towed behind the car! |
#91
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O.T. electric cars - do they have gearboxes?
On 24/04/2017 10:44, Huge wrote:
On 2017-04-24, RobertL wrote: On Thursday, April 20, 2017 at 8:11:00 AM UTC+1, Tim Watts wrote: [49 lines snipped] I have no idea if this method is used by any car motors but I think some trains do - you can hear the "whirrr... drop pitch whirrr" which I can only explain as pole changing as the motor is otherwise directly connected to the axel. I have also noticed that sound and imagined it to be due to exactly what you have described. A neat way of 'changing gear' electrically instead of mechanically. Having listened to Tube trains "changing up" as they accelerate out of the station, and assuming that they can't possibly have mechanical gearboxes, I found this quite interesting! I think they used to run pairs of motors in parallel on starting and switch over to series at higher speeds. That was some time ago and I don't know if they still do. -- Mike Clarke |
#92
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O.T. electric cars - do they have gearboxes?
Mike Clarke wrote:
On 24/04/2017 10:44, Huge wrote: On 2017-04-24, RobertL wrote: On Thursday, April 20, 2017 at 8:11:00 AM UTC+1, Tim Watts wrote: [49 lines snipped] I have no idea if this method is used by any car motors but I think some trains do - you can hear the "whirrr... drop pitch whirrr" which I can only explain as pole changing as the motor is otherwise directly connected to the axel. I have also noticed that sound and imagined it to be due to exactly what you have described. A neat way of 'changing gear' electrically instead of mechanically. Having listened to Tube trains "changing up" as they accelerate out of the station, and assuming that they can't possibly have mechanical gearboxes, I found this quite interesting! I think they used to run pairs of motors in parallel on starting and switch over to series at higher speeds. That was some time ago and I don't know if they still do. That description fits with this for older trains. https://www.whatdotheyknow.com/cy/re...%20Edition.pdf I think this is what they use now. https://en.m.wikipedia.org/wiki/Vari...requency_drive Tim -- Please don't feed the trolls |
#93
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O.T. electric cars - do they have gearboxes?
Tim+ wrote:
Mike Clarke wrote: I think they used to run pairs of motors in parallel on starting and switch over to series at higher speeds. That was some time ago and I don't know if they still do. That description fits with this for older trains. https://www.whatdotheyknow.com/cy/re...%20Edition.pdf Indeed so - the old DC machines with series resistors and series/ parallel switching. Simple, but inefficient. Somewhere in the loft I have a copy of my calculations for the Class 313 notching curves. Now slowly passing into history. Chris -- Chris J Dixon Nottingham UK Plant amazing Acers. |
#94
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O.T. electric cars - do they have gearboxes?
On 24-Apr-17 12:34 PM, Capitol wrote:
Nightjar wrote: On 23-Apr-17 9:57 AM, The Natural Philosopher wrote: On 23/04/17 09:49, Nightjar wrote: Steam is viable, even if that does not sit well with your world view. Technically perhaps ...but economically? IC engines are good because you don't have to lug the fuel oxidant or the working fluid around. Its in huge supply as atmospheric oxygen and gases respectively. Once you are building a static installation though, steam predominates and is more efficient, because you can run huge condensers on the back end. And you have a variety of thermal sources that you can hook up - coal, oil gas, nuclear. The developers of the engine I mentioned see the main transport use to be in commercial vehicles in third world countries, where its multi-fuel capacity would allow more flexibility than a conventional ICE. Sounds like we're going back to charcoal burners towed behind the car! I think that charcoal is one of the things their catalytic burner couldn't handle. However, almost any flammable liquid or gas would work. -- -- Colin Bignell |
#95
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O.T. electric cars - do they have gearboxes?
On 23/04/2017 22:26, Tim Streater wrote:
In article , Tim Streater wrote: Perhaps these researchers are of the same ilk as the Cold Fusion ones, or that autism/vaccination [1] twerp. [1] I see the anti-vax twerps are still on the go, with outbreaks of measles as a result. Its because vaccines carry a small risk and the twerps can't workout that the risk from the illness is many times more. So they put their child in danger and endanger others that can't have the vaccine for reasons other than stupidity. |
#96
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O.T. electric cars - do they have gearboxes?
On 24/04/2017 08:19, Chris Hogg wrote:
(SI = Somewhat Inconvenient, but there it is!) Don't worry we are going back to degrees F, foot-pounds, etc. after brexit. |
#97
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O.T. electric cars - do they have gearboxes?
On 23/04/2017 22:09, Tim Streater wrote:
Actually Tin-Tout/Tin. Which equals 1 - Tout/Tin. OK, I'm not a physicist. And the reason its degrees K is because the kinetic energy in a gas is proportional to its temperature in K. Just look up thermal efficiency in Winky. But I'm enough of one to know that while one kelvin is equivalent to one degree celsius, it isn't a degree. It's just a kelvin. Andy |
#98
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O.T. electric cars - do they have gearboxes?
On 24/04/2017 07:43, harry wrote:
On Sunday, 23 April 2017 21:37:09 UTC+1, Vir Campestris wrote: On 23/04/2017 08:13, harry wrote: Higher steam temperatures results in less efficient boilers because the exiting combustion gases can be at no lower temperature than the stem. This turns out not to be the case. You can, for example, use the warm exhaust to preheat the incoming air & fuel. Andy The effect is negligible and leads ot all sorts of control problems. The specific heat of air is low. Well, I suggest you go and look at your nearest power station. There's a nice model of one in the Science Museum. Andy |
#99
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O.T. electric cars - do they have gearboxes?
On 24/04/2017 07:43, harry wrote:
On Sunday, 23 April 2017 21:37:09 UTC+1, Vir Campestris wrote: On 23/04/2017 08:13, harry wrote: Higher steam temperatures results in less efficient boilers because the exiting combustion gases can be at no lower temperature than the stem. This turns out not to be the case. You can, for example, use the warm exhaust to preheat the incoming air & fuel. Andy The effect is negligible and leads ot all sorts of control problems. The specific heat of air is low. What? Are you really trying to suggest the temperature of combustion is independent of incoming air temperature? There are even recuperative furnaces for smelting. I suggest you look up 'recovery boiler design' before showing any more ignorance. |
#100
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O.T. electric cars - do they have gearboxes?
On Mon, 24 Apr 2017 12:44:26 +0100, Mike Clarke wrote:
On 24/04/2017 10:44, Huge wrote: On 2017-04-24, RobertL wrote: On Thursday, April 20, 2017 at 8:11:00 AM UTC+1, Tim Watts wrote: [49 lines snipped] I have no idea if this method is used by any car motors but I think some trains do - you can hear the "whirrr... drop pitch whirrr" which I can only explain as pole changing as the motor is otherwise directly connected to the axle. I have also noticed that sound and imagined it to be due to exactly what you have described. A neat way of 'changing gear' electrically instead of mechanically. Having listened to Tube trains "changing up" as they accelerate out of the station, and assuming that they can't possibly have mechanical gearboxes, I found this quite interesting! I think they used to run pairs of motors in parallel on starting and switch over to series at higher speeds. That was some time ago and I don't know if they still do. If true, the sequence would have been series for starting, then paralleled for 'cruise speed'. Effectively a two speed "Electric Gearbox" created out of nothing more sophisticated than a cleverly sequenced bunch of contactor switches. The same trick can be used in hydraulic drive trains where the motors *are* fed in parallel from the pump to double the starting torque at half speed (they get the full pump pressure at half pump flow rate each) before being 'valved' into series for full/cruise speed (each operating at full pump flow but only half the pump pressure). For passenger cars, I doubt such an 'electric gearbox' technique would be applied (other than as a fixed ratio matching between motor and road wheel speeds in the fashion of a rear wheel differential reduction box as part of the optimisation of the design of the whole power train). Since an electric motor is, like a steam traction engine, capable of providing high torque from a complete standstill, the necessary voltage controller to control the vehicle's speed can also effectively function as a combined accelerator and automatic gearbox in one when fabricated using modern heavy duty switching converter technology thus neatly saving on the need for an additional box of contactors to switch between series and parallel motor arrangements (or effective poles in a single motor). A box of contactors in addition to the electronic speed controller would most likely be more at home with rolling stock and heavy duty goods wagons and specialised military vehicles (and possibly off-road 4WD vehicles) otherwise why embellish an already effective switching converter solution to speed control with the additional expense of another box of contactors? I'm no expert on how the manufacturers *actually* apply these basic laws of physics as they relate to electric (and hydraulic and gross mechanical) power trains[1], just someone who has a comprehensive understanding of the principles the manufacturers are constrained to work with. :-) [1] When all is said and done, the basic function of a power train is just a specialised application of Archimede's Principle of levers. -- Johnny B Good |
#101
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O.T. electric cars - do they have gearboxes?
On 23/04/2017 22:26, Tim Streater wrote:
In article , Tim Streater wrote: Perhaps these researchers are of the same ilk as the Cold Fusion ones, or that autism/vaccination [1] twerp. [1] I see the anti-vax twerps are still on the go, with outbreaks of measles as a result. Some of us were not willing to risk MMR, but paid for single vaccines to gain the protection - rather expensive at 3 vaccines per child, £136 per vaccine and 3 children, but we had our reasons. At the time of the "scare" my wife (a nurse) worked directly with two different colleagues, both of whose children were developing normally, both children had the MMR, both suffered a fever and went floppy the evening of vaccination day. In both cases, the children took a week to recover and had regressed significantly. Both were later diagnosed as autistic. Having such immediate experience of what some people were saying persuaded us not to take the risk. Getting the single vaccinations was not easy, as not only were they expensive, but the government had apparently put a limit on how much could be imported, creating a national shortage. SteveW |
#102
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O.T. electric cars - do they have gearboxes?
On Mon, 24 Apr 2017 08:19:28 +0100, Chris Hogg wrote:
On Mon, 24 Apr 2017 01:45:45 GMT, Johnny B Good wrote: On Sun, 23 Apr 2017 21:42:59 +0100, Vir Campestris wrote: On 22/04/2017 22:43, Johnny B Good wrote: On Sat, 22 Apr 2017 12:13:31 +0100, charles wrote: In article , Tim Streater wrote: One of the laws of thermodynamics IIRC - efficiency is related to the difference between input and output temps - in degrees K, not C. my elementary physics suggests that if you are only refering to a temperature difference the answer is the same in °K and in °C.° The main benefit of using deg K instead of Deg C is the complete and utter absence of negative numbers by which to confuse the mathematics. :-) It's true enough that as far as steam engines are concerned, this is unlikely to effect calculations involving deg C, but there are other heat engines designs based on fluids with much lower freezing and boiling points than zero deg C (the triple point of water to within an accuracy of one decimal place). FFS Kelvins aren't degrees. Well, assuming by "Kelvins" you meant Degrees Kelvin and by "degrees" you meant degrees Celcius, they are! Degrees Kelvin is not the approved SI unit. The kelvin is, as is K. So water freezes at 273.15 kelvin or 273.15 K. Not degrees Kelvin, nor Kelvins nor even kelvins (which I wrongly used in an earlier post). http://tinyurl.com/kr3l36f (SI = Somewhat Inconvenient, but there it is!) Ah! I now see the point being made by Andy. :-) I like your definition, "SI = Somewhat Inconvenient"[1]. I've watched enough episodes of "QI" to know better by now. However, in my defence, I'm not habitually writing scientific papers where such precision of terminology is a vital part of not being deemed a bit of a Dickhead by one's peers so lack the experience required to remain up to date with the latest fads in SI unit terminology. I'm now aware of the fact that Kelvins (or, more precisely, Kelvin) *aren't* degrees. :-) [1] It occurred to me that the misunderstanding was more to do with semantics so I think a better definition of SI may be[2] "Semantically Inconvenient". [2] Please note the *correct* usage of "may be" in this case. I'm sick of the sight of "may be" when the *single* word "maybe" was intended (along with the less common but equally irritating use of "maybe" in place of the phrase "may be"). Apologies for this mini-rant but it *does* feel good to get that off my chest. :-) -- Johnny B Good |
#103
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O.T. electric cars - do they have gearboxes?
On 22/04/2017 10:48, The Natural Philosopher wrote:
On 22/04/17 09:45, Nightjar wrote: On 21-Apr-17 6:46 PM, harry wrote: On Friday, 21 April 2017 09:58:50 UTC+1, Nightjar wrote: On 21-Apr-17 8:47 AM, harry wrote: On Thursday, 20 April 2017 19:24:26 UTC+1, Nightjar wrote: On 20-Apr-17 6:18 PM, Tim Streater wrote: In article , Nightjar wrote: On 20-Apr-17 8:18 AM, harry wrote: On Wednesday, 19 April 2017 19:47:29 UTC+1, Murmansk wrote: I've just been for a ride in someone's Nissan Leaf - it was impressive, so quiet and amazing acceleration. Do electric cars have a gearbox (an automatic one I presume)? Or does the motor just run faster the faster you go? I was told by the owner the optimum speed for economy of battery usage is about 55mph. It doesn't sound like it's changing gear. Internal combustion engines are inherently unsuitable for traction, hence the need for gearboxes/clutches etc. Electric motors can be designed to be ideal for traction. Max torque at zero rpm. I could get that with a steam engine. And a small one at that for a car. But AIUI, it's the condenser that's the problem. With a 24 gallon water tank, the 1924 Doble E had a 1500 mile range and it could move off from cold in under 30 seconds. Drivel. Water is not fuel. I was answering the point about the condenser. However, recent advances in catalytic splitting of water could make it feasible to use water as fuel, if you really wanted to. Drivel. Have you never heard of the Law of Conservation of Energy? The principle has been demonstrated. A few years ago the Japanese demonstrated a fuel cell car that ran entirely on water. All steam engines and boilers are inherently inefficient. They will never come anywhere near the ICE efficiency wise. Typical modern steam power station 37%. More with supercritical steam Typical diesel. 25%. Petrol cars achieve a tank to wheel thermal efficiency of about 16%. Non-condensing third generation steam locomotives achieve a drawbar thermal efficiency of about 16%. No use telling harry anything. The thermodynamics are all well understood, but not by harry I spent forty years running them. And getting rid of them where possible. I suspect that the boilers and engines you are familiar with are more nineteenth century technology than twenty-first century. A titanium tube flash boiler can supply steam at up to 4,000 psi and 650C. Ceramics allow engines to work at those temperatures and pressures and achieve efficiencies not even dreamed of with conventional materials. Exatamondo. I cant remember what the law is called, but the hotter the working fluid (steam in this case) is to start with, and the colder the final exhaust, the more efficient is the engine. Which is why a combined cycle gas turbine that starts with 1000C gases in the jet engine, then heats a boler to get steam, and has a final after condenser temp of around 50C, willnet you over 60% thermal efficiency. There was an article some time ago saying that you can do better than that. Follow up the whole train with a closed circuit system containing LPG. The waste heat boils the LPG which drives an expander to produce more power. Extracting the energy cools the gas to a mixed vapour/liquid which can then be cooled a little further in a condenser to re-liquify it for re-circulation. Steve W |
#104
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O.T. electric cars - do they have gearboxes?
On 24/04/2017 21:33, Vir Campestris wrote:
On 23/04/2017 22:09, Tim Streater wrote: Actually Tin-Tout/Tin. Which equals 1 - Tout/Tin. OK, I'm not a physicist. And the reason its degrees K is because the kinetic energy in a gas is proportional to its temperature in K. Just look up thermal efficiency in Winky. But I'm enough of one to know that while one kelvin is equivalent to one degree celsius, it isn't a degree. It's just a kelvin. Andy Correct. You can have a difference of 10 degrees Centigrade, 10 degrees Celcius or 10 Kelvin and they are the same ... you cannot have 10 degrees Kelvin, it is just wrong! °C is a relative scale, a gradient, hence the degrees, whereas K is an absolute scale, a fundamental unit, hence no degrees. Now, how about Rankine? SteveW |
#105
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O.T. electric cars - do they have gearboxes?
On 24/04/2017 23:02, Steve Walker wrote:
Correct. You can have a difference of 10 degrees Centigrade, 10 degrees Celcius or 10 Kelvin and they are the same ... you cannot have 10 degrees Kelvin, it is just wrong! °C is a relative scale, a gradient, How can it have a gradient when its scalar? The bit of the equation is just constant + the temp where the constant for kelvin is zero. |
#106
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O.T. electric cars - do they have gearboxes?
On 24/04/17 22:52, Steve Walker wrote:
On 22/04/2017 10:48, The Natural Philosopher wrote: On 22/04/17 09:45, Nightjar wrote: On 21-Apr-17 6:46 PM, harry wrote: On Friday, 21 April 2017 09:58:50 UTC+1, Nightjar wrote: On 21-Apr-17 8:47 AM, harry wrote: On Thursday, 20 April 2017 19:24:26 UTC+1, Nightjar wrote: On 20-Apr-17 6:18 PM, Tim Streater wrote: In article , Nightjar wrote: On 20-Apr-17 8:18 AM, harry wrote: On Wednesday, 19 April 2017 19:47:29 UTC+1, Murmansk wrote: I've just been for a ride in someone's Nissan Leaf - it was impressive, so quiet and amazing acceleration. Do electric cars have a gearbox (an automatic one I presume)? Or does the motor just run faster the faster you go? I was told by the owner the optimum speed for economy of battery usage is about 55mph. It doesn't sound like it's changing gear. Internal combustion engines are inherently unsuitable for traction, hence the need for gearboxes/clutches etc. Electric motors can be designed to be ideal for traction. Max torque at zero rpm. I could get that with a steam engine. And a small one at that for a car. But AIUI, it's the condenser that's the problem. With a 24 gallon water tank, the 1924 Doble E had a 1500 mile range and it could move off from cold in under 30 seconds. Drivel. Water is not fuel. I was answering the point about the condenser. However, recent advances in catalytic splitting of water could make it feasible to use water as fuel, if you really wanted to. Drivel. Have you never heard of the Law of Conservation of Energy? The principle has been demonstrated. A few years ago the Japanese demonstrated a fuel cell car that ran entirely on water. All steam engines and boilers are inherently inefficient. They will never come anywhere near the ICE efficiency wise. Typical modern steam power station 37%. More with supercritical steam Typical diesel. 25%. Petrol cars achieve a tank to wheel thermal efficiency of about 16%. Non-condensing third generation steam locomotives achieve a drawbar thermal efficiency of about 16%. No use telling harry anything. The thermodynamics are all well understood, but not by harry I spent forty years running them. And getting rid of them where possible. I suspect that the boilers and engines you are familiar with are more nineteenth century technology than twenty-first century. A titanium tube flash boiler can supply steam at up to 4,000 psi and 650C. Ceramics allow engines to work at those temperatures and pressures and achieve efficiencies not even dreamed of with conventional materials. Exatamondo. I cant remember what the law is called, but the hotter the working fluid (steam in this case) is to start with, and the colder the final exhaust, the more efficient is the engine. Which is why a combined cycle gas turbine that starts with 1000C gases in the jet engine, then heats a boler to get steam, and has a final after condenser temp of around 50C, willnet you over 60% thermal efficiency. There was an article some time ago saying that you can do better than that. Follow up the whole train with a closed circuit system containing LPG. The waste heat boils the LPG which drives an expander to produce more power. Extracting the energy cools the gas to a mixed vapour/liquid which can then be cooled a little further in a condenser to re-liquify it for re-circulation. The law of diminishing returns steps in. You cant get lower than ambient, and even if you could get back to ambient its still only around 70% from memory. You need to have a hotter gas to start with. Steve W -- "Women actually are capable of being far more than the feminists will let them." |
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O.T. electric cars - do they have gearboxes?
Johnny B Good wrote:
On Mon, 24 Apr 2017 12:44:26 +0100, Mike Clarke wrote: I think they used to run pairs of motors in parallel on starting and switch over to series at higher speeds. That was some time ago and I don't know if they still do. If true, the sequence would have been series for starting, then paralleled for 'cruise speed'. Effectively a two speed "Electric Gearbox" created out of nothing more sophisticated than a cleverly sequenced bunch of contactor switches. It is quite true, though the actual method is somewhat more complicated. I was about to start writing a description, but it is covered rather well he http://www.railway-technical.com/tract-01.shtml About the last UK stock to be built using this principle was the 1983 Tube Stock which was retired from service comparatively early in 1998. Older examples are still in daily use. Chris -- Chris J Dixon Nottingham UK Plant amazing Acers. |
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O.T. electric cars - do they have gearboxes?
On 20/04/2017 10:51, The Natural Philosopher wrote:
On 20/04/17 10:17, Tim Watts wrote: On 20/04/17 08:13, The Natural Philosopher wrote: On 20/04/17 08:10, Tim Watts wrote: More poles = slower and higher torque, less poles = higher rpm. What utter ********. Perhaps you should check your facts before you go slagging people off: https://en.wikipedia.org/wiki/Dahlan...changing_motor I'll accept an apology when you've read that. I have no idea if this method is used by any car motors but I think some trains do - you can hear the "whirrr... drop pitch whirrr" which I can only explain as pole changing as the motor is otherwise directly connected to the axel. However, I'm pretty sure most traction has at least one set of fixed gears as motor rpms tend to be higher than desired wheel rpms. Well even there you would be wrong. Its depends on how many poles the motor is built with (as opposed to driven). I could explain the theory, but you wouldn't understand it would you? Perhaps you could try - or is it beneath you? People would simply say 'too long, didn't bother to read it' and go back to believing simple fairy tales as per usual. Lets just deal with one aspect. Number of poles. There is a given amount of iron you can cram into a motor, that, plus the magnets you use (unless they are electromagnets) determines the amount of energy *per magnetic reversal* you can get in and out of the system This leads to a simple rule: the more revs (reversals) the more power. Until other factors limit you, as high frequencies start to impose their own extra losses, as does friction. Adding more poles allow for more reversals per shaft rotation. It is equivalent to a gearbox. However only using *some* of those poles nets you nothing, because you are simply using less ironwork. Its pointless. No one does it. It is simply like having a smaller motor that weighs more. Electric motors are UTTERLY different from other motors.They dont really have a 'power rating' re se. Only when fed from a given voltage. I've run motors designed for 3V, generally used at 6-7v, at 11-12 v and got more than three times the power out of them. The limitation was brush bounce and wear in that case, and the availability of gearboxes to get the insane RPM down to something usable.. In practical terms a multipole motor is bigger and more expensive than a two or three pole motor* BUT if the gearbox you need to use is more expensive and heavier...then the multi-pole wins slightly. Some of the model motors used to come with kevlar wound rotors, to stop them exploding. More revs, more power. That's part of the simple story. The more complex story involves understanding copper losses (resistance) iron losses (hysteresis and frictional motor losses) plus issues with the controlling electronics (peak currents, inductance, switching losses and so on). And it it uses permanent magnets, the field strength, weight, and performance versus temperature of those as well. Each one of which is a book chapters worth. *two magnetic, three wound poles is the most basic uni-directional motor. I'd take that as the apology Tim :-) -- Cheers, Rob |
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O.T. electric cars - do they have gearboxes?
On 25/04/2017 08:23, RJH wrote:
On 21/04/2017 11:21, wrote: On 21/04/2017 08:04, RJH wrote: On 21/04/2017 00:04, wrote: On 20/04/2017 17:23, Tim Streater wrote: In article , Brian Reay wrote: On 19/04/2017 19:47, Murmansk wrote: I've just been for a ride in someone's Nissan Leaf - it was impressive, so quiet and amazing acceleration. Do electric cars have a gearbox (an automatic one I presume)? Or does the motor just run faster the faster you go? I was told by the owner the optimum speed for economy of battery usage is about 55mph. It doesn't sound like it's changing gear. We looked at the Tesla and were told it didn't have a gear box. We decided against all electric, we don't like the idea of being stuck with a 'flat' battery on a journey. The idea of stopping for 'top ups' on a long journey is fine until you consider the practical aspects. As a matter of interest, is anyone looking (as in considering making) a hybrid electric? As in, rather than having a powerful petrol engine, a less powerful electric motor, a normal size fuel tank and a smaller battery (like my Toyota Auris), instead have a full-size electric motor, larger battery, but with a small petrol engine and small fuel tank? That way one could stop anywhere to recharge or even do it on the go. A few months ago I went through the EV search, I think the ones with small ICEs are called Range Extenders. I decided on a plug-in hybrid and am very pleased with it - 208HP ICE and 80HP electric motor driving a seven speed auto box with some magic arrangement of clutches that allows one or both to drive, or neither, or to use the motor for regen braking. All very clever but probably a maintenance nightmare when it gets old. BMW 3 series? A friend has one and likes it. No, it's a M-B C350E estate. About the same price as the BMW - surprised, thought it'd be a fair bit more. They're quite expensive but a lot of spreadsheet what-ifs showed that buying it in a company was cheaper over 3 years than buying an equivalent 2-3 year old petrol or diesel (hisss ;-) ) car and running that privately for 3 years, this was allowing for all factors (including depreciation). I've been very pleased with it so far. |
#111
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O.T. electric cars - do they have gearboxes?
On Tue, 25 Apr 2017 07:49:22 +0100, Chris J Dixon wrote:
Johnny B Good wrote: On Mon, 24 Apr 2017 12:44:26 +0100, Mike Clarke wrote: I think they used to run pairs of motors in parallel on starting and switch over to series at higher speeds. That was some time ago and I don't know if they still do. If true, the sequence would have been series for starting, then paralleled for 'cruise speed'. Effectively a two speed "Electric Gearbox" created out of nothing more sophisticated than a cleverly sequenced bunch of contactor switches. It is quite true, though the actual method is somewhat more complicated. I was about to start writing a description, but it is covered rather well he http://www.railway-technical.com/tract-01.shtml Although the article mentions pretty well all aspects of DC motor control as historically employed for railway locomotion, the use of a journalistic style over a technical authoring one resulted in a confusion of descriptive terms (eg currents instead of magnetic fields and the impression that the [armature] windings on the rotor were wound *around* the rotor shaft). Although the author 'loses points' for the use of confusing terms, he does gain points for his comprehensive coverage of the difficulties, imposed by the limitations of the technology of the day, facing the designers in their attempts to recover the braking energy for use by other trains on the line. -- Johnny B Good |
#112
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O.T. electric cars - do they have gearboxes?
Johnny B Good wrote:
Although the article mentions pretty well all aspects of DC motor control as historically employed for railway locomotion, the use of a journalistic style over a technical authoring one resulted in a confusion of descriptive terms (eg currents instead of magnetic fields and the impression that the [armature] windings on the rotor were wound *around* the rotor shaft). Although the author 'loses points' for the use of confusing terms, he does gain points for his comprehensive coverage of the difficulties, imposed by the limitations of the technology of the day, facing the designers in their attempts to recover the braking energy for use by other trains on the line. OK, if you want a bit more reading, try these Principles of Direct Current Electric Traction https://archive.org/details/in.ernet.dli.2015.288435 Electric Traction https://archive.org/details/in.ernet.dli.2015.19338 Chris -- Chris J Dixon Nottingham UK Plant amazing Acers. |
#113
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O.T. electric cars - do they have gearboxes?
On Tue, 25 Apr 2017 19:16:52 +0100, Chris J Dixon wrote:
Johnny B Good wrote: Although the article mentions pretty well all aspects of DC motor control as historically employed for railway locomotion, the use of a journalistic style over a technical authoring one resulted in a confusion of descriptive terms (eg currents instead of magnetic fields and the impression that the [armature] windings on the rotor were wound *around* the rotor shaft). Although the author 'loses points' for the use of confusing terms, he does gain points for his comprehensive coverage of the difficulties, imposed by the limitations of the technology of the day, facing the designers in their attempts to recover the braking energy for use by other trains on the line. OK, if you want a bit more reading, try these Principles of Direct Current Electric Traction https://archive.org/details/in.ernet.dli.2015.288435 Electric Traction https://archive.org/details/in.ernet.dli.2015.19338 Thank you for those links, Chris. I had a quick look at the linked pdfs and they look an interesting read so I've downloaded them for future reference. :-) -- Johnny B Good |
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O.T. electric cars - do they have gearboxes?
Johnny B Good wrote:
On Tue, 25 Apr 2017 19:16:52 +0100, Chris J Dixon wrote: OK, if you want a bit more reading, try these Principles of Direct Current Electric Traction https://archive.org/details/in.ernet.dli.2015.288435 Electric Traction https://archive.org/details/in.ernet.dli.2015.19338 Thank you for those links, Chris. I had a quick look at the linked pdfs and they look an interesting read so I've downloaded them for future reference. :-) Yes,. When I started in the industry a colleague lent me Dover, which had much of what I needed to know at the time. I did get a photocopy of the entire volume, but somebody never returned it to me :-( Chris -- Chris J Dixon Nottingham UK Plant amazing Acers. |
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O.T. electric cars - do they have gearboxes?
On Wednesday, April 19, 2017 at 2:47:29 PM UTC-4, Murmansk wrote:
I've just been for a ride in someone's Nissan Leaf - it was impressive, so quiet and amazing acceleration. Do electric cars have a gearbox (an automatic one I presume)? Or does the motor just run faster the faster you go? I was told by the owner the optimum speed for economy of battery usage is about 55mph. It doesn't sound like it's changing gear. What do you folks think about the company Adomani, which goes public tomorrow, with the symbol ADOM? I think their technology sounds pretty cool and Ive been reading everything I can find about the company recently, leading up to the IPO and Im pretty impressed already. Id really like to get into this one on the ground floor because I have a strong feeling, based on the research Ive done, that this one is going to take off shortly out of the gate. So Id be really interested in hearing what others have to say about it. |
#116
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O.T. electric cars - do they have gearboxes?
On Wednesday, April 19, 2017 at 2:47:29 PM UTC-4, Murmansk wrote:
I've just been for a ride in someone's Nissan Leaf - it was impressive, so quiet and amazing acceleration. Do electric cars have a gearbox (an automatic one I presume)? Or does the motor just run faster the faster you go? I was told by the owner the optimum speed for economy of battery usage is about 55mph. It doesn't sound like it's changing gear. What do you folks think about the company Adomani, which goes public tomorrow, with the symbol ADOM? I think their technology sounds pretty cool and Ive been reading everything I can find about the company recently, leading up to the IPO and Im pretty impressed already. Id really like to get into this one on the ground floor because I have a strong feeling, based on the research Ive done, that this one is going to take off shortly out of the gate. So Id be really interested in hearing what others have to say about it. |
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O.T. electric cars - do they have gearboxes?
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O.T. electric cars - do they have gearboxes?
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#119
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O.T. electric cars - do they have gearboxes?
wrote in message ... On Wednesday, April 19, 2017 at 2:47:29 PM UTC-4, Murmansk wrote: I've just been for a ride in someone's Nissan Leaf - it was impressive, so quiet and amazing acceleration. Do electric cars have a gearbox (an automatic one I presume)? Or does the motor just run faster the faster you go? I was told by the owner the optimum speed for economy of battery usage is about 55mph. It doesn't sound like it's changing gear. What do you folks think about the company Adomani, which goes public tomorrow, with the symbol ADOM? I think their technology sounds pretty cool and I've been reading everything I can find about the company recently, leading up to the IPO and I'm pretty impressed already. I'd really like to get into this one on the ground floor because I have a strong feeling, based on the research I've done, that this one is going to take off shortly out of the gate. So I'd be really interested in hearing what others have to say about it. ------------------------------------------------------------------------------ As you are new to this UK group, you should write in a UK style and don't give away your foreign UTC time-zone. If your company can't produce a better script, I doubt it can produce a better car. -- Dave W |
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O.T. electric cars - do they have gearboxes?
wrote:
On Wednesday, April 19, 2017 at 2:47:29 PM UTC-4, Murmansk wrote: I've just been for a ride in someone's Nissan Leaf - it was impressive, so quiet and amazing acceleration. Do electric cars have a gearbox (an automatic one I presume)? Or does the motor just run faster the faster you go? I was told by the owner the optimum speed for economy of battery usage is about 55mph. It doesn't sound like it's changing gear. What do you folks think about the company Adomani, which goes public tomorrow, with the symbol ADOM? I think their technology sounds pretty cool and Ive been reading everything I can find about the company recently, leading up to the IPO and Im pretty impressed already. Id really like to get into this one on the ground floor because I have a strong feeling, based on the research Ive done, that this one is going to take off shortly out of the gate. So Id be really interested in hearing what others have to say about it. I've heard that it's complete and utter ****. Don't waste your money. Seriously, do you think we're too gormless to spot such flagrant spamming? Tim -- Please don't feed the trolls |
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