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Joined: Jan 2009
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Originally Posted by Hamwich
Originally Posted by howard

Interesting post. Where do you get the 30666 and 11089 from? Can you expand on the calculation please.


The formula for calculating the energy needed to overcome aerodynamic drag is

0.5 x Air Density x CdA x Speed**3

Air Density can be ignored for comparative purposes, CdA is the drag coefficient multiplied by the frontal area of the vehicle in m**2

All values in SI units, so 50 mph is 22.3m/s which cubes to 11089.567. 70mph is 31.3m/s hence 30666

The result of the formula is expressed in Joules/second, ie Watts. Divide by 746 to get HP of course.

Note that although aerodynamic drag increases with the square of the speed (which is what Peter quite correctly said, and I rather sloppily corrected by not using clear enough terminology), the power expenditure necessary to overcome drag increases with the cube of speed. For a detailed explanation of why this is, see:

https://physics.info/drag/


Thanks for that.

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I remember doing charity track runs at the Lyneham open day a couple of years back. During some laps I experimented with gears to see how the car reacted to aerodynamic deficiences ( a well know Morgan “they all do that, sir”).
A basic comparison using revs/ gear selection to get up to speed on a long straight. My rule of thumb results were that trying to keep in a max torque band into the headwind gave a slightly better speed when in 4th for slightly longer before upping to 5th. All a bit unscientific a nice exercise.
The aero/drag effect is why supercars need the very high power to achieve their very high top speed.
Just to add.....the upright, flat windscreen of a trad is a good airbreak! I think Caterham owners could claim about an extra 10 mph top end if they removed their similar screens.

Last edited by sospan; 15/07/21 05:52 PM.

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Originally Posted by Peter J
Traditionalists should sit down....

This is a EV Plus 4 conversion

https://youtu.be/m8HJjUEVpGQ

Made by Electrogenic REV...

they claim 150 miles range and 3X the torque of the original...

www.electrogenic.co.uk if you are tempted.


150 miles isn't good enough.

Would anyone buy an ICE car with a tank that only gave 150 miles??


DaveW
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You'd be lucky to get 150 miles out of an old school Mini & several other classics of the era...but we accepted it as normal back then, plus there were a lot more rural filling stations too


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Originally Posted by DaveW

150 miles isn't good enough.

Would anyone buy an ICE car with a tank that only gave 150 miles??


Depends on their usage pattern, I would think - and whether one has the capacity for overnight charging at home. Although I agree that 150 miles is too low for a car that one wishes to go on tours with, a car with 150 mile range would be easily enough to cope with all our non-Morgan driving over the last few years. IIRC the average daily use for a car in the UK is only around 30 miles or so. I suspect that a significant proportion of Morgans don't actually do very high daily mileages. Most of them (mine included) don't do significant annual mileages either, so maybe it's an attractive option for some.

There will always be travelling salespeople types who have to do galactic mileages, but as working and travel patterns change I would think that for very many people an EV would be perfectly adequate for their needs. Plus of course the latest generation of EVs are giving much higher mileages, I believe the Mustang EV claims nearly 400 miles of range.


Tim H.
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None of my current bikes will do 150 miles on a tank full and for many periods in my life, I only had a bike. However, I can fill up at any petrol station in minutes....


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I fill up the Plus 8 at 220 miles to prevent any range anxiety moments in minutes...

The Fiesta will do 500 miles easily at legal limits.

I wouldn't even consider a PP3 car until they hit the 400 mile and 30k mark and that would be out of legislative necessity not choice, I'll wait for the real thing Hydrogen to come along as it will.


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Originally Posted by +8Rich
The Fiesta will do 500 miles easily at legal limits.


The thing is though, how often have you needed to go 500 miles in your Fiesta in one day? I accept that many people, especially those who live in urban environments, don't have the possibility to charge their car overnight at home, but having said that, it's equally true that for millions and millions of car owners it's entirely feasible to simply plug the car in when you get home and for it to charge slowly overnight on a domestic socket. Who cares if it takes your car 10 hours to charge if it does it whilst you are down the pub or watching telly or sleeping?

So the idea of a car that can do 500 miles on a tankful is pretty much irrelevant if all you ever need is to be able to go 20 miles to work or maybe 100 miles at the weekend to visit a National Trust property or whatever.


Tim H.
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Originally Posted by Hamwich
Originally Posted by +8Rich
The Fiesta will do 500 miles easily at legal limits.


The thing is though, how often have you needed to go 500 miles in your Fiesta in one day? I accept that many people, especially those who live in urban environments, don't have the possibility to charge their car overnight at home, but having said that, it's equally true that for millions and millions of car owners it's entirely feasible to simply plug the car in when you get home and for it to charge slowly overnight on a domestic socket. Who cares if it takes your car 10 hours to charge if it does it whilst you are down the pub or watching telly or sleeping?

So the idea of a car that can do 500 miles on a tankful is pretty much irrelevant if all you ever need is to be able to go 20 miles to work or maybe 100 miles at the weekend to visit a National Trust property or whatever.









The relevance to me is the running costs, with £30 RFT it's cheaper than a Pizza supper to run, and the irony is that Ford have never pushed this virtue of high mpg and great range. I mentioned it so we had a good comparison of what a reasonably up to date tractor can achieve compared to Jon's Mini figure.

500 mile was very relevant to me whilst working as Stirling was a regular port of call in a day and that is about that distance. An overnight and then on on up to Aberdeen for the Shetland ferry was quite handy with those sort of ranges tbh.

Thankfully since choosing to retire early six years ago no such boring treks up the M6 are needed and it's strictly social and domestic runs these days to our three youngsters in differing areas of England and holidays.

The youngsters would have waited a long time for a visit if it had involved the M6 I can tell you I learnt to hate it with a vengeance.


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I frequently have to travel 500’mile round trips in a day as part of the business

I don’t believe battery or hydrogen are the future
Neither have the energy density that is required for our current lifestyles


Simon @ Sifab.co.uk

Sifabtemporary@gmail.com
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