Hardware update gained 15% range

All Jaguar I-Pace related discussions
Delta5
Posts: 41
Joined: Tue Sep 24, 2019 1:32 pm
Location: Midlands

Re: Hardware update gained 15% range

Post by Delta5 » Thu Oct 10, 2019 8:55 am

Having seem a wheel on a balancing machine, it seems to take very little power to accelerate it to running speed , how little power?.
At 50mph a typical wheel will rotate at 520 rpm and might weigh 20 kg
A flywheel disc of that size would store 2400 joules, (.0007 KWh)
accelerating to 50 mph in 10 seconds takes .25 KW
4 20 kg wheels would absorb 1KW for 10 seconds, a 15kg wheel would take .75KW
The energy needed to maintain a flywheel is zero, only bearing and aerodynamic drag slows it down

The difference in energy needed between different weight of 4 wheels in this example is .25 KW for 10 seconds
Energy to accelerate the wheels is very small, rolling resistance and aerodynamic drag at 50 mph would be vastly greater


Chewy
Posts: 1904
Joined: Tue Nov 06, 2018 5:46 pm
Location: Forest of Dean. UK.

Re: Hardware update gained 15% range

Post by Chewy » Thu Oct 10, 2019 9:45 am

Energy to accelerate the rotating mass is significant.

I am sure someone else on here can do the sums before I get around to it.


User avatar
mjc
Posts: 429
Joined: Fri May 19, 2017 2:43 pm
Location: Hertfordshire, UK

Re: Hardware update gained 15% range

Post by mjc » Thu Oct 10, 2019 1:09 pm

:oops: I fear that Laithwaitian Anti-Gravity might be about to make an entrance :oops:
I-Pace HSE delivered 14/12/2018 - Farallon Black, Air++, oyster interior, panoramic roof, 20" std wheels
InControl Touch Pro Software Version: S19A_19.24.2-375121 Telematics Software Version: 14.2
:?


Delta5
Posts: 41
Joined: Tue Sep 24, 2019 1:32 pm
Location: Midlands

Re: Hardware update gained 15% range

Post by Delta5 » Thu Oct 10, 2019 1:19 pm

The figures are less than I expected, a wheel traveling at 50 mph is spinning at 520 rpm and I chose 20kg as a realistic weight, the wheel diameter was 800mm, an online flywheel energy calculator did the arithmetic and the result is in Joules which convert to kilowatt hours. Increase speed gradually over 10 seconds to get the load in KW for 10 seconds.

Does this sound realistic ?. Spinning a wheel on a bare axle is very easy, if I built a rig with a 10 to 1 gearing could I wind it up by hand to 520 rpm within 10 seconds, yes that is realistic .25 KW or 1/3 hp is well within manual effort.


User avatar
Koala
Posts: 25
Joined: Sun Mar 17, 2019 8:40 pm
Location: Germany - Bavaria

Re: Hardware update gained 15% range

Post by Koala » Thu Oct 10, 2019 7:54 pm

Slightly off-topic here, but maybe of interest: Living on the continent, we do change wheels from Summer to Winter tiers and back. (Not mandated by law, but highly recommended).
The consumption for my weekly commute between Nuremberg and Munich:

Summer tires: 18” (factory standard) : 22kW/100Km average consumption

Winter tires: 18” (Pirelli Scorpion Winter): 25kW / 100Km average consumption

So with the same tire size the winter wheels increase energy consumptions by ~13%. The Pirellis have a C-rating for energy efficiency. Considering the slightly higher speed that I can drive on dry summer roads than wet winter roads the difference may be close to 15%. This experience is in line with all diesel cars I had over the past decades.
2019 I-Pace S, Firenze Red, Light Oyster Interieur, picked up March 14th, 2019
InControl: 19B_19.40.4-436082 | Telematics: 17.2 | > 25.000 KM of happy I-Pace driving


Chewy
Posts: 1904
Joined: Tue Nov 06, 2018 5:46 pm
Location: Forest of Dean. UK.

Re: Hardware update gained 15% range

Post by Chewy » Thu Oct 10, 2019 8:36 pm

Delta5 wrote:
Thu Oct 10, 2019 1:19 pm
The figures are less than I expected, a wheel traveling at 50 mph is spinning at 520 rpm and I chose 20kg as a realistic weight, the wheel diameter was 800mm, an online flywheel energy calculator did the arithmetic and the result is in Joules which convert to kilowatt hours. Increase speed gradually over 10 seconds to get the load in KW for 10 seconds.

Does this sound realistic ?. Spinning a wheel on a bare axle is very easy, if I built a rig with a 10 to 1 gearing could I wind it up by hand to 520 rpm within 10 seconds, yes that is realistic .25 KW or 1/3 hp is well within manual effort.
Once rotating ar a fixed speed it won't take much energy to keep it there. It is acceleration that requires the energy...

Put simply F = mA. Where F = force. m = Mass and A = Accel

However, because the wheel is a rotating mass it is somewhat more complex.


User avatar
anorak
Posts: 411
Joined: Sun Feb 03, 2019 10:56 pm
Location: Cambs. UK

Re: Hardware update gained 15% range

Post by anorak » Thu Oct 10, 2019 9:47 pm

Koala wrote:
Thu Oct 10, 2019 7:54 pm
Slightly off-topic here, but maybe of interest: Living on the continent, we do change wheels from Summer to Winter tiers and back. (Not mandated by law, but highly recommended).
The consumption for my weekly commute between Nuremberg and Munich:

Summer tires: 18” (factory standard) : 22kW/100Km average consumption

Winter tires: 18” (Pirelli Scorpion Winter): 25kW / 100Km average consumption

So with the same tire size the winter wheels increase energy consumptions by ~13%. The Pirellis have a C-rating for energy efficiency. Considering the slightly higher speed that I can drive on dry summer roads than wet winter roads the difference may be close to 15%. This experience is in line with all diesel cars I had over the past decades.
I'd imagine the average summer temperature being around 20 degrees warmer than winter in your part of the world has a far greater bearing on efficiency than tyre choice.

I tend to get a 20% improvement in the summer on the same wheels and tyres as I have in winter (22kWh/100km in summer, 26kWh/100km in winter strangely enough).
I Pace EV400 S, Caesium blue, Oyster leather, 18" wheels
MY19, delivered 01/2019
IMC: S19B_19.40.4-436082 || Telematics: 17.2
Now on its 2nd front EPIC


Delta5
Posts: 41
Joined: Tue Sep 24, 2019 1:32 pm
Location: Midlands

Re: Hardware update gained 15% range

Post by Delta5 » Thu Oct 10, 2019 9:57 pm

The calculation longhand takes up most of a A4 page, a wheel rotating needs no energy other than to overcome mechanical friction and aerodynamic drag - zero. So the only energy absorbed is accelerating for 10 seconds nothing else counts.
The original controversy was that a heavy wheel absorbs more energy than a lighter one - it does but the difference is so small it can be ignored


Jan073
Posts: 91
Joined: Thu May 03, 2018 10:28 pm
Location: Netherlands

Re: Hardware update gained 15% range

Post by Jan073 » Sat Oct 12, 2019 8:20 am

I’ll just head to the gym and loose the weight myself, the 22 are a keeper :-p
FE Corris grey ebony/ebony 22” summer / 20” winter | NL


Post Reply

Return to “Main Jaguar I-Pace chat”