Formula E

Please discuss here all your remarks and pose your questions about all racing series, except Formula One. Both technical and other questions about GP2, Touring cars, IRL, LMS, ...
Tommy Cookers
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Re: Formula E

Post by Tommy Cookers » Mon Jan 21, 2019 12:11 pm

F1 has a fuel rate limit for every rpm
the rate reduces disproportionately at rpm below 10500 so the engine is prevented by rule from using constant torque running
if gears were banned the cars could manage without them - but for this rule

the EM is the extreme opposite
the torque-producing 'fuel' is current - which seems to be unlimited by rule eg at low rpm
so the performance characteristics of the EM and the EM drive notionally appear to form a complete substitute for gears

the big question (which no-one addresses) is ......
the designer-chosen current (torque) limits in the EM drive vs. the designer-chosen voltage (rpm) limits in the EM drive .....
if there's no conflict between these factors and others - I'd certainly like to know how there isn't

mzso
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Re: Formula E

Post by mzso » Mon Jan 21, 2019 2:42 pm

Tommy Cookers wrote:
Mon Jan 21, 2019 10:48 am
constant torque ICEs have been made and they worked
F1 is constant torque design but fuel rate is rigged to prevent constant torque running and compel traditional 'racy' running
Huh? That's inherently impossible for ICEs.

Tommy Cookers
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Re: Formula E

Post by Tommy Cookers » Mon Jan 21, 2019 3:05 pm

can you explain how it's inherently impossible ??
how is torque not constant if charge is constant and fuelling/rev is constant ? ..... and btw ....

some ICEs have been designed for 'better than constant torque' running ie 'constant power' running (like EVs)
differentially-boosted or similar CI engines having extra torque at start/low rpm enabling gearless locos (or trucks)
ie 'constant power' running like Paxman Hi-Dyne engined locos on the Sierra Leone railways until 1974
the F1 ICE could even be run like this - but the fuelling rules deliberately force it to the opposite 'traditional' extreme
of course neither the above nor real EVs are run 'constant power' down to zero rpm - neither has infinite starting torque

but to be on-thread - any answers to my question about EMs and their drives ?

mzso
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Re: Formula E

Post by mzso » Mon Jan 21, 2019 6:17 pm

@Tommy Cookers

Ever saw a torque curve of an ICE?

Tim.Wright
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Re: Formula E

Post by Tim.Wright » Mon Jan 21, 2019 8:19 pm

Turbo diesels have E-motor like characteristics apart from both extremes of the rev range.

In fact any turbo ICE has a pretty flat torque response apart from the extremes.

Obviously they can't replicate the stall torque or the constant power torque roll-off that an E-motor has.
Not the engineer at Force India

Andres125sx
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Re: Formula E

Post by Andres125sx » Mon Jan 21, 2019 8:33 pm

Tommy Cookers wrote:
Mon Jan 21, 2019 12:11 pm
F1 has a fuel rate limit for every rpm
the rate reduces disproportionately at rpm below 10500 so the engine is prevented by rule from using constant torque running
if gears were banned the cars could manage without them - but for this rule

the EM is the extreme opposite
the torque-producing 'fuel' is current - which seems to be unlimited by rule eg at low rpm
so the performance characteristics of the EM and the EM drive notionally appear to form a complete substitute for gears

the big question (which no-one addresses) is ......
the designer-chosen current (torque) limits in the EM drive vs. the designer-chosen voltage (rpm) limits in the EM drive .....
if there's no conflict between these factors and others - I'd certainly like to know how there isn't
Sorry Mr. Cookers but you´re concluding that those particular characteristics of the restricted F1 ICEs are the normal behaviour of an ICE. Even that same F1 ICE would be very different if not restricted by rules, and the torque curve would be far from flat

That´s the reason there are very different ICE for very different tasks, they need to optimize the power band for different rpm ranges. OTOH EMs work at max torque for a much wider range of rpm so they´re infinitely more versatile and the reason except size they the same no matter how different is the task

Tommy Cookers
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Re: Formula E

Post by Tommy Cookers » Mon Jan 21, 2019 8:40 pm

the crankshaft torque of the NA 3.8 litre Jaguar XK150S (a sportscar) was in 3rd gear at ....
(617 rpm) 10 mph 176 lb ft, 20 mph 186 lb ft, .... 40 mph 200 lb ft, 60 mph 209 lb ft, and (4936 rpm) 80 mph 211 lb ft
pretty close to constant torque
with a weak electric supercharger and F1-style control of ignition timing etc it could be dead constant torque

or even work nearer to constant power - a bit like an EV
the Paxman Hi-Dyne torque curve was notionally constant power throughout its working rpm range
(that range being limited by wheel slip - the lower range capability of the motor was not endorsed)
of course the locos were 'clutched' by a fluid coupling (non-torque multiplying)

the original diesel loco the (V4 reversible 2 stroke) Borsig-Sulzer Thermolokomotiv of 1912 had (rigid) direct drive
it ran by compressed air motor action to 7 kph - there commenced diesel motor action at maybe 100 rpm

even with normalised charge at 0 rpm torque would be less as heat addition would need to be later to contain pressure peak
torque could be maintained by increased charge and fuel - but necessary heat dilution would demand further charge increase
incipient resonance (surge) in path between motor and load could increase load and stall the vehicle
the EV design must also deal with some of these issues
Last edited by Tommy Cookers on Wed Jan 23, 2019 1:01 pm, edited 1 time in total.

Andres125sx
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Re: Formula E

Post by Andres125sx » Mon Jan 21, 2019 8:57 pm

Tim.Wright wrote:
Mon Jan 21, 2019 8:19 pm
Turbo diesels have E-motor like characteristics apart from both extremes of the rev range.

In fact any turbo ICE has a pretty flat torque response apart from the extremes.

Obviously they can't replicate the stall torque or the constant power torque roll-off that an E-motor has.
I think we have different concepts about what a flat curve is :)

Tim.Wright
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Re: Formula E

Post by Tim.Wright » Mon Jan 21, 2019 9:31 pm

Andres125sx wrote:
Mon Jan 21, 2019 8:57 pm
I think we have different concepts about what a flat curve is :)
Image
Image
Image
Image
Not the engineer at Force India

marmer
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Re: Formula E

Post by marmer » Mon Jan 21, 2019 10:13 pm

Anyone else share my view that the gen 3 car should be as slippery as possible with basically no downforce just focus on least air resistance.

Gain the corner performance from AWD and fancy hi tech suspension

Skippon
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Re: Formula E

Post by Skippon » Mon Jan 21, 2019 10:39 pm

EV are not constant torque but constant power!!!
Since power is the torque x speed they have much more acceleration from zero speed. But there is a limit to torque at low speed and that is traction!!!
So EV motor designers refer to a speed knee point. Below a certain speed you are constant torque - traction limited; above the knee - power limited falling torque. Set your gear ratio to match!

Tommy Cookers
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Re: Formula E

Post by Tommy Cookers » Mon Jan 21, 2019 11:57 pm

Andres125sx wrote:
Mon Jan 21, 2019 8:33 pm
....... OTOH EMs work at max torque for a much wider range of rpm so they´re infinitely more versatile and the reason except size they the same no matter how different is the task
the FE task helps the designer of EMs and their drives because the rpm and torque range is small as the max speeds are low
torque needs current and rpm needs voltage

that's why the electrical energy efficiency of gearless road (or F1/Le Mans) EV acceleration will be lower than that in FE

Andres125sx
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Re: Formula E

Post by Andres125sx » Tue Jan 22, 2019 7:27 am

Tim.Wright wrote:
Mon Jan 21, 2019 9:31 pm
Andres125sx wrote:
Mon Jan 21, 2019 8:57 pm
I think we have different concepts about what a flat curve is :)
http://images.pistonheads.com/nimg/3225 ... ueGr-L.jpg
http://paultan.org/images.paultan.org/u ... _graph.jpg
http://www.cumminshub.com/img/figures/2 ... -graph.png
Ok, if you take a heavily oversized engine (wich is oversized exactly to fullfill the bottom end and make the curve flatter) wich will be used at a small fraction of its capabilities 99.999% of its lifespan, then ok, that´s more or less flat.

But in the real world what 99% of people use is this...
Image

Flat at a 25% of its rpm range as much, that´s far from a flat curve

Andres125sx
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Re: Formula E

Post by Andres125sx » Tue Jan 22, 2019 7:36 am

Tommy Cookers wrote:
Mon Jan 21, 2019 11:57 pm
Andres125sx wrote:
Mon Jan 21, 2019 8:33 pm
....... OTOH EMs work at max torque for a much wider range of rpm so they´re infinitely more versatile and the reason except size they the same no matter how different is the task
the FE task helps the designer of EMs and their drives because the rpm and torque range is small as the max speeds are low
torque needs current and rpm needs voltage
Sorry but both statements are wrong. Torque needs power, not current, and power can be produced with high voltage and low current, low voltage and high current, or both similar.

And rpm don´t need voltage at all either, I fly RC planes with a motor that spins at 40k rpm with a 14V battery. IMHO 40k rpm is high rpm, and 14V low voltage

marmer
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Re: Formula E

Post by marmer » Tue Jan 22, 2019 12:00 pm

Not quite a fair comparison. A plane prop doesn't deal with friction on the blades to the same degree a wheel has to with the contact with the ground. The force that acts against it is the mass of the plane plus it's wind resistance. The prop will spin as fast as you ask it to do regardless of speed of the plane. A tyre has constant friction from the ground trying to slow it down.

Rambling but the point is electric props don't need a great deal of power to spin as fast as they can. They are only push/pulling air.

But the points about power cuvrs and stuff at the end of the day once you have a sufficient power to weight ratio having more power low down in the rev range is pointless you would just end up doing burnouts.

Until battery technology gets amazing it's going to be though to get F1 speeds for a full race out of just electric power the batteries are adding too much weight. Making more powerful motors will just waste battery iand add weight.