Stupid things non petrolheads say... Vol 2

[MartG]

What The Deuces said:

Nomme de Plum said:

Could you show your working to evidence please as I do not see the logic in your statement.

Have you taken into account the extra losses of the heavier vehicle? e.g. drive train losses, friction and drag.

Just consider which of those are directly influenced by mass

Ummm...all of them

Heavier vehicle puts more load through the transmission, so increased frictional losses

Friction - greater load on bearings and tyres creates more friction there too

Drag - heavier vehicles tend to be larger, so increased drag too

MartG B.Eng

[What The Deuces]

MartG said:

Ummm...all of them

Heavier vehicle puts more load through the transmission, so increased frictional losses

Friction - greater load on bearings and tyres creates more friction there too

Drag - heavier vehicles tend to be larger, so increased drag too

MartG B.Eng

Given you can measure transmission loss on a dyno ( separate to the car ) then I dont think so - we may have differing concepts of transmission loss

Drag - in my example, loading an extra 1000kg in my van isn't going to change the drag now is it....(if anything it'll settle a bit lower and have less frontal area lol)

Rolling Friction does increase with weight Fr = cW

Edited by What The Deuces on Monday 24th April 10:40

[GT9]

MartG said:

Ummm...all of them

Heavier vehicle puts more load through the transmission, so increased frictional losses

Friction - greater load on bearings and tyres creates more friction there too

Drag - heavier vehicles tend to be larger, so increased drag too

MartG B.Eng

It's disingenuous to respond to a statement about the direct influence of mass and include drag.

[Nomme de Plum]

What The Deuces said:

MartG said:

Ummm...all of them

Heavier vehicle puts more load through the transmission, so increased frictional losses

Friction - greater load on bearings and tyres creates more friction there too

Drag - heavier vehicles tend to be larger, so increased drag too

MartG B.Eng

Given you can measure transmission loss on a dyno ( separate to the car ) then I dont think so - we may have differing concepts of transmission loss

Drag - in my example, loading an extra 1000kg in my van isn't going to change the drag now is it....(if anything it'll settle a bit lower and have less frontal area lol)

Rolling Friction does increase with weight Fr = cW

Edited by What The Deuces on Monday 24th April 10:40

These two articles disagree with your assertion plus wiki link

1) Extra weight causes a greater deformation of the sidewalls and tread of a tire, thus, increasing the rolling resistance. Rolling resistance increases in direct proportion to the weight that the wheel supports, and is equal to about 0.3 to 0.5 percent of the load on the wheel.


2) Load: Road resistance increases directly with load. The coefficient is 0.01. This means a 1,000-lb increase in a car's load will increase rolling resistance by 10 lb. Reducing this component of resistance depends more on vehicle weight than the tires.

https://en.wikipedia.org/wiki/Rolling_resistance

Edited by Nomme de Plum on Monday 24th April 12:08

[Nomme de Plum]

GroundEffect said:

It depends how the weight is being achieved. If it's from a larger battery, then it probably can be recovered - since bigger batteries tend to have high power charge/discharge capabilities. If it's purely through bigger vehicle/inefficient body design then probably not.

For normal driving, having rear-only regen isn't much of an issue. Just brake lighter and earlier and not engage the friction brakes (if they're using series vs parallel braking).

The recovery is limited to the ability of the motors to generate and the batteries to accept that load in an extremely short time frame.

I'm suggesting that the instantaneous braking energy cannot be absorbed by the system quickly enough.

[What The Deuces]

Nomme de Plum said:

What The Deuces said:

MartG said:

Ummm...all of them

Heavier vehicle puts more load through the transmission, so increased frictional losses

Friction - greater load on bearings and tyres creates more friction there too

Drag - heavier vehicles tend to be larger, so increased drag too

MartG B.Eng

Given you can measure transmission loss on a dyno ( separate to the car ) then I dont think so - we may have differing concepts of transmission loss

Drag - in my example, loading an extra 1000kg in my van isn't going to change the drag now is it....(if anything it'll settle a bit lower and have less frontal area lol)

Rolling Friction does increase with weight Fr = cW

Edited by What The Deuces on Monday 24th April 10:40

These two articles disagree with your assertion plus wiki link

1) Extra weight causes a greater deformation of the sidewalls and tread of a tire, thus, increasing the rolling resistance. Rolling resistance increases in direct proportion to the weight that the wheel supports, and is equal to about 0.3 to 0.5 percent of the load on the wheel.


2) Load: Road resistance increases directly with load. The coefficient is 0.01. This means a 1,000-lb increase in a car's load will increase rolling resistance by 10 lb. Reducing this component of resistance depends more on vehicle weight than the tires.

https://en.wikipedia.org/wiki/Rolling_resistance

Edited by Nomme de Plum on Monday 24th April 12:08

1) Pump up the tyres ;-)
2) As above Fr = cW


Still cant wait to hear about drivetrain losses and drag being linked to the weight of the car.

[GroundEffect]

Nomme de Plum said:

GroundEffect said:

It depends how the weight is being achieved. If it's from a larger battery, then it probably can be recovered - since bigger batteries tend to have high power charge/discharge capabilities. If it's purely through bigger vehicle/inefficient body design then probably not.

For normal driving, having rear-only regen isn't much of an issue. Just brake lighter and earlier and not engage the friction brakes (if they're using series vs parallel braking).

The recovery is limited to the ability of the motors to generate and the batteries to accept that load in an extremely short time frame.

I'm suggesting that the instantaneous braking energy cannot be absorbed by the system quickly enough.

For normal driving, it very much can.

[Nomme de Plum]

What The Deuces said:

Nomme de Plum said:

What The Deuces said:

MartG said:

Ummm...all of them

Heavier vehicle puts more load through the transmission, so increased frictional losses

Friction - greater load on bearings and tyres creates more friction there too

Drag - heavier vehicles tend to be larger, so increased drag too

MartG B.Eng

Given you can measure transmission loss on a dyno ( separate to the car ) then I dont think so - we may have differing concepts of transmission loss

Drag - in my example, loading an extra 1000kg in my van isn't going to change the drag now is it....(if anything it'll settle a bit lower and have less frontal area lol)

Rolling Friction does increase with weight Fr = cW

Edited by What The Deuces on Monday 24th April 10:40

These two articles disagree with your assertion plus wiki link

1) Extra weight causes a greater deformation of the sidewalls and tread of a tire, thus, increasing the rolling resistance. Rolling resistance increases in direct proportion to the weight that the wheel supports, and is equal to about 0.3 to 0.5 percent of the load on the wheel.


2) Load: Road resistance increases directly with load. The coefficient is 0.01. This means a 1,000-lb increase in a car's load will increase rolling resistance by 10 lb. Reducing this component of resistance depends more on vehicle weight than the tires.

https://en.wikipedia.org/wiki/Rolling_resistance

Edited by Nomme de Plum on Monday 24th April 12:08

1) Pump up the tyres ;-)
2) As above Fr = cW


Still cant wait to hear about drivetrain losses and drag being linked to the weight of the car.

You have still not evidenced your statement:

"As I originally said, Regen is more effective in heavier cars. I doubt that would have been achievable had the kerb mass been 2000lbs all up."

So how will you show us this?

Tyres are inflated to manufacturers recommendations so the deformation still occurs.

Most of us don't drive vans and in general a 2000kg car will be bigger than a 1000kg vehicle. So yes drag will have an impact.

Additional friction caused by weight in the drive train has already been explained to you.

[GT9]

Nomme de Plum said:

The recovery is limited to the ability of the motors to generate and the batteries to accept that load in an extremely short time frame.

I'm suggesting that the instantaneous braking energy cannot be absorbed by the system quickly enough.

The magnitude of instantaneous power to recover kinetic energy during braking is defined by the speed you are travelling at, the mass of the car and the desired deceleration rate, in exactly the same way it was added in the first place. There are of course losses to take into account and there is also a consideration regarding voltage headroom to drive current back to the battery, the latter being dealt with in the power electronics. However for the purpose of this discussion, the only equation that you are really concerned with is that kinetic energy = 0.5 x m x v^2 which defines a rule of thumb for the instantaneous power to accelerate or decelerate the car as 6 bhp per ton per g per mph.

The square law relationship between kinetic energy and speed, combined with low motor back-emf at low rotational speeds means that the regen is not very effective (nor does it need to be) at very low road speeds. It doesn't need to be because the kinetic energy is so low, such that you are not losing out much by it being ineffective. Where it matters is at the start of the braking event from higher road speeds.

The question to ask yourself is this, do you find that you normally brake at deceleration rates greater than you accelerate at? I'm not talking about emergency braking, I'm talking about 99% of the time when you are not doing an emergency brake. If the answer is, 'most of the time I decelerate at similar rates to what I accelerate at', then regen is perfectly viable for 99% of the time. Which means that 99% of the time the system does have enough capacity to absorb the kinetic energy, because it had enough capacity to add it in the first place. These change of speed events are usually discharging and recharging the battery by less than 1% of its rated capacity in pure EVs. It's an absolute non-event in terms of what energy the battery can absorb.

The reason EVs have high peak power ratings is because the short-duration power required to accelerate and decelerate is relatively high, i.e. relative to cruise power. But it's not higher than what the system can cope with for these events that are a few seconds long. Compare that with the minutes or hours it actually takes to recharge the battery, which can be done at many tens or hundreds of kWs.

[GT9]

And for reference, 1g acceleration or deceleration is 22 mph change in speed per second.

[Freddie Fitch]

Good grief.
Three pages of argument about electric cars. Surely there's a separate thread for that?
Can we please remember this thread's title?

And can we return to diesel motorbikes which do of course exist.

[MartG]

What The Deuces said:

Given you can measure transmission loss on a dyno ( separate to the car ) then I dont think so - we may have differing concepts of transmission loss

Drag - in my example, loading an extra 1000kg in my van isn't going to change the drag now is it....(if anything it'll settle a bit lower and have less frontal area lol)

Rolling Friction does increase with weight Fr = cW

Edited by What The Deuces on Monday 24th April 10:40

Why does the fact that it can be measured on a dyno make you think it doesn't alter with load ?

At no point earlier in this discussion was it stipulated that the 'heavy' and 'light' vehicles were the same vehicle.

[What The Deuces]

MartG said:

At no point earlier in this discussion was it stipulated that the 'heavy' and 'light' vehicles were the same vehicle.

Even if they're not, it not the weight that's affecting the drag, I just used the example of the van to make it clear

[What The Deuces]

Nomme de Plum said:

You have still not evidenced your statement:

"As I originally said, Regen is more effective in heavier cars. I doubt that would have been achievable had the kerb mass been 2000lbs all up."

So how will you show us this?

Tyres are inflated to manufacturers recommendations so the deformation still occurs.

Most of us don't drive vans and in general a 2000kg car will be bigger than a 1000kg vehicle. So yes drag will have an impact.

Additional friction caused by weight in the drive train has already been explained to you.

Just fit the correct spec tyres

Get a tesla with a big battery or a small battery

Does adding weight make the % drive trains losses increase? No

[MartG]

What The Deuces said:

MartG said:

At no point earlier in this discussion was it stipulated that the 'heavy' and 'light' vehicles were the same vehicle.

Even if they're not, it not the weight that's affecting the drag, I just used the example of the van to make it clear

Heavier cars tend to be bigger, with greater frontal area which DOES affect drag

[What The Deuces]

MartG said:

What The Deuces said:

MartG said:

At no point earlier in this discussion was it stipulated that the 'heavy' and 'light' vehicles were the same vehicle.

Even if they're not, it not the weight that's affecting the drag, I just used the example of the van to make it clear

Heavier cars tend to be bigger, with greater frontal area which DOES affect drag

Which is caused by the frontal area being bigger not by the weight.....

[Bungleaio]

Can we get back to what idiots have said down the pub or in the office please?

[GT9]

MartG said:

Heavier cars tend to be bigger, with greater frontal area which DOES affect drag

I posted a picture of a heavy car with outstanding drag characteristics just this morning on this very thread.

[carlo996]

Bungleaio said:

Can we get back to what idiots have said down the pub or in the office please?

But why, we’re just getting to the crux of why EVs are so interesting. I don’t know about you, but I often talk about drag and spreadsheets when people ask me how my drive was

[GT9]

carlo996 said:

But why, we’re just getting to the crux of why EVs are so interesting. I don’t know about you, but I often talk about drag and spreadsheets when people ask me how my drive was

Pie are squared.