Feedback for WIP video

[Killrob]

The final version is out: https://youtu.be/UIQjyn95c-o
Took a while to make :s


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Hey guys!

Maybe you have seen on Facebook that I have been working on a Power & Torque video getting into explaining the fundamentals of what accelerates a car.
The script and amount of effort going into this is really large, so I don't want to make the best out of it. This is where you potentially can help.

I just made a draft recording of the first bit of the video which contains the full physics lecture of it and I'd like to have some feedback on this.

Edit: deleted link to old video

What is not in this video but will be in the finished one I make after getting some feedback:

• Example for idealized combustion engine and electric engines
• Example of realistic combustion engine accelerating a car with drag, looking at gearing and shifting.
• Example with two V12s that are compared, both making the same power but one much more torque than the other.
• Then followed by a 12-question Torque & Power FAQ.

My questions to you:

• Are things presented in an understandable manner, or are there things that need to be clarified?
• How is the pacing? Too fast, too slow, or too fast in some parts and too slow in others?
• Can I improve things? If so, how? The only thing obvious is to in the slides mark parts of the formulae as I talk about them, which I didn't do for this test video.

Thank you for your comments!
Cheers!
/Killrob

[07CobaltGirl]

Quick thought. In your opening forumula sequence, you refer to torque as foot-pounds, when it should be pound-feet, right?

I think the pace is just about right.

[TurboJ]

Quick thought. In your opening forumula sequence, you refer to torque as foot-pounds, when it should be pound-feet, right?

I think the pace is just about right.

Both can be used, correct?

[KLinardo]

Quick thought. In your opening forumula sequence, you refer to torque as foot-pounds, when it should be pound-feet, right?

I think the pace is just about right.

Both can be used, correct?

That's a good question to ask because my understanding is that they cannot both be used.

The measure pound-feet in the imperial system is how many pounds of force are exerted at one foot perpendicularly from the central pivot point. https://en.wikipedia.org/wiki/Pound-foot_%28torque%29
The measure Ft-Lbs actually measures energy. https://en.wikipedia.org/wiki/Foot-pound_%28energy%29

I'm not quite sure which one is the most proper, but I have heard both used and I tend to use Ft-Lbs when talking about cars (although for engines alone, the Lb-Ft measurement might be best). My argument for that choice is the fact that the perpendicular torque on the power axle is translated to linear kinetic energy through the rotational force the wheel exerts on the pavement. That being said, we are now practically at the limits of my knowledge of physics and that's all I really have to contribute. Therefore, I am open to being educated on the subject.

[RobtheFiend]

Isn't it a myth that a longstroke engine has more "torque" than one with shorter stroke?
If both are 2 liter 4 cylinder engines with the same BMEP, then the force working on the piston would be smaller in the longstroke engine, due to the lower area of the piston.
Does that make sense?

[AirJordan]

As a fellow physicist with some (limited) experience with didactics (honest coincidence my assignment was torque) I must say that you did an excellent job.

I would add one thing and this really is nit-picking and purely subjective.
At around 3min when you are talking which torque is really important to us, you could add extra clarification of what that means in engine which would better connect to 5:55 when you say...the amount of work produced in combustion cycle.... My idea is that after boat story you add: so in the engine we are looking at the amount of energy/work it has created in one cycle (something in that way). Or maybe before stories when you are already mentioning engine. It is really hard to be explicit because you did such a great job but I think this is only slightly bigger step you made in understanding.

[Killrob]

Isn't it a myth that a longstroke engine has more "torque" than one with shorter stroke?
If both are 2 liter 4 cylinder engines with the same BMEP, then the force working on the piston would be smaller in the longstroke engine, due to the lower area of the piston.
Does that make sense?

That is definitely something I should add to the FAQ!
What you say is both "true to first order" and "not quite that easy". An engine with more stroke tends to have a lower Helmholtz Resonance, which moves more torque to the low end of the torque curve... so that could actually be a thing and also it could not. It's complicated but yeah, to first order it is a myth.

[Killrob]

As a fellow physicist with some (limited) experience with didactics (honest coincidence my assignment was torque) I must say that you did an excellent job.

I would add one thing and this really is nit-picking and purely subjective.
At around 3min when you are talking which torque is really important to us, you could add extra clarification of what that means in engine which would better connect to 5:55 when you say...the amount of work produced in combustion cycle.... My idea is that after boat story you add: so in the engine we are looking at the amount of energy/work it has created in one cycle (something in that way). Or maybe before stories when you are already mentioning engine. It is really hard to be explicit because you did such a great job but I think this is only slightly bigger step you made in understanding.

Ohh, that is a good point! I should connect those more and already when I compare Torque and "Torque" say that the latter is "The amount of work or energy created in a combustion cycle". The more that point is hammered home the less people will talk about torque and instead focus on what actually matters. Thank you for your comment!

[Leonardo9613]

Quick thought. In your opening forumula sequence, you refer to torque as foot-pounds, when it should be pound-feet, right?

I think the pace is just about right.

Both can be used, correct?

That's a good question to ask because my understanding is that they cannot both be used.

The measure pound-feet in the imperial system is how many pounds of force are exerted at one foot perpendicularly from the central pivot point. https://en.wikipedia.org/wiki/Pound-foot_%28torque%29
The measure Ft-Lbs actually measures energy. https://en.wikipedia.org/wiki/Foot-pound_%28energy%29

I'm not quite sure which one is the most proper, but I have heard both used and I tend to use Ft-Lbs when talking about cars (although for engines alone, the Lb-Ft measurement might be best). My argument for that choice is the fact that the perpendicular torque on the power axle is translated to linear kinetic energy through the rotational force the wheel exerts on the pavement. That being said, we are now practically at the limits of my knowledge of physics and that's all I really have to contribute. Therefore, I am open to being educated on the subject.

Torque and energy are different things, and that's why it was chosen to name them differently, even though dimensionally they are the same, ie you use the same units to express their values. So, using them either way is just a matter of avoiding confusion, something that, as with all other units, was made better by the SI, naming them Nm and J.

[Killrob]

Alright, the final version is out: https://youtu.be/UIQjyn95c-o
That was a lot of work to put together!

[koolkei]

SUPER awesome video killrob. #firstgearproblems

it's a bit OOT i'd like to point out that even electric motors is not perfectly flat in it's torque.
it's MOSTLY flat, up to a point.
i remember seeing an actual electric motor power curve specification.
the one i see DOES NOT have 100% torque at 0RPM, more like 90-95% at 0RPM. and i believe that is also true for most electric motors

i kinda don't know what i meant with this. so incognito text it is. props to those who found this

[Killrob]

Thank you!

[RobtheFiend]

Nice one.

[HighOctaneLove]

Thanks Killrob for this video, I finally understand what you mean by "Torque has nothing to do with it" now!

I believe that this was because you went through the real-life examples and you took the time to simulate both engine sizes and place them in the same car. Can't argue with those stats,

Quick question: Does the shape of the torque curve affect driveability in Automation? For example, is a downwards torque curve scoring a higher driveability in-simulation to an upwards curve or flat curve?

[TrackpadUser]

IIRC, a less peaky torque curve is better for driveability.