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Hello all

I just thought of an interesting concept for technic supercars, that could help compare them properly. As we all know, the real supercar world is a buzz about power to weight ratio figures and such. I know you would probably think this is pointless for a technic supercar, because you would expect its power to weight figure to be so low but, it's still a neat way of comparing them. Because some technic supercars are heavy but powerful and others are the opposite. So I have researched a formula to work out power to weight ratio for real cars, and thus used this for technic models, and have also worked out the power and torque of every modern technic motor: Xl motor, L motor, m motor and possibly RC motors.

Here are some power to weight figures from 2 of my motorized supercars:

My Lamborghini Huracan

*1.3kg

*0.004hp

= 3.08hp per ton

My Mclaren P1

*2.8kg

*0.008hp

= 2.86hp per ton.

As you can see. eventhough my Mclaren has 2 Xl motors and my Lamborghini only has 1, the Lamborghini edges out a better power to weight ratio because its less than half the weight of the Mclaren. Which explains why my Lamborghini is almost twice as fast as the Mclaren (apart from the fact that the Lamborghini has a 3 speed gearbox, 4wd and better gearing, and the Mclaren just has 2 Xl motors powered to a differential.)

Thank you for viewing this topic, if you have any questions feel free to ask. If you have any motorized mocs that you would like me to work out their power to weight ratio, just tell me their weight in kilograms, and how many motors it's power by e.g. 1 Xl motor or 2 L motors. I'm not sure about RC motors but if your moc is powered by RC motors I will try my best to work it out.

LeocornoProductions

Edited by LeocornoProductions

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oooooo

interesting question, but wouldn't the pneumatics be powered by a motor? Or you would need to work out how much rpm the pneumatic engine makes, and also is there a way that you could work out the torque?

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This works basically for any machine. So my fox with 8Xl motors and 4kg weight has a mechanical power to weight ratio of 4,42W/kg.

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I actually just wrote a maths paper on optimizing motor choice and gearing based on weight, similar to the comparison of power to weight we're doing here. I was using drag cars as an example though, would be cool to translate some of those concepts here :classic:.

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Power = Energy x time

Not Quite, instead:

Power = Force × Velocity = Torque × Angular Speed = Energy / Time

How could i measure the power of my pneumatic engines?

Power = (2×3.14×RPM/60) × Torque

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Ok... torque is then F x r i guess. So i need to measure the force a pneumatic piston produces somehow.

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@nicjasno: Simple. Force=Pressure x Area (piston)

Assuming piston diameter D=13 mm

Then piston area becomes 1.3*10^-5 m2

Pressure in Pa= 800 000 at 8bar

Total force= 106.2 N per cylinder.

In order to calculate the total force and torque of the engine, a dynamic analysis has to be made

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Assuming that you only have a one-cylinder LPE, with 1 stud as a turning radius, then Torque= Force x Radius

E.g: M= 106.2 x 0.0078 = 0.8 Nm

Assuming angular velocity in RPM: 2400

Ang V in rads/s: 251.3

Power= Torque x Ang v = 0.8 x 251.3 = 208 watts

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I think efficiency is equally important to power and weight. We saw supercars with okay theoretical power to weight ratio, yet they could hardly crawl.

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I claim that motorised drive is not a prerequisite of being a supercar. Sure most MOCs would have this feature, but I wouldn't necessarily disqualify a creation from supercar status just because it doesn't have a drive motor (all other elements being in place).

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Assuming that you only have a one-cylinder LPE, with 1 stud as a turning radius, then Torque= Force x Radius

E.g: M= 106.2 x 0.0078 = 0.8 Nm

Assuming angular velocity in RPM: 2400

Ang V in rads/s: 251.3

Power= Torque x Ang v = 0.8 x 251.3 = 208 watts

Are you sure? because 208 watts is almost 0.3 horsepower, and thats almost 9 times the power of Zblj's fox with 8 Xl motors. What type of pneumatic engine are you talking about? is it the standard one with 2-3 pneumatic cylinders, or one of those beefed up lpe powered v8 replica's that can rev over 1000rpm.

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@LeocornoProductions: I have a Masters' degree in Machine design, so I'm sure about it. Dont you mean 0.16 HP?

If you have a look at my calculations, I'm talking about a single cylinder LPE peaking at 2400 rpm at 8 bars ;) so in theory, it sure is true. However, in reality it would differ due to friction, gearing, and vibrations :)

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@LeocornoProductions: I have a Masters' degree in Machine design, so I'm sure about it. Dont you mean 0.16 HP?

If you have a look at my calculations, I'm talking about a single cylinder LPE peaking at 2400 rpm at 8 bars ;) so in theory, it sure is true. However, in reality it would differ due to friction, gearing, and vibrations :)

Ow Earth life, makes most things worse. I like this idea to calculate the power to weight ratio.

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epic technic, I'm really impressed by your radical as well, but I can't watch the video because my phone is playing up and my laptop is really laggy, but would you like me to work out the power to weight ratio of your radical? I heard that it has 4 L motors!

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Pneumatic's are strong. I don't even need to build an LPE to know this. But lets say that the LEGO DC motor is going to have a maximum of 600N/132lbs of force @12V, Would LPE be (A) stronger (B) roughly the same or © weaker.

I made a video awhile back doing some Horse Power calculations on a couple of LEGO vacuum engines and the LEGO XL motor with my 18V drill motor. I don't know if the calculations are correct so if anyone can see if it is please be my guest. But this is dealing with the HP in engines.

I just thought of an interesting concept for technic supercars, that could help compare them properly. As we all know, the real supercar world is a buzz about power to weight ratio figures and such. I know you would probably think this is pointless for a technic supercar, because you would expect its power to weight figure to be so low but, it's still a neat way of comparing them. Because some technic supercars are heavy but powerful and others are the opposite. So I have researched a formula to work out power to weight ratio for real cars, and thus used this for technic models, and have also worked out the power and torque of every modern technic motor: Xl motor, L motor, m motor and possibly RC motors.

Thank you for viewing this topic, if you have any questions feel free to ask. If you have any motorized mocs that you would like me to work out their power to weight ratio, just tell me their weight in kilograms, and how many motors it's power by e.g. 1 Xl motor or 2 L motors. I'm not sure about RC motors but if your moc is powered by RC motors I will try my best to work it out.

LeocornoProductions

Hi, I have some questions. Everyone is free to answer them but this First question is for you Leo, How would you define properly? Can you provide in real life examples of Power to weight Ratios with Lego comparisons and then provide a intriguing analysis of it? Also what is the goal for doing this and what ways could you go about using this.

-snip- and have also worked out the power and torque of every modern technic motor: Xl motor, L motor, m motor and possibly RC motors.-snip-

Another Question here, did you do this yourself or is your work based on the information provided on Philo's 9V motor comparison?

I actually just wrote a maths paper on optimizing motor choice and gearing based on weight, similar to the comparison of power to weight we're doing here. I was using drag cars as an example though, would be cool to translate some of those concepts here :classic:.

That sounds interesting. Do you have plans on putting up a digital version of your paper up on EB. Dragsters are a great Examples its just basically an one badass engine connected directly to the drive axle with a clutch break in between.

I claim that motorised drive is not a prerequisite of being a supercar. Sure most MOCs would have this feature, but I wouldn't necessarily disqualify a creation from supercar status just because it doesn't have a drive motor (all other elements being in place).

Yea. I agree Captain, just because the Lego Supercar don't have a motor, theoretically you could still calculate the theoretical Horse Power of the little grey engine block.

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Hi

I see you have many questions, but I will anwser the questions directed towards me. First, people like me like to compare other motorized mocs and the power to weight ratio figures can help me and other people compare them, maybe racing them would be proper, but their aren't many people eligible to race mocs, due to providing instructions etc. In the real supercar world, it's a buzz about power to weight ratios, because supercars always racing each other and such. But the best example is the bugatti veyron supersport vs koenigsegg agera r. At first it was difficult to compare these cars because no one knew what the koenigsegg was capable of speedwise (well now we know that it can do 186mph in 14.53 seconds and 200mph in under 18 seconds), but the koenigsegg has a power to weight ratio of 794hp per ton and the veyron has just over 600hp per ton. Power to weight ratio is useful for comparing modern, cars because comparing 2 cars from different decades is innacurate with power to weight ratios. The mclaren f1 has a power to weight ratio better than the original veyron, yet the veyron destroyed it in a race. Power to weight ratio comparisons are often 60% right for whether 1 car is faster than another overall. But power to weight ratios are 100% useful for comparing modern cars acceleration. Let me give you a statement I have just come up with, a supercar with a power to weight ratio from 300-420 horsepower per ton will have an acceleration to 60 mph from 3-4 seconds, a modern supercar with more than that will accelerate almost as quickly as a hypercar e.g. Lamborghini aventador, ferrari f12, Mclaren 650s, Lamborghini Huracan, ferrar 458 speciale, noble m600. A modern hypercar with a power to weight ratio over 500hp per ton will do 60mph in under 3 seconds and 100mph in under 6 seconds, and a modern hypercar with over 650hp per ton will be significantly faster than than the 2005 bugatti veyron in terms of acceleration, and a modern hypercar with over 700hp per ton will accelerate faster than a bugatti veyron supersport.

Second, the lego technic power functions website shows how much rpm and torque each motor makes, and there was this online calculator which used rpm and torque to workout horsepower and watts, thus I used the formula for working out power to weight ratio for cars. And applied all of this for working out technic power to weight ratio. Does this anwser your questions?

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