Reel Physics: xXx: State of the Union - Riding the Rails

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xXx: State of the Union - Riding the Rails

Hop in the backseat with Colby and Jason as they find out if you can indeed ride the rails.

Watch Video

Hey Everyone, we grabbed a pretty crazy scene this week for you and had a good time making this one. I hope you guys like it.
Remember to tell your friends about the show.
Also, welcome to all the new audience members who might have discovered our show from PAX East!
Thanks again for watching!
Jason Dean
REEL PHYSICS

Haha, loved how you guys inserted yourselves into the scene, freaking hilarious. Also, regarding the math here, wow. Aside from the ridiculousness of him having a one-of-a-kind car he got from a chop shop (iirc), and being able to get it onto the rails without dying, it's actually possible to go that fast on rails with that car. Neat.

All assuming the lightweight vehicle could survive a 160 mph turn over obstacles without flipping...

And the drive shaft not disintegrating as those speeds...

This would theoretically work... huh.

v sub ice cubed... I see what you did there.

aeric90:
v sub ice cubed... I see what you did there.

Damn! Beat me to it! So wait! That's not actually the equation?

Not that it mattered given the results, but you didn't even mention the effect of the trains slipstream. The closer to the train he got the less and less drag he'd have.

I've got one question...

How do you turn this on?

Well, the power delivery is only one thing. The major drag in here is air resistance, which is actually completely played out by the train. The train would drag a giant bubble of still air, so if he manages to get his car into that, a reasonably fast car could easily catch up.

Ukomba:
Not that it mattered given the results, but you didn't even mention the effect of the trains slipstream. The closer to the train he got the less and less drag he'd have.

Yeah but that would have meant a whole other set of equations to keep track of.

My first question would be the width of the wheels. North American(and most of the world) Train tracks are spaced 4 ft 8 1⁄2 in, 56 inches The Cobra had a width of 68 inches so unless the wheels were running two feet into the car it would run down the outside of the tracks, or with one wheel on the tracks and one off.

vice3

Hehe. Did you start with that and look for a way to incorporate into your show, or was it a happy discovery while writing/filming?

I think my favourite part of that whole thing was the outtakes. I almost did a spit take right at the end.

DVS BSTrD:

Ukomba:
Not that it mattered given the results, but you didn't even mention the effect of the trains slipstream. The closer to the train he got the less and less drag he'd have.

Yeah but that would have meant a whole other set of equations to keep track of.

What, no CSI scream? :O

Ukomba:

DVS BSTrD:

Ukomba:
Not that it mattered given the results, but you didn't even mention the effect of the trains slipstream. The closer to the train he got the less and less drag he'd have.

Yeah but that would have meant a whole other set of equations to keep track of.

What, no CSI scream? :O

You know what? You're right: Reel Physics has earned that distinction by now :P
We'll see what they have to offer next week -_^

burningdragoon:
vice3

Hehe. Did you start with that and look for a way to incorporate into your show, or was it a happy discovery while writing/filming?

A happy discovery! Sometimes the comedy just writes itself!
Jason Dean
REEL PHYSICS

Lord Hosk:
My first question would be the width of the wheels. North American(and most of the world) Train tracks are spaced 4 ft 8 1⁄2 in, 56 inches The Cobra had a width of 68 inches so unless the wheels were running two feet into the car it would run down the outside of the tracks, or with one wheel on the tracks and one off.

We gave them credit on that. Of course train tracks are not equal to almost any vehicle wheel spacing... but we just figured most everyone knew that. You also can't stand up in a car going 160mph and can't violently turn at that speed either. What we find interesting in scenes is getting down to the stuff that really is calculable... and not the stuff that we consider common knowledge. If we were a more mainstream show, we might have to dumb it down I guess and actually spell out all the problems with a scene... but, hey.... THIS IS THE ESCAPIST COMMUNITY!! ;)

Jason Dean
REEL PHYSICS

ReelPhysics:
xXx: State of the Union - Riding the Rails

Hop in the backseat with Colby and Jason as they find out if you can indeed ride the rails.

Watch Video

Please start superimposing yourself into every scene you test. Even if it's just a reaction shot or something, it was hilarious.

Mouse_Crouse:

ReelPhysics:
xXx: State of the Union - Riding the Rails

Hop in the backseat with Colby and Jason as they find out if you can indeed ride the rails.

Watch Video

Please start superimposing yourself into every scene you test. Even if it's just a reaction shot or something, it was hilarious.

What's more absurd than us riding in the car with Ice Cube... is the car has no back seat!! LOL!

Jason Dean
REEL PHYSICS

Hilarious episode ones again xD
Loved the part with you guys inserting yourselves into the back of the car :D

Would it be possible to try and figure out if a bullet that's beeing sliced in half, by a sword (several movies do this), if the halves then fly past the head on each side?
I think I saw a video on TV in some crazy stunt show or something where someone sliced a bullet, with a sword, that went past him but that didn't cover how wide the bullet pieces then flew from each other...

Top Gear actually refitted two cars in order to have them drive on train tracks:

I love the wheelspin when they first set off!

In this case, James has the exact same observation; with what little traction you get from metal on metal, four-wheel drive provides twice as much acceleration as rear-wheel drive.

I thought the bigger challenge might have been the lose of the tires. If you are losing 3 inches off of the radius of each wheel due to the lose of the tire, then you would need to have the engine/drive train/gear box/etc... run around 25% faster to maintain the same speed. But if the car was suppose to have a top speed of 260mph, even that wouldn't be impossible to overcome.

Please more of you guys inserting yourselves into the videos. Hilarious.

You guys didn't take into account the aerodynamic effect the train had on the car, once you get close enough and slip into the slip stream of the air it's displacing he would definitely have no issues keeping up with the train.

Guffe:
Hilarious episode ones again xD
Loved the part with you guys inserting yourselves into the back of the car :D

Would it be possible to try and figure out if a bullet that's beeing sliced in half, by a sword (several movies do this), if the halves then fly past the head on each side?
I think I saw a video on TV in some crazy stunt show or something where someone sliced a bullet, with a sword, that went past him but that didn't cover how wide the bullet pieces then flew from each other...

Ryan Reynold's character did that in X-Men Origins Wolverine. The halves of the bullet then flew by him, each hitting and killing 2 people.

It was unveiled at the Too-thfairy?

How about slicing bullets in half, which then magically makes them fly WAY off to the sides, instead of into the ninja wielding the sword?

synobal:
You guys didn't take into account the aerodynamic effect the train had on the car, once you get close enough and slip into the slip stream of the air it's displacing he would definitely have no issues keeping up with the train.

Ukomba already mentioned that, post #7.

OT: Hell of a ride, guys. As stated, the ride along was great, as well as the Ice Cubed *actor knowing smile* sequence. Interesting material and entertaining edit'ing. Keep it up!

Dan W:
I thought the bigger challenge might have been the lose of the tires. If you are losing 3 inches off of the radius of each wheel due to the lose of the tire, then you would need to have the engine/drive train/gear box/etc... run around 25% faster to maintain the same speed. But if the car was suppose to have a top speed of 260mph, even that wouldn't be impossible to overcome.

We thought that was going to be an issue too, but the car can crack 160 in third. Some additional drive train reduction due to losing the tires wouldn't have kept it from hitting 160.

Really, the most amazing thing is that the wheels of the car were perfectly spaced apart so as to fit directly onto the rails, what are the odds of that?

"This is real physics."
"Don't you mean rail physics?"
"No."

I love the dry humour.

Finally, the show got stunts! Good blooper rail material.

Anakinnnn:

Lord Hosk:
My first question would be the width of the wheels. North American(and most of the world) Train tracks are spaced 4 ft 8 1⁄2 in, 56 inches The Cobra had a width of 68 inches so unless the wheels were running two feet into the car it would run down the outside of the tracks, or with one wheel on the tracks and one off.

We gave them credit on that. Of course train tracks are not equal to almost any vehicle wheel spacing... but we just figured most everyone knew that. You also can't stand up in a car going 160mph and can't violently turn at that speed either. What we find interesting in scenes is getting down to the stuff that really is calculable... and not the stuff that we consider common knowledge. If we were a more mainstream show, we might have to dumb it down I guess and actually spell out all the problems with a scene... but, hey.... THIS IS THE ESCAPIST COMMUNITY!! ;)

Jason Dean
REEL PHYSICS

I wasnt saying "bad reel physics people you missed something crucial!" I was just suggesting that since you covered other "ok lets just say this is possible" like the tires blowing out perfectly and the insane turn, that you might have missed the wheel base thing which is not insignificant, although clearly less significant than the turn.

i'm ignoring the entry to the track, because if you slam a wall at that speed you're probably dead, so it would be a pointless discussion

the main practical problem i see here is the tyres and wheels, if you burst the tires it probably has a better chance of making it, because it slots onto the rails, but then you'd be red lining the car to apply enough speed to accelerate
all things considered, it could probably still make 160m/h

which leads me to..

the traction calculation, did you use static friction or kenetic friction? because that's a suspiciously high amount of traction imo, i've seen plenty of trains and even at low speeds they seem to slip a little
my understanding of this is that the surface chemical bonding under ambient ( or material ) temperature is the correct way to calculate the friction coefficient here, and your .6 might be rather high when in motion ( obviously it's correct for static friction ) but how do we calculate the thermal model with kenetic friction?
compared with train wheels, i'm not sure a car's rims can hold the heat required to get sticky enough to move
and i know train wheels are a, aligned properly b, VERY hot. 100-300*c on average, 600*c.. no, really! in extreme cases.
surprising temperature source:
http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1054&context=mechengfacpub
thoughts?

other than that, if you can get close to the train drafting behind it would be easy,
cyclists have managed this.

Lord Hosk:

Anakinnnn:

Lord Hosk:
My first question would be the width of the wheels. North American(and most of the world) Train tracks are spaced 4 ft 8 1⁄2 in, 56 inches The Cobra had a width of 68 inches so unless the wheels were running two feet into the car it would run down the outside of the tracks, or with one wheel on the tracks and one off.

We gave them credit on that. Of course train tracks are not equal to almost any vehicle wheel spacing... but we just figured most everyone knew that. You also can't stand up in a car going 160mph and can't violently turn at that speed either. What we find interesting in scenes is getting down to the stuff that really is calculable... and not the stuff that we consider common knowledge. If we were a more mainstream show, we might have to dumb it down I guess and actually spell out all the problems with a scene... but, hey.... THIS IS THE ESCAPIST COMMUNITY!! ;)

Jason Dean
REEL PHYSICS

I wasnt saying "bad reel physics people you missed something crucial!" I was just suggesting that since you covered other "ok lets just say this is possible" like the tires blowing out perfectly and the insane turn, that you might have missed the wheel base thing which is not insignificant, although clearly less significant than the turn.

Are you sure about width being 68"? The important measurement you would be looking at is the wheel track, that gives the distance between the wheels on an axle from the hub. For The Cobra Concept the listed wheel track is 60.6" for the front and 60.4" for the rear. These measurements are from hub to hub so there will be rim to both sides of that measurement. The wheel size listed for the Cobra Concept are 10x18 for the front and 13x19 for the rear. From looking at the images available of the car you can see that the wheels are not centered under the vehicle, but mostly tucked under neither it.
image
With the 9.5" width rims used with the front tires you could have the front-wheels centered on the hub, from images of the rims you can see they are actually mounted with a bias toward the cars center-line. Even with a centered rim the front wheels will have a distance between them of 60.6" - 2*(4.5") giving us 51.6" between the edge of the rims. this is well within a reasonable bound for this theoretical vehicle on the rails. The rear wheels are more then wide enough to accommodate a rim.

Using the right measurements when doing the math makes it much easier.

TLDR; yes the vehicle would be able to fit properly on rails.

Metal to Metal friction varies less then other substances for sliding friction. For instance they used .61 as there coefficient of friction so the materials they compared using are Aluminium and Mild Steel. The sliding coefficient of friction between dry aluminum and mild steel is .47. Substituting .47 for .61 when calculating the Frictional force you get 3212.22 N, or 722.13 lb of force. That is still enough frictional force to reach 160+ mph.

Coefficient of Friction table

I love videos keep making them you guys are awesome.

I have to say that this video had THE FUNNIEST set of bloopers to date! I am not really that surprised that it worked and I look forward to the next one

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