Putting coins on railroad tracks

Quote: Wizard

Also, what about all those devices that flatten pennies to make a souvenir? Aren't those in violation of that law?

I used to put coins on the RR tracks near my house when I was a kid. Should I turn myself in?

Quote: EvenBob

I used to put coins on the RR tracks near my house when I was a kid. Should I turn myself in?

Me too! However I did it well into my early thirties. Once I taped the coin to the track so it would get REALLY flat, but the tape didn't seem to have any effect. After the first wheel rolls over I think the coin is propelled backwards, and the tape is not sufficient to stop it. Maybe Doc, our resident physics expert, can explain.

Anyone hear that urban legend that putting a coin on the track could cause the train to derail?

Quote: Wizard

Me too! However I did it well into my early thirties. Once I taped the coin to the track so it would get REALLY flat, but the tape didn't seem to have any effect. After the first wheel rolls over I think the coin is propelled backwards, and the tape is not sufficient to stop it. Maybe Doc, our resident physics expert, can explain.

Anyone hear that urban legend that putting a coin on the track could cause the train to derail?

Sometimes we put 10 pennies on to see how many would remain, and none ever made it. Once some bad neighbor kids put a big chain on and it just flattened it and cut it in half. Those were the days when they shipped autos from Detroit on open cars and kids would line up on the hill and throw rocks at the new cars. Now they travel in enclosed cars.

Quote: EvenBob

Those were the days when they shipped autos from Detroit on open cars and kids would line up on the hill and throw rocks at the new cars. Now they travel in enclosed cars.

No wonder the auto makers went bankrupt.

Urban legend for sure.

Back in the days of street cars it was common for nickles to be squashed down into quarter-sized slugs since vending machines weren't so discriminating at the time. Happened a great deal, no streetcars derailed though. The different sections of track often meet with a height difference of more than a penny-width.

Quote: Wizard

Me too! However I did it well into my early thirties. Once I taped the coin to the track so it would get REALLY flat, but the tape didn't seem to have any effect. After the first wheel rolls over I think the coin is propelled backwards, and the tape is not sufficient to stop it. Maybe Doc, our resident physics expert, can explain.

Anyone hear that urban legend that putting a coin on the track could cause the train to derail?

Heard it on Mythbusters but seemed completely silly. For the record I put a quarter, dime, nickel, and penny on one track in my mid 20s killing time between sales appointments. The nickel was unharmed and merely was thrown from the track. Showed it to a guy at the office and he insisted it was a mint mistake. I told the guy what it was and he said, "No, it is a mis-strike." The guy was an idiot.

I think you would have to REALLY tape it down with duct-tape but I also think there would be a limit to how flat it would get since the pressure would not be increasing after the engine being the heaviest car. Think filling a cooler of ice with beer. The ice will get it to 32 degrees or so, but no longer how long you leave it in or how much more ice you add it is still 32 degrees at its coldest.

Quote: Wizard

.... Maybe Doc, our resident physics expert, can explain. ...

Well, Mr. Wizard, I think we're once again getting into some careless use of terms. Way back here, I had to chastise mkl654321 for sorta referring to me as an "authority" on something or other. I don't think I can let you get by with calling me a "resident physics expert" either. Someone might ask me a serious question, and I could wind up really embarrassing myself if I tried to live up to that title. I once had a month-long energy consulting job with the United Nations Development Program in Cyprus. The official position title was "Technical Expert", and I was seriously uncomfortable with that.

With regard to a cent being propelled backward after it is squashed under a wheel, I could only apply some wild speculation. Although the coin undergoes extensive permanent deformation in that process, it probably still exhibits the customary elasticity of the metal. Once it is relieved of the stress imposed by the wheel, it probably snaps back the amount it has been elastically deformed (much less than the permanent deformation), which could cause it to jump as it comes free of the pinch. At the moment of release, backward is possibly the only direction it has available to move, since the wheel and track would obstruct forward motion. Does that seem like rational speculation? That's all I think I can offer. For better answers, check with whatever rocket scientist you know best.

Quote: Doc

At the moment of release, backward is possibly the only direction it has available to move,

I've seen enough of them, they usually just fly off the track in any direction, depending on the speed of the train.

Quote: EvenBob

I've seen enough of them, they usually just fly off the track in any direction, depending on the speed of the train.

I think the nickel I once put on flipped mostly forward since the train wheel caught it like a tiddly-wink piece. The others got crushed, so I would guess coin thickness would be involved.

Quote: AZDuffman

I think the nickel I once put on flipped mostly forward since the train wheel caught it like a tiddly-wink piece. The others got crushed, so I would guess coin thickness would be involved.

I think they have a tendency to bounce, actually. If you look at it, only a very small part of the wheel is in contact with the track at any given time. Its not unlike hitting the coin with a heavy hammer, and that will make a coin bounce.

Quote: EvenBob

I think they have a tendency to bounce, actually. If you look at it, only a very small part of the wheel is in contact with the track at any given time. Its not unlike hitting the coin with a heavy hammer, and that will make a coin bounce.

I'll let someone who is better with the math tell us how much of the weel is tangent to the track, but you are right, it was kind of a bounce. But I do swear that the nickel just bounced off untouched. Quarter, dime, and penny were crushed. I didn't have a JFK Half at the time.

I was going to use a tiddly-wink comparison, but AZD beat me to it. Upon thinking about it, I think you're right that it would fly forward. My theory is that the force is so great that even duct tape couldn't hold it down. Even with tiddy-winks just your finger can make a piece fly a few feet, so imagine what a train engine could do. Does anyone following this live near some train tracks to test this out? Freight trains do come through Vegas, but not very frequently, and I live far away from the tracks.

As I recall, sometimes when I put coins on the track they would be unharmed. Maybe the vibrations caused them to fall off before the train even touched it. Or maybe it was a mis-struck super-nickel!

Quote: Wizard

As I recall, sometimes when I put coins on the track they would be unharmed. Maybe the vibrations caused them to fall off before the train even touched it. Or maybe it was a mis-struck super-nickel!

Thats exactly what happens. Tracks aren't very solid, they're meant to move somewhat. When a train is coming they vibrate like crazy. They have to be able to move up and down and to the side or the train would derail, as I'm sure they discovered early on.

Quote: Wizard

I was going to use a tiddly-wink comparison, but AZD beat me to it. Upon thinking about it, I think you're right that it would fly forward. My theory is that the force is so great that even duct tape couldn't hold it down. Even with tiddy-winks just your finger can make a piece fly a few feet, so imagine what a train engine could do. Does anyone following this live near some train tracks to test this out? Freight trains do come through Vegas, but not very frequently, and I live far away from the tracks.

As I recall, sometimes when I put coins on the track they would be unharmed. Maybe the vibrations caused them to fall off before the train even touched it. Or maybe it was a mis-struck super-nickel!

Too cold and dark to go down to the river and wait by the tracks this time of year, but if there is interest in spring I will go try it and even take pictures to doccument it. As long as anybody is interested remind me.

On another part, Wiz, is there a formula to know how much of the wheel is tangent to the track? Forgetting any "flex" the track might have as it would be minimal. Just the amount of any circle of a given diameter?

Quote: AZDuffman

Too cold and dark to go down to the river and wait by the tracks this time of year, but if there is interest in spring I will go try it and even take pictures to doccument it. As long as anybody is interested remind me.

On another part, Wiz, is there a formula to know how much of the wheel is tangent to the track? Forgetting any "flex" the track might have as it would be minimal. Just the amount of any circle of a given diameter?

Let's remember that in the spring.

I don't know about how much of the wheel touches the track. Although I'm sure the wheel is made out of very strong steel, it is also under a lot of weight, so must flatten a little. If forced to a guess, I'd say about a centimeter. Maybe our resident physics expert science guy, Doc, will know.

Quote: Wizard

Let's remember that in the spring.

I don't know about how much of the wheel touches the track. Although I'm sure the wheel is made out of very strong steel, it is also under a lot of weight, so must flatten a little. If forced to a guess, I'd say about a centimeter. Maybe our resident physics expert science guy, Doc, will know.

I like to know how much flex a track has. When you see a train going over tracks on a high speed camera, they move around a lot.

Quote: EvenBob

Quote: AZDuffman

I think the nickel I once put on flipped mostly forward since the train wheel caught it like a tiddly-wink piece. The others got crushed, so I would guess coin thickness would be involved.

I think they have a tendency to bounce, actually. If you look at it, only a very small part of the wheel is in contact with the track at any given time. Its not unlike hitting the coin with a heavy hammer, and that will make a coin bounce.

Yep, hitting it with a hammer to make it bounce would be an example of the elastic snap-back I was trying to describe. I particularly like AZD's and the Wizard's references to tiddly-winks -- those little plastic toy buggers tend to jump in all sorts of directions if you're not careful, and that would match up with what most of us coin-defacing miscreants have observed. You can have the tiddly-wink effect on the front side of the wheel (if the coin can escape) or on the back side after the deformation, as the coin is released -- it is a different shape/thickness there, but it is still elastically compressed as it was on the front side.

As for the wheel/track contact area, yes, it would not just be a point/line. That would imply an infinite stress level in both the wheel and the track, which they could not support. Back during the late Pleistocene epoch, when I took a course or two in mechanics of materials, perhaps I could have figured out the amount of compression in a round wheel and a flat track under a given loading. But I forgot how to do that sort of thing in the interim. I suspect some skilled undergraduate majoring in engineering mechanics could do the calculation, but likely not a senile retiree like me.

Look at a train track in cross section, and it does NOT have a flat top. The bottom is flat, but the top is rounded. So the point of contact is rather small.

Quote: EvenBob

Thats exactly what happens. Tracks aren't very solid, they're meant to move somewhat. When a train is coming they vibrate like crazy. They have to be able to move up and down and to the side or the train would derail, as I'm sure they discovered early on.

I used to live near tracks. I had that problem. The vibrations would cause the coin to fall off. To combat that, I would place coins on the common flat part of a switch/junction, so that the coin may move a little, but stayed on the track - until struck by the train.

Sometimes the coin gets multiple strikes, resulting in bent coins. I have also stacked coins resulting in flat coins that are partially fused together.

Quote: DJTeddyBear

Sometimes the coin gets multiple strikes, resulting in bent coins. I have also stacked coins resulting in flat coins that are partially fused together.

Wow, stacking coins, we never thought of that. Also, this was a long time ago and you could go to the store with a dime and get 10 pieces of penny candy. With a train flattened coin you could buy exactly nothing.

Quote: AZDuffman

I think you would have to REALLY tape it down with duct-tape

Hey, it's the modern age! Superglue it to the track.

I used to put coins on the track as well, until Winter Park, Co. One of the coins flew back. It sounded like a bullet ricocheting, and hit the building behind us.

Quote: DJTeddyBear

Look at a train track in cross section, and it does NOT have a flat top. The bottom is flat, but the top is rounded. So the point of contact is rather small. ...

You are quite correct about the top surface of the rail, except that they tend to get distorted over time. The issue of shape in this problem that is most interesting to me is the fact that the section of the wheel that rolls on the track is not cylindrical as one might expect. It is conical, and the reason for that (does everyone know?) shows that someone was pretty clever back in the day. I think this may be associated with the designed curvature of the top of the rail, but I'm not certain of that.

Quote: rxwine

Hey, it's the modern age! Superglue it to the track.

Nice idea. But if it really bonded that well, it might be hard to take your souvenir home with you. Can you just imagine the kids trying to hacksaw out a little section of track to take with them? Actually, I think I do have about a 6" piece of rail in my garage. I found it in my late father-in-law's tool room, and I hung onto it trying to figure out something neat to do with it. Heavy as all get-out.

Don't the laws of physics dictate the coin must fly backwards once the train wheel rolls over it? Sure it will probably strike something and end up moving forward, especially considering all of the objects to strike are moving forward........

The coin is at rest on the track. A train is moving forward. Therefore, there is a resistive force that is being applied to the top rail in the reverse direction. It is this resistance that allows the train to move forward, correct?
When the wheel gets to the coin, a resistive force is applied toward the rear and the train is moving forward. However, the coin is not fixed in place. It has the force of the train trying to slide the coin backward, and it has the friction of the coin against the top rail to keep it in place. I would think the train would win the battle over the friction........

Disclaimer. I received C's in physics in high school, back when slide rules were still used......................

Tape?
When I was a kid, I would just have my little brother hold the nickel on the track with his finger.

Warning: This is a long, boring, nerdy post. Anyone with a lick of sense and restrainable curiosity should definitely skip down to the next post.

Quote: Wizard

... I don't know about how much of the wheel touches the track. Although I'm sure the wheel is made out of very strong steel, it is also under a lot of weight, so must flatten a little. If forced to a guess, I'd say about a centimeter. Maybe our resident physics expert science guy, Doc, will know.

Consider this response to be evidence of two things: (1) I have far too much time on my hands to live a normal life, and (2) it really bugs me to admit that my brain can no longer solve a problem, as I admitted in my original response to this comment by the Wizard, back on page 2 of this thread.

Because of these factors, I felt compelled this morning to pull a reference book off my shelf and try to figure out just how much contact distance there typically is between the train wheel and the track. Of course, I took some short cuts due to my laziness.

DJTeddyBear pointed out that the top of the track is not flat, and I pointed out that the wheel surface is conical rather than cylindrical. But lets make the simplifying assumptions that this problem is equivalent to a round cylinder rolling on a flat surface. For that situation, my reference book provided enough info to lead to the following equation:


where:
b = width of the contact area (estimated by the Wizard as 1 cm.)
P = load on the contact area
r = radius of the wheel
E = modulus of elasticity of the steel (assumed the same for wheel and rail)
l = length of the contact area across the rail

I assumed that the coin would be struck by the locomotive (as the lead car) and looked at some electric and diesel locomotive engine info (weights and number of wheels). I think that something around 33,000 lb is a reasonable figure for the load at each wheel.

I found that freight and passenger cars typically have 33-in or 36-inch diameter wheels, but didn’t find that info on locomotive wheels. I’ll assume r = 16.5 inches.

For most steels, E is in the range of 30 million lb per square inch.

There are several standard sizes of rail with the head widths varying from 2.56 to 3 inches. Discounting for the curved edges, I estimate l = 2 inches.

Using these estimates and the formula above, I calculate that b = 0.145 inches or about 0.37 cm. A little more than 1/3 the distance the Wizard came up with much more quickly than I came up with this calculated answer. In a rational world of internet gambling forums, his method is better justified than mine.

Now that I have once again proved what a nerd I am, I think it is time to address in a little more detail the Wizard’s references to me as “resident physics expert” and “science guy.” I’m not sure just where this started, but it may have been back on that thread about the Mike O’Callaghan-Pat Tillman Memorial Bridge, where we got side-tracked talking about how much load the water in a lake places on a dam. I stated that “it is a simple physics problem” and caught a bit of skeptical flack about my answer. The objections did not subside until the Wizard’s dad (the actual PhD physicist) gave me a vote of support; then the pitchforks were put away, and the torches were doused.

Yes, I did study a little physics along the way, in addition to a number of other areas. Once, I actually moonlighted for a few months teaching an evening course in physics at a Vo-Tech school. Other than that period, I’m not sure any of my employers ever really cared that I had studied some physics. It would not surprise me a bit to hear that some other member(s) on this forum studied physics to a greater extent than I have. I never took a single graduate-level course in physics. So there.

Quote: RaleighCraps

Disclaimer. I received C's in physics in high school, back when slide rules were still used.

I still have a slide rule in my desk drawer. Didn't use it on this problem, though.

Quote: EvenBob

Quote: Wizard

Let's remember that in the spring.

I don't know about how much of the wheel touches the track. Although I'm sure the wheel is made out of very strong steel, it is also under a lot of weight, so must flatten a little. If forced to a guess, I'd say about a centimeter. Maybe our resident physics expert science guy, Doc, will know.

I like to know how much flex a track has. When you see a train going over tracks on a high speed camera, they move around a lot.

To make it more complicated, most of that "flex" is the tie and all moving up and down in the rail-bed. The steel track moves much less.

Like I said, I'll maybe try a lot of this in spring. But from last time I did it there was little problem with the coins flying out, except for the nickel.

Doc, maybe I am wrong, but from my point of view, this is a matter of strenght of materials, and in this case, deformation due normal force.
That would actually result in the use of G instead of E, that is E/(1+V), with V = Poisson constant, and somehow wouldn`t the inertia of the coin affect the numerical results?

Yes, aluisio, this is an issue of strength of materials. Back when I took such courses, they were called something like "Mechanics of Deformable Bodies", or "Def Bods" for short. I think that Poisson's constant and Pi and D/r=2 and maybe a few other constants are hidden in that 1.52 factor in the formula. For the analysis in my last post, I just considered the (cylindrical) wheel and the (flat plate) rail, ignoring the coin. My off-the-wall guess is that both the inertia and the compressive strength of the metals used in our coinage would have negligible effect on the steel wheel and rail -- it's the coin that gets flattened rather than leaving an indentation on the wheel. (Occasionally when using a penny, you can see a small amount of copper fused into the rail afterward.)

A page back, I suggested that "some skilled undergraduate majoring in engineering mechanics could do the calculation...." I have no idea about your background, but perhaps you come a lot closer to that description than I do. Feel free to jump in on any of these absurdly nerdy conversations.

Quote: RaleighCraps

Don't the laws of physics dictate the coin must fly backwards once the train wheel rolls over it?

Exactly. But only if the train does succeed in rolling OVER the coin.

Often, the train hits the coin, and, much like tidly winks, the coin goes flying.

Other times, at the point where you'd think the coin should fly backwards, it has been flattened to the point where the train is in contact with the coin, as well as the rail alongside it. That would kill a lot of the potential sliding due to backwards resistive force.

I always suspected that the air being pushed in front of the wheel would start the coin moving off the track. The faster the train, the less likely the coin would remain on the track.

I have also heard that it was possible to prevent a train from starting by wedging a small stone next to a wheel to prevent it from rolling. Amazing that tons and tons of train can be held back by something so small, but in a critical place.

Quote: Ayecarumba

I always suspected that the air being pushed in front of the wheel would start the coin moving off the track. The faster the train, the less likely the coin would remain on the track.

I have also heard that it was possible to prevent a train from starting by wedging a small stone next to a wheel to prevent it from rolling. Amazing that tons and tons of train can be held back by something so small, but in a critical place.

Hello MythBusters

I asked my dad about this. Here is what he said:

Quote: Wizard's dad

I do not to claim to have the definitive answer, but I have had my windshield broken by rocks ejected backwards by trucks I was following at what I thought was a safe distance. Once free of the tire, it is as if the rock was shot from a gun. (Part of the relative speed of inpact was due to my own speed, however). It may have something to do with a higher friction coefficient between tire and rock than between rock and road, so the rock is free to fly backwards while still being held by the tire.

That is one reason why large trucks have large "mud flaps" behind the rear wheels. They protect cars behind from flying rocks.

The same argument might not apply in a steel/copper/steel railroad track "sandwich" situation.

With duct tape, it would depend upon how much tape is applied. If you put enough on, the penny should stay in place.

Guess I'm in a video posting mood lately.

http://www.youtube.com/watch?v=yOMwAnwp9JQ

Kids still do this of course -- this one even includes a slow motion replay.

(heh, it's where I found the superglue comment)

Quote: Wizard's dad

I do not to claim to have the definitive answer, but I have had my windshield broken by rocks ejected backwards by trucks I was following at what I thought was a safe distance. Once free of the tire, it is as if the rock was shot from a gun. (Part of the relative speed of inpact was due to my own speed, however). It may have something to do with a higher friction coefficient between tire and rock than between rock and road, so the rock is free to fly backwards while still being held by the tire.

That is one reason why large trucks have large "mud flaps" behind the rear wheels. They protect cars behind from flying rocks.

The same argument might not apply in a steel/copper/steel railroad track "sandwich" situation.

With duct tape, it would depend upon how much tape is applied. If you put enough on, the penny should stay in place.

A few thoughts on this:
-- The tread pattern on most truck tires has bigger channels which make picking up larger pieces of gravel easier. It seems to me that the windshield busters are launched from the tire when the centripetal force of the wedged tread is exceeded by the centrifugal force from being on the surface of a spinning tire.

-- Very large things can be caught between the "dually" wheels of semi's and trailers. Mudflaps do indeed save lives.

Quote: Ayecarumba

... It seems to me that the windshield busters are launched from the tire when the centripetal force of the wedged tread is exceeded by the centrifugal force from being on the surface of a spinning tire.

You might consider that the motion of a rock stuck in a tire tread of a moving vehicle is quite different from what it would be in a spinning tire with a stationary axle (tire not touching the ground). As the vehicle goes down the road, the rock moves along a cycloid path, coming to a complete stop when that point of the tire is touching the road and traveling in the vehicular direction at twice the vehicle's speed when it is on the top side of the tire. The stuck rock is never moving toward the rear.

I think that rocks are frequently released from the tread shortly after that spot on the tire lifts from the road, probably due to the flexing of the tread as it touches the pavement and then rises again. If the rock comes free on its upward path on the cycloid, the horizontal component of its velocity is still in the same direction as the vehicle -- the rock tends to be thrown upward and forward, not back at the trailing vehicle. (You can see this if you are standing on the side of the road, watching the truck go by slinging rocks forward from its treads.) The windshield of the trailing vehicle tends to be hit because that vehicle is traveling forward faster than the rock. It's not really a matter of the rock flying back and hitting the windshield but that the trailing windshield catches up with and hits the rock!

Wizard, perhaps you should check with your dad to see whether I am thinking correctly on this one. It's getting late here in the east, and my brain may already be asleep. :-)

Note: if the tire is on a drive wheel and the hot-rod driver is peeling out spinning his wheels, then in that case it actually is possible to toss a rock to the rear.

Quote: Wizard

I asked my dad about this. Here is what he said:

Mikes dad must be going "What site is my son running now", never a gambling question.

Quote: Doc

Note: if the tire is on a drive wheel and the hot-rod driver is peeling out spinning his wheels, then in that case it actually is possible to toss a rock to the rear.

Thanks Doc. This does match my experience, where the two times I have been struck, the causes were nutjobs driving on the shoulder and center divider of the highway to pass stopped traffic. They end up kicking up all kinds of stuff as their tires spin through the loose accumulations on the sides of the road.

I am AMAZED that a topic such as this gets gets as high a number of replies, esp. on a forum such as this. I myself can't see the fascination over what happens to coins that trains run over or what they may or may not do to a train. How about if you stick your leg out and let a train run over it? Does it cut it in half, does it disintegrate it, or maybe it flattens and fuses it in such a way that you can pull the whole thing out afterwards so you can show it off at the church bazaar.

I make no apologies for my interest in putting coins on railroad track, or my interest in why others find it interesting. I've never thought about it before, but I think inquisitive minds like to experiment, in particular in methods of destroying things.

Funny you should ask about putting a leg on a RR track. I just finished watching the movie 'Sin Nombre' where a guy fell off the top of a train, his leg fell on the track, and the train cut it right in two.

Quote: Wizard

where a guy fell off the top of a train, his leg fell on the track, and the train cut it right in two.

Between 1890 and 1920, the RR's is the US were the biggest employer and of average of 10 men a day were killed on the job and dozens permanently injured. Every day. Those were the days when every car had a brakeman riding on top, no matter what the weather. Many of them would fall asleep and get crushed between the cars. It wasn't until 1910 that air brakes, invented by Westinghouse, were on all trains.

I apologize for going off-topic...

If you have an interest in railroads or model railroads, an amazing place to visit is the Model Railroad Museum in San Diego. It's inside Balboa Park. We went last year and, to me, it was fascinating. The enthusiasm and dedication of the volunteers that work on the exhibits is incredible. Great thing to see if you get a chance.

address for the museum -

And back to topic...

Quote: JerryLogan

I am AMAZED that a topic such as this gets gets as high a number of replies, esp. on a forum such as this. I myself can't see the fascination over what happens to coins that trains run over or what they may or may not do to a train. How about if you stick your leg out and let a train run over it? Does it cut it in half, does it disintegrate it, or maybe it flattens and fuses it in such a way that you can pull the whole thing out afterwards so you can show it off at the church bazaar.

Putting coins on a track is fun and exciting, you should try it sometime.

Quote: EvenBob

Putting coins on a track is fun and exciting, you should try it sometime.

Maybe....but I haven't even SEEN a train for 20 years.

Well, I did it. I was near some tracks on Sunday and I put a stack of 4 pennies on one track and a stack of 4 nickels on the other. I went back today and found them. The pennies were scattered, but nickels were fused together in one solid flat piece. I never would have invested 24 cents when I was a kid, you could buy enough candy to fill a small bag for that princely sum in 1960..

And I'm a bit offended because I actually have a degree in Physics (and Astronomy)... not as good as a 1xx IQ I know but I busted my ass pretty hard in University to get it. Mind you, that was 19 years ago and I remember little tidbits of calculus, statistics, quantum mechanics, relativity, cloud physics, electromagnetism and so on and so forth.

The track itself is not level. It is slightly higher in the middle and rounded on the edges. Whether the track is made this way or if it it from wear I am not sure. The coin would be thrown backwards because of the rotation of the wheel applies a force to the coin. Since the train is so massive and the coin so light and the friction between the coin and steel is negligible, the coin is thrown back at the same speed of the wheels going over it. Because the top of the track is not precisely flat, any imperfection of the placement of the coin or the wheel going over it will also cause to coin to fly off axis, which is why it ends up off the tracks fairly quickly.

I don't think duct tape would help, but I could be wrong. I think with all of the heat and friction, there is no way that duct tape would stand such a beating. Your best chance might be some adhesive such as Crazy Glue, but I don't even think that would do the trick. If the coin was able to be kept in place, i think. The coin would end up elongated and flatter.

Actually, if you google images "Flattened coin on on a train", you will see plenty of flattened coins.

Quote: boymimbo

Actually, if you google images "Flattened coin on on a train", you will see plenty of flattened coins.

LOL, you're right, very cool pics. Trains coins tracks, its never boring.

BoyMimbo -

I think you're responding to a bad assumption on your part.

Nobody is claiming the coins stayed on the tracks for the entire length of the train.

Usually, the first wheel that hit it will send it to the side. Sometimes it gets flattened or at least bent first. Certainly, if it remains on the track after being squished, the second wheel sends it off track.

It's just that, occasionally a stack will be arranged and hit in such a manner that it gets run over by that first wheel, and fused, before sailing off the track.

---

Note that when I did this, I'd put the coins on the flat part of a switch junction. This served two purposes:

1 - Being flat, it reduced the likelihood that the coins fall off the curved track due to vibration of the approaching train.

2 - It made it simple to remember where they were so I could look for them. I've lost too many in the gravel prior to learning that trick.

Here's something I had no conception of. A group of thieves somewhere cut out a section of track to sell the steel. A track section weighs 700 pounds. When they cut the track, it snapped like a stretched rubber band!

'De Angelis noted that a piece of rail, more than 100 feet away, had buckled and torn away from its moorings because of the intense pressure released when the thieves cut through the steel. “When they cut through they must have got the shock of their lives,” he said.'

Apparently, the weight of the trains over a long period stretches the steel (or maybe it contracts) like a rubber band so its always under pressure. I'm sure it was very exciting when they cut thru, the morons. A train was derailed as a result, BTW.

Okay, I hope you guys are happy. Here is a video of my experiment to answer the question at hand.



I welcome all comments.

Quote: Wizard

I welcome all comments.

1) nearly three years after the last comment. I admire that level of dedication.

2) the train does a nice rendition of the Doppler effect

3) I think it's settled, the coins are not flung far away and they do get flattened like bottle caps (remember them?) on the street.