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Stringatron string accelerator
Particle accelerators are designed to accelerate, well, particles. But if string theory's right, and elementary particles really are just tiny vibrating strings, then why not just accelerate strings in the first place?
About this creation
Please feel free to look over the images and skip the verbiage.

Like many a young boy growing up during the Cold War, I dreamed of owning my very own atom smasher. And some 6 decades later, the dream came true with this top quark accelerator...



Then it hit me: If string theory's right, and elementary particles really are just tiny vibrating strings in disguise, then why bother with particle accelerators like the Large Hadron Collider?

Why not just accelerate strings in the first place??

Allow me to introduce the "Stringatron" -- the world's first high-energy LEGOŽ accelerator just for strings...



Here's a preview of my upcoming press conference...

So far, ladies and gentlemen, the Stringatron has produced no compelling evidence either for or against string theory. Contrary to widespread belief, however, it's proven conclusively that you really can push string!

Some versions of string theory envision the strings as closed "loops" while others allow open-ended "strands" in some settings.



That's why I designed the Stringatron to accelerate both kinds. Here, it's loaded with a yellow twine loop while 9 different twine and paracord strands wait to smash unsuspecting atoms.

Accelerating a loop...



So far, the Stringatron's been tested with 2 different kinds of string -- thin yellow "twine" (1.5 mm OD, probably polypropylene) and thicker white "paracord" (3.0 mm OD) looking more like polyethylene than nylon. The 3L black axle pin has a 4.8 mm OD for comparison.



The paracord has twice the diameter but over 5 times the linear mass density (4.3e-3 vs. 8.0e-4 kg/m).

The twine and paracord both work well for strands. But until I find a way to make seamless paracord loops without knots or other big lumps, the loops will just have to be twine.



That's because twine knots can pass through the string transport mechanism without mishap, but paracord knots are way too big.



Twine loop knot emerging from the pinch roller gap.

Credit: The Stringatron was inspired by a non-LEGOŽ string shooter posted by YouTube science teacher Bruce Yeany in 2014. I just adapted it to LEGOŽ for use in low-budget high-energy physics experiments.

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Stringatron with twine loop

The Stringatron with a twine loop ready to go...



Unlike LEGOŽ battery boxes, the old train transformer on the left (2968b) delivers a full 9 volts with no voltage sag -- no matter how long the Stringatron's been running.

Loops enter the string transport mechanism at the outer loop guide below the lower black rubber pinch roller and exit from between the pinch rollers. The outbound and return limbs of the loop travel in roughly opposite directions.



With no string loaded, there's a 0.7 mm gap between pinch rollers to minimize friction.



Wide, flat pinch rollers with very shallow treads make the accelerator more tolerant of deviations in the string's path through the transport mechanism. Only the lower pinch roller is driven.



A loop coming in from the right and exiting almost vertically...



Removing the loop guide carrier reveals the hidden portion of the loop path as seen from below.



The passive upper pinch roller is spring-loaded to maintain a good grip on both twine and paracord while allowing twine knots to pass through uneventfully.



A single black "R-motor" (RC Race Buggy, 5292) drives the lower pinch roller directly from its high-speed power take-off.



This motor's unique combination of high speed, medium torque, and very high mechanical power output delivers high string exit speeds with no external gearing.



A timing disk for a laser tachometer rides on the motor end of the lower pinch roller axle.

With a twine loop loaded and the transformer at full power, the lower pinch roller turns at 1,695 RPM. Given the pinch roller OD of 37 mm, that comes out to a twine exit speed of ~6.6 m/s! That's a whopping 24 kph or 0.0000022% the speed of light!

The mostly LBG accelerator core swings up and down within a mostly yellow gimbal to adjust the string launch angle.





The actual launch angle is 15° higher than the angle the accelerator core makes with the horizontal.



The Stringatron's latest addition -- a new way to dial in launch angles between ~0° and ~85°. The range can easily be shifted up or down as needed by moving the linear actuator attachments.





The firing switch (orange lever) is just for convenience. The accelerator spins up just as quickly with a sharp full turn of the transformer dial.



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Stringatron with paracord strand

The first video starts with a series of strand launches with ranges of up to 1.0 m at 35°.

The white paracord strand between the pinch rollers here is ready to go. The off-line yellow twine loop remains in its guides but no longer runs through the pinch rollers.



Strands enter the accelerator core at this yellow strand guide and exit from the pinch rollers in roughly the same direction.



Sighting down the empty strand guide to the pinch roller gap...



Like the loop feed, the strand feed is quite robust. As long as a strand has no knots, it can lay on the table behind the Stringatron any old way and still feed properly. Laying strands out straight does nothing to improve range.

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Stupid Stringatron tricks with loops

Pummeling unsuspecting atoms and subatomic particles with strands shot from a Stringatron is loads of fun, but things get really interesting when a loop is running...



Assume a Stringatron running a twine loop at full power and ignore the small waves excited in the loop by the knot bumping through the pinch rollers. The loop's undisturbed shape and orientation then depends only on launch angle θ. We'll call this the loop's "equilibrium state".

Here and at 1:20 above, we see the equilibrium state for θ ≈ 35°.

[equilibrium loop]

An equilibrium loop has 3 distinct sections lying in a vertical plane perpendicular to the lower pinch roller axle:
  • An upper "outbound limb" with a convex-upward trajectory that only roughly resembles a parabola. (Remember, we aren't dealing with a textbook cannonball in a vacuum here, as forces other than gravity act on each small piece of this limb.)
  • A lower "return limb" sliding back toward the Stringatron along the table top.
  • A relatively short, sharply curved "turnaround" in between.
At 1:52, we see that increasing θ raises the apex of the outbound limb while shortening the return limb. The lateral (side-to-side) loop distortions in this video segment are due solely to an intermittent breeze.

From 3:15 on, launch angle is fixed at θ ≈ 35°. At 3:23, we see how quickly the loop snaps back to equilibrium after even large perturbations of its return limb and turnaround.

The wand I use to mess with the loop has its own roller.



At 4:09, the wand pulls the loop out to full length by its turnaround. In the process, the return limb straighens out and comes off the table while the outbound limb drops below it. Meanwhile, the breeze comes and goes.

At 5:20, the outbound limb's great sensitivity to even the smallest disturbances becomes apparent. As seen at 7:11, however, the adjacent turnaround is very forgiving.

At 7:20, I poke the outbound limb a little too hard and end up jamming the Stringatron -- something very hard to do any other way.

Turns out that you can use the wand to push or pull the loop into many "metastable states" that retain their shapes and orientations as long as the wand stays put. Release the loop, however, and it snaps right back to the equilibrium state dictated by launch angle.

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Large Hadron Rap

A look at the Stringatron's competition -- Large Hadron Collider (LHC) at CERN. Yo, check it out...



Science journalist Kate McAlpine recorded this catchy little rap just before the LHC went live in 2008. An eventful four years later, researchers there confirmed the existence of the elusive Higgs boson.

And to think I used to hate hip hop!

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Optional: Design notes

The best thing about the R-motor here is its ability to run the lower pinch roller at ~1,700 RPM with enough torque left over to jerk the string quickly up to speed and keep it there despite mechanical losses.

The good news: These losses must be pretty small at full power, because the R-motor looses only 65 RPM in going from its measured no-load shaft speed (1,760 RPM) to its measured operating speed while running a loop (1,695 RPM).

Some of the power losses come from (i) sliding friction in the string guides and along the table top supporting the loop's return limb, and (ii) from rolling resistance between the pinch rollers. There are probably (iii) elastic losses in the string, and (iv) aerodynamic losses inside and outside the accelerator as well.

I thought about driving the lower pinch roller with an original Technic 9V motor (2838) geared down 1.67:1 or with an XL motor geared up 1:8.33. But available motor data (e.g., here) convinced me that the torque delivered to the lower pinch roller would suffer a lot, and string exit speeds along with it.



The R-motor also makes for a rather compact Stringatron. As you can imagine from the 2838 driving this electric top starter, accommodating a 2838 and its gear train would make the Stringatron much wider. An XL motor would be even worse.

The string guides have to usher string to the pinch roller gap while minimizing both friction and the chance of misfeed. The front guide is for loops, and the rear for strands. All 3 guide portals (2 for loops, 1 for strands) have small rollers on 2 sides.



Strand loading was too fiddly with early rear guides, but with this one, it's a snap.

The inner and outer portals of the loop guide have to contend with knots. They also have to allow an installed loop to be taken off line for strand acceleration without the bother of removing the loop from the accelerator core.





This removable carrier for the inner and outer loop guide portals reduces the fuss associated with installing and removing intact loops.

The strand and loop guides took some trial and error, but misfeeds are quite rare now -- even with twine loops and their pesky knots. As you can see in the first video at 4:50, the loop feed tolerates a 90° deflection of the return limb by a passing breeze without complaint.

In the background here is the 30.4x20 wheel (56145) with 37x22 ZR tire (55978) used for both pinch rollers.



In the foreground is a tool for pulling string through the pinch roller gap from the loop path. Strands don't need a loading tool.

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Specifications
Format for string-related fields: 1.5 mm twine / 3.0 mm paracord

Overall dimensions:118x168x136 mm (LxWxH)
Mass:286 g excluding transformer
Electrical power supply:9V train transformer (2968b)
Motor:RC Race Buggy (5292), high-speed power take-off
Acclerator no-load speed:1,740 RPM (182 rad/sec)
Pinch roller OD:37 mm
Available launch angles:-20 to +105°
Suitable string configurations:Both loops and strands
String types:Twine / paracord
String diameters:1.5 / 3.0 mm
String densities:8.0e-4 / 4.3e-3 kg/m
Twine strand lengths:1.72 and 2.64 m
Best twine strand range:~1.0 m (L=2.64 m at ~35°)
Paracord strand lengths:0.32-1.29 m
Best paracord strand range:~0.95 m (L=1.13 m at ~35°)
Twine loop length:1.54 m
Twine loop operating speed:1,695 RPM (177 rad/sec)
Twine loop exit speed:6.6 m/s (~24 kph)
Modified LEGOŽ parts:None
Non-LEGOŽ parts:Strings only
Credits:Original MOC inspired by Bruce Yeany's non-LEGOŽ string shooter
See also:Top quark accelerator, Scientific MOC folder

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Comments

 I made it 
  August 15, 2017
Quoting Gabor Pauler String manufacturers could pay you a dividend extending the string market to recreational strings...
Could and should! Great idea, Gabor! I'll have my agent call the string manufacturers in the morning.
 I like it 
  August 15, 2017
String manufacturers could pay you a dividend extending the string market to recreational strings...
 I made it 
  August 14, 2017
Quoting Nirds forprez Oh the versatility of Lego. When it comes to this.... you have certainly found Lego's sweet spot. Applying Lego to String Theory? Lego really is boundless in your hands.....
Thanks, Nirds! I felt sorry for the string theorists. They toil away, fighting the nastiest math imaginable at every step, but never seem to get any validation from particle accelerator results. So far, none from string accelerator results, either.
 I like it 
  August 14, 2017
Oh the versatility of Lego. When it comes to this.... you have certainly found Lego's sweet spot. Applying Lego to String Theory? Lego really is boundless in your hands.....
 I made it 
  August 14, 2017
Quoting Nils O. Wow, it looks so cool and like so much fun! Have you tried melting the ends of the ropes together with a flame or a soldering iron? The result should be a rather smooth connection. Just be careful not to burn your fingertips! Great job! :-))
Many thanks, Nils! My initial attempts at melting with a flame failed to produce a strong bond, but I'll try again. The soldering iron is a great idea!
 I like it 
  August 14, 2017
Wow, it looks so cool and like so much fun! Have you tried melting the ends of the ropes together with a flame or a soldering iron? The result should be a rather smooth connection. Just be careful not to burn your fingertips! Great job! :-))
 I made it 
  August 13, 2017
Quoting Henrik Jensen Very nice and entertaining string accelerator, now you just have to combine it with one of your tops. It could be great fun to see a top dancing on the string just like in the classic diabolo game.
Thank you, Henrik! A diabolo played well is truly a wonder. A LEGO top balancing on a string? Guessing you mean by straddling the string rather than standing on it, but wonderful idea either way! I can see a possible standing solution now. It could even pan out.
 I made it 
  August 13, 2017
Quoting Oliver Becker This should go as "Cowboys and Physics" referring to a movie- title, my friend! For my little german mind Colorado has s.th. to do with those men... I'm fascinated about what you've created here, Jeremy! As I told in my latest comment... B.t.w.: do you've checked how clean pollished the desk is after your shooting? Your wife will confer a decoration on you for that! ;)
Too kind, Oliver! Great name for the movie of my life! Can I use it? Colorado definitely has its cowboy heritage, and of course that's rubbed off on me. Yeeeee ha! I'll have to point my polishing job out to the CXO right away. Honestly, the best I could hope for at this point would be a reprieve from one of my 3 consecutive life sentences in the dog house. But, hey, it's a start.
 I made it 
  August 13, 2017
Quoting Sven ;o) Hey my man, you're crazy XD In a good way. It's again a absolutely fantastic creation and watching how it's working was a joy. Great description as always from you. Btw, don't wonder about lack of activity on my side, but I'm very busy and take short a break from building. Have a great day my friend and keep up your fantastic work! Greets to you and your family from us in Germany :)
Crazy in a good way, eh? Well, I've been called worse. What the videos don't show is how much =more= fun it is to mess with running loops yourself. No camera -- just your own hands and ears and eyes. They seem to have lives of their own, varying with launch angle. Perhaps I'll try to bring that out in a future video. My best to you and yours, my friend. May you find some building time soon.
 I made it 
  August 13, 2017
Quoting Walter Lee Awesome *cowboy rope* tricks with Lego Technics - there's some crazy physics behind this of am sure of it... :-)
Thanks, Walter! Still scratching my head over many aspects of full-power loop behavior -- especially when I mess with the outbound limb. I like your lariat analogy. In normal operation, the loop and lariat both take on stable shapes and orientations, though not the same ones. Are these stable states maintained the same way? Guessing so, but only in part. Need to think it through. Are they equally stable? No data.
 I like it 
  August 13, 2017
Very nice and entertaining string accelerator, now you just have to combine it with one of your tops. It could be great fun to see a top dancing on the string just like in the classic diabolo game.
 I like it 
  August 13, 2017
This should go as "Cowboys and Physics" referring to a movie- title, my friend! For my little german mind Colorado has s.th. to do with those men... I'm fascinated about what you've created here, Jeremy! As I told in my latest comment... B.t.w.: do you've checked how clean pollished the desk is after your shooting? Your wife will confer a decoration on you for that! ;)
 I like it 
  August 13, 2017
Hey my man, you're crazy XD In a good way. It's again a absolutely fantastic creation and watching how it's working was a joy. Great description as always from you. Btw, don't wonder about lack of activity on my side, but I'm very busy and take short a break from building. Have a great day my friend and keep up your fantastic work! Greets to you and your family from us in Germany :)
  August 13, 2017
Awesome *cowboy rope* tricks with Lego Technics - there's some crazy physics behind this of am sure of it... :-)
 I made it 
  August 13, 2017
Quoting Builder Allan Haha nice! A fun little build. I like both the videos :-)
Thanks, Allan! Definitely fun to play with, but also a device with the potential to unlock the deepest secrets of the subatomic world! ;^}
 I like it 
  August 12, 2017
Haha nice! A fun little build. I like both the videos :-)
 I made it 
  August 12, 2017
Quoting Doug Hughes Haha! This is awesome! The video is fantastic :)
Very kind, Doug! Guessing you're talking about the 2nd video?
 I like it 
  August 12, 2017
Haha! This is awesome! The video is fantastic :)
 
By Jeremy McCreary
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LEGO models my own creation MOCpages toys shop Stringatron string accelerator


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