Going Round and Round

When I was young, riding the Carousel was a magical experience.  I can recall holding onto my horse's pole for dear life, intoxicated by the bright lights, the shrill calliope music and the world spinning past at dizzying speed. I always chose my steed with care, knowing that only the perfect companion could get me to the far-off destination pictured in my imagination. These rides were an integral part of childhood summer adventures that included other joys like cotton candy, beach-side arcades and boardwalks.  

Now that I am older and own a Carousel, I have come to appreciate it for what it really is, a wonderful machine of subtle complexity designed by some long-gone inventor for the specific task of bringing joy to the hearts of children of all ages.  Somehow, knowing how it works makes it even more magical for me years later.

Carousels, like so many other engineering marvels, work because engineers have overcome the problem of moving around something much too heavy in a clever way so that the machine’s own weight and speed assist. The carousel must spin, or it's not much fun.  In order to make the spinning efficient, and to allow the horses freedom to move up and down, the whole works actually floats, suspended unhindered on a single bearing from a central pole. The pole is a rather remarkable tube of structural steel. The Wackenhammer’s carousel has a center pole about 8 inches in diameter, which is strong enough to support our 30 horses, riders, and the rest of the platform, canopy and sweeps, 8-10 tons in all.

We owe the modern carousel ride to an English engineer named Frederick Savage. He invented both the steam-powered carousel (the first engine-driven carousel) and the system of overhead gears and cranks that allow the suspended horses to move up and down as the carousel turns and simulate an actual ride on horseback. The first trick is to get a motor (an electric motor these days) which spins at a very fast rate (about 1740 rpm), to spin the ride at a more sedate speed (so that children aren’t flung off into the bushes), more like 5.5 rpm.  We must also get the motor, which turns a shaft that comes out the side, to turn the main carousel drive shaft, which is upright. This is accomplished through a multi-step set of belts and gears and gear ratios to change rotations per minute (rpm) and orientation.  

First, the motor drives a clutch along its shaft, which you can think of as a mechanical fist. As the motor is turned on, the fist gradually closes around another shaft that in turn holds a pulley. It’s important to do this gradually so the ride doesn’t jerk riders around when it’s starts. The 6.75" pulley runs a belt to a larger diameter 21" pulley. This is the first step in slowing the number of rotations down to a reasonable rate, 1740 rpm to something less, about 560 rpm. 

The larger pulley runs a gearbox.  Within this box is a worm gear that drives a spur gear which couples directly to the drive shaft - this is how we get from horizontal to vertical rotation.  This also does another speed reduction equal to the number of teeth in the spur gear, which in our case is 29.  Our drive shaft is now down to a modest 19 rpm.  Now that we have the vertical drive shaft spinning at a reasonable speed, we can use it to turn the carousel itself.  At the top of the drive shaft is attached a pinion gear which drives a chain (like your bicycle) to a larger main gear attached firmly to the carousel, which in turn spins around the center pole. The ratio of the number of gear teeth from main gear to pinion gear is about 3.5, so in this last step the 19 rpm of the drive shaft are translated to a reasonable 5.5 rpm of the main gear and carousel. Now the motor power has been transmitted to the sweeps that hold the horses.   

With each one of these reductions in rotation speed, we gain the ability to turn with more force (called torque) because the energy has to go somewhere. So the several steps down in rotational speed from a small diameter piece to a larger one allow us to take a high-speed low-torque motor to a low-speed high-torque gear that turns the whole carousel.  That’s the only way the 30 x 150lb = 4500lbs of horses, plus all the cranks, sweeps, canopy, and the riders can be made to turn off a relatively small motor.  The Wackenhammer carousel motor is a 5 HP motor.  This is far less powerful than the engine in your car (120 HP driving tires at 840 rpm) but it can turn a carousel that weighs about 8 tons with riders...slowly.

So now the carousel is able to spin around for the amusement of all riders.  The horses could just be hung off of the radiating arms (called sweeps) and turn around in a circle.  But we’d like them to also go up and down, like a real horse would when galloping.  Savage’s innovation was to put a stationary rack gear up at the top of the carousel solidly connected to the non-moving central pole, then to put a meshing gear at the end of each of the cranks from which hang the horses.  As the mesh gears are driven along the stationary track, they cause the crank to spin. The bends in the crank when turned make the horses go up and down about twice per carousel revolution, mimicking a gallop.

Even with the additional torque we pick up from all the diameter ratio juggling, it would still not be enough to lift all the horses and riders simultaneously without the carousel grinding to a halt. Fortunately, physics holds one more trick for us to play. If a force on one side of a rotating system pushes up, we’d like an equal force pushing down on the other side to keep everything in balance.  If you look closely at the cranks on the carousel you will see that they are installed in opposition.  That is, the cranks are in the down position on one side (horses in low position) and in the up position on the opposite side of the ride.  Then as the carousel spins, the horses are always balancing each other's weight, like a funicular or ski lift.  It also adds to the illusion that these are real horses racing along, because they all run a little out of phase with each other.

A little history:  Wackenhammer’s carousel is a 1956 Allan Herschell carousel.  The Allan Herschell company was a respected and prolific manufacturer of carousels from the 1880's through the 1960’s, when it was sold to Chance Rides.  This carousel was designed to travel and was part of a moving carnival until it was set up in a building in Hyannis about 30 years ago. It was moved from it's indoor location to the Wackenhammer courtyard in 1998. While it means that we have to disassemble the ride every winter for storage, it does mean our riders experience a thrilling horse race in the fresh air and sunshine.   We run the carousel Memorial Day through Labor Day, come by sometime and take a spin!

Virtigo is Born!

It has been quite some time since I have updated progress on our climbing game.  Well, I managed to stuff all the important bits into the case at the end of last summer and installed it next to our Treadwall for a little testing.  The speaker was not loud enough in our noisy venue, so I have upgraded the amplifier over the winter.  We still owe it a nice piece of glass over the upper portion to protect everything and keep it all clean.  Still it seems to have come out nicely! There is even a fine yodeling song that plays while you climb.  The display shows average climb on the left and maximum climb on the right.  Will you try to beat that score?  I hope so!

-Otto

It's What's Inside that Counts!

 Numbers!  What would an arcade game be without a way to see your score?  Fortunately, while rummaging through our arcade workshop, I found two old mechanical displays under the bench.  These are about 5 inches high and have 4 numbers each which is plenty for my climbing game scores.  I'm not sure what previous game they came out of, but they are pretty interesting. The numbers 0-9 are displayed by turning on or off the standard 7 segments.  Each segment however is mechanically driven by a small solenoid.  A white bit of plastic flips 90 degrees and is either visible when horizontal or hidden down under the cover when vertical.  Each number is driven by decoder that translates a 4 bit binary number into commands for the seven individual segments. On the whole this is an awesome alternative to LED displays and quite in keeping with the machine's mechanical nature.  The best part is the very satisfying click-clack sound they make when they are counting.

Seen here are all the electronics we shall need to run the game!  The silver box to the left bottom is a 5V and 12V power supply.  The black box right is the Raspberry Pi computer.  Two stepper motors and two servos motors are below that.  The center tan board is a variety of interface logic and connectors. The only thing not pictured is a couple of speakers for the yodeling sounds and a bell to announce high score.  Also not pictured is about 200 lines of software (in "C") that is now written and tested to run the whole shebang.

Next step...installing it all in the case!

Move your Carcass!

During this long cold season when Old Man Winter chooses to trap us in our homes by piling multiple feet of snow at our doorsteps, I find that progress on my various projects is inevitable. Certainly, I have had plenty of free time recently to sit by a crackling fireplace and read Sherlock Homes stories to the Wackenhammer children, both of them rejoicing in their snow day freedom from classes. On a happy note, we discovered that snow ice cream is much better with chocolate sauce applied liberally.  Still, I have managed now and then to sneak away from this sleepy reverie down to my basement workshop and apply sharp cutting tools to the two large sheets of sandeply I procured for the Treadwall game case to slice them into back, side, top and bottom pieces.  This was followed by a flurry of assembly activity with glue and nails.  As shown here, basic carcass, as the case skeleton is called by cabinetry makers, is done.  A door will cover the lower portion, glass the top.  Do not be fooled by the perspective, this is a huge piece, 7 ft tall by 3 ft wide by 1 ft deep.  Mrs W. has chosen a nice Early American stain for the wood. Her sanding and finishing efforts have been well rewarded, the piece has a deep, rich, antique look to it.

Hmm...I'd best get together some interesting bits to put inside...
-Otto

Title: It's All Quite Moving!

We didn’t always have motors. Before about 1870, we only had engines. There is a basic difference between engines and motors; engines convert heat into mechanical work while motors convert electricity into mechanical work.  During the Industrial Revolution everything ran on some form of James Watt's magnificent invention, the steam engine (1780), because mankind had not yet figured out how to generate electricity, but still needed some way to turn the shafts of their factory looms and newspaper presses.  Indeed, the Steampunk aesthetic itself that we espouse at Wackenhammer's harks back to those days and envisions a Jules Verne-inspired present and future where neither electricity nor the internal combustion engine were ever invented and so the world and all its myriad devices still run on that quaint form of power conversion, steam.  Steampunk has also retained Victorian fashion into the bargain, but that is another story.

Steam machinery has gradually been replaced by more efficient, cleaner, more reliable and less complicated technologies.  Diesel engines have run our trains since about 1930.  Cars have been made with gasoline engines since about 1920. Starting around 1870, electric motors have come to run everything else.  Engines require a constant supply of fuel (coal, petroleum), which is burned, producing nasty exhaust. Steam engines also require a vast quantity of water.  Motors simply take in electricity and produce work quite cleanly in a compact, simple  and reliable package that is extremely easy to control. There is no fuel or water to store or pipe about and no exhaust released.  Of course we use them where we can!  The great irony is that nearly all our modern electricity is produced by generators turned by giant engines which are generally based all or in part on...you guessed it...steam.

Unfortunately, our Treadwall game will not use any steam-driven components.  It will use motors.   But what kind of motors will we use?  Motors these days come in many different flavors, shapes and sizes. A typical motor has a set of magnets positioned around a spinning shaft that is itself surrounded by coils (windings) of copper wire wound around an iron core.  When electricity flows through the wire the iron is turned into an electro-magnet.  This attracts or repels the surrounding magnets.  By energizing the coils in the right order around the shaft it can be made to turn.   A basic motor choice is AC or DC power which determines how the electricity is commutated into the windings. AC motors count on the fact that the voltage changes direction.  DC motors use a pair of brushes to put the current into a particular set of windings that changes as the shaft spins.  See  this excellent reference for more info.

The strength of a motor is basically proportional to its size, tiny motors vibrate your cell phone, while gigantic motors drive a streetcar along its track.  A motor's size and design will determine its speed-torque characteristics.  That is how fast it turns in Revolutions per minute (RPM) and the force it can exert.  Torque is expressed in units like inch-pounds.  A 10 inch-pound torque motor can push 10 pounds around at the end of a 1 inch lever or 1 pound at the end of a 10 inch lever.   Speed and torque can be traded by the use of gears.  Gears will reduce the speed of a motor but increase its torque by the same amount.   So you can have a very fast motor that is weak or by adding a gear box you can have a slow motor that is very strong.  A gearmotor is a motor with a gearbox attached for just this effect. Small motors tend to spin so fast (1000’s of RPM) that they are not very useful without a gearbox.  

The picture shows a number of motors.  The largest one at the bottom left is a windshield wiper motor.  I happen to like this motor very much.  Since it is a car part, it is readily available on the surplus market for about $20.  It is a 12V gearmotor that has torque in the 15 foot-pound range at 30 RPM.  This makes it an ideal motor for my animatronic projects.  The tiny motors bottom right are DC toy motors and could be used to drive the wheels of a battery operated car.  Since the motor is ungeared, it runs very fast with low torque.  Your toy car will go fast but will be easily stopped by your thumb on the wheel.  The motor left center with the long shaft is a 12V DC gearmotor, with a 2 RPM, 5 ft-pound output for about $15, the cylinder is a small DC motor, the square box is the gearbox.  The flat motor center right is a so-called timing motor as they are used in washing machine timer applications.  They are geared 120V AC motors that go 2-30 RPM but are very low torque even though it is a gearmotor.  All of these motors share the characteristic that they are free-running, you plug them into the appropriate voltage and they spin.  With a DC motor you can even choose the direction of spin.  

For the Treadwall game I am going to use two kinds of motors that have the advantage that the computer can precisely control their rotation.  The stepper motor shown upper right with the colorful wires has its coils separated, so that the computer can choose how to energize them.  By doing so in the right order, this motor can be placed precisely at 200 positions over 1 rotation.  This allows the speed and direction of its spin and the number of times it turns to be very precisely controlled.  A stepper motor can be identified by its having 4, 6 or 8 input wires instead of 2.  Stepper motors are complicated to drive and usually require a driver circuit.  The nice people at Polulo sell this motor for $15 and the controller for another $5.   Two of these motors will be used in the game to turn a 5 ft long screw shaft each.  A nut on the shaft will move up and down as the shaft is turned.  In this way the computer will be able to control how far the nut moves up and down the shaft very precisely.  A little man glued to the nut will indicate the climbing height that the game player has achieved.

The other motor I will use is called a servo motor.  The rectangular box on the top left is one of these.  They are always in this standard form factor.  They always have 3 wires: power, ground and control. Control is done by a series of pulses in a format called PPM that the computer can output.  This motor does not spin.  The servo has internal gearing and circuitry such that the shaft will only move over at most half a circle (180 degrees) range determined by the pulse width present in the control signal.  This type of motor is often used to steer Radio-Controlled (RC) cars, boats and planes. It is a remarkable package and can be purchases at hobby suppliers like ServoCity for $5-$100's depending on the speed-torque rating. I plan to use a small servo to display a simplified clock to show the game participant how much time he has left to climb.

Hmm....Maybe steam would be simpler...

-Otto

We're on the Case!

Have you ever tried to LIFT an arcade game? Well take my expert advice, don't try. They are unbelievably heavy, surprisingly heavy, inordinately heavy.  When we bought the arcade, we rearranged our games from the former owner’s grouping scheme into our own, so we moved almost everything.  At this point, I hypothesized that they had all been hogged out of solid blocks of some dense base element like Tungsten or perhaps depleted Uranium. To be sure they are built to last. They are certainly built to be immovable by your average arcade patron, which may be why manufacturers make them this way. Of course, this makes them only marginally movable by your average arcade owner.  Some have built-in casters, but in older games these have generally either fallen off, jammed irreparably or are permanently oriented in directions that oppose any desired direction of travel whatsoever. The smallest games in our arcade require a 6 foot male staff member with our 10,000 lb capacity two-wheeler to move.  A typical video game cabinet would fall into this category, 150 to 200 lbs, 6 feet tall, maybe 2 by 3 ft footprint.  The next size up are a couple feet larger in every dimension and weigh in the 350 lb range which means that one man with a two wheeler can't quite get them tipped up to move.  These games can still be repositioned by two men and a couple of moving dollies. Then there are the monsters, 10 or 15 ft long, 6 feet wide and high and 1000+ lbs, requiring a minimum of 4 burly men to move about.  Sometimes if you are lucky, these separate into 2 pieces like a screen from a set of seats or a base from a ball lane, but sometimes they are just one big piece like a mini movie theater or a set of connected skee ball lanes.  You don't move these that often and you think carefully about it before you do.  Our Treadwall for example was assembled in the place where we wanted it.  We may never see that piece of floor again in our lifetimes.

Why are they all so heavy?  Simple, heavy materials.  The outer cases are almost always made out of Particleboard (lower example in photo) or Medium Density Fiberboard (MDF) coated with a resin product called Melamine.  4x8 ft sheets of this product are often referred to as simply "Melamine."  If you have ever bought some assemble-it-yourself furniture at IKEA you will be well acquainted with this particular substance. The IKEA people make everything out of it.  These so-called “engineered wood” panels are made by taking wood chips or sawdust, mixing it with a resinous glue and extruding it into a flat shape.  The outside is then coated with melamine to give it a uniform appearance. It is one of the cheapest construction materials you can purchase, hence its widespread use in the furniture of college students and divorced men (song by Jonathan Coulton).  It is particularly good for cheap furniture and arcade games because it is dimensionally stable unlike, say, actual wood. Wood contracts and elongates with temperature and humidity more across the grain than with it.  Try to make anything large out of wood boards and unless you observe very specific building techniques that respect the grain direction and leave room for expansion, it will all crack apart come winter.  Not so with melamine.  Also, wood tends to warp, cup and twist as its moisture content changes, particularly in a wide board.  Again, not so with melamine, even large sheets stay very flat over time.   The downside of this product is that it is very heavy, essentially the weight of the glue not the wood.

There is another very common product, which I am sure you have dealt with if you have done any construction at all, and that is plywood (center example in photo).  Here, thin sheet-like layers of wood are glued together, with 4 or 6  alternating layers perpendicular to each other.  This gives the panel strength in all directions, prevents much of the directional deformation that boards get and is heavier than wood but much lighter than melamine.  One can even purchase plywood with the outer layers comprised of a nice hardwood, like oak or birch, so that the finished product has a pleasant wood grain that can be sanded and stained attractively.  Most kitchen cabinet interiors are made with plywood.  However, door fronts are generally still constructed with boards.  Why?  Because of the edges.  The layered nature of plywood makes the edges nasty-looking, difficult to stain and impossible to shape in any way. They essentially must be hidden.  Again, melamine does not have this issue, all parts are coated and look the same, another point in its favor.

So what do we choose for the new Treadwall game case? Frankly, I don't like Melamine. It is heavy which is annoying when working with 4x8 stock sheets. I also don't like the way it fails. Pull a screw out of wood and you get a hole and maybe a splinter.  Pull a screw out of melamine and a 4" diameter "chunk" that extends halfway through the board will come with it, you will never put a screw in that location again. It swells horribly and falls into bits if water gets past the melamine into the core, usually at a a worn edge.  It seems like every game we own has at least one corner broken off for this reason and they never glue back on quite right.  It also does not have great strength, the sad sag in the middle of your self-assembled bookshelf will demonstrate that fact to you.  Most important, melamine looks far too smooth and modern for our Steampunk aesthetic. We are looking for a victorian age machine, so nicely stained wood surfaces are indicated.  I have found an interesting product recently in our local Home Despot called SandePly (top example in photo), which happens to be made in Ecuador.  It is like a plywood in that it has thin attractive outer layers. However, the inner layers, rather than lots of thin crossed layers instead are replaced by a number of small boards laid side by side and end to end.  These all run with the grain so strength across the sheet is reduced somewhat. The nice thing is that as a result, the edges can be shaped with a router and stained, particularly on the edges that run with the grain.  I bought a couple sheets and have cut out all the parts of the Treadwall game cabinet from them. I even cut a number of "boards" out of this material that I will use to make a standard panel-type door for the front access to the inside of the machine. So far I am quite pleased with all the routed edges and the way they take stain.

To finish the thought: So the outside of the games are heavy, often also the guts of a game can be heavy.  Some have tube-style TV monitors, heavy all by themselves.  Some have large power transformers, great windings of copper that take the 120V wall current and transform it down to 24 or 12V for the game electronics.  These can be quite large and weigh 20 lbs in a big game. In some games like basketball games there is a entire additional frame made of welded steel holding up all the melamine boxes that adds significantly to the weight.  Still others come with large panes of glass so you can see the balls you are pitching into the holes but not touch them.  Many games will have two or three of their sides made entirely of ¼” safety glass, which is quite heavy.  Glass is always used in arcade games rather than its lighter friends acrylic or plexiglass as it is much less prone to scratching and the only thing that can stand up to harsh customer use. I do see what I feel is an unfortunate trend in the game industry to “bigger is better.”  What used to be a nice game adequately contained in a standard video game cabinet has since grown into a giant wall screen display with four huge gun stations, vibrating seats and flashing light turrets. The game play is not really any better, but it does cost and weigh a great deal more...oh my aching back...

Next step: Assembling the case carcass

-Otto

You'll Pay For That!

Perhaps you have heard the old saying, "There's no free lunch." Certainly, I am inclined to agree.  When they say come in here for a "free set of dishes," they do not adequately warn you that in order to get them you will have to resist the purchase of a timeshare you can't really afford, located someplace you don't really want to visit again for two separated weeks every October, over the vigorous protestations of an extremely persistent salesman for a full two hour period. When the on-line merchant offers you "free shipping," it is only if you continue to load your virtual shopping cart with additional goods worth at least twice what you wanted to spend in the first place.  In this respect, Supermarket coupons are certainly the most insidious. Buy something at the market, anything, and you will invariable receive at check-out a "buy 1 get one free" coupon for a similar product that you don't really like.  But go ahead and use that coupon and out will come yet another for a similar product that you like even less, but this time the deal is "buy 2 and get one free" and so forth.  Dear Mother Wackenhammer, God love her, was taken in by each and every one of these dastardly offers. When we finally laid her to her eternal rest, there among her most cherished possessions was a "buy 23 get one free" coupon for a brand of condensed canned milk so obscure that the label (loosely translated) read "Best in all CCCP, Yum!"  And is it my imagination or is it now the rule rather than the exception that militant marketeers stalk the front of every discount shoe store (is there any other kind), their pockets stuffed with "buy one pair, get a second pair of equal or lesser value at 10% off" coupons just waiting to be thrust into the hands of any unsuspecting woman who might possibly need shoes as they pass by.  It should be a crime.

In our arcade, life is much more simple.  Each game has a sign that says, for example, "2 Tokens." You place 2 Tokens in the coin slot and the game begins.  No fuss, no complicated discount structure, no shipping, no handling, no coupons for the next game.  You simply...pay. 

Some people ask us "why Tokens?" why not just use quarters at the arcade?  There are a number of reasons: It keeps all the cash in the Token machine, which means thieves have no incentive to break into the games, but more importantly so that the staff can record the day's revenue by counting the money in the 1 Token machine rather than having to empty quarters out of 40 individual games. On the downside, some number of Tokens do walk away in customer pockets as souvenirs or "we'll spend these when we come back tomorrow" but they never do, so we do need to buy a quantity of new Tokens every year.  The arcade was running with Tokens when we bought it, so we have stuck with them.  It is actually not trivial to change back to quarters, let me explain why.

Behind the coin "slot" in an arcade game, or vending machine is a complicated little device called a coin mechanism or "coin mech" for short.  Some coin mechs are purely mechanical, like the ones you see on coin-op washing machines.  You put in some number of quarters vertically in a row and push in the bar they sit in.  The coins disappear and the device is activated.  The coins must be of a certain size or they will not fit in the slots or fall through it.  There must be a correct number of coins or all the mechanical stops will not be lifted and allow the bar to be pushed in all the way.  It is a simple device that rarely jams, which is nice. Also, it can be used to push either an electronic switch or a mechanical lever to unlock the functions of the game or vending machine. However, this mech can be fooled with worthless slugs that are the same size as a quarter.  

More sophisticated coin mechs are called "roll down" mechs (shown in the picture) as the coin rolls down a tilted ramp past a series of slots.  If the coin is the wrong size, it falls out of a slot to the coin return. If not, it falls into a chute to a capacious coin box.  On the way through the chute, the coin pushes down a thin wire lever attached to a small electric switch (blue in the photo), which sends a signal to the game's brain that the coin has been deposited. These mechs typically contain magnets that divert steel slugs to the coin return as well.  Better ones also have a mechanical lever on the coin chute that acts as a one-way valve. This prevents so-called "stringing," where a thief ties a string to the coin and tries to pull it back up and out of the mech once the game is activated. These mechs are unpowered and completely mechanical except for the switch.  On the downside, these mechs are designed to work only for one specific coin diameter. Our Tokens are 0.94 inches, which is an industry standard, a little larger than a quarter.  If we wanted to operate on quarters rather than tokens, we would have to change out the coin mechs in every game. In more modern games (1970's) this is the swap of a small square plastic module of the overall mech, in older games it means unscrewing the whole mech (like the upper one in the photo), face plate and all.

The latest technology solves this problem nicely.  There is a coin holder (under red dot in the photo) on the mech where the owner inserts the desired coin.  This action sets the size of the coin that the mech will accept.  It also measures the electrical conductivity of the coin which is a surrogate for the coin material.  Coins placed in the mech must meet both size and material property as compared to the desired coin type. Those not conforming are rejected to the coin return. If you want the game to operate with quarters today, dimes tomorrow and Tokens on Thursdays, you simply change the example coin in the mech. I use these mechs exclusively when building new games, like the Treadwall game currently in progress. One can get nice ones from China on Ebay for about $20. These are electronic, they take a 12V supply and put out a short pulse on an output line when a coin is accepted.  They also have a hookup for a coin counter, a useful device which increments a set of numbered dials when it gets a 12V pulse. This lets you know how many coins have run through your games, giving you an accurate measure of their popularity and amount of usage/wear.

Who ever thought there was so much going on behind that little slot...

-Otto