How Not to Build A Spinning Tunnel

First of all, everything on this site is for information only. In no way does the author make any claims as to the safety, reliability or engineering of any of the items on this site. It is the responsibility of anyone attempting the project to ensure the safe construction and operation of the attraction.

Safety needs to be the primary concern of this project. There are moving parts, and some of these are quite large. Guests will be traveling through this moving tunnel. Every effort needs to be made to ensure the safety of the guest. Complete inspections (including tightening all bolts) should be performed daily.

I've built two tunnels in my lifetime. The first was originally patterned after "The Black Hole" and featured plywood rings for the tunnel. I did the construction outside, and it worked well... until it rained. And the plywood warped. So I started over using the construction method that follows. Also, my first tunnel utilized steel I-beams for the bridge. They are very heavy and very expensive. The second version utilized engineered plywood beams. Much cheaper and MUCH lighter and easier to maneuver. So the instructions that follow are based on my second tunnel, which I still own and is used at the Tam Valley Haunted House each year (visit www.timepasses.com and click on Halloween for more info about this amazing attraction).  

This version of a spinning tunnel consists of several elements:

The Framework

The framework is constructed of steel channel framing (Unistrut). Two 20-foot lengths run the length of the tunnel, and four 10-foot lengths run the width of the tunnel.  Six BMX-style bicycle wheels (without tires) are attached to this framework, upon which the tunnel rests. The motor is attached to one of these wheels.

The Tunnel

This is the main element. The tunnel is constructed of three rings that are connected by four rods, creating a cylinder. Think of a coffee can resting on its side. The each of the rings rests in two of the BMX wheels. Because there is no direct connection between the tunnel and the motor, if anyone were to fall into the tunnel, it would simply stop spinning. You can actually stop the tunnel with your hand. This will become clearer later. The framework of the tunnel is covered with flameproofed fabric and painted with UV paints.

The Bridge

The bridge is the hardest thing to engineer. Because it must span the entire tunnel, it must be beefy. You can't run a brace from the middle or it would intercept the tunnel. The bridge is constructed of two platforms on either side of the tunnel, I-beams stretched between the platforms, and a plywood walkway. In addition, hand rails are necessary. UV lights are placed along the side of the bridge to illuminate the tunnel.

That's it! Now, on to the actual constriction.

The Framework

The frame is built of Unistrut brand metal framing. This is the easiest method to use, as it allows easy adjustments.

I strongly suggest using 12-gauge solid full-channel. (warning - a 10-foot length is running about $50 in early 2014 - nobody said this was going to be a cheap project). You will need 6 10-foot lengths, 4 5-foot lengths and 2 2-1/2 foot lengths. The side rails are 20 feet long, but need to be split up into a 5-foot<>10-foot<>5-foot arrangement so that there is not a seam in the middle where one of the sets of wheels needs to be placed. This diagram shows the basic configuration. The cross beams are placed next to each set of wheels so that there is a lot of support at each point to keep the wheels from warping and tweaking.

So, in addition to the strut lengths, you will need

12 of Unistrut part #P1957 (two for each of the wheels),

8 Unistrut part #P1357 for each of the cross sections,

4 Unistrut part #P1579 for the motor mount

and 4 Unistrut part #P1067 for the two seams on each side rail.

Plus the associated number of channel nuts (and bolts) to put it all together, which I believe is 16 for the seams, 24 for the cross beams, 12 for the motor mounts and 24 for the wheel supports.

This drawing shows the basic assembly.

10 foot Unistrut is green 5 foot is blue, 2.5 foot is red, and the wheel assemblies are purple.

The wheels are mounted in a L-shaped steel strapping that is bolted to the Unistrut fitting.

You will need to drill the hole in the strapping a little larger in order to get the bicycle wheel to fit. There is no need to put the nuts back on the bike wheels (like I did)- they will stay in place on their own. The wheels are BMX wheels - the front ones without gears. The good thing about these wheels is there is a groove in them that allows the drive belt to fit without interrupting the tunnel wheels. One of the center wheels has the drive belt that is connected to the motor.

The motor is the most expensive part of this project. This one is discontinued, it has been replaced at Grainger with model 4FDZ3. It is a 288RPM 110v gearmotor. And currently sells for (please sit down) $796.50. But it will last forever (don't quote me). Mine ran 6 hours a night for 3 weeks straight for several years without complaining. I would also strongly suggest wiring the motor to a switch at either end of the tunnel and having an attendant to switch the tunnel off in case someone can't make it through.

The Tunnel

My tunnel is build from 1/2 inch galvanized pipe. Unless you own a roller bender, you will need to have the pipe bent at a fabricators. This cost about $240 including the pipe (in 2006). They would only bend 20 foot sections, so I had to recall my High School geometry and figure out the circumference of a 10 foot circle. 31.4 linear feet of pipe were needed. I wanted to be able to store this easily, so each ring consists of two 15.7 foot circles

My neighbor Steve came up with an ingenious solution for the assembly of the wheels. He fabricated a series of tabs that held the pieces together, along with a solid insert that slid into the tubing.

Here you can see the rings. Each forms 1/2 of the circle.
This is an end ring. This is the male end. The base of the "T" is where the cross brace is attached.
Here is the male end of the center ring. Notice that the cross brace can be affixed on both sides of the ring.
 
Here is the female side. When it slides into the male side, the two flanges slide side-by-side and are bolted together. Use grade 8 bolts everywhere. Standard bolts will sheer!
This is the midpoint of an end ring.
 

The 4 cross-braces are also 1/2 inch galvanized pipe. they will end up about 18 feet long, but start with them a little longer and cut off the excess when you are sure everything is working. When designing the rings and tabs, make sure half of the rings has all the tabs needed to hold 3 of the cross-braces. This will make assembly much easier.

The cover was made from commando cloth, which is a velour-like flame retardant material. It is very important that any material is flame retardant. Under no circumstances should you use vis-queen or other plastic sheeting. In case of a fire, this will drip molten plastic on your guests. You will also never pass a fire inspection. I ordered a custom-made curtain from "Sew What?" www.sewwhat.com. I had them install Velcro on all four edges, plus a strip down the middle that lined up with the center ring. The Velcro alone is not strong enough to keep the material attached. I added sheet metal screws and washers occasionally, plus I tied the material to the rings with zip ties occasionally, especially along the cross pieces. You can also add zip ties to the rings themselves; they will pass through the wheels with no problems. I painted the fabric once it was installed with a splatter technique. I swear by UV paints from Wildfire.

The Bridge

My original tunnel had a bridge made of 2 steel I-beams. They were pretty expensive, and extremely heavy. My second tunnel used engineered wood beams. I used three of them and it was very solid. I will leave it to you to work with your supplier to spec out the proper sized beams for your application. The beams are held in place with brackets specifically designed for this purpose. You will see I've added a small piece of 2x 6 to fill in the gap. You will need, of course, hefty platforms 24 inches high at either end to hold up these beams. And a way to get to that height. ADA requires 24 feet of ramp to get to 24 inches of height, so keep that in mind when planning. If you don't fall under ADA guidlines and decide to use stairs, I'd strongly recommend an attendant at the exit to assist guests, as they will be dizzy after going through the tunnel.

The beams are covered with 3/4 inch plywood.

UV florescent lights are added along the side of the beam.

The photo above shows the installation point just before installing the fabric. You will want to get all of the base plates for the railing installed before you install the fabric. Make sure the tightening nuts are to the inside edge so you don't have to reach around to tighten the rails.

The railing I used was Kee Klamp.

Lastly, you should make sure your entrance is masked so it is a simple doorway entrance. Also, adding mylar walls (or mirror Plexiglas if you can afford it) to the far wall will make the tunnel seem twice as long.

Here's a video of the tunnel in action. You need to have Flash installed and enabled in order to view it.

I hope this little tutorial is helpful in constructing what will become a highlight of your haunt. I'm sure I've made it overly simple and left out a lot of details, and I'm happy to answer any questions that you have. Email me at jbrown@timepasses.com.

Jeff Brown