Materials

There is an incredible variety of materials available at home building stores like Home Depot, Lowes and Osh. For example, a trip to the electrical section of Home Depot proved most rewarding. A 10 foot length of 1" EMT (thin wall, metallic electrical conduit) looks to provide material for both the cyclic and collective. They even have a pre-formed 90 degree bend that looks very useful for the cyclic. I thought I would have to buy a tubing bender, but fortunately, no. There was also a "short bend 90" which is a fitting that can be used to make the transition from the cyclic to the stick grip. I was going to do something else, but I think this will look nicer as well as be quicker.

Auto parts stores also have some useful stuff. When it comes to making odd shaped items like the collective switch box and the cyclic flight grip, polyester body filler is very useful. It comes in several varieties. I've had good success working with two in particular.

One type has short lengths of fiberglass  fibers mixed in. It provides substantial additional strength to the filler, nearly doubling it compared to the regular variety. It's more difficult to work with. The fibers make it pretty much impossible to get a smooth surface. The idea is to build up the basic structure of whatever you're making, then use the regular variety to smooth out the surface.

Building the Collective Switchbox

The Bell 206 collective switchbox is just the sort of odd shape that makes it a good candidate for fabricating out of polyester body filler. I didn't try to get the size spot-on. I just figured out how big to make it so the switches I had on hand would fit. I actually did not expect the first attempt to work well enough to keep, so I thought I'd re-size as needed on subsequent tries. As it turned out, it looks okay.

The Technique (such as it is)

The basic idea is to fabricate front and rear panels for the switch box, in this case using sheet aluminum. The panels are then fastened to each other using threaded metal spacers which are as long as the finished box is to be thick. At this point you've got a box with a front and a back, but no sides. The threaded spacers are near the panel edges and will be embedded in the sides. The volume between the panels that will accommodate switches is filled by a block of "dry floral foam" shaped to be a bit smaller than the width and height of the panels, and to clear a little room around the threaded spacers. 

Dry floral foam is a crumbly urethane foam sold at craft stores, and is used for silk flower arrangements. It's cheap and not dissolved by polyester resins. It's very simple to shape using a knife and sandpaper.

While wearing gloves, fiber glass filled polyester auto body filler is layered (trowelled?) over the exposed floral foam. The threaded spacers are embedded in the filler as well. This forms the sides of the box. Once the filler sets up a bit, it can be trimmed with a razor blade. After it hardens fully, it can be shaped further with sandpaper. The screws holding the panels in place can be removed to expose the foam core. (I had wrapped the panels in a bit of plastic from a plastic shopping bag to prevent the filler from sticking to the panels.) The core is then carved out.

At this point the box looks pretty rough. It takes sanding and more polyester filler to fill voids and develop a smooth surface.

Fiber glass filled polyester filler is twice as strong as the regular, unfilled variety. It's a pain to work with, though, because the fibers make it difficult to push the filler into smaller spaces. It takes some practice and an acceptance that you may not be able to get all the filler into place in a single attempt.

Building the Throttle Grip

The throttle grip is a cylinder that surrounds the collective lever near the end, just below the switch box. Looking for suitable materials, I ran across straight couplers for connecting pieces of electrical conduit. A coupler is made to just slide over the conduit. It's the right diameter but only half a long as needed. It also has a ridge midway inside so it stays centered on the conduit joint. 

Short story is I removed the center ridge from two couplers and used epoxy to glue them end-to-end. I reinforced the joint with a strip of aluminum wrapped and epoxied over it.

I glued a conduit compression fitting to the end of this assembly to become the throttle friction lock. You can see it in one of the later pictures down the page.

Building the Collective Shaft Pivot & Box 

After going through several designs on paper, I finally built what's pictured here.  The collective shaft pivots on a 4 inch strap hinge from Home Depot. A pair of extension springs provide a bit of lifting force to offset gravity.

The black roller is an experiment. I was looking for a way to add a bit of friction to the system so the collective would stay put when released, but not stick and jerk when moved. The roller is a hard rubber wheel, that's mounted on a second 4 inch strap hinge. The black knob on the far left turns a screw that pushes against the hinge, and forces the rubber wheel against the wood cam. It seems to work reasonably well, though time will tell if the wheel develops a flat spot.

On the negative side, the hinge supporting the collective has a bit of lateral play that lets the collective move sideways slightly. I expected a bit, but hoped the loading from the rubber wheel would make it unnoticeable. Well, almost, but not quite. 

I like the hinge because its use allows easy construction. I could use a short length of 1/2 inch pipe as a pivot shaft, but I would also have to make some sort of bushings. I've got some high density polyethylene that would do, but I'm aiming for "simple".  I'll use the current set up for the time being. If it gets increasingly loose with time, I'll try something else.

The Throttle Linkage

Because this is a sim, the throttle is actually a potentiometer turned by rotating the throttle grip. While the grip is on the outside of the collective shaft, but the throttle potentiometer is inside the collective switch box. The linkage connects from the pot's shaft to the inside of the grip through a slot in the collective shaft wall.

I've used a small pot with a 1/8" shaft. It's that little black rectangle in the middle of the switch box. The linkage is nothing more than an off-the-shelf brass, threaded hex spacer that I cut to length. I drilled a 1/8" hole through it and epoxied about 2 inches of 1/8" brass rod into the hole. When assembled, the brass rod is concentric with the collective shaft. The brass rod lines up end-to-end with the pot shaft, and will connect to it with a slip coupling made from brass tubing.

The collective assembly bolts to the left of the base. 

It's possible that I'm not as smart as I think I am. (Occasionally, I have moments when I know this to be true. Fortunately the feeling passes quickly.) Although I have tried to make this information as accurate as I can, it is not only possible, but also quite likely, that errors lurk within. I cannot and do not warrant these pages to be error free and correct. Further I accept no liability for the use of this information (or misinformation). If, after reading this, you are still interested, please be aware that the contents of this site are protected by copyright (copyright © 2002, 2003, 2004, 2005, 2006, 2007, 2008 by John M. Powell). Nonetheless, you may copy this material subject to these three conditions: (1) the copyright notice is copied and presented along with the material, (2) the copy is used for non-commercial purposes, and (3) the source of the material is properly credited. And of course, you may link to this page.