Monday, January 19, 2015

This Bird Will Fly Again...

Getting ready to complete the mechanical work on the control columns and the obvious problem slowing me down is I only have 1 control column. And it is one of my own design with a replica yoke from Routech.

Thinking of the cost of a first officer yoke, shipping from Europe and the associated metal work, I figured it would be cheaper to buy a real one. Over the Christmas break I found a beauty on eBay but was outbid ($676 for a control column and yoke? Madness). In the New Year I spotted another that looked a little tatty but good enough for my purposes. I was the only bidder and snagged the devil for $500. And here it is:
Once it is all hooked up I'll strip down the old paint and get it in the same shape as the captain's side. Before taking it all apart I set it up in the test frame I've been working on to see if the control arms will pull the weight of the column back to center. It does. Won't know for sure if it has enough umph until I get both in situ but for now I'm happy with the result.

Inspecting the column there's the obvious problem of the pivot point. Looks like the bees knees but won't work with my simple design. Take a look at the business end to see what I mean:

The "torque paddle" (if that is its name) must fit into the cross-member that connects to the captain's side. Instead of going industrial strength, I'm going to be using bevel gears and 1/4 inch steel rods. Bottom line, the green bit has to come off.

I wanted to do it in such a way that wouldn't damage or deform the control column. For this reason I couldn't simply cut it off. Instead I removed the paddle then drilled out the 8 aluminum rivets (yes 8 - they build these things to last) that holds the piece to the bottom of the column:

Even with all the rivets out I had to "persuade" the cast aluminum piece off with a hammer. Taking it all apart I was surprised to discover the vintage of the kit. Check this out - the thing is almost as old as I am:

Which means this rig probably came out of a 727 and not a 737, since the first 737 didn't fly until 1967. No matter to me. Very curious though as to the airplane it came off of, where it flew and when it stopped flying. It will get to fly again, albeit virtually...

And here is the dis-assembly complete:
The mustard looking shaft twists as you turn the yoke. I'll keep the upper assembly since it works fine. The trick will be attaching this bevel gear to the bottom of the shaft and aligning it with the cross connector to the captain's side:

Good news is the aluminum shroud that fits in the floor is in great condition. I can use it as a model for one I'll make (probably out of fiberglass) for the other side. It looks like it has the 10 degree forward tilt on it - interesting:

Monday, January 5, 2015

Back in the Workshop

Alrighty then, Christmas and New Year out of the way, back to work.

I've been rethinking the design of the control column mechanism, specifically the self centering . It's overly complicated for something that it is relatively straightforward. Taking cues from what others have done, I'm now experimenting with a simple "pull me, push you" approach.

First step was to saw off the end of the screen door closing mechanism and to put a thread on the rod:

The thread allows ease of adjustment to get the control column center just where I want it. Next I made a simple bracket out of HDPE (High-density polyethylene, the stuff quality chopping boards are made of) to anchor the other end of the closer to the frame. HDPE machines very easily on my table saw and offers up a low friction surface:

With the closer attached to the swinging arm I tested the resistance. Feels about right but I won't know until I have it loaded with the control columns, yokes etc. The idea of this design is that when the arm swings towards the closer, the rod passes through the opening in the swing arm. When it goes in the other direction, the end of the rod engages and pulls the arm back to center:
I'll make up an HDPE bracket for where the closer rod ends meets the swing arm. At this point just testing the concept. So far so good. Next I'll mount the control columns and yoke for a fuller test.