Boeing 737 rudder pedals construction

[mauriceb]

I have finally completed my linked rudder pedals (minus interface). I used real Boeing pedals but the linkages started with an idea from Alain Tremblay (thanks Alain) which I modified as I wanted to use gas springs instead of elastic bands for the tension on the pedals.

Well, this turned out to be an ordeal as I am very lousy at visually how things work mechanically and I had to basically try & fail a hundred times before I got them working the way I like them to work.

The gas springs for the brakes were easy enough to figure out, but the gas springs for the pedals were another thing. I finally found a way that works perfectly and the key part was to have one end of the gas spring not attached to anything but still be able to remain in a certain track at all times. I did that by enclosing them inside a tube. The tube itself is attached at one end and is able to pivot.











This is how it works. When I push on one pedal, the associated gas spring compresses normally and the gas spring on the other pedal is simply pulled out of the tube by the other pedal since it is only attached to the pedal arm and is free at the other end.

When I release the pedal, the centering is done automatically since both gas springs exert just a tiny bit of pressure on the pedals without compressing the gas springs at all, so the pedals always come back to exact center. If the gas springs were attached at both ends, then the gas
springs would both have to be compressed half way at the center neutral position and the center position would be hard to maintain properly unless both gas springs exerted exactly the same tension at the center of their travel. I'm not an expert with gas springs, but I would think this would be very hard to achieve due to different tolerances.

I must say I love the feel of the gas springs. It is always smooth and never jerky at all for both for the pedals and the brakes and I'm very happy with the results.







And now, all I have to do is figure out how to add the pots & interface. Piece of cake!

More pics here:
http://good-times.webshots.com/album/560928860GxpIoQ

Maurice

[dodiano]

Beautiful!!! Simply Beautiful!! Hope you can make a tutorial of some sort or some links to get the materials!! This is amazing Work!!

Regards,

Roberto

[Michael Carter]

Outstanding engineering. They are beautiful Maurice.

What is the weight of compression for the springs?

[Westozy]

Great work Maurice, a big thumbs up from this engineer! I would suggest a linear (straight) pot on one of your pedal push rods.

Gwyn

[NicD]

Superb work Maurice - thanks for the pics and information too .. very helpful. All I gotta do is find the inspiration to start on them now!

[Tomlin]

Awesome to see them put to good use Maurice, and Im still elated you bought them from me! They obviously went to very capable hands. I wish you the best in getting them interfaced.

[PaulEMB]

Excellent Maurice,

An inspiration for us - shows what you can do when you keep at it. The engineering work is very good, and I like Nic have put it back on my list of things to do!

[mauriceb]

Beautiful!!! Simply Beautiful!! Hope you can make a tutorial of some sort or some links to get the materials!! This is amazing Work!!

Regards,

Roberto

Thanks, but the best tutorial I could produce would be pretty bad compared to the one I copied the idea from. As I said, I 'borrowed' the idea from Alain Tremblay and he has a very good PDF document available in his website. I'm sure Alain won't mind if I include the links here:
http://www.sim-737ng.com/rudder/rudder.htm
http://sim-737ng.com/rudder/Assemblage_pedaliers.pdf

The main changes I made were to add gas springs instead of rubber bands for the tensioning and the pictures are self explanatory I think (I can answer other questions you might have though)

Maurice

[mauriceb]

What is the weight of compression for the springs?

I have no idea, but I guess about 25 lbs. I got the springs from Eric when I bought the pedals and Eric likely has a more accurate idea. It's not that critical though as you can vary the tension by the location of the springs. That's why I have so many extra holes in the linkage T bar . Lots of trial & error.

Maurice

[Michael Carter]

I like yours better.

What weight of compression are the gas struts?