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Tail Wheel Swap to a Matco Pneumatic 8"

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Posted (edited)

I removed my little Maule 6" hard rubber tail wheel and put on a new Matco single arm pneumatic wheel (WHLT-8). The basic wheel swap was easy, one bolt, but while at it I cleaned up the whole tail wheel area:

1) I removed the Matco 45 degree wings and put on some 25 degree ones to match the Avid's rudder rigging. Had I left the 45 degree ones on, the wheel would never unlock, yielding wider turns,and crappy manual ground handling because the wheel would not swivel fully.

2) Re-bent the spring to angle the wheel down a bit. The spring had flattened enough to make the wheel pivot axis point forward, perhaps 20 degrees off the vertical, thus making the wheel lift the whole tail when it pivoted. A local car spring shop (search Automobile Suspension, leaf spring) did it while I waited for $20. Now the wheel is almost purely vertical. I bet they could have made a new one easily, too.

3) Extended the steering arms at the bottom of the rudder using a flat bar of 1" x1/8" aluminum. This extended the horn about 1.5" per side and made the steering more powerful and kept the geometry of the springs square. I bolted the flat to through old holes.

4) Rigged the springs using some threaded quick links which are much easier to use than the previous spring clips (https://www.amazon.com/gp/product/B00M9FAPYK/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1)  I used #35 sash chain which has a working strength of 106 lbs, and which can be easily opened and built up to desired lengths.

Taxi and flight tests showed great improvement in handling, the basic lock in the trail position is stiffer and steering commands are much crisper (I bet the increased steering arm was as much responsible as the wheel). Landings track straighter now, the wheel is locked more tightly in the trail position. The big spring on the right is a bear to deflect now, but tells me positively that I am getting right wheel deflection. Another positive note: the tail wheel no longer acts like a phonograph needle for all the bumps and cracks in the tarmac, taxiing is quieter.

I got some tail wheel shimmy, so I tightened up everything after the flight (found the spring to fuselage bolt had lost torque, allowing the spring to rotate enough to be the cause).

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Edited by nlappos
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Posted

I would highly suggest adding some eye bolts to lessen the angle of the chains in comparison to their pull direction.  The handling will further improve.  You would then be able to get rid of the speed links which are known to fail often.

 

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Posted

Where would they go? 

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Posted

they go into the holes on the rudder bar and hang down to lessen the angle of the chains.  That really helps the geometry.  I just bent the rudder bar extension that I made from flat bar steel to look like an old top hat so the arms dropped down and inch and a half.  That really made a difference!

Nice write up Nick!

:BC:

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Posted

I put them on the bottom of the rudder bar and on the top of the tailwheel arms to lessen the angle of the chains.

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Posted

Thanks, Nick.  There are, for me, some keeper ideas here.  I think I will also install a bar to extend the rudder horns to the same width as those of the tailwheel.  The uneven spring pair is evidently offered as a way to mitigate shimmy, but with a left-turning prop, and hence greater on-ground P-factor thrust on the left side, I think I will break with tradition and swap the stiffer spring to the left side.  I think I'll keep my Maule TW for now. Plunka-plunka-plunka!

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