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Old 01-02-2017, 03:47 PM
rzbill's Avatar
rzbill rzbill is offline
Join Date: Nov 2005
Location: Asheville, NC
Posts: 2,574
Default RV-7A Custom Towbar/Control Lock

Due to the holiday week, I have had more "shop time" than usual.

One of the things I have been thinking about was a replacement of my current control lock. This was an idea stolen from a Diamond DA20 I flew some 10 years ago. My initial implementation was OK except the interface to the rudder pedals was a bit light and it popped off once, giving me a dent in the rudder that very very windy day.

So, a few months ago, I saw and picked up a couple of discarded aluminum crutches by the side of the road. Perfect.....

I did a jury rig proof of concept at the hangar and then an evening in the shop to fabricate it to final form.

Here is my old control lock

Below is the spare crutch, partially fabricated new unit and my old control lock.

Next is the finished new unit.

Details of the "spreading and clamping" mechanism. The springs are strong enough to spread the jaws when I unscrew the knobs. Loosten the knobs, engage with nosewheel and tighten knobs. There is a stop to prevent overtightening. I thought about a cam mechanism but this was cheap and easy. We'll see if it is too much of a nuisance to use.

Details of the wheel engagement pin. It was an AN5 bolt. Its threaded into a slug of steel inserted into the tubing.

The below image shows the device in place as the control lock, pretty much like the original Diamond idea.

Below it is engaged with the nosewheel. The finished version is a lot more robust than the initial "test" run (jury rigged with threaded rod and a bunch of nuts) which is good. The test run was a little "iffy" and I was concerned about it popping off. This feels good and solid. We'll see if that remains true in use.

So.... just over 10 bucks for the knobs and springs. The rest was trash or stuff from the multitude of jars in the shop.

Thanks all.
I hope holidays were good for you. Too short as always!
Bill Pendergrass
ME/AE '82
RV-7A: Flying since April 15, 2012. 750hrs
YIO-360-M1B, mags, CS, GRT EX and WS H1s & A/P, Navworx
Unpainted, polished....kinda'
My RV Construction Page

Last edited by rzbill : 01-02-2017 at 04:03 PM.
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