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  #1  
Old 01-02-2017, 04:47 PM
rzbill's Avatar
rzbill rzbill is offline
 
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Location: Asheville, NC
Posts: 2,550
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!
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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 05:03 PM.
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  #2  
Old 12-26-2017, 12:03 PM
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ColoCardinal ColoCardinal is offline
 
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Location: Morrison, CO
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Default

Bill,
After using your creation for a little while, is there anything you would change on your design?
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N16CB RV7A
Airworthiness cert issued 12/24
best X-mas present I could have hoped for!
paid 'til 10-19
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  #3  
Old 12-26-2017, 02:03 PM
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GalinHdz GalinHdz is offline
 
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Location: KSGJ / TJBQ
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WOW! That is simply brilliant!!!

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CP-ASEL-AMEL-IR
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  #4  
Old 12-26-2017, 03:43 PM
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rzbill rzbill is offline
 
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Quote:
Originally Posted by ColoCardinal View Post
Bill,
After using your creation for a little while, is there anything you would change on your design?
Hi Carl,
To be honest, I have not used it for steering the nosewheel yet, other than the test in the image. Its a tool for me to use in a pinch and I have not gotten in one since then (although I was close last weekend pulling the plane into the hangar and I got a little fouled up). I still pull on the root of the prop. I have used it in its control lock mode every week since it was created and it is working fine for that.

Sorry for the incomplete feedback. You are probably right that I should try to use it more for steering than I do. I have a lazy streak........

And thanks for the compliment Galen.
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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
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  #5  
Old 12-26-2017, 05:05 PM
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ColoCardinal ColoCardinal is offline
 
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Location: Morrison, CO
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I wouldn't say that you're being lazy. Doing things the easiest way, as long as it's equally effective is just plain SMART!
I'll give your design a try if I can find some crutches. Do you remove the cap screws and use the slotted pins to insert into the threaded hole that they would have threaded into or are they meant to insert into the heads of those screws?
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Carl - - Morrison, CO
N16CB RV7A
Airworthiness cert issued 12/24
best X-mas present I could have hoped for!
paid 'til 10-19
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  #6  
Old 12-26-2017, 05:20 PM
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rzbill rzbill is offline
 
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Location: Asheville, NC
Posts: 2,550
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Carl,
Those 'studs' I made out of AN bolts engage with the allen socket of the SHCS that mounts the nose fairing. When I built the fairing originally, I only drilled a hole big enough for the allen wrench to pass. I also changed to a longer SHCS and spacer to get the bolt head to reside just barely inside the fairing hole. This is important so that the tow bar width travel needed to engage is minimized.
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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
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  #7  
Old 12-26-2017, 05:37 PM
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ColoCardinal ColoCardinal is offline
 
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Location: Morrison, CO
Posts: 322
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Good plan; I like it.

Thanks
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Carl - - Morrison, CO
N16CB RV7A
Airworthiness cert issued 12/24
best X-mas present I could have hoped for!
paid 'til 10-19
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