Corked Nose Wheel

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smoss
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Re: Corked Nose Wheel

Post by smoss »

Any update on success of a new fin from Bret yet, or anyone able to mock up a 3D printer version?
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Re: Corked Nose Wheel

Post by Lance Murray »

I wonder if the OP got some unwanted attention from the FAA on this. They take unapproved parts seriously.
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Re: Corked Nose Wheel

Post by Antoine »

My friend in Zimbabwe came up with a solution as on page 1 of this thread. Took him 2 x 2 hours of work as he explained

1. Remove the nose gear fairing and reassemble the two halves.
(1a - polish and wax the fairing)
2. Wrap this in thin plastic film to protect the paint.
3. Laminate a "hat" out of fiberglass and polyester resin on the trailing edge side
4. Make a "shark fin" as on the picture above from lightweight plywood (1 cm or .4 in thick) and shape it to approximate an airfoil section
5. laminate this into position on the fiberglass hat. This is the critical point: the assembly must be stiff and strong.
6. Once everything is cured, pop out the hat, reinstall the fairing on the nose wheel minus the rearmost screw and simply push the fiberglass part into place. It will fit snugly...
7. Reattach the screw catching the part in position and apply some tape to the front side.

Sadly this only works legally in Zimbabwe, as the ZAA is very tolerant of homegrown solutions to stupid problems that the TC holder won't address. WARNING: If you do that, you will void your airworthiness! I do NOT encourage you to do it. Just fly with your foot on the rudder pedal. It is safer and much more legal.
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smoss
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Re: Corked Nose Wheel

Post by smoss »

Mark, any success on 3D modeling a fin?
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Re: Corked Nose Wheel

Post by smoss »

anyone still working on this project?
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Lou
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Re: Corked Nose Wheel

Post by Lou »

This weekend I finally did some work to diagnose the problem and I think I have made some progress! I built a fully castering 1/4 Scale model of the nosewheel and mounted it on a car rack as a make shift wind tunnel! :D
Quarter Scale Nosewheel model.jpg
I have theory on why this behaviour occurs and I wanted to test, firstly, if I could replicate it and, secondly, test some possible fixes.

We just took a 10 minute drive in the city to see what would happen and I am blown away by the results! At any significant speed (above 40kmh/h) the wheel would not fly straight and would swing out one way or another. The conditions are gusty and turbulent and of course there is traffic, road bumps and all kinds of disturbed air. But it still seems to suggest that the design is inherently not aligned.

I'll edit the video footage and post.

I have a theory as to why this happens but I want to do some more controlled testing: stable mount, calm, no traffic, smooth road). Then the next step will be to test some fixes. :D
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Re: Corked Nose Wheel

Post by Boatguy »

The "wind tunnel" idea is great, but doesn't the actual installation have a spring loaded mount with adjustable spring tension? Wouldn't your testing need to closely replicate the actual installation, weight of the components, etc.?
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Re: Corked Nose Wheel

Post by Lou »

This is just a fun project - really to satisfy my curiosity. I know the Bretfin works, but I want to play with some other ideas. I was mostly wondering if the scale effects would even allow a model to be used - it looks like it does, at least to some degree. I want to see if it's possible to reduce the turbulence around the strut and the swivel.
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Re: Corked Nose Wheel

Post by Rich »

My theory is simple. As I've posted before, I believe the faired nose gear is most aerodynamically and mechanically stable when cocked against the stop. Any disturbance causes it to return the most stable position.
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Re: Corked Nose Wheel

Post by Scottsware »

Boatguy wrote:
Sun Jul 19, 2020 11:44 pm
The "wind tunnel" idea is great, but doesn't the actual installation have a spring loaded mount with adjustable spring tension? Wouldn't your testing need to closely replicate the actual installation, weight of the components, etc.?
If by actual installation you mean the actual DA40 having a spring loaded mount, I’m pretty sure it doesn’t. From the look of the maintenance diagram and looking at my nose wheel, there is no spring to center the nose wheel. As far as I can tell you must have enough tension on the swiveling nose that it won’t move/shift in the air and that when you lift the nose wheel off the ground it's hopefully straight. The manual states a pull tension to test how tight the nut is tightened hold on the nose wheel fork. I use a small fish scale. The stated tension in the manual doesn’t seem to be near enough to hold the nose wheel straight in the air. Mine needs around 18 lbs of pull tensions on the fish scale ( cheap Walmart scale) to hold the nose wheel in place.

Hopefully I didn’t completely misunderstand what you meant by spring loaded mount 😳
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