Corked Nose Wheel

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Rich
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Re: Corked Nose Wheel

Post by Rich »

Scottsware wrote: Mon Jul 20, 2020 12:37 am
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 😳
The spring load is basically a shimmy dampener and also function as Scott says.
2002 DA40-180: MT, PowerFlow, 530W/430W, KAP140, ext. baggage, 1090 ES out, 2646 MTOW, 40gal., Surefly, Flightstream 210, Orion 600 LED, XeVision, Aspen E5
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blsewardjr
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Re: Corked Nose Wheel

Post by blsewardjr »

My DA40 has been flying with a consistent left wing low attitude with AP on so decided to join the no NLG pant group. Seems to have helped, but has not cleared it up completely. No apparent loss in TAS.
Bernie Seward, IR, AGI
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smoss
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Re: Corked Nose Wheel

Post by smoss »

Well, since it doesn't look like anyone is going to try and 3D model and print a fin, I finally mocked one up myself using 90 degree angle roof flashing, cut with a Dremel cutoff wheel, and bent to shape to mold/fit to the pant angle under the bolts. I put a few layers of polyethylene tape under the mounting area so as not to scratch the fairing. The shape I cut was nothing magical, just the largest shape I could cut from the piece I had. I have not tried it out yet, but am very eager to. I assume that if it is working, my plane will then fly uncoordinated, with the ball to the left (as when it is corked the "wrong" way), since it is currently trimmed for the typical sideways nosewheel. Do folks think this is big enough and rigid enough to work?
And if it does work, any issues people may see with it being metal, instead of a non-conductive material? The whole nosewheel setup by design is connected to the electrical bonding system.
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Re: Corked Nose Wheel

Post by Antoine »

Hi Steve

Metal is probably not great for damping in this highly turbulent flow area. You need a stiff structure to resist the prop blast and internal damping to avoid it becoming a resonator that’s triggers some unexpected effects.
I used a plywood core: this allowed me to easily carve it into an airfoil shape and then trim it down to the right size.
The fin that is shown on the photo on page 1 of this thread is the exact size needed to straighten up the nose wheel.
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Re: Corked Nose Wheel

Post by smoss »

Thanks for the feedback Antoine. I suppose if it generally seems to work, I can always wrap it with some fiberglass tape to stiffen it up. I just like the quick and easy fabrication.
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Re: Corked Nose Wheel

Post by briankelly327 »

Purely a hypothetical for the aerodynamic engineer or test pilot - Ive wondered if there is a simpler solution of attaching two small metal straws taped on either side of the nosewheel at the back of the wheel pant, mounted vertically but tilted slightly back like the seats, such that they act like trim tabs pushing the nosewheel back in place when it gets corked out to one side.

My assumption here is that in cruise, the DA-40 flies nose down, causing the nosewheel pant to fly angled down. The nosewheel flies in the low pressure created by the nose gear strut, which blocks air over the top of the nosewheel. If the nosewheel drifts to either side by a little bit, it would graze the high speed air on either side causing it to get sucked out into the slip stream and stuck there until landing.

Like the straw tab solution above, I recall the rudder of the DA-42 has a similar T-shape trailing off the back. Aerodynamic engineers here can chime in on whether that T-shape on the DA-42 rudder is for stabilization, or to prevent flutter.

The risk here is that the straws could induce flutter if it catches enough air to push the nosewheel back through low pressure behind the strut and into the slip stream on the otherside, and then back again. Or it could be a simple hack just like the taping the air vents to reduce noise. Im not ready to try it tho
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Re: Corked Nose Wheel

Post by Pilot55 »

It has been a while since I have posted. I have the tooling finished for the newer model front wheel pant and will start producing the fins like the ones for the earlier pants I did a few years ago. I will update in a week or so when I have the fins stocked. Sorry this has taken so long to produce.
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Re: Corked Nose Wheel

Post by smoss »

Well it appears my quick fin production pictured above works. With the rudder trim tab still in place, the plane flew with the ball about half way to the left, as compared to all the way to the left when it flops the "wrong" way after a left crosswind takeoff, or centered in normal flight (wheel flopped to the right). With gentle left rudder pressure (to overcome the still present trim tab), the plane flew coordinated, and did appear to gain about 3-5 knots, although it was pretty bumpy, so hard to tell. Immediately after takeoff, prior to fin, I typically had a few seconds of nosewheel shimmy I would feel in the air. With the fin, I still felt the brief shimmy, but to a much lesser degree. After that, there was no appreciable shimmy, vibration, or adverse effects noticed. I took off the rudder trim tab after the flight, and will have to give it another go without it to see where the ball is, and if the nosewheel behaves again.
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Re: Corked Nose Wheel

Post by ZAV »

Just wanted to say my left leg is tired after a 3.5hr flight with the corked wheel. This seems like a silly problem to have. Do other aircraft types have similar issues?
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Re: Corked Nose Wheel

Post by Soareyes »

ZAV wrote: Sun Aug 02, 2020 1:44 am Just wanted to say my left leg is tired after a 3.5hr flight with the corked wheel. This seems like a silly problem to have. Do other aircraft types have similar issues?

Not only a DA40 problem:
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