New High Performance Landing Gear

[Antoine]

Charlie this is a well known fact: the problem ONLY occurs with the fairing installed.
The plane is faster without the fairing, despite the horribly "non aerodynamic" shape of the fork.

This story has been annoying us all for waaay too long. I want it fixed once and for all without depending upon some black magic that lasts 2-3 flight hours.

We're really close. The 3D print is being made these days. I can't wait to post photos of the "real" assembly!
Stay tuned - and thanks for your input.

Antoine

[Antoine]

Delivery of the 3D print is due next thursday.

Technical drawing of the full strut in 2D is completed and handed over to Roman for 3D modeling in SolidWorks. That was a lot of frustrating and tiring work.

NLG Strut dimensions.pdf

(23.94 KiB) Downloaded 135 times

I may be getting a bit over-optimistic here, but I am confident that the test of the new fork WITHOUT a fairing will confirm a nice performance gain. So I am pushing ahead with the design of the fairing set which should provide yet another performance boost.

I have hired a second engineer, Alex, a composites specialist. As soon as Roman delivers the 3D model, he will start working on a fairing set for the full NLG assembly, similar to the one found on Austrian-made planes.

[Antoine]

Here comes the strut ...

We have been delayed a bit because we made some dimensional checks (clearances) of the wheel / fork assembly. It looked OK so far but we have nevertheless implemented small changes that increased the radial clearance further. Easy enough at this stage!

I also found out that the Michelin tire I use is a bit larger in diameter than the Goodyear and a bit less wide. The new design will only support the Michelin/Beringer assembly, so if it ever makes it to certification it will cost another $ 500 for a drop-dead gorgeous nosewheel and tire!

[Antoine]

Here a render showing the difference between the factory fork and the new design. Notice the effort made to allow a more favorable fairing fit. The new part is also 1 lb lighter and 33% stronger - in SolidWorks.

We have now started the design of the fairing set (wheel and strut).

[Chris B]

Hi Antoine -

This effort is impressive! I hope that you are able to pull this off!

The new design will only support the Michelin/Beringer assembly, so if it ever makes it to certification it will cost another $ 500 for a drop-dead gorgeous nosewheel and tire!

Are these zippy tires repairable by most normal FBOs? IOW, by mechanics without expensive dedicated tire mount/dismount tools like automotive tire shops? I have no experience with tubeless aircraft tires, but only recall seeing them on jets.

Chris

[Antoine]

Thank you for the kind words Chris.

I am putting the resources behind this project to do it seriously from day one so that the (reverse) engineering work is re-usable down the road - certification will be a big challenge.

You comment about the serviceability of the tire is well noted.
Beringer deliver the thing pre-assembled and there are instructions for tyre replacement on their web site.
I will dig them out and post here for further investigation.

This said, the DA40 Tundra planes do operate in the Russian back country with Beringer wheels and Michelin tires, so there must be a way.

I like the Beringers and, unless we have a field issue, intend to use them in the MLG redesign too.
They are not only lighter, the brake system is more compact (disk inside the wheel rim). This is a very significant benefit when it comes to the resulting shape of the fairing.
And Beringer's anti-lock braking system is so much better, we will have a great side benefit from it.

[Antoine]

The printed part has finally arrived. See attached pic of the assembly.

Am I happy? Well no!
Granted, it is a big step forward, but there is still untapped potential. It is going back to the drawing board.

PS: how do you like the wheel?

[Antoine]

1. Tight clearances with the tire need to consider other than static dimensions of the tire. Tire dimensions grow in all dimensions (especially radius) as one climbs, the tire gets hot, and as the tire spins. It's also possible to pick up mud (on unimproved surfaces mostly). With the right/wrong type of mud I've had a front motorcycle tire gum up the space between the fender and the tire to where the tire would no longer turn. There is also some variation in tire dimensions with different brand/model tires.

Rich as promised, coming back with the action on this matter:

I have gone through a challenging (for my little brain at least) comprehension and math exercise courtesy of THE 2013 TIRE AND RIM ASSOCIATION AIRCRAFT YEARBOOK.

It turns out that the clearances required by the growth and deformation of the tire are quite small.
The clearance requirements we have set are significantly larger - in case the test plane picks up a rock or something.

[Rich]

1. Tight clearances with the tire need to consider other than static dimensions of the tire. Tire dimensions grow in all dimensions (especially radius) as one climbs, the tire gets hot, and as the tire spins. It's also possible to pick up mud (on unimproved surfaces mostly). With the right/wrong type of mud I've had a front motorcycle tire gum up the space between the fender and the tire to where the tire would no longer turn. There is also some variation in tire dimensions with different brand/model tires.

Rich as promised, coming back with the action on this matter:

I have gone through a challenging (for my little brain at least) comprehension and math exercise courtesy of THE 2013 TIRE AND RIM ASSOCIATION AIRCRAFT YEARBOOK.

It turns out that the clearances required by the growth and deformation of the tire are quite small.
The clearance requirements we have set are significantly larger - in case the test plane picks up a rock or something.

The picture you posted makes that look like plenty of clearance. The thing that concerned me was from the top view drawing, it looked like zero clearance.

[Antoine]

I understand, Rich!
My concern was on the lateral clearance, which is difficult to perceive on this pic.
But even there we are fine - say the calculations.

The picture above actually highlights the reason why we will rework it. The shape is still far from the tight fit that is our goal. It looked OK in drawings and was already so much more compact than the original assembly that I made the mistake of not pushing for even more streamlining.

.. but when you see the real part, you can imagine how big the bulge in the fairing will be. Those "elbows" where the attachment point of the tow bar is located have to go.

So this 3D print, while expensive, saved a multiple of its cost in CNC machining...
Stay tuned. Version 2 is in the works