New Landing gear brakes.

 Hello to all the readers of Kitplanes magazine!!   I was fortunate to meet Dean Sigler at the 2012 Experimental Soaring Associations  Western Conference in Tehachapi California. It was sure great meeting and seeing everyone over the Labor Day week end. From the emails I have received I see that the January edition has already made it to the subscribers base.

The first thing I realized when we went to the airport for the initial Taxi test, is that  I need brakes!!!! For the initial flight my buddy Ed was going to keep me from rolling into other planes and hangers, but in reality that's not really practical.
 With this new Grove spring gear, it quickly became apparent that I was going to have a axle bending problem. The axle is a 4130 steel tube 3/4" x .125" wall. I do not want to heat treat the axle, so I am using the 4130 in the normalized condition. That limits the stress to about 95 ksi in tension and 74 ksi in compression. The old landing gear design tucked up inside the hub and limited the bending moment because the point of load application was only 1.75" The new spring gear increases the cantilever distance to 3.57", That distance by the way is the point the axle is cantilevered to the point of load application which is the center of the hub. When brakes are added the distance increases by another inch.  The gear will almost bend now just sitting on the ground!!! To solve this problem I decided to make a sleeve collar that is 1.24" in diameter at the point of greatest moment. this will limit the bending in the axle back to the original design stress.  I bought some 3.5" diameter 7075-T6 round stock and proceeded to make a ton of chips.

Sleeve collar being turned

Here is the beginning of the Sleeve hub being turned on my Lathe.
This is my faithful 36" Grizzly Bench lathe. I've had this lathe for 20 years, and believe it or not I have moved this lathe all over the country chasing the latest and greatest aircraft design contract!! I'm getting too old for that stuff these days however!!

 This gear design is not only way too heavy, its also too damn expensive. As you can see in the next picture, 8 hours of my life was spent standing in front of my lathe!!
  

Chips and turnings

I filled that trash can 5 times!!
I have decided that the final design will be offered in two options, thanks in large part to all of the letters I have received.  I will offer the original retractable mono wheel as well as an  option  Taylorcraft style internal bungee landing gear.

sleeve collar and axle

This shows the outside of the sleeve collar, the part not shown is a flange that mates to the gear leg. In this picture its very apparent how far the axle would have had to extend. The inside face of the wheel bearing rides on the outboard face of the sleeve. The flange of the sleeve is bolted to the gear with 4 .25" dia bolts. The brakes that I finally adapted are from Azuza manufacturing. I purchased them online from Go Kart Galaxy
http://www.gokartgalaxy.com/

ask for Clint. These brakes are mechanically actuated so I ordered all of the cable , cable ends and fittings. I have plenty of excess cable that I think I can route the cable  to the actual rudder pedals. That will be the subject of the next blog entry.because I haven't designed them yet!!!

inside view of gear leg

The 3/4"l axle is welded to a 1/8" steel plate that is bolted to the inside face of the gear. I had to grind out a small recess at the very bottom of the gear to clear the actuation lever. I also had to flatten the lever and remove the 1/4" offset. The flange of the sleeve is also shown in this view.






  

Cable anchor bracket.

I added a bracket to attach the adjustable cable anchor. All in all this turned out to be a really clean installation. The cable will route along the trailing edge of the gear and will be attached to it with heavy duty nylon tie wraps

Drilling the axle hole

If you were wondering how I was able to accurately drill the 3/4" axle hole, this is how I did it.