Gear legs

[Panther16]

I converted to the TB gear legs at 80 hrs when I removed an aerovee and installed a 3300 Jab. At that time I had 1 bent gear leg. Now have 530 hrs and gear legs are still straight with both myself and my son flying the airplane. I did compare the weights and as I remember they weighed almost the same. The fact that the tubes are necked down between the engine Mount tubes may allow for for some flex in that area to absorb some of the load of a bounced landing. My bent titanium gear leg was straight above the lower engine Mount tube and straight below engine tube and bent at the base of the tube.
Of course it could be that I or my son has not had a bad landing in the 450 hours since the installation, said in jest.
Keith Rhode
Sonex 214KE

[Bryan Cotton]

Interesting - we have conflicting data.

[garyb]

I have the Tracy O'Brien gear legs on my A model Std Gear and with a very hard landing they held up well. They are cheaper than the Titanium lengths Sonex sell and they come complete with the axles.

[Area 51%]

Titanium would weigh about half of that (~2.2-2.4 lbs each).

Wow, for that weight penalty I don't understand why anyone would consider the TOB gear legs.

Edit: using the numbers above that is a 6.7 lb increase!

A 1 1/8in diameter rod of 2024 weighs 1.205lbs per foot according to Aircraft Spruce. Taildragger legs are nearly 3ft long. That alone puts the weight of the legs above the 2.4lbs if they were made of aluminum.
Don't know the weight per foot of titanium, but it is heavier than aluminum and lighter than steel. Split the difference and you get more that 4.5lbs for the titanium. Now we're talking about a little over a pound difference between the two. But wait....there's more.
The TOB leg already has the axle adapter welded on. Subtract that weight (or add the axle weight to the titanium) and we're talking a few ounces. Couple that with only having to drill one hole through the gear leg (which can be repaired if botched) and that the anti-torque plate has 4 bolt holes vs. the 1 on the axle for the titanium and I'll take the TOB legs every time.

As a side note: The TOB legs are indeed hollow and tapered. It's evident that there was more to the design of these legs than just chucking up a piece of pipe and whittling it down till it looked good.

Shining up my second set of TOB legs for the next Waiex here @Area 51%

[bvolcko38]

I,m not an engineer, but, wouldn't it be a good thing if the stock Sonex Ti gear legs had a little taper machined into them? Seems to me that if they had a bit of taper, then the bending would be distributed along the entire leg instead of concentrated at the motor mount gear socket. At a builder's workshop, Monnett said he" liked Ti because of its modulus."

[peter anson]

There are some pretty vague numbers floating around here so just checked the drawing. Standard gear legs are 34" long and 1 1/8" diameter. Using the density figure for 6AL4V from Matweb as 4.43g/cm3 I get a mass of 2.453 Kg or 5.4 pounds for the titanium gear legs. If the TOB legs are 5.7 pound it's not much of a weight penalty.

I would guess that the TOB legs are a thick wall tube so even if you bend them a little it would probably be possible to straighten them depending on how far they are bent.

Peter

[Bryan Cotton]

There are some pretty vague numbers floating around here so just checked the drawing. Standard gear legs are 34" long and 1 1/8" diameter. Using the density figure for 6AL4V from Matweb as 4.43g/cm3 I get a mass of 2.453 Kg or 5.4 pounds for the titanium gear legs. If the TOB legs are 5.7 pound it's not much of a weight penalty.
Peter

Thanks Peter, you beat me to it. Once you add in the axle mounts they are either closer in weight, or the TOB assemblies might be lighter - but they would be close. When I redo my alignment this winter I'll have to weigh an axle weldment - unless somebody in Sonex land has one not installed and can weigh it.

I am not planning to change out my gear legs, but it is interesting to do the trade studies.

[Waiex 0194]

Axle weldment, as received, each 468 g = 1.032 lbs

Titanium gear leg, as received, 34.125 long, each 2478 g = 5.463lbs

[Murray Parr]

I didn't know anything Tracy O'Brien was still available. Not much showing on his website. Is someone else producing them now?