XL Landing Gear

[914pete]

I was going to reply to a post from 2015 but got a pop up to consider starting a new thread. 

I've tacked together my gear to a height of 17.5" center of axle to center of the bottom bracket/tube attach point as shown on page 22 of the XL plans.  I am using the BlackMax BX1000 wheels, tires, brakes etc.  I plan on purchasing the 1/2VW 37hp engine.  Will I have enough ground clearance for the prop?  Or should I have built the gear to the 21.25" height as mentioned in the gear thread from 2015?  Another member mentioned the height difference between the 20"BMX wheels and the BlackMax wheels resulting in a difference of 3.75" however, Leonard mentions in my plans that everything is geared to using the BlackMax wheels so I followed the plans.  The general consensus from previous threads seems to be to build the gear somewhat to your landing preference.  I have no tail wheel experience.

Also, while searching threads I've seen 0 camber, 2 degrees, 3 degrees.....Any suggestions on wheel camber for an XL, 37HP 1/2VW 170 pound pilot?  I haven't cut my shock struts to length yet.

[Dan_]

Here is what one builder did: http://www.angoraaffaire.com/leu/id48.htm


Your goal is to have the plane loaded at gross weight with the tires almost vertical, and perhaps 1/8" closer together in front than in the back.  (toe in)



The empty plane will sit with positive camber.  (The tops of the tires are farther apart than the contact patch)  


It is said that upon landing, the spring rebound is damped from the tires scrubbing as the camber goes from positive camber toward 0 or negative.  (depending on how hard you landed I suppose)

Interesting use of "grease plates" to allow the gear to align itself at different loads...

If you are a current accomplished pilot otherwise, the taildragger transition is not that big a chunk of gristle to chew...  (plenty of help out there that you will want to avail yourself of)  If not, it is going to be one more thing in the long list of distractions that put you behind the plane at the worst possible moment.

Hopefully someone will comment with better particulars to your situation.

[914pete]

One mention of extending the gear 4" from the old web pages using 12" tractor style tires.  Hmm.  Anyone using the BlackMax set up that went with the 17.5" dimension from page 22?

[Tom XL-7]

I have a red handwritten note on page 22 to use 22.5 inches. The note came from another builder and could have been spoken in person.
but let me assume some numbers as I have nothing here to measure and I'll put together an example.
Assumptions only: always equals danger
 
Your crankshaft sits 7" above the bottom of the firewall. Your blackmax tire and wheel are 16". 54" prop

7+4.5+17.5+8= 37"
a 54" prop yields a radius of 27"
10" clear   6" is probably good 
A flat tire gives you 5"
 
Where am I thinking wrong
prop size, crankshaft height, Bad logic or addition?
Tom XL-7

[PropMan]

Hey Pete,
Just took some measurements on my XL. Keep in mind i will be turning a 67" diameter prop but the dimensions should be helpful.

My gear is 19.75" instead of the 17.5.
The black max wheels with 15x6 Carlisle turf tires are 13" tall.
Currently i have a 62" diameter prop installed and with fuselage in level condition, ground to tip clearance is  9.75"(FAA recommends 9"), My engine is a bit above center line tho.

Bottom of sta1 to floor is 32", add 6 inches gives you center to floor of 38", less 9" for tip clearance and you have room for a 58" prop, if you use the 17.5 gear you still have room for a 54" prop and 9" clearance.

Hope this helps

Also, I typically make a 54x22 prop for the 37HP half.