Author Topic: Landing gear, springs, wheels etc  (Read 1601 times)

Offline lacazet2k

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Landing gear, springs, wheels etc
« on: February 19, 2020, 02:26:53 AM »
Attached are pics of the landing gear for my cabin mod of the XL. There is a shot of the AS Raymond stock 90 durometer .75 in urethane spring. Five or six of these, with 5 .020 alum spacer twix, in series yields 800 to 1000 lb per inch.  five springs weigh .25 oz. In the range of the speced steel spring eh? To facilitate changing the preload I slotted the lower tube for an AN3 bolt. Slotting allows changes to the spring length and preload without grinding and rewelding. You slotted the upper end of the tube, that was fun, why not the bottom. To evaluate the spring rate and preload I computed the tube loads in my finite element model and these are shown on a PDF file of the gear area of the model with the forces and moments added in red from the analysis. I ran the computation at 100 lb vertical load but the results scale linearly. I did not add the stresses as my axle is a .75 X .090 to accommodate a Tuff 16 inch wheel and Avid brake. The total weight of the gear, wheels, springs, brakes is 11 lb. If cooler heads see danger lurking in all this foolishness please shout out very loud! And yes this cabin mod will finish out at 254 lb

Offline Vince Carucci

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Re: Landing gear, springs, wheels etc
« Reply #1 on: February 19, 2020, 05:57:34 AM »
Try again with the attachments. I'd like to see the work.

I also ran the numbers for springs. The flying weight of me and the aircraft will be 480 lb.-ish. So with the geometry of the bicycle landing gear, each spring will be under 345 lbs. compression just sitting on the ground with me in the seat. I bought some springs rated 1,000 lb/in. So I should have suspension for a 3-G masher into the sod. I wonder if anyone can say how many G's a typical landing experiences. 

Vince

Offline Dan_

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Re: Landing gear, springs, wheels etc
« Reply #2 on: February 19, 2020, 03:11:46 PM »
 I bought some springs rated 1,000 lb/in. So I should have suspension for a 3-G masher into the sod. I wonder if anyone can say how many G's a typical landing experiences.

Vince
The short answer is between 1G, a perfect greaser landing and 2.1G a "firm" (hard?) landing. 

A 30 degree banked turn is 1.15G.  15 percent over what you experience in front of the TV in your easy chair.

I would be inclined to believe a 3G "arrival" is going to tend to bend or even break things on the XL.

The long answer is here:
https://thepointsguy.com/news/hard-airplane-landings/




“A superior pilot uses his superior judgment to avoid situations which require the use of his superior skills.”

– Frank Borman, Apollo 8 Commander

Offline scottiniowa

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Re: Landing gear, springs, wheels etc
« Reply #3 on: February 20, 2020, 04:27:53 AM »
Attached are pics of the landing gear for my cabin mod of the XL. There is a shot of the AS Raymond stock 90 durometer .75 in urethane spring. 
No attachments were at hand, that I could see.
 
Dan had interesting numbers that probably are spot on for strait in landings.  A couple of things to note, but most of you would never do, :D and that is a side wind landing.  Simply said, you come in and for some reason at the last second, the wind gets under the up wind side.  We all know how to correct, but it is that split second before correction is made, that we need to be concerned with the "side load g force"

Lets say we have everything calculated just right for the gear, but the wheel can handle only 1/2 of what the gear can, then it if it has a grippy tire, may well be the first to go.  This can be said about any "weak point"   Don't get me wrong, I am not saying the gear has to be made to handle anything you give it, but rather, if you have everything working together and have one little part of it that is way under the task at hand, it will/could be the deciding factor.

There have been many craft that had 2.3g A frame gear but the shock strut (parts)  could only handle .8g in side load at which point the 2.3 part really don't matter much for that split second when we are correcting for wind under the wing. Parts working in harmony have always been better.  Tires-wheels-A frames-shock struts-attach points-bolts   :grin:
best email address:  irondesignairparts@gmail.com

Offline Suomelainen

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Re: Landing gear, springs, wheels etc
« Reply #4 on: April 26, 2021, 12:39:25 PM »
I've looked high and low in all the wrong places and still can't find any springs for my LEXL. Where in tarnation you folks finding springs for your birds?

Offline Vince Carucci

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Re: Landing gear, springs, wheels etc
« Reply #5 on: April 26, 2021, 01:57:35 PM »
I've bought new springs (since my previous post). Visit McMaster-Carr and have a look at PN. 9573K81. Less than $9 each.

Vince

Offline Suomelainen

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Re: Landing gear, springs, wheels etc
« Reply #6 on: April 26, 2021, 05:59:33 PM »
Thanks Vince. That’s awesome.

Offline leshoman

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Re: Landing gear, springs, wheels etc
« Reply #7 on: April 28, 2021, 09:22:57 AM »
Check out Fastenal, they have springs in the range we need for the Legal Eagle also.
Les Homan

Offline Chuck in Indiana

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Re: Landing gear, springs, wheels etc
« Reply #8 on: May 04, 2021, 04:29:01 AM »
I've bought new springs (since my previous post). Visit McMaster-Carr and have a look at PN. 9573K81. Less than $9 each.

Vince
This is the above spring..

 

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