Landing gear springs

[Rich Snyder]

I have decided to go with springs for my landing gear after about 70% of the group polled, replied for using them. Also The Boss says to do it; so who am I to argue?
The plans say to Tack weld (the bottom spool) to  3/4" tube to adjust spring. What exactly is the adjustment? Is it just snug for no spring rattle or are we talkin' a bit of compression of the spring? Rich.

[rockiedog2]

most all these guys say to "preload" the sprang. I never have done that. I just adjust the length of the shock strut so it compresses the spring a little and the wheels it right when it's loaded. maybe thats the same thing. i never did figure out how to compress one of those stout little springs w/o risking losing a few teeth

[weasel]

I don't have the plans in front of me right here but you have a slot in the larger tube for the travel in the suspension.  If you just butt the socket up to the spring with NO pre loading. You will loose part of your travel (slot) when you start loading the airplane.  If you can pre-load the spring (compress) it some you will not be setting so far down the slot when the plane is loaded.  Ideal would be to load the plane on the ground with the pilot setting still and still be at the top of the suspension slot so that any bump or hard landing can utilize the maximum amount of spring without bottoming out.

Hope this helps some.

[Rich Snyder]

Thanks guys ; that does help a lot. I'm thinking about 1/4" of compression but will refer to the spring specs for pound per inch of compression and do the usual guesstimate engineering. My weight plus the mighty VW = oh.... about that much. Rich.

[riorex2002]

Don't forget to add the O S---t landing load  into the equation

[weasel]

Don't forget to add the O S---t landing load  into the equation

Don't figure that in.  Thats what the slot is for and also why you want as much slot available as possible.

[Tom H]

Some may never understand it, but Weasel has it right.  Save the slot length for landing.

[Will Weidner]

Hello, I'm new here.  This is my first post, although I've been learning a lot from listening (lurking?) to the old hands and new folks like myself for a while now.  My son and I are building XL-D-43.  I want to add how much I appreciate Leonard's designs.  I think these are the best ultralights out there, but I'm biased towards old technology.

I thought I'd chime in on this landing gear business.  I am planning to use the 20" Tuff wheels with compression springs.  The design I've laid out puts the plane at the same height from the ground as the Black Max wheels.  With this configuration, I end up with a strut force of 16/8.5 = 1.88 times the weight on the wheel.  So if there is 225 lbs. on each wheel, the strut force will be 425 lbs.  If you pick a spring with a 528 lb/inch spring rate, you would need to have the spring compressed 425 lb./528 lb./inch = .804 inch when the bolt is at the top of the slot.

The spring Leonard called out, 14714, has (I believe) a 528 lb./inch spring rate, and I recall he mentioned on a post some where that he preloads it 9/16", which is pretty close to the number I came up with.  I think anyone using 20" wheels is going to have a similar geometry to what I came up with.  I hope this helps, and doesn't muddy the waters any more than they are.

[Rich Snyder]

Great information from all. This is a  "copy and put in my plans"  page. Rich.

[Tom H]

Started the annual inspection on Stubby yesterday and looked at the gear strut springs.  I believe they may have lost a bit of strength or have been slightly compressed after too many hard landings.  I originally built in some preload so that the bolt was at the end of the slot when the airplane was sitting on the ground empty.  Now I notice that the bolt is positioned a half inch or so in the slot.

I built in an adjustment capability to preload the spring, and may have to change it some. 

I've attached a pic to show the parts of the spring section, including the adjustable "hat" for one end of the spring.  The adjust-ability is accomplished by selecting one of the three pairs of holes in one of the hats.  Note the hat at the other end of the spring is welded to one of the strut tubes, so it has no holes.

Spring preload adjustability may be useful in the future, no matter how you do it.

[rockiedog2]

I thank you guys are way overthinking this preload business. I didn't put any in mine and yeah the crossbolt rides down in the slot a little and you can't tell the diff. 143 had no telling how many off field rough ground landings and never had a problem except the few times the gear got all bent up but that wasn't the fault of the preload. The crossbolt in mine was a 3/16 and at 250 hours when I changed to the leaf gear that little bolt wasn't marked in the least.
But if I wanted preload I would sure put it in it. Why not, right?