More landing gear springs

Ralph925

Ralph925

New member
It is annual time for my 14-19-2 Cruisemaster.

Thinking I had all the information I needed, I opened up my gear legs to replace the sagging gear springs and found a surprise. The two sides are assembled differently, and one side has a spacer that the other side does not. It looks to me like the one on the left is correct and the “tulip” on the right is upside down and missing a spacer. Does anybody have a drawing of the assembly?
Any comments on the correct assembly would be helpful.

 
Hi Ralph... let me offer my comments. First of all the orientation of the welded spacer (I think you called this the tulip) is with the flat side towards the spring, as shown in the left view of your picture. Now, regarding the cylindrical spacer, this is not a standard part of the assembly - I have not seen this on any of my main gear units. So why would it be there? I can think of only two reasons... first as a temporary solution to a spring that is too short - maybe the only available spring was undersized. The only other reason I can think of is that the step on the ID of the lower strut has been counterbored too deep and the spacer makes up for this. Check and make sure that the strut length and the counterbore depth are the same for both the left and right side gear. This feature is not well illustrated in any of the documentation that I have seen but when you look at the inside bore of the lower strut you will see this shelf. The attached picture is actually a document from Bellanca showing the stackup. I think I have a better drawing somewhere. Also I have attached a picture of one of my oleo pistons - no cylindrical spacer. --Rob
 
Thanks so much Rob. Checking the c’bore depth is a great idea. My guess was the spacer was a “field expedient” to fix a sagged spring. Then the other side was assembled incorrectly at a different time. Over its long life this aircraft has had a mix of very nice, and kind of sketchy maintenance. I am trying hard to only do the better thing.
 
I was at a eaa pancake breakfast the other day, and the bellanca attracted the usual crowd. One of the guys looking at it had owned one in the past (who hasn't, they must have made thousands of these things), and when we discussed the gear springs he said that bellanca used the same springs on the cruisemaster they used on the lighter cruisair. He said he got the specs and ordered replacements made that were stouter and they worked great. he said he thought he had some laying around and is going to check to see if he can find either the springs or their specs. if i find out anything i will post it here. interesting, i thought. i'm sure mcmaster has some that would be in the right range.

the only problem is if you crashed and the ntsb got wind that there were non-tso'd springs on it they would probably send you to leavenworth for life, assuming you survived. or worse, maybe put a black mark on your permanent record.

my springs are ok so far, but the handwriting is on the wall. maybe another year or 2 i'll need some. they were at one time in their life pretty short, but i think somebody might have put them in a press and stretched them back out. but bottom line, they are not strong enough for the weight. only my unbroken string of perfect landings has preserved them so far.

does the 14-19-3 use the same springs? of course with the tri gear, there is less weight on the mains, so they probably work fine.

i didn't eat any pancakes, i'm off the carbs, but i ate lots of bacon and sausage.


bobg
 
Designing a spring that will run lots of cycles without fatigue is more complex than it looks at first blush. Simply making the spring “heavier” will usually make the problem worse. To keep the extreme stress and the change in stress under control the spring needs to get longer or larger in diameter, hard to do in an existing design. Using a spring in the existing space that has thicker wire or fewer coils will be stiffer but the stress in the spring wire will go up and the life of the spring will be shorter.

The real problem is not the landings, it is the long taxi back to the runway, in the rough grass, now overloaded after that monster meal provided by the fine dining establishment at the local airport. :shock:
 
I just replaced my main gear springs due to sagging.
I called Alexandria and they actually had a set of main springs in stock. They were reasonably priced.
Might give them a shout.

Also, there shouldn't be a spacer ring. That seems jerry rigged.
-Adam
 
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