landing gear springs

B

bobgoodman

New member
does anybody have the specs on the landing gear springs? i think i can get some from mcmaster carr if i knew the specs. i have some that might work left over from an old replica storch project, the weights are pretty similar. mine are totally shot having sat on them so long.

i read the post on making sure your gear will fall down, and one of mine wont quite make it. im going to take a closer look at it later today, but it swings pretty easy, i swear the hydraulic cylinder is the problem. or the gear valve. you have to hold the gear lever down a long time to even get the other one to lock.

i'll report back in after i mess with it some more. the manual pump will lock them both pretty quick. aand of course the engine pump has never failed yet, but i know it will. eventually
 
Are you talking about a smaller spring extension tube or a bigger one in the upper part of the gear strut itself ?
 
actually i should replace both. my struts are pretty flat, and i hear weak down pressure springs can lead to gear collapse, so that is bad too. i worked on my gear today and solved several problems but it was as usual, 2 steps forward and 1 step back. they worked perfectly on the jacks but when i let it down i got a gear unsafe light on the left gear. im pretty sure it's the switch but i didn't want to chance it. it was 4pm when i finished and about 100 degrees in the hangar so i quit for the day.

anyway, the right main will now fall and lock, but the left main is still sluggish. i really think its a hydraulic problem because if you take the cylinder loose it falls easily and locks. with the cylinder on, it wont lock but a couple of shots with the hand pump locks both. is that normal? could it be the valve not opening enough when you press the gear down pedal? the pedal will go all the way to the floor.

they old owner apparently believed that every bolt on an airplane should be as tight as you can get it.

maybe i'll have more gumption tomorrow. because tomorrow is another day.
 
Hi Bob… you have certainly been busy lately! There is a lot to learn about the entire landing gear system, but definitely worth the effort. Landing gear mishaps of various origins have been a big problem over the years. First of all, some standard terminology… “Taxi Springs” these are the large springs found inside the struts. They come into play, as the name implies, after the initial touchdown impact which is cushioned by hydraulic action. Generally it is recommended that they be replaced if their overall free length is less than 6” (some sources say 5-3/4”). “Kickdown Springs” are the smaller, but longer springs that maintain tension on the over-center position of the drag strut after the hydraulic pressure within the actuator bleeds off. They also become a secondary force of a gear freefall should the hydraulic system fail (the primary force being gravity). The Kickdown Springs are not particularly powerful because they do not need to be based on the mechanical advantage of the linkage once the gear is near the down and locked position. In my experience they seldom require replacement. The AAC factory does sell springs at a reasonable price.

Now let’s move on to the hydraulic system. Of course the hydraulic pump must be operational and capable of delivering 1000+ psi under load. The more complex component is the Electrol 750 powerpak. Most 14-19-2 Cruisemasters were fitted with the Electrol 750N model powerpak, however the fact that you have the first production -2 it appears you have the older Electrol 750B model (no doubt leftover from the previous 14-19 parts inventory). I’m not sure when in the build sequence the change was made to the newer model. I do not know much about the 750B model, only that there are few, if any, overhaul shops willing to work on this unit. Nonetheless the powerpak is basically a fancy hydraulic directional control valve system loaded with a bunch of o-rings. If the spool valves are leaking the effective pressure delivered to the gear actuators will be reduced – get a hydraulic pressure gauge and check for this.

Regarding the bolts holding the various strut components together none of them should be more than finger tight (or less in order to engage a cotter pin). You mention that the gear is not free to extend with the actuator attached. Is the powerpak gear lever in the down position when making this observation? If the gear level is in the neutral position the hydraulic circuit is locked. Also make sure the shaft is not bent to start with. Another very important point is to inspect the drag strut attach bracket for cracks – this is the bracket that is bolted to the rear spar. This is a known failure point guaranteed to cause serious damage. Keep asking questions and we will do the best to share our knowledge.
 
Bob.

Just a small addition to your words.
I do disagree with your opinion on kickdown springs.
Mine 14-19-2 came with 2 sets of gear legs and a bunch of wrecked one from ground loop.
So I had 3 sets of kickdown springs.
While assembling gear I've compared all of them. And the difference between most used and most fresh one was as much as 2" and this was REALLY noticeable on test extensions/retractions of the gear.
 
thanks guys. i think i'll go for replacing all the springs. even the little bitty ones that hold the cable for pulling the strut in when you retract the gear. ha ha. yes, ive been real busy, i was working on this thing for nearly 2 weeks in seattle, 16,18 hour days. I had a blast. I also had a blast flying it home. the weather sucked, so i flew virtually coast to coast at 2000 ft over the ground. or less. in a 60 year old airplane that hadn't flown in 40 years. i had a ball. the adventure of a lifetime.

the first takeoff wasn't as big an adrenaline kick as the first flight in my rv, but close. it wasn't a very long strip it came out of.

but so far, i love the plane. still lots of little stuff to fix, but that's what I do. I work on stuff.

bob
 
Since we are on the subject of hydraulic gear and my notebook is right in front of me, I will give the numbers for the O-rings in the retract cylinders (Bellanca part # 18500-20) for one cylinder 3 each AN 6227B-19, 1 each, AN 6227B-7, 1 each AN 6227B-10. They are available for a few dollars from Aircraft Spruce. Another point to inspect other than the drag link bracket, is the much small bracket that the hydraulic cylinders attach to. They seem to have a track record of cracking or complete failure. I believe that one of our members made a batch of them that were stronger than the originals. Glad to see you are enjoying your new plane. ___Grant.
 
Bob, you will come to know Grant as a source of great knowledge about the triple-tail beauties.
 
does anybody know the an number for the o-rings on the hydraulic dampener on the landing gear, mine are shot. but the springs are both 6 inches long.

they come apart real easy, took me about an hour to get them both off.

i've got like tons of literature on this plane, i'll be perusing my library to see if i can find it. this plane was owned for years by don vaughan, in seattle, and he had accumulated tons of information, but most of it is not technical.

bob
 
final word on landing gear. got it all back together with new springs and o-rings, i strayed from the published method of reassembly a bit by starting the dampener oleos into the outer tube before putting the tube into the upper housing so that i could be more careful about pinching the o-ring. i had to use an impact driver on the top nut to tighten it because obviously with the plinger already in the tube there was no way to keep it from spinning with a wrench, but the impact pulled it up fine.

looking back with hindsight on the hookup, i feel that the longer new oleo springs, working with the cable, really give the gear a boost downwards when the valve is opened, to make the gear swing down and lock better, which both do now. in fact, after i had it all done and the gear were hanging in limbo, already half way down, when i dumped the valve they both locked down immediately. its a very positive action and i feel it will work in the air. unfortunately, there is no way to test the 2nd emergency gear down with the engine running. the first emergency gear down method being the hand pump which also you can only test on jacks. on the viking, with the electric pump, you can test it, but not on my cruismaster. there is no way to turn off the hydraulic pump.

i have heard that you should stow a small wrench in the pocket behind the seat to release all hydraulic pressure if the pump fails but im interested if thats what you cruisemaster gurus do. i will mark the gear up side if i do that.

so i am am happy the the mechanism and with the amount of chrome showing on my struts.

big success. waiting for my pump to come back from qaa. no more boring landing gear posts from me. even the horn works.

wish i could go fly it somewhere today, but luckily i do have other planes to fly if i feel the need.

thanks for all the help.
 
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