LANDING GEAR STRUTS #2

STRUT STUFF...(010401)
Subj: Servicing ELI struts
From: Sam Swift <Flyboycpa@aol.com>
I have a question about servicing the struts on 3760K. I have the ELI (air/oil) and am pretty clueless about what to do to service them. Upon each landing and subsequent taxi back to the hangar, both struts have compressed with about 1.5 to 2 inches of chrome showing. At the end of each flight, I lift both wings back up to bring the struts "up" while the plane is hangared. My question is this--how do I go about adding air or oil (or both) to the struts to get them where they ought to be and how do I know which, if either, needs to be added the most and in what quantities. Additionally, is it just regular air or nitrogen?? Thanks for the help, Sam Swift 3760K

Sam
I would suggest just adding nitrogen until the struts are extended to about 3 or 3 1/2 inches. The book says 3 3/4" at GW. You will be guessing that the person who last added 5606 got it right. If you ever have occasion to remove the landing gear from the airplane you can fill them with fluid, then air them when reinstalled. The book procedure is kind of screwy, but I just filled them up with fluid with the strut flat. Adding air or nitrogen is somewhat difficult because the air is on top of the fluid. Nitrogen is preferred, but a strut pump will work too. I used to have an inline reservoir which I would fill with 5606 and blow in fluid and air together. Caution - if you try something like this, be sure the reservoir won't explode with several hundred pounds of air pressure, and get it out of there before you air up the strut. I think your struts are not too far off. If they never bottom out, perhaps just leave them the way they are. I would guess your ride on the ground is pretty good! -- Jim

ELI LANDING GEAR PRESSURES... (010501)
Subj: Struts
From: Ron Williamson <rwwilliamson@earthlink.net>
Monty, I did see the question that Sam Swift asked about ELI gear, and I'd like to add my opinion. I also have the ELI gear. I've been using 160 psi as the nitrogen pressure when the gear leg is fully extended. I fill the strut per the instructions and then put in the plug. I start the nitrogen using a 2000 psi bottle and regulator set at 160 psi. As the pressure builds up, I put a jack under the jackpoint to let the strut extend fully under the pressure. Then, shut off the nitrogen, disconnect and let the jack down. The strut then collapses down to the desired setting. I've never been able to get the gear to set properly by just increasing the pressure until it gets to the desired 3 inches or so. My gear always sticks a little when it's just sitting still. When cranking the pressure up to 250psi or more to get it to the right level, it's way easy to overpressure and then it's extended too much. As you know, there's no graceful way to release the pressure since the Schrader valve is below the fluid level! When moving, with some vibration, it works normally and gives the nice cushy ride. I'm sure it's simple to calculate the amount of strut compression using Boyle's Gas Laws, the internal volume of the strut at full extension, the cross sectional area of the strut, the weight on the gear and the ambient temperature, but, I'm an electrical engineer so I took the experimental approach. The analytical method is left to the more academic among us. -- Ron

AD 58-10-03 CONCERNS... (010501)
Subj: GC-1B (AD)
From: Michael Ward <Michael.Ward6@PSS.Boeing.com>
Jim, Looking over a 1946 Swift to purchase and came across a potential problem. 58-10-03 is an AD that checks the clearance between the gear strut and the side brace over-extention external stop. Apparently if the internal stop is in its proper place the external stop will have a clearance of 1/32"-1/8". The Swift in question has no clearance on either strut and the logs say that all AD's have been complied with. The AD states that it covers all Swifts with "Adel aluminum forged torque knees". The struts on this Swift are Adel, but they are the Air-Oil not the spring oil. I do not now if the air-oil has the aluminum forged torque knees that the AD is covering. After reading some earlier posts concerning struts, I geuss my question now is weather or not I am dealing with the Adel or ELI strut. How do you tell them apart if the I.D. tag is no longer legible? Any help is appreciated. Regards, Michael Ward

Michael, I'm puzzled, all Adel struts are spring-oil. The aluminum scissors (torque knees) will physically fit on an ELI gear, but they are not legal. All that holds the fork to the ELI gear is the torque link. (and brake hose!) If the torque link breaks, you just lost the lower part of the gear. The steel ELI torque link has never been known to break. Put a magnet on the torque link and determine if it is steel.You should enlist the help of an experienced Swift mechanic. Can you send me a .jpg picture of the gear? If in fact it is an Adel gear, a positive check of the internal stop is to remove the external stop completely. Then if the internal stop ring is broken the scisssors will extend almost vertically. The ELI has a Shrader valve valve in the fork. The Adel has a filler on the side of the strut, a 1/4" pipe plug. The Adel has the aluminum scissors. (torque link) The Adel has a chrome strut diameter of a little less than 2". The ELI strut diameter is over 2". Compare to the parts catalogue. You should not consider buying a Swift without having a knowlegeable Swift mechanic look at it. -- Jim

ADEL LANDING GEAR STRUTS... (020201)
Subj: Adel Struts
From: Bob Webster <bob-jewell@wk.net>
Hi Jim, I just thought I would throw in a side note on Michael Ward's question on the air in the Adel struts. This is the long way around but Charlie Cummins got this on the advice of Bill Commings on putting air in the Adels. You pull the plug on top and put in a Schrader (sp) valve, after the normal servicing of hydraulic juice. Then you give it a shot of air from 40 to 60 psi. Charlie said that he had a buddy that was an engineer who attempted to explain it in engineer talk to no avail. The guy sold him to forget about the details and just do it. It somehow affects the spring rate when it is done. Also, and again this doesn't make sense, but it makes the gear softer when encountering Mom Earth. I do it on my bird and I can tell the difference as does Charlie in Booger. He also says it helps on birds with tired springs and gives them a slightly new lease on life. So in the long run Michael isn't far off. You make it an air-oil-spring gear. Works good, lasts a long time. Keep up the good work. Bob Webster

Bob, Yes, I do the same thing but I did not want to complicate the answer to Michael's question. As it turns out, the airplane has ELI gear. -- Jim

LEFT STRUT PROBLEM ON ELI LANDING GEAR...(030401)
Subj: ELI Gear
From: Michael Ward <millerk@gte.net>
Monty,
I recently bought N3773K and I am having a little problem with the left strut. After landing on roll out I applied brakes firmly to make the first intersection. Just at the end of the braking my left strut compressed completely. On previous postflights I have noticed some leakage from the strut, but the 3.75" measurement was never degraded. There is no damage that I can see, but I imagine that the seal is most likely blown out. My main question is to ask for the part number of the lower seals on the ELI struts since the service information that came with 73K only had info about the Adel gear. Also I have noticed that the fluid that was leaking was not red. Was there another hydraulic fluid other than 5606 that was used in ELI gear? Regards, Michael Ward

Michael,
The seals are available from Swift Parts. It is just a simple AN6227-35 "O" ring in the ELI gear. I used to have ELI gear on a previous Swift that I owned. I had the same thing happen to me once. Since all the air was gone from the strut, I removed the scissors (on jacks of course) and removed the strut and fork assembly. The "O" ring had gotten dry and rolled, allowing the air to escape. I lubed up the "O" ring with Vaseline and refilled the strut with 5606 and aired it up. I never had to service that gear again! Of course, the proper thing would be to replace the "O" ring. Old 5606 sometimes has a yellow appearance, but someone may have used regular engine oil or jack oil in your struts. There is no good reason for this, as 5606 is not much more expensive than engine oil and it may be cheaper than hydraulic jack oil. --  Jim

HYDRAULIC FLUID LEAK... (040101)
I have a trickle of hyd fluid which comes out of the "set screw" in the gear leg (screw holds the bronze sleeve in place). I had correctly installed the soft aluminum washer when I overhauled the gear leg. Question is -- can I remove this "set screw" so I can apply a bit of sealant? With the gear up on jacks, if I remove the "set screw" can the bronze sleeve move? Steve

Steve: The sleeve can't go down, there is a snap ring below it. I doubt if it could go up by itself, although there is really nothing holding it in place with that set screw out. (gravity and friction?) Just pull the set screw out and seal it with something that is impervious to 5606. -- Jim

SCHRADER VALVE ON ADEL LANDING GEAR... (040201)
Subj: Adel landing gear
From: Geroge Rodda <garodda@compuserve.com>
Jim;
Recently there was an article about adding a schrader valve on the adel landing gear strut so that it could be pressurized. If I misunderstood the article, please let me know as I 'm getting ready to install new struts and bushings on our plane. If this is a worthwhile procedure, please advise me. Thanks, George Rodda N3244K

George
That is a worthwhile idea. You can buy 1/8" pipe air valves in any hardware store for 2 or 3 bucks ea. If your struts are tight, they will retain air. Some guys only use 20 psi. If the springs are weak, you can use 100 psi or more. My right gear never has held air for more than a few days, there is too much clearance between the brass sleeve and the chrome cylinder. There is not much volume in the Adel - so any leakage will be noticeable immediately. The Adel "O" ring is a little small so it might be a good idea to cut a deeper groove and install a thicker "O" ring, but don't do something like this unless you understand what you're doing. -- Jim

BUT WHAT ABOUT A CLUNKING SOUND??? (050201)
Subj: Clunk, Clunk
From: edlloydaustin@juno.com (Ed A. Lloyd)

Jim, I've been meaning to ask this for some time and keep forgetting it. When I taxi my Swift on a grass strip that's a little bumpy, there is a noise from one or both main gear at various times. We have discussed it around the hangar and I'm told it is the tail wheel strut. I know when the tail strut makes a noise and it's easy to tell the tail strut from the main gear. When the main gear strut is fully extended, and the scissors stop block has the required clearance, does the silver soldered ring on top of the chrome part of the strut come in contact with the top of the main bushing in the strut? If it does, then this explains the noise I hear. I have flown Duane Golding's Swift and it has the same noise as mine. When I was towing Dorothy's "New Swift" today, her gear is making the same noise. Please try and settle this "discussion" item for me. Cheers.......Ed

Ed,
That internal stop ring is probably what you're hearing. Is it any wonder those rings break off occasionally? -- Jim

CLUNK, CLUNK, PART II...(050201)
Subj: Clunk, Clunk
From: edlloydaustin@juno.com (Ed A. Lloyd)
Thanks Jim, you confirmed my suspicions. What would be wrong with putting an 'O' ring or a Quad ring around the chrome portion of the strut, at the top, to absorb the shock and stop the noise. That way there would be no metal to metal 'clunking' and it should act to absorb some of the shock on the upper stop ring. Cheers..........Ed

Ed
An "O" ring would probably not last too long, then you would have rubber fragments in the strut. Maybe a teflon ring?? I will give it some thought. -- Jim

ELI STRUT INFLATION... (060401)
Subj: ELI Strut Inflation
From: Michael.Ward6@PSS.Boeing.com (Ward, Michael B)
Jim,

Recently replaced seals common to the ELI struts on N3773K. Ever since, I have been trying to figure out the right formula for proper chrome extension (ie.3.75"). I have tried several way, but all have been hit or miss and I would like to have a system that works "every time". The one thing I have not done is to have the tail up on a stand when inflating the struts. Maybe this is what's causing the inaccuracies. Let me know if you have any tricks up your sleeve. Regards, Michael Ward

Michael
I must confess when I had a Swift with ELI gear I often used a hit or miss method. Usually, once I got it right, it lasted for years so I didn't worry about it too much. If you get the struts overinflated you can let a little air (nitrogen) out and get a face full of 5606. (cover the Schrader valve with a rag) There are several "tricks" -- lube the struts up with Vaseline so the "O" rings slide more freely on the strut. Put jacks in place and jack to full strut extension. Then adjust the nitrogen regulator to a set value, say 250 pounds. Then remove the jacks. If you need more strut extension, repeat, only use more pressure. (the value varies with individual setups) Once you get a pressure value that works for you can repeat the procedure. -- Jim

STRUT LEAK STOP IDEA... (090201)
Subject: Re: Leaking Strut
From: Phil Howell <POPPAPOU@aol.com>
Jim,
Regarding the note from Mile Whitt concerning the leaking LG strut, I had a similar problem on my left ELI strut. I fixed mine as follows: Extend the strut and carefully drain the fluid and air from the strut via the scrader valve. Mix up a solution of 2oz (by volume) of Flocked Cotton Fiber and hydraulic fluid, pump the mixture into the strut. Continue to refill the strut with the proper amount of fluid and air. Over time the fibers will settle to the bottom of the strut (they sink in hyd. fluid) and slowly fill the cracks. This worked great for mine and the cotton fibers "should not" harm the rest of the system. The fibers are available from Aircraft Spruce, Ph 877-477-7823, P.N. 01-14800, 1 lb. $1.95. The fibers are used as a thickening agent in epoxy. It goes without saying, "use this advice at your own risk!" Phil N3313K

Thanks, Phil -- I had not heard of that problem with an ELI strut. Usually, it's the recent production Adel struts that have that problem. -- Jim

STRUT LEAK STOP IDEA #2... (090201)
From: Rick Stroud <Rick.Stroud@tbe.com>
Subject: Landing Gear Strut Leak
I had a the same problem with N78280, the strut leaked by the bottom plug. We (Jim Thomason, my long suffering mechanic) solved the problem by removing the landing gear and taking it apart. Cleaned the strut inside to remove any oil. We then poured slow drying epoxy into the strut (enough to cover the entire plug at the bottom. We then cut a valve out of an old tire and clamped the whole thing in a press. We put about 80 psi of air in the strut while the epoxy cured - we left it overnight. That was about 5 years ago and no leak so far. Simple and lots less expensive than a new strut. Hope it helps, Rick Stroud

STRUT LEAK STOP IDEA #3... (090201)
Subj: Gear Strut Leaks
From: Jim <jimlinda@spacestar.net>
Hi Jim,
I saw the posting on the strut leak and thought I would pass along my experience with the problem to date. I have had one that leaked since new. I tried to clean the outside and add epoxy to the bottom of the cup around the edge of the cup to stop it from the outside, it worked for a week. Then I took the strut out, called Loc-tite and found that a green Loc-tite might work. I cleaned it out and washed it with everything known that will cut the 5606 and then poured the Loc-tite into the strut. It set-up so fast that I wasn't sure that it could have penetrated the leak area. It didn't at first and then after a month it quit leaking and stayed that way for a couple of years. Now it's leaking again. I'm of the belief that there are only two ways to fix it. One, replace it with a new correctly made one. Two, find someone that can work miracles with silver solder and remove the plug, clean it and replace it with the proper process. The second choice is to risky in my opinion on a finished strut and I worry about embrittlement etc. I'm just going to bite the bullet and replace mine this winter when there is no flying to be done. -- Jim

STRUT LEAK STOP IDEA #4 (090201)
From: Porter Houston <porter.houston@home.com>
Subject: Re: September #1 GTS Internet Update
Ref: Main Gear strut leaks at the bottom.
The fix is real simple.
Remove Strut, Clean out very good especially at the seam where the plug meets the strut tube. For the final clean out use Loctite Primer ( it's in a yellow spray can). Dry out real good with compressed air. Pour just enough Loctite 290 inside the tube to completely cover seam. 290 is very thin and will wick into the seam area ( IF IT'S CLEAN). Let it setup over night. Do the same thing on the outside of the tube at the bolt hole seam. It worked for me. I recommend this even for new struts. -- Porter

STUCK STRUT... (100401)
Subj: Gear strut
From: Don Woodhams <biplane@btc-bci.com>
Hi Monty, We have a gear strut that seems to be froze, strut will not extend on jacks.It won't move so the snap ring can be removed. If we removed the bushing locking bolt will the strut then come out of the upper housing. If not how will we remove the , we think bent , strut. Thanks for all your advice. Don woodhams

Don
If you remove the bushing locking bolt probably nothing will happen. Place a 2 1/8" x 6 1/2" piece of tubing (suitably split) over the strut. See the Commings Manual. If the brass sleeve won't push up, I would remove the landing gear from the airplane. Place the gear in an arbor press and attempt to compress it. You need to push the brass sleeve up in the cylinder about 3/8" to remove the snap ring. Be sure you have removed the keeper bolt! If the strut is bent so bad you can't do this you are in "experimental" mode and you will have to rely on your own ingenuity. At this point it is a "sledge hammer" operation and may require a LOT of pressure from the hydraulic press, but I have never seen one that wouldn't come apart eventually. Mark Holliday had an Adel strut that had previously been assembled with an oversized sleeve and it took several days of effort to get it apart. Mark left the gear in the airplane and applied pressure and blew the strut out. I would use hydraulic pressure or a grease gun, with several grease cartridges available. Caution: If you use air pressure to blow the strut out, it may take 500 lb of pressure or more and create a very dangerous situation. -- Jim

FLAT STRUT... (100401)
Subj: flat strut
From: Phil Nussbaum <joem@totalseal.com>
Dear Monty,
we are in the throws of buying a swift. One of the things I found on my initial prebuy was that the right strut was much lower than the left. A look in the parts breakdown wasn't that much help unless the spring is gone soft or it has broken. I don't think there is an inch of piston showing. Don't know how long the present owner has been flying it this way. I would not sign it off for ferry because I was afraid of increasing any internal damage that might already exist. Of course the gear door attach arms have been scraping the strut itself as well. This airplane had a low speed groundloop in which the left strut was replaced don't know if it material to this or not. I need an experts best guess as to what is going on with the right strut and if I was correct in not signing it off for ferry either. Thanks Phil Nussbaum

Phil
I presume you are talking about an Adel gear. If it is an ELI gear there is no spring in it and raising the level is a simple matter of airing it (with a strut pump or nitrogen bottle) The ELI should not be flown with low strut extension. Weak springs are common in the Adel gear and are not critical. When the gear is hanging down, in flight or on jacks, the spring will give full extension. The gear will only bottom out in a very hard landing. A quick way to get more strut height is to install a common 1/8" pipe threaded air valve in place of the filler plug on the strut and fill the strut with air or nitrogen. You can get an air valve like this at any hardware store for about $2.00 If the "0" rings are old the strut will not hold air pressure for very long. Regardless, a low spring in the Adel gear is not critical. -- Jim

STUCK STRUT UNSTUCK... (110201)
Subject: RE: Don Woodhams <biplane@btc-bci.com bent gear
From: "Owen, Larry" <Larry.Owen@Tenethealth.com>
Hi Denis
Under the "Been there, done that" heading..... several years ago..... after ground looping and bending the left gear, it took a press and some very gentle heating with a propane torch to get it to release. Heat it with a "spreader" on the flame and keep it moving. You don't need to get it hot, just warm all over, as you only need a few thousands expansion to get it to release. Hope this helps....Larry Owen N78287 El Paso, Texas 915-577-6832

CAN’T GREASE IT... (010302)
Subj: Main Gear Pivot Point
From: Doc Moore <darladoc@sport.rr.com>
Jim:
Can't get left main zerk fittings to take grease... front or rear. Have pulled fittings and they're clean. Have cycled gear up..45.. and 90, trying at each spot. Still won't take grease. Am going to heat the trunion housing with my heat gun this afternoon to try to soften old grease to see if thats the problem. Its ELI gear... could the bushing have spun? If I elect to remove in order to clean and inspect are the four bolts on the front and 4 on rear holding the assembly in going into nut plates or just plain nuts? My AI is going to submit the 337's on the JPI Instruments per your suggestion. Thank you for your help, Kindest Regards, Doc Moore

Doc
The ELI gear, when manufactured, had no grease fittings. So what you have is field installed by who-knows-who. Are they the flush fittings for a needle point grease adaptor? I suspect that the brass bushings in the aluminum trunion caps were not grooved for grease retention. You might try "wobbleing" the gear while the airplane is on jacks to get some grease in there. What you are experiancing is not unusual. I had a set of ELI gear and installed some grease fittings in the trunioin caps but never could get much grease in there. I guess the way the manufacturer of the gear intended, you must remove the 4ea. 1/4" bolts front and rear and grease the bushings ny hand. Yes, there are nut plates for these bolts. -- Jim

AIRIN’ UP THE STRUTS...(030302)
Subj: N80572
From: Bill Doty <wdoty@earthlink.net>
Jim, I am ready to air (nitrogen) up the struts but have trouble figuring out the instructions for ELI gear. Need to add hyd. fluid but I am not sure of the process! Refers to upper plug and lower bleeder. Believe the upper plug is at very top of strut but the bleeder is in question. I have located the plug inside bottom of strut but seems to me it would drain the strut!? Maybe a quick note would help to get past the "senior moment"... Also, the high psi air valve stem destroyed its self on removal ! Broke off inside the brass housing. Any idea where a new housing could be purchased? I have the stem on order. The good news is that the gear and flaps cycled and all the lights are working !!!!!! Thanks, Bill Doty

Bill
Read "Landing gear - struts" in the "Monty the Answer Man" archive. You have me confused when you say "broke off in the brass housing" - The air valve for the ELI gear is in the aluminum fork. I don't know of a brass housing. Maybe someone in the past has installed a thread repair......? As long as you are starting from scratch, with the strut flat, fill it with 5606, then air to 3 - 3/4" extension. -- Jim

AIRIN’ UP THE STRUTS PART II...(030302)
Subj: N80572
From: Bill Doty <wdoty@earthlink.net>
Jim, I have printed out the pages in "landing gear/struts" and will read them. The Valve I referred to ,as brass, is the Schrader valve. It is in the aluminum fork. Have new ones on order from Swift Parts. When you say "flat", I assume you mean "no air". Adding oil to the top hole, how do I know when it is full? I still am in doubt as to what is referred to in instructions as "bleeder valve". Will read the archives and get back to you, if still in a state of confusion. Thanks, Bill

Bill
With it flat (no air) just take one bolt out of the scissors, presuming the brake line is removed, the whole lower unit can then be pulled out. Fill it up with 5606 thru the hole in the strut. Reinstall it with vaseline on the "O" ring. You may have to raise the tail and level the airplane to get the metering valve which "floats" on one rivet to hit the hole in the strut when reinstalling. If the landing gear is removed from the airplane, the metering valve van easily be removed, it can't be removed in the aircraft. You might have a small pipe plug on the bottom of the strut which could be called a bleeder valve, usually it should not be necessary to remove this. -- Jim

DON BARTHOLOMEW IS HERE WITH: AIRIN’ UP THE STRUTS PART III...(030302)
From: Don Bartholomew <diamondswift@earthlink.net>
Subject: air valve
Bill,
If I read your email correctly, the valve stem core (the part that comes out of a tire stem) broke when it was being unscrewed from the housing (brass) of the schrader valve, and part of the stem remains in the housing. If this is correct, you can remove the schrader valve with a deep 7/16" socket. It is better to use a six point socket to reduce the possibility of stripping the hex. Once that is out, just install a new schrader valve. Check with Swift parts, I think they have them. Also, once the schrader valve is removed from the strut, you may be able to push the remaining piece of valve core out with a small punch (from the strut side). If the threads in the housing are damaged, you can get a thread chase for a standard tire valve (Napa store) and clean the threads. I imagine you have already looked at the archives, but take the bottom plug out, compress the strut, and pour fluid in the top until it runs out the bottom. The strut has to be filled a certain amount before there is enough fluid to fill a cavity and overflow. The excess is what runs out the bottom plug. - Don

On to page 3 of landing gear struts...