redbaron1982 Posted January 27 Report Posted January 27 16 minutes ago, tankman said: Good question. When the landing gear is jacked up, your lifting at knee joint, this allows the gear to swing down. This removes the compression load on the pucs and allows them to expand as much as possible. This is the evaluation that is performed during the airframe annual inspection when the plane is raised on wing jacks. You can see the wheel swing down in the video. Thanks, https://www.youtube.com/shorts/UY_9IYvVkn4 Oh, now I see, the wheel fwd/aft movement is directly linked to the pucs, so reducing the load on the wheel make it move fwd and allows the pucs to expand. Thanks!
Max Clark Posted January 27 Report Posted January 27 1 hour ago, redbaron1982 said: Maybe a stupid question, but how this helps the pucs? The airplane weight is still on the pucs. If any, the only thing you are helping is the tire itself. I was trying to figure that out as well. Isn't the shock link connected to the same point that the jack is? Also can someone help me with what wear and tear/future expense these are saving us from?
EricJ Posted January 27 Report Posted January 27 29 minutes ago, Max Clark said: I was trying to figure that out as well. Isn't the shock link connected to the same point that the jack is? Not the same point but the same part. The jack might reduce the force on the pucks a bit since the lever arm is smaller. 29 minutes ago, Max Clark said: Also can someone help me with what wear and tear/future expense these are saving us from? Pucks seem to last for decades, so I have the same question. Puck aging seems to be more about sunlight and environmental exposure than whether they have weight on them. 2
IvanP Posted January 27 Report Posted January 27 25 minutes ago, Max Clark said: I was trying to figure that out as well. Isn't the shock link connected to the same point that the jack is? Also can someone help me with what wear and tear/future expense these are saving us from? I replaced my pucks in 2023 - parts were about $1,200 then if I recall. Today's pricing on Spruce is $1,980 for full set. Add labor as neeeded. I think it took me about 5 hours or so..
LANCECASPER Posted January 27 Report Posted January 27 5 hours ago, EricJ said: Not the same point but the same part. The jack might reduce the force on the pucks a bit since the lever arm is smaller. Pucks seem to last for decades, so I have the same question. Puck aging seems to be more about sunlight and environmental exposure than whether they have weight on them. Not on long bodies (especially with extended range tanks left nearly full) . I think Don Maxwell was mentioning that on heavy long bodies that they don't pass the test after about 6 years. 2
tankman Posted February 8 Report Posted February 8 Each year during the annual inspection, the plane is supposed to be jacked up off the floor. This takes the weight off of the disks/pucs. This allows the disks/pucs to to expand back to an uncompressed condition. The disks/pucs are inspected with an “on condition” criteria. They are inspected for any cracks, deterioration or bulging. The tire/wheel is lifted up and down to determine if there is any play/movement on the disk tower. If there is no movement, the disks/pucs have expanded indicating a satisfactory condition. If there is play, this indicates that the disks/pucs rubber has harden to a state that has very little resiliency. This is demonstrated by the height difference shown in the picture of the 2 stacks of disks/pucs. New disks/pucs are one inch high. The disks/pucs should be replaced at this point. 1
47U Posted February 8 Report Posted February 8 1 hour ago, tankman said: The disks/pucs are inspected with an “on condition” criteria. They are inspected for any cracks, deterioration or bulging. The tire/wheel is lifted up and down to determine if there is any play/movement on the disk tower. If there is no movement, the disks/pucs have expanded indicating a satisfactory condition. As many have posted previously, old on the left, new on the right. The vintage shock disc retainer bottom plate wasn’t flat. You can see the slight dome on the top disc, which was on the bottom of the stack on the airplane. I think they were last done in the mid-late ‘90s? I’ll have to look at the date code/logbook. Another change between the vintage shock disc retainer and new production… the new retainer allows the disks to stand taller because the bottom plate is lower, closer to the bottom mount. The overall height is virtually identical. It won’t take much compression to get the collar and bolt installed. I didn’t like the condition of the old retainers… and what would they look like in another 20 years? With less static compression, maybe the discs will last a little longer. (Mooney had them in stock… but oh, boy. Eye watering amu’s, more than 4 amu for the pair.)
kortopates Posted February 8 Report Posted February 8 13 minutes ago, 47U said: (Mooney had them in stock… but oh, boy. Eye watering amu’s, more than 4 amu for the pair.) Lasar has their own PMA version of these which were half the cost of the factory shock disk towers. Many fail to visually check inside the tubes at the bottom for corrosion. It only takes 1/10 of loss of the tubing thickness from rust to render them unairworthy. I squirt some ACF50 into the bottom to prevent rust from water getting in there; but LPS3 and many other things would work as well. 2
IvanP Posted February 8 Report Posted February 8 I just got a set of savers from Carl. Noticeable expansion of the discs when I lifted the plane. I use the cheap Harbor Freight 4 ton jacks - drilled holes in the bases and put small screws in to keep the jacks from sliding around. Overall, I lke the product. Takes only couple of minutes to lift the plane on them after flight.
tankman Posted Friday at 12:27 PM Report Posted Friday at 12:27 PM The ability of the puc to expand when the load is removed determines its useful life. The expense of replacing the disks/pucs is approximately$2,500 to $3,000. The pucs resiliency on a long body lasts about 5 years due to the weight of a long body. For short/mid bodies, the life is around 10-12 years.
GeeBee Posted Friday at 04:55 PM Report Posted Friday at 04:55 PM Somehow, oleo struts are looking better and better.
Max Clark Posted Friday at 08:54 PM Report Posted Friday at 08:54 PM 3 hours ago, GeeBee said: Somehow, oleo struts are looking better and better. I heard a rumor about this - is anyone actually working on pulling this off?
IvanP Posted Friday at 10:25 PM Report Posted Friday at 10:25 PM 1 hour ago, Max Clark said: I heard a rumor about this - is anyone actually working on pulling this off? As appealing as oleostruts may be, it would lkely require major changes in the gear system and STC. The cost v. benefit analysis may not be favorable for such endeavor.. 2
Sabremech Posted Saturday at 02:16 AM Report Posted Saturday at 02:16 AM Having done plenty of shock disk changes, I don’t see how this would make a difference to shock disk longevity on the nose gear. They are under heavy compression all the time unlike the main gear. I could see this helping possibly extending the life of the mains but not sure by how much. Are they worth the investment on any other model than the long bodies? I’m not sure. David 2
LANCECASPER Posted Saturday at 03:04 AM Report Posted Saturday at 03:04 AM 6 hours ago, Max Clark said: I heard a rumor about this - is anyone actually working on pulling this off? The factory was working on a gross weight increase that would have included struts. That project was put on hold about 5 years ago.
IvanP Posted Saturday at 05:20 AM Report Posted Saturday at 05:20 AM 2 hours ago, Sabremech said: Having done plenty of shock disk changes, I don’t see how this would make a difference to shock disk longevity on the nose gear. They are under heavy compression all the time unlike the main gear. I could see this helping possibly extending the life of the mains but not sure by how much. Are they worth the investment on any other model than the long bodies? I’m not sure. David Yes, the nosegear discs are under higher cmpression than the mains. Still, lifting the plane reduces the weight on the discs which could arguably extend the longevity of the discs in teh nosegear as well. I have seen some Mooneys with very tired nose gear discs. Time will tell.
DonMuncy Posted yesterday at 02:56 AM Report Posted yesterday at 02:56 AM I think that it is pretty well agreed that the weight compressing the discs is a major factor in how long they last, as evidenced by the fact that the heavier late model planes require more frequent disc replacement. If that is true, keeping the weight off the discs, as these Puck Savers do, would almost certainly be helpful in extending the life of the discs. It would seem that the only questions would be how much their life is extended, and whether it is worth the extra time and effort necessary to put the Puck Savers in place each time you put the plane in the hangar. It seems that a lot of plane owners think they are going to be flying again in a few days, so they may reason that it isn't worth the x extra minutes it takes to hook up the Battery Minder, jack up three Puck Savers, put plugs in the air intakes, hook up the engine desiccator, etc. 1
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