Nose gear shock static "gap"

[Birdseyeview]

I noticed that there is a gap between the brown rubber top bushing and the lower engine mount that holds the nose gear in place. I understand that this "gap" does open up during load on the shock assembly but while it's static it seems in conflict with what's stated in the build manual. The build manual implies that the assembly should all be tight (no gap) when torquing the top bolt that caps off the shock assembly. I don't know if this static gap is normal or is a product of the shock donuts taking a set or shrinking during the decade this project sat idle before I bought it. I've incorporated the service bulletin that opens up the bearing diameter of the shock tube so that there is no binding during shock compression travel. I measured the thickness of the four rubber shock donuts and they all vary slightly within 1.100" to 1.125". Does anyone have a new shock donut they could measure to compare with mine? Has anyone else with a nose gear assembly seen this "gap" while the plane is just sitting still?

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[DesertFox4]

Larry, I’ve seen some finished and flying with a little gap before like the one shown below. It looks about like yours does.
* Click on photo two times to be able to zoom in for close up of gap.*
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Finished and flying Model7 with 914 Rotax.


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This is a photo of mine however, it was taken before wings were installed along with cowlings, prop, spinner, windshield, interior,
avionics, ect. Can’t remember if I had a small gap after finishing the build though. I’ll check next time at the hanger.

[Birdseyeview]

DesertFox4,

Thanks for the photo confirming that I'm not the only one to have this gap. As a follow up: I talked to Deb at the factory and she measured a new black rubber shock bushing for me and it was 1.250" thick. As stated below my thickest one was only 1.125 (in the loaded state). When I unload the weight on the nose gear the gap reduces to near zero. Even though my shock bushing haven't been subjected to more than a few hours of taxi operation, we speculated that because of the actual age of my bushings they may have dried out and shrunk a little over time. Deb also stated that the gap is not a "problem" and I take that to mean that it's OK to use as is, even though it may be technically out of new spec limits. The new bushings are $41 each so I'm not going to replace them right away. I'll keep an eye on them for any further shrinkage over time.

[Delta Whisky]

Larry - I don't have the third wheel at that end of the airplane and can't see all of the kinematics involved but just as an observation, would it be reasonable to add washers on top of the rubber donuts to take up the slack and extend the nose gear to its original position? That might also minimize some distracting thumping and bumping. Just a thought.

[Birdseyeview]

Larry - I don't have the third wheel at that end of the airplane and can't see all of the kinematics involved but just as an observation, would it be reasonable to add washers on top of the rubber donuts to take up the slack and extend the nose gear to its original position? That might also minimize some distracting thumping and bumping. Just a thought.

I've had the same thought about adding something into the assembly that might snug it up and eliminate the gap. I like the idea of getting the gear back into its original position and I do have some rubber material of the right thickness that I just might add to the stack of black rubber bushings to accomplish what you suggest. Thanks for your input.

[efwd]

Ten year old rubber? I'd start there. 2cents please.

[Birdseyeview]

Eddie, Do you take Visa? LOL. Replacing the old rubber is the obvious way to go and I must confess that the tight wad in me has come out on this one. As I've looked closer at the rubber bushings they are still compliant so I hate to spent $165 for something that the factory says isn't a "problem".

[Rumbear]

I had a similar issue on my KF 5 that I noticed last spring. Research and a fone call with KitFox convinced me that replacement was the cure. The consensus was that the rubber pucks harden and collapse a bit over time. I replaced the old with the new. I did stack each up next to each other prior to install. The differential was about a 1/4 inch. Upon mounting the new ones, the gap narrowed, but did not entirely go away. The older ones were very hard, more like a hockey puck!

Of course, my landings are now smooth as butter! (your mileage may vary)