SonexBuilders.net

Hey Guys,

Even though I am building a Model-B I am directing this question to the legacy Sonex Tri-Gear builders since there aren't many tri-gear model-B builders out there and it appears it is all the same hardware (all SNX prefxes). The problem is I am assembling the front fork into the engine mount and it is a really really tight fit in the brass bushings even with a ton of grease on the fork. Even when I stripped the powder coat off where the plans state, the fork would not budge in the bushing where the powder coating was still present between the two bare metal spots. Since I had that issue I then stripped the powdercoating off the entire upper portion of the fork and managed to get it into the bushings with new grease. However, it is taking me using a rubber mallet to move it up and down. I can turn it side to side using both hands and a bit of force on the fork but I feel it should be easier than this. I guess I am looking for guidance on how easy the fork should be moving in the mount and what route I should go to make this a better fit. Thanks for the help.

-Tim

I'm not building a tri-gear, but I've seen several post about tight fits. Here's a tip:

When you have a tight fit like that go to Kroger or an Ice house and get a small amount of dry ice. Place it in a metal bucket (NOT PLASTIC) and place the end of your tight tube sown in the ice. Let it sit for about thirty minutes, then remove it from the bucket and rapidly place it in the tube it goes into. Make sure you pre-mark exactly where you want it. The ice will shrink the inner tube enough it should slip in easily. No grease needed.

Ed
Still awaiting my Onex full kit here just east of Graceland
Name of airplane censored by mod

Thanks very much for the tip Ed. I have seen that technique used specifically on Lear Jets when they insert that big pin that pivots the rear elevator assembly. It stays in dry ice for several hours and they only have 10 seconds to get it in. I'm a geek and watch documentaries on planes a lot haha. (Google Learjet Megafactories).

Anyway, back on topic I got the fork into the bearings, it just seems really tight even with the factory suggested grease. I am basically looking to see how free this fork really should be in the front mount/bearings and how much effort is required to move it up/down or turn it left/right. Of course there is no weight or engine on it yet, just don't want to get to the point of taxi testing months from now it only to realize I need to disassemble the whole thing again. Thanks again in advance for the help everyone!

Tim
It should not be that hard, I was able to turn mine easily from the beginning. I would seek tech help from the factory.

Jim B wrote:Tim
It should not be that hard, I was able to turn mine easily from the beginning. I would seek tech help from the factory.

Thanks Jim. So yours was able to move up and down and side to side with little to no effort? I’d contact Kerry but they are all at Sun N Fun. Thanks for your help man.

-Tim


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Just an update, my friend who is an A&P came over and verified the very tight fit. He said not to sand the inside of the bushings but that I hadn't completely removed off the bottom layer of the powdercoating. Its very thick powder coating on the fork. He suggested we sand it down by hand. I progressively sanded using 120, 220, 400 and 800 sandpaper by wrapping it around the exposed metal and turning it back and forth. My forearms are still sore days later. After test fitting it multiple times, we greased it up, and she slid in with no issues. It turns fine and goes up and down easily with a nice tight fit. Seems like these bronze bushings are a tighter tolerance than spec'ed which caused the issue. I hope this helps anyone else that runs into this issue.