Ken's Sonex 1243

[Area 51%]

Helped a guy replace the mount bushings on his Xenos. There was somewhere between 1/2in and 3/4in difference in the thrust line/angle after the change. His report was it flew no different.

[Sonex1243]

Richard, I know what you mean! I am really trying to knock that down some as I find myself getting to the point of drilling, then, start second guessing myself and get into a check / recheck cycle! Whenever that happens, I always remember John's famous words "we are not building a swiss watch" and the CAD program gets everything down to the most minute measurement. I stay within 1/32" or less tolerance.

So, with the help of the daughters boyfriend, I made a new set of shims that covered the gap better and re-leveled everything and plopped the mount back in. Everything squared up, went through the OCD cycle, took a deep breath and drilled it up to #30! Now I am ordering a 100 degree 1/4" countersink as I didn't have one..

Did you guys upsize to 1/4" and then countersink for the bolt blush fit? I thought I read something that some folks upsized to a certain size, countersunk , then upsized to hole to bolt size?

[Rynoth]

Did you guys upsize to 1/4" and then countersink for the bolt blush fit? I thought I read something that some folks upsized to a certain size, countersunk , then upsized to hole to bolt size?

Both methods can work, the important bit is not either enlarging the hole at the bottom of the countersink, or creating a knife-edge at the bottom of the countersink. I was fine with having my bolts slightly proud to avoid either issue. The reason for the countersink is mostly cosmetic to keep the cowling from "bulging" over the engine mounts. Being slightly proud at the bolt heads wasn't an issue for me, the cowling still fit snug.

[Sonex1243]

Thanks for the info Ryan. My original plan was to be slightly proud so when the bolt is torqued it would pull it down flush.

Since I am waiting for hardware / tooling to finish the mount, I started honing out the gear leg holes to remove the powder coating and polishing the gear legs. I have a light film of WD-40 on the leg and it helps a lot getting them in and out. Is this the same route everyone else has taken?

[Sonex1243]

The engine mount is officially done! Cut down the "infamous" two lower mount bolts and installed the mount and hardware.

[Sonex1243]

So, working the landing gear legs and have been lightly honing and polishing the TI rods to get a good slip fit with a light coat of WD40. I am fighting two weld spots on the left lower mount, it leaves a mark on the TI when I try to remove it by rotating back and forth while pulling.

I am afraid I will get too aggressive and hone/polish too much. I am also trying to work the spots down with round and half round files. I still have the upper ends to do as well. Very time consuming.




One penetrated weld spot


2nd penetrated weld


TI gear leg marks. The TI marks polish out with light sand paper.

[Sonex1243]

Finished fitting the gear legs into the engine mount tonight. Blocked everything up and set the toe-in. Only 1/6" short on the dimension from the fuse skin to the axles, works for me. Now for that 12" 1/4" cobalt bit that I thought I had to mark the legs for drilling...

[GordonTurner]

Wow. Ken, that looks fabulous. I am approaching the motor mount gear installation myself and you’re upside down method looks much easier and more accurate. For setting the toe-in, does it matter that there is no weight on the gear, or is that a prerequisite anyway?

Gordon

[Sonex1243]

Wow. Ken, that looks fabulous. I am approaching the motor mount gear installation myself and you’re upside down method looks much easier and more accurate. For setting the toe-in, does it matter that there is no weight on the gear, or is that a prerequisite anyway? Gordon

Hi Gordon,
Yes, the axle rigging is done with no load on the gear per the plans. I used a method perfected by Bryan Cotton, he helped me out with his method of setting the motor mount in place upside down with the plumb bobs since the measurements were referenced from the bottom. It also worked right in to the gear leg installation and axle rigging. Easy to block it up and set the toe in along with measuring from the bottom of the fuse.

Ken

[GordonTurner]

Nicely done. Thanks

Gordon