SonexBuilders.net

Hey all,
When I built the airplane I didn't design in any way to be able to remove the bolts. The engine/landing gear mount is so close to the firewall that I have the bolt head basically on the firewall, and the nut away from the firewall. I know some people have made an access hole with a cover that they can screw on. I was thinking of adding that.

When I was looking at it this morning, it seems like the landing gear bolt is pretty much perpendicular to the firewall. That got me thinking - instead of an access hole, I could just drill a hole for the bolt using the mount as a guide, and then put a spacer between the mount and the firewall. The spacer would be a touch thicker than the bolt head.

Any thoughts?

Bryan, are you then thinking of pushing the bolts through the firewall-spacer-mount then bolting? It was not completely clear. I've run into the same thing except my bolts go into the gear towards the firewall with the nut sandwitched. I was thinking the same thing about drilling the firewall. But then it would take two people to fasten the bolt/nut.

Looking forward to reading comments on this.

Brock, that is what I was thinking. Yes it would require 2 people, or a box wrench and duct tape inside. I did not have room for the end of the bolt and nut on my Waiex and that is why my bolt head is next to the firewall. If I was still building, and had not already riveted the firewall on, a nice big round dimple in that location would also probably work.

Bryan, my gear bolts go in pointing aft, washers make up the distance to the firewall, and the castle nuts are on the cabin side of the firewall. It works well. The torque on the nut is minimal so there is no need to go so tight as to crinkle the firewall. There seems to be a good seal from the washers.

I am interested in what you come up with. I will be installing my gear legs soon and I want to make sure these aren't too difficult to access. Currently my plan is to insert the bolts from the front, drill a hole in the firewall large enough for a socket to get to the nut, and fabricate a removable cover plate for the holes.

I think if I build another Sonex ever I would put a nutplate in the cabin, and use a bolt with a head drilled for safety wire. If it wasn't such a pain to work on the firewall I'd put it in now.

Bryan, when it came time to replace the bolts in question per the SB, I was faced with the situation exactly as you describe. So to remove the bolts I was able to cut the head of the bolts off with a hacksaw blade and and then pull the remainder of the bolts forward to extract them. Then I backdrilled through the firewall using the engine mount as a guide. The new bolts were then installed with the head forward, a spacer between the engine mount and the firewall, and a washer and a nut on the cockpit side of the firewall. No ill effects having flown this way for years now. If I could have foreseen the future, I would have dimpled the firewall before installing it to make room for the washer and nut at the back of the engine mount. Oh and installing the new bolts and nuts is still a one person job.

Hope this helps,

Art,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,Jabiru 3300 #261

Bryan Cotton wrote:I think if I build another Sonex ever I would put a nutplate in the cabin, and use a bolt with a head drilled for safety wire. If it wasn't such a pain to work on the firewall I'd put it in now.

?? Did you use safety wire on the bolts attaching the vertical stabilizer?..........Oh wait, you built a Waiex. Just wanted to point out that there is no safety wire called out for the heads of the bolts that attach the vertical stabilizer on the Sonex. Nutplates by themselves have self "locking" qualities. But I have put torque seal on the heads of these bolts to satisfy myself that they haven't loosened since the last inspection.

Art,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,Jabiru 3300 #261

builderflyer wrote:

Bryan Cotton wrote:I think if I build another Sonex ever I would put a nutplate in the cabin, and use a bolt with a head drilled for safety wire. If it wasn't such a pain to work on the firewall I'd put it in now.

?? Did you use safety wire on the bolts attaching the vertical stabilizer?..........Oh wait, you built a Waiex. Just wanted to point out that there is no safety wire called out for the heads of the bolts that attach the vertical stabilizer on the Sonex. Nutplates by themselves have self "locking" qualities. But I have put torque seal on the heads of these bolts to satisfy myself that they haven't loosened since the last inspection.

Art,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,Jabiru 3300 #261

The safety wire in this instance would keep the bolt captive if it broke, so the gear leg could not fall off. Actually I think a nutplate would be bad here. If the bolt broke inside the motor mount, it would be very difficult to remove the part of the bolt screwed into the nutplate.

N111YX wrote:Bryan, my gear bolts go in pointing aft, washers make up the distance to the firewall, and the castle nuts are on the cabin side of the firewall. It works well. The torque on the nut is minimal so there is no need to go so tight as to crinkle the firewall. There seems to be a good seal from the washers.

Kip, Do I understand you correctly? You are using castle nuts and a cotter pin on the cabin side - right? I like that. These bolts are loaded strictly in sheer and don't really need to be tight (correct me if I'm wrong). Thus a castle nut could be put on just tight enough that the, un-held, bolt doesn't rotate. Then just install a cotter pin.