Lower engine mount nuts

[sonexsteve]

Hi all. I suspect this has been covered before.....but, how is it possible to get the nuts to go on the screw bolts inside the lower engine mount to fuselage longeron engine mount 'boxes' and onto the screws?

There seems to be insufficient space against the main gear leg tube inside the box. I've cut back the length of the lower screws and bought some AN310-4 nuts, but still can't find a way to get the nuts onto the screws.

I bought a Handee Clamp at OSH recently in the hope it would work, but it's too big.

Help!

SonexSteve

Leamington Spa, England.

[Bryan Cotton]

I had great pictures on my thread. Sadly, they were hosted on photobucket so they are gone forever. You have to cut the bolt down, sneak the nut in place, tighten via the bolt while holding the nut, and use the Force.

[mike.smith]

You could also glue the nut to the end of a piece of metal clothes hanger with something like Gorilla Glue. Once you get the nut started by turning the screw/bolt, you can waggle the clothes hangar and the glue should eventually pop off. Do a test, first. Once the nut is started you can hold it in place with your finger. Getting it tight requires some skinny pliers I think, to hold it in place.

It was a long time ago, so the details are fuzzy. But I remember it was a PITA. The Force is a good alternative!

[Bryan Cotton]

I think I remember. I put a loop of the good duct tape on my finger, stuck the nut on it, and used the Force.

[NWade]

I cheated. I couldn't figure out a way to avoid having the nuts rub on the firewall, so I used a Unibit to drill out a hole in the firewall large enough to accommodate each bolt & nut. I put the bolts in "backwards" to give the least portrusion behind the mount, then I got spare stainless steel material and cut squares large enough to cover the holes I'd drilled *plus* be secured by 4 rivets each, with some good edge margins. I used various tools to make a cross-shaped set of ridges in the material - stiffening it and deforming the center of the patch away from the bolt to provide some clearance. I then put some high temp RTV around each rivet hole and around the unibit holes (to help seal out any CO, or smoke in the event of a fire), and riveted on the patches.

Here are a couple of photos:
https://flic.kr/p/SpHJLB
https://flic.kr/p/R7ZEjC

--Noel
Sonex #1339

[Bryan Cotton]

Noel,
I thought the original poster was talking mount to airframe nut, not gear leg to mount nut. Maybe I'm wrong. I do like your idea though and had considered doing​ something similar for gear bolt access.

[peter anson]

Hi Steve, for a start If you haven't already countersunk the longeron brackets for the flush screws, don't. Use AN4 bolts and cut a clearing hole in the cowl - much easier to torque.

I suspect you are already past that so to answer your question, buy some MS21042-4 nuts. These have a reduced size hex (5/16 AF instead of 7/16AF) so that they are much more compact than the AN365 nuts, which in my case wouldn't fit without a bit being filed off. Glue the nut into an open-end spanner (translation into American - spanner = wrench) using a rubbery contact glue. This will hold it on while you poke it into the engine mount box while you do up the screw.

I had a couple of the flush head screws come loose and hammer out the hole so had to drill out and replace the screws with AN5 bolts. The MS21042-5 nuts are compact enough that I was able to fit them into that tiny space, but have a large flange so the contact area is the same or larger than AN365 nuts.

Peter

[Jim1342]

I just finished installing my engine mount by using low height all steel lock nuts (there is only shear load on the bolts and nylon inserts should not be used in the engine compartment) then use heavy bearing grease on the tip of your finger to hold the nut in place to get it started.