Engine mount doubt

[Jeff XL79]

This is a cut case 45 built by Casler. I'm not sure about the engine mount to rear engine case method of attachment.  The engine mount bolts are 3/8-20. The bolts are inserted through the  rubbers and threaded into the plate. There is a lock nut on the end of the bolt. Is this safe?

[Jeff XL79]

More pics.

[Jeff XL79]

More pics

[Jeff XL79]

Does anyone know what this engine mount was off of? I was told it was off of a hummelbird but they are bed mount.

Jeff

[GTS225]

There is a lock nut on the end of the bolt. Is this safe?

I assume they're "pinch-lok" type nuts.  Otherwise, no......there should be FULL engagement of the nut with the bolt.  As a rule-of-thumb, you should have half the thickness of the nut in bolt threads sticking out.
T'were me, for engine mount bolts in an airplane, I think I'd use grade 8 bolts with castle nuts and cotter pins, and I like nylon style lock nuts.  And 3/8" seems kinda small to me for holding onto something as important as the engine and prop.

Roger

[Chuck in Indiana]

Assuming that the plate itself is tapped, I'd use a longer bolt, preferably an AN. The other issue is no safety on the bolts that thread into the case on the mount and magneto mount. Maybe a drilled head and safety wire to each other. No offense meant to GTS, but 3/8" is a little over kill for this size engine. Grade 8 bolts are hard, and as hardness goes up, so does brittleness. AN bolts aren't hard, and handle vibration much better.

[Jeff XL79]

Thank you GT and Chuck. I'll upgrade the hardware. I'm also going to add a cable attach point. The 45 is a notorious shaker regardless of balance. 

I'm not sure I can use AN bolts due to the plate being threaded.  Don't AN bolts have a limited threaded area? They have enough thread for a washer, nut and two turns of thread. I'll look through my aircraft spruce catalog. 

Thank you again 

Jeff

[Dan_]

Grade 8 bolts are hard, and as hardness goes up, so does brittleness. AN bolts aren't hard, and handle vibration much better.

Also, AN bolts have rolled threads instead of cut threads.

The un-threaded/threaded spec can be controlled by bolt length, "grip" and washer stack.

The size/metallury of of the car mounting studs are proven over eons of time.

Lots of overkill on that mount... That "ring" tubing for instance.

If that's a firewall and not a test stand, it may be off one of the wooden airframes.

[Jeff XL79]

It's mounted on my test stand Dan. 

I'll try to get AN hardware if I can find a bolt configuration with the proper thread and length of thread. The one hitch in the fly ointment is that the rear plate of the engine is threaded 3/8-20. If I can find the right length of AN bolts It might be good to drill out and helicoil the plate. That is, if that's allowed in aircraft standards for hardware. 
This may be a cool engine but I'd really appreciate a simplified 37 with the full case at times. 

Jeff

[Dan_]

I'll defer to the more experienced, but since it's already threaded, it would be hard for me not to want to keep the 3/8 bolt size.

Just get the AN ones with the grip the right length to go through the rubber part and the threads extending far enough for a jamb nut on the back side of the plate...  You can order them with drilled heads and nuts for safety wire.

The jamb nut with built in washer (or separate washer) would spread the force to a larger area of the plate it would seem.

Can't really tell if the bottom bolts go into the car mount stud holes though, but it looks like you could jam a nut on the top bolts.  

While we are killing it over, may as well make sure.

[Jeff XL79]

I think this will work.  I'll safety wire it before it's started. 

Thank you all for your input. 

Jeff