Trunion atachment concept

[john pike]

i was thinking, of a clean way to attach the trunions on my next cannon,

heres a pic of what i came up with,
the gray area would be JB-weld,
the idea would be that you would mill an angle into the  wall of the trunion hole.
after bring it out.

then cutting an matching angle onto the trunion shaft,

filling the areas with JB weld and pressing in place.

my thinking is that the JBweld washer now dried would act as a retaining ring and also gluing it in place, i dont know if it could shear off or not,
but being on an angle, the pressure would be transfered to the barrelwalls.

just my overworkedbrain keeping me up at night.
opinions wanted.

[Double D]

Build your self a sample and put it in a vise and see how much it takes to break it off with a hammer.  If you can beat the trunnion out of the pocket it is not strong enough.  If you bend the trunion or break the trunion of the joint is okay.

Let us know how it works.

(thanks George)

[GGaskill]

Just so you know where I am coming from, I both have a TIG welder and know how to TIG weld and I TIG weld all of the trunnions I do unless there is a welding problem with the material used for the barrel and trunnions.  In such a case, I will silicon bronze braze instead. 

Whether your system would work depends on the properties of JB Weld and the amount of recoil force your gun generates.  The recoil force will tend to rotate the trunnions about the front of the pocket so the anchoring (weld, etc.) in the rear will be carrying most of the load.  While it is unclear how much "tensile lap shear" applies in this case, it would appear that just gluing the trunnion in would give as much strength as making a "keystone" would.  Since the depth of the pocket for the trunnion is going to determine how much glue you can get in action, I can't seeing JB Weld as providing much strength.

The carriage is going to have a tendency to keep the trunnions in the barrel, especially if the pocket has perpendicular sides.  But I would be unwilling to rely on a wood carriage to perform that function. 

JB Weld Properties
Properties . . . . . . . . (psi)
Tensile Strength: . . . 3960
Adhesion: . . . . . . . . 1800
Flex Strength: . . . . . 7320
Tensile Lap Shear: . . 1040
Shrinkage: . . . . . . . .  0.0%
Resistant to:  . . . . . . 500° F

[Cat Whisperer]

i was thinking, of a clean way to attach the trunions on my next cannon,
....
opinions wanted.

Use the strengths of the materials you have to the max.  
JB Weld is an adhesive (between two adjacent surfaces)- use it for that - the shear strength is not it's strong point (as a solid).

We use a number of high-tech adhesives (EBWhite and many flavors of loctite) in manufacturing of motors - which encounter continuous vibration from inside and from the load.

Your best bet is to build a CLOSE fitting trunion that will fit (just) into the mortise (the hole for it).  That way the adhesive is used to it's strength - bonding two surfaces.  (Which on the rear are going to be compressed (as George has mentioned) and stretched  at the front.)  If the clearance is minimal you will be using the adhesive at it's best.  Most of the shear forces will be where they need to be - perpedicular to the trunion.  The trunion is locked into position by the very small clearance being filled with the adhesive - compressing it, the shear forces being born by the trunion and the trunion pocket.

Loctite is similar - you can even choose the loctite product to match the exact types of metals.  It EXPANDS on hardening - that really locks it up tight!