Tuesday, February 27, 2018

Composites and "Metal-Thinking"

A good friend brought me his NEW Beretta A400 Black target shotgun with the whizzy carbon fiber rib.  Yup, a carbon fiber rib, an idea that ranks right up there with the GunPod and the model 486-MN but, I digress.  The problem is that the carbon rib is attached exactly as if it were a metallic rib and if there is one thing that composite structures don't like, it's holes being drilled into them for bolts or pins.  Beretta simply drilled the rib and inserted a roll pin, directly into the carbon fiber layup.  Due to the fact that composites like carbon, Kevlar and glass are actually very flexible fibers held in shape by a matrix of either epoxy, polyester or vinylester resin, any load that is introduced into them must be spread over as large an area as is practicable.  Failure to do so will result in the elongation, chipping, deformation and eventual failure of the part at the drilled hole.  The standard method of spreading the load of a bolted or pinned fastening or joint in a composite structure is to use a flanged bushing set in epoxy on either side of the composite.  The bolt or pin bears against the bore of the bushing while the outer flanges spread the load into the structure.  This is the method that I used to permanently end the problem of the rib loosening and spitting its retaining pin.

The original configuration, using "metal-thinking"

The rib machined to accept the bushings on each side

 The flanged bushings that are epoxied in place and new retaining pin

The finished job

Tuesday, January 30, 2018

"Anglicizing" a Fox

This is the Sterlingworth from the previous post.  The client wants an American gun with English flavor but it also has to be something unique.  Obviously a Fox has to be the basis, no other will do, for reasons that I've covered before.
I've never worshiped at the altar of the supposedly "superior" rotary bolt, it's a clever solution to packaging a bolt in a compact space but it offers no mechanical advantage over a linear bolt.  In fact, if not precisely fitted (they never are) or worn (very common), they do a very good job of opening themselves upon firing as the bite's ramp cams the bolt around to the open position.  The marketing hogwash printed in the catalogs about the guns "never shooting loose" or being "self-compensating for wear" sounds good but it isn't always so in reality.  When correctly fitted, the rotary bolt is as good as any other but certainly no better.  Now, back to the project at hand.  This gun will marry attributes of the two best-looking British boxlocks, the Greener and the Westley Richards.  It will combine the sleek, rounded bar of the Greener with the aesthetically and functionally distinctive, side-pivoting toplever of the Westley Richards (a design also used on early Lefever doubles).  The toplever operates a linear acting bolt of my own design.  Think of it as an American homage to the two English boxlocks that truly qualify as best guns.

The parts that won't be going back into the gun

Packing the frame for annealing

The horrible, belt-sander-shaped fences are chiseled per standard operating procedure.

The frame, modified for the new toplever

Making the toplever:  The pivot and bolt bosses and the underside are machined, the rest of the lever is shaped by hand.

Fitted up

Naturally the frame cheeks needed attention.  Not only were they originally shaped on a belt-sander, I'm pretty sure that the guy that did it was either blind or drunk.

Next is to clean up the beads around the fences and cut the pocket for the doll's head rib extension.

 The modified Fox with a standard early-Utica Fox

Here are a couple of videos of the new bolting mechanism.

The next agenda item is to do something about the forend iron relief cut in the frame.  This area looks bad enough even when done with the superior craftsmanship of the early Philadelphia days, it is positively atrocious on a Utica gun.

Machined floor and bevels

Smoking in the cover piece

The cover fitted and the hinge mechanism is made.  The spring to power it comes next.

The leaf spring that closes the cover

In action

Next is to hide the triggerplate screw.  This is done by closely fitting the cover into a machined and dovetailed (at the front) pocket in the triggerplate.  The triggerguard stud retains the rear of the cover.
The cover plate is made from 1020, the same as the frame and triggerplate.

The bow of the new triggerguard is made.  Its form is a bit more pleasing than the original part.  I've said it before, the shape of the guard and the triggers can make or break the lines of the gun.  With this in mind, I also made new triggers.

The original triggers
The new triggers

Here are a couple of areas that will need attention since these parts are not being replaced. 

The typical lumpy barrel contours
The breechface and action flats that look like they were finished by a farrier

The new rib extension is up next. 

Original rib extension removed by machining down to the original vertical braze seam

The rib extension was blanked from a piece of 4140A using a shop-made single edge profile cutter.

The new rib extension with doll's head, installed and fit to the frame

Stay tuned...