New Build Project - a weird Webley-related pistol from the 1920's

[ccdjg]

Earlier this year I started a new project, as a follow up to my Webley Whiting effort reported back in 2016

http://www.airgunbbs.com/showthread....hlight=whiting .

http://i.imgur.com/NmYbFUH.jpg

and I thought some of you might be interested in how it panned out. There is currently a brief account of the project in the Vintage Airgun Gallery, but as it is likely to get pulled by Photobucket any time now, a post here would seem appropriate. You will be relieved to know that I have given up on Photobucket and will be using Igmur for all my pictures from now on

I have always been intrigued by the twist-grip spring air pistol patented in 1924 by Douglas Johnstone and John Fearn (of Webley) and Frank Clarke, which was never actually manufactured. http://imgur.com/a/mTgAq .

The pistol has the air cylinder in the butt, and is cocked by twisting the grip downwards until the piston is pulled into engagement with the sear. In theory the twist action gives a mechanical advantage of about 2 over a straight pull design, as used in some butt cylinder air pistols. The great Mac Evans made two reproductions of this design some years ago,(these will also still be illustrated in the Gallery with any luck) and he concluded that in reality frictional forces made the twist system extremely difficult to cock and the pistol would never have been a commercial proposition. Despite this, I decided to have a go at making one myself, as I am more interested in unusual cocking mechanisms than performance, and I really wanted an example in my collection.

The patent drawings provided the starting point. There were two main challenges with the build. Firstly the main frame of the pistol was a single chunky piece of metal and would either have to be cut and shaped from a solid steel block, or cast. Casting, especially in steel, was not an option, so I followed Mac’s example and used the former method, even though it meant a lot of heavy milling and filing. Secondly, there was the problem of how to cut the two helical slots in the cocking slide, as these had to be the right pitch and exactly in line with each other.

By playing about with the change gears on my Myford lathe I was able to get the lathe saddle to move the correct distance (about 3 inches) for each rotation of the mandrel to give a helix of the right pitch. An end mill held in a flexible drive from my electric drill was clamped in the saddle to provide the cutting action. The cylinder tube was clamped in the mandrel chuck, so that as this was slowly rotated by hand the end mill moved forward and cut a slot in the form of a helix. http://i.imgur.com/PlRegd9.jpg Progress had to be very slow as an electric drill flexible drive is not what you would call an ideal milling machine, but it got there in the end.

The starting materials for the build consisted of a 30mm thick steel block for the frame, sections of round steel bar for the grip and for the piston, and a length of precision steel tubing for the cylinder. http://imgur.com/a/bbht5

The barrel was cut down from an old defunct air rifle barrel.

The rough shape of the frame was cut out with a hacksaw (30mm thick - very good for the biceps) and roughly milled with the recess for the trigger/sear mechanism . It was then drilled out for the barrel and also to take the cylinder tube http://imgur.com/a/gcULb. The solid round bar for the grip was bored out to take the cylinder tube. http://i.imgur.com/gEjTAHG.jpg

The piston was turned down on the lathe, bored to take the spring, and fitted with a leather washer. http://imgur.com/a/T7z1E

According to the patent, the grip contains two fixed pegs which ride in the helical slots of the cylinder tube and contact a rim at the base of piston. Twisting the grip causes the pegs to drag the piston backwards against the tension of the main spring. Mac found that there was considerable drag resistance in this system, needing “Herculean effort” to cock even a modestly strong spring. The patent does mention that “friction rollers” could be used instead of fixed pegs, so I looked at this as a possible way of reducing friction. At first I used freely rotating steel balls instead of pegs, and these worked very well but their area of contact with the piston rims was very small and this led to indentations in the rim and increasing friction after several shots. I then tried rotating steel pegs http://imgur.com/a/Ty1HS , which proved to be almost as free running, and because they gave a larger bearing surface on the piston rim, there was less tendency to damage the piston rim. To further minimise wear and tear on the rim and on the sear-engaging ridge of the piston, the whole piston was case-hardened.

The piston and spring are held in place by an end plug. This plug was itself fitted with a small spring that pressed against the base of the grip when the grip is in the closed position, so helping to keep the grip locked in place when firing. http://i.imgur.com/VedPWCs.jpg

The barrel was pinned into place in the frame and threaded to receive the breech screw, which in turn was made on the lathe from round steel bar. http://imgur.com/a/OCmue

The grip was milled to an oval profile and then flutes cut into it to help with cocking. http://imgur.com/a/hnC2J.

After making the trigger / sear unit and the trigger guard http://imgur.com/a/yT3fc, everything was polished and fitted together http://imgur.com/a/9JgLE.



Once I was sure that the gun cocked and fired I was then ready to apply the finishing touches. First came the lettering, which was photoetched on by the technique I used for the Whiting. On the top flat I provided a description of the gun and its original patent number, and on the base of the grip my personal details. So in years to come the gun, there should be no doubt that the gun is a copy and not an original prototype. Once the lettering was done to my satisfaction I hot blued the pistol in a sodium hydroxide/sodium nitrite bath to give a deep ebony black. I could have gone for a more vintage blue, but as the gun was admitting to be a 21st century reproduction I preferred to use a modern finish. These are some pictures of the final result.

http://i.imgur.com/45Dr9c9.jpg
http://imgur.com/a/x5M2B
http://imgur.com/a/uShqn
http://imgur.com/a/sU3ZD
http://imgur.com/a/mGtLF
http://imgur.com/a/IQw2P


Now, what about performance? To cock the gun, the main body is held firmly in the left hand and the grip is pushed upwards against the pressure of the spring in the base of the grip and rotated slightly clockwise to free it. The grip is then rotated firmly downwards in one twisting movement until the sear engages, and it is then returned to its locked position. . Once the pellet or dart has been inserted into the breech and the breech screw screwed in place, the gun is then ready to fire.
http://imgur.com/a/XRb1m

I experimented with various springs and found that a Gat spring had an ideal diameter to fit inside the piston, but it needed cutting down significantly in order to be able to get it into the cylinder without excessive compression. Interestingly a Tell 2 spring also proved too long, so I could not make an exact comparison of the powers of these two pistols by using the same spring in both guns. With the cut down Gat spring I could just comfortably cock the pistol repeatedly without experiencing any wrist strain. Attempts to use a stronger spring made the cocking effort very uncomfortable, and the increase in power was generally too small to make it worth bothering with.

The main weakness with this design is the low swept volume, which is forced upon it because only a ¾ twist is feasible for the normal human being, unless he is double jointed, so without some kind of ratchet system the piston movement is restricted to less than 2 inches. This means that the power of this design is never going to be high. The swept volume for my pistol is only 9 cc, compared with 12.9 cc for the Gat, 10.9 cc for the Whiting, and 8.5 cc for the Tell 2. As the spring strength was significantly lower than for the Tell 2, I expected the power of the twist grip to be significantly lower, but in the event I was pleasantly surprised to find that it matched the muzzle velocity of the optimally performing Tell 2 very closely, both giving average values of 200 fps with Milbro slugs (5.74 grains).

Unfortunately the 4.5mm barrel was quite heavily rifled and gave a tight fit with most .177 slugs and waisted pellets, so to get reasonable and reproducible muzzle velocities it was necessary to pre-size all the pellets by pushing them through the barrel with a rod. Darts were not a problem.

Here are some comparisons using the Milbro slugs:

Near mint Gat : ~ 300 fps
Webley Whiting: ~ 175 fps
Good condition Tell 2: ~ 200 fps

Twist-grip: ~ 200 fps (max. 211, min. 180)

With waisted pellets, weighing 7.56 grains, the muzzle velocity fell to an average of 178 fps. The calculated muzzle energies for the two types of ammunition turned out to be identical, at 0.57 ft lbs.

I have not carried out any proper accuracy tests, but the following target shows 10 successive shots from 6 yards using waisted pellets, hand held but resting on a surface. http://imgur.com/a/JbMya

This puts the twist grip clearly into the category of a low grade plinking pistol, which does not do justice to the solid, heavy construction suggested by the patent drawings - my pistol weighed 1.18 kilograms, slightly heavier than a Webley Senior! To ever become commercially viable, the design would have needed adapting to a cheap folded metal type of construction.

Even so, having now fired a couple of hundred shots through the pistol, I find that the twist-grip principle is very pleasant to use. There is no fumbling for a latch or a lever and the whole cocking stroke can be achieved in two simple twists. The downside is the cumbersome loading system involving unscrewing and screwing the breech screw.

I think that if the design could be improved with a ratchet twist system to give a higher swept volume and more power, and a simpler loading system introduced, this would make for a much more viable gun.

All in all, a very interesting project and a very interesting design.

[Geezer]

Amazing piece of work.

[Garvin]

Absolutely awesome work, John, truly impressive. Thanks for posting this account.

[RichardH]

Brilliant

[nige346]

Awesome work and a great account of it, thoroughly enjoyed reading it, Thanks for sharing

[coburn]

Very impressed with this and your previous project. Given your skill can you make me a time machine next

[harvey_s]

The best compliment I can pay your work is to say "you sir, are a true craftsman."
A very nice piece of work if ultimately based on flawed original design...but still a terrific job

[micky2]

A excellent job indeed. and very well done for stamping it's a reproduction on it.

[45flint]

Brilliant job and post! Thanks for all the pics and detail. You've raised the bar so high for a informative post don't know how anyone can top this.

[deejayuu]

Humbling. Thanks for sharing.

[Mark D]

You Sir, have 'skills' . A great piece of work, thanks for sharing.

[PaulR]

Superb - fascinating reading and excellent craftsmanship.

[ccdjg]

Thanks everyone for your words of encouragement. I can assure you I am no craftsman, just an academic who hadn't touched a lathe until he retired a few years ago, and lucky to have plenty of time and patience to compensate for his machining ignorance.
Now for a long break, and then to start another build, whateve that might be. Perhaps something with a bit more oomph this time!

[Mark D]

Thanks everyone for your words of encouragement. I can assure you I am no craftsman, just an academic who hadn't touched a lathe until he retired a few years ago, and lucky to have plenty of time and patience to compensate for his machining ignorance.
Now for a long break, and then to start another build, whateve that might be. Perhaps something with a bit more oomph this time!

You underestimate your abilities young man

How about a Brown pneumatic - now that would have some oomph !