W.R Highest Possible breech seal discovery

[ptdunk]

This may be common knowledge but if not it may be of interest.

Having done the 'Talc test' I finally plucked up the courage to change the breech seal on my H.P.

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My new seal is shown fitted on the top left, and seals very nicely now, but what I found inside surprised me.

I had read that the breech had either a curved tube behind the leather seal connecting the two holes, (first variant) or two 45 degree holes as per Anson's patent on the second variant.

On the second variant breech seal on my example it turns out that what was thought to be a rivet holding the seal in position, is in fact a brass block that makes up the internal curve of a transfer port within the scooped out curved cutout in the breech.

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It simply hangs on the inside of the leather breech seal. This is a very clever and extremely simple way to reduce lost air volume in the slotted breech air passage.

I did wonder how the brass rivet held the leather seal in place, but was rather surprised to see what it actually was. Hope this is news to some of you.

According to jimmiedee's excellent article the heart shaped variant had one massive cup type leather washer that lined the whole of the slotted breech air passage.
His article here:
https://www.jimmiedeesairguns.com/pi...y-edwin-anson/

Cheers,
Matt

[Shed tuner]

very interesting..... I can't help but feel a somewhat smaller "port" channel would have helped further - but would never have guessed at that configuration !

[Garvin]

Fascinating! Are the channels in the brass insert straight (ie. drilled) or curved? I wonder if it makes any difference if the air flows through a 'C' shaped curve or a 'V'?

[ptdunk]

Fascinating! Are the channels in the brass insert straight (ie. drilled) or curved? I wonder if it makes any difference if the air flows through a 'C' shaped curve or a 'V'?

Do you mean the recess in the steel breech? I think It’s been milled with a round ended bit, like half a thick flat disc shaped hole. With the ‘D’ shaped brass insert centred in it it makes a nice curved transfer port. A ‘V’ would be less efficient I’m guessing as it’d ‘bounce’ round the corner.

As Jon says it could be a bit more efficient, ironically by cleaning all the gunk out I’ve probably slightly increased the lost air in the transfer port, cancelling out any gains from a good breech seal

Velocity is only a couple of FPS faster, but shot cycle is much nicer.

Cheers,
Matt

[Garvin]

Do you mean the recess in the steel breech? I think It’s been milled with a round ended bit, like half a thick flat disc shaped hole. With the ‘D’ shaped brass insert centred in it it makes a nice curved transfer port. A ‘V’ would be less efficient I’m guessing as it’d ‘bounce’ round the corner.

As Jon says it could be a bit more efficient, ironically by cleaning all the gunk out I’ve probably slightly increased the lost air in the transfer port, cancelling out any gains from a good breech seal

Velocity is only a couple of FPS faster, but shot cycle is much nicer.

Cheers,
Matt

Sorry, I misunderstood. It's very clever- by having a rounded internal curve it ensures the transfer port doesn't have any sharp corners. Brilliiant!

[Shed tuner]

As Jon says it could be a bit more efficient, ironically by cleaning all the gunk out I’ve probably slightly increased the lost air in the transfer port, cancelling out any gains from a good breech seal

Velocity is only a couple of FPS faster, but shot cycle is much nicer.

Cheers,
Matt

yes.. the nicer cycle is probably due to maintaining an air cushion for the piston to land (due to not leaking).

you know what you do do matt ? Get a 3D printed replacement for the brass insuert that takes up the entire milled recess, but incorporates a 2.7mm curved port all the way though internally. That should gain you some FPS and be competely invisible.

[ccdjg]

An interesting observation, Matt, and one that I would have remained unaware of, never having had cause to reseal my HP pistols. I did a quick check, and as you found, the second variant had the brass insert. However, my first variant had a diabolo shaped, flat bottomed, recess with a wide ledge around its perimeter, and the leather washer, with two holes, sat on this to create an air passage from cylinder to barrel. From the condition of the leather and the amount of dirt behind it, I am pretty sure that the seal is original to the gun.

[ptdunk]

you know what you do do matt ? Get a 3D printed replacement for the brass insuert that takes up the entire milled recess, but incorporates a 2.7mm curved port all the way though internally. That should gain you some FPS and be competely invisible.

That’s not a bad idea, the recess is 5mm wide so plenty of room for a 3D printed block with a 2.7mm transfer port. Be interesting to see how it would improve performance. That’s going on the joblist

Cheers,
Matt

[ptdunk]

An interesting observation, Matt, and one that I would have remained unaware of, never having had cause to reseal my HP pistols. I did a quick check, and as you found, the second variant had the brass insert. However, my first variant had a diabolo shaped, flat bottomed, recess with a wide ledge around its perimeter, and the leather washer, with two holes, sat on this to create an air passage from cylinder to barrel. From the condition of the leather and the amount of dirt behind it, I am pretty sure that the seal is original to the gun.

Hi John,
It’s interesting that they tried so many variations of recess & seal, they were obviously barking up the right tree given what we know about the importance of this area.
By rights it should be quite a powerful pistol, I hope to try Jon’s 3D printed TP idea one day just to see what the potential is.
I think Webley got it right later with the Mk1, it’s got a comparatively skinny curved transfer port.

Glad it’s been of interest.

Cheers,
Matt

[ptdunk]

Discovered a recessed piston washer bolt and also a small recess inside the cylinder around the transfer port....this meant the last bit of air wasn't getting compressed.
Having sorted these out the fps has increased from a measley 220fps to a healthy 345 fps, doubling the power to 2ftlbs. Yay!
It cock's relatively easily but I wouldn't want to fit a stronger spring.

I was intrigued to try Shedtuner's idea, but getting a cad drawing and 3d print made could take a while so I went oldschool.

I bent a brass tube I.D of 27mm (filled with sand and crimped at the ends so it didn't flatten) and packed out the recess with modelling wax which is quite hard when cool.

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So that was pretty much as good as I would get it.
Surprisingly it made no difference to the power, I tried it both before and after I had sorted the lost air issue and both times it was about 10fps less than the original setup. I've refitted the original configuration and am happy it's now shooting to it's potential.

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I think the shaped brass block protrudes in quite far, so the channel is thinner at the top of the arc than the sides, maybe this effects the airflow?

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Maybe another example of century old airgun pioneers getting it right first time, I'm going to study Edwin Anson a bit more, this is the only pistol by him I have.

Well that kept me busy for a bit....

Cheers,
Matt

[Shed tuner]

interesting, shame it didn't improve things as you did such a great job !

so many variables in play though... I'd guess in this instance the piston mass (or spring preload) is such that the increased back pressure is causing the piston to stall earlier