My Mercury Ratting Rig

[T 20]

No recess, I've put up a picture here:
https://www.airgunbbs.com/showthread...s-wanted/page4

image.jpeg



Thankyou for that, Evert.

Mine isn't like that at all and unfortunately your photo has highlighted another problem, I'd been under the false impression that my cylinder was from a MK4 or even an S but with a single piece cocking arm added.
Looking at your picture and cross referencing the Mercury parts diagrams it would appear that my cylinder is off a MK1 or MK2 as it has one central bolt holding the fore end screw bracket not two a shown in your picture --- bugger.

that looks way too easy to remove for Mick to resist...

In view of the above it may not be that simple, Jon.

I'll have to get my magnifying glass out and inspect the cylinder joint for braze.

Something else that this has highlighted is the fact that folks having their later Mercuries reblued run the risk of creating a porous breech in their cylinder by the hot bluing breaking down the sealing compound on the breech plug threads.
Ideally, to have a Mercury reblued I'd be looking at getting the plug and cylinder blued separately and then assembling them with Loctite afterwards.





All the best Mick

[T 20]

The more I stare down this cylinder the more I think WTF. :-

image.jpg


It doesn't unscrew either, I reckon the plug was welded onto the cylinder on these earlier guns --- I've had this red hot and it won't budge.

[Shed tuner]

are they radial grooves around the outside ?

[crowbar]

I was hoping it would all work out. I have just checked my Mk2 and Mk4 Aisporters with a magnifyer they are both brazed.

[T 20]

are they radial grooves around the outside ?

It certainly looks like a radial groove round the outside of the plug, Jon.

The groove and the hemispherical cutout in the middle of the plug goes a long way to explaining why this old girl won't pick her heels up and she feels slammy.
As the transfer port is drilled into the hemispherical cutout I'm wondering if it was deliberately made that way in a Zephyr type style ?

A few cures spring to mind but I'm still thinking about it.



All the best Mick

[T 20]

I was hoping it would all work out. I have just checked my Mk2 and Mk4 Aisporters with a magnifyer they are both brazed.

Don't worry, if I have to scrap the Mercury cylinder none of my machining will go to waste as everything I've made will drop into my Airsporter S.

Funny you should mention the Airsporter MK4 as one of the cures I'm contemplating for this Mercury cylinder is to machine the end plug out of it, machine it flat and then weld it into a spare Airsporter MK4 cylinder I have.



All the best Mick

[Shed tuner]

A few cures spring to mind but I'm still thinking about it.

reckon you could JB weld it all up in there, smooth it off and redrill the port ? Or just melt a load of solder down it ?
would be so much easier if you could get the bugger off !

[TonyL]

would be so much easier if you could get the bugger off !

Yep, and just think of the possibilities then, with your engineering prowess, Mick.

In a similar fashion to how you lovingly conjured up the HW35/LGV.......take the breech assembly and attach a tube to sleeve down to 24mm. The perfect breech join achieved by pre-assembling the breech to comp tube will guarantee against any voids or leaks and the perfect tube will provide the ideal environment for 'O' ring employment........In for a penny, in for a pound.

[lightning22]

Don't worry, if I have to scrap the Mercury cylinder none of my machining will go to waste as everything I've made will drop into my Airsporter S.

Funny you should mention the Airsporter MK4 as one of the cures I'm contemplating for this Mercury cylinder is to machine the end plug out of it, machine it flat and then weld it into a spare Airsporter MK4 cylinder I have.



All the best Mick

In 50 years time airgun collectors of the future will be arguing about the phase in its history when the Airsporter became a breakbarrel..

[T 20]

reckon you could JB weld it all up in there, smooth it off and redrill the port ? Or just melt a load of solder down it ?
would be so much easier if you could get the bugger off !

It worse than I thought, Jon.

Having another poke around in the cylinder revealed that it isn't just a radial groove round the outside of the plug --- it's has a radius round the end of the plug the same as the radius on the front of the piston.

Then there's a radial groove behind that section.


By a quick calculation :-

The transfer port has a volume of 0.078cc

The plug radius has a volume of 0.176cc

So the total lost volume is 0.078 + 0.176 = 0.254cc


The swept volume of the cylinder is 43.12cc

So the static compression ratio is 43.12 /0.254 = 170:1

That figure doesn't include the full radial groove behind the radius or the hemispherical cutout in the front of the plug, so I reckon the static compression ratio is nearer to 100:1 --- no wonder it was getting slammy.


It's an absolute knacker, but I'll give it some thought.



All the best Mick

[T 20]

In 50 years time airgun collectors of the future will be arguing about the phase in its history when the Airsporter became a breakbarrel..

I must admit, that aspect of doing it did appeal to me.

Another evil thought just crossed my mind, I could machine down a HW80 breech and fit that to the Airsporter cylinder --- that'd make future collectors scratch their heads.

A HW80 BSA Airsporter break barrel imported by Hull Cartridge.

[Shed tuner]

eash, that's never going to shoot nice.

messy bodge idea: machine a nice flat disc to fit the cylinder bore, smatter gobs of jb weld on one side, insert it with the piston to keep it true, stick the mainspring and block in there and tighten it all up to ram the JB weld into all the holes, and hopefully force as much air out as possible. the disc stay in place permenantly, forming the new cylinder end. When all set, drill a new port, and hope. I mean, it can't really be worse, can it ? Should only cost you 2mm in stroke/ tp length.

[TonyL]

Beat me to it, Jon.

[evert]

It worse than I thought, Jon.

Having another poke around in the cylinder revealed that it isn't just a radial groove round the outside of the plug --- it's has a radius round the end of the plug the same as the radius on the front of the piston.

Then there's a radial groove behind that section.


By a quick calculation :-

The transfer port has a volume of 0.078cc

The plug radius has a volume of 0.176cc

So the total lost volume is 0.078 + 0.176 = 0.254cc


The swept volume of the cylinder is 43.12cc

So the static compression ratio is 43.12 /0.254 = 170:1

That figure doesn't include the full radial groove behind the radius or the hemispherical cutout in the front of the plug, so I reckon the static compression ratio is nearer to 100:1 --- no wonder it was getting slammy.


It's an absolute knacker, but I'll give it some thought.



All the best Mick

I'm just happy to see that I'm not the only one who runs into problematic receiver tubes.

[T 20]

I'm just happy to see that I'm not the only one who runs into problematic receiver tubes.

To be honest, Evert.

Your tube fault I could happily accept on an old gun as the sealing compound had broken down with the passing of time.

My tube tells a different story, it shows a manufacturer who couldn't give a toss about the product they were making or how the finished gun would perform.


I've never come across anything like this before.




All the best Mick