My Mercury Ratting Rig

[Shed tuner]

I do find most guns shoot better with more spring room... I guess it reduces the differential between the cocked and uncocked loadings for a calmer acceleration.. pity you couldn't find a way to retain it without spacing it out... howsabout a sleave affixed to the end block, that abutts the piston skirt just after cocking ?

[T 20]

I do find most guns shoot better with more spring room... I guess it reduces the differential between the cocked and uncocked loadings for a calmer acceleration.. pity you couldn't find a way to retain it without spacing it out... howsabout a sleave affixed to the end block, that abutts the piston skirt just after cocking ?

I could easily keep the spring room, Jon, but I just don't want it.

The coilbound Spring height of the 28 coil HW95 Spring is 84mm, in my Original 35 I have the spring compressed to 100mm when cocked for 11.6ftlbs.
As I'm attempting to run the same bore, stroke, Spring and piston weight in my Merc it makes sense to keep the same spring room by way of an experiment.
Once I've finished machining the new Merc Spring guide I'll have 110mm of Spring room when cocked --- I've allowed 10mm for top hat and slip washers.
If I don't have enough Spring room I can easily machine 10mm off the guide to get to 120mm of Spring room when cocked.

I'll get a picture up when I've finished machining so you'll get a better idea of what I'm upto.




All the best Mick

[T 20]

I'll get a picture up when I've finished machining so you'll get a better idea of what I'm upto.

Here you go, Jon. :-

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The spring space inside the piston when cocked is now 110mm before slip washers.
The latchrod can't be forced into the Sears too far now as the largest guide diameter acts as a stop.
And the spring guide weighs in at 146grams which adds just 27grams to the overall weight of the gun.

It'll be a laugh if this lot don't work.




All the best Mick

[crowbar]

I can see that the large dia flange willl give more rigidity but what does the bit that goes in the piston do,would a flat face
from the large dia to the spring guide not work then you would have more room for spring tuning with doughty washers.

I would machine a two piece spring guide with the large back block drilled and countered bored and a standard type spring guide that fits through the back.

[T 20]

I can see that the large dia flange willl give more rigidity but what does the bit that goes in the piston do,would a flat face
from the large dia to the spring guide not work then you would have more room for spring tuning with doughty washers.

I would machine a two piece spring guide with the large back block drilled and countered bored and a standard type spring guide that fits through the back.

I'm working on the theory that 100mm of compressed spring room should put me in the right ballpark power wise, so the bit inside the piston is just to take up 10mm of the 120mm of spring room inside the piston and to add weight to the static part of the gun.
Effectively this piece takes up the space of 5 Dowty washers (which I'm running low on), if I find that I need more Spring room I can simply machine that 10mm piece off.
Another spring that I'll be trying out is a 25 coil HW99 Spring which will need even less Spring room than I have now --- basically I'm just leaving all my options open at present.



All the best Mick

[T 20]

It'll be a laugh if this lot don't work.

And --- it's complete crap.

After dieseling a couple of times the trigger blade snapped in half, which I've had happen before with the same trigger unit on an Airsporter S.
Once the gun settled down it gave a consistent 525fps over the chrono with Superdomes with 106mm of compressed Spring height.
So I took it apart and stuffed in another four preload washers in, cutting the compressed Spring height down to 98mm --- over the chrono it gave a very consistent 559fps with Superdomes for an earth shattering 10ftlbs and it was getting a bit slammy.

Now I don't think this low power and slam is down to the action --- I think it's down to the barrel.
Any type of pellet I have easily drops into the breech, some fall 3-4mm into the barrel as they're way too small for the rifling.
Strangely I didn't have this problem with the Mercury S I serviced the other week so now I think the low power could be down to the pellets setting off too early in the firing cycle.
I'll have a look through my spares in the morning and see if I've got a tighter barrel, if not I'll have to shelve the gun until a later 5.5mm barrel shows up in sales.
I was going to open the transfer port up to 3.2mm but with the lost volume in the barrel it could make things worse so I'll swap the barrel before modifying anything else.





All the best Mick

[evert]

Could it be a leaking/porous breech?
I had to screw the forks out of my mercury tube and put them back in with new thread locking glue to get it working properly.

[T 20]

Could it be a leaking/porous breech?
I had to screw the forks out of my mercury tube and put them back in with new thread locking glue to get it working properly.

I don't think it's porous, but that gives me an idea, Evert.

I still have that weird hemispherical chamber in the front face of the cylinder, if I unscrewed the forks I could lathe the front face flat, or MIG it up and then machine it flat --- I take it that they're Loctited in ?

Looking at the barrel again tonight, even FTT pellets drop into the barrel, but these were so tight in the Original 35 barrel that I gave up trying to use them.

I have a couple of .22" Meteor MK1 and MK2 barrels kicking about somewhere, I'll try some pellets in them tomorrow.



All the best Mick.

[TonyL]

Lots of areas for improvement then, Mick.

As you say, you have a good few areas of potential there. If everything seemed okay but the results just weren't coming, it would be much more confounding. I hope you find a barrel easily to hand in your stash.

[evert]

I still have that weird hemispherical chamber in the front face of the cylinder, if I unscrewed the forks I could lathe the front face flat, or MIG it up and then machine it flat --- I take it that they're Loctited in ?

Yes, there was some kind of glue, mine needed some heat before it could be unscrewed.