My Mercury Ratting Rig

[TonyL]

Any progress on this, El Maestro?

[T 20]

Any progress on this, El Maestro?

I'm still on the case, Tone.

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The reason I haven't updated you is because of the simple fact that the Mercury Latchrod isn't long enough to reach the piston head so I'm having to machine the piston in three parts.
The top hat will have to be steel and form part of the piston head with the latchrod threaded into it in order to get the piston length I need.
The top hat section will have to be let into the piston from the front and welded in to keep everything nice and strong.

As I've just finished the latchrod my next job is to machine the piston head to length and bore through it at the spring ID then open up half the depth to a larger ID so that I can leave a step on it for the top hat to sit in.
The idea is that the step stops the top hat pulling through the front of the piston --- once this is all set to length I'll weld the top hat in.

This lot would all be easier to explain with pictures which is why I haven't posted for a day or two.




All the best Mick

[T 20]

The top hat will have to be steel and form part of the piston head with the latchrod threaded into it in order to get the piston length I need.

This lot would all be easier to explain with pictures which is why I haven't posted for a day or two.

Like this :-

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Next up the piston body will need finishing to final size while I still have a hole in the front of it for the revolving centre to run in --- then I can weld the top hat in.

[TonyL]

Nice work, sir.

[T 20]

Next up the piston body will need finishing to final size while I still have a hole in the front of it for the revolving centre to run in --- then I can weld the top hat in.

Well that wasn't quite the right order as I missed a step out.

I finished machining the piston body for now and machined the front to let the top hat in. :-

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Now this isn't quite ready for welding as I have to put a V groove on the weld line for maximum weld penetration.
But before I get the welder fired up I need to cut the cocking lever slot in the piston as it'll be much easier to do now without the latch rod in.

I was aiming for an all up piston weight of around 275 grams --- As it stands now the piston components weigh in at 290 grams.
Cutting the cocking lever slot will remove between 13.3 to 14.8 grams depending on how long I cut it so I hope to end up between 275 and 280 grams, this will be tried in the gun at this weight for testing.
I could make further weight reductions by fitting Delrin bearings but I will be trying as is for now to see if any further work would improve things --- I am considering increasing the stroke a tad depending on what this piston does.



All the best Mick

[evert]

Impressed by all the piston work you've been able to turn out the last weeks!

[TonyL]

Fine work indeed.

[T 20]

Impressed by all the piston work you've been able to turn out the last weeks!

I find that making Pistons is a bit of a challenge and also a time consuming pain in the neck.
But, once I got into the mind set of making them it made sense to carry on and make all the ones I needed in one long lathe session.

The Mercury piston came about by accident due to the firing cycle of my Original 35, the Mercury piston is being made to a 70mm stroke, but I've left the option to long stroke it to 80mm with this piston if needed --- I'd just have to machine 10mm off the back of the top hat.



All the best Mick

[T 20]

Completed piston :-

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That's 45grams less than a factory piston.



And my welding :-

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I may tidy this up at a later date as I couldn't be arsed to sharpen my lathe tools.




Next up is a custom Spring guide from 316 stainless steel --- this will actually be a bit more involved than it sounds.
On cocking, the back of the piston hits the threaded block on a Merc which acts as a stop, as my piston is shorter than standard then the base of the guide will have to extend into the cylinder to act as the piston stop.
So besides having to drill for the latchrod I'll have three different ODs to machine to act as a both a guide and a piston stop.




All the best Mick