Webley Osprey Barrel

[evert]

When I machined an Osprey piston to take the HW seal, I THINK I machined it back a bit to retain most of the stroke.
But it is some years ago so I dont remember the details clearly.
Anyway, the transfer port was sleeved and the gun did not loose power.

[T 20]

When I machined an Osprey piston to take the HW seal, I THINK I machined it back a bit to retain most of the stroke.
But it is some years ago so I dont remember the details clearly.
Anyway, the transfer port was sleeved and the gun did not loose power.

Hi Evert.

To fit a HW seal and retain the standard stroke on a Hawk/Osprey piston, you have to machine the thickness of the front face of the HW seal (@ 4mm) off the front of the piston before machining the arbor.
If you don't machine the 4mm off the front face before machining the HW arbor you end up short stroking by 4mm like the piston in this thread.
Without brazing or welding this piston arbor up you can't remachine the arbor 4mm further back to correct the stroke to standard, but you can machine the HW arbor down to take the shorter TX seal which will correct the stroke.

Anyway, this piston should be on its way to me today so I'll take some photographs of the process and post them here.




All the best Mick

[evert]

Hi Evert.

To fit a HW seal and retain the standard stroke on a Hawk/Osprey piston, you have to machine the thickness of the front face of the HW seal (@ 4mm) off the front of the piston before machining the arbor.
If you don't machine the 4mm off the front face before machining the HW arbor you end up short stroking by 4mm like the piston in this thread.
Without brazing or welding this piston arbor up you can't remachine the arbor 4mm further back to correct the stroke to standard, but you can machine the HW arbor down to take the shorter TX seal which will correct the stroke.

Anyway, this piston should be on its way to me today so I'll take some photographs of the process and post them here.




All the best Mick

I really dont remember any more what I did, but remeber some thinking around how to combine the existning grooves for the Ospreys piston rings with the arbor profile for the HW seal.

[T 20]

Well folks, Toni's HW seal converted piston arrived at T 20 towers today and as he says it has a 4mm shorter stroke than standard :-

image.jpg


Toni's piston didn't have the necessary 4mm removed from the front face before the Weihrauch arbor was machined :-


image.jpg


The only slight concern in machining the Weihrauch arbor down to a TX arbor is the thin wall between the Weihrauch arbor and the original Osprey's piston ring groove :-


image.jpg


Having thought about this, I've decided to remove the wall completely and glue an oilon bearing in the original widened Webley groove and then machine the arbor to suit a TX seal.
Though I probably need to measure the back diameter of a TX seal before I commit to this as I could be worrying about something that will be perfectly OK.






.

[evert]

I really should get the piston out of my converted Osprey to see what I did...
IF I remember correctly I machined away the front goove and used the remaining wall for the head in the HW style arbor.

The one you are working on has too much metal removed to do that, so the TX/Diana seal is probably the best option.

[T 20]

I really should get the piston out of my converted Osprey to see what I did...
IF I remember correctly I machined away the front goove and used the remaining wall for the head in the HW style arbor.

The one you are working on has too much metal removed to do that, so the TX/Diana seal is probably the best option.

I gave my spare Hawk piston converted to HW seal to BBS member HW777, as I wasn't well enough at the time to convert the one he sent me.
From memory I'd machined past both piston ring grooves, which are within the first 9mm of the piston head so I'm happy that I sent John a good one --- it was probably longstroked slightly as well knowing me.

[ToniD]

I am so glad that you chaps know what you're talking about.
Well over my head.

Is long stroking a bad thing too?

Toni

[T 20]

I am so glad that you chaps know what you're talking about.
Well over my head.

Is long stroking a bad thing too?

Toni

Hi Toni

If you longstroke a gun you increase the amount of air that's compressed by the piston as the gun has a longer stroke.

This can be done to increase the gun's power or change the firing cycle, I know that the Webley Hawk 2/3 will longstroke, but I don't know about the Osprey.
The deciding factors on whether a gun can be longstroked is if the working cylinder can support a stroke increase and whether the cocking linkage will work through a longer distance.
Without having an Osprey here to measure I'll be playing safe this morning and machining your piston to take a TX seal, working at standard stroke length.




All the best Mick

[ToniD]

Thanks Mick,
I have had that explained before, but at last, that explanation made sense to me.

Cheers,

Toni

[T 20]

Good news, Toni --- the operation on you piston was a success and the patient is now awaiting transportation home.

I hope to get to the post office this afternoon.



Before :-


image.jpg


After :-


image.jpg


After - with TX seal and Webley piston ring to act as a bearing :-


image.jpg


With the TX seal fitted the piston should be within 0.5 mm of standard piston length.




All the best Mick

[ToniD]

Wow!
Thanks Mick,
I shall be putting it all back together this weekend as my new seal should be with me by then. You sir, are a gentleman!

Toni

[T 20]

Wow!
Thanks Mick,
I shall be putting it all back together this weekend as my new seal should be with me by then. You sir, are a gentleman!

Toni

No problem at all, Toni.

The only tricky part was avoiding taking any material off the thin wall between the TX seal and Webley seal groove --- I managed this by painting the thin wall with white paint.
As soon as I saw white paint on the cutting bit I knew I was on the final cut.

On fitting a TX seal I found the seal was 26mm OD so I fitted the seal to a genuine TX piston and found that to also be 26mm OD so I'm happy that everything is correct.




All the best Mick

[evert]

On fitting a TX seal I found the seal was 26mm OD so I fitted the seal to a genuine TX piston and found that to also be 26mm OD so I'm happy that everything is correct.




All the best Mick

Is that a Cometa seal, or do the AA seals come oversize?

[T 20]

Is that a Cometa seal, or do the AA seals come oversize?

That's the genuine TX seal which measured 26mm fitted, Evert.

The John Knibbs website gives the diameter as 25.75mm, if that's before being stretched onto its mounting that would seem about right.
I was a bit worried that I'd cocked up machining Toni's piston so I fitted the seal to a TX piston and it measured the same at 26mm.

1mm (40thou") of crush seems a bit excessive to me but the TX seal has a very thick lip to enable it to be sized down without any problems.

Toni is using an aftermarket TX seal, so all I could do is replicate the TX dovetail arbor on his piston for him.




All the best Mick

[Thegreg]

Hi Toni

If you longstroke a gun you increase the amount of air that's compressed by the piston as the gun has a longer stroke.

This can be done to increase the gun's power or change the firing cycle, I know that the Webley Hawk 2/3 will longstroke, but I don't know about the Osprey.
The deciding factors on whether a gun can be longstroked is if the working cylinder can support a stroke increase and whether the cocking linkage will work through a longer distance.
Without having an Osprey here to measure I'll be playing safe this morning and machining your piston to take a TX seal, working at standard stroke length.




All the best Mick

You can get about an extra 2mm from the Tracker (assuming the same for an Osprey given the almost identical cardinal dimensions) without having to alter anything. Beyond that, IIRC about +8mm is achievable but with major works to the mechanics of the gun. The cocking slot can only accommodate so much, but after that the sear can be remade to alter the latching point on the piston.

They still shoot like turd, I wouldn’t recommend bothering! I love them though.

Cheers
Greg