Protector scopes

[Mrs Vampire]

Hi Brian

I suspect the pistol port protectorscopes in the M5 etc are the same. The drivers and gunners protectorscopes in the M5 etc are quite different to the Stuart Drivers and Bow gunners scopes.

The pistol port scopes I cast are optically perfect if I put in enough work to flatten them of and polish them . The issue is that I have no desire to put in the twelve to fourteen hours necessary to do to the six pistol port scopes when I can pay sixty dollars and get acrylic sheet professionally cut and polished.

The drivers and gunners periscopes on the M5 etc are all standard 346 https://www.marstar.ca/dynamic/produ...roductid=82590

of which the Stuart had One up until the late production M3A1s which had two in the turret .

The pistol port Protectorscopes are quite different and so far as I can find unavailable.

The M3 turret had a direct vision "peep" hole system that consisted of a thick piece of flat glass. The later M3 hybrid and M3A1 turrets had a periscope like device instead.


The driver and Bow Gunners Protectorscopes are made up of two mirrors and two windows all of which are separate components and separately replaceable .
I don't have part numbers for any of the components either for Pistol ports or front hatch scopes.

[BCA]

Gina; In your figure sheet 2 of 4, is item A, "glass". I am pretty sure this is an item that have NOS: mine are plexiglass, 5-7/8" long, 3/4" thick, maximum width 2-1/4" with the polished faces being 1-5/8" x 5-7/8". They are different than the glass pieces that you posted earlier in photographs. PM me for more info or with an email where I can send you a photo.

[Mrs Vampire]

Progress on the Pistol Port Protectorscopes.

I rate the clarity at around 85% . I can see through them but not well enough to read my computer screen. I can certainly recognize someone at a distance of twenty feet though.

the first two are pictures with mirrors attached the third the extrusion I had made . It all looks remarkably clear but viewing acrylic sheet coupled with the slight distortion of the two polished faces means a less than optically pure result.
It is good enough for a view port in non combat situations and the costs of getting an optically perfect scope are not worth it .

So that's my limit on these tricky gadgets.

[Mrs Vampire]

I have now assembled my prototype using super glue...

I was advised against this but I threw caution to the wind.

Clarity is improved to near perfect when the entire face of the mirror is covered and all air bubbles excluded.

The suggestion of Canada Balsum would also be a very good fix...but I am impatient and the only supply is from E-bay

There are also a number of UV activated lens glues available but I have no experience with them and they are expensive when I consider the number of mirrors I have to mount.

The issue it seems is the distortion caused by the gap between the mirror and the prism. I worked it out and light has to penetrate fourteen surfaces from object to eye....lots of opportunities for distortion.

[Mrs Vampire]

Protectorscope perfection

Using Acrilifix glue to hold the acrylic mirrors onto the shaped acrylic sheet I have achieved perfect clarity.

My protectorscopes are absolutely clear and usable as original....very very satisfying. Not much trouble to make sure all the air bubbles are squeezed out and the glue goes right to the edge.

This project is done

[Mrs Vampire]

Steve asked me if

"using the "acrylafix " to bond mirrors onto cast resin prisms would produce the same results as bonding mirrors to the acrylic sheet extrusion I had made?"

The answer is definitely yes!!

I bonded two acrylic mirrors to the best of the cast resin prisms I had made. It instantly improved the optics to usable clarity. The only reason they were not perfectly clear was that I had abandoned the cast prisms before I had ground the surfaces to dead flat.

Had I flattened them I am sure I would have produced the same results I have achieved with the extrusion I purchased.

I am unsure how effective this would be if I used glass mirrors but have a very strong feeling that if the "acrylifix" would bond to glass the results would be the same.

Brian also recommended Canada Balsum . I have a similar feeling about that as a bonding medium . That is if it will bond perfectly to both the mirror and the prism "whatever they are made from, then a perfectly optically clear scope will result. My only reason for not using Canada Balsum was that It would take a while to get it to me from an e-bay supplier.

I think if anyone was undertaking scope building then an experimental cast up and bonding would qualify the mixture of products selected.

What I am able to say is that using acrylic sheet , acrylic mirrors and acrylifix produces very clear scopes and that if clear casting resins are used the same results are obtainable so long as all surfaces are sanded/ground dead flat.

[Mike Cecil]

Good job, Gina! Well done.

I admire your skill and your perseverance in the pursuit of excellence.

Mike

[Douglas Greville]

Gina

The ongoing problem with the prisms always appears to be the glue
either shrinking or yellowing.

This is something that has plagued US military periscopes and episcopes and
still does. I have seen NOS ones still sealed in their hermetic packets that the glue had started debonding or/and yellowing. Most seem to go no more than 2 years out of the wrapper before they go yellow.

However, I note that I have seen Churchill, Ferret, Saracen and Centurion scopes that were as perfect optically as the day they were made. Most had been in a vehicle or sitting unwrapped on a shelf all that time. So whatever it is that the British are doing and have always done works.
I would like to find out what it is?

The ultimate test of your acrylic glue will be how it withstands normal daylight. This is also the reason why the normal UV setting glues cannot be used for optics. They are fine for home craft work for something that spends its life indoors.

Regards
Doug

Originally Posted by Gina Vampire

What I am able to say is that using acrylic sheet , acrylic mirrors and acrylifix produces very clear scopes and that if clear casting resins are used the same results are obtainable so long as all surfaces are sanded/ground dead flat.