Bulldog Props M38 & M19 Resin Scope Project

Bulldog44

Well-Known Member
RPF PREMIUM MEMBER
Started this on the FISD but thought to share this here with another great prop making community. Also hoping to learn from members here about casting props and ways to improve my project.

My initial goal was to make scopes hollow to easily add lenses. Just going to post up several update sheets I made along the way. Feel free to add comments or advice.
Also many thanks to the people who sold me these scopes along the way, members from here and the FISD for their knowledge & support to get me started and the people who helped move this project further by purchasing a trail kit last summer.


Starting point in 2016- M38 Scope
0M38%20Scope%20Project%20Promo%20Sheet_zps6ntmrrab.jpg


Version 4 Mold-
cope%20Parts%202016%20V4%20Test%20Pull_zpshzlsjyah.jpg


M38%20Scope%20Parts%202016%20Revised_zpsohfelyop.jpg


Decided to cast the prism cell too to make assembly more accurate-
0Parts%202016%20Prism%20Cell%20Casting_zpsd0ennqtu.jpg


Parts%202016%20Objective%20lens%20Test_zpskgo4mevu.jpg


Another 1942 M38 Scope-
M38%20Scope%20Number%202%20Test%20Cast_zpsgwknhhqo.jpg


Both Scope side by side-
ope%20Parts%202016%205%20and%201%20kit_zpsixuowehq.jpg


A third M38 scope made from mold using better silicone- ( was having shrinkage problems with the previous silicone)
cope%20Model%206%20First%20Test%20Cast_zpsfp53v48r.jpg


M19 First Trial-
02016%20M19%20Scope%20Casting%20Trials_zpszmtzmuph.jpg


19%20Scope%20Disassembly%20with%20Bulb_zps1e5g7ckm.jpg


Test casting of the light socket bulb-
0Socket%20Bulb%20Test%20Casting%202017_zpssio0j0st.jpg


Recent Test Casts of the M3 8 and M19 from the new molds using Smooth On Onyx Slow-
0amp%20M19%20Smooth%20On%20Onyx%20Test_zps7gmcejjs.jpg


Hoping to sort out casting problems using onyx but overall I am happier with the progression of the project. M19 light socket bulb still remains a huge challenge to cast but battling the bubbles is my first priority for both scope models. Thanks for stopping by. :)
 
I have had poor luck casting the clear socket bulb for the M19. Riddled with bubbles. I had some great advice from a member on the FISD but unfortunately it involves vacuum chambers, and pressure chambers, both of which I do not have or can afford to buy at the moment.

Has anyone ever worked with UV clear resin? Is it reliable to cast bubble free?

Also, does anyone know of a person or place who may be able to do high grade casting of the light socket bulb for me? I really want this part of my kit to be a nice as possible. My last test cast with Pro crystal resin ended up with more bubbles. Still need to try a few more ideas but it seems pointless if I don't use a vacuum & pressure chamber.
Any help is greatly appreciated.
 
Attempted another go at casting the clear light socket bulb from my M19 and had slightly better results. I was able to get one near perfect cast out of the 10 molds I made. The odds are terrible but its better than what I was getting. For my latest attempt I researched a bit on you tube and picked up a few tips to limit bubbles. I learned that I needed to stir the 2 part liquids much slower and use a mixing stuck tat doesn't hold any moisture ( no wood Popsicle sticks basically). Also I purcahsed a small heat gun. After mixing is finished I pour the mix into a shallow pan so the resin can spread out while I apply heat to the surface. I kept applying heat for about 2-4 minutes until I noticed the resin looked very clear and free of the tiniest bubbles. Then I used a syringe to inject the resin into each mold. This sort of worked but hard to tell if air is still trapped in the mold or not. Takes almost 3 days for the resin to cure, quite disappointing when it fails. :cry Trying again tonight!
 
Looks amazing! Will you be offering these as kits?

For the clear part, you could try using pour on epoxy coatings, made for tabletops and such. They tend to be pretty bubble free and are less susceptible to moisture. Long cure time, but nothing close to 3 days anyway.

Also, pressure casting really isn't that difficult or expensive (especially easy if you have a slow curing resin!). All you need is a compressor and a paint pot. Not sure where you're located, but you can pick up a cheap paint pot/pressure tank in the US for around $100. You don't need a particularly mighty compressor if you don't need to reach high pressure quickly, so the slow resin helps here. If you do try this, make your molds under pressure too. If you don't invisible bubbles in the rubber will compress and you'll get dimples and bumps. It's also quite capable of crushing hollow master patterns that aren't sturdy enough, though that wouldn't be an issue here. ;)
 
You might also look into casting the clear parts in Smooth-On 325 or 326 - both cure clear within an hour or so, I've had pretty good success with them for clear or tinted parts - they tint well for both translucent and opaque parts with the proper Smooth-On dyes. I even use them with a black dye in place of the Onyx - found that Onyx cured too quickly, even the Slow. And pressure is the sure-fire way to get bubble free, but with the 325/326 I find that they still do much better than other "clear" resins I've used without pressure, including the 24 hour stuff.

Hope this helps, best of luck, I've enjoyed following your progress!
 
I don't suppose there's a source for clear glass or plastic marbles or hemispheres of the right size, thus eliminating the need to cast altogether?
 
Re: Bulldog Props M38 & M19 Resin Scope Project

My deepest apologies for ignoring this thread. I subscribed but had received any messages that members posted here. I have attempted a few things to get the bulb casted but nothing with the results consistent or nice enough to move forward with. My best hope is to find a company who can make these with injection molding.

NX resin I used is good for quick curing, outer surfaces are smooth but inside is riddled with bubbles. At this point, its my best option if people are okay with how they look.
The Pro Crystal resin gives mixed results, I remove the main bubbles with a heat gun, inject with a syringe and get nice casts but there is always a large hole left somewhere. Tried pouring in the two mold halves too and removing bubbles before curing( 1 hour after mixing) but still getting surface holes. Last test results back tonight.This lastest test I waited 2 1/2 hours before sealing the molds together. Should be cured when I get home ... I hope.

Looks amazing! Will you be offering these as kits?

For the clear part, you could try using pour on epoxy coatings, made for tabletops and such. They tend to be pretty bubble free and are less susceptible to moisture. Long cure time, but nothing close to 3 days anyway.

Also, pressure casting really isn't that difficult or expensive (especially easy if you have a slow curing resin!). All you need is a compressor and a paint pot. Not sure where you're located, but you can pick up a cheap paint pot/pressure tank in the US for around $100. You don't need a particularly mighty compressor if you don't need to reach high pressure quickly, so the slow resin helps here. If you do try this, make your molds under pressure too. If you don't invisible bubbles in the rubber will compress and you'll get dimples and bumps. It's also quite capable of crushing hollow master patterns that aren't sturdy enough, though that wouldn't be an issue here. ;)
Thanks Pedro. Yes, I will be offering these as kits very soon. I am waiting on some fasteners from ebay to arrive and then start to see if the parts I have casted are worthy to sell. I would hate to sell scope kits with major defects. Make a simple assembly manual, got the packaging ready,.. almost there!
I will look into the vacuum chamber and pressure pot stuff once I get more funding. I am in Japan and limited on space and money at the moment so I can't go down the pressure pot route yet. I am interested to try your suggestion using epoxy coatings.

How did the new casts come out? I am in the market for two repro light sockets... ;)
Sorry for the long wait to hear how things went. I hope I can make these as nice as possible to offer them to you. Fieldmarshall will probably be making these too and will probably be perfect copies. I will keep trying to make these as nice a possible for you. If you want any of the ones I have now, happy to just send them to you. No problem. Just PM me your mailing address.


You might also look into casting the clear parts in Smooth-On 325 or 326 - both cure clear within an hour or so, I've had pretty good success with them for clear or tinted parts - they tint well for both translucent and opaque parts with the proper Smooth-On dyes. I even use them with a black dye in place of the Onyx - found that Onyx cured too quickly, even the Slow. And pressure is the sure-fire way to get bubble free, but with the 325/326 I find that they still do much better than other "clear" resins I've used without pressure, including the 24 hour stuff.

Hope this helps, best of luck, I've enjoyed following your progress!

Thanks! I will look into Smooth on Clear. They sell in here now but super expensive. If I get some cash freed up I might give it a try. Still have a lot left of the other clear resins to finish off yet. Cheers! Appreciate the help.

I don't suppose there's a source for clear glass or plastic marbles or hemispheres of the right size, thus eliminating the need to cast altogether?

Good idea. I am a sucker though for wanting to cast from all the original parts so its as close as possible. Definitely going to keep this mind. Thank you for your idea and help,

- - - Updated - - -


Thanks for posting this link. I am using these domes for the lenses incase the builder wants to use them or use their own found lenses. I will have a think about this for the bulb replacement. Cheers.
 
Just some of the packaging ideas and manuals I hope to include in the kit. Manuals were made in MS Publisher and Pixlr. I have no CAD draw skills so its all I could do for now. The fasteners in the kit are not perfect replicas of the originals but as close as I could find to buy. Fieldmarshall makes perfect replicas for all the exterior fasteners. Check out his thread to see those. Awesome mounting screws. The only part I am considering to get custom made would be the adjustment pegs found behind the mounting plate on the M38. They appear from the holes to be flathead screws but their shafts have no threading and they shafts are off centered from the fillister style peg head. Guessing these were just functioning to help center the smaller lens housing for a precise focused view. How much these will cost to be made might be more than the kits even worth.LOL.

M38%20amp%20M19%20Scope%20Kit%20Packaging%20Insert%20Production_zps2la3rzkp.jpg


Scope%20Kit%20Instruction%20Manuals%202017_zpssboyqubj.png
 
That's really an impressive project, very well done.

The package gives it that extra touch.

I think I had more fun working on the packaging. The casting has had many ups and downs. Don't even want to think about the money I invested and wasted with my mistakes. I really want the buyer to feel like they are getting a quality scope kit and the packaging hopefully reflects that. Thanks for your comments.
 
Better news on the bulb casting-
M19%20April%202017%20Light%20Bulb%20Casting%20Test%20Results_zpskufpewzs.jpg


This was going to be my final try at making these if the bubble problem continued but to my surprise most of the bulbs casted extremely clear and free of bubbles. In my second trial I joined the two mold halves together roughly 30 minutes after pouring (this clear resin has a pot life of 100 minutes). Before joining the molds I removed the major bubbles with a toothpick. Everything seemed good. I then allowed the molds to be heated to speed up the curing process for about 6 hours but after two days of curing I found that there were still tons of bubbles.

Trial 3 - I poured the resin and planned on joining the molds after an hour wait but I fell asleep on the floor and awoke 2 hours later! Luckily the resin was still gooey so I removed any noticeable bubbles then slowly joined the mold haves together. I did not heat dry the molds this time and let them sit for 3 days. The bulbs came out looking really nice but somehow I must have mixed the ratio of A:B resin incorrectly, so the bulbs have cured in a slightly flexible rubberlike state. I can live with that for now as long as they cast bubble free consistently. 7 out of 9 bulbs casted well!

smile.png
Going to try the same steps in trail 3 tonight but now I have a more accurate scale to ensure a better resin A:B ratio. Just a half a gram off and the results can change. Trail 4 here we go!

Hope all this casting jargon is interesting enough to post. Its exciting when things start to point in a positive direction after so many disappointments. Thanks for stopping by!
 
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Trial 4 Complete. I tested my latest method for casting the bulbs and pleased to announce it was successful! All 6 mold produce very clean and almost very clear bulbs. A bit foggy compared to the real one and I can see mirco bubbles here are the but nothing major. Also the resin cured to stable solid state. Back in business on the M19! This was surely the back breaker for me and I hope I can continue making these with success. It just takes a lot of time and patience. Thank you all who chimed in for your advice and help both here and on the FISD. Its your interest and help that led me to keep trying. Thanks once again!

Now back to work on these kits. Big casting day ahead! :D
 
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