M38 Hollow Core Scope Project 2016 - Bulldog44

[Troopacoola[TK]]

Awesome Marc! Thanks for posting this. The scope looks cool with the light inside. Now your son is ready to blast those rebels with illuminated sight precision!

Yup! He's got a couple of years to get cleared though!

 

Marc

[Bulldog44[TK]]

Short Project Update-

 

 

 

Stared a few test castings of both scopes and parts-

• M38 testing well, very clean castings so far.  Hope to get all the parts casted a few times and test fit them. So far all the parts are 99% in proportion making it possible to screw the threaded parts on like the real scope with a little bit of persuasion  . 
• M19 testing at 90%, still getting large air pockets on one end of the scope. Good news, the scope is fully hollow inside- removed the inner reticle assembly and side light socket bulb before making the mold.
• Light socket bulb tests are promising but not satisfactory yet. Test casting with Pro Crystal 880, very clear castings only achievable using a syringe to inject the resin otherwise bubble heaven. Still not perfect though. Takes 2-3 days to fully cure due to the winter temperature here. Need a heat lamp to speed things up.
• Ordered another clear resin called Hobby Cast Resin NX that cures in 20-30 minutes. Trial that this weekend when it arrives. 

Pro Crystal 880 does not turn yellow over time and Hobby Cast NX does. That is the only drawback but the NX resin sounds easier to work with. 2-3 days wait sucks especially when you find out the casting failed. Report back my findings.  Thanks for stopping by!

[bpatneaude]

Are these available to buy? Thanks

 

Sent from my 2PYB2 using Tapatalk

[Bulldog44[TK]]

Are these available to buy? Thanks

Sent from my 2PYB2 using Tapatalk

Hi Brian. Yes, these will be offered soon. I am just working out some casting issues with some of the smaller parts. Once those issues are reduced I will start an interest list for both the M38 and M19 scope kits. Which one are you interested in?

[bpatneaude]

Both.

[Bulldog44[TK]]

Both.

Great. I will try to give a better assessment this weekend about kit sales. I am a bit slow making these so it might be a while. Hope to have good news this weekend for you and anyone waiting to purchase a kit.

[darthcue[TK]]

Great. I will try to give a better assessment this weekend about kit sales. I am a bit slow making these so it might be a while. Hope to have good news this weekend for you and anyone waiting to purchase a kit.

i can't hardly wait for this weekend!!! take your time Brian!!!

[Bulldog44[TK]]

i can't hardly wait for this weekend!!! take your time Brian!!!

Thanks. I know you have been waiting patiently and hope to get you a scope kit soon. The M38 scope kit parts seem to cast well with some minor trapped air pockets on the surface. The surfaces I am referring to are all the sides that face inside when assembled so they will not be seen. The visible surfaces for each part are perfectly fine. I just hate not being able to get these parts bubble free.  Looking into alternative methods to cast using syringes, hoping this will cut down on those air pockets. It  is a one shot deal, one you use the syringe it has to be tossed so its another item I will have to purchase in bulk. Using dollar store syringes now for testing, works well sometimes but not 100%. My molds need an extra spout for the syringe to be inserted so the air goes out the other spouts when I inject the resin. No room or cash for a pressure chamber so that is not in the cards at the moment. 

[kman[TK]]

Thanks. I know you have been waiting patiently and hope to get you a scope kit soon. The M38 scope kit parts seem to cast well with some minor trapped air pockets on the surface. The surfaces I am referring to are all the sides that face inside when assembled so they will not be seen. The visible surfaces for each part are perfectly fine. I just hate not being able to get these parts bubble free.  Looking into alternative methods to cast using syringes, hoping this will cut down on those air pockets. It  is a one shot deal, one you use the syringe it has to be tossed so its another item I will have to purchase in bulk. Using dollar store syringes now for testing, works well sometimes but not 100%. My molds need an extra spout for the syringe to be inserted so the air goes out the other spouts when I inject the resin. No room or cash for a pressure chamber so that is not in the cards at the moment. 

 

I wonder if a vibrating plate would accomplish the goal in a similar way?  A case tumbler (used to clean ammo casings for reloaders) is only $40.  Strap the molds on top and it might shake the bubbles right out.

 

Pure speculation, mind you.  Maybe it'll do the opposite... I don't know a lot about the molding process.  But it seems kinda logical.

[Bulldog44[TK]]

I wonder if a vibrating plate would accomplish the goal in a similar way?  A case tumbler (used to clean ammo casings for reloaders) is only $40.  Strap the molds on top and it might shake the bubbles right out.

 

Pure speculation, mind you.  Maybe it'll do the opposite... I don't know a lot about the molding process.  But it seems kinda logical.

Thanks Kman for the advice. I do use a similar technique when making my silicone molds. I use a small fish tank air pump to vibrate the mold to help release bubbles trapped near the surface of the item I am molding. I will try this tonight with the clear resin. I hadn't considered it because this clear resin I am using cures in 20-30min. Only 100 seconds pot life so I have to work quick. The bubbles might still be forced out with vibration as you suggest if I can get them filled before it gels up. Let you know how it goes. Appreciate the help. 

[Bulldog44[TK]]

Had a moment this weekend to try out the new clear resin I ordered for the M19 light socket bulb. First test casting did not go as planned. The Hobby Cast NX resin cures very quickly so I worked within the 100 seconds available before it gels. Either I got the unequally mixed parts A & B or the colder room temperature caused the resin to remain in a soft rubber like state. after noticing the resin looked soft past the 30 minute cure time, I used a desk lamp as a heat source to assist the curing process but to no avail. Last night I tried a second time using the desk lamp right after injecting the molds with resin. In short the cured as stated within 20-30min but riddled with air bubbles. Sorry, the photos below are from the first test. I will post the second test photos tomorrow if I get a chance.

 

 

At the moment I am still unsure how to cast this clear piece consistently and free of bubbles using either resin I bought. Any suggested ideas or methods are greatly appreciated. 

[QuartZ]

I know you said not to bring up pressure chambers, but as far as I know that's what it takes. Over at propsummit (a blade runner forum) we have had tons of trouble casting the clear grips without bubbles. A member DaveG had some of the best luck with the following method (quoting his post here):

 

"www.silpak.com 
RU-525 two part water clear polyurethane. Same stuff I used to make the amber grips for my Snub Nose Blasters.

 

It's a PITA to use. The mold has to be platinum based silicone, not the more common tin based. The resin needs to be first de-gassed in a vacuum chamber to get rid of the big bubbles from mixing and once poured into the mold left to cure in a pressure chamber at 80 to 100 psi to get a crystal clear result. After that it needs to be post-cured at about 125 to 150 degrees for 4 to 6 hours. And even then you'll get a lot of rejects."

 

 

Sorry if this didn't help you, but I just popped into this thread, saw how much you were struggling with bubble-free, clear resin castings, and we've been dealing with this issue for years over on that forum with very few real solutions other than something similar to what I've quoted from DaveG.

 

Best of luck,

-Dana

[Bulldog44[TK]]

I know you said not to bring up pressure chambers, but as far as I know that's what it takes. Over at propsummit (a blade runner forum) we have had tons of trouble casting the clear grips without bubbles. A member DaveG had some of the best luck with the following method (quoting his post here):

 

 

 

 

"www.silpak.com

RU-525 two part water clear polyurethane. Same stuff I used to make the amber grips for my Snub Nose Blasters.

 

It's a PITA to use. The mold has to be platinum based silicone, not the more common tin based. The resin needs to be first de-gassed in a vacuum chamber to get rid of the big bubbles from mixing and once poured into the mold left to cure in a pressure chamber at 80 to 100 psi to get a crystal clear result. After that it needs to be post-cured at about 125 to 150 degrees for 4 to 6 hours. And even then you'll get a lot of rejects."

 

 

 

Sorry if this didn't help you, but I just popped into this thread, saw how much you were struggling with bubble-free, clear resin castings, and we've been dealing with this issue for years over on that forum with very few real solutions other than something similar to what I've quoted from DaveG.

 

Best of luck,

-Dana

Dana, thanks a ton for sharing this. Its extremely helpful to get lots of info, especially casting with clear resins. I am still a novice at this and hearing how others cast their resin makes a huge difference. Those grips look amazing. to hear that it must go though that whole process and still have a chance of failure has certainly outlined how futile my attempts have been. Pressure casting seems the best and proper way to go for bubble free casts. Maybe I will have to consider building a pressure chamber in the near future somehow.

The resin I bought cures super quick so degassing might not be an option but at least some pressure would help during the curing process I think.

The part I am casting is quite small so nothing like those grips. Hopefully I can find a middle ground for now to get some casted without too many bubbles. Going to check out that RU-525 stuff but guessing its not possible to get here in Japan without paying a fortune.

Thanks so much again for your help. Now I know its not just me making a mess of things and see its quite common to battle the bubbles.

Chime in anytime you see something I might be doing wrong or could try alternatively. Cheers!

[Bulldog44[TK]]

Test Casting with Smooth On Onyx Slow Cure

 

 

I was able to get some black onyx resin from the Smooth On distributor here in Japan. The distributor sold me a trial kit at a discounted price because the kit has passed its shelf life date. Started with 2 tests this weekend to see if this is the way to go. It is really nice to get pure black casts but because the resin mixes have expired, they seem thicker than they should be making it harder to get the resin to slush around the mold and fill the areas prone to trapping air.

 

First test was a disaster, second test much better. I had to try an alternative way to pour the resin into the mold since it was too thick to use my normal funnel method. Still some major air pockets in the M38 but the M19 casted well. Lots of tiny bubbles though so getting clean casts might not be possible until I get a fresher set of resin mix. I like this stuff though quite a lot and if I can get a few more casts with less trapped air, I will probably use this for my future kits.

 

Speaking of kits, I am sorry I did not post any major news on when I will start selling these again. I am looking at having limited kits available by the end of January but warn that these kits will probably not be free of the bubbles. After tireless research, I would have to make some major changes in my mold designs, buy a vacuum chamber for the silicone and a pressure chamber for the resin to get near perfect casts. With my limited living space and budget for this project, I will just try to keep my current method going and find better solutions to reduce the air being trapped. The great thing this time around is that the parts will mostly fit with higher accuaracy, almost no issues with shrinkage to the molds. 

 

Hoping to design some packaging inserts this week so all the kits can be packed more efficiently. My kids have volunteered to help me make more boxes for future kits, I promised ice cream for labor! Updates to come soon I hope. Stay tuned!

Edited January 16, 2017 by Bulldog44

[R2Chris[TK]]

Thank you for the update Brian.  You have certainly put a lot into this project.  Keep up the good work!

[Bulldog44[TK]]

Had a few more test runs this week and the results are mixed regarding the Smooth On Oynx. I am sure this is because the resin mixes are expired and not as fluid as they should be. Part A mix is already thick and my mixing time needs to be less than 30 seconds, half of the recommended time of 60 second. This makes it harder to get the resin to cover the mold walls and tight spots before the resin starts to gel up and bubbles get trapped.

 

Moreover I have found that the retainer rings are too rigid after they cure making it difficult to screw them onto the scope. A little flexibility is best for these delicate parts so I am considering to cast the smaller parts in the same resin I was using before. The onyx resin also seems to expand more on the surface than the previous resin used maybe due to less surface tension. I am getting raised areas on the reverse side of the rings were they should be flat. The only drawback so far is that it will not be the exact deep black color of the main scope body. The M38 large ring and lens assembly are still the only two parts that do not fit as nicely as I had hoped. I still must remind myself that the real scope rings and lens assembly fit really tight when they are screwed on. So in conclusion, these parts will require some delicate sanding of the threads so smoothly screw on. 

 

Hope I can get some fresh Smooth On Onyx soon so I can confirm for sure the true viscosity and casting results. If anyone else has worked with Oynx and can comment on the mix viscosity I would deeply appreciate it. 

 I now have a box load of mistakes. 

[Bulldog44[TK]]

Been sick the past week, progress almost at a halt. Waiting on some new black resin I want to try from a local vendor. Smooth On probably is the best I can get but the expired Onyx I have now is like working with glue, thickening too quick before I get to pour into the mold. Once some new stock is imported I will try it again.

 

For my M19 light socket bulbs, I am going to try using a heat gun and perhaps some spray on alcohol to attack the bubbles. Waiting for the heat gun to arrive this weekend. In the meantime I will be casting some smaller parts over the weekend to build up some stock so I can pick and choose the best parts to put in each kit. 

[darthcue[TK]]

take you your time Brian... Hoping you are feeling better now.

[Bulldog44[TK]]

take you your time Brian... Hoping you are feeling better now.

Thanks darthcue. Feeling better today. Test casting with new resin tonight when I get home. I made new molds over the past few days for each scope. One checked last night and it looks good, the second mold to be examined tonight. For the smaller parts, it still always a 50-50 chance to get usable castings with my molds and setup. The exterior surfaces are almost always flawless but the undersides have air pockets ranging from tiny to large depending on how much air gets trapped when I seal each mold. Since I am not pouring into spout holes because the milds are small, I pour into the base mold and cover it with the other half. There are air release spouts to help air escape but some always gets trapped. Post up photos in the coming days to show those air pockets.

  Sorry I am not able to meet my kits yet but hope to have better news soon after I get some more parts casted.

Cheers.

Edited January 30, 2017 by Bulldog44

[darthcue[TK]]

[Bulldog44[TK]]

 Discovered my latest M19 mold did not cure properly in two spots  . No idea what went wrong,   Big waste of silicone. Going to have another try once new silicone arrives. 

 

More casting of the small parts and M38 scope this weekend when time permits. 

[Bulldog44[TK]]

 

Update:  Progress slowed to a halt recently, work & life to blame for this. 

 

• I managed to re-mold the M19, looks good but minor cosmetic issues with the front foot of the scope. I had to touch up some bubble spots with additional silicone so it partially affected the original scope surface texture. It can be sanded to a nicer finish. 

 

• To eliminate the large air pockets trapped in the castings, I had to rethink my pouring method and scrap using the original pour spouts where the scope feet are. Those spouts are now plugged up with M5 threaded screws and I pour into one end of the mold that gets capped before the resin cures. The advantage now is that there is limited trapped air if any. Also the screws' threaded ends are casted into the scope replicating mounting holes as seen on the real scope. Its almost a full perfect casting of a scope now;  less holes to drill out, just need to drill or knock out the inner opaque reticle and screw holes for mounting the smaller parts. 

 

• Getting better results on the smaller parts. Retainer rings with threading intact, easy to screw together. Still having trouble getting perfect castings of the M38 mounting plate that sits between the scope and the smaller reticle housing. 

 

• Kit boxes purchased! ( I made them for the first round of sales but decided to go with something easy to assemble quickly- had to buy 300 of them, stocked for quite some time  ) . I finally finished the packaging insert template, designed and created in Word. Spent lots of time mocking up a few designs but settled on a simple easy one I can prep. Now putting them together. Lots of folding lines to score and edges to trim but think it will compliment the actual scope kit.  

Hoping to have some fully finished scope kits ready in the next week or so. 

[darthcue[TK]]

any updates on your scopes bro Brian?

[Bulldog44[TK]]

any updates on your scopes bro Brian?

sorry, I have some family visiting me in Japan for a few weeks. Busy touring around. Hoping to get back on track in the next week or so. Really sorry for the long wait. I think I have parts to put together some kits but need to sort out some mold issues to get one last part to cast better and finalize my packaging & manual. Just ordered some cheap biconvex large lenses for the larger end and some cheap small clear domes for the smaller end lens . Not sure if they will fit but if they do then its one less thing to source for the buyer.

[Tee-Kay Fisto[TK]]

Will you be opening an interest list for your latest batch of M38 scopes?

If so I'll jump straight in for one possibly two

These are just what I need in my life right now. Fantastic workmanship on these.

 

Cheers

Brian