i have been so intimidated about casting, but your tutorial (to this point) is showing me the "do-ability" of it. the pressure pot thing has always been a deterrant, however. i'll be most anxious to see how that is achieved. i do so hope the master (and resin parts) will be able to be removed reasonably well from the mold. that's the part i hear you cautioning about. i hope, i hope, i hope, i hope.... thanks for showing it all to us, tim. definately DO keep this archived somewhere! dave f.
Tim, Can one mix the resin and put it in a vacuum pot (to make the bubbles come up) for some time then pour it in atmosphere? Kim
Update #4 Ok, today I woke to find the molds ready for seperation. I took the styrene sides off and removed the small styrene pegs I glued to the master parts for venting resin/air bubbles. This photo shows the molds before I carefully pry them apart. I still have some hobby knife cutting to do to the top of the molds. I will make small inverted conical cuts in every vent hole. This inverted cone will hold a greater amount of resin than the small vent alone. I do not have the luxury of owning a vacuum pot, to de-gas the resin, so I have to rely on my pressure pot to reduce any air bubbles, in the resin, to near invisible. The next photo shows the molds taken apart, with the masters still inside. Everything looks great so far. Here are the three parts that were molded. They are in perfect condition. I have since washed them in warm water and a small amount of liquid soap. Then rinsed well and gave them a Polly Scale Plastic Prep bath to remove any mold release residue that still remained. They will be shipped back to the owner real soon. The last photo shows the molds. I have carefully removed any small RTV flashing from the mold so when resin is cast the results will be as perfect as can be. I have placed the molds to the side to cure!!!!! Stay Tuned for the Casting of the first parts. Probably this evening or tomorrow. Right now I have some Thrall's to airbrush!!!! Hobo Tim
Vacuum Pot/Pressure Pot Kim, A vacuum pot is exactly what I need to make castings absent of air bubbles. I have combed the web to see what a cheap vacuum pot would go for. The lowest I found once was $300, and that was for a pump only so I would still have to hook it up to my pressure pot. If I had one, would be great!!!!! If you find a cheap source, please let me know!!!!!!! David, The masters are in near exact condition as when they left your home for Robert Ray. The only thing I did was glue styrene .040" square rod onto the parts. The only place that might need any fine tuned sanding might be the walk deck. The parts were expertly assembled and I applaud your skill and cratfsmanship!!!! The pressure pot I use is nothing more than a 2 1/2 gallon pressure paint pot that a house painter would use. You can find these at Harbor Freight! They have this on sale right now for $39.95. You will need to remove the regulator and put the pressure gauge in its place. The other fitting will need a quick disconnect male fitting. You can put the quick disconnect female fitting on the airhose end. Under the lid a long metal tube protrudes to the bottom of the pot. It will need to be removed. Once all of these modifications are done you are ready to pressure up the resin. This pot has a safety rating of 80 psi pressure. For casting, what I have read and experienced, 25 - 40 psi is all that is needed to make some very nice castings!!!! When I purchased my pressure pot I also got a small 2 gallon air compressor and fitting for about $65 total. I went to Home Depot to get the metal valve to releave the pressure from the pot when the castings have cured, I usually time it at 55 minutes each cast. When I start casting the test samples of the SD70ACe I will take a photogragh of my pressure pot set-up. Hobo Tim
tim, this is fantastic! i know i'm as excited as everyone else. if you want to keep the shell for a while and make a second mold, now is clearly the time to do so! feel free. you decide. i can wait a little long for the master, since the etched railings/doors are going to be needed before i can finish the shell anyway. thanks for your great efforts, tim, on behalf of all ACe and Z fans! WOO HOO!!! ok. now comes the main act. i hope it all comes out well. dave f. p.s. and thanks for the info on the pressure pot.
Heck Yea!!!! Heck Yeah!!!!! I see no reason why it couldn't be. I have actually read a message in a casting forum where some use this same pot for pulling a vacuum on mold and resin materials. Mine would be used to vacuum my RTV and resins if I only had a reasonably priced vacuum pump. But the pump also has to be able to pull a certain amount of vacuum to achieve desired results. I can't remember the amount but I believe it is 32 lbs of vacuum, or something like that. I have a DVD from Freeman called Making Parts, Patterns, Tools & Molds. Freeman sells a variety of rubbers and resins and depending on what type used might require a vacuum pot to de-gas the material. Freeman, DAP, Micro-Mark, Smooth-On, and a few others make different resins and rubbers. I think Smooth-On has the largest selection by far of both rubbers and resins. Almost anything you want or need. If you are serious about geting into casting I suggest starting with Micro-Marks casting kit first. If you will cast small amounts then it is the way to go, but if you want to conquer the world you might want to look into getting your stuff from Smooth-On. Take this time to go to their website and request a sample, http://www.smooth-on.com/feedback.htm go down to the bottom of the web page and click on the big yellow box that says "I would like to Request Literature" and you will be sent a nice informative info packet along with samples. Take the time to explore their website. Hobo Tim
Tim, I was told when I first learned to cast that if I glued the masters to a 1-2mm plate (around the edges) while making the molds this would give the bubbles a place to go. You would still put you vent holes in there. I was told you pour into one hole until the resin comes out another. So each piece needs 2 vents. You would need to cut that "plate" from the castings when done. It seemed to work for me, but I'm not a pro and don't cast much. Just thought I'd pass it along.
Not My Master!!!! Chris, Greetings!!! Please don't throw any advanced info in here. I am trying to keep it simple!!! I would have modified these masters to the extreme if they belonged to me. I did not want to add any additional items to them. I do know what you are talking about though. Again, these masters are not mine. I hated that I had to glue the vent styrene to the walkway. On a different note Chris, what have you been up too lately?? We haven't heard anything from you in quite a while!!!!! Hobo Tim
Advanced info? Naaa I'm sure you have casted a 100 times more than I have. Just thought I'd mention it. What have I been up too? Not much at all : ( I bought a N scale 0-8-0 and was pretty disgusted with the stock gear ratio (it's 2008 you know) I haven't done much train related since around Thanksgiving. I still need to install "glass" in my heavyweights and have some boxcars to decal. Well I have plenty to do, whole layout to finish. I dunno maybe it's MRRADD syndrome ; )
Tim - I do a bit of pen turning and many pen turners cast their own acrylic pen blanks. They have the same issues with getting the bubbles out. Check out the "Library" at penturners.org. In the 2007 articles, http://content.penturners.org/articles/2007/pressurepot.pdf, there is a full tutorial of how to use the Harbor Freight paint pot and a $9 vacuum pump from Harbor Freight into a both a pressure and vacuum pot. Spread throughout the library are various articles on casting resins and some of it may be helpful to train makers. Deane
Etching Update #1 This is the first update for anything to do with the etching of the brass handrails. Thanks to Robert Ray for carefully creating the artwork for the handrails. With some very minor modifications, inverting the black and white, to the handrails they are now ready to print to an overlay and UV exposure to the brass. Lengthy process, will talk more on it later. I also created the artwork for the two brass panels of doors that cover the motor. In order for AZL to get as prototypically as possible, the sides where the motor is was too thin to make from injected plastic. They had what looks like a stamped and etched piece of sheet brass formed for the sides to cover the motors. Blah, blah, blah, blah........... Anyways here is a crude shot at the artwork for the handrails and the door panels! What you are looking at is the front and the rear of the brass. Where their are voids, this is where the etchant will eat the brass 1/2 it's thickness form each side. Hobo Tim
Casting Update #1 Here are three photos of the first test casting. No bubbles in the main shell or the cad, some very small bubbles in all 4 of the corner steps, but nothing a tiny amount of putty won't take care of. This is the only casting I am going to do right now. I have already sealed the three molds in a jar with anti-oxy gas in it. Definitely a snug fit on my SD75I chassis, but fits. Just need some fine tune cleaning and the etched brass. Hobo Tim
#1 goes to.................... John, this shell will be shipped to David along with 3 sets of etched brass parts. Two for the two SD70ACe shells he modified and the third to go with this cast shell. When I do come back, I will make some more shells. I hope all of them turn out like this one did, bubble-less!!!! Don't worry, the next 8 weeks David can work on this cast shell and we can see what he comes up with. He might find somethings need to be changed. Who knows!!! Consider it a testbed time period. To work out any bugs!!! Stay tuned for etching results! Hobo Tim
tim, i'm most honored ... and speechless! the shell looks just great! i know everyone will be anxious for your return and resumption of "production." your work is top notch. one question (or two) before you leave: what glue do you recommend for attaching resin parts? styrene glue or something else? also can these be painted with floquil? is there any special preparation i need to follow before paint or finishing? i don't want to mess anything up. we'll be thinking about you as you go to your work. i suspect you'll have some internet access so you can keep in touch. thanks tim. and thank you, also, robert ray for your significant part in this project. blessings on you all, dave f.
Just from experience! David, For most adhesion efforts I use superglue liquid but mostly the gel. You can use E-6000 which is a medium viscosity glue. It takes some getting use to working with it but holds better than any glue I have ever used. The problem with it is it is stringy and skins over very quickly. It's glue like this that Walther's recommends for attaching brass details to their plastic kits. (North Island Refinery in HO scale) As far as paints, I use only Floquil on almost everything. Never had a bad experience on cast resin. You might want to wash the shell in a warm soapy solution and dry thoroughly or use Polly's Plastic Prep. Their is a very slim chance that some of the "Rubber-to-Rubber" liquid release I used when making the mold might be on the castings, but is most likely on the master. The stuff washes off easily unlike the spray stuff I have!!! Never have found anything to remove it. I think I trashed that stuff years ago. Ok, I have found you don't want to soak resin for any long periods of time in alcohol. I had some stuff do weird things once. Ruin't the casings. Ugh!!!! Now, you will need to do some fine filing/trimming/sanding/etc.... to get the shell looking exactly like the master. All fine tuning, nothing big. Typical stuff. I will make the corrections on the etching artwork that you mentioned. As for the handrail from the steps to the cab can be made from thin brass rod from K&S. Cross your fingers that I can get that done tomorrow, or at least all ready to etch. Maybe finish the etch on Thursday. Tomorrow I need to get two new tires, and oil change, and who knows what else done to my Pathfinder before the trip Saturday. Also need to get stuff for my fiance's SUV too. Going to be a busy day tomorrow. Stay posted for updates!!! Ok, what's next? Oh, internet connections. I will have my laptop, but will need to download AOL or something and use their service but yes will need internet connection. You think I cannot check emails for more than a day let alone see what people are saying bad about Hobo Tim on Z Central and Trainboard??? Hah!!!! May take a few days but I will get a connection!!!! Hobo Tim
