I've been posting most of my work over here: http://forums.mylargescale.com/15-model-making/44722-hfc-tanker.html (http://forums.mylargescale.com/15-model-making/44722-hfc-tanker.html)
I read this forum fairly regularly, but I think this is only my 2nd post here.
I'm going for the sheet metal look on the tank body:
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Ftank_body2.jpg&hash=bb04c38ee1f4615ccef92297e3689b9860248c9c)
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Ftank_body4.jpg&hash=0bb4c3e3ba4cd2634359054c826b2614ceaa9da8)
I think I have filled, sanded & primed about 5 times on the main body. This is 1:29 scale, so I can get away with using Bondo & spot glazing putty. I just glued on the tank ends last night, so there will be another round of filling & sanding. I'm being picky at this stage because this will be the pattern for an RTV mold.
Hi Burl, nice to see you posting here! Great work as always!
My end castings ended up being about .040" bigger than the body, so I re-molded & the shrinkage from that process took up most of the difference. The 2nd generation of castings was only a hair larger than the tank body, but I still had to do another round of Bondo & spot putty to even out the seam. Here it is after a fresh coat of paint. I still have a couple spots to fill & sand, but I'm almost there.
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Ftank_body5.jpg&hash=6330f7087aceb343a131cc3225288f07057de0c2)
Since the body has a slight V shape, I had to do something to account for that in the connection between the body and the bolsters. I made a temporary jig to align the bolsters.
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Fbolster_jig1.jpg&hash=fce958a37d148bd43c5d4d48e88cd659eb9b3e10)
They're hard to see, but on top of the bolsters are two wedge shaped castings. The patterns for these were 3d printed, using the body angle to derive the angle of the wedge. They are tacked to the bolsters with two tiny drops of CA. A larger quantity of CA is put on top of the wedges, then the body is aligned on top of the whole thing.
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Fbolster_jig2.jpg&hash=71bbcad0180b83f2b17717289fef2b22eaebfde8)
After the CA has set up, the wedges are popped off the bolsters with a flat tipped X-acto blade:
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Fbolster_jig3.jpg&hash=3e6c1b075a08a8016da90f0783133e142a333b18)
Then they're beefed up with some .040" styrene. This should make it easy to keep the production castings in alignment when assembling the finished model.
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Fbolster_jig4.jpg&hash=4803a71e7881b205fbdf41eb655452507c3810be)
And here's a dry fit:
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Fbolster_jig5.jpg&hash=a604c0ac5112782cdf740fe00af419a7935de604)
Very interesting!
Starting on the final coat of paint today. Decals (weld beads) have been applied, and all mounting holes have been drilled. I'll have to let this dry for a couple days before I paint the top. I'd hate to get smudges on it from sitting in the cradles.
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Ftank_body6.jpg&hash=665c792e85871ac27b9c43fc8628cddf21bbf125)
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Ftank_body7.jpg&hash=ca01f06039a527e4bcabd62454751a37c50f549b)
Started the pouring the mold this week:
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Fmoldbox_pour1.jpg&hash=6311a8cec288efee7549b3039af43edc6f5f648c)
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Fmoldbox3.jpg&hash=9d75035ba05ebe606ce3f6d8129f448325fde56a)
Pulled the mold out of the mold box today.
The aluminum foil worked fairly well as a release. I still had to take a couple sides off to get the whole thing to release. One thing I learned from my previous project: the mold box needs to be able to be disassembled from the outside.
I wish I had put some stock in on the ends for spacers. As it is with the mold length equal to the inside width of the box, it is difficult to get in and out. This got fixed by cutting about 1/8" off one end of the mold.
That's a two-piece mold, right?
Take it out!
The suspense is KILLING me! :o
Mj
Ray: I was going to cut it completely in half, then I realized I could cut three sides open and use it like a glove mold. Wish I had thought of that before I poured it. I would have made the seam on the bottom of the car.
Mj: you think the suspense is killing you? How do you think I feel!
I pulled the first casting out too soon and it deformed on me. It wouldn't have been usable anyway because the resin heaped up on one side. I made some adjustments, and poured again this afternoon. I will probably let it set overnight before I demold this time.
Also, this is my first try at using a legitimate mold key knife, so I'm anxious to see how much flash is produced.
While trying to figure out how to make up for the shrinkage of the mold material, and how to get the mold out of the machine, I had the idea to use plastic sheeting. By wrapping the mold before I close up the box, it makes up for the shrinkage incurred when the RTV cured. The packaging doesn't say what its made of, but the sheeting acts like polypropylene in that resin doesn't stick to it. It also gives me something to hold onto when I'm taking it back out:
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Fmoldbox4.jpg&hash=c5227fab56dafdd04f848bb2370523bf496e5de1)
The first casting had too much resin heaped up on one side, and I pulled it out too early anyway. Strangely, I feel better about losing the first one. The last large mold I did poured perfectly the first time, and it took me months to figure out how to get another good one out of it.
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Fcasting1.jpg&hash=2ea4bb2eb501520c01554eea492efc57894fabe2)
My theory for the first failure is that the resin was too thin, allowing the majority of it to congregate in the bottom, instead of sticking to the walls. It accumulates heat too quickly this way, and once it begins to kick (accelerated by the heat), it stops flowing all together.
To compensate, I added micro balloons to increase the viscosity. It seemed to work. In the second casting, you can see where it has kicked. Each dark wave is one pour. This was four pours, three ounces each, giving a total of twelve ounces of resin. This photo is a 15 second exposure in a dark room, with a flashlight held to one end of the casting:
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Fcasting2.jpg&hash=ba2675fe0b417132eadbb54daaa2937bbf655a52)
In the next casting, I will try increasing the viscosity with more micro balloons. I will also insert a straw in the pour hole to help the resin flow in faster. That should give me a little more working time.
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2Fbody1.jpg&hash=088d9d89f68c74c91e6cfdf9f5d87c226e386908)
Looking good!
You seem to have made some progress. -- Russ
Fill 'er up!
Looks great!
How many are you going to make?
Marty
That came out really nicely. Does the whole mold rotate at low speed to keep the resin from settling during the early part of curing or does it spin faster to centrifugally to force the resin into the pattern?
Looks good to me!
I was planning on making 10 kits for the first run, and see how that goes.
The mold only rotates around 5 rpm. It took me quite a while to figure out the right rotation speed & resin viscosity (I'm thickening it with micro balloons), but now I'm getting consistent castings out of it.
(https://www.finescalerr.com/smf/proxy.php?request=http%3A%2F%2Fburlrice.com%2F_LS_CornSyrup%2F3_4ths_lr.jpg&hash=321ff52b77677afb573074e58c4465eed2e88a17)
That looks amazing!
Satisfactory. -- Russ
Okay so thats the prototype you are using for reference, where's the model? ;)
Great job!
Are you going to build several?.....
-Mj
Wow I really like the overall project but the trucks and couplers top it off very nicely!
Patrick Welch