robdebie

Steve, I just found your thread, great stuff! I will comment on a few things. I'm slowly (slowly) converting a 359 to a 281, to build the 'Duel' movie truck. First that wheel/tire size. I'm very happy to read that you too think that the kit wheels and tires are too small. Most 'Duel' models looked wrong to my eye, and one problem appeared to be the wheel/tire size. A photo analysis with two known dimensions, 202" wheelbase (measured on the front rear axle, since this truck has a tag axle), and 120" (119 1/4 actually) cab size. I kept measuring tires in the 44-45" diameter range. The kit tires are the equivalent of 40.5" diameter. AMT's Part Pack PP028 'Semi tractor tall tires 11.00-22' are the equivalent of 41.4". I did another photo measurement that established the wheels were 22", see the rest of the analysis here: https://robdebie.home.xs4all.nl/models/peterbilt-3d-1.htm Therefore the tires must have been 11.00-22s. I looked for period tire data books on Ebay and Worthpoint. I found very little, but one brochure listed 44.1" diameter for a Goodyear Unisteel 11.00-22. Hakan Persson found a US supplier of 'old style' tires: 11.00-22 14PR G STA Super Transport TT listing a 44.7" diameter. Those values fit my analysis, and I'll go for 44" or thereabouts. Apparently no model truck tires are available with this diameter, but I'm happy you designed them yourselves. I'll probably do the same. Conclusion: I agree with your 'larger wheels/tires' theory, at least for my movie truck. Of course I don't know what other Peterbilts had fitted. And I'm happy that you have an eye for shapes, and noted too that the wheel/tires were too small. Rob

Robert Tolone did a video on using different pressures, but it doesn't really answer our question. I would even dare to say that he did not consider the air absorption theory. Rob

In the past, I did quite a lot of vacuum infusion of composite parts. The biggest was 10 by 3 meters 🙂 We would always de-air the epoxy resin thoroughly, and if the injection went as planned, we produced totally void-free parts. But if you would get a small dry spot, with the injection encirling a spot, the tiny amount of air present would often be absorbed, solving the problem. I know that research was done on the de-airing process, but I did not participate in that. Here's one example of such research, but as far as I can see, it does not discuss 're-absorption' of air, after de-airing that same resin. But if the gasses got in the resin before de-airing, they surely must be able to 'get in' after de-airing too. https://www.sciencedirect.com/science/article/abs/pii/S1359835X20300567 The paper does not discuss the effect of pressurizing the resin-air combination. But that must have been studied extensively for autoclaving of composites, so I expect scientific literature on that too. All in all, I still can't prove my assumption, but I'm pretty sure that I witnessed air absorption in practice, with epoxy. It should be fairly easy to test the assumption, by curing polyurethane samples at increasing pressure, then cutting the samples and study for air bubbles. Actually, that might be a good question for Robert Tolone, who has a great Youtube channel: https://www.youtube.com/@RobertTolone/videos Rob

I don't know if it's of use, but here's how I copied a truck tire with single-piece mold and vacuum casting. I filled the master tire with Apoxie Sculpt to make it solid. Worked perfectly. Rob

I agree that vacuum casting makes more sense. But pressure casting works very well too 🙂 Maybe there's another mechanism with pressure casting: I have a feeling that small bubbles do not get compressed to a smaller volume, but that they are actually absorbed by the resin. Why do I think that? I have never seen tons of tiny bubbles in cured pressure-cast items. It's interesting to look at the numbers. A 1 mm diameter bubble has a volume of 0.52 mm3. Compress it to 5x ambient pressure, and the volume becomes 0.10 mm3, and that gives a 0.6 mm diameter. So, the bubble size reduction is not very impressive. So one should see lots of tiny bubbles in a cured part - but you don't. I'm sure there are technical papers and studies on this subject.. Rob

No, I haven't tried both, it just developed that way. Plus, like I write in the introduction of my webpage: "There's an interesting cultural aspect to resin casting. It seems that vacuum casting is the European way of resin casting. In the USA pressure casting is the preferred method. I'm describing vacuum casting here. " I'm in Europe 🙂 Rob

Since then I've made a web page with a lot of information on my method of vacuum resin casting: https://robdebie.home.xs4all.nl/models/casting.htm Here are a few pictures from the page. Rob

Helmut, thanks for your reply and extensive analysis, I really appreciate it! You know your 907s and 908s, that's clear 🙂 I had called in the help from the GPMA mailing list, and we arrived at the same conclusions: - the project probably started as the narrow 1967 907, with the 'high' windshield - issued as a 907/908, naughty.. - wheelbase almost correct - overall length way too small - way too narrow, the 1967 907 is closest - the cabin is set too far aft by somewhere between 4 and 8 mm All in all, it would be very difficult to correct this model. But anything is possible - I've cut up a few car bodies to make shape corrections. One of the worst was the Profil 24 1969 Porsche 917. Wheelbase was 6 mm too small. I added a 4.5 mm extension between the doors and rear wheel openings. Plus lots of other mods. My most recent project is the Nunu Porsche-Kremer 935 K3, that I modified heavily. It looked horrible straight from the box, but after lots of cutting and gluing it looks like a 935 now. Unfortunately I don't have a way to show before and after. Here's 'after'. Rob

It might be difficult to answer, but does the allergic reaction develop during the casting, or the sanding of the resin? If you know the answer, you can focus on improving your safety measures on that phase. Judging from the whole sheet of safety warnings on one of the components of the Smooth-On resin that I use, the casting operation is not without risk. The dangers of isocyanates are not to be underestimated. I know one Dutch seller who stopped PU resin sales, he couldn't take the responsibiliy anymore. Judging from modelers' stories, the sanding phase gives most problems, usually in the shape of nose bleeds that won't stop. Rob

A tip from a fellow user of Alps decals: I recommend lightly sanding the edges of the cut decal. It softens the sharp cut edge, and makes it look better on your model, with less of a visible step. Rob

Thanks for the linked video! It yielded a much better view of the 'White Power' sticker than I had ever seen before. I drew my decals based on a much worse screenshot from the movie itself. Rob

Haha, my favorite quote! The moment they lift from their seats due to zero G (how was that done??) , I start laughing, and then that quote on top of it, I nearly wet myself 🙂 I put the quote on the fictitious shop display that I made for my model. But hardly anyone here (the Netherlands) recognises the car, let alone that quote.. But it doesn't matter, I love it 🙂 Rob

Since you state that the part was perfectly clear after demolding, you can rule out that the cloudiness is internal. My first guess is that the material isn't hard enough to be sanded and polished, it's too rubbery. You can probably find the Shore-D value somewhere. Maybe you can increase the hardness by a postcure, only then you get the full material properties. Room temperature cured epoxy isn't 'done' curing. I've done some clear resin casting too, with epoxy resin. Shown below are the fuselage parts of the MPM 1/72 Fokker G.I Mercury. Epoxy is a killer for silicone rubber, shown in the second photo is the sixth casting, that came out cloudy. With polyurethane resin I get twenty castings. Rob

Here's a scratchbuilt example, for my 'Blues Brothers' Ford Pinto Wagon, quickly slapped together because of a deadline. It's three plastic parts: the mirror, the arm and the foot. The mirror was thick piece of plastic card, trapezium-shaped, sanded on the front side to make it slightly bulbeous. The mirror itself is canted like in the movie. It's not perfect but it does the job. Rob

Helmut, I'm a bit late to the party, but how would you modify the model to make it more correct? For starters, I think the cockpit should more forward quite a bit. Maybe the windshield is too long? Rob

Assuming you're using enamel paint, I would recommend a Paasche H. It's based on this video, showing the 'Donn Yost' technique. I tried it, and it works really well. All enamel paints came out super glossy and shiny, something I never achieved with my other airbrushes. You do have to crank open the nozzle for the final layer. It's a fairly cheap airbrush, give it a try! Rob

I used CA throughout. The first layer is difficult to do: you need to glue the 45 degree cut ends together, while not gluing the strip to the rim. Here's a photo sequence of another one I built. The rough ends were cut off with a JLC razor saw. Rob

Cheap it will never be, but that's also a consequence of wanting scratch-built 1/8 models! I cannot predict the actual costs, you'll have to give it a try and see. You can break it up in design costs and printing costs, to keep control. But I'm pretty sure you'll be hooked once you start, it opens up a world of possibilities. A club member printed some 1/24 truck tires in rubber on his filament printer, and that didn't look half bad. The route you mention is another good one. Personally I don't need tires to be made from rubber, I like them better in a hard material. Two examples below: an old Ertl truck tire cast in resin, the rear one flattened so the truck doesn't appear to be standing on its toes. And second a slick tire made by wrapping sheet styrene around the rim, and painted off-black. Everyone thinks it's rubber! Until I bounce it on the table, and you hear it's hard. Rob

I guess you'll get this anwer multiple times: 3D design & printing. I've done a few small '3D' projects, like the truck wheel and the tiny 1/72 airplane shown below. The results are excellent. But the usual barrier is mastering 3D CAD design. If that's insurmountable, maybe you can hire a school kid to do it for you. Rob

Thanks for the compliments! Here's one more with a car model. But not a Pinto 🙂 Rob

I built the MPC 1977/1978 Pinto Wagon, as the the Illinois nazi's car in the 1980 movie 'The Blues Brothers'. It started as a glue bomb. I don't consider it 100% done, MPC 'forgot' the chrome trime around the side and rear windows, I hope to add that one nice day. I made a fictitious shop display for it, that was shown along with 32 more fictitious shop displays at the IPMS-NL show ESM, see here: https://robdebie.home.xs4all.nl/models/shopdisplays.htm Rob

I would say it's regular polystyrene sheet. The cracking problem is easily avoided by not using pink Zap, so the problem is not too bad. But it is fascinating! Rob

There's no brand on the polystyrene, only a small sticker with a bar code and a brief product description. If I could read the bar code, I would probably know the manufacturer too. To be clear, I did not use a kicker. Never used that in my life. Rob

A follow-up. I did a simple test: I bent pieces of 1 mm plastic card into an arch, and fixed the base ends with a piece of tape. Then applied a drop of CA straight from the bottles, on the arch's peak, the area that was most deformed. The pink Zap specimen started cracking within seconds, but nothing happened to the Colle 21 specimens. I bent all specimens identically, but the cracked specimen changed shape due to the cracking. On the left, the same specimen but upside down. On the right, an earlier test. Different cracking patterns. An amazing result! But I can't offer an explanation. It would be great if forum members could repeat this test with their CA glues. If you want to replicate mine: the samples are 80 x 15 x 1 mm, bent to an arch, the ends fixed with tape with a 20 mm distance. CA is applied straight from the bottle, tip against the top of the arch, approximately one drop over an area of 15 x 5 mm. Rob

I have a page showing 'Humbrol tin evolution': https://robdebie.home.xs4all.nl/models/humbrol.htm. It includes some details on the production locations. Production was in China for a number of years, but returned to the UK in 2012, outsourced to Rustins Ltd in Cricklewood. The China production was unreliable in quality, but the UK production did not improve it. Many modelers simply gave up after maybe 20 years of unreliable paint, including me. Many modelers here (Europe) move to acrylics, and sell their surplus enamels. That's probably the best source for older Humbrol paint, that's of good quality. You can identify the good quality tins by their labels. I'm still using the 'Authentic' paint from time to time. 40+ years old, shake it a bit, ready to go, excellent coverage. What a difference.. Rob