robdebie

After 16 years of on and off use, I replaced the oil in the single-stage rotary vane vacuum pump that I use for vacuum resin casting. I can't say exactly how much time the pump ran, but 5 hours total is my first estimate (100 runs of 3 minutes each). I read a warning that polyurethane does contimate vacuum oil. This close-up shows how the oil separated after 20 hours. The top part looked like regular oil to me, then a layer that looked like engine car oil sludge, oil that has mixed with coolant or water ('mayonaise') At the bottom I see some white parts. Weird! The lower two parts look really strange to my untrained eye. However the pump runs the same after adding fresh oil, I don't notice any difference. Since there are plenty of (hobby) car mechanics on this board, I would love to hear your judgement! Rob

Those nylon parts are very porous indeed. But you can improve the material properties and paint adhesion by filling the pores with CA glue. It will absorb a lot.. Rob

BTW, I also made an animated GIF of the box art of the Matchbox 1/72 MiG-21PF, when I found a photo that must have been the inspiration for the box art artist: He changed the pitot tube, the canopy and the spine to make it a PF version. He added a parachute to make it more dynamic, but you can see this is from his own imagination, since he attached the parachute to the bottom of the fuselage, whereas it should attach to the base of the fin. Also, the centerline tank, that he also added, has fins that look rather crooked, since he had to sketch them free-hand. The tank appears to be yawed to the right too, now that I look at it closer. Rob

Thanks for all your comments. I made a slow version of the first picture, to see if that suits you guys better. AFAIK, there is no way to make the GIF's speed variable. You can download the file and use graphics software to change it, or run it through one of many online speed converters. The photos were indeed taken with a tripod. Once I photographed the first model, I put some heavy objects as stops against the body, then switched bodies while using the stops to position the body, then removed the stops, lastly made the second photo. I did some fine-tuning of the exact positioning in graphics software. But all in all it's not too much work. Rob

While making kit reviews, I noted that it can be very useful to compare two different kits of one subject. You will spot the differences between the models, and then check which manufacturer got it right. It works even better if you can photograph the models in exactly the same position. I did that with the AMT and MPC 1971-1973 Mustangs some time ago. It requires careful work to put the bodies in the same spot, but you can make small corrections in the image software (Photoshop etc). But only a few days ago I got the idea (from a friend) to make an animated GIF from each set of photos. And it works really well I think: if you study the alternating photos for a while, you'll see more and more differences. Just in this view, I noted the following differences, with AMT in white and MPC in tan: the AMT windscreen is angled slightly steeper, and slightly longer at the top the AMT A-pillar is thinner and more accurate, and has a slight curve the upper edge of the AMT door opening is positioned 2 mm higher than the upper edge of the windscreen, on the MPC model this is around 1 mm. MPC is more correct in that respect AMT's side window is about a millimeter taller at the rear AMT molded the NACA ducts in the hood 2.5 mm further back, and they are shallower and closed. I measured some distances in a photo, and found that the front edge of the NACA openings are at 33.0% of the local hood length. The length of the inlet piece is 2.75% of the local hood length. That shows that the MPC inlets are 2.5 mm to far forward, and the AMT nearly spot-on (0.5 mm to far forward). AMT's fold in the sides is more restrained than on the MPC model, and faired in the sheet metal with a radius. The MPC has sharp folds, and that's what the real car shows the AMT fender flares are also faired in with a radius, but it should be more of a fold like the MPC model AMT has raised trim strips on the lower body, MPC forgot them. The Mach 1 version had them to cover the factory paint break (earlier I reported the opposite) the 'Mach 1 Mustang' logos the front fenders are molded raised on the AMT, whereas it is a sticker in reality on the 1971 and 1972 Mach 1 cars. Most other Mustang models have a raised 'Mustang' script, as does the 1973 Mach 1 the AMT grille and headlight area is modeled differently, likely more correct than on the MPC model the AMT hood has no vent slots near the windscreen, which is correct Here are three more, but I won't list the differences, see: https://robdebie.home.xs4all.nl/models/mustang.htm I'm curious what you all think of this method. Rob

Inspired by Erik's post, I did another analysis, to see whether there was a proper vanishing point. And indeed there was one, see right side of the picture below. I again conclude that the (relative) lack of perspective creates the illusion that the far side is larger than the near side. Rob

Two comments: First: I think it cannot be a speed effect, since the photographer is panning his camera with the same 'speed' (angular velocity) as the car. For the camera, the car is standing still. The track is moving backwards though! Second: in the 3D CAD software that I used in the past, you had several options how to display the object one was drawing. One choice was perspective or no perspective. If you work for a time with perspective 'on', and then switch to 'off', the object looks really akward, like the back side is bigger than the front side. I assume that applies to the racing shots too: we are so used to seeing cars with perspective, that a photo with barely any perspective looks strange. I'm guessing the photographers used very long telelenses, in the order of 400 mm or so. With such long lenses, you get very little perspective deformation. Concluding: it's the lack of perspective that plays tricks on you. An unrelated example: if you know the Porsche 917K, it had a pretty wide and high rear deck. But since we hold our models at arms length or less, you don't see how big it actually is, in relation to the cockpit section. Only when you are confronted with race track photos, made from the front with (again) a very long lens, you see how ridiculously large it is. Like on this book cover. It's another example of the effect of lack of perspective. I photographed the Heller model in almost the same attitude and with the longest lens I have, and it gives a similar effect. Rob

An important drawback of addition type silicone (platinum type) silicone rubber is that the curing reaction can be inhibited by a number of materials. This is called inhibition or poisoning. The following materials are listed by various manufacturers: - condensation type silicone rubber (especially its tin-soap catalyst) - unsaturated hydrocarbon solvents - sulphur (in vulcanized natural and synthetic rubbers) - phospor - epoxies containing strong amine catalysts - isocyanates of urethane resins - tape adhesives - metallo-organic salt-containing compounds (especially tin salts and heavy metals) - plasticizers in plastics (especially vinyl) - some epoxy and polyester resins - nitrogen containing materials - some modelling clays - solder flux - wood - leather - chlorinated products (such as neoprene rubber) It's a scary list for sure. Better do a test when in doubt. Rob

Interesting thinking! If one would cast two copies of the 'second' (lower, body interior) mold half, and save one of those, my goal would be roughly achieved. The claying would still have to be done once though, but not for making subsequent mold sets. Rob

I've always wondered about the following. The clay-filling of a body is quite a bit of work, the clay removal before casting the second mold half is quite a bit of work, and all this needs to be repeated every time a mold wears out, after (say) 30 castings. Isn't it better to create a permanent (but removable) plug for the interior? I haven't found a perfect method yet, but maybe the clay plug can be baked, or you cast the plug from plaster and seal it, whatever. What do you think of this approach? Rob

Bill, another big thanks for all your help! I think I now understand most details of the Airfix carburetor, and modified the kit parts a bit. I scribed a line around the velocity stack, to indicate it is a separate part, and to serve as a paint demarcation. I cut off the set screw on the left, glued in a piece of thread, rolled a spring from plastic rod, and reinstalled the screw head. On the top side (right in the photo) I cut off the two very unround cilinders, and replaced them with 3.5 mm tubing. Maybe I will add throttle and choke cables coming through them. On the right side of the float chamber I cut off the simulated cut-of fuel tube. To make its function clearer, I replaced it with a piece of tubing that I gave barbs by using my motortool as a lathe. I just applied a layer of Mr Surfacer to check build quality. Painting will start tomorrow. Finding a paint match for zinc might be a problem though.. Rob

Absolutely! I spent so much time on masking, it's not funny. If I was ever to build something similar, I would try to break the parts up, and replace as much as possible with metal hardware. I hadn't considered cutting away the carburetor, but indeed that would totally fit with the rest of the model. But with the finish line in sight, it's really hard to do that right now.. Rob

Fantastic! That will surely help. Those Amal carbs really look a lot like the Airfix thing. I just discovered that I don't see a fuel line, or a throttle cable, to name some esstential components. Regarding the color, are those Amal carbs made from Zamac / Zamak or similar? I *just* finished filling and sanding the transition between the body and velocity stack, grr.... But I always thought that casting it all in one piece wouldn't be easy in reality. Back to the drawing board.. Rob

Slow progess with the Airfix engine: I painted the new flange of the crankcase, and painted the 'gasket' in a cork-like color. I'm now working on the valve train. I used three metal colors for each valve. The last major part to paint is the carburetor. And again I could use some help, because I have no idea what the various details represent. I never worked on a real carburetor.. Thanks in advance for any suggestions! Rob

Maybe your partially assembled kit could serve as a testbed? I think it requires careful study / planning / testing to create a tasteful cutaway engine. I'm getting more and more enthousiastic about this idea, but the amount of work scares me.. I made the next step with my Airfix model. I created a fillet with Apoxie Sculpt, with small cut-outs on the corners for the bolt heads. Next was the paint, from a freshly mixed batch. Next is the 'gasket' on the base. Rob

Bill, Trevor, Michael: thanks for the kind words. I'm building that fillet now, using Apoxie Sculpt, about halfway now. More photos soon. Michael: same interest here, and that resulted in this visible engine overview. I basically made it to pick the best visible engine, but I still haven't decided, and started with the relatively simple Airfix engine. I'll publish a full build report of this Airfix model on my web site, once it done (i.e. soon). I've been thinking: could the old Renwal / Revell 'Visible V8' be built in this style too? Fully painted but with cutouts? Rob

Here's what I built yesterday. I built the two flanges (one each for the crankcase halves) from polystyrene strips, feeling my way to what looked right in terms of width and thickness. I ended up with a shape slightly larger than the 'thing' that Airfix molded. For the rounded corners I used half of a 1/72 rocket pod body. It's a dry fit, the flanges are not attached to the crankcase yet, therefore there is no fillet. The original detail under the new flanges still needs to be partially sanded away, so the flange will sit on the 'gasket'. Please let me know what you think. Thanks again for all the input that led to this solution. Rob

100% agreement with what you write. Can you agree with the modification as sketched in the previous posting? Rob

You could phrase my initial question like that, yes. Based on the responses so far, this is what I currently have in mind. I want to sand off half of the 'strange detail' and retain that as a simulated gasket. Next I would add a relatively thick flange to the crankcase halves. The crankcase gets lifted by 2-3 mm. Would you agree with this approach? Regarding the fuel cap on the base of the other model: that fuel cap was originally the turning switch for the electric motor. I don't see the base as a fuel tank, but one could. I removed all traces of the motorization on mine, hence the difference. Rob

It's a crazy phenomenom indeed! Could you, for the sake of science, try water-based acrylics over all these paint layers? Theoretically that should stop the bleeding. Rob

Bill, Greg, Ken: many thanks for all the responses and insights! It's clear that all of you 'see' a flange, and the photos support that idea strongly. Thanks for searching and finding the photos! The modification to a 'flange' type construction wouldn't be too much work actually, if I would do the filling with Apoxie Sculpt, without sanding. But the thing is that I made a custom paint mix from three colors, to create RAL 6011 'machine green'. And as Murphy would have liked it, I just ran out of that paint. I need to do some hard thinking.. Bill: I fully agree with your comment of 'what happens when the tooling designer doesn't understand the function or real-world construction'. In my view, this model is full of these problems.. Greg: I think the model represents a theoretical teaching aid. I never found a picture of a single cylinder engine that resembles the model. Rob

I'm building the 1972 vintage Airfix single cilinder four-stroke engine with cutaway sections. Here's where I'm at, nearly done: I want to glue the crankcase on the foot, but I just don't understand the detail that Airfix molded on the foot. Here's the connection between the crankcase and the foot. Is this supposed to be a clamping ring? Or is it a flange of the crankcase halves? Or is there a simulated gasket under the clamping ring? Should I fill the gap to make a smooth transition to the flange / clamping ring? What do you think? Any help is welcome! Rob

The simplest solution I see is to rename all the photos to the actual model's name. Then that file list (folder / directory) is your database. Rob

Try the 'Donn Yost' or 'Andy X' method! I found it some months ago, and it worked extremely well for me. Here are some test pieces - so far it worked with all brands of model enamel that I tried. The method is simple and easy, give it a try! Rob

I built the 1/96 version two years ago, and made a full build report, with details of the paints I used: https://robdebie.home.xs4all.nl/models/lm.htm With this as the end result: For the 'wrinkled' isolation blankets, I used kitchen aluminum foil. If you have an airbrush you can use yellow and red paint to mist over the foil to create the required three colors. My build report includes a link to the David Weeks drawings, that contain a ton of information. For the fine-grained material, another modeler used a mortar repair material, to repair brick walls, and that looked really good - just the right mix of fine material and 'boulders' if applied with a spatula. Plus probably the right color, boring medium gray. Here's a picture of the stuff I'm talking about: Rob