NickD

This will just be a short post (famous last words) to answer some of the comments above. Spoke alignment and 3D printing - the main reason for building this model in the first place was to see how much of a faff it would be to model the spokes and what a wheel with spokes that are thick enough to be printed would look like - would the spokes be so overscale to look ridiculous. The jury is still out. (in fact I have not shown it to the jury because that's you guys). Back to modelling the spokes. While Blender is fantastic, it is not a CAD package so there are certain things it does not do well. Or it does them but they are difficult. One thing I always struggle with is keeping cylinders circular when you start to bend them. This exercise was an opportunity to try some things with a shape is fundamentally quite simple. Having drawn a perfect spoke I did not want to have to place 70 of them manually so it was also an opportunity to learn how to handle arrays of objects - more later. Alignment - Very good question. There is a number factors affecting the answer. Firstly Blender is very precise even in 32 bit form. That does not mean that what the humble modeller produces will be accurate. As the screen shot shows, even with a line drawing , line thickness is a signficant issue. Also all drawings are wrong and all photos are massively distorted. Assuming one is happy with the resolution and alignment of the reference material, Alignment is in the hands of the modeller. The comparison between the measured and modelled wheel dependes on having a common frame of reference. Axle centreline is one. but the other is not obvious because the model wheel does not truely model the hub geometry and the tyres are very different. I chose to align tyre back face but tyre centrline or hub front face might have been better. As usual it needs to reflect the modeller's aims. In this case I am more interested in the lessons that the spokes and printing will teach me. I have not tried to hard to get the tyre geometry perfect. Deflated or not - there are two possible answers here. To generate the screenshot I switched off the modifier that controlled the mesh resolution, leaving just the basic mesh which is crude and flat. With the modifier applied, it behaves like a rubber skin that flows within but does not necessarily exactly correspond with the mesh. The second answer is that I might not have the base mesh in the right place. Minor tweeks could easily make bulge bigger or smaller. I might come back to that later. Again thanks for your continued interest and support Nick

Thanks for the support guys. I sense a general tone that this stuff is Voodoo or Black Magic. At the start it certainly feels like that. However, the tool is free, what it can achieve is only limited by imagination and there is a bunch of really helpful how tos online. So surely it's worth a go. The first part of this WIP is not much different from the skills taught in a the classic bottle tutorial. Reflecting on the post above, and now that I am slightly more confident about uploading pictures, I thought it might be worth a couple of extra pics. The first shows how the first circle lines up with the tyre. Subsequent steps then add concentric rings at points where the geometry changes direction. This procedes until the shape is complete. At this stage it is very facetted. Blender sorts this by offering a very clever feature called a modifier. This is non-destructive. It generates an arbitrarily smooth surface through the points the user has entered. There are modifiers for all sorts of things that can be applied one after the other and switched on or off at will. Utterly mind-blowing how they make that happen. The other astonishing for the crustier amongst us is that my laptop (7 years old) is more than good enough to do this stuff in real time. I repeated the above exercise using dimensions taken from an Italeri Mef wheel. I generated a pile of circles Not a very exciting picture - just goes to show that you don't need to have a lot of vertices to get a good result. from this the geometry is generated in a very similar way to the first wheel giving this... The image is fuzzy but that is an artifact my image processing rather than Blender. Compared to the first wheel its is clearly, as has been noted elsewhere a lot thicker than the car actually has. Direct comparison is easy. The wheels are concentric and scaled to the same OD. So switching off the modifier and highlighting the drawing-derived wheel gave... One of the things the tool does make easy is this sort of comparison. One note of caution though: the alignment is only approximate. It is not obvious whether to use the tyre wall or hub as reference.That said the overall depth from tyre face to hub outer face is very similar. Next up - spokes...

I seem to have been sucked over the spoke event horizon. Spoked wheels have recently been covered in both the Fiat 806 and Mefistofele threads that are currently running. The conversation touched on the potential for computer modelling tools to depict spoked wheels. I opined on how this might be done. I then thought I ought at least to demonstrate the approach rather than pontificate some impractical theoretical method I ought at least try it. Rather than hijack the thread further, I thought I had better create a mini WIP just on this small aspect. It's probably more of a how to really. The goal is to start from either a drawing and generate a representative (but not necessarily completely accurate) model that could be used as a basis for 3-D printing. The lack of precision is due to i) me being a bit slap-dash; and ii) I wanted to have a minimum thickness that stood a chance of being printed. The output will be a file that contains all the components and consolidated models that can be used in a number of combinations and potentially could be used as the basis for any spoked wheel. The only step I don't plan to do is add the embossed detail, I am not particularly skilled at this and I want to get on with other things. This will be relatively short, I hope but I will submit in installments. I will use a free surface modelling tool called Blender. The steps are: model the wheel and hub; model an architypal spoke; generate sets of spokes; merge all the components into a printable object. I will post the completed model at the end for information and should anyone wish to use it or modify it for personal projects. Wheel and hub models. The wheel I want to represent is that for the FIAT Mefistofele. Sources are: many pictures on the web, though few which cover the full circumference. There is also a copy of the line drawing from the kit instructions and of course the wheel in the kit.The wheels have 70 spokes. On the front wheels, there are 6 sets. The outermost is clockwise (hub to rim) with 14 spokes. then anticlock with 14 spokes. Both sets attach to the outer edge of the rim. Mid-rim there are two sets of 7 spokes that attach to the inner face of the hub. Inboard, the last 2 14-spoke rims that connect to the inner hub. So there are 28 spokes connected to the outer edge of the hub and 42 to the inner edge. I chose to model the rim and hub two different ways. The first was drawn using the cross-section for the rear wheel using the drawing from the kit instructions. The result is shown below: To generate the model, the image is loaded into a class of object called an "empty" object. That can then be aligned with the cardinal axes, scalled appropriately. If you are new to Blender the interface is a bit obscure but these are fairly straightforward once you get the hang of it. Having aligned and scaled the picture. I added a circle (renamed it - eventually) and entered edit mode. Generating a shape is then a case of align the diameter with the drawing and successively extruding (E), scaling (S) until the required profile is generated. The wheel is modelled as a single object with 3 separate meshes comprising the tyre, rim and hub. This allows various combinations of the 3 components to be used. Once familiar with the interface this type of object takes about 30mins to 1hour to complete, so fairly quick once set up. Counting the spokes took as much again!

Olivier, sorry just realised my last post mis-spelt your name.:( Won't happen again Regards

On the subject of 3D printing, I don't wish to come across as if I am the expert, I am not. However I have printed a number of items so can offer the following observations. Background - I have used Shapeways occasionally. Service has always been excellent. I have printed a variety of things: some 1mm hex bolts, an approx 1/32 scale 312T body, the ferral (I think that's what its called) for an umbrella. In all cases I used the nylon material they offer. The results were excellent but not without limitations, which I'll cover below. As I have said elsewhere, I have also had one of my car shell models "printed" (though actually milled from blocks of solid foam) at 1:1 to great effect. The process I used is: Draw the part in a free surface modelling package called Blender (other tools are available). Not always easy or right (as the 312T demonstrated - hence the approximate qualifier) - depends on modelling skill and availability of good references. Practice mitigates the former - the latter is an ongoing issue. Add thickness - Blender models a perfect infinitesimally thin surface that would be a bit difficult to print. The designer has to add thickness manually. Blender can help but in the end I did it myself. Check the mesh for printability using the Blender "3D Tools" add-in. This ensures there are no flaws in the mesh such as holes unlinked sections etc. Output the mesh in a printable format (usually STL) Upload to your printer service of choice, pick a material (more below) and use the online tools they provide to check printability. Again the 312T was a nightmare because I wanted it to look crisp and sharp. It took at least half a dozen iterations of steps 3-5 before it passed. Pay the money and wait with great expectation for you beautiful work to appear. Material choice - There are many materials ranging from CA/mineral through all sorts of plastic, many engineering metals and into precious metals. As I said above I used nylon exclusively for the following reasons. It offers the best surface resolution apart from acrylic. It is cheap. I didn't use acrylic because I felt it would be too brittle. However acrylic is potentially a good choice for the sort of thing you are discussing above (again I will discuss further below). I would love to print with the metals but 10x on cost triggers the miser in me. Results - I was surprised with the objects I got back. I had thought of nylon as a soft homogeneous material. However, the 3-D printed form is hard, more like polystyrene and reverberates like a shell when tapped on a hard surface if that makes sense. The surface finish is quite rough. The 312T looked superb (it was just the wrong size and shape - a modelling error on my part!), with just a fine linear grain like wood. The bolts and ferral were much more grainy, like sandstone. The bolts in particular were right at the limit of what was possible with the material. Conclusions - I have been really happy with the results I got but it does highlight the care needed to pick the right material. Let's also be clear, nylon is nylon. It does not paint well and does not stick well. Neither were issues in the applications I had - it does melt so I rivetted the bolts on with a soldering iron! Surface finish is not good enough to be used directly - easily fixed by filling and sanding. Benefits - You can produce any arbitrary shape you like - 3D modelling skill and good reference materials are the key enabler. Limitations - the perfect material for this sort of application does not exist ( at least on Shapeways). Small details are difficult. Surface needs post processing. Size is limited (though not in any way that would affect sensible non1:1 modelling ambitions). It would struggle to do the sort of resin ejector seat model used by our aircraft bretheren. Alternatives - Once the model is in digital form, there are any number of different ways to make it real. Make cross-sections (which the tool can do easily but which are a faff to turn into something useful), and if big print on paper and bandsaw out, or small - photo etch. Send to a theatrical prop specialist and they can machine from polyeurtithane or polystyrene foam (still need work on surface finish but can be fabulous) Wheels - So how would I do wheels. Sorry Oliver this may be difficult reading... Need good source material for a typical 1920s tyre. Once obtained draw in one's favorite package (adding sidewall text is probably achievable through use of displacement maps provided the resolution can be printed). Then there is a choice. Starting from scratch, I would be tempted to print rim and tyre as one with holes already defined (Sorry chaps). Having done that you might as well print the hubs too. The problem is going to be material choice. With the 312T we used the 3D part to generate a mould that we could cast from. So material choice becomes one of resolution not durability. Then cast hubs and tyres (beyond me at the moment but one day). For those who have already produced awesomely neat 72 spoked wheels the above approach would work but do the tyre alone. Two separate halves (cut on the diameter of course) could be printed and then moulded to save razor sawing. Fit tolerance to the rim might be an issue but that's what Dremels are for. Hope that is useful. Sorry it is a bit long. Nick

Roy, Thanks for the kind comments. I just hope the model is right. Bit more work to do yet before victory can be declared methinks. One thing it highlights, and part of the reason for getting in touch in the first place, was that there are some fantastic, useful FREE tools to help the modeller enhance, correct and embellish. A measure of its power is that I used Blender to design a full size one off body shell with a low drag coeff. We "printed" the shell as a buck in foam full size. It should be able to deal with anything the guys reading this website can imagine. If anyone wants more insight a great starting point is Witold Jaworski's thread here: Thanks also for the research - I'd just been thinking I would have to understand the development story. Saved me a lot of time. Regards Nick Time spent modelling : 0 (as usual) Time spent studying: never enough

I have a feeling this is going to be a really stupid comment but... Can't you just run a 0.5 drill up the inside of the tube to provide the clearance. Might drive you insane but apart from that what is there to lose? Please feel free to explain simply why this is a dumb idea. ATB Nick

Glad I'm not the only one crawling round the spidery corners looking for things I should have a kept a better hold of. Microbrushes and bluetacking down the bottles would not have occured to me. Thanks again All the best Nick Oh and fortunately I screwed and CA'd the wheels so those babies are not coming apart!

Oliver, thats a genius solution. It almost makes me want a go. Fortunately I have already assembled my wheels. Phew - dodged a few hours there. All the best with the rest of the wheels. Nick

Roy, Having got my Top Studio set and read all your posts I am compiling a (not serious) list of things I will need comprising: A full hazmat suit with respirator and eye protection to keep me safe from resin dust and glass fibre fragments; a medical grade stereo microscope so I can see the screw heads and probably eyeball upgrades too: beta blockers (and the odd stiff drink) to steady my hands; a fire extinguisher for when annealing gets out of control and industrial quantities of CA remover. Have I missed anything? More seriously, I love the attention to detail in this build, an inspiration. All the best Nick

I think that may be beyond me currently. Olivier's wheels look superb. My poor Mef has some other issues. The RH front upright has broken and needs fixing. Too much CA me thinks. I'm also struggling to drill 2 holes accurately.How hard can it be - my success rate was 1 in 4 this evening! My skills still need significant honing. And as you might have seen my head is being turned by an MP4/6. However, all that said, I am still enjoying the progress I am making. Oh and no worries about the pics. I look forward to seeing them whenever. ATB Nick

I've always felt you can't have too many photos of a BT52. It always looks like a rocketship. Excellent

Sam, Thanks for getting back to me so quickly. I'll probably have a play with it over the next few days. It all looks a bit flimsy and delicate. Not got a good record drilling microscopic holes in things so it will be intersting how it goes. ATB Nick

Sam, No worries. One question: how did the carb pipework work out? I've just got to that bit and wondered what solution you used in the end ATB Nick

Sam, No offense taken or apology needed. I wrote in the first place because I just plucked up the courage to dremel the carbs per one of your earlier posts and been pleased with the results. Also I have just realised there is a treasure trove of ideas in the earlier posts that I missed first time round. Masking the sunflowers for example - genius. On the subject of colour. Mine is bright read because my skill level would not allow me to re-create a 90 year old paint scheme credibly (though some of my old modelling attempts with thick paint and brush might have been quite believable!) Anyway... Mef in its current form would be hard simulate. The body carries all sorts of dents and ripples, I stopped at just reskinning the middle section to give a believable step. That was scary enough for me. This is Airscale terriory. Then several layers of red would need to be applied (badly) and chipped off. To add to the fun, the left had side carries a lot of heat damage. The top coat is quite glossy but seems a different colour on each panel and clearly 90 years of dirt and crud (aka patina) has been lovingly removed so the nooks and crannies don't look dirty and spidery. I look forward to watching the first person to take on this challenge. It might be easier to represent the car as it might have been in the 20s, semi-black and covered in oil and soot. That would also be worth seeing. ATB Nick

Having started the Mef some time ago and contributed on another forum, I read this thread and Sharknose's comments with interest, specifically. Sharknose: " The other builders i saw, with my respect to them, either stopped or were satisfied with a basic OOB build. Most chose a monotonous quasi-chromophobic paint job. With due respect this is not valid for this car, who's body paint appears to be made of different hues." I have no problem with any problem at all with the comment, guilty as charged. Mine is a completely unrepresentative shiny red, but it looks, to my eye superb, and perhaps more importantly, represents the first time I have ever managed to get close to the level of gloss finish that others achieve on this forum. And that probably is the point. I would never have thought to have tried some of the things I've now done without LittleAndi, Sharknose, Jeremy, Codger, Caterhamnut and a number of the aircraft guys. The real value for me is to build the confidence to try and more importantly fail and then be able to recover the disaster. I am doing things now that I have never done before. So I look forward to 70 spoke wheels, paint crackle, and the myriad of other ideas that you will try that would not even occur to me. I will continue to plod on with my still unfinished but progressing Mef. I now can do really nice stained varnished wood effect, it should be really useful on my next project a Mclaren MP4/6! Regards Nick

Impressive that you got that back - I have been there but had to live with the results. Post havoc the part is better than I manage. Very impressed with the build so far and the other four or is it five threads you currently have running Nick

As you say, you will know.

Roy Thanks for the support. I'll let you know when I start. It will be interesting to see just how "competent" I am. Still not sure I would try to rebuild the dynamo, it would require an eyeball upgrade (that the finance director would veto in favour of a new patio). ATB Nick

Roy, I've been hording an MP4/6 for 10 years. Lack of skill and the existance of detail sets that one can't get hold of have stiffled the urge to rip the packaging open and start sticking stuff together... Until now. On the strength of this thread I bought the full detail set (never done resin or photoetch before) today. As the youth of today might say O....M....G what have I done. Will continue to watch with interest. Worried my org skills will not be up to the standards you have set so far. It would never have occured to me to do anything other than live with warp. Thanks for the inspiration. Long may it continue. I am going to need it. Nick

Richard, I've not commented on this forum before but I followed this thread from afar and looked forward to updates. Seeing your update prompted me finally to pen something. It would be great to see this model of my favourite aircraft restart. Even if it doesn't, you have shown an enthusiastic but not very productive modeller what can be achieved. Thanks for sharing your endeavours with us. Regards Nick