1/8 Porsche 956

[ScratchBuilt]

Hello again!

It's not really a surprise, but this new project of mine will be a 1/8 scale scratch-built Porsche 956. This was Porsche's first design for the new-for-1982 Group C sportscar rules and it would enjoy a lengthy (and successful) career as both a factory racer, and a customer car.



This is the Minichamps 1/18 version of the 1982 Le Mans-spec car...and for comparison with the Moby Dick:



What am I letting myself in for?!

So, why a 956 and not the later 962? The main reason is that from various books I have several useful chassis and layout drawings, all of them 956-spec. I know that one of the main factors in the 935 'Moby Dick' taking so long was the lack of proper reference drawings – and it's not an experience I want to repeat! A second factor is that the earlier 956 is very closely related, engine-wise, to the 935-78. It has water-cooled heads, but still the traditional air-cooling for the cylinders and block. I'll be able to use most of my photos and references from the 935 to make the new engine for the 956.


A big challenge will be the creation of the aluminium tub chassis – not the usual 908 or 917-style tube-frame. Fortunately I have plenty of photos for this, both from books and from online searches, and the drawings. Of course, there will be plenty of other problems along the way – headlight covers and door hinges, for example – but I'll deal with those as they happen!


What's interesting (to me, anyway) with the 956 is that it was clearly a fresh start for the Porsche racing department, and you can see that in the design of many of the components. Throughout the 70's there was an obvious connection with all of the racing prototypes, from the 908 to 917, to the original 936, then the various updates running through to the last 936 in 1981. The frames are similar, the brakes and uprights are similar, the gearboxes are similar, etc. Although the 956 borrowed the 917's windscreen (sort of), everything else is fresh, and seems more 'refined' than the 70's cars. I suspect this will cause me a lot of headaches as I try to balance strength and durability of the parts, with the more detailed nature of the design.


Unlike my other projects, I am starting this one without a specific chassis identity in mind. The 956 was available with both 'long tail' bodywork for Le Mans, and 'short tail' bodywork for normal circuits – I prefer the look of the 'short tail' despite my love of Le Mans! Maybe I make both types of bodywork? I could go for a factory livery, or one of the privateer teams...lots of choices. At this early stage it's not too important – I won't have to commit to these details for a long time yet.


I started the build at the very end of 2018, during the Christmas holidays. After completing the 935 in mid-November I was ready to move onto something new! My first job was to create a scale drawing of the chassis tub, and to use that to make a cardboard mock-up. I wanted to get a feel for the size and shape of the tub, and how it differed to the tube-frames I was familiar with. Later, I could use the dummy tub to work out how I could mount the engine and gearbox – what's possible in real-life doesn't always translate to model-form, even at 1:8 scale.





The tub as you see it here only took a few days to put together. It's mainly thin cereal-packet cardboard, with some styrene box-section added in places for strength and alignment. The curved floor section in the footwell adds a bit of complication, but the overall shape is relatively simple. At this stage I haven't added all the little brackets and suspension pick-ups – these are all details that I will work out on the proper tub.





Having made the mock-up, the next question was: how to make the actual tub? It's supposed to be made from folded aluminium, so a smooth finish is necessary – I'll have to spray it eventually. Styrene sheet on its own will probably not be strong enough, and could lead to problems with distortion or glue-related pitting over time. I could make a tube frame and add outer panels, but would it be strong enough? My current thinking is that I should make foam cores for the main side-boxes, then add fibreglass, then a thin styrene skin. Hmm...how about a thin aluminium skin?


Either way, the weather for the first two or three months of the year would not allow me to spend much time working with fibreglass, or making a mess with foam out in the workshop. Until things warmed up a bit and the evenings start to get lighter, I would do something else to advance the project.


To work out how to mount the engine and gearbox properly, I would need an engine (or at least the block), so that's what I've been doing since early January. Construction is basically the same as for the 935, so I won't go into lots of detail at this stage – there'll be lots of things later which are specific to the 956. I've tweaked one or two little things here and there – partly to find improvements over the 935, and also to keep things interesting!







So if I'm building one engine, I might as well build a second at the same time, right? Might come in useful sometime in the future, and it hasn't really taken much longer – I've been leap-frogging between them: while the glue's drying on one, I'm working on the other. I've concentrated on getting the two blocks detailed before moving on to the heads, cylinders, etc.


On the 956 there's a large fabricated mounting which bolts to the front of the engine and tilts the entire powertrain upwards by a few degrees. The first step with this was to connect four 1/8” tubes with lengths of box-section to make a simple U-shaped spacer – this would be the core of the front mounting:




The rear of the engine is supported by two large A-frames which bolt to the back of the main chassis tub at the bottom, and to the roll-hoop structure on top. Between the engine and main gearbox is a spacer module which includes two large arms – these arms spigot onto the A-frames and tie the structure together. The next step was to make a dummy spacer module from box-section and 0.75mm plate, and use this to set the engine at the correct angle:





At the top I've used two short pieces of 4mm tube to represent the base of the roll-hoop structure. For now the lower ends simply rest inside the brackets, but on the proper tub I have various options for running the tubes into sockets hidden inside – this should allow some adjustment, but also create a stronger connection than simply pinning them through. Being able to assemble and dis-assemble the drivetrain is an absolute requirement, but it helps if everything goes back into the correct position each time!


So, at this point I now have 75% of the drivetrain dummied-up on the back of the tub; even like this the engine is quite stable. The A-frame construction will be modified for more strength – possibly by running aluminium or brass tube inside, as on the 935 – I'll pin the ends together, and can work out the final fixes onto the back of the tub. The two lower brackets, for example, will effectively be purely decorative as the structural connection will be inside the tub.


For the last week or two I've been working on the proper front mounting. I re-made the U-section around longer lengths of 1/8” tube – my plan here is to run these into sockets inside the tub for an even stronger mounting. The engine's fan drive-pulley will fit inside the arms of the U. An angled 0.75mm plate across the front creates the basic shape of the mounting where it will attach to the back of the tub. Smaller lengths of tube at each corner can be used to pin the mounting in place (although this might not be necessary with the longer 1/8” tubes available), and these are reinforced with pieces of thick strip styrene:






Two 0.75mm plates close-off the back of the mounting, and I've added two sections of 11mm tube to create the swaged holes present on the original 956 part. The front plate has no holes (for strength, and they're not going to be seen). At some point I'll add some weld detailing around all the edges with Greenstuff and then it's ready for paint:


What's next? However I make the proper tub I'll have to mould the floor in fibreglass, so I guess I need to start thinking about shaping some foam to make the pattern. Assuming the weather doesn't revert to winter-conditions in the next couple of weeks I could think about laying-up some fibreglass soon. I'll need to make some more flat-sheet for use on the project too, but that's easy enough. I'm still undecided about the tub construction...If I can convince myself that an internal tube-frame will be strong enough, that could be the answer, but the shaped floor will certainly add to the challenge! Hmm...needs more thought.

Sorry if this first post has been a bit wordy - I knew it was going to have to be a long one, so actually started writing it a couple of weeks ago, and only copied-and-pasted it together with the photos today! Normal service will be resumed soon once I get the proper tub underway. I wanted to satisfy myself that the basic layout was sound before committing to a new thread...and here it is.

If I can get this one built in less time than the 935, I'll be very happy...!

SB

[freakray]

This is going to be fun, can't wait to follow this build!

[jaykay640]

Following!

[nugundam93]

another awesome build!

[lemansnut]

Oh yeah, can't wait to watch this one unfold! This is going to be epic! Second engine? Why not for the Dauer 962.

Mike

[lasagna99]

great project!So do you choose for the very first version of the 956?
in the engine compartment it had some differences compared to the following versions ('83, '84 ...), but I imagine you already know …

Great start!

[360spider]

Buckle up, AF.

[sky1911]

Another master class is about to start, and boy are we in for a treat.
Considering you just "happen" to build two engines at the same time, can I hazard a guess and ask if, per chance, we are going to see different versions? Or is it a preparation for the model after this one? :P

Great start. I love how you go about the process of reverse-engineering a real car and then recreate it in almost household materials. I've been stumped 2 times already with the projects I've seen here come alive (908, 935) and now I'm in for number 3 (I was too late for the 917).
As for the chassis. I would think about thin sheets of aluminium. But that is just my personal preference, because I like to have things made from their original material instead of painting something so it looks like what it really isn't. Plus I suck at painting. And at these size metallizer paints (or whatever you call them) like the xtreme metal paints from AK or Alclad etc. are going to be a pricey proposition. That aside, the metal would be a good for structural integrity and stability - but of course with the downside of adding quite a bit of weight that the suspension needs to be able to carry.

Hm food for thought, but hey, I'm glad you have to do the thinking and I can just sit back and enjoy the ride .

Did I say brilliant work so far? Consider it said :P

[ScratchBuilt]

Hello folks,

The tub is certainly giving me some mental exercise as I try to decide on a plan! The cardboard mock-up is surprisingly sturdy, despite being put together relatively quickly, and as I don't have to worry about fitting a fuel tank into the rear bulkhead section I've got a relatively free hand in how I construct this area. The various holes and openings in the tub are going to be the things causing problems - I'll need to run pipes and cables into some of them, for example, so if I go down the foam-core route I'll have to start putting holes in it anyway. A concealed tube structure is appealing, but most of the tub is quite thin in cross-section (and will be even thinner once I allow for whatever outer skin is used).

I'll have to so some digging around in the scrap aluminium bin at work and see what I can salvage! Most of what we use is going to be fairly thick compared to a 1/8 model (eg 16swg) but there might be some thinner 18swg or 20swg offcuts I can experiment with. Although using proper ali has the obvious advantages in terms of colour and texture, I can see problems with detailing it (gluing, discolouration, scratches), and if it's thin enough to use on the model it might not be as rigid as I would like.

Yes, the engine installation does change over the years, so the current plan is 1982-spec with the Kugelfischer mechanical injection. I believe that this arrangement continued in use with some of the privateer cars during '83-'85, so I'm not just limited to using an original 1982 livery. Either way, I can make a final decision about this further down the line. It might just come down to what decal sets I can find to supersize...but I suspect the 956 is well-served in this respect. I have a few 1/24 956 and 962 kits in my stash already, so that's a start...

The second block just seemed like a good idea - even if it doesn't end up going into a car, I could finish it up as a display piece. It does mean that I don't have to keep removing and re-fitting the primary engine every time I want to check something, so I'm sure it will be of use as I make progress. Having all the photos on file from the 935 build certainly made life easier, and there wasn't that feeling of 'will it or won't it work?' from the first time. Of course, I will still have to build a new gearbox and the adaptor section, so I still have fresh challenges there!

SB

[ianc911]

A good choice of an interesting car which will present some new challenges for your fabrication skills. I'm surprised that a box section of thickish styrene wouldn't be strong enough for the tub? I guess I don't really have an idea what one of these monsters weighs.

Looking forward to your (always entertaining) build reports. Hope you stick with the Rothman's livery!

ianc

[Martini Man]

awesome start, looking forward to this journey.


Paul

[ScratchBuilt]

Hello again,

Right - change of plans! Before throwing myself into tackling the tub I felt it was necessary to spend a bit more time working on my 1/8 scale layout drawing, to get a better feel for the size of this thing. I've decided to put the tub on hold for a little while: I need to make the outer tub sections (sidepods) quite structural to support the weight of the main bodywork, and as these will be permanently fixed in place, I might as well incorporate them somehow into the main core monocoque.

The other issue is that the rear undertail and venturi tunnel bodywork section continues underneath the sidepods - it doesn't stop at the front edge of the engine bay. There's no point in making the tub and sidepods before I have the drivetrain in place to determine the shape of the undertail. It will all make sense in time!

So, new plan: make the adaptor casting which supports the engine and gearbox. I managed to find some more good photos of this online to add to what I already had - but struggling for a good clear view of the underside. I spent several nights drawing the basic shapes to scale and working out a plan, before starting to cut plastic. First stage was to make a series of plates and rings to create the front section around the engine's flywheel:







The rings were made by wrapping and gluing several layers of 0.75mm strip around a 'D' battery. The main body is 3/8" box section, with the ability to run a pin through from front to back, as shown. The notch at the back is where I will fit the crossbeam which will connect the two A-frames on the back of the tub.

Next stage was to start creating the rear end - a single plate to define the connection to the gearbox, then two more rings:



Finally for tonight, I've made a start on the underside. The four tubes on top will be the anchor points for the forward mounting for the lower wishbones, and these will be firmly supported by plates and pins. The plate on the bottom creates the split-line - the upper section of the adaptor has a removable cover which allows access to the clutch and release mechanism with the drivetrain still assembled. I can't fix this plate permanently until I've done more work on the crossbeam, but once it's in place I'll be able to start adding more detail to the sides.



So, work will continue - hopefully the next time you see it it will be looking more like the real thing. Once the adaptor is under control I can make a start on the actual gearbox, and then I can start thinking about the undertail…

Have a good week,

SB

[SchuberT]

Holy cow. Do you ever take a break? Haha

Excited for another great experience!

[360spider]

Wow.

[iliasbass]

gosh! this is amazing!!!!