1/8 Porsche 956
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
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