1/8 Porsche 956

[tyrrell]

Hello. Beautiful and thoughtful work. (My models would also look better if I spent so much time preparing.) I have one suggestion. Try to make the chassis from styrene coated with thin aluminum. I tried alu from a party tray. It's thin enough. The bonding of the parts is also solved because styrene is well bonded.
I will follow this project closely. It's great and informative.
"Tyrrell"
this is a translator, sorry for imperfection

[JesusM]

I'm here again for learning!!

[ScratchBuilt]

Thanks for everyone's comments and 'positive vibes'. You'll have to forgive my slow updates so far - it's one of those times where the progress seems to take a while to happen, despite lots of hours spent making large pieces of styrene into small pieces! As you'll see here, things are certainly moving along.

Having got the main body of the engine / gearbox adaptor under control, the next job was to tackle the beam (or 'ox-bow') which would connect the two A-frames. The core structure was put together from 1/4" x 1/8" box-section:



This would be combined with the top plate and more plates on the front to create a solid support for the back end of the car:



Of course, there were lots of other pieces required to make it all work - here's a selection before I started gluing it all together:



You can see that I filled in the ox-bow with various pieces of box-section for reinforcement. The two aluminium tubes are the main connections to the A-frames - these are slotted for the pieces of styrene strip to fit inside, which will plug into each end of the main cross-bar.

To increase the structural strength, I wanted to pin through into the sides of the module (rather than just relying on glued joints). You can see one of these pins below:



The circular boss is one of the two mounts for the top rocker of the suspension. There's more to add to this, but I wanted to create a solid socket to pin into later on. I used sections of angle to build up the shape of the rear part of the ox-bow, with the plan being to either fill in the gaps with greenstuff or styrene, before adding more plate-work to finish off.

As you can see here, I used more styrene to shape the back, and more on top:



There's a 0.5mm gap between the rear of the ox-bow and the plate which defines the back face of the adaptor. This will allow me to slot in a piece of 0.5mm styrene sheet each side.

Jumping forwards a bit, here's the adaptor in it's latest state:



I addition to the two 0.5mm plates on the back, I've wrapped two more pieces of styrene over the top and undersides of the ox-bow. The ali tubes have been fitted in place, and the styrene wrapped around them. This arrangement is a little different to the real car, but I've done it this way for extra strength - it might be modified later on.

At this stage, it's not really necessary to continue adding more detail to this piece. For what I need to do this summer, I just need to connect together the basics of the engine, gearbox and adaptor in a solid and repeatable way.

So, time to start on the gearbox itself. First job was to make a scale drawing based on measurements taken from the various official drawings, combined with info from the many photos. As with the 935, I'll make it in three sections - diff housing, gear cluster, and the end-cover - rather than trying to do it all together.

The starting point for the diff housing was the front plate where it connects to the back of the adaptor section. This includes six thick bosses where the bolts go through, so these were made from 4mm x 2mm strip, rounded at the ends. A 1mm disc was cut and inserted between the strip sections, with a further 0.25mm plate on the back to tie it all together:



The square plate will form the backbone of the diff housing, made from more 1mm styrene. The two sides of the housing are quite different, so I can build them up separately. One of the hardest pieces will be the cover plate on the RH side:



Lots of detail, lots of fins, webs, and all sorts of stuff that will take time to sort out! It doesn't help that I don't have a proper square-on view of this side of the gearbox, but I'll work with what I've got. The 935 was similar, so it's not my first attempt at this sort of part! I started with the disc of 0.5mm styrene in the photo above, then added two rings of 0.75mm to give it some depth:



The notches around the edge will need some work, and there will also be small bulges on the inside and strips running to the centre. It's a long way from being finished, but once I have the two side-plates they will play a big part in defining the overall shape of the diff housing.

Let's see what happens!

SB

[jaykay640]

Love it!

[kalax]

So cool!

[Kombi]

Your scratch building capabilities are just unreal.



I can't wait to see your progress on this one.

[ScratchBuilt]

Time for another update!

As it turned out, the cover plate for the RH side of the diff housing wasn't too bad. Having marked it all out and added the edges (as seen in the last post), everything else was basically just filling in the gaps. A short length of 11mm tube was glued in the centre, and then it was the time-consuming job of cutting and shaping the 24 fins. After that, very short pieces of strip were added between the fins to create the middle ring:



Next, I could start building the diff case itself. Four strips of 0.4mm styrene were layered together around a useful offcut of nylon rod to create the central 'drum' section. Assorted discs of styrene were cut and used to locate the drum onto the backing plate, and the cover plate:



In this photo you can also see the early stages of the bellhousing section which will attach the gearbox to the back of the spacer / ox-bow. The main positions of the mounting bolts have been fixed by the three sections of strip with the rounded ends, but there will be more work later to make the transition to the diff-housing.

Here's a shot of the main components at an early stage before I started gluing things together:



From the left we have the LH side of the diff-housing. The detailing for this is quite different to the other side, as you'll soon see. Next we have two small panels, made from various pieces of strip, which are the starting point for the flange between the diff-housing and the gear-cluster section. Then it's the RH side of the diff-housing, and the front plate.

Fast-forward a bit and you can see how things have developed:



This side of the front plate has had more sections of strip added which will define the positions of assorted 0.75mm webs - these will run across the side of the diff housing and meet-up with more from the top, bottom and rear. The centre piece has been bulked-up with lengths of 0.5mm strip to create an internal chamfer; my original plan was to then fill this with greenstuff and smooth it out, but when I started cutting the slots for the webs the greenstuff didn't key properly and pulled out! For now it's had some work with emery cloth, and will be fettled more before it's complete.

These shots give you an idea of how the webs will slot into place:





By the time of the second photo I've started adding more strips to control the webs across the top of the gearbox too. The curved section in the middle of the photo was built up from five layers of 1mm sheet, then lots of sanding to add the chamfer. Once the basic web positions were fixed, I could cut this piece into sections to fit in between.

The two sides of the diff housing have been glued together, and the front plate has been added too. Here you can see how the central spine now has extra strip on both sides for the webs:



So, still a lot to do. It feels like it's been slow progress, but there's a lot of effort in these parts, and a lot of trimming, fettling, positioning, thinking and finally gluing! Now that this core section is glued it should help as I'm not having to hold it all together whilst I work out what to do next - things stay in place. I've rough-cut a lot of the webs already, so when I'm ready it will start looking quite different quite quickly. The underside needs more work where the wishbones will attach, the rear needs work where it meets the gear-cluster...and the top needs work too.

Getting there, though!

Have a good week.

SB

[360spider]

Simon, your scratchbulding skills are out of this world, but to me, its your vision on how to approach certain things that makes your model building so unique and SO good.
Terrific update once again my friend, and please keep on building!
Patiently awaiting next installment!

[ScratchBuilt]

Hello again,

Sorry it's been a while since the last update - the back end of the gearbox has taken me longer than I planned to get to this stage, so I've been waiting until I had something useful to show before posting.

Adding the web-plates to the diff-housing was certainly much easier having first put the pieces of thin strip in place to locate them:



At the front I added shaped pieces of styrene to create the curved transition between the back of the adaptor and the gearbox. Again, much easier to do with the webs firmly held in place...but still removable if necessary:



The transition piece on the other side was smaller, due to the size of the diff cover plate. This started life as several pieces of rough-cut styrene glued together, and then filed and fettled to shape:





At this point I realise that I haven't taken any photos of the diff-housing in it's 'finished-so-far' state. No problem - there'll be a few of these next time as I have to return to it to continue the mounting flange onto the gear-case.

The gear-case itself is what's been occupying most of my time since returning from Le Mans. I knew it would be constructed in a similar way to the 935 - split into sections either side of a centre-plate, with the webs added in between - but I wasn't totally sure of the shape. The two halves are not symmetrical - the selector mechanism is on the left-hand side - so I had to make eight different sections, each comprising a top half and a tapering lower half.

Having drawn-up the basic layout, I started putting the sections together from various sizes of box and strip, with an outer skin of 0.4mm strip added at the end:



The web-plates have been rough-cut from 0.75mm sheet and their shape will be refined as the gearbox is assembled. The upper and lower pieces all sandwich a further piece of 0.75mm strip, creating another web down the length of the case:



As with the diff-housing, I made the centre plate from two 0.5mm plates, allowing me to glue the two sets of sections separately. The web-plates are not glued at this stage, but are in place to make sure everything is correctly positioned during the gluing process:



After this I could start trimming the backing plates to shape, and eventually glue the two halves together. I cut a small slot inside each of the plates to create a 1mm hole on the centre-line, allowing me to pin the gearbox together. It still needs more work, but it's looking better:





It's only when all four sections are fitted together that you appreciate the size of the 956 powertrain - and I still have to add the gearbox end cover:



So, what's the plan from here? First, I need to spend some more time working on the mounting flange detailing between the two sections of the gearbox. There's still plenty more other detail to add, but that can happen later - I can do a lot of this during the winter months.

I really want to spend some time shaping the underwing and floor in fibreglass before the end of the summer, so I can make use of the better conditions. To do this I need the basics of the powertrain in place, together with the cardboard chassis tub, etc. My original plan was to have these basics in place by Le Mans, but that deadline has now slipped slightly!

I reckon another week or so should put me where I want to be, then it'll be time for more drawing, blue foam, cardboard and hot-wire cutting. I'm still undecided on the chassis construction, but I'm hoping that having the floor available (even if I have to mould a Mk2 version later) will help to make the decision. If I can get some good progress with the fibreglass before the end of September, that should be enough to keep me busy into 2020!

All the best,

SB

[360spider]

Excellent update once again!

[ScratchBuilt]

Hello again,

Time for another update - to be honest, I hadn't realised that it had been so long since the last one. Quite a lot to report, though, as I've been busy - although not necessarily with the jobs I thought I would be doing!

So, early last month I was considering making some moulds for the undertray / floor panel. I spent a couple of afternoons playing around with some cardboard to make some mock-ups for the ground-effect tunnels, but I just wasn't happy that it was the right time to continue with this work. I still wanted to get some fibreglass parts underway, so I made some simple foam and cardboard moulds for the main tub floor and the inner and outer tub skins:



This is the floor and outer tub skin. The pencil lines are marked onto the moulds, not the panel - although when the panels were removed I was pleasantly surprised to see that the indentation has transferred to the fibreglass. It'll make things a bit easier when I start trimming. Here's the two side panels:



...and the floor:



Other than a wash to remove the greasiness of the release-agent and a quick trim around the edges I've not done any extra work on these. Each panel is a combination of five layers of different cloth weights, for a thickness of about 0.7mm. They'll lose a bit when they're sanded smooth, but as they won't be the outer layer I can adjust the total thickness when I add the styrene final skin.

Next up, a bit more gearbox detailing. Although there is still plenty of work to do here, I particularly wanted to sort out the area where the lower wishbones will attach. My photo references for this area weren't great, but what I've done is very much in keeping with the original design, and should provide a strong foundation for the wishbone bracket. It'll all be hidden when the undertray is fitted, but we all like to know the detail is there, right?





The main work for the last couple of weeks has been on the inner tube-frame for the tub. The cardboard version has been very useful as a reference - I didn't work out the frame design in advance, I just started making a structure that would fit inside the pattern. First step was a U-shaped base layer in 8mm x 5mm box:



This sets the internal width and defines the flat section of the tub where the driver will sit. Most of the rest of the structure you see here is made from 1/4" x 1/8" box, with lots of internal pinning for strength and location:



The section at the far left made from three pieces of box is where the front of the tub will slope upwards, and will eventually tie in with the rearmost mountings for the front wishbones. The rear of the tub below the fuel tank also slopes upwards, but this is where I will be incorporating the engine mounting.

It's only in the last couple of days that a lot of this has actually been glued together, so for most of the time it's been possible to take everything apart. The priority with the engine mounting has been to create a firm, strong structure - the positioning of the main beams has been defined by the external shape of the tub, so I've had to work the mounting tubes into them with a bit of filing and fettling:



After that it was a question of adding more tubes for reinforcement - both for the engine mounting, and to strengthen the overall frame:



Here's the frame as of this evening:



I've added 1/8" diagonals into the side frames, and you can see how the engine mounting plate slides into the four tubes that are now part of the chassis. The next challenge will be to create strong pick-ups for the two engine side A-frames, extend the rear part of the frame upwards and forwards to create the full fuel-tank section, and to taper the front towards the pedal-box. I can see that I'll be busy with this for some time to come, but with a holiday next week I should be able to make some good progress before the next update.

Have a good week,

SB

[360spider]

Nice. Where do you get your info as far as the design of these elements? I assume there are books and blueprints online, was just wondering, as you reproduction seems very exact.

[ScratchBuilt]

Hello 360spider,

There's various drawings of the chassis, suspension, etc, in assorted books I've collected over the years, but everything I have is for the 956 rather than the 962. As with the Moby Dick there's a lot of useful photos on the Freisinger Motorsport site, and some good stuff on the Pelican Parts forum, so I'm pulling lots of info from those sources. There's enough info on the gearbox and spacer module on one or two of these drawings to get the basis dimensions 'about right', but the rest comes from searching the books and online images. The engine will be very similar to the 935-78, so that's less of a worry - I've got lots of photos of what I made last time!

The problem, of course, is working out the little details that are 956 or 962-specific, or the cars that are genuine Porsche tubs compared to the ones made by other workshops, or simply the fact that over the years many things get altered! That's why for now I'm not basing this project on one particular car - there's not really enough reference material on any single chassis. It'll probably end up with details from several cars, and the livery will depend on what I can paint, and what I can make decals for! Fortunately I have a few un-built 1:24 956 and 962's in the collection, so they might be donating their decal sheets to the project, as per the Moby Dick...

The tube-frame is my design, working to fit the measurements of the original aluminium tub. It probably won't be as elegant as the genuine frames for the likes of the 908 or 917, but as it won't be on show I'm looking for strength and stability, rather than a 'perfect' frame. It also means I don't have to add all the weld details! Given how sturdy my original cardboard pattern tub is, I'm hopeful that the styrene-and-fibreglass version will be up to the job. These 1/8 cars get quite heavy, though, when you start adding the transmission, bodywork, etc.

SB

[360spider]

I see. Well, you are doing heck of a job. Keep at it, I am following this build closely.

[John18d]

As usual SB - unF*ing believable work

What you can do with simple styrene is very impressive.

I'm on board for this build.

Cheers
John