1/8 Porsche 935/78 'Moby Dick'

[puffyrs]

Very nice.

[ScratchBuilt]

Doing donuts this week!

Yes, I've made a start on the driveshafts and a main part of these are the two rubber donut joints (as also seen on the 917, 908, etc). A simple enough shape, but there's quite a lot of work involved. First step was to cut the basic hex plates from 0.75mm sheet, using a template, then to add the six pieces of 3/16" box-section. Once glued together, the centre of the donut can start to be removed:



Each corner was then filed away to create a groove for lengths of 2.5mm rod. The inside of the donut was filed away to give a smaller hex-shaped hole, and short lengths of 2mm half-round added in the corners. When the glue was dry, everything was filed back to flat with the top surface. The short connecting pieces started as 2.5mm x 0.5mm strips, rounded off at the end and tapered slightly along the sides:



To connect the donuts to the shafts I need four 'spider' plates. I re-used the template I'd made during the 908-03 project and cut four from 1mm sheet. A bit of filing later and here they are:



I might still slim them down a little more - I'll continue with the shafts and see how they look later. There will be hex-nut detailing to add to all this when it is assembled, of course.

Now I have to start on the fun part - making the universal joints at each end of the shaft. It's going to be a fiddly job, but having already made something similar on the 908 I'll be looking for ways to improve them. This will keep me occupied through the rest of the week...

See you next time,

SB

[Interceptor1955]

As usual a fantastic work you've done SB.
Always looking out for the next update.

Mark

[ScratchBuilt]

...and here is the next update.

Starting point for each of the universal joints was two 1/4" lengths of 3/8" box-section; pilot holes were drilled through two sides, then the third side was removed to create the C-section. The inside faces were reinforced with two lengths of 0.5mm strip. The pilot holes were taken out to 1/8", then each half of the joint was pushed onto a length of rod (to make it easier to hold) whilst the ends were rounded-off with file and emery cloth.

From here, each of the joint sections was modified to suit it's position on the shaft. The innermost ends (onto the gearbox) were given a slightly thicker base and some half-round detailing to create the gearbox output flanges, plus a central spigot to help locate them in place. The other half was given a two-stage spigot which would pass through the first of the two spider flanges. The outermost joint was designed to locate into the hub in the trailing arm, whilst the other end was attached to the driveshaft itself.

To allow for a little movement as the suspension was articulated, the outer end of the driveshaft is able to telescope into the inside of the donut joint - an internal tube provides support.



Here you can see the two complete shafts when assembled for a trial run. The spider flanges have been drilled through into the two donuts with short lengths of styrene rod used to hold everything together. The cross-shaped 'spiders' inside each joint are made from three short lengths of 1/8" tube, with pins pushed through from each end to allow them to pivot:



In this next photo you can see that I've added hex-detailing on both sides of the donuts, to create the nuts and bolts which would pass through the spiders. The outermost ends of the shafts have been given a curved underside (using a section of large-diameter tube cut to shape) with some greenstuff to fill the gaps.

The small pins pushed into the universal joints are not permament. Each shaft can still be broken down into parts to allow for easier painting (whenever that will be!). It's tempting to glue the donuts and spider flanges together now, but it would be very awkward trying to get a brush into the inside.



The next job was to re-fit the engine and gearbox and see how everything looks. Here you can see the two driveshafts with the suspension on full droop - note how the left-hand side clears the starter motor:



With the wheels fitted the driveshafts lift to a more conventional angle - just slightly below horizontal. The outermost universal joints are buried inside the trailing arms and nearly hidden from view - I could have saved some time and effort here by leaving out this joint completely, but that's not the way, right?!



Another photo at ride-height, looking towards the back of the car:



So, at this point the two shafts are about as complete as they need to be (for now). Time to move on to the next job!

More at the weekend.

SB

[kohula]

Fantastic job! May I have a question? What type of putty do you use? I meen the green one.

[ScratchBuilt]

Thanks, Kohula. It's 'Greenstuff' from Citadel / Games Workshop. As well as the normal yellow/blue two-part solid version, they also make a pre-mixed liquid version that you can apply with a brush.

Hope this helps!

[Martin S]

I guess the best thing with not loggin in on AF for about two years is that your favourite builds has come a long way...
I just spent the last half hour browsing through like 17 pages of amazing updates of scratchbuilding at its' best !

[ScratchBuilt]

Evening, all,

Thanks Martin - glad you liked it. I have a feeling that you could come back again in another two years and there's a good chance the build will still be in progress! We'll see...

So, when I finished working on the driveshafts last week it was a question of what to do next. Having been on the gearbox since early April I returned to the engine - time to start on the top half of the heads.

The first stage was to make a pair of inserts which would drop into the top of the engine and create the core structure - all the extra detailing would be added later. Each insert was a mix of three pieces of box-section, some solid-section, and a very thin strip - I've cut a slice on the left of this photo. The flat plate on the end would allow me to mask the joint between the top and bottom sections:



I added a similar smaller plate to the front end of each insert, and you can see here how they drop into place:



At the flywheel end you can see how I've started adding some detailing to the flat plates - a lot of this will be hidden later by water pumps, etc, and there will also be a couple of closing panels over the finned cylinder-barrel area. Once the engine is installed in the car, you will see even less...



Next stage was to create the bases for the six inlet trumpets - starting point was a length of 1/4" x 1/8" box, some 1mm strip either side, then two extra pieces of 1.5mm strip:



...and here they are all assembled and glued in place on the two insert blocks:



I've marked and drilled into the top of each one so that I can pin the inlet trumpets in place - these are the next (fiddly) job. I have a feeling I'll spend several nights playing around with small bits of tube and box-section making a prototype, before I can push on the real thing...

Have a good week,

SB

[ScratchBuilt]

Hello again,

I've left it a couple of weeks before updating - I wanted to have something worthwhile to show! I've been busy working on the inlet stacks and the intercooler structure, and it's all slowly coming together. The starting point was making the cores for the inlets - 18mm lengths of 9/32" tube, with a band of 1mm x 0.5mm strip wrapped around each end. Slices of 3mm half-round were added to create the flange detailing, using a simple fixture to keep them aligned properly:



Make one, then make five more! The half-round pieces were filed smooth on each end to bring the length back to 18mm overall. Each stack sits on a short stub which is part of the head casting - I've pinned all these together with smaller sections of tube inside to keep everything in place:



In time the square flanges at the bottom will be fettled into shape. Next job was to create the two intercooler bodies that sit on top of the inlet stacks - I had to play around with the box-section for a while to get a suitable combination. It's worth remembering that most of these measurements have come from comparing several photos of the engine and scaling from each one - as long as it all fits in place, that's fine!



The centre section of each intercooler was given a wrapped layer of 0.4mm sheet - I added some reinforcement under the sloped sides to hold it's shape. The real things appear to have a very fine almost 'crackle' type finish - I think some experiments with textured paint may be in order eventually? You can see here how everything fits under the bodywork:





Here you can see how everything comes apart and spigots together:



The ends of the intercoolers were blanked off easily enough, but I also had to add two shallow curved end-tanks. I re-cycled some offcuts of old curved fibreglass to provide a backing layer, added an outer styrene skin, then a pair of sides to finish it off:



The forward ends of the intercoolers will have simpler square end tanks where the pipework will connect, but these will wait for another time.

The final job for this update was to add some detailing to the inlet stacks. Similar castings were used on the 1978 935 and 936 engines, and also on the 956 and 962 engines, so there are plenty of photos to work with - the trick is working out which bits are appropriate for the Moby Dick. It's clear from the photos that they certainly tried at least two variations for the intercooler layout, but there also appears to be small differences in things like the positioning of the fuel injector pipes. The engine in the Freisinger car is subtly different again in other ways...

Here I've added some waisted plates to the front and back of each inlet, plus some 1/8" tubes for the fuel lines to connect to, and the connecting sections between the three cylinders (part of the throttle mechanism):



I've also done some work on shaping the lower flange that each inlet sits on - the top flanges attached to the intercooler are supposed to be square. In this final photo you can see where I've added four small wedges to each inlet - these measure 5.5mm long, 0.5mm thick, tapering off from 1mm. There are also four more on the other side...not the easiest of things to cut! They'll need a little tidying up now they're in place, but the final effect will look good - not that you'll see too much of them when it's all assembled.



The rod through the top of the stacks will be the eventual position of the throttle mechanism - this will be added later. I've now got to finish working on the parts for the second set of inlets to bring them all to the same level before starting the next job. I'm tempted to get the fan and shroud sorted out - once this is done the engine would surprisingly complete, plus it would make it easier to create the fuel injection pump, throttle mechanism, etc.

So, that's it for tonight. I'll continue with the inlets and see what happens...

Cheers!

SB

[lovegt40]

mamma santissima... :o

[nugundam93]

Originally Posted by lovegt40

mamma santissima... :o

^^^ what he said.

[ScratchBuilt]

LoveGT40 - I'll take that as a compliment - thanks!

Quick update tonight - my connection keeps dropping out on me, so I want to get this on before it goes again!

Firstly, in this photo you can see the intercoolers with the small curved end tanks added. I've also glued the three pipes to the underside of each one, although the square flanges are still free. You can also just see where I've added some greenstuff to the 'hourglass' plates on each of the right-hand inlet stacks - I'll show this better in the next update, as I have to repeat the process on the other side.



Next, the fan housing. The main hoop was made from four layers of 0.4mm sheet wrapped around a 3/4" socket from a toolset (hey, it was just the right size!), with a 0.5mm flange added to the front end to tidy it up. Extra bands were added around the outside from 0.75mm strip, and a couple of bushes added - these will eventually provide the mounting for the alternator. Later this week I'll make the securing strap which wraps around the housing.



Finally, the fan itself. Again, more layers of 0.4mm sheet, this time wrapped around a till-roll core. The blades are cut from 0.75mm styrene, about 10mm long by 3.5mm wide, curved to match the side of the central hub:



I've reinforced each blade by drilling through and adding a single pin at the base of each one - you can't see them once it is fitted into the housing:



The till-roll core is not glued in place - yet. This piece needs to be detailed and the central drive-pulley added.

Now I can start to work on the shroud which ducts the air over the top of the cylinder barrels - this will probably start as a piece of blue foam. There's more work to be done on the inlet stacks and intercoolers, so I'll be keeping busy...

Have a good week,

SB

[John18d]

stunning SB simply stunning what you can do with some raw styrene
It's all I can do to build an out of the box kit.
you truly are a designer/manufacturer/builder.
Unbelievable
John

[ianc911]

Magnificent work as usual! Can you enlighten us yanks as to what a till-roll might be? Never can tell when you might use one... ;-)

ianc

[ScratchBuilt]

Hi Ian - 'till-roll' - or to give it it's full technical name: 'credit-card-chip-and-pin-terminal-printer-paper-roll'!! About 2" long, 5/8" diameter, thick-wall plastic tube - and they come in very useful...

John - much appreciated; cheers!

SB