1/4 scale Porsche 917 180 degree V12 Build

[steamer]

Here we go!
Maybe you spoke to this is the design workup but what materials were used in FS engine for the various (I'll loosely call them composite / molded thermoplastic) components. They all have different color amber shades, perhaps heat aging affecting them differently? Or maybe Kevlar used back then? The fan shroud has a hint of fabric so presume its a composite layup vs molded? Will you similarly miniaturize these?

Honestly....I haven't gotten that far yet....I have looked at those parts and honestly I think they are Kevlar/polyester resin layups.    I think I will probably 3D print some of these parts...

Dave

[Vixen]

Here we go!
Maybe you spoke to this is the design workup but what materials were used in FS engine for the various (I'll loosely call them composite / molded thermoplastic) components. They all have different color amber shades, perhaps heat aging affecting them differently? Or maybe Kevlar used back then? The fan shroud has a hint of fabric so presume its a composite layup vs molded? Will you similarly miniaturize these?

Honestly....I haven't gotten that far yet....I have looked at those parts and honestly I think they are Kevlar/polyester resin layups.    I think I will probably 3D print some of these parts...

Dave

Hi Dave and perertha,

I think you will find that the fan, the shroud and the injection trumpet decks were dough moulded using the DMC process, rather than a layup. DMC (Dough Moulding Compound) was a popular material for aerospace products in the 1970's 1980's. The DMC is an uncured dough-like thermoset compound, made up from either epoxy or polyester resins with a high proportion of chopped E glass fibre and other fillers.

The DMC process requires expensive heated metal moulds and some form of a mechanical or hydraulic press to close the mould. Similar in some ways to die casting moulds.

A measured amount of uncured dough moulding compound is rolled flat and placed into the heated female mould. The heated male side of the mould is closed, under pressure, forcing the dough molding compound into the mould cavities. Heat from the mould initially softens the dough molding compound so that it flows into every part of the mould very accurately. The heat then cures the compound.

The resulting material is both strong and light with the characteristic translucent amber colouring, you see on the 917 engine. The fibres are usually visible within the resin. The amber coulour seems to darken and become more opaque with age.

Sounds like a 3D print is the way to go. It would be nice to find a translucent amber printing filament to complete the illusion

Mike

[steamer]

Here we go!
Maybe you spoke to this is the design workup but what materials were used in FS engine for the various (I'll loosely call them composite / molded thermoplastic) components. They all have different color amber shades, perhaps heat aging affecting them differently? Or maybe Kevlar used back then? The fan shroud has a hint of fabric so presume its a composite layup vs molded? Will you similarly miniaturize these?

Honestly....I haven't gotten that far yet....I have looked at those parts and honestly I think they are Kevlar/polyester resin layups.    I think I will probably 3D print some of these parts...

Dave

Hi Dave and perertha,

I think you will find that the fan, the shroud and the injection trumpet decks were dough moulded using the DMC process, rather than a layup. DMC (Dough Moulding Compound) was a popular material for aerospace products in the 1970's 1980's. The DMC is an uncured dough-like thermoset compound, made up from either epoxy or polyester resins with a high proportion of chopped E glass fibre and other fillers.

The DMC process requires expensive heated metal moulds and some form of a mechanical or hydraulic press to close the mould. Similar in some ways to die casting moulds.

A measured amount of uncured dough moulding compound is rolled flat and placed into the heated female mould. The heated male side of the mould is closed, under pressure, forcing the dough molding compound into the mould cavities. Heat from the mould initially softens the dough molding compound so that it flows into every part of the mould very accurately. The heat then cures the compound.

The resulting material is both strong and light with the characteristic translucent amber colouring, you see on the 917 engine. The fibres are usually visible within the resin. The amber coulour seems to darken and become more opaque with age.

Sounds like a 3D print is the way to go. It would be nice to find a translucent amber printing filament to complete the illusion

Mike

Thanks for that Mike....this pesky work thing slows down my response!....That's an interesting note on the DMC process that I did not know about.   As far as 3D printing, I'm certainly at the right place to find a substitute material to replicate that.    I have a few materials in mind that I could use, but I'm also aware that not everyone has access  to those materials, so I may come up with something more readily available......I think I have some time to think that one over.

Dave

[Art K]

Mike,
Thanks for the info about DMC. It's above my pay grade I'm sure.
Art

[Vixen]

DMC moulding fell out of favor when carbon fibre pre-preg became widely available.

Mike

[steamer]

Ok...I got some time in the shop finally   More crank disk "B"s and I cut the crank pins.    The  pins need to be drilled and finished to length

When I inspected my first crank disk, I found it was out of spec, so I'll need to crank out 1 more tomorrow.

progress!!
 

[Vixen]

More nice bits

Even with the best CNC machines, there can be slight tolerance differences between otherwise identical components. For critical components, like this built-up crankshaft, it can pay to make an additional one or two. You can then chose the very best, the cream of the cream,  for the final assembly.

Mike

[ozzie46]

Ok...I got some time in the shop finally   More crank disk "B"s and I cut the crank pins.    The  pins need to be drilled and finished to length

When I inspected my first crank disk, I found it was out of spec, so I'll need to crank out 1 more tomorrow.

progress!!
 

Just don't get cranky about it.

Ron

[steamer]

Yup  made 8   need 6    I have another blank and it's still set up..

Dave

[Vixen]

Yup  made 8   need 6    I have another blank and it's still set up..

Dave

Need 6?? I guess that's 6 side A and 6 more side B

Mike

[steamer]

There are 4 B sections   and 2 A sections

Each A and B section has a finished side and a unfinished side  ( bearing diameter)

One side is finished in that the ball bearing diameter and mounting face are machined complete prior to assembly


The other unfinished side has the ball bearing diameter and face machined AFTER the section has been assembled to the crank pin  to guarantee concentricity

It's How Shilling did it actually.

The area in blue is finish machined after the 3 parts are put together either with loctite or just the press fit

Dave

[Roger B]

Glad to see you underway with this one  I will be following along 

[Kim]

I'm following along, Dave, but I don't have much to add.

Other than to say, "that is one complex crankshaft!  Wow!"   

Kim

[steamer]

Well....it's no Briggs and Stratton!.....I started with what I think is the most difficult part of this build.   The Crankshaft.    As the power from this engine is taken from the center by way of a big gear, and a 8 main ball bearing crankshaft.....it's a doozy!...I figured if i could build this....I can build it!

I'm putting together a post from today's effort....

[steamer]

Made more cranks today, and all the crankpins.  The Crankpins are A2 tool steel.   The will be hardened.   The crank webs are 1144SP.     To test the press fit I made up a extra pin and cheek and pressed them together  ( .002" press fit") using some never seize as a lubricant.   It worked perfectly!   So I'll just keep going this week and see how many I can get done.   I need to order some more 1144SP to finish off the parts for the crank, including the central gear.  #2 and #4 32 DP cutters and a arbor.....lots of tool making this week I think.    I'm having fun with it thou.      I was able to save that oversize crankweb, so I have my 4 and they all meet spec.

Progress!