Author Topic: 1/4 scale Porsche 917 180 degree V12 Build  (Read 18124 times)

Offline steamer

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1/4 scale Porsche 917 180 degree V12 Build
« on: September 06, 2021, 09:47:00 PM »
This is the beginning of a new build!   A 1/4 scale Porsche 917  180 degree V12    or Flat 12.

This engine was instrumental in the victories for Porsche at Leman in 1970.    This engine also would go on to dominate in the CANAM series in the early 70's in its turbo form.  However, this build will be of the engine in the Leman endurance racer format as shown below.

Specifics:

Bore:  0.845"  ( 21.5mm)
Stroke:  0.692"  ( 17.6mm)
Displacement:  76.7 CC
Air cooled
Engine block   2 piece split at the crank for a right and left half per the prototype.
SOHC with 2 valves per cylinder with 12 individual heads sharing a common cam box.
Gear driven camshafts as was prototypical, with a timing Vernier at each camshaft
Camshaft:    Individual hardened inlet and exhaust cams pinned to a common shaft driven by a gear as per prototype.
Ball bearing Crank with hardened throws
Plain connecting rod bearings of 6.7mm diameter.
Pressure Lube
Scavenged dry sump
Carbureted  ( Original was fuel injected)
Ignition will be via glow plug for initial running and debug. 
Dual Distributors
Fuel    E85 Gasoline with synthetic oil mix

I'll be following the prototype where ever possible.   The output shaft will be prototypical, and be gear driven off the center of the crank..   The cooling fan and the distributors will be driven from the top counter shaft also driven from the center of the crank.

Features where I will be departing from the prototype

Connecting rods will be 7075 T6 Aluminum, with bronze bearings ( the originals were Titanium with shell bearings)

The crankshaft will be for the sake of durability and reliability be a ball bearing built up crank.    As popularized by Shilling.  The crank throws will be hardened A2 tool steel.

The Oil Pump and Scavenge Pumps:
The oil pump and scavenge pump were driven by a pair of spur gears off the lower output shaft and were mounted directly to the engine block and fed oil to the engine with internal passages.   This is the proper thing to do on an endurance racer.  The best way to avoid a broken oil line is to not have oil lines in the first place!    However, the only way to access these pumps, is to split the case.    For the sake of maintenance simplicity, I've elected to mount the pumps off the front of the engine, directly driven by the output shaft.   This will allow easy removal of the pumps.   
The output of the oil pump will feed 6 nozzles via a cross drilled hole in the left engine block.  These nozzles will be aimed at each connecting rod pair.
Scavenge will be taken from the sump from two sump pickups connected vis cross drilled holes in the right engine block.

Now running some oil in the fuel is a common way to lubricate the bottom end on 4 stroke Model engines.   That would preclude the need for a oil pump and a scavenge pump....but all of that will get sorted out once it's running.

I've made a start with the rotating assemblies.    I'll post up my progress shortly.

Link to the Design Thread.      https://www.modelenginemaker.com/index.php/topic,6259.0.html

Dave

« Last Edit: September 06, 2021, 10:28:01 PM by steamer »
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Online Vixen

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #1 on: September 06, 2021, 10:24:31 PM »
And so another epic build begins. I for one, will be following each and every step. In some ways I feel very close to this one. Maybe it's next on my list.

Dont forget to reference your readers back to the 917 design thread from time to time.

Mike
It is the journey that matters, not the destination

Oh! sod the journey, lets hit the bar and pool instead.

Offline crueby

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #2 on: September 06, 2021, 10:27:06 PM »
Carton of fresh popcorn: check

Comfy chairs for me and shop elves: check

bibs to control drool: check

Ready! :popcornsmall:

Online Vixen

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #3 on: September 06, 2021, 10:32:40 PM »
Did you notice the caption on the second to last photo "porsche-917-racer-could-be-yours-for-a-cool-20-million.jpg ".

Now we can see why Dave is building his own, rather than buying

Mike
« Last Edit: September 06, 2021, 10:40:58 PM by steamer »
It is the journey that matters, not the destination

Oh! sod the journey, lets hit the bar and pool instead.

Offline steamer

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #4 on: September 06, 2021, 10:40:43 PM »
And so another epic build begins. I for one, will be following each and every step. In some ways I feel very close to this one. Maybe it's next on my list.

Dont forget to reference your readers back to the 917 design thread from time to time.

Mike

I can only imagine it's because you and I have been talking about the design of it for 5 years!! :cheers:

Life certainly got in the way of this one....My daughter's cancer....twice!.....the surgical reconstruction of my right quadricep, and a global pandemic!......  There!   that's three!  NO MORE.

 8)

Dave


"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline steamer

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #5 on: September 06, 2021, 10:42:18 PM »
Did you notice the caption on the second to last photo "porsche-917-racer-could-be-yours-for-a-cool-20-million.jpg ".

Now we can see why Dave is building his own, rather than buying

Mike

And it's only affordable because it's only the engine...and it's 25 percent full size!!! :DrinkPint:

oh and one other thing....I pay the guy building it in beer....when he's not doing other things.....
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline steamer

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #6 on: September 06, 2021, 11:03:53 PM »
OK so currently I'm rejiggering the program to cut multiple parts by order of tools

There are 6 or so tool changes per part, if I do one part at a time, and I have 5 more parts that 30 tool changes...but if I cut more than one at a time....it's only 6 tool changes...and I can do something else in between....like crank pins.....

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Johnmcc69

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #7 on: September 06, 2021, 11:26:19 PM »
Woo Hoo! Here comes the chips!
 Glad that everything's coming together Dave, it's going to be a really great build to follow!
 :popcornsmall:
 :cheers:

 John

Offline steamer

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #8 on: September 07, 2021, 12:05:38 AM »
Thanks for coming along John!

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline steamer

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #9 on: September 07, 2021, 12:44:24 AM »
OK   8 tool changes per piece....or 8 total for 3 parts......

Just need to make a new base fixture, I think 3 at a time is a good place to stop...it's a 1.5 hour process for three


Oh and a little eye candy......a print and that print superimposed on the CAD model

« Last Edit: September 07, 2021, 12:59:44 AM by steamer »
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline steamer

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #10 on: September 07, 2021, 01:19:50 AM »
And some more views of the CAD assembly model

"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Don1966

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #11 on: September 07, 2021, 02:35:07 AM »
Ok Dave we are with you and want to see the chips flying …….LOL…..



 :cheers:
Don

Offline petertha

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #12 on: September 07, 2021, 03:09:40 AM »
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?

Offline Art K

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #13 on: September 07, 2021, 03:28:43 AM »
Dave,
This should be a good build I'll be following along, and try to keep up.
Art
"The beautiful thing about learning is that no one can take it away from you" B.B. King

Offline Craig DeShong

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Re: 1/4 scale Porsche 917 180 degree V12 Build
« Reply #14 on: September 07, 2021, 03:32:25 AM »
Hey guys, pass the popcorn, I have a front row seat

 :popcorn: :popcorn:
Craig
The destination motivates us toward excellence, the journey entertains us, and along the way we meet so many interesting people.