917 180 degree V 12

[steamer]

OK Mike.....Those spiral worm gear drives for the distributor.    Do you recommend  the "Westbury" trick to cut them?  or do you have another trick up your sleeve?


never mind.......like this
http://modelenginenews.org/index.html




Dave

[steamer]

I think I sorted the oil plumbing tonight.....a bit of clever, and deep!   gun drilled holes in the case..

The model should be FUN!

Dave

[Vixen]

Unfortunately I do not have much experience in making spiral worm gears and non at all with "Mr Westbury's" tricks.

Did you post the correct link? I was taken to the farewell post from our dear departed friend Ron. Such grace and dignity knowing everything would end in just a few short, painful weeks.

RIP Ron, your memory lives on.

Mike

[steamer]

Hi Mike,

Yes, I always loved his editorials!     The page I hoped I was linking, but apparently failed to ...is on that page

Look under Engines

Then Projects

Then look under the "Feeney" project, and he explains a very simple means of cutting these gears.   It was actually published in Home Shop Machinist, and I remember the article.

Dave

[Vixen]

Dave
I know we have both been looking at the oil system plumbing for the Porsche 917 engine. The oil system is well integrated into the bowls of the engine and not that easy to understand, given the limited drawings available to us. There are many photos on Google but usually of the different parts of the engine to that you wish to study. It will take some engineering detective work and plenty of discussion to work things out. It would be a great help if one of the forum members had a Porsche 917 sitting in the garage, but perhaps that is too much to wish for.

In a high performance racing engine the oil system performs two major tasks. The lubrication of the bearings is obvious, the use of the oil to remove heat and cool the engine may not be so obvious. The oil system plays a major role in the cooling of an air cooled engine, more so than in a liquid cooled engine. Most high performance race engines do not have an oil sump (oil pan), instead a so called a dry sump system is used. The engine's hot, used oil is sucked out of the bottom of the engine by large scavenge pumps and pumped through large oil coolers into a header tank. The cooled and de-aerated oil returns to the engines pressure pump for re-circulation.

Three large volume pumps can be seen in the cross section drawing. One pressure pump and two scavenge pumps. The pump block is sandwiched between the two halves of the crankcase. Oil passages have been gun bored (drilled) into the crankcase casting walls, the bumps associated with these oil passages can be seen in the photos shown in reply #  53. All three pumps, pump from right to left.

If you look at the cross section drawing in the first post, you can see there are four circular oil passages (drillings) in the crankcase. Three on the left half and one on the right. The oil passage in the bottom right corner connects the oil suction strainers to the inlet side of the scavenge pumps. The hot oil from the scavenge pumps exits via the lower left oil passage on the left side of the crankcase. The high pressure oil from the pressure pump connects to the middle left drilling. There is another vertically drilled passage (can be seen on several of the Porsche museum exploded engine display photos) which connects the lower left oil passage to the the full length oil passage at the top left hand corner on the crankcase. The high pressure oil is distributed down smaller drillings to each of the eight main bearing journals. More small drillings in the crankshaft distribute the oil to the big end bearings. All quite conventional but needs to be fully understood to design the model engine.

The oil feed to the four camshafts is not so easy to trace. There are no drawing and the available photos never seem to show the detail we are looking for. There is an interesting series of engine part photos on the https://www.classicdriver.com/en/car/porsche/917/1970/171074 website. One shows the cambox lower shelf, without the camshaft in place. There appear to be no oil passage drillings into the camshaft bearing journals. I have therefore assume that the camshaft lube oil passes down a drilling in the centre of the hollow camshaft instead of through oil passages in the cambox tray. I am not absolutely certain how the high pressure lube oil reaches the four camshafts, but there appears to be an oil way drilled in both of the camshaft drive gear cluster housings, between the crankcase oil passage and the camboxes.

Waste oil from the four cam boxes is scavenged by another two oil pumps driven off the ends of the lower camshafts. The camshaft scavenge oil is returned to the front of the engine via the two external pipes.

Well that's how I interpret the limited information available. Dave may have reached different or similar conclusions, Either way, by this sort of engineering detective work, we slowly begin to understand what made the Porsche 917 so remarkable.

Mike

[steamer]

Hey Mike,

I believe the pumps work just as you say.   What I saw last night is ....I think.....they come out of the pump and both feeds make a 90 degree turn to the front of the engine.  Through two separate gun drilled holes.     One from the scanvenge pumps goes back to tank as you have mentioned.   I believe the pressure side turns vertical at the front of the engine and goes to an oil filter at the top front of the engine.   From there, it flows back along the top of the engine towards the back of the engine.     From there I think it feeds the mains as you say.   and there appears to be a cross over between the cases that feeds passages in the cam gear box assemblies.    If you look you will see two hollow location pins on the gear cases, and an oil passage down the side...it is often plugged with a plastic plug cap in the photo's     You can also see the cross over port from the left case to the right case for the camshafts just behind the bore for the cooling fan shaft, just below the stud in the casing.

OK  so we've gotten as far as the top of the of the cam shaft gear boxes, both sides..... 

What I see....and perhaps I'm not seeing it correctly so I'll call it surmise....

There are two gun drilled passages either side of the cam shafts on the cam box, connected to the one feed port coming from the cam shaft gear boxes.

They are connected via two cross drilled ports.    This feeds all the camshaft bearings from below.     I also believe we see oil nozzles that feed oil to the cam/tappet pockets...this would cool and lubricate this part of the engine nicely....

See if you can see what I see....if you like..      I need to go make a living.....but I'll be back later...

Having great fun!

Dave

[steamer]

Mike...the pictures I was looking at were of the engine in the Porsche museum....the "Exploded view" engine

https://www.classicdriver.com/en/car/porsche/917/1970/171074
The reference you gave...doesn't show oil feed holes to the cam shaft bearings, but I did see them in the other engine.

A design change perhaps?

Dave

[b.lindsey]

Hmmmm...twelve pages and not one chip yet. You have been around Zee to long Dave 

Bill

[steamer]

Hmmmm...twelve pages and not one chip yet. You have been around Zee to long Dave 

Bill

This would be called the Engineering phase of the project.    Personally, I think it's a great tool for the design of a model.   How did the real one work, and how do you figure it out?  How do you go about designing a model...and documenting the design so that you can go in the shop and make it....

Additionally, I'm enjoying myself...and I think Mike is as well.....

Dave

[steamer]

Mike...

I blew up the photo from your reference....and took a snap shot and annotated it.

I think it does have oil holes, it's that the picture is low resolution...but I think I can make them out.....here's my retouched photo with a sketch on it.

I've circled what I think are the oil holes.....they appear at least consistent.

Dave

[b.lindsey]

I am just messing with you Dave. For a project this complex you are absolutely right

Bill

[steamer]

Thanks  Bill!   

Dave

[Vixen]

Dave,
That's the big problem with this sort of detective work. Which piece of information is correct, which can you trust when you only have Google to find stuff. There were many different versions produced by the factory and the available documentation does not record version number or modification state. Similarly, many engines are in private hands and we have no idea what extra modifications were added by the new owners.

The best we can hope to achieve is an understanding of the approach taken by the designer and from this devise something similar which can be made to work for our model engines. We can work to produce a fine look alike engine from the limited information available but you would need access to a full set of works drawings to produce an exact replica.

[steamer]

Dave,
That's the big problem with this sort of detective work. Which piece of information is correct, which can you trust when you only have Google to find stuff. There were many different versions produced by the factory and the available documentation does not record version number or modification state. Similarly, many engines are in private hands and we have no idea what extra modifications were added by the new owners.

The best we can hope to achieve is an understanding of the approach taken by the designer and from this devise something similar which can be made to work for our model engines. We can work to produce a fine look alike engine from the limited information available but you would need access to a full set of works drawings to produce an exact replica.

1000% correct on all accounts!    We progress......

Dave

[steamer]

Here's the engine build from another site....same part.    showing oil ports...