Porsche 917 flat 12 engine

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ddmckee54

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My mistake, I didn't look at the drawings close enough.

I saw one threaded hole and at first glance it looked like the other hole was threaded too. Now that I go back and take a closer look at the drawings I can see that one hole in each cam section is threaded and the other hole is for the pin.

Don
 

ajoeiam

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I only did a little bit of searching and couldn't find any such - - - - wondering - - - have you described how you're cutting all this gears?
(Just curious about how you're succeeding at this - - - great looking stuff!!)
 

Foketry

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I only did a little bit of searching and couldn't find any such - - - - wondering - - - have you described how you're cutting all this gears?
(Just curious about how you're succeeding at this - - - great looking stuff!!)
Are commercial gears, available at any bearing shop. Module 1, 32 teeth
Involute gear cutters is much more expensive than commercial gears, some different sets would be needed depending on the number of teeth.
 

ajoeiam

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Are commercial gears, available at any bearing shop. Module 1, 32 teeth
Involute gear cutters is much more expensive than commercial gears, some different sets would be needed depending on the number of teeth.
That was what I was wondering - - - sorta hoping that you had cut them - - - - would love to follow such!!
 

Foketry

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Valve tappets , qty 24
Are made of bronze and kept in axis by an external steel bushing.
The ratio between tappet diameter and bushing length is greater than 1.5 to ensure linear sliding without jamming , everything will be lubricated with good quality permanent grease.
Steel bushings are fixed with Loctite 620
After the final assembly it will be necessary to find the right thickness of the tappet of each valve with respect to the base of the cam , valve clearance must be between 0.05 mm and 0.1 mm
Now I have made tappets increased by 0.5 mm then the internal part will be turned up to the correct thickness.

testa e valvole 2.jpg


Simulazione camma punteria.jpg

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IMG_2074.JPEG
IMG_2077.JPEG
 

a41capt

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Terry,

The camhead version of the BMW R1200 models (as well as several other motorcycle manufacturers) utilize a tappet “bucket” of different thicknesses to adjust valve clearance. These fit inside the tappet and over the head of the valve stem and allow for wear to the tappet face as well as valve seat wear.

Perhaps this type of system would allow you to fine tune each valve as the engine wears in without having to make all new tappets later?

Thanks again for the detailed build thread. I’m loving the hell out of your work and looking forward to hearing the snarl of a horizontally opposed, air cooled 12!

John W
 

Foketry

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Terry,

The camhead version of the BMW R1200 models (as well as several other motorcycle manufacturers) utilize a tappet “bucket” of different thicknesses to adjust valve clearance. These fit inside the tappet and over the head of the valve stem and allow for wear to the tappet face as well as valve seat wear.

Perhaps this type of system would allow you to fine tune each valve as the engine wears in without having to make all new tappets later?

Thanks again for the detailed build thread. I’m loving the hell out of your work and looking forward to hearing the snarl of a horizontally opposed, air cooled 12!

John W
In general, all engines with overhead camshafts have shims under the tappets, in my case since this engine will work a few hours in its life and therefore will not need to be adjusted due to wear, I prefer to lower the thickness by turning, one by one , do shims means have at least 24 pieces in addition, a further complication...

I also hope to hear this engine roar :p, thanks for the encouragement
 

a41capt

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In general, all engines with overhead camshafts have shims under the tappets, in my case since this engine will work a few hours in its life and therefore will not need to be adjusted due to wear, I prefer to lower the thickness by turning, one by one , do shims means have at least 24 pieces in addition, a further complication...

I also hope to hear this engine roar :p, thanks for the encouragement
Understood! But I am a bit disappointed that you’re not building it to fit a scale 917 to fit it and shrinking yourself to drive it!!! :p

John W
 

Peter Twissell

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I've probably missed it on the pictures, do you have a means to vent the volume under the tappet, so it can't become hydraulically locked with oil?
 

Foketry

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Bearing caps for camshafts
As the original Porsche engine I made 8 supports for each camshaft, the camshaft slides directly into the hardened and lubricated aluminum seats.
My poor technology does not allow me to harden the aluminum, so I put 8 small bearings on each camshaft
Each bearing will have its own cap, total 32 caps
cavallotto albero camme.jpg
 

Foketry

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To avoid complex machining I made 5 aluminum castings, each with 7 joined pieces, I made patterns with 3D printer

cavallotto albero camme fusione.jpg


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the shape patterns on sand, the shapes below are for other pieces to make a modification in my CNC milling machine

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The furnace with molten aluminum

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a41capt

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Well, I REALLY need to become educated in 3D CAD. What a tool, and I guess I’ll have to sit down at my desk and take the plunge. I experimented with a student version of SolidWorks several years ago and was making headway when I just went back to paper. SolidWorks has a program for Veterans, so I guess I’ll bite the bullet and get back to it. The downside? Next will be CNC/CAM… one more hobby expenditure! ;)
Thanks for taking us along for this ride,
John W
 

Foketry

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The casting caps

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first machining, 3 mm hole and counterbore

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second machining, roughing of the bearing seat and face milling
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third machining, separation of the caps with 4 mm end mill , the caps are locked with a jig
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Foketry

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Milling of bearing seats and the surface for cover on the camshaft housing
the planes to be milled are inclined, I built a simple equipment to clamp the camshaft housing in the correct position , at the right angle
Note the holes closed with brass screws, I corrected an error

IMG_2116.JPEG
 
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