Cosworth V8 1:12 scale

[Art K]

Steve,
It looks like you've been up to some very intricate work, twice. Looks very good.
Art

[steamer]

That's coming along beautifully Steve!!!

Dave

[Steve Crow]

One of the most fiddly things on this build was hand fettling the bearing blocks so the camshaft turns freely with a minimum of play.



The cam shafts are supported by a sort of shell bearing. These were made by turning down brass bar to 2mm and boring out to 1.6mm.

These were then trimmed down to a semi circular C-section and burnished/work-hardened into place using a polished steel 1.6mm rod.

They are now held firmly in place by there own springiness.



I'm making all this up as I go along but it seems to be working fine.

Steve

[crueby]

Quite impressive!!

[Steve Crow]

My next challenge is to finish the cam gear train. The principal gears are in place and running smoothly, I just need to sort out the idler gears.



Here are some sat in their final position.



Steve

[Admiral_dk]

Very nice progress 

You are not doing things the easy way ...!

Since you have very small tollerances on the placement of these gears - are you placing the axels on excentrics so you can adjust them ?

[Steve Crow]

It's time I resurrected this thread. I've had a couple of months off metalwork but I'm back into it now.

Yesterday, two years to the day from the first idea and drawing, I finally finished making all the major components.

I've completed the task I dreaded most. The valves, guides, tappets and springs - 32 of each.

The valves took the most time as they are rather small with quite tight tolerances. Each one needs 8 machining processes.



Here's 16 of them on a penny.



And a close up of one so you can see the slot.



At this magnification, you can see bits of paste from when I ground them into their seats.

[Steve Crow]

Here's how the valve parts fit together, open and closed.



The valve guides are brass and reamed with a 1.026mm carbide reamer (Jurassic Tools - great price). They are a friction fit in the cylinder head and the springs keep them seated.

The tappets are adjustable using the 3 holes and the slot in the valve using a tool that I have not finished yet.

Here is a tappet and an untrimmed spring. And a penny.



Steve

[A7er]

A great piece of work! I haven't read through the whole process to see if you have already covered this question, but why 1/12th scale?

[Steve Crow]

A great piece of work! I haven't read through the whole process to see if you have already covered this question, but why 1/12th scale?

It's the smallest I could get away with! Also, it's easy to scale from the imperial measurements of the original. The block fits nicely into a 1 inch square bar, look at my earliest pictures.

[Steve Crow]

Here is one cylinder head with valve gear installed and a cam carrier behind it.



Valves, tappets and springs (and spares) for the other head.

[Admiral_dk]

Very impressive work and scale 

I can't remember, but you are getting close to first run, aren't you ?

Per