Cosworth V8 1:12 scale

[Bob WildParticipant @bobwild67557]

Very impressed!!

[Steve CrowParticipant @stevecrow46066]

I made this gadget (mandrel?) to hold the cylinder heads while I milled it and drilled and counterbored the inclined valve holes.

It is basically a 18mm diameter brass bar with 4mm removed on the flat. The silver steel rod is 8mm so I can hold it in various tool holders and collets.

The idea behind this is that the 16 degree inclined valves converge at a point 5mm below deck height, the bottom of the cylinder head. If I axially centre a cutting tool, I can do all the operations just by rotating 16 degs. either way.

The above photo were taken after I'd used it, hence the square pattern of shallow holes where the drill (intentionally) broke through.

Here it is set up and the flats being milled.

It took me a long time to set this up. I had to clock it axially and make sure it was centred both ends. It seemed like hours with a little rubber hammer tapping things true before I was happy. This was done before I attached the workpiece.

After that it was drilled 1.6mm through, c/bored 2mm for the valve guides and c/bored 2.7mm for the springs.

This worked a treat. My Y-axis remained locked for the whole process.

Steve

[Steve CrowParticipant @stevecrow46066]

I made 3 cylinder heads, a left, a right and a universal.

The universal is going to be used as a test-bed for cutting the valve seats and a couple of other things. After that it will go back on the mandrel and will be a sacrificial holder for the cam carrier blanks when it comes to machining them.

There are 48 inclined holes here, that's 144 separate operations.

Here is the under side of the heads. The central holes were drilled at the same time as the holding down bolt holes.

Here is a close up. The web between the two valve holes is 0.1mm thick which I was a bit worried about as even the slightest variation from this between cylinders would be visible but everything came out alright.

A close up of the underside. The central hole is not for a miniature spark plug but a guide for the tool I'm going to make for cutting a recess.

All in all, I'm quite pleased with these. I can't find any errors so all the careful clocking and indexing paid off. Saying that, I'm glad it's over. It took me a whole day of dial-counting and double checking before drilling.

Steve

[Steve CrowParticipant @stevecrow46066]

Hello, I haven't updated this thread for a while so here we go.

I have been cutting the gears for the cam gear train, and lots of spares.

There are 11 gears in the train in 4 different sizes.

 

They all came out ok apart from the 20 tooth wheels which I didn't give enough depth of cut. Only a couple of thou but it's made a difference at Mod 0.3. This is unfortunate as 7 of the 11 gears are 20 tooth! I'm just going to have another go.

To hold the wheels for facing, drilling etc. I made pot chucks for each size.

These just screw into a 8mm collet thingy.

They give a nice friction grip that doesn't do any damage. You don't need glue or shellac.

I made a spare of course.

I centre drilled one of each size as "test" gears. I'll fix an arbor to each and put them in my depthing tool and see how they mesh.

More soon.

 

Steve

 

Edited By Steve Crow on 07/02/2021 18:04:56

Edited By Steve Crow on 07/02/2021 18:05:53

[Roger BestParticipant @rogerbest89007]

well done, too fiddly for me!

[SteviegtrParticipant @steviegtr]

Nice work Steve. Keep it up.

Steve.

[Hubert ImrightParticipant @hubertimright59493]

Excellent

[Ron LadenParticipant @ronladen17547]

Very impressive I admire your patience and ingenuity in making those tiny parts, great stuff.

Ron

[Steve CrowParticipant @stevecrow46066]

These are the cam carriers. I think that's the term. If someone has a better name for them, let me know.

They are about 80% finished. I just need to cut a groove for the cam bushes and drill and tap a few holes for end plates.

Made from 1/4 x 3/4 mild steel bar. Quite tricky milling operation with all the angles.

A total of 48 M1.2 holes to tap – I have done around half.

Steve

[Steve CrowParticipant @stevecrow46066]

Cam carriers and cylinder heads.

Steve

Edited By Steve Crow on 08/02/2021 10:12:38

[Ady1Participant @ady1]

Amazing workmanship

My eyes would explode after an hour of effort at that scale

[Steve CrowParticipant @stevecrow46066]

I made a start on the camshafts. First of all I turned the blanks and a couple of spares from 1/8" silver steel.

 

The brass gadget on the end is to support and provide a female centre for the shaft and also, when I move it in the collet chuck when milling, I can use the flat part for indexing and make sure all the lobes are of correct orientation.

 

Here they are sat on the cam carriers.

 

Here they are with the lobes milled.

 

Each lobe has 36 facets which I will have to file and polish out.

 

This is the cam profile I've tried to achieve. There is no science behind me using this shape – it's just easy to draw and "looks right".

 

It was difficult to get a photo of the profile but you can get a good idea from this one.

More soon,

Steve

Edited By Steve Crow on 01/03/2021 13:22:58

Edited By Steve Crow on 01/03/2021 13:33:13

[Steve CrowParticipant @stevecrow46066]

I made some temporary arbors for the cam train gears and checked them with a depthing tool.

They meshed very nice and smoothly and the centre distance seemed bang-on as well.

But, they just didn't look right in brass, it made everything look a bit "clockwork", so I remade them all in steel.

Here are the steel test gears with temporary arbors and a brass one for comparison.

Steve

[Steve CrowParticipant @stevecrow46066]

Hello,

I haven't updated this in ages so here are a few images of where I am with the engine and gearbox.

I still have the pistons, valve springs and and a few minor things to make for the engine.

For the gearbox, I have to make the forward/reverse gears. I also need to design a clutch that will fit in here-

The crossed-out side plates on the gearbox are tempory. I wanted to be able to see the diff but I've cut a "viewing window" in the top of the gearbox instead. The plates will be replaced with scale looking ones.

There is till a lot of work in finishing and polishing not to mention blueing about 130 screws.

More pictures soon.

Steve

[Dave SParticipant @daves59043]

Awesome work.
Any chance of a photo with a rule in it so we can get a true sense of the small scale?

Dave

[Steve CrowParticipant @stevecrow46066]

Any chance of a photo with a rule in it so we can get a true sense of the small scale?

Dave

I usually put something in my photos for scale – I forgot this time.

To give you an idea, the total length of the assembled engine and gearbox is 85mm, 5mm longer than a cigarette.

Next time I take some photos, I'll include a coin or something.

Steve

[Ady1Participant @ady1]

Looks great, a work of art

[Nigel Graham 2Participant @nigelgraham2]

A fine challenge and beautiful work!

[Steve CrowParticipant @stevecrow46066]

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

[David George 1Participant @davidgeorge1]

Amazing work! Keep up the info on here please. I wish I had the time patience and skill that you have.

David

[SteviegtrParticipant @steviegtr]

That is looking stunning Steve. As above keep posting pics.

Steve.

[Steve CrowParticipant @stevecrow46066]

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

[Die HardenedbedwayParticipant @diehardenedbedway41166]

So cool !! I wouldnt know where to start !

[Ramon WilsonParticipant @ramonwilson3]

Superb workmanship and excellent documentation – thanks for sharing it

Tug

[Engine Doctor ( Phil )Participant @enginedoctorphil]

Absolutely BRILLIANT . Well done .

[Author]

Posts