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Cosworth V8 1:12 scale

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Steve Crow01/11/2020 14:46:01
275 forum posts
156 photos

A few months ago, I decided to have a go at making a 1:12 scale Cosworth V8 DFV Formula 1 engine.

It will be a 2-stroke running on air (or CO2?) with a bore of 7.2mm and a stroke of 5mm.

I want to share my progress so far as I’m sure I will need some advice.

After making the drawings, the first thing I did was make card models of the main components.

pre_01.jpg

 

This helps me visualise things and see if any screws interfere with each other etc.

card_04.jpg

 

The block started life as 1” square mild steel bar.

pre_02.jpg

 

I sawed of a piece about 3” long and this was clocked in the 4 jaw and eccentric bosses, on the crank centre line, were turned at both ends. This gave me an accurate way of holding it while boring out the cylinders and milling the block to shape. In the picture below, the milling is part done.

pre_04.jpg

 

The block, milled to shape. The bores are a bit rough but true. They will have brass liners anyway.

raw_block_04.jpg

 

The block was drilled and tapped and the sump blank bolted to it.

raw_block_02.jpg

 

The whole assembly was then drilled and bored out as one piece and the bosses removed.

block_sump_01.jpg

 

More to follow….

Steve

Edited By Steve Crow on 01/11/2020 14:47:22

Edited By Steve Crow on 01/11/2020 14:48:04

Edited By Steve Crow on 01/11/2020 14:52:27

Brian H01/11/2020 15:13:00
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2097 forum posts
113 photos

Super! Look forward to seeing more.

Brian

Steve Crow01/11/2020 15:29:55
275 forum posts
156 photos

The next job was to remove some metal from the inside of the sump and the block to provide clearance for the con rods.

Here is the block, ready to be milled. Note the miniature brass V-blocks – very handy things. You can see they are numbered. This is to ensure repeatability when using them with a 4-jaw.

block_02.jpg

And here they are completed. The block now weighs 60g. The initial square blank weighed 370g. That might not sound a lot of swarf to you guys with big-boy’s lathes, but it made a mess of the kitchen table with my Sherline.

block_sump_03.jpg

More soon.

Steve Crow01/11/2020 15:48:00
275 forum posts
156 photos

I made some endplates from 1/8” mild steel flat bar. These hold flanged bearings for the crankshaft, 4mm at the gearbox end and 3mm at the cam-drive end. There is raised boss on the back of both which are a snug fit into the crankshaft bore to keep thing nice and true.

end_plates_04.jpg

The one on the left will house the flywheel and the one on the right, the cam gear train.

end_plates_05.jpg

The sump and block were drilled and tapped 12BA to secure the endplates and everything was assembled.

end_plates_03.jpg

end_plates_02.jpg

assembly_01.jpg

Steve

Steve Crow01/11/2020 16:03:55
275 forum posts
156 photos

I then fly-cut some steel to size for the cylinder head blanks and drilled and counterbored to suit the block. All in all, I had to tap 30 blind holes to M1.6 in the block. A bit scary.

assembly_03.jpg

I also cut to size blanks for the cam carriers. They can just be seen in the background.

card_02.jpg

Another shot.

card_03.jpg

Steve

Nicholas Wheeler 101/11/2020 16:21:54
566 forum posts
31 photos

When I read you started with 1" square bar, I thought you were crazy.

I've just pulled a bit out of my stash, and now I know you're crazysmiley

It already looks cool. Are you going to fold a monocoque out of foil to mount it in??

Steve Crow01/11/2020 16:22:12
275 forum posts
156 photos

The flat-plane crank is assembled from EN1A webs and 3mm silver steel journals.

crank_02.jpg

 

The assembly was a tight friction fit then drilled, countersunk, pinned and riveted. 1mm mild steel pins were peened into the countersink then filed and polished over to render invisible.

crank_03.jpg

 

The unwanted journals were then sawn out and the gaps between webs cleaned up on the mill.

crank_01.jpg

This still needs a bit of cosmetic fettling.

Steve

Edited By Steve Crow on 01/11/2020 16:23:37

Edited By Steve Crow on 01/11/2020 16:34:11

Steve Crow01/11/2020 16:27:11
275 forum posts
156 photos

Here is some of the crank in situ.

crank_04.jpg

crank_05.jpg

crank_06.jpg

crank_07.jpg

Steve

Steve Crow01/11/2020 16:33:20
275 forum posts
156 photos
Posted by Nicholas Wheeler 1 on 01/11/2020 16:21:54:

When I read you started with 1" square bar, I thought you were crazy.

I've just pulled a bit out of my stash, and now I know you're crazysmiley

It already looks cool. Are you going to fold a monocoque out of foil to mount it in??

I've actually thought about making a 1:12 English wheel to form beer can aluminium for said monocoque.

Has anyone heard of this being done before?

Dave Halford01/11/2020 20:58:29
1388 forum posts
12 photos

You're 3 main bearings short laugh

Steve Crow01/11/2020 23:02:00
275 forum posts
156 photos
Posted by Dave Halford on 01/11/2020 20:58:29:

You're 3 main bearings short laugh

I know. I considered a central one but life's too short.

Graham Stoppani02/11/2020 06:28:18
avatar
95 forum posts
18 photos

When I was a young lad working in a local motorcycle shop I took a phone call from a gentleman who wanted us to collect his son's field bike to sort out the non-running engine. Being an 'expert' I asked if he had checked if the petrol was turned on and if there was a spark - turned out I was talking to Keith Duckworth... Doh!

embarrassed

Steve Crow02/11/2020 19:46:56
275 forum posts
156 photos

Here is a drawing of a cross-section through the cylinders. It is sort of colour coded. Grey is EN3B, light blue EN1A, dark blue are screws and silver steel and orange or brown are brass except for the exhaust headers which are copper tube.

 

section_a_02_print_01.jpg

 

The air is fed from the two brass vessels (plenums?) in the vee.

This a hypothetical cross-section as there are 4 valves per cylinder and the banks are staggered.

Edited By Steve Crow on 02/11/2020 19:48:28

Steve Crow03/11/2020 17:53:20
275 forum posts
156 photos

Here is another cross-section, this time between the cylinders.

section_b_02_print_01.jpg

When designing this, I had a bit of a headache making sure the screws didn't clash with anything or each other. The problem is, even using the smallest economically available, the screws are grossly over scale.

I'm using M1.6 allen screws with the head turned down to 2.35mm to hold the sump, block, heads and cam carriers together.

12 BA cheesehead screws with the head turned down to 1.95mm for the con rods, exhaust and inlet manifolds and also the cam covers.

I will use either M1.0 or 14 BA cheesehead to secure the cam shaft. I want to find a good quality supply of steel screws first(non-stainless, I'll be blueing them). When I find them, I'll buy the appropriate taps. If anyone has any advice on this, I would be grateful.

Steve

Mike Poole03/11/2020 19:26:42
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Moderator
2936 forum posts
70 photos

“It will be a 2-stroke running on air (or CO2?) with a bore of 7.2mm and a stroke of 5mm.”

Was this a typo Steve? or am I missing something.

Mike

Steve Crow03/11/2020 22:43:37
275 forum posts
156 photos
Posted by Mike Poole on 03/11/2020 19:26:42:

“It will be a 2-stroke running on air (or CO2?) with a bore of 7.2mm and a stroke of 5mm.”

Was this a typo Steve? or am I missing something.

Mike

No typo. By 2 stroke, I meant a simple expansion engine with 2 cycles, in and out.

I suspect I am not using the right terminology.

DiogenesII04/11/2020 08:12:46
213 forum posts
108 photos
Posted by Steve Crow on 03/11/2020 17:53:20:

...I will use either M1.0 or 14 BA cheesehead to secure the cam shaft. I want to find a good quality supply of steel screws first(non-stainless, I'll be blueing them). When I find them, I'll buy the appropriate taps. If anyone has any advice on this, I would be grateful...

Steve

EKP SUPPLIES and BA-BOLTS are two suppliers that list plain steel cheesehead down to 14BA.. ..others might too, those just sprang to mind..

I have and do use EKP, satisfactory fit & finish on the larger BA stuff I've had - I've seen BA-B recommended before, so probably fine as well.. ..there may be others..

Mike Poole04/11/2020 08:30:44
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Moderator
2936 forum posts
70 photos
Posted by Steve Crow on 03/11/2020 22:43:37:
Posted by Mike Poole on 03/11/2020 19:26:42:

“It will be a 2-stroke running on air (or CO2?) with a bore of 7.2mm and a stroke of 5mm.”

Was this a typo Steve? or am I missing something.

Mike

No typo. By 2 stroke, I meant a simple expansion engine with 2 cycles, in and out.

I suspect I am not using the right terminology.

I have read your description again and realise what you said, I was locked into internal combustion think. It’s looking great so far, it will be nice to see it running when finished.

Mike

Steve Crow04/11/2020 18:27:40
275 forum posts
156 photos

EKP SUPPLIES and BA-BOLTS are two suppliers that list plain steel cheesehead down to 14BA.. ..others might too, those just sprang to mind..

I have and do use EKP, satisfactory fit & finish on the larger BA stuff I've had - I've seen BA-B recommended before, so probably fine as well.. ..there may be others..

Thank you, I've just checked them out. It seems that 14BA screws are more easily available than M1 so I'll probably go for that. A finer thread too - M1 is pretty coarse at 0.25 pitch. I can single point thread down too 0.25 pitch on my Sherline lathe but I need at least 60 screws!

14 BA taps are quite pricy though. I might have to redesign a few bits so there are no blind holes, then I can get away with a single taper tap.

All the ones I've seen seem to be around the same price, £15 each so I suspect they are all the same manufacturer. There can't be too many companies making 14 BA taps! Has anybody got any recommendations?

Cheers,

Steve

David George 104/11/2020 20:12:46
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1521 forum posts
472 photos

Try Tracy Tools they may sponsor you for a couple of taps. If you don't ask you don't get.

David

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