Author Topic: Cosworth V8 1:12 scale  (Read 2444 times)

Offline Steve Crow

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Re: Cosworth V8 1:12 scale
« Reply #15 on: November 24, 2020, 11:36:47 AM »
The flat-plane crank is assembled from EN1A webs and 3mm silver steel journals.



 

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.



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



This still needs a bit of cosmetic fettling.

Steve

Offline Steve Crow

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Re: Cosworth V8 1:12 scale
« Reply #16 on: November 24, 2020, 11:39:35 AM »
Here is some of the crank in situ.









Steve

Offline nj111

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Re: Cosworth V8 1:12 scale
« Reply #17 on: November 24, 2020, 12:44:54 PM »
Great little project! Well executed!
Nick

Offline Steve Crow

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Re: Cosworth V8 1:12 scale
« Reply #18 on: November 25, 2020, 04:10:46 PM »
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.

 



 

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.

Offline Steve Crow

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Re: Cosworth V8 1:12 scale
« Reply #19 on: November 25, 2020, 04:12:15 PM »
Here is another cross-section, this time between the cylinders.



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

Offline Steve Crow

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Re: Cosworth V8 1:12 scale
« Reply #20 on: November 25, 2020, 04:13:43 PM »
This is the gear train for the cams. The camshafts rotate counter to the crank. The blue gears (EN1A) are driven or drive and the orange/yellow (brass/nickel silver) ones idle.



This is quite a bit simpler than the full-size engine, which has compound gears, but it does resemble it.

The gears are Mod 0.3 as I have a set of involute cutters. It would work in Mod 0.4 or 0.5 as well.

This is part of the build I'm looking forward to most.

Steve

Offline Roger B

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Re: Cosworth V8 1:12 scale
« Reply #21 on: November 25, 2020, 04:55:50 PM »
I use two European sources for small fastenings:

https://www.mikromodellbau.de/artikelauswahl.php?kid=173&sprache=2

https://micro-model.ch/de/1483-din84-m1

Hopefully someone will suggest a more local source for you.

I'm enjoying someone else working with very small things  :ThumbsUp:  :ThumbsUp:  :wine1:
Best regards

Roger

Offline ddmckee54

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Re: Cosworth V8 1:12 scale
« Reply #22 on: November 25, 2020, 04:58:54 PM »
I love the fact that you're building this with a Sherline.  (I've got both a Sherline and a Unimat.)

The fact that you're mostly building it out of steel is even more impressive.  Why did you chose to use steel for the block and heads over something easier to machine like aluminum or brass?

Don

Online sco

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Re: Cosworth V8 1:12 scale
« Reply #23 on: November 25, 2020, 05:12:22 PM »
I recently used this site for some small screws: http://www.modern-screws.co.uk/.  They seem good quality but were expensive but then the small sizes all seem expensive for what you get by weight!

Looking at your block cross-section between the cylinders - is there definitely room for those head fasteners - the walls must be getting very thin?

Simon.
Ars longa, vita brevis.

Offline Jo

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Re: Cosworth V8 1:12 scale
« Reply #24 on: November 25, 2020, 05:39:48 PM »
The Swiss screws are very nice I normally buy mine in the UK from Everett Model Engineering Supplies. I am also a masochist and make my own small screws, so far nothing under 16BA  :paranoia: 

What sizes are spectacle and watch screws? I notice that Fleabay has a lots of small metric screw suppliers (they are not very pretty)

Jo
« Last Edit: November 25, 2020, 05:54:08 PM by Jo »
Enjoyment is more important than achievement.

Offline Jasonb

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Re: Cosworth V8 1:12 scale
« Reply #25 on: November 25, 2020, 05:47:51 PM »
GHW do some neat slotted and cap head screws down to M1. I tend to use them for small hex metric fixings

https://ghw-modellbau.de/index.php?cPath=4_108&MODsid=02c5200eaa0f2b2c7410f27ba5f3cda5

Offline Steve Crow

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Re: Cosworth V8 1:12 scale
« Reply #26 on: November 25, 2020, 06:51:57 PM »
Thank you for all the suggestions regarding small screws. I will look through them all before making the M1/14BA decision.

Then there are the taps to consider - all a bit spendy. I want good ones.

I would prefer steel over stainless because I want to blue them but I can live with SS if they are good quality. I've found that the British made 12BA steel screws I've been using are far better quality than any stainless I've seen.

The ebay spectacle and watch screws are particularly shabby.

I have made my own screws, one at M1 x 0.25 but it took me all day and it was just to see if I could.  I need over 50 at that size so that's out of the question.

I need 50 modified M1.6 allen screws but I've done all those and tapped the holes. Also just over 50 12BA cheeseheads. I've modified about half of them so far, I'm doing it as I need them.

Steve

Offline Steve Crow

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Re: Cosworth V8 1:12 scale
« Reply #27 on: November 25, 2020, 06:59:11 PM »
Looking at your block cross-section between the cylinders - is there definitely room for those head fasteners - the walls must be getting very thin?

Simon.

I had a bit of a measure and the thinnest wall is 0.4mm - plenty of meat!

Steve





Offline Jo

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Re: Cosworth V8 1:12 scale
« Reply #28 on: November 25, 2020, 08:49:37 PM »
I need 50 modified M1.6 allen screws but I've done all those and tapped the holes. Also just over 50 12BA cheeseheads. I've modified about half of them so far, I'm doing it as I need them.

Be careful about mixing threads  :paranoia: I normally try to keep to one type i.e BA & ME, or Metric, or UNC/UNF. If you loose  :facepalm2: a screw you have a better chance of replacing it without getting it wrong and crossing the threads.

Jo
Enjoyment is more important than achievement.

Offline gbritnell

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Re: Cosworth V8 1:12 scale
« Reply #29 on: November 26, 2020, 12:05:26 AM »
I tried to figure out your crank to cam gear ratio but it didn't seem to come out to 2:1
gbritnell
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