DOHC V8 Engine

[mikemill]

Having made many engines over the years, both steam and I.C. they were all designed by others. Recent acquisition of a cnc mill , and the wish to design and build an engine myself, I cast around for a subject.
Formula One teams have used the V form of engine in 8,10 and 12 cylinder versions since it started in 1952, and could be concidered the pinicle of performance engine design each in its era. So the temptation to build a small version of a V8 racing engine proved to difficult to resist. After a lot of research I settled on a double overhead cam, four valve per cylinder layout, of which many examples have been used by varios F1 teams, that should be enough to drive one mad for a couple of years!!

The scale is roughly 1/3 (as it is not a model of a specific engine) making components a sensable size to work on, and not watch making
Bore 1.350" Stroke 1" . Here are a couple of pics of the crank assembly, I made the perspex block as a visual check on my layout ideas.

I would be interested to hear of any advice on the subject.

Thanks

Mike

[moulin]

awesome... giong to follow this one closely...
Thanks for sharing

GJ

[dynosor]

Very nice. Looks like you should be giving advice, not asking for it.

Is this a cross plane rather than flat plane V8 or does it have non-conventional throws?

http://www.autozine.org/technical_sc...ne/smooth4.htm

[mikemill]

Hi Dynosor

The crank is cross plane design, thanks for the compliment, but you assume I am a experianced engine designer, far from it, an experianced metal basher yes, but thats why I am attemting this task.

Your link has taught me somthing about crank balance I was not aware of, so asking for advice works. This is the genious of the internet and this site, were we can exchange thoughts and learn from one another.

Thanks

Mike

[dynosor]

Mike

What alloy did you use for the crank at what hardness? Is that coating nitriding? Did you rotate the blank about 5 centers in turn or mill in 3D?

I have been playing around with a simple design to facilitate machining on a manual mill:
http://www.cnczone.com/forums/showth...t=39626&page=2

[mikemill]

Dynosor

The crank had 5 centres and is made from 2"od EN1A and left soft, con rods have phos bronze shells for big end and a bush for little end. My approch to components that in industry would be heat treated and ground is don't go there! as I dont intend to run the engine at high revs, and once made and proved it works it will join all the other models on the shelf.
I cut the journals on the cnc mill useing forth axis see pics. pins are .750"od so cut 1" square first then hex to .875", then .800" round, then finnished on lathe.
Your straight six looks good, your own design or based on a existing engine?
Do you know of Ron Colonna, have a look at his work www.ronsmodelengines.com his book on making the Offy is good referance
Keep up the good work

Mike

[dynosor]

Mike

The straight 6 is based on my own design and uses 1/4" increments for all major material removal on the crank, done with a 1/4" diameter endmill (0.020 nose radius). This results in 1" bore centers within the 7" long block.

I used a rotary table to rotate the crank blank between each of 4 pairs of centers on a manual Emco hobby mill (Austrian).

The crankshaft shown has main and crankpin journal diameters of 1/2 and 3/8"; the largest that would fit into a 1 1/8" OD 41L40 steel blank. The model of the crank has the same general layout, but with the journal sizes increased to 5/8 and 1/2" - have 1 3/8 and 1 1/2" OD 41L40 standing by...

The larger journal diameters better approximate a 1/4 scale BMW 330i crank, although the model's stroke is "short": Bore and stroke (.767 & .648") fit in the above layout, but were chosen to allow the use of OS model pistons and liners, if required. The plan is to try electroless nickel plating the Al bores after honing to see if this can be made to run without liners first...

Planning to make connecting rods from 2024 Al without bushes or shells. The main bearings are to be part of the 6061 block without shells. The bottom of the block will look like the top except it will be shallower without cylinder bores.

The main journals in the block were cut with a ball-nosed endmill in the same setup as roughing out the pockets and bores to maintain alignment. Main journals will be reamed to finished size once the top and bottom of the block are screwed together. Bearing pockets were cuts with a 3/8" diameter endmill (0.045 nose radius)

This design is optimized for manufacturing on a small capacity manual mill – should be a breeze on an industrial CNC…
Engine Design & Build

[dynosor]

Mike

Do you have any pics of your connecting rod endcap and bearing shell detail? My endcaps will be large enough to fit M3 screws - the smallest size I want to try and cut thread for...


By the way, Ron's model engines are impressive:

http://www.ronsmodelengines.com/Gas_Engines.html

[mikemill]

Dynosor
I defer to your knowledge of metalurgy regarding bearings, and I am aware that industry are experementing with plated sufaced aluminium instead of linners, but I would not have confidence in an alloy to alloy interface, as your lubrication has to be reliable, let alone wear.
Ron Colonna uses pure silver sheet for bearing shells, simple and effective. I will shoot some pics of big end for you , but not for a few days as other needs beckon.

Regards

Mike

[elmerfud]

I'm gonna use bronze weld and remachine it for the big end, should be ok, silver solder maybe a bit rugged, pours on thin and costs a bit too.
Man, your crank is superb, EN1a? Not familiar with that one, I was thinking EN26 crank and High tensile annealed rods, oh, just realised bronzing will brittle the ??K1045?? forgot exact material code. Cross drilling crank? Oil pumps?

[elmerfud]

crickets, the forum killer strikes again!

[Lola T70 MkIII]

How's progress, mikemill?

Dynosor, do you have a build thread?