That's closer to 1215ci, but still not there yet. Typical - gotta have the biggest bore and stroke you can in a Mini (1500+cc), gotta take the Rover V8 as far as you can (bored out, stroker crank)... Is there any other way?

Nah , it started life as a P76 4.4litre donk, (The Rover`s "big brother" engine) so it wasn`t hard to make it that bit bigger now with 4.7 litres & T04 turbo

i helped a friend build a 6-litre P76 donk once,,, don`t know if it`s still running tho

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

try www.marinediesels.co.uk and www.enginehistory.org

or do a search on "sectional crankshaft types"

the method is not new and these design of cranks are very strong

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

I,ve been having a look at the sectional cranks but can't find that much information, the only good description I got was off an Engineering Forum

"The crank is sectional. The wings are billet machined so that all are the exact same. The main journals as well as rod journals are also billet machined. The parts are put together by the use of induction heating or pressing. The journals are designed with a flat side that fits against a flat side in the wing. Kind of a D shaped joint. There are no welds or oil galleries. All the parts are 4340 alloy. These designs are patent pending. The bearings will be heavy duty needle bearings with inner races that are pressed over the machined journals. With the inner races pressed over the journals the needle bearing slides over the journal before the wings are pressed on the journals. The engine will use a standard main cap and rod cap arrangement. Since all parts are CNC machined,I hope the finished product is already in balance. I still want to use a dampener however, one with a serpentine belt groove for the alternator. We will be using a gear driven coolant pump"

I have to assume that getting one CNC'd will be $$$$ as a one off but once all of the correct measurements and a 3D program made it would be easier to replicate the process.

I am quite happy to admit it's in area beyond my knowledge and expertise but I would be interested to learn.


When I did a Google Image search the only thing I found was an Eccentric Shaft with anti-friction roller bearings which I have to assume is similar but CNC'd as a single piece


[img][img]http://img32.imageshack.us/img32/8462/eccshaftfinal0preview.jpg[/img][/img]




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the marine diesel site shows the world biggest crank shafts being made.the mains are 1.5mts dia and the big ends are 1.2m dia and the engine is 9 cylinders in-line.
These cranks have the big end and webs forged from single piece of steel and the crank pins are fitted with round bore with shrink fit. the whole thing is then machined.
Honda has done some interesting development work with cranks for bike engines. these consist of individual pins for mains and bigends that have a taper on each end. the pins are joined with a shaped web[for balancing] that has tapered holes set for the stroke. the brgs are inner race needle rollers both mains and big ends.
once the tapers are pressed into position they use a counter-sunk head bolt to hold the webs into position.
The main advantage is single inner races instead of split races . with this construction any stroke and conrod position can be used with minimal changes to the crank design. the design is just a variation of cranks used in out-board engines.
These would be easier to manufacture than a billet crank and the grain of the material is not cut thru .

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Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

David, have you seen how Mercedes used to make the cranks in their F1 cars in the 54/55 season? They used the "Hirth" method of joining the sections of crank.
All roller bearings and one piece con-rods. Very nice stuff.
I will see if I can find a photo.

they are very nicely made cranks.some of the radial air craft engines have used a similar system.
Honda were building some for experimental F1 engines , but it has been shelved. the bike cranks that I have seen details and specs on are very impressive. Honda has incorperated a couple of ideas to come up with a good design. the taper idea allows needle brgs and a taper [ male/female ] is the best locking mechanisium for joining two pieces.
There are other methods that have been used like spline faces and clamp systems , but the honda ones are good from an engineering aspect.
Taper reamers are easy to get and lapping the two joints with shrink fit and a bolt to hold the webs on , they will never fall apart.
time to play with another mad idea

_________________
Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

I,m just waiting to here back from Wiseco about the K810 Kit which is the overbore 69mm piston size for the Kawasaki GPZ 750 , they were a lot more friendly this time as I was able to give them a part No .



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I personally would be looking at a piston out of a car and trying to find one to suit. The bike engines are very short stroke and cut away skirts and small gudeon pins.
I have pistons out of honda 600's, 900's ,and 1100's and they cover the range from 68mm thru to 76mm.
The bike pistons will need new rods to match up with stroke/ deck height etc and the gudeons modified.
I may be completely wrong ,but looking at the difference in stroke and then calculating the final velocity[ acceleration/de-celeration] of the piston for the new stroke and angle of force on rod the bike piston might be subjected to too much stress.

_________________
Research is the difference between speculation and investment. Anyone who copys some one else will always be second
www.minisprintgt.com

Yamaha RZ250/350/500 2 stroke crankshafts are multi-piece with needle roller bearings. Beautiful machines, I miss my RZ250 My mate had his turned into a RZ350 with higher compression and pig porting by a guy (Hi Dave if you are watching ) who used to be a mechanic for Yamaha racing in Japan. Man what a monster of a bike it was

here are some pics - Notice how all the counterweighting is very nicely contained in a compact little cylinder, quite unlike an A-series crank. Also note how short a stroke these things are, again guite unlike an A-series crank. Remember too that this was early 80's technology. God knows what they have now....

RZ500 front crankshaft - yes they had two separate crankshafts


RZ250/350 crankshaft exploded diagram



And here is a guy doing a rebuild of a RZ350 engine and gearbox. Reminds me of my youth (no I am not that old, but it was 19 years ago )

http://www.scooterhelp.com/RZ_help/restorations/rebuild.transmission.html

cheers
michael

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the world is a book, and those who do not travel read only a page
66 Mini Minor sponsored by http://www.lifeonthehedge.com.au/ The Dog Harness Specialists
It was a pleasure ausmini. I'll miss all you misfits and reprobates

I run a piston made from a motorcycle forging in an A-series 1275. The piston weighs 229 grams including its 50 gram pin and swings on a 6-inch rod which weighs about 450 grams. BTW, an Omega 1275 piston weighs closer to 360 grams and costs as much or more than my piston.