Hi there,
I was just looking on Swiftune site and read this article on a new type of crankshaft, rods and pistons that they have developed.
Check it out.
http://www.swiftune.com/NewsArticle/80/ ... eries.aspx

Graham Russell and other racers already run an 8 counterweight nitrided crank that looks like this, which are made in Melbourne... cost around $4K I think.

It's a bit of a long bow Swiftune calling theirs a `5 main bearing crank' though... the block and this crank still only run with 3 bearings.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Simon Gardner (Powerplay automotive) had a crank like this years ago and as the Doc said, Ian Shrugg at Crankshaft Rebuilders here in Melbourne will make you the same kind of thing, at a cost. A lot of money for little gain, you can buy a lot of "normal" 1275 cranks for that kind of money.

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Simon also did those '2 up, 2 down' mini cranks, which had some serious advantages too, but not cheap.

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Swiftune actually writes in that article that they "create[!] two “false” journals which enables the counterbalance to be doubled" - there's nothing there saying it's a 5 bearing crank. It's just designed like one... And that idea I like. A lot.

Most certainly a waste of money for a road engine that spends 95% of it's life below 3000RPM, but on a full-out racer...?

What do they say? The first few BHP are cheap, but after that you get progessively less for exponetially more money... If that makes sense

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No speakers, no bodykits, no six-inch spacers, no spak filler, no bullshit

that type of crank was being made by rev-master back in the early 70's but with a big difference.
With the swift tune crank the counter weights are all part of the crank and you can not get past them to drill No 2& 3 bigend journals. They have drilled 1 & 4.
The rev-master had the webs smaller and were machined with a dove tail arrangement this way you could drill the 2 center journals and the counterweights were fitted side ways over the dove tail and bolted on. The weights were wider and closer to the center line of the crank and made balancing easier and weight could be added or removed by changing the counter weights.
The flywheel end was also bored and a flange type weight added to the front to help with longitudinal balance. They also had 3 oil holes drilled instead of cross drilling . Less stress cracking in the journals.
Much easier to make as you are machining a smaller diameter round and less out of balance during machining.
I used one for years[ the advantage of working there] and never had any trouble with it even with exploded flywheels and a few broken rods.

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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

Hi 850man
Yes simon did use one of these crank after he rang me and asked could he use my design[he saw mine being made at Ians] I didnt just design these cranks for a better counter balance but also to take the harmonics away from the valve springs the valve springs that i had made were bigger dia and taller which all the valve spring experts said should work better than any thing else they didn't because a mini being a mini has very funny harmonics that happens to up set mini valve springs with agresive camshafts,but with these cranks and some other fiddles the springs now work and so do some of my camshafts.
this is why i like to step out side the circle so i can make more hp than other people and keep the minis up near the front.
Also if you can wait a little bit these cranks will become cheaper as MED are now going to copy my cranks.
Graham Russell

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"It's better to be not informed than ill-informed"

Hi gt mowog
The crank that you speak of, Simon offered to me to try and sort out but it has very serious balance problems that can not be cured even with lots of heavy metal stuck in the counter weights,it does not work.
Graham Russell

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"It's better to be not informed than ill-informed"

Is the two up and two down crank really the same the same crank but different cam and firing order to make what is in effect, two twin piston singles?
Some use this in speedway side cars.
They feel these motors give more traction on loose surfaces.
The reasoning being that motor behaves like two singles leaving a lapse of power during a revolution of the motor giving the wheel an opportunity to bite.

Hi MG Rocket
Thats why the GP bikes tried it to try to control wheel spin out of coners,gave a much better dilivery of power, but they didn't stay with it for very long
Graham Russell

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"It's better to be not informed than ill-informed"

Sorry i forgot to say they were only using 2 strokes back then.

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"It's better to be not informed than ill-informed"

The blokes that ride these 4 cylinder twins say they run out of puff at the top end so no good for GP racing.
I would imagine they would be particularly hard on a 3 bearing crank?

GR why are you fiddling around with spring rates to get the harmonics between the crank shaft and the cam shaft to balance out.

A chain drive between a crank and a cam is the best drive for agressive cams and springs as the construction of the chain is a perfect vibration absorber. Just do what many engine designers do, fit a effective damper to the drive on the cam shaft end so that the harmonics of the cam are absorbed and the chain seperates the harmonics between the cam and the crank.

These is nothing new about this idea many marine engines have far greater torsional problems with their valve gear especially with valves with bridge rockers and they fit silicon dampers to the drives.Even the fuel pumps created massive torsional problems and they have a individual drive with a damper to drive the pumps.

engines like sulzer and m.a.n use pressurized oil dampers on all the drive shafts on their engines and all the drives between the crank and the other shafts are all chain drives to overcome shaft vibrations. The early sulzers around 100,000 HP had gear drives and they all had massive gear train failures. They even now run pneumatic valves with hydraulic actuators to actuate the valves from the cam to reduce torsional vibration problems.

The torsional vibrations in a mini engine is nothing compared to a big marine engine or a steam turbine propulsional unit.

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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

Hi David
Sorry David but i have to disagree and so do many engine builders around the world including nascar teams fomula one engine designers [cosworth] and many others that the chain is the worse thing in an engine to create hormonics, it is the easiest and cheapest way to get a drive from a to b.
And as for vibration i have yet to find a four cylinder engine that vibrates more than a mini after using a very expencive machine to measure both vibration and harmonics on many engines i stand by comment that the mini is one the worst that i have ever tested apart from a single cylinder bike engine we tested once.
And as for valve springs have a look around at the masive amount of time and money being spent by spring makers to try and stop valve springs from getting out of control caused by agressive cam design and harmonics from the engine.
A little note of intrest when Keith Duckworth of cosworth fame started out on his own and started designing the fomula junior engines he looked at the BMC cam designs but would not go down that path as the cams were to agressive an could not be controled by the springs that were around at that time,and if you look at his cams back then he used slower opening ramps and very long duration with not a lot of lift and just used a lot of rpm 10,000 to make the hp, a lot of rpm back then
Graham Russell

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"It's better to be not informed than ill-informed"

Graham, the point I was getting at is a roller chain for a drive will transmit more power than other drive systems and is more suitable for shock load transmission. It has it's limitations and thats why drives like high velocity chains, HTD toothed belts and gears are used. F1 engines use herring bone gears with dampers fitted internally.

A roller chain can not create a harmonic only transmit the harmonics from the driver to the driven shaft. It's design allows it to flex and therefore absorbs the vibration and in doing so it will fail. With a engine the 2 sets of torsional vibrations from the crank and the cam will overlap[node point] and this causes the chain to vibrate and fail.

With any drive and driven application in a engine IE high velocity chain or HTD tooted belt or gears will all suffer from the same problem and the application is the thing which determins the type of drive.
Any destruction of these drives can be reduced by fitting a damper on both the crank shaft and the cam shaft.

In your application and depending on what drive system you use, a cam damper will reduce the harmonics between crank and cam. Thats why a steam turbine running at 25,000 + RPM with a final output shaft speed of 100 has herring bone gears with internal dampers and dampers on the quill shafts. Turbines do not like torsional vibrations .

Sure many engine designers do not use roller chains but they fit dampers to minimise drive failure.

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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