3K Cross Plane Crankshaft

[KO 10]

G-day i've been playing around with the idea to get a cross plane crank made for a 3k as i've also been playing around with a mates XS 650 yamaha and he has turned the crank (via a slpine) to make a 270 degree C/Angle this gives him excelent traction due to the large brake in power.The yammy R1 has a CPC and showes no differance in power but does have smoother ride and less stress on the internals and a higher usable rev range these are all posative things for a motor bike ,as for a car not sure how this will translate but in a ke10 the same results should occure being light and needing traction plus rpm, ( please don't get carried away with timing and cams cause its a bit confusing i have spent a fair bit of mind bending to get the timming with an elec dizzy from a V8 and the came grinding sorted )

 

The question is has any one done this ? does anyone know some one who could make one,I sould be able to cut and shut two cranks to make one but don't know any one who has welded a crank then regroud with any sucsess

 

I have posted a photo of a cross plane crank from an R1 (this was taken from a blog called Dark Rider Blog)

[altezzaclub]

I think you'd have to make a crank from scratch. You could cut one up and re-weld it, but that welding would have to be both perfect and amazingly accurate. You only have a handful of thou to grind each journal and fit undersized bearings. Then you'd need to sort the balance weights, and they would be bigger than stock wouldn't they?

 

For the amount of power being made it wouldn't be hard for a good engineer to make one up, something lightweight & it doesn't need to be that strong a steel, but I imagine it would be expensive!

 

 

 

 

 

[kickn5k]

For the amount of power being made it wouldn't be hard for a good engineer to make one up, something lightweight & it doesn't need to be that strong a steel, but I imagine it would be expensive!

Crankshaft Rebuilders and I think the shop that makes those billet SR/4G EVO blocks are the only shops that make cranks in AUS. You'd also be looking at $4k at a minimum.

 

Stu.

[KO 10]

I think you'd have to make a crank from scratch. You could cut one up and re-weld it, but that welding would have to be both perfect and amazingly accurate. You only have a handful of thou to grind each journal and fit undersized bearings. Then you'd need to sort the balance weights, and they would be bigger than stock wouldn't they?

 

For the amount of power being made it wouldn't be hard for a good engineer to make one up, something lightweight & it doesn't need to be that strong a steel, but I imagine it would be expensive!

 

I'd have to start with two standard cranks split them spigot then press them back together making one out of two then machine it between centers but even then it'll be dodgy then the counter weight problem they are bigger for a CPC so balancing issues ,I've never machined up a crank for a car but have for gear boxes and bits for farmers the balancing on a car has to be spot on no doubt but maybe some one out there could help with that one

[KO 10]

Crankshaft Rebuilders and I think the shop that makes those billet SR/4G EVO blocks are the only shops that make cranks in AUS. You'd also be looking at $4k at a minimum.

 

Stu.

 

4K bugga it'd wana be gold plated ;)but surly some one else makes cranks i was even thinking of aprotching a Tafe to do some thing like this as a project or any one with the gear

But thanks anyway i'll givem a call, any ideas where else would very handy

[KO 10]

 

the counter weight problem they are bigger for a CPC so balancing issues

 

edit the counter weight are the same ,even smaller if anything this type of crank sound out of balance due to the firing order being at 270 180 90 180 but actually runs smoother

[altezzaclub]

Yes, you could pick any firing order from the cam you use, but it always ends up with an asymmetrical spread of 90deg divisions between cylinders firing. I had to draw diagrams of pistons out to 720deg to check! :laff:

[altezzaclub]

Fascinating stuff- love to see you do it! So it will accelerate a bike faster in a similar way to a lightened flywheel.

 

 

 

 

http://darkriderindia.blogspot.com/2010/02/cross-plane-crankshaft.html

 

To understand it, first imagine a crankshaft on its own, no pistons or conrods, spinning in friction-free bearings. There’s nothing to slow it down or speed it up so it just keeps spinning at a smooth, constant speed. Now attach the conrods and pistons, and for the sake of this mind experiment, we’ll make them friction-free too, so you can spin the crank again and the pistons bob up and down, and the whole system keeps on rotating and reciprocating.

 

 

 

At this stage there’s no combustion or valve gear or anything to confuse the issue, and crucially, there is no energy being put into our system and none being extracted or lost. This matter because it is a fundamental law of the universe that energy cannot be created or destroyed, only converted into another form – physicists know this as the first law of thermodynamics.

 

Within this system, the pistons are travelling at high speed when they’re half way along their cylinders, and at this point they have a lot of kinetic energy. Yet 90 degrees of crankshaft rotation later, all four pistons are stationary, two at the top, two at the bottom. Their kinetic energy hasn’t simply vanished because it can’t: instead it’s been transferred to the crankshaft, which was responsible for slowing the pistons down. As a result, the crank itself has increased its speed. Another 90 degrees on and the pistons are back up to maximum speed, accelerated by the crank which has returned some energy to them and in turn, it’s slowed down again.

 

In a full rotation the crank will have sped up and slowed down twice, generating rapid negative and positive torque pulses completely independent of the torque produced by the combustion. This constant pulsing torque is like a background noise to the main torque output, blurring its edges and taking away a small element of rider control and precision as he tries to hold the back tyre on the very edge of its grip.

Basically what they do is they take the standard 1-2-4-3 firing order, flat plane crankshaft and move both cylinders 2 and 3 by 90 degrees and 4 by 180. This yields a firing interval of 270-180-90-180. It's essentially one bank of a V8. Their claim is that by moving cylinders 2 and 3 out of the plane, the inertial torque is split evenly throughout the cycle, yielding a smoother variation in crankshaft.

Engineers ran their firing order and phasing through the crankshaft program and got the same mean torque throughout the cycle. This makes sense (same amount of fuel and air combusted over the same period of time). Okay, so same mean power is produced over the same cycle. What is different are the peaks and valleys. cross plane crank are smaller (blue line) as opposed to the normal flat plane (pink line).

 

 

On Yamaha’s cross-plane crankshaft, these fluctuations are all but reduced. In this layout the crankpins are distributed at 90 degrees to each other around the crankshaft (in two planes which form a cross). So as one piston is slowing down and losing energy to the crank, another is speeding up and taking the same amount back. At no point do all the pistons stop together, as they do on a flat-plane crank. Instead the energy flow is evened out and the rotation of the crank is almost completely smooth and steady. This improves the ability of a cross-plane-crank, in-line-four bike to accelerate out of corners.

 

 

[KO 10]

Ah so you've read dark riders blog its a good read too ,the thing with the timming is that the dizzy on the standard crank wont work because the 270 dgre is 3\4 of a rotation of the crank and only 3\8 of a revolution in the dizzy so 270 dgre ends up being 135 dgre put in order this is the points position 0-135-225-270 this means the points have to close between the standard dizzy points the way around this well the only way round i can see is to use a V8 elec dizzy and remove the loabs to suit and only use the n-1 n-4 n-6 n-7 leads as for the cam it'll need to be built up then reground to suit still trying to get my head around that one to.

[altezzaclub]

LoL!!! I hadn't thought of the dizzy! Forget it- fully electronic with a crank angle sensor!

 

The crank I was thinking could be sliced through the three main-bearing journals then re-welded and ground to size. The oilways would need re-driling too.

 

I don't know if the cam can be similarly treated, but with welding these days they can do damm near anything. Slice between the lobes in the same way as the crank and re-weld it.

 

 

[KO 10]

Do crank angle sensors need a ecu ???

 

Yep the oil holes will be ok if the welds are offcenter but if not a few grub screws should fill up any holes i drill

to match em up

The cam luckly dos'nt need much to be ground rite no need to cut thank god they just seem to be able to build it up and grind it back (but the positioning mmmm ???)

may have foud some one to build the crank for me to so a few phone calls and i'll see what it'll cost

Edited November 23, 2011 by KO 10

[altezzaclub]

Do crank angle sensors need a ecu ???

 

Yes, but probably Jaycar have some electronic kit that will do it. You need some sort of ECU to read the input from a CAS and send a variable signal to the coil. The variable part will be needed to have an advance curve related to rpm.

 

Look up the Megajolt DIS (distributorless ignition system) and ask them if it will handle such weird timing. I think a lot of them are programmed for firing 180deg apart.

 

 

 

Then you start thinking .. the ECU can take account of temperature so does cold/warm mixture if it was injected, so if I just add 7K injectors and if I fitted an oxy sensor and...

 

..it never stops!

Edited November 23, 2011 by altezzaclub

[irokin]

It stops when you stop fiddling around with toy kits and buy something designed by an electrical engineer and pay him for his time and effort.

 

Personally I can't see a crank welded that many times lasting more than a few hours before coming apart, best case scenario.

 

Audi turned 90 degree V8 cranks into 180 degree cranks by heating and twisting production blanks before grinding and finishing. I doubt you'd have much success with that method, without masses of trial and error and a well built jig to twist them.

 

 

I think, realistically, the only way you'll pull this off is with CAD and CNC. Its not as expensive as you might think, but still way too much money to spend on a K motor.

[ke70dave]

welding a crank?

 

good luck! just not going to work.

 

i can see the merits of the cross plane crank, but i just don't think your going to get the advantage out of it. they say the advantages come in the high RPM's (12000+..)

 

the yamaha R1 engine they refer to is, is 998 cc, 78mm bore and 52mm stroke.

 

it is this 52mm stroke that makes this cross plane thing viable, less stroke slower maximum piston speed for a given RPM. it makes its maximum power at ~12000 rpm, and has a rev limit of 13750 rpm. and it will rev that high all day.

 

getting those sorts of rpm out of a K motor is going to be a very expensive task, not even mentioning reliability.....

 

assuming you can get a crank made that will last more than 20mins, you would want to attempt to reduce that stroke. a 4k has a stroke of 73mm...too high...a 3k has a stroke of 66mm...getting better....i dunno what a 1k or a 2k has. if its less, that would be the engine to start with!

 

else get a custom crank made up for 53mm stroke, and take 20mm off the top of a 4k block.

 

annndd when you get it up and running, the block will probably explode, as it was made in the 1970's:P

[irokin]

You can get a custom designed and made CNC aluminium block for around the $10k mark Dave ;)