ESE's works engine tuner

[speedpro]

I've seen a crank in a bucket with screws into the crank webs and then carbon string wound all round them and then resin tipped in while the crank was in a mould. End result carbon-fibre filler for a full circle crank.

[Yow Ling]

I've seen a crank in a bucket with screws into the crank webs and then carbon string wound all round them and then resin tipped in while the crank was in a mould. End result carbon-fibre filler for a full circle crank.

Sounds like a wind up to me

[husaberg]

cork won't stay in the web cut outs (incomplete web). I was intending on trying it, but clearly Frits for example will likely know if it is a waste of time, but I'm assuming the RSA cranks were full circle for a reason. I don't have a heap of time to try everything I want, so very happy to learn without having to make every mistake myself.

Have a look here there are people who have successfully used Cork and other methods on RZ500's
http://www.rzrd500.com/500phpBB2/vie...f906fd0ff1930c

[2T Institute]

Made a nylon stuffer in place of the original plastic one 'someone' broke when rebuilding a KDX200 crank. Still in there today.

[Frits Overmars]

yes, but where in the crankcase was the volume concentrated?
if for example one had the 'compromise' of having a clearance over the web to case of 1mm or above to limit shear, but otherwise had as little volume in the web area, - and more area underneath the transfers to draw easily from; -would that be a perceived advantage, rather than have to pull from the violently rotating webs?
Indeed incomplete webs are effectively paddles thrashing more air about in an already turbulent area. Just thinking about the comment of the incoming gasses & the rotation of the crank web comments as well.

Good point, Dave; in fact several good points.
Most of the volume is concentrated in the transfer ducts. Then there is the volume inside the piston of course, and the 1 mm shear-avoiding clearance at all surfaces of the crank.
But that is not nearly enough volume. If you take another look at the Aprilia crank below left, you will notice that the space between the crank webs is the same as the space needed for the big end bearing. In other words: the crank webs have flat insides, good for another 60 cc or so, if I remember correctly.
Additional benefits: the con rod has an easier time pushing the mixture aside as it moves between the webs, and the big end bearing gets a lot more cooling and lubrication because it is not shrouded in any way.
Because there are no overhung bobweights, the crank webs are stuffed with tungsten to get the balance factor right.
In the RSA125, the con rod was lengthened from the RSW's 115 mm to 120 mm to create even more crankcase volume.

The paddling is a mixed blessing; it creates aerodynamical drag but it also greatly improves the homogenity of the mixture.
Smooth, full-circle crank webs have the advantage that there is little mixture hiding in nooks and crannies. An example of it's importance: in a certain engine there were 20 mm spaces between the crankshaft bearings and the seals. these ill-accessible volumes acted as pneumatic dampers on the crankcase pressure fluctuation. Filling those volumes with plastic bushes gave a measurable improvement.

Summary: you need a large crankcase volume. Ideally all of this volume should be situated in the transfer ducts. In real life you will also need to lodge part of this volume between crankshaft and piston, i.e: use a long con rod. Avoid nooks and crannies. Crankshafts should be small and smooth. Big end bearings must never be shrouded by recesses in the crank webs or by stuffers.

The picture right below shows, wait for it, an RSA125-crank with stuffers...
After Jan Thiel went into retirement in 2008, some geniuses at the factory grabbed their chance to 'correct' the errors that Jan left behind, without even testing the result because 'everybody knows the smaller the crankcase volume the better'. But they never could understand why a 2011 RSA125 was slower than a 2007 model (just look at the 125 cc top speeds on any GP-track). O, the joy of working with Italians.....

[TZ350]

Thanks for that .......

I guess the ballancing hole stuffers stay but I could look at opening up the inside of the crank.

The present RGV250 rod is 105mm and if I want to try more case volume I could use a 110mm RZ350 rod.

[Frits Overmars]

I guess the hole stuffers stay but we will look at opening up the inside of the crank.
The present RGV250 rod is 105mm and if I want to try more volume I could use a 110mm RZ350 rod.

...

[TZ350]

Thanks Frits, your input helps a lot .... there is only so much time and effort possible and your comments give me confidence about the direction to take.

[Frits Overmars]

Thanks Frits, your input helps a lot .... there is only so much time and effort possible and your comments give me confidence about the direction to take.

Be careful with that, TeeZee.
We drive on the right side of the road; you drive on the wrong side. We will not mention driving in Italy... (but Teheran or Calcutta cannot possibly be worse ).

On a more serious note: I just took a look at the crank web + pin you showed above. As a rule-of-thumb the web material around the crank pin hole should have a thickness of at least 50% of the pin diameter. I'm afraid yours hasn't. And I am not even regarding the large bevel....

[dinamik2t]

We will not mention driving in Italy...

A driver in Italy has the right to drive in any road line, direction, parks, pavements etc and still, if that leads to an accident, it's always the other guy's fault - even if he's a pedestrian

[TZ350]

I just took a look at the crank web + pin you showed above. As a rule-of-thumb the web material around the crank pin hole should have a thickness of at least 50% of the pin diameter. I'm afraid yours hasn't. And I am not even regarding the large bevel....

50%,I had thought about it but like fork rake and trail I didn't know the numbers ... so thanks for the heads up.



Original Suzuki pin and rod are on the left.

The bigend hole was bored out to 22m so that I could use a 110mm RZ350 rod or a 105mm RGV250 one. The Suzuki rod has a 14mm L/E pin and the RZ and RGV have 16mm L/E pins and 16 allows a greater selection of pistons and increased case volume.



The inner faces of the flywheel have been machined back a little and test fitting a RGV250 rod. I use original RGV silver caged bigend brgs with individual rollers. But for test fitting etc an old RD B/E with trapped rollers is much easier to work with.



There is not much room around the bigend available for ballancing. I plan on using Mallory slugs pressed into the counter weight area on the next crank.



The crank was skimmed 1mm all over for a 2mm clearance in the cases. Red line is the smaller 2mm clearance crank.



It’s one of the beauties of Buckets, pretty much everything is a compromise as things are mostly cobbled together from something else and it’s the key to Buckets affordability.

Not many people myself included have the resources to build something like a crankshaft completely from scratch but most people can cobble different bits together to make something special. Like addapting wheels from one make of bike to another like is often done with FXR150's or fitting an RG400 cylinder to a Kawasaki bottom ends or other tricky stuff.

[dinamik2t]

TZ, that's a huge difference from 27.6 to 30.3hp !! Everything else was the same (jetting, advance etc)?

-------

I was searching randomly about head designs and found this at the bimotion page:



Especially on the second paragraph, the zero-radius stage transitions and inner curves seem to work as pockets of low velocity gas, that in their turn work as a heat barriers. And that would be the reason of the anti-detonation effect of toroid design.

[TZ350]

TZ, that's a huge difference from 27.6 to 30.3hp !! Everything else was the same (jetting, advance etc)?

I was searching randomly about head designs and found this at the bimotion page:

Interesting about the Toroid head.

I have just re-checked, and Ooops I refered to the wrong post and graph.



The Red line is the smaller crank with 2mm clearance. (the original post is on page 155) I am not sure why the improvement is all at the bottom end and drops of earlier at the top.

[husaberg]

Dont worry I not one of them, why would the mixture come from round the spinning cranky things , there is nothing going on there to pump anything, my mental moddeling just has a blob of gas mix under and around the piston that gently bumps the mixture waiting in the transfers into the cylinder. With what frits says about the rsa and rsw ccv's , would indicate that the pipe is more involved than the crankcase compression in filling the cylinder

In saying that Wobbly is using some aluminium stuffers on my crank, i think this has to do with the paddle problem.

in this thread is the stuffing http://www.kiwibiker.co.nz/forums/sh...post1130142699

I though a lot of the volume reduction was because you were going from 125 to 100cc as well.

From memory the NSR (Vanessa) reworking in thie intake and crankcase area will need to be much less radical
Vanessa's crank to destroke to 50mm ish however requires a smaller pin otherwise it will overlap the main bearing journals. (You already have the correct stroke there Mike what was i thinking)
This is why my first thought was to use a different crank and i think i may have found one now will suit.
The main problem was the unusual (for Honda) spline. (Gee Honda What were you thinking)
Wob says of course the std crank can work worked around with welding machining and holes done with electric arc etc.
But the budget is in danger of being stretched past its original limit. (Plus i want to use as many std parts as possible)

[Frits Overmars]

...The Red line is the smaller crank with 2mm clearance. (the original post is on page 155) I am not sure why the improvement is all at the bottom end and drops of earlier at the top.

Helmholtz frequency, my dear Watson. The smaller crank will give the pipe more crankcase volume to breathe from. This larger volume will also lower the resonance frequency of the inlet system, hence the drop at high rpm. It can be compensated with a shorter inlet tract, a bigger carb diameter and a later inlet closure. To put it real simple: if you have more volume, you need more time to fill it. But more time, i.e. later closure, has adverse effects at low revs. So my preference is a shorter tract (unless you go the 24/7-way and employ a reed for the low revs, and swing it out of the way at high revs).