Billet cylinder head

Shorter stroke would also allow a longer rod, dependent on piston pin location, maybe the best of both worlds :wink:

fdracing said

"moving 1 or 2 mm the cylinder foward help a lot to reduce that wear "

Offsetting the pin in the piston may achieve the same, and easier to do.

as you said it "may" , in fact it works on 95/98 mm piston , on 104/106 mm piston its a bit more complicated , they tilt more easely giving you more trouble than it should solve .

a steel liner with a good nikasil coating will do the job :wink:

spanner said:

Dr C
"I'm afraid that a very tall conrod will give a (too) large dwell, killing the inlet inertia too soon in the rpm-range. "

My thought exactly, Long rods are good for under valved/small port heads allowing more time to fill the cylinder.

My conclusion regarding the crank flex is that the pin is to close to the outside of the flywheel so there is not a lot of strength in that section of the flywheel installing a bigger pin could make make this worst.
Just from my observations and gut feeling. :lol:

Have thought about shorter stroke to increase flywheel strength, with perhaps larger piston 105mm to regain capacity.

Is their an advantage with the single sided swing arm? Looks heavy to me I know is is the fashion statement on a lot of road bikes these days. :roll:

Keep up the good work Dr C

Cheers spanner

Click to expand...

Thanks, Spanner!
I'm currently investigating how the stresses and stiffness change, depending on the parameters you mention. This to see if there is an optimum regarding pin diameter and stroke, within physical limitations of the OEM crank. Advantage of a single sided swing arm? Ah, well... Changing rear wheel and adjusting drive chain tension is done very fast. But most important is the fashion statement! I'm planning to make a taller swing arm in CrMo-tubing, which hopefully will shave off some weight on the rear wheel.
[attachment=0:3rjpxjxv]Crank stress1.png[/attachment:3rjpxjxv]

spanner said:

fdracing said
"moving 1 or 2 mm the cylinder foward help a lot to reduce that wear "

Offsetting the pin in the piston may achieve the same, and easier to do.

Click to expand...

I measured one of my crank cases this afternoon. As far as I can tell, there is an offset by appr. 3mm already. I do not have proper measuring equipment for this, but there is absolutely an off-set.

Shorter stroke will also reduce rod angle.

Malleable Iron would make a good liner, steel is not as ridged.

Agree with fdracing, and nicasil it as well.

Cheers spanner

spanner said:

Shorter stroke will also reduce rod angle.

Malleable Iron would make a good liner, steel is not as ridged.

Agree with fdracing, and nicasil it as well.

Cheers spanner

Click to expand...

I*m planning on using 34CrNiMoS6 material. I don't know the correct English word for it. Maybe "quenched and heat treated"?! That material is in no obvious need of a Nikasil surface.

Using two cranks rotating against each other, will also reduce the side thrust on the piston..

BTW: I have just ordered CrMo-tubes for my frame and swing arm! Lots of things going on in the workshop this winter!

My buddy (mechanical designer) has now run a couple of simulations in Ansys. We have tested different crank pin diameters, different strokes and different press fits. The simulations tells us that:
1. The crank pin (diameter 35 mm) is not the weakest point, causing the OEM crank to spread. Increasing the crank pin diameter will not help the situation much.
2. The holes for the crank pin, in the crank flywheels/cheeks, can not keep the crank pin in place. The general stress in the part outside the crank pin, is not very high, so more material in that region wouldn't either help much. What would help is thicker crank flywheels/cheeks. That would make the holes taller, increase the lever and reduce the surface pressure preventing the crank from loosing control over the crank pin.
3. A tougher press fit would prevent the pin from loosing contact in the "inside" of the crank flywheels/cheeks holes. The crank spread will not be reduced substantially by such an operation.

So where does this leave us? If the goal is to avoid the misalignment causing the main bearings to seize, there are only a few options left. Producing a solid left side with a homogenous crank pin, pressing a right hand side onto it and install another bearing in the "flywheel compartment", might have some success.

interesting...

the pins on the KTM are 35mm x 64mm and the end (in) feed is in the right place as well as of course the one in the middle (out).

and what loadings did you find out about with rod lengths or are those tests next?

If F1 rod lengths are now up to 2.5 x the stroke then that must be because they are running composite rods right? and the extra weight v length is always justified.

surely it's a case of correct ignition timing and longer rod? OK x 1.9 is good but...

Taffy

as you said the weakest point is not the pin itself , but the roller bearing :?

having that power +/- 85 hp at wheel , an 40x50x22 bearing is a good choice , 35 mm works too , maybe not for long time :wink:

Interesting DrC, How much thicker would the flywheels
have to be to make the pin a stable proposition?
Should be plenty of room on the left side to increase thickness, if you are
not using the counter balance.
I think a lot of the bearing problems will be solved form having
the crank halves in line with each other.

You are correct, the crankshaft is offset to the cylinder
by about 7 or 8mm by my rough measurement. Reducing the
rod angle on the compression stroke.
You might like to consider mounting that cylinder head backwards :wink:


Cheers spanner

Re: Sv: Billet cylinder head

We didn't go any further in trying different solutions to cure this problem. Basically I just wanted to find out if a bigger pin would help, and if the crank material "outside" the pin was enough....

This is very off-topic, but my recent work has been in designing a new frame and swing arm. This is to make space for a taller rod... :wink:Any tech-freaks out there might find it amuzing anyway...

Hi Matts

it warms the heart to see 3D software put to use by someone who understands the emotional connection of design to his motorcycle :wink:

has your oneball sport injury healed enough to get some riding in?

FWIW there is an FMX motorcyle "unit skycraft" carbon frame wheels swingarm and a ktm 250 2T engine all up weighs 75kgs, the silencer is the swingarm :twisted:

cheers
Bushie

LOL Bushie welcome back!

Very nice Dr C, wondering if your buddy (mechanical designer) could run an anlasys of single sided swing arm Vs double
sided as to which is stronger for the same given weight?

Cheers spanner

Yeah welcome back Bushie
Thanks for sharing all your amazing work Dr C
Davo.

bushmechanic said:

Hi Matts

it warms the heart to see 3D software put to use by someone who understands the emotional connection of design to his motorcycle :wink:

has your oneball sport injury healed enough to get some riding in?

FWIW there is an FMX motorcyle "unit skycraft" carbon frame wheels swingarm and a ktm 250 2T engine all up weighs 75kgs, the silencer is the swingarm :twisted:

cheers
Bushie

Click to expand...

Aw.. thanks Bushie! I find it very fun and rewarding to fiddle around with CAD! Maybe I should have chosen that line of work instead? It takes a lot of time for me to produce these models, as I have no formal education in this software what so ever!

Yes, I have paid my dues for violating my one ball sport restriction order...

Although I highly appreciate all your efforts in trying to have me develop a carbon fibre itch, I feel the to-do list is tall enough already. :wink:

spanner said:

Very nice Dr C, wondering if your buddy (mechanical designer) could run an anlasys of single sided swing arm Vs double
sided as to which is stronger for the same given weight?

Cheers spanner

Click to expand...

Thanks Spanner! I think there is no need for a fancy multi body simulation tool to prove that a single sided swing arm needs to be heavier than a double dito, to show equal stiffness figures. However, taking the cool factor into account, the decision is eeeeaaaasy. To the boring functionalists I say that tensioning the chain and changing wheels are so much faster with a single sided swing arm.

Davo said:

Thanks for sharing all your amazing work Dr C
Davo.

Click to expand...

Thank you for the kind words, Davo!

DrC, Besides the fact that it appears that something is missing, you will have the
problem of the bike tipping into the corner quicker one way, don`t say I didn`t
warn you 8O

Don`t suppose that design program is open source? ( Free ) 8)

Cheers spanner

spanner said:

DrC, Besides the fact that it appears that something is missing, you will have the
problem of the bike tipping into the corner quicker one way, don`t say I didn`t
warn you 8O

Don`t suppose that design program is open source? ( Free ) 8)

Cheers spanner

Click to expand...

"Lots" of things are still missing in the model, but I was craving for some nice boosting comments from you guys, to man up and complete the work! :wink: Which way do you think it will tip? Into righthanders would have been nice, as nearly all tracks are clockwise.

I'm still evaluating the software... 8)

fdracing said:

as you said the weakest point is not the pin itself , but the roller bearing :?

having that power +/- 85 hp at wheel , an 40x50x22 bearing is a good choice , 35 mm works too , maybe not for long time :wink:

Click to expand...

the problem is that there is not enough metal to support 40mm pin
crankshaft will break
so that's just my opinion

forged 1 piece crank, no problem!