Question regarding Superquadro engine

mi2jaca · Nov 19, 2019

Hi,
I have a technical question regarding the design of the Ducati Superquadro engine and it goes like this:

How is the crankshaft axial end play (float) controlled in these engines? I see no mentioning of thrust bearings or any way of checking/adjusting end play in the workshop manuals. With roller/ball bearings you are always so concerned about crankshaft endplay but when you are running plain bearings like in the Superquadro that is not a problem?

Please enlighten me.

Best regards,
//Carl

airjawed · Nov 20, 2019

In a modern engine the manufacturing tolerances are very strict. You can measure it but on the MV Agusta F3 800 for example there didn't seem to be a way to adjust it. If it was not in spec then you needed a new engine case.

mi2jaca · Nov 21, 2019

Thanks for the reply!

On the MV where did you measure the end play? Was there a thrust bearing?

On the Superquadro engine I can find no such features so what is actually controlling the end play? Is the crankshaft rubbing against the crankcase directly?

airjawed · Nov 22, 2019

I don't think any modern motorcycle uses thrust bearings. They use plain bearings vs roller bearings. The "bearing" works by oil pressure and very exact tolerances. The plain bearing sits in a groove on the crankshaft and is kept from lateral movement by its tolerance and separated by oil. The plain bearing is held into the engine case and it is not lubricated.

Oil does all the work with the cooperation of tolerances . The piston uses oil to keep it from rubbing against the cylinder walls. Oil also does the work between the piston and connecting rods. Even the connecting rod does not use a 'roller style bearing'.

Basically the entire crankshaft assembly floats on oil.

mi2jaca · Nov 24, 2019

I understand that the crank "floats" on oil but what is keeping it from moving from side to side and rubbing against the crankcase?

Plenty of modern motorcycles use thrust bearings for example the Yamaha R1 and the BMW S1000RR to prevent this from happening.

alvarocca · May 18, 2020

mi2jaca said:
I understand that the crank "floats" on oil but what is keeping it from moving from side to side and rubbing against the crankcase?

Plenty of modern motorcycles use thrust bearings for example the Yamaha R1 and the BMW S1000RR to prevent this from happening.

did you find the answer to this question? Im rebuilding an 1199 engine and have the same play... its normal?
i think the oil presure that cames from one of the sides of the crankshaft push it to one side??? im asuming..not saying...

DesmoAndrew · Aug 27, 2020

well, I went the 1199 service manual that I have and, sure enough, no spec for crankshaft end play. Presume they can hold the tolerances close enough to get some degree of centering based on oil film from the oil coming out of the crank main bearings.

And speculating here ... given that we dont have the angular contact bearings of the previous engines, we dont need a prescribed amount of preload. Since the rods do float a bit on the crank and the rods also float a bit within the pistons, a slight amount of side to side motion with the cases isnt an issue. The main drive gears are straight cut so there isnt any side thrust produced. It may well be that modern manufacturing tolerances can be held to where it is needed. Ducati still do offer difference classes of cranks and rod bearings so as to obtain the required oil clearance there.

Question regarding Superquadro engine

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