Single Cylinder Crankshaft Oil Drilling

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Mudflap
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Re: Single Cylinder Crankshaft Oil Drilling

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coseng wrote:
Thu Dec 19, 2019 10:17 pm
I may stick with one hole in the rod initially. 12krpm is not that high a crank speed that I would have to solve problems that Ducati didn't.
I agree, I don't think you have to.
coseng wrote:
Thu Dec 19, 2019 10:17 pm
I thought you were talking crank material stress levels. I was planning on using the OEM Ducati bearings for both the mains and rod. The mains may be a bit oversize but that is better than too small. If it becomes an issue, the bearing width can be narrowed a bit and still be over D/L 0.25.
Actually any increase in clearance from nominal will certainly lead to a decrease in bearing load capacity. I strongly suggest using whatever clearance the OEM engine was designed with.

I apologize - L/D should be 0.25, not D/L! My brain was switched off. I'll edit previous posts.
How much TQ does it make though?

coseng
coseng
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Re: Single Cylinder Crankshaft Oil Drilling

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Yes, sticking with OEM design wherever it makes sense to.

For anyone interested, I will be documenting most of the build on Instagram under the hashtag #hypermono
Chris
Cosentino Engineering
www.cosentinoengineering.com

Tommy Cookers
Tommy Cookers
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Re: Single Cylinder Crankshaft Oil Drilling

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coseng wrote:
Wed Dec 11, 2019 1:15 am
.... I'm getting into my 3rd custom single cylinder roadrace motorcycle design ....
.... I've done head/crankcase transplants before with good power .....
did/do you use (or lose) counterbalance shafts ?

iirc no 4 stroke single design over 223 cc without such shafts has been introduced since 1979 (the SR 500)

J.A.W.
J.A.W.
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Re: Single Cylinder Crankshaft Oil Drilling

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Tommy Cookers wrote:
Wed Jan 01, 2020 7:50 pm
coseng wrote:
Wed Dec 11, 2019 1:15 am
.... I'm getting into my 3rd custom single cylinder roadrace motorcycle design ....
.... I've done head/crankcase transplants before with good power .....
did/do you use (or lose) counterbalance shafts ?

iirc no 4 stroke single design over 223 cc without such shafts has been introduced since 1979 (the SR 500)
Indeed T-C, a powerful BMEP big single will pump out quite a spike, 'torsional excitation' wise,
& with that stress vectored via components designed for a 90 degree twin, perhaps problematically?

http://epi-eng.com/piston_engine_techno ... ngines.htm

Historically Daimler-Benz, & later Yamaha*, Kawasaki, & Ducati too, all had problems with their
transitions from rolling-element bearing-to-plain bearing crankshaft designs, even when in service.

*The Yamaha TX 750 was an early`70s 360 degree 4T twin which did incorporate a balance shaft
to quell its 'torsional excitation' vibes, but ran afoul of tribological issues such as excess oil-frothing
causing problems with lubrication functions - (as had Daimler-Benz, earlier) which were an unforseen
result of the vastly increased quantity/pressure of oil being pumped - as demanded by plain bearings.
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

coseng
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Re: Single Cylinder Crankshaft Oil Drilling

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>>did/do you use (or lose) counterbalance shafts ?

There will be a balance shaft in my new crankcases. With a large displacement single, if you want a happy rider a balance shaft is pretty much a requirement.

With the short length and large diameter crank bearing journals, I don't expect any torsional vibration issues. A balance shaft would not assist in damping torsional vibrations, you would want a torsional damper for that. Balance shafts are for reducing the forces generated by rotation of unbalanced mass.

I thought the TX750's oil frothing problem was due to locating a balance shaft in the sump area.
Chris
Cosentino Engineering
www.cosentinoengineering.com

J.A.W.
J.A.W.
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Joined: Mon Sep 01, 2014 4:10 am
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Re: Single Cylinder Crankshaft Oil Drilling

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A single cylinder 4T design necessarily puts dynamic stress of many types on its big-end.

The Yamaha TX 750 did feature a pair of balance shafts, & a dry-sump design,
but it also suffered from both crankcase ventilation & over-heating issues,
(along with its various internal chain runs whipping the oil around excessively),
so the oil-pump complex could not cope with this combination of tribological
factors, & failed to supply the plain bearing crankshaft with lubricant, as needed.

Yamaha attempted to ameliorate these issues with a redesign of the balancer
set up & oil pump, (along with a bolt on 'wet sump' addition) plus an oil-cooler.
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

coseng
coseng
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Location: Jersey City, NJ

Re: Single Cylinder Crankshaft Oil Drilling

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After getting more of this engine apart it looks like Ducati feed both crank main bearings from one end of the crank.

This means that the oil is pumped in at center axis of the crank then out to the the larger radius of the conrod throw then back to a smaller radius for the second main bearing. Seeing how much radial distance they come back for the second main bearing I am not concerned about the smaller amount that I am going in my design to feed one conrod.
Chris
Cosentino Engineering
www.cosentinoengineering.com

J.A.W.
J.A.W.
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Joined: Mon Sep 01, 2014 4:10 am
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Re: Single Cylinder Crankshaft Oil Drilling

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Hi Chris, have you had the opportunity to examine a hard-run bearing shell from
any donor-like Ducati's big-end bearing, or seen any calc's on relative dynamic forces
per potential usage as a single?

AFAIR, this was one of the reasons Ducati went down the complex 'super-mono' faux-twin
route, & also why BMW also did such a dynamic solution with their current 360 degree twin.

Likewise, one of the issues with Cosworth's DFV 1/4 cut for the Norton F750, back in the day,
was the massive crankcases required to contain the recip-forces, counter-balancers or no..
Dr Moreau sez..
"Who breaks the law... goes back to the House of Pain!"

Tommy Cookers
Tommy Cookers
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Joined: Fri Feb 17, 2012 3:55 pm

Re: Single Cylinder Crankshaft Oil Drilling

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good point ....
however ....

there is anyway counterbalancing in the crankshaft .... this subtracting from the notional (otherwise unbalanced) inertia force
eg in the simple single etc
max 'primary' inertial force is (with balance factor of 50%) 50% of NPIF ...
max 'secondary' inertial force is 25% of the NPIF .... so ....
max combined PIF+SIF approaches 75% of the NPIF (at tdc)

in a 90 deg V ....
the max SIF reaches at midstroke 36% of the NPIF ... and ...
this notional PIF's has moment effects which aren't cancelled within the crankshaft (though the forces are) ....
as the rods aren't co-planar (plus the balance factor is 100%) ....in reality ....
each main bearing sees a significant fraction of NPIF adding to the SIF's magnitude of 36% NPIF as above

coseng
coseng
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Re: Single Cylinder Crankshaft Oil Drilling

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>>have you had the opportunity to examine a hard-run bearing shell from any donor-like Ducati's big-end bearing, or seen any calc's on relative dynamic forces per potential usage as a single?

I'm not sure why a big end bearing would know how many other cylinders there are. I could make a V8 with the same dimensions and each conrod would see the same loading as the twin, or single. I have run simulations to confirm there should be no problems with bearing loads.

>>AFAIR, this was one of the reasons Ducati went down the complex 'super-mono' faux-twin route

The Supermono was a student design project by Terblanche (who unfortunately peaked early) and was anything but complex. Not to kill a legend but the balance rod idea is nice but was making lemonade with lemons as he had to reuse existing parts and patterns. A 90 degree twin has zero primary vibes and the SM engine mimics the twin's primary balance characteristics. The secondary vibes of a twin and the SM are the same and each conrod big end (there are still 2 in the SM) add up using vector addition (45, 45, 90 triangle) so the magnitude is 1.414 (1, 1, Sqrt 2) the size of one cylinder’s secondary vibration and twins usually have short-ish rods so high secondary vibes. The Duc rod is a 1.85 ratio giving a combined secondary vibration magnitude of about 38%. For a single with a counterbalance shaft you also have zero primary vibes. For the secondaries I am using a long rod (~2.2 ratio) for lower secondary vibes and since there is only one cylinder it is 1 times those lower vibes, which comes out to a vibration magnitude of 22.7%. So overall a counterbalance shaft with a long rod in a single will have about half the vibration levels of a well-balanced twin or single/balance rod. And have a more compact engine design.

https://motochassis.com/Articles/Engine ... alance.pdf

>>BMW also did such a dynamic solution with their current 360 degree twin

The balance rod here is dynamically very different, it has its own throw which is less than the stroke. Leave it to the Germans to solve a problems uging twice the complexity as everyone else.

>>Likewise, one of the issues with Cosworth's DFV 1/4 cut for the Norton F750, back in the day, was the massive crankcases required to contain the recip-forces, counter-balancers or no

That was the Norton Challenge and the crank was not much different than their other parallel twins. There is one about 50ft from where I am sitting. Let the engine hover around 3krpm too long and the cam belt jumps a tooth. I think it had about 70lbs of internal rotating weight.
Chris
Cosentino Engineering
www.cosentinoengineering.com

Steve
Steve
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Re: Single Cylinder Crankshaft Oil Drilling

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First time on the forum and I stumbled across this thread. I am working on a prototype engine design and there is a shaft that has very high thrust load. I would like to use plain bearings for both the rotation and the thrust. It appears some here are very knowledgable on bearing design. Could anyone direct me to where I might find basic plain bearing design principles to start educating myself.

coseng
coseng
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Location: Jersey City, NJ

Re: Single Cylinder Crankshaft Oil Drilling

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>>Could anyone direct me to where I might find basic plain bearing design principles to start educating myself.

This could be a start: https://www.nationalbronze.com/Tribolog ... ition).pdf

For my project, I am using the OEM bearings so not much bearing design went on, just a reuse.
Chris
Cosentino Engineering
www.cosentinoengineering.com

Steve
Steve
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Joined: Sat Jan 04, 2020 3:54 pm

Re: Single Cylinder Crankshaft Oil Drilling

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Chris, thanks for the link. This will help me to begin to understand the principles.

coseng
coseng
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Re: Single Cylinder Crankshaft Oil Drilling

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Hey Mudflap,

For a big end fed from the main bearing journal I've seen the Japanese bike manufacturers put a groove in the upper bearing half. Do you think this is sufficient feed? What happens for the other 180 of crank rotation that the rod hole is not fed by the groove? I have enough width in the bearing face available to have two thin bearings (with same overall width as the original single bearing) spaced apart by .2 or so to have a full circumference groove for full-time conrod feeding.

Thanks,

Chris
Chris
Cosentino Engineering
www.cosentinoengineering.com

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Mudflap
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Re: Single Cylinder Crankshaft Oil Drilling

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Hi Chris,

Normally the bottom half of the main bearing is the highest loaded so you don't want a groove there (it reduces projected area which increases pressure).

180 deg in the upper main is more than enough for the rod bearing. It is not unusual to have a groove of less than 180 deg such that it stops just short of the crush relieves. This way oil is prevented from flowing right out of the bearing through the relief and that can add up to a significant oil pump capacity reduction on multi cylinder engines.
How much TQ does it make though?