TRNorBRN6001
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Posts: 2021
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posted August 06, 2008 07:48 AM
Crank and Rod Bearing Clearance
Curious what most say a good general race clearance is for main and then rod bearings. I have seen some differences between individuals. Also curious if and how oil pressure is taken into acount with regard to running clearances? Also curious when running a fairly stronger hit of nitrous if a different rod clearance should be taken into account?
The application would be for a stroker Hayabusa motor with the larger Honda BlackBird rod bearing size. I have unfortunetly just found out that Honda does not list the actual bearing size and only goes by the color/letter, so I'll be ordering a few extra and doing a bit of measuring. Go figure, how would you know if they were accidently miss labeled.
Thanks you all,
Gary
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zrexpilot
Expert Class
Posts: 470
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posted August 06, 2008 09:40 AM
were going to give a bit more clearance on the bearings on my motor. The theory is with more hp the the rods will want to squish out the oil.
I want to see what others say, I was going to ask the same question.
You should see the difference between the 12 rods and the busas. The 12 are much much stronger, crank is even heavier on the 12,
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VincentHill
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posted August 06, 2008 09:42 AM
Dr. Gary, First, remember that as the Rod is accelerated the Oil in the journal is at the Bottom of the rod but just beforeTDC When the the full Hit of the explosion is getting ready to take place, the Crank stops Accelerating but the Rod continues! This causes the rod to Squish the Oil at the Bottom like a Big Cushion and force it on top of the Journal giving a new Cushion for the explosion for the rod to ride against the Journal on the way down! \
The only problem is when the Oil pump is ported and there is No Oil supply for a milisecond and there is no cushion for the Rod and Journal and they "Touch" each other!!
Bigger clearance needs Higher Oil pressure for the larger amount of Oil needed and the faster leakage out the sides!
I said all of this to say that I would NOT Increase the Clearance and this is why thinner Oil with the smaller Molecules offer less protection as in your Zero Weight Oils!
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zrexpilot
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Posts: 470
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posted August 06, 2008 09:52 AM
and yes we will be upping the oil pressure and running an oil pressure guage.
But in all reality what are we talking about , 5 hundred thousanths ?
0.0005 to maybe .0010, That is not much.
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TRNorBRN6001
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Posts: 2021
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posted August 06, 2008 11:09 AM
Thank you Mr. Hill that helps explain what I was thinking about. Yep, ZRex it's not much, but I'd bet there in lyes a small portion to some build secrets. No worries Mr. Hill I'll make sure it has oil in it even with more volume/pressure. I think it's a generation thing, but I do not like the low weight oil either.
For those who have run coated bearings do you run a little tighter clearance as the coat people say is possible or do you take the amount of coating into full consideration.
Annoyingly my mains are tending to want to run a little loose and my rods a little on the tight side. Guess when your on a little bit of a budget you just have to put up with certain things.
You would be proud of me Mr. Hill, I have gone over to the DarkSide and will be running CP Pistons for this build. Should have them in a couple days and then send them off with the block. Don't worry I'll have them smooth that old tired block out a little while their at it.
Gary
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VincentHill
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posted August 06, 2008 11:32 AM
Dr Gary, I know that Dan is not afraid to use 20 weight but anything less than 30 weight scares me! Short story I have told is how I put the thrust washer behind the Clutch Basket in "BACKWARD" so that it was rubbing the Input Shaft Bearing race. I must have had it this way for at least a year using Moutl E-Tech 100. Then when I went to the NOS Pistons and broke them in for about 50 Miles with ND30 Oil (SA - A Rated Oil) when I drained the oil I saw pieces of Steel and metal Shards. I took the engine apart and saw that I was blueing the bearing and was trying to weld the washer to the Bearing race.
I took the bottom end apart and replaced the Bearing and put it all back together and no problems (Also cleaned the Screen). To me, this showed me just how good the Motul was and whi i was using Junk Oil for a few miles to allow the rings to seat!
After the 50 miles I then iuse the Cheapest Motorcycle Oil I can find (Usually Honda Oil) for about 500 Miles and ring the Hell0 out of it for VERY Short periods off time to really seat the rings. I am still not able to put the pistons in the Cylinders DRY or with 1 drop of oil on each Skirt yet!
You will find that the CP Pistons have better Rings and sealing along with lighter but more Meat where you need it than some other brands of Pistons! Y2K and I were discussing rings and between what he said and what I think, I believe the rings are the reason most big bore kits do not make much more HP than stock. If the circlips grooves do not have a small notch to pry them out, make one with a dremmel tool so that you can get under the circlip to install or remove it!
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tcchin
Zone Head
Posts: 867
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posted August 06, 2008 11:43 AM
FYI, .0005 to .0010 is a five ten-thousandths change.
I agree with most of what Mr. Hill says, except that the velocity of the piston is sinusoidal, meaning that the rod is decelerating for the last 90* BTDC. Also note that the geometry of the oil wedge, which is defined by the load vector and the relative radii of the bearing and the crank journal, will have a significant effect on the thermal and bearing loads applied to the oil. Using tighter clearances not only reduces lateral leakage rates, it also allows for more load distribution across the oil wedge, and for more gradual thermal/viscosity gradients.
The OEM engineers have spent a lot of time designing these motors, so I wouldn't stray too far from the recommended parameters. If you're using CBR bearings, use CBR clearances.
Finally, I measure every bearing every time so I know if a bearing is out of spec. Never trust the paint codes, as they are often wrong.
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zrexpilot
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posted August 06, 2008 12:07 PM
quote:
FYI, .0005 to .0010 is a five ten-thousandths change.
yep missed a zero.
.00005-.00010
isnt this around what people run if they were to open it up some, or even less ?
like 1or 2 one hundred thousands
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NOX
Needs a job
PMRA / TMRC Super Street 4022
Posts: 3745
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posted August 06, 2008 01:54 PM
Depnds on what oil you want to run as well.........
zrex......, you have a late model......, you can use your flywheel on a 2001 crank, and loose 3 lbs. Thats what I did. Problem was I added 15 lbs to the bike, so it equaled out in et.
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tcchin
Zone Head
Posts: 867
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posted August 06, 2008 03:14 PM
quote:
isnt this around what people run if they were to open it up some, or even less ?
like 1or 2 one hundred thousands
I don't know if I understand your question. Where would you run .00001" clearance?
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entropy
Moderator
Posts: 8671
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posted August 07, 2008 03:03 AM
quote:
Finally, I measure every bearing every time so I know if a bearing is out of spec. Never trust the paint codes, as they are often wrong.
big 10-4 to being careful on what size the shells really are.
I just sent a couple sets of rod shells to WPC, luckily i had several extras laying around.
2 of the supposedly brown shells, were assuredly in the black range.
Now, when i order a set of rod shells, i order 10, not 8...
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NOX
Needs a job
PMRA / TMRC Super Street 4022
Posts: 3745
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posted August 07, 2008 05:57 AM
Ditto that. Luckily, all my browns were browns on my build.
____________
42 Wins
21 Runner-ups
2010 TMRC Super Street Points Champion
2010 PMRA Super Street #3 Points
2009 PMRA Super Street Points Runner-Up
6 Time Centerville Dragway Points Champion
Sponsored by:
Scorpion Helmets
Galfer Braking
AMSOIL
Steve's Speed Shop
Kawasaki Sports Center
Mickey Thompson Tires
Catalyst Racing Composites
Conway Cycle
Syed Leathers
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VincentHill
Needs a life
Posts: 6520
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posted August 07, 2008 08:26 AM
quote:
FYI, .0005 to .0010 is a five ten-thousandths change.
I agree with most of what Mr. Hill says, except that the velocity of the piston is sinusoidal, meaning that the rod is decelerating for the last 90* BTDC. Also note that the geometry of the oil wedge, which is defined by the load vector and the relative radii of the bearing and the crank journal, will have a significant effect on the thermal and bearing loads applied to the oil. Using tighter clearances not only reduces lateral leakage rates, it also allows for more load distribution across the oil wedge, and for more gradual thermal/viscosity gradients.
The OEM engineers have spent a lot of time designing these motors, so I wouldn't stray too far from the recommended parameters. If you're using CBR bearings, use CBR clearances.
Finally, I measure every bearing every time so I know if a bearing is out of spec. Never trust the paint codes, as they are often wrong.
Good Stuff loose is not always better because of the Rocking forces that can push the wedge from side to side! (per my conversation with Kevin Cameron
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Made History @ Daytona and still one fast old man!!
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