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Crankshaft Balancing

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Cotten

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Location: Central Illinois, USA

Post Sun Nov 28, 2010 8:13 am

Re: Crankshaft Balancing

My turn.

The pistons dipping into pooled oil would not be all that desireable in a running motor.
But as soon as the motor is started, that pooled oil is probably dispersed pretty damn fast, so my guess is that it was intended to be a benefit for initial start-up, when need for lubricaton is most critical. (Just as the felts in Pans served as a reservoir to keep the rockers wet.)

Indian's baffles were different, in that the front was intended to scrape oil windage off of the wheels, and had small holes to aspirate oil upward with the rise of the piston. So basically the baffles shielded the rear and favored the front. Since the windage from the wheels floods the rear, but has diminished by the time it reaches the front, it makes sense.
WINDAGE.jpg
Plexiglas box around 101 flywheel on lathe to observe windage spray of oil from below.
WINDAGE.jpg (104.09 KiB) Viewed 4474 times

I do not endorse removal of baffles, unless they are just too badly cracked.
They provide a substantial stiffening effect for the case. Note how H-D substantially beefed up their left cases after baffles were eliminated.

And now back to Cooky's first question about balancing "specs":
The only thing that could be called a useful spec would be the balance factor, which is totally arbitrary. But you will find most folks declaring 60% carved-in-granite for a post-36 Harley Big Twin, whether they understand motor balancing or not.
The Factory undoubtedly chose a lower factor, but only by back-calculating with original rods and pistons, etc., would I guess as to what it was.

....Cotten
Last edited by Cotten on Sun Nov 28, 2010 8:27 am, edited 1 time in total.
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Frankenstein

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Post Sun Nov 28, 2010 8:26 am

Re: Crankshaft Balancing

Chris, you misunderstood me, in that I don't agree with the "metered dip" theory. I was tactfully trying to point that out with:

"As for one theory of the narrow slot created by the baffles creating a vacuum to help lubricate cylinders/pistions, I offer these thoughts. Ever pull the timing plug on a running harley? Get a little oil mist in your face? Right. Inside those crankcases it's a hurricane confined. Oil is being flung from the only source, the rod journals, radially, in all directions, including up at the bores. No extra inducement is needed to get it there."
That indeed there is violent, turbulent, airflow within the crankcases and there would not be any calm pools of oil waiting to be dipped in. However, I've never seen the goings on within the crankcase, and until they build the plexiglass ones, I don't think anyone else has either.
As I stated, my original source for my theory is from an old harley mechanic, much like you.
I wish to leave it that we agree to disagree. You won't convince me, and I probably won't convince you. :D

DAMN Cotten, I take it back about the Plexiglass cases!!! You posted while I was typing. But, those still don't take into account the air movements induced by piston travel. Could you maybe add a couple of PVC pipes, rods and pistons?
:lol: :lol:

DD
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Chris Haynes

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Joined: Wed Jul 05, 2000 12:01 am

Location: Los Angeles, CA

Post Sun Nov 28, 2010 7:59 pm

Re: Crankshaft Balancing

[quote="panic"]I've found that attempting to 'explain" something to a person who is waiting to criticize anything I say, and who wouldn't understand the comment anyway is a waste of everyone's time.
It it what it is, whether you understand it or not. It doesn't depend on whether I convince you.

[quote]


Darn Panic,
I must have missed the part where you tried to explain this. All I saw was your criticism and trying to belittle me..
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Pa

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Post Sun Nov 28, 2010 8:04 pm

Re: Crankshaft Balancing

OK Chris....enough is enough. Continuious mud slinging is only gonna invite more of it. let it go now.
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Chris Haynes

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Post Sun Nov 28, 2010 8:51 pm

Re: Crankshaft Balancing

PA,
I am not slinging any mud. I tried to give an answer to a question and I was attacked. I am not a highly educated man. I have attended the school of hard knocks. I listen to people with first hand experience and try to remember what they tell me. But one person here seems to have made it his life's ambition to criticize any post I make. That sir, is not me slinging mud.
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jib

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Location: devon,england

Post Mon Nov 29, 2010 4:03 am

Re: Crankshaft Balancing

cotten ,after you have made the perspex conrods and pistons etc could you add scrapers please i have been thinking of knife edgeing my wheels ,but am not sure if they will still deposit oil in the same way

if you had a set of wheels could you try it for me please i'm sure loots of people would be interested in your findings.

regards jib :)
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years
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Cotten

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Post Mon Nov 29, 2010 6:45 am

Re: Crankshaft Balancing

Jib!

I'm afraid my motor studies were shelved long ago to concentrate upon carbs,
and I would rather do my best to talk you out of mutilating your flywheels anyway...
Unless by "knife-edge" you meant this:
knifedge.jpg
knifedge.jpg (53.82 KiB) Viewed 4355 times

You can see in the plexiglas box photo that the oil sprays off of the sides of the wheel to make two lines of oil across the top of the box. Two wheels would make four streams, of course, with the inboard two being the ones that come closest to the gap between baffles. The amount of oil is determined by how much oil is pooled in the bottom of the cases.
A flywheel shaved to a single edge would pick up much less oil, and spray its single stream at the middle of the baffle.

It should be noted that the oil that gets sprayed directly between the baffles comes from the crankpin itself, and evacuating the pooling oil in the sump is the priority, not splashing it back up again. Flwheels cut to a point would not feed the "scraper" very well at all, and normal pump feed would soon flood the sump.

And DD!
I would love to have nothing better to do than build a complete see-through motor, but a damn Linkert bowl must come first.

....Cotten
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jib

Posts: 570

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Location: devon,england

Post Mon Nov 29, 2010 8:44 am

Re: Crankshaft Balancing

cotten your answer was kind of what i thought would happen although i have been toying with the idea of adding a 'sump to the casings sometime in the future.

i guess i will have to put off mutilating my wheels till i have worked out a viable system.for returning the oil from the sump as gear oil pumps are poor suckers

buell wheels are knife edged probably for the very reason its not a good idea to do a 45 set .i.e so that they dont pick up oil.

i wont be having baffles in the motor and will be using k pistons and kh barrels (4 5/8 stroke) . as the k model didnt use baffles and thats what im going to emulate, thought best to remove them.

had never considered the case stiffness to be a problem as at that point the cases are firmly clamped by the barrels, a thought to bear in mind.

regards jib
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years
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COOKY6660

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Joined: Mon Mar 09, 2009 3:55 pm

Post Mon Nov 29, 2010 12:36 pm

Re: Crankshaft Balancing

Thanks for all your quotes and answers on my baffle question. So, on my cases only one baffle plate is left, would this cause any problems with the motor? Again your help would be very much appreciated
regards
cooky
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jib

Posts: 570

Joined: Sat Dec 10, 2005 3:36 pm

Location: devon,england

Post Mon Nov 29, 2010 12:48 pm

Re: Crankshaft Balancing

cooky,
37 - 38 both crankcase mouths had baffles on the bigtwin sidevalve cases.
39 and later only the front had a baffle and the conrod was the male one, the female or forked rod being used on the rear cylinder.
hope this helps regards jib
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years
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Pa

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Location: Ohio USA

Post Mon Nov 29, 2010 1:38 pm

Re: Crankshaft Balancing

Chris Haynes wrote:PA,
I am not slinging any mud. I tried to give an answer to a question and I was attacked. I am not a highly educated man. I have attended the school of hard knocks. I listen to people with first hand experience and try to remember what they tell me. But one person here seems to have made it his life's ambition to criticize any post I make. That sir, is not me slinging mud.


Sorry Chris...I did not mean to suggest your last comment was mud slinging. I meant anymore conversation on the bashing would entice more mud slinging. Preferably I should have just said "stop it", "drop it", "quit it", or "move on"....

IMHO....there are two types of educated people. Those who wish to learn more and those who think they know it all. It doesn't matter what schools they attended, what degrees they hold, what skills they possess, what trade they are in, or what position in society they sit in. If they permit their ego to swell, as to have placed themselves high up on an imaginary throne. so as to look down upon others, they wasted the time and efforts of the educators.
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MarkBranst

Posts: 341

Joined: Thu Jun 24, 2004 12:01 am

Location: Champaign-Urbana, IL

Post Mon Nov 29, 2010 2:50 pm

Re: Crankshaft Balancing

jib,

"He that shall not be named" suggested that Mississippi tried to legislate that pi=4 ... I came up with a different source for this story, but it is still interesting:

http://tinyurl.com/bta9ta

Regards, Mark
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jib

Posts: 570

Joined: Sat Dec 10, 2005 3:36 pm

Location: devon,england

Post Mon Nov 29, 2010 3:04 pm

Re: Crankshaft Balancing

cheers mark
quite a funny read , strange lot in Indiana ,i would imagine at the turn of the19th century. gonna book mark the site and see what other boosh cecil deals with. :D :D

regards jib
Dude, check out that jibhead, he's crazy. Hasn't been sober for 40 years
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Pa

Site Admin

Posts: 4656

Joined: Sun Mar 12, 2000 1:01 am

Location: Ohio USA

Post Mon Nov 29, 2010 4:51 pm

Re: Crankshaft Balancing

I am really hooked on the idea of a transparent engine assembly. I have a spare set of cases which would make an ideal set of casting cores. I'm going to look into have the foundry see what they can do with forming molds and casting transparent cases from them. They will know what transparent material we will need as well. Keep your fingers crossed I can gain some interest. I do have very good friends in the foundry business and many in the machine trades. It will take time though. Along the way, we will need to come up with suggestions on how to cut the possible transparent cases into sections. we will need them so they can be modified with additional sections as we test out the lube circulation. We can start with stock engineering and proceed from there. Pa
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Chris Haynes

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Joined: Wed Jul 05, 2000 12:01 am

Location: Los Angeles, CA

Post Mon Nov 29, 2010 9:22 pm

Re: Crankshaft Balancing

They had clear aluminum in a Star Trek movie. Just wait a few years and it will be available. Everything else from them is coming to the market or is already here. :D
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Beachdog

Posts: 765

Joined: Mon Oct 16, 2000 12:01 am

Location: CA USA

Post Tue Nov 30, 2010 8:41 am

Re: Crankshaft Balancing

I've watched this discussion with interest. Over the years I've heard many explainations from oldtime builders about the baffles. All different. My observations are that there is a lot of stuff flying around in that bottom end as a pulled timing plug illustrates. Dipping a piston skirt into a pool of oil probably doesn't happen as the oil drains into the rod opening and to dip, the piston would have to come too close to the baffle for my comfort. I'm pulling down a UL with baffles so I will test this clearance theory if it has HD pistons in it. Over the years I have built many race engines with various baffle arrangements in them. No baffles, one half baffle, both baffles drilled like swiss cheese and full baffles. The one thing they all had in common was that they all ran well. I suspect that the loose piston setup in the race specs helps to account for this. The later K/KH model was set up a little tighter and was intended for street use in competition with the Brit twins so it got the piston lube in place of the baffles in the interest of longevity. Anyone who has pushed a KH hard on a hot summer day knows that unlike the UL you are never worried about it getting tight. So, instead of snapping the throttle closed every so often like the oldtimers taught us to do on the UL you just ride without care. My two cents from an uneducated grease monkey.
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Lee W

Posts: 137

Joined: Sat Sep 23, 2006 8:58 pm

Location: Carver, MN

Post Tue Nov 30, 2010 1:19 pm

Re: Crankshaft Balancing

Maybe I misread some comments here, and I am not going to spend the time to go back and see if I did or not, but I just want to add this. It seems that there is a common misconception that there is a quantity of oil in the bottom of the cases that the flywheels run through. This would only be true on initial start up. From there on, the oil is being carried around with the flywheels. Like I said, maybe I misread someone's comments, or maybe I am the one with the misconception, but I thought I would throw it out there.

As to flywheel balance, here are the balance factors used in production (from a factory service school back when I was much younger)
FL 1340 - 60%
FL 1200 & Pan - 50%
XL 883 - 62%
XL 1100 - 69%
XL1200 - 63%
XR 750 - 55%
XL 1000 - 62%
While that doesn't really answer anyone's question, it does provide food for thought.
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X-WLCH

Posts: 111

Joined: Wed Apr 30, 2008 12:16 pm

Post Mon Jan 24, 2011 6:41 pm

Re: Crankshaft Balancing

Has anybody actualy built an engine with a balance factor lower than 50% ? What was it, and at what rpm did it run smooth? I would be interested to know the highest and lowest factors that anyone has actual experance with and how did they act? Is lower better for light engines at high rpm ? I have never heard of a bad balance factor but i suspect that there is a point of too far, with all the experienceters out there looking for the altamite, someone reading this has probably found it.
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Cotten

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Location: Central Illinois, USA

Post Tue Jan 25, 2011 6:56 am

Re: Crankshaft Balancing

X-WLCH wrote:Has anybody actualy built an engine with a balance factor lower than 50% ? What was it, and at what rpm did it run smooth? I would be interested to know the highest and lowest factors that anyone has actual experance with and how did they act? Is lower better for light engines at high rpm ? I have never heard of a bad balance factor but i suspect that there is a point of too far, with all the experienceters out there looking for the altamite, someone reading this has probably found it.


X-WLCH!

VLs were down around 43%, from what I have read. (Late correction after finding a handwritten note from Mr. Slocombe: 46%) The reason being the different frame.

A single-throw V-twin cannot be out of balance. It can only be poorly balanced for a particular application.

These motors 'run smooth' over an enormously wide range of factors. If a motor does not run smooth, something mechanical is amiss!

Balancing is for the motor's benefit, not the rider's.

....Cotten
Last edited by Cotten on Fri Jan 28, 2011 6:56 pm, edited 1 time in total.
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Sidewinder

Posts: 89

Joined: Tue Dec 25, 2007 4:04 pm

Location: Norway

Post Tue Jan 25, 2011 2:01 pm

Re: Crankshaft Balancing

When I run my U the first year it was running smooth only on low rpm. I seamed to pull happily up hills in high gear and low rpm. In highway-speeds it was not smooth. The vibrations where so bad that my boots kept sliding of the footboards. The two front tubes actually cracket above the sidecar loops under previous ownership. And I kept loosing nuts and bolts. The balance factor was lower than 50% with aftermarket pistons (cant remember the exact figure anymore).

During rebuild the flywheels where rebalanced to 55%. No change in cylinder/top end/cams during rebuild. The motor now runs smooth at any rpm you dare to take her to. Maybe a litle bit less smooth at very low rpm than the previous setup. And I have not retightened a singel nut in 10 seasons now (and no nylock or tread locker anywhere).

This is my experience, not a scientific evaluation. Might be some factor I have not taken in concideration. But I think it is safe to say that the higher balance factor had no bad effects on my motor.
Torstein
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