Author Topic: engine balance - how to  (Read 11895 times)

mike90045

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engine balance - how to
« on: July 25, 2007, 03:42:51 AM »
newbie here - I can pull start a lawnmower.  (also  took a 2 cycle engine apart, to clean grit out of it, and it still runs, 13 years later)

Is there a reason the head can't be pulled, and then spin the engine up to see if it's in gross balance ?
   (hand crank, or motor drive)

if it wobbles around, do weights need to be added to the crank, or either/both flywheels

I suppose if it wobbles, and a chalk mark is successfully made, the weight gets added opposite the chalk ?


phaedrus

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Re: engine balance - how to
« Reply #1 on: July 25, 2007, 11:37:31 AM »
George's utterpower CD has, as I recall, a good piece on balancing these engines. However if they are not terribly out proper mounting to a massive foundation may be enough. It's desirable in any case too.
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mike90045

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Re: engine balance - how to
« Reply #2 on: July 25, 2007, 01:03:44 PM »
George's utterpower CD has, as I recall, a good piece on balancing these engines. However if they are not terribly out proper mounting to a massive foundation may be enough. It's desirable in any case too.
I have the CD, but

1) it does not cover the thought I had about removing the head, so the engine will coast freely (or will the decompression valve do that 100%) ?

2) are flywheels even enough to do the chalk marking - if it has a lump, won't the lump get marked as heavy (maybe it is)

3) I'm wanting to do this before starting a new (and unbought) engine, and want to gather up ideas.

xyzer

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Re: engine balance - how to
« Reply #3 on: July 25, 2007, 01:25:45 PM »
Mike,
What engine are you trying to balance?
Dave
Vidhata 6/1 portable
Power Solutions portable 6/1
Z482 KUBOTA

mike90045

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Re: engine balance - how to
« Reply #4 on: July 25, 2007, 03:34:19 PM »
Mike,
What engine are you trying to balance?
Dave

The one I get before the end of the year.   I suspect it's going to be a 8/1  clone of some sort.   I hear all the horror stories of how bad these are off the boat, and want to start laying out a plan of what I'm going to do, and how.   I've got the "CD of hints" but, I don't have a workshop (dual knife edges),  and am wondering other ways to balance these things.
 I fugure if I'm lucky, I won't have sand & grit throuout the engine.
I'm looking at a choice between one of Geroges kits or a complete rack system from Bill @ Central Maine Diesel.   Bills system has the Listeriod on 4 rubber shock mounts, which appear to provide all the drive belt tension. ad page  http://tinyurl.com/24jjkq  I'm not sure if the rubber mounts are the way to go, or if there are failures associated with them.

And there is the speed HP choice I'm dithering about.  6HP @ 650 RPM  or 8HP @ 850 RPM.   I'm fond of the slower RPM's and concerned about taking the 6hp up to 8HP via RPMs, since except for the flywheels, there is no other difference ??

xyzer

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Re: engine balance - how to
« Reply #5 on: July 25, 2007, 04:09:02 PM »
Mike,
You can ran a 8hp at 650 but I would NOT run a 6/1 at 850. Searck for the misterx metod of balance useing chalk. They can't be made to run perfect but can be tamed considerably.
Dave
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Power Solutions portable 6/1
Z482 KUBOTA

M61hops

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Re: engine balance - how to
« Reply #6 on: July 26, 2007, 08:13:19 PM »
My Metro 6/1 is driving me crazy trying to get it even somewhat civil as to balance.  There is no reasonable amount of concrete that could hold it still the way it is.  I bought it 3rd hand and I suspect that the last owner got rid of it because it could not be held down.  I laughed like hell when he started it because I never imiagined that a motor could jump so high!  Since I consider myself to be a good mechanic and machinist I figured I could smooth it out but so far I've been somewhat humbled by Indian casting expertise.  At the moment I have the engine mounted on a frame with 4 steel wheels riding in leveled steel U channel and tethered by bungee cords attached to substansial weight so so the assembly is free to wobble a few inches any direction, although it can't drive the channels very far into the ground.  I have a 3HP golf cart motor & speed control set up to spin the motor at speeds from 0 RPM to 800 RPM but I don't exceed 660 out of fear of flywheel damage to me.  At this moment I have 2.5 pounds of weight bolted to the flywheels in the area close to the counterweights and it seems like a little too much.  I had to sand and repaint the flat surface of the flywheels in order to make the chalkmarks somewhat clear.  I can rotate the Metro in either direction and I make marks both ways.  I took out the COV hole plug and leave the compression release holding the exaust valve open.  It seems that the chalkmarks indicate that the counterweights are not heavy enough and also maybe they are a little out of position from where they need to be.  Basically so far I'm having trouble figuring out what the chalkmarks are telling me because adding weight does not change them hardly at all.  I'm wondering if there is something wrong with my method and I'll have to disconnect the camshaft and remove the head and crankcase cover?  I find it hard to believe that the valve springs and minimal air resistance of the piston could have meaningful influence in relation to the mass of the flywheels but there is an interesting thing I observe; at about 190RPM the frame rolls back and forth about 1/2 an inch in perfect time with the lifters rising and falling!  So far I haven't seen any consistancy with where I put weight and where the chalk marks move and I'm puzzled.  Any thoughts out in Listeroid land?  The counterweights appear to be clocked right to the crank throw and the flywheels run true, so I'm surprised at the inconsistancy of the chalk marks even though I try to be careful to hold the chalk up to the flywheels the same every time (minimum light contact at crankshaft centerline on breather side of engine).  The fun never stops in Listeroid land!     Leland
I pray everyday giving thanks that I have one of the "fun" mental disorders!

carlb23

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Re: engine balance - how to
« Reply #7 on: July 26, 2007, 10:17:55 PM »
M61hops

I too have a metro 6/1 and i used the chalk method with the engine running. What i found was that i had to add weight opposite the weights on the flywheel.  I added 2.8 lbs on each flywheel.  While not perfect it has calmed down quite a bit.


Carl

mobile_bob

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Re: engine balance - how to
« Reply #8 on: July 26, 2007, 11:34:51 PM »
guys:

as most know i debated with some voracity the use of resilient mounting of a listeroid

but the method used in the link  http://tinyurl.com/24jjkq

in my opinion is not in anyway desirable, and might even be dangerous

i would not support its use or recommend doing what is illustrated there.

bob g
otherpower.com, microcogen.info, practicalmachinist.com
(useful forums), utterpower.com for all sorts of diy info

Doug

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Re: engine balance - how to
« Reply #9 on: July 27, 2007, 12:56:44 AM »
Looks like its bolted to the floor but its hopping on the first power stroke....

Prices for spares aren't bad!

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rjcroc

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Re: engine balance - how to
« Reply #10 on: July 27, 2007, 09:21:09 AM »


M61

"The counterweights appear to be clocked right to the crank throw and the flywheels run true"

Do you mean at the same place as the crank throw or 180 from it ?

Rick
"THE GREATEST DANGER FOR MOST OF US IS NOT THAT OUR AIM IS TOO HIGH AND WE MISS IT, BUT THAT IT IS TOO LOW AND WE REACH IT"  MICHELANGELO
6/1 METRO, 6/1 LISTER SOM, 6/1 LISTER, 1 1/2 HP LISTER D, LISTER PUMP,LISTER PETTER LPWS4

ronmar

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Re: engine balance - how to
« Reply #11 on: July 27, 2007, 02:03:09 PM »
The counterweights should be opposite the crank throw.  That is what they are countering, the 20 some odd pounds of cast iron that form the big end journal as well as the weight of the big end of the crank.

have you read thru the Balancing threads up in the "Listeroid Engines" section?  I went over how I dynamically balanced my 6/1 in one of them.  They also discuss the MrX chalk method and having to compensate for mass acceleration when placing the counterweights in relation to the chalk mark.  Here are a few links.
http://listerengine.com/smf/index.php?topic=1882.0
http://listerengine.com/smf/index.php?topic=2199.0

Ron
 
PS 6/1 - ST-5.

rjcroc

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Re: engine balance - how to
« Reply #12 on: July 27, 2007, 03:54:15 PM »

Ron

I'm with you 100% The reason I asked is that there are some units with wrong wheels and some not broached in the right place. On my Metro 6/1 the counter weights are slightly off. If I place one counter weight at 12 oclock the other side is at 11. Dont know if that is by design or not.

Rick
"THE GREATEST DANGER FOR MOST OF US IS NOT THAT OUR AIM IS TOO HIGH AND WE MISS IT, BUT THAT IT IS TOO LOW AND WE REACH IT"  MICHELANGELO
6/1 METRO, 6/1 LISTER SOM, 6/1 LISTER, 1 1/2 HP LISTER D, LISTER PUMP,LISTER PETTER LPWS4

ronmar

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Re: engine balance - how to
« Reply #13 on: July 27, 2007, 05:25:20 PM »
counterweight to keyway mis-alignment has been noted by others.  I believe the twin flywheels are different from the singles so I wouldn't be surprised if some have encountered incorrect parts applied to their particular engine.  There could also be alignment issues that have not been identified such as bent/twisted crank.  It dosn't take very much offset of a 150# of flywheel to impart some energy.

Securely affixed to a ton of concrete can work wonders at masking these little imperfections:)  Personally I am picky enough to want to know exactly how it is setup and if it is running true/smooth before I finally anchor it down.  I spent quite a bit of time while mine was disassembled making sure the fit and alignment was correct.  It now runs smooth under 3KW load just setting on the garage floor(1000# frame/gen/engine weight).  It also ran good under 2KW load with frame still setting on 3/4" pipe rollers after I finished the balance work.  I will however still be bolting it down to a 1300# concrete block setting on a ruber/plywood base for noise/vibration isolation.
PS 6/1 - ST-5.

M61hops

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Re: engine balance - how to
« Reply #14 on: July 28, 2007, 06:50:34 PM »
Hi Rick, yes the counterweights are 180 from the crank throw.  The new paint I put on my flywheels seems to grab the chalk when I make the marks so that may be introducing some error into my proceedure.  The flywheels are correct for this motor and it seems the keyways are broached in the correct place on both, though the inner face of the rim on one flywheel has a little runout.  The chalk marks seem to indicate that the heavy spots are about 60 degrees off from where the counterweights are so there might be a density problem like a hollow spoke in the castings?  Nothing obvious to my eye yet.  I will fuss with it untill I'm satasified that I can't get it balanced any better but it is going to take much more time than I figured (what doesn't?).  I plan to set the frame with the engine and generator into a subsancial mass of concrete when I'm done balancing and I will do something to reduce transmission of the power stroke thump to the ground.  I want to end up with a generator/heat pump that I or at least my neighbors can't hear or feel running.  Quite a challenging project but this is the kind of thing I do for fun.  (Yeah, my friends think I'm nuts but they are polite to my face and usually use words like "excentric")  Well it's a beautiful day in the neighborhood so I'm outa here for now...   Leland
I pray everyday giving thanks that I have one of the "fun" mental disorders!