Balancing out the Bounce---

[hotater]

I was just thinking of the gal I saw that helped gather cattle this fall.     I thought it was her saddle bags bouncing.....

poor horse.   

[cujet]

I agree, mounting these engines on a huge slab of concrete is a good thing! Letting them move around is probably not a good thing.

Balance factor of 50% is a good place to start for a single or 180 deg twin. In reality, 53% to 55% works well in smaller engines. However for our discussion the ideal will not vary beyond 50 to 55%. 0% or 100% are the extremes.

Rocking couple is aggrevated by improper counterweights.

With a twin flywheel such as the Lister, rocking couple can be lessened somewhat by adding small weights on the flywheels. However some of this depends on the mass of your engine/generator frame.

I still say the best bet is to start with 50% balance factor for each cylinder. If you feel really bold, go with 53%.

Another thing, maybe after balancing each component, the entire rotating assy (crank, counterweights, flywheels less rods) can be balanced as a whole before final assy.

Chris

[quinnf]

Chris, 

You're probably the guy to ask this of:  When you static balance an engine, I was taught you do like Clifford explains on George's Utterpower CD.  That is, you place the big end of the con rod with bearing, bearing caps, nuts, dipper, whatever, on a balance (a scale), leaving the small end of the rod suspended off the balance pan.  The weight that registers on the balance is then the bobweight that you attach to the crank journal while you then balance the crankshaft with flywheels attached.  On my 'roid, that amounted to about 6 lbs., yet the weight of the complete con rod assembly was about 9 lbs.  So there's about 3 lbs. of high-quality Indian cast iron that's rotating in synch with the crankshaft and flywheels that's not accounted for in the bobweight.

All of the connecting rod is rotating in synch with the crankshaft, from the big end all the way up to the center of the small end of the rod.  The circles the mass of the con rod describes with each revolution become enlongated into ovals, with smaller areas, and therefore less energy as you proceed up the connecting rod.  So why is it that only the mass of the big end is set on the balance?  That seems arbitrary, but that's how it's commonly done.

Any thoughts?

Quinn

[hotater]

It's NOT the lack of coffee that's making your head hurt......

[quinnf]

Re: the aforementioned cowgal,

I was at a horse show a few months ago where my daughter was showing off.  A grizzled old guy with tobbaco stains running out the side of his mouth (evidently he worked there) was leaning on the rail next to me as a particularly _well-fed_ young lady trotted past, well, the horse was doing most of the trotting, but you get the picture.  A few moments after she passed, he spat and drawled, to nobody in particular, "I call that one Crisco.  Yep, fat in the can."

q.

[Mr X]

Im a carpenter not a mechanik But couldent you pull the head off and the barrel pull the rist pin and now read the  weight of  the piston, and subistitute weights taped or held to the con rod. in place of the piston. Pull any thing elets which could cause drag and spin it over by hand.[ of corse youll have to suspend the con rod  some how and not let it flail around the crank opening]  Isnt the heavy side going to gravitate to the  bottom. Do this a coupel of times and you could have the general area of the heavy side , now you can start to tape weights to the fly wheel May be?  Ill have to purchase my first roid before I can speak with experiance.

[quinnf]

Mr. X,

Welcome to the board.  You know, having a 6/1 chugging away in the bed of your pickup truck as a jobsite generator would sure be cool.  Could belt a great big air compressor off the flywheel and supply enough air for the whole job.  Wouldn't get much work done with all the guys standing around and saying how cool it is, but I bet you'd be popular! 

If I understand what you're saying right, I think the problem is that as you go higher up the cylinder toward the wrist pin, the motion becomes less circular and more up and down.  When you finally get to the wrist pin, it's ALL up and down.  So if you used the whole weight of the connecting rod, and used that figure for your bobweight, you'd have too much weight.  Somewhere there's a tradeoff, and I think weighing the big end and ignoring the weight of the other end must be the compromise that is usually made. 

My question to Chris was WHY static balancing is done that way.  I know it works, at least that's the way I've seen it done in the shop and heard a good handful of people explain it, so I know that's the standard way it's done.  Since Chris is an aircraft mechanic, he has access to some aircraft-type instrumentation that might operate on different principles than the usual auto/motorcycle stuff I'm familiar with.  I thought I'd pick his brain a little to see what his understanding is.

Quinn

[cujet]

The crankshaft bobweight must also balance out some of the reciprocating mass of the small end of the rod, piston, pin and rings.

Using a single lister as an example:
If no balance factor is used, as in the example above, the rotating mass will be perfectly balanced. So, anytime the crankshaft is at (roughy for geometry reasons) the 90 degree point the engine is in balance. Piston is neither accel or decel. However at either end of the stroke the reciprocating forces come into play. This engine would jump up and down but not fore/aft.

Adding roughly 50% more weight to the bobweight will even out the vibes up/dn and fore/aft. Generally this is a better situation. The original Lister had no crank bobweights but did have flywheel weights opposing the crank pin. Really just as good in a single.

Chris

[Stan]

I just received a couple of pics on the "new" powerline" brand which now puts a light green  counterweight on the crankshaft.  If this is a normal thing and I just don't know it, ignore this post.  If you'd like to see the pics let me know and I'll try to post them on the pics page.  I've also got pics of their oil filter, and other improvements.
Stan

I have no connection with this company and don't sell anything remotely connected with Listeroids, and I don't have any other identity on this or any other website

[n2toh]

Pertaining to what I posted ealier, If we balance a single at 100% it will rock for and aft this can be eliminated by suspending a weight over the head connected by a section of all thread (to the head) and adjusted the height untill the rocking stops.

[hotater]

n2toh---

By golly I *understood* that post.....and I have all kinds of all thread and ways to make weights.
If you can explain how to attain 100% percent figure as simply, I'm a tryer to prove concept.

Does this mean if the threaded rod were adjustable in two directions a location could be found that would counteract movement in any direction?

Could a magnetic rooftop antenna base be used to attach a counterbalance to a plate held horizonal to the engine by head bolt extensions?   How long the rod and how heavy the weight?

[n2toh]

n2toh---

By golly I *understood* that post.....and I have all kinds of all thread and ways to make weights.
If you can explain how to attain 100% percent figure as simply, I'm a tryer to prove concept.

I'm not an ME I just retain alot of what i'm told. the 100% was just an example as it would stop all the up and down.

As to how to attain 100% i'm not sure, but bolting the engine to a slab should stop most of the up and down and the suspended weight will still stop the for and aft rocking.

I don't have to formula to determin the mass of the weight or how far up it needs to be suspended. ( My ME friend has been out of touch for the last few weeks ) And I don't know what the technical name for it is, makes googling it hard.

untill such time that I can ask I would say start with 10% of the engine mass and experiment with the height untill you get the greatest reduction in movement. Please note that the weight will dampen fore and aft rocking as well and side to side, but not up and down

[quinnf]

All the talk about balancing the 'roid is interesting, but one factor of the ListerRock I haven't heard mentioned is inherent in the design.  It's a very heavy vertical engine mounted on a very narrow base. 

Most chore-duty engines at the time the Lister arrived on the scene were hotizontal engines.  As such, the typical work engine's center of mass was low, and they had engine mounts that were placed far apart.  Compare that to your 4' tall 800 lb. overhead valve (and therefore even taller than was usual) 6/1 held down by four skinny bolts located only 13" apart.  That was something that distinguished the Listers from most everything else.  A decision was made that the engine was going to be a vertical (perhaps to set them apart from the competition?). 

And to make matters worse, its a diesel!  Bad enough that most engines of the day were horizontal gas engines with compression ratios of like 4:1 to 6:1, 'cause they vibrated quite a bit, too, but the Lister has the tremendous kick of high compression, then an explosive power stroke 180 degrees later, both forces twisting the engine's mounts apart in different directions  650 times/minute.   Like the fat lady in a thong jogging down the boardwalk.  It's badly in need of some support.

Point being anything you do to try to civilize the 'roid should involve ensuring that it is rigidly mounted on something that doesn't flex much.  Steel I-beam or channel or welded angle of heavy gauge, with spans kept short will provide rigidity.  Wood or truck tire tread beneath the steel will absorb a lot of the high-frequency vibration, but you really can't get away from the need to bolt the whole thing down on something really heavy like concrete. 

Quinn

[kpgv]

Hi All,
I've followed the discussion here regarding the "bounce" and looked at all else I can find (G.B.'s CD, etc.).
I need to be able to run this 6/1-ST5 rig on a slab (attached) garage floor.
Assuming a reasonably well behaved and "balanced" engine, the "frame" is next.
The "simple" (factory recomended) dedicated concrete machine base is, for me, not an option.
I do think weight (lots of it), and stiffness are the most important elements for a "frame".
Then, there is the "isolation" issue.
I was thinking...
What if one used structural (A-500) rectangular TUBE for the "rails" on the mount.
6"x4"x.250" and 8"x4"x.250" are fairly common and available.
I know this stuff "rings" like a bell......but what if one FILLED the tubes with something?
I have considered concrete...Heavy, non-removable, not "elastic". I think this is the stiffest, and heaviest case.
Or.....
What if the tubes were filled with something heavy, and loose...and removable.
Like maybe gravel, or sand, or a mix...(Not as heavy, but CHEAP).
Or.....
Like maybe "Steel Shot" (HEAVY but more expensive).
I am wondering if a heavy, loose fill in the "tubes" might "confuse" and "deaden" the hard dynamic and harmonic pulses.
(Like during an earthquake when the "soil" kind of turns to "pudding")
I'm thinking of the opposite of a "dead blow" hammer.
Of course, this will be set on some sort of rubber "isolation" pad(s).
Another thing I thought about is if it might be better to make the "frame" a fiew inches longer, so the engine is out "on the bridge" instead of beating right on top of the pads on one end. (This, I know requires a STIFFER frame, but spreads the load).

Kevin


 

[Joe]

Kevin,
I just picked up some steel for my base at a scrap yard yesterday…talk about a kid in a candy store.   Anything and I mean anything was available…from a mountain of old cast iron house heating radiators to used machinery and structural steel.  Price was .25 per pound, which seems expensive but the selection was outstanding.  From what I gather scrap prices are high…China is scooping up all they can get. 
I looked at using rectangular/square tubing for base rails but talked myself out of it for a number of reasons.  My primary concern was that it did not lend itself easily to bolting to anything especially compared to an “I” beam arraignment. I don’t know what you are planning or what else you may have laying around to use in the project but that was my dilemma.   I would have ended up welding tabs or ears on in order to bolt it down. 
Sand would certainly deaden the sound and be removable.  In another life I mixed concrete and replaced some of the gravel with steel slugs to make extra heavy counter weights.  Wheel weights/spent bullets would do the same. You could go with straight wheel weights and then pour in something to bind them together so they didn’t rattle.
In the end however, I went with “W” beam because I thought fabrication would be easier with the other stuff I have laying around.  Specifically for the base frame rails I picked up 8”x 18lbs/ft foot because there was a nice clean piece at the scrap yard.   I laid some ideas out in AutoCad and intend to make the frame 48” long by 27” wide.  The end cross pieces will be 5” “C” channel. Both the engine cross mount and the generator mount will be made from 1.5”x18”x 27” solid chunks of steel…I‘ve had a 9’ piece of this laying around so I finally have a use for it…cutting it takes a bit of effort…. I guestimate I’ll have about 600 lbs of steel in the frame alone.
I realize you are not going to pour concrete for a base.  Are you planning on shear weight to hold things in place or will you be mounting to the garage floor?  Initially I’ll be temporarily setting up in the garage to test out things before I build a permanent home for it.  I very much want to make it run as quietly as possible.

Joe