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Author Topic: Flywheel balancing question  (Read 36189 times)

overbore

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Re: Flywheel balancing question
« Reply #30 on: November 05, 2013, 06:03:35 PM »
I have noted, in unscientific environments, that an IC engine has an rpm sweet spot for the balance state of the rotating mass; therefore, my tentative hypothesis  is that if an engine ( Listeroid) is balanced with a given weight mass,  changing the operational rpm's outside the "sweet spot"  will change the needed weight mass for optimum balance. 

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Jordan

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Re: Flywheel balancing question
« Reply #31 on: November 05, 2013, 08:50:05 PM »
Do we know what is the balance factor that Lister recommended?
I think, if an engine's bolted firmly to a large block of concrete, this must help lessen vibrations.

Jordan

xyzer

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Re: Flywheel balancing question
« Reply #32 on: November 05, 2013, 10:49:57 PM »
I have noted, in unscientific environments, that an IC engine has an rpm sweet spot for the balance state of the rotating mass; therefore, my tentative hypothesis  is that if an engine ( Listeroid) is balanced with a given weight mass,  changing the operational rpm's outside the "sweet spot"  will change the needed weight mass for optimum balance. 

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Horsepoor

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Re: Flywheel balancing question
« Reply #33 on: November 06, 2013, 02:32:49 AM »
Guys, technically - it is so easy to balance a single cylinder - a little time consuming but not hard. After all, didn’t you get a Listeroid to tinker with it? So, we know that pulling the flywheels off has been discussed on numerous other threads, not hard to do when you have a flywheel puller. Bubble balancing, or pendulum balancing both flywheels so they are the same weight is not hard, but takes time. What you end up with is two flywheels closely matched. Put your newly closely balanced flywheels back on the machine.

Next step is using an accelerometer to give you a numerical readout of how well you are doing. It is possible to see the improvement by carefully noting the up and down bounce but numbers are nice. Most people or their children have an IPhone or an IPad. This $4.99 application will give you the IPS (inch per second – acceleration in the X, Y, & Z planes). Now you have numbers to verify you need to add more weight or remove some. Here is the link:

http://dld-llc.com/Vibration2Manual/Credits.html#Introduction

Early on in this thread there was an eBay link to order strips of ¼ oz weights with adhesive backing. The strips are about 6 inches long and each weights 3 oz each in total. I ended up with 6 oz on the inside rim and 6 oz on the outside rim for a total of 12 oz on each flywheel. In other words, my counter balances were 12 oz too light. Yours will likely be different.

Here is the method we used. Assume that on your identically balanced flywheels, either the counter balance is too heavy or light. Measure the amplitude of Y and Z direction IPS with your $4.99 application. Mine started out at 1.8 IPS in the Y direction and less than 1 IPS in the Z direction. After adding 6 oz on each flywheel next to the counter weight, we got 1.4 IPS in the Y and 1 IPS in the Z. Next with 12 oz on each flywheel, we got 1.2 in the Y and 1.1 in the Z. This is where we stopped. Visually, you can see the slight movement (vibration) front to back and very slight movement (vibration) up and down. I’ll shoot a video and post in a day or two but you’ll see a Metro 6/1, mounted on a nursery cart with wheels (moves easily), running so very smooth. I took the time to post these details because, it is so easy to do on a single cylinder using this application, I want others to benifit,    
« Last Edit: November 06, 2013, 02:34:37 AM by Horsepoor »
GTC 20/2 down rated to 850 rpm - ST 15
Metro 6/1 800 rpm on cart - ST 7.5

Jordan

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Re: Flywheel balancing question
« Reply #34 on: November 06, 2013, 02:41:01 AM »
The notion of sweet spot is sort of correct, but the other way around.
There's a "sore spot" in any reciprocating mass, when the frequency of vibration matches the natural resonant frequency of the mass, creating the worst vibes for it.
Avoid that freqency (and multiples of it) to lessen vibration.
Easy enough to do on a single speed engine. Bolt it to something heavy, if it vibrates excessively. That will change its inherent resonant frequency.
A portable engine isn't so easy to deal with.
I'm guessing the balance factor is 50% ?

Jordan

xyzer

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Re: Flywheel balancing question
« Reply #35 on: November 06, 2013, 04:59:10 AM »
Jordan,
I even agree with the sore spot description! After balancing 2 6/1's using several methods I believe they come from India at 50% that is why all of them are usually hoppers. Most stories of taming the 6/1 reveal the weight is usually added to the already counterbalanced area of the flywheel. Both of mine needed it in that area. My last 6/1 ended up at a 62% balance factor. That number was arrived at by dynamically balancing the flywheels using 100% of the bottom end of the rod and 62% of the wrist pin end of the rod 62% of the piston, pin, and rings. Any higher and it will become a slider. The cast iron piston is the gremlin. You defiantly have to balance it for the intended rpm need!

http://www.youtube.com/watch?v=eOxPXGn6BWo&feature=relmfu
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Horsepoor

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Re: Flywheel balancing question
« Reply #36 on: November 06, 2013, 05:07:30 AM »
My 20/2 GTC 850 rpm is sitting on several yards of fiber mesh concrete with 5/8 rebar inserted. It also sits on top of some improvised shock absorbers from a helicopter rotor system on heavy I beams. But this did'nt stop me from making an effort to balance the engine. More on this later on. Cujet, Rocketboy and I have thought about this a lot and want to standardize a twin balance method. But before I take this thread to twins, let's stick with single cylinders which is much less complicated due to the absence of a significant rocking moment ( side to side). A well balanced engine is more reliable, tears up fewer components, doesn't destroy our cheap ST generator heads as fast and is just, frankly, desirable. I am confident we have perfected the balance method for single cylinders. I world like to see others attempt the method and verify it is repeatable. Then let's move to twins.
« Last Edit: November 06, 2013, 05:21:13 AM by Horsepoor »
GTC 20/2 down rated to 850 rpm - ST 15
Metro 6/1 800 rpm on cart - ST 7.5

Horsepoor

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Re: Flywheel balancing question
« Reply #37 on: November 06, 2013, 05:13:10 AM »
I agree with everything XYZer just posted while I sitting in favored bar (brass ring, royal palm beach, 0030 hrs, drinking pitchers of coors lights, reading the forum, eating chilli. Life is good.. All our experience also indicates light on the counterbalance area, needing more weight. What we did having three engines between us was as follows: disassembled all three engines at the same time. Weighted all pistons, connecting rods, everything, then tried to match up similar parts. I remember grinding several ounces off of connecting rods, drilling holes in flywheels to remove a little metal from the rim, etc. this got us close, but we had three engines to work with 8 years ago.
« Last Edit: November 06, 2013, 05:17:34 AM by Horsepoor »
GTC 20/2 down rated to 850 rpm - ST 15
Metro 6/1 800 rpm on cart - ST 7.5

millman56

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Re: Flywheel balancing question
« Reply #38 on: November 06, 2013, 07:16:41 AM »
Good results, Horsepoor, Cujet and Rocketboy and great to see them backed up by qualifying numbers.
On the same subject  but off to the side and maybe Jordans niche.      When starting and running CSs sat on blocks of wood etc, its always noticeable that the ones with SOM flywheels do much less of a combined bucking bronco/ precession induced pirouette, when accelerating and decelerating, than the spoked flywheel ones, I guess mass is mass whether rotating or not, or could it be increased damping of the cyclic acceleration/deceleration?  Slower rate of speed change ? 

Mark.
   

Fairmountvewe

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Re: Flywheel balancing question
« Reply #39 on: November 07, 2013, 01:01:17 AM »
Hi all.  Well it is a blustery Wednesday night here in Fairmount, so I thought I would update you on my flywheel endeavours, and of course solicit more free advice on what to do next.

I finished grinding out the counter weights, and started making the device to hold my wheels horizontally (with apologies to all machinists everywhere)


Here is my jig already rigged up with the eyebolt and swivel


Here we are just a swinging in the breeze


  So I have one wheel suspended and I cannot find my handy bubble level.  No problem I thought.  I have an iPhone.  There must be an app for that.  And there is.  Except my phone is in a Lifeproof case, and the back of the case will not sit level on the center area of the flywheel, so the bubble isn't level, so I have no idea how far the wheel is out.  Well I am really no further ahead, except the wheel looks pretty level, so I am presuming I am close.  I still have to get a bubble level, and some stick on weights, so I guess a shopping trip is in order.
  Now to wait for Horsepoor to finish his installment on balancing a twin.  Thanks all for the input.

Peter 
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cujet

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Re: Flywheel balancing question
« Reply #40 on: November 07, 2013, 01:52:55 PM »
You can, of course, balance a twin the same way. By noting the vertical and horizontal vibration levels on each end of the engine. (each flywheel end)

It will take much more work than a single, and the rocking couple will never be eliminated. But the balance can be improved. Just don't expect smoothness.

Note, if you have a calibrated index finger, you can press it hard (pointing) on the block horizontally. Then vertically, on the block just below the cylinder. This will illustrate to you any difference in vertical vs horiz vibration. You really could get it close doing just this.
« Last Edit: November 07, 2013, 01:55:20 PM by cujet »
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Fairmountvewe

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Re: Flywheel balancing question
« Reply #41 on: November 16, 2013, 02:06:15 PM »
Update #3

The preamble;

I stopped by a local tire shop that does heavy equipment tires on the way home from work last week looking for some stick-on weights.  The fellow who runs the shop wasn't too interested with my unusual request until I explained what they were for.  Then he lit right up.  After a  couple of minutes of talking and with the help of a couple of pictures from my phone, he said that they have a $30000 machine in the shop that can balance anything that is designed to rotate, and to bring the flywheels in.  So yesterday I did just that.

 Mike and the guys at Benson Tire in Bowmanville Ontario (little plug because they were awesome - no affiliation) put the flywheels on a tire balancing machine, and balanced them. Now I am not saying I am some kind of grinding master......but.....



I think that kind of speaks for itself.. ;D

Of course the other wheel took 24 ounces of lead and was a real pain in the ass to do, so I obviously got lucky on the first one!  Ha!

So now the flywheels are balanced, and it is supposed to rain tomorrow, so it looks like I will be starting on my temporary stand next.  Listeroid nirvana and a first smoke video are coming quickly.  I can feel it. 
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, cooperate, solve equations, analyze a new problem, and pitch manure. Specialization is for insects.

overbore

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Re: Flywheel balancing question
« Reply #42 on: November 16, 2013, 07:23:37 PM »
Thinking outside the box is good; wish you good dynamic results. Keep us posted.

Laus Deo
overbore

xyzer

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Re: Flywheel balancing question
« Reply #43 on: November 27, 2013, 11:52:16 PM »
Update #3

So now the flywheels are balanced, and it is supposed to rain tomorrow, so it looks like I will be starting on my temporary stand next.  Listeroid nirvana and a first smoke video are coming quickly.  I can feel it. 

Curiously waiting for the results!
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Fairmountvewe

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Re: Flywheel balancing question
« Reply #44 on: November 28, 2013, 02:10:38 AM »
    Todays update.  It snowed around these parts last night, so to while away the hours waiting for morning, I headed out to the barn for a little Listeroid therapy.  At the end of the night, I was cold, tired, diesel soaked and actually further behind than when I started! 

    I put the flywheels on, and got the gib keys actually fitting.  Yay.  Success.  Then I got the fuel tank installed, fuel put in it, and the lines to the injector pumps full of fuel.  Yay.  Success.  Then I thought, "well.  May as well prime this baby up and see where that gets us" and that is when the wheels fell off.

    I couldn't get fuel up to the injectors for love nor money.  I cranked, and I bled, and I cranked some more.  I finally decided that there must be some kind of rational explanation for this, so I went back to the basics.  I tightened every fuel fitting on the beast, and sure enough, a couple of them were loose.  No Biggee.  Commence to cranking....again.  Nothing on one pump but success on the other.  Hmmm.  Now what?  So I looked, and I poked, and I fumed all to no avail.  Figuring that there has to be something I am missing, I took the flywheel off to look at things a little closer.  It seems that one of the camshaft actuated lifters under the  fuel injector pump was backed almost all the way down.  The lifter was going up and down, but it wasn't even contacting the bottom of the pump!  That explains the lack of fuel to the injector.  So I adjusted the bolt assembly enough to get fuel up to the injector, but after thinking about it for a while today, I think I am going to take both IPs off, measure the good lifter at TDC, and adjust the other one so it is the same.  Is there actually a value I should be looking for?  Any one know?

    In the process of all this prodding around the fuel system, I have discovered that the outboard IP lever assembly doesn't really line up very well with the IP rack, causing the rack not to travel freely, and kind of bind.  It looks like it is just a matter of some shimming and maybe some grinding.  Here's hoping.  I promise to take some pictures (for the more visual among us) the next time I am out working, but I am house bound for the rest of the evening - Skype call to my Grandson in 24 minutes.  Cant miss that.  Even for a Listeroid!
A human being should be able to change a diaper, plan an invasion, butcher a hog, conn a ship, design a building, write a sonnet, balance accounts, build a wall, set a bone, comfort the dying, cooperate, solve equations, analyze a new problem, and pitch manure. Specialization is for insects.