A fresh look at engine balancing at home.

[bandmiller2]

If you recall before computer wheel balancing tires and wheels were balanced on the car.A sending unit was attached to the car to sence vibration and a strobe would flash to show where weight was needed.Its bygone technology now and the units could probibly be had cheap.For large trucks there was a pickup unit they placed under the front axle,then spun the wheel with a electric motor and friction wheel.Hopefully someone here knows more than I do about it. Frank C.

[bandmiller2]

Very common was the balancing unit that would clamp on the cars front wheel.The afore mentioned motor and flat wheel drive would spin the tire to speed.If I recall their were four knobs the mechanic could adjust weight wile the wheel was spinning and they would tell him weight needed and location .The only problem with a roid would be clamping the unit on true. Frank C.

[38ac]

 

[bandmiller2]

38ac,isn't that always the way, no easy fix,Guess thats why the good engines cost much more, the devil is in the details. Frank C.

[dieselgman]

Rotating forces can be relatively easily balanced, reciprocating forces less so. The total picture becomes a compromise between these two forces, and to make things worse, the reciprocating force changes fairly drastically according to engine speed as well. A compromise between brute force and finesse must be struck, therefore the common old-school methods of using massive concrete to anchor these babies.

There is a lot to be said for internal crankshaft counterweights... most modern engines are balanced in this way as well as a handfull of the Lister clone engine variations - especially the larger displacement longer-throw designs.

dieselgman

[BruceM]

I agree, the internal counterweights would take a lot of stress off of the flywheels and crankshaft.  Plus it makes balancing the flywheels easier. You could still do fine tuning via flywheel weights, also.

[skippytdi]

Yes, hello and thank you for the welcome.
I am picking up what ur putting down regarding weight evaluation prior to drilling/adding weight.
I'm a little confused regarding where you take off or add weight to, i took your picture and added red dots to where it appears you made your holes and im wondering if you could possibly expound as to why that is the area you chose to drill.
Also i am seeing some variation on determining offset weight, mainly in that some calculations include adding the big end of the con rod after determining percentage of small end of con rod and piston.  Could you set that in stone, so to speak. 
Thanks for the time.

Hello and welcome! No stupid questions here.

A. In one of my posts in this thread I said that a person needs to evaluate both wheels before he starts drilling and adding weight an attempt figure out a course of action so you dont end up drilling holes to accomplish one goal and adding weight over them to make another goal. As an example if you calculate the off set weight in two flywheels and flywheel A has 10oz more offset weight but also needs the weight centered you would want to try to drill holes in an are a that not only centers the weight but also serve to lessen the off-set. So many variables that a person just needs to evaluate his own wheels and go from there.
B. In every Indian Engine I have worked on they needed more off set weight, not less so in that case I would add weight to the off set of the lighter one to match the flywheels.

Once you get the flywheels to a corrected state the rest is dead easy. Start the engine and if it jumps or walks in a circle you have something wrong, fix before going further. Assuming it is either jumping straight up and down or walking a straight line. THEN using the Mr X method add weight to the side opposite the chaulk mark  ONLY centered at the heavy spot or 180 opposite. and in equal amounts for both wheels.

[overbore]

What happens to the can & string while the engine runs 

YOU GET STONED!!!
OVERBORE

[dieselgman]

You are correct, these machines should be smoothed out (via balancing) so as to reduce metal fatigue and wasted energy as much as possible. It sounds like yours must be lacking considerably in that department. I would review the various "methods" suggested on this forum so as to reduce the amount of trial and error required to figure it out.

dieslegman

[2ringers6]

I did this method of balancing with a different setup.  I didn't have any 2" round stock.  A 12" long piece from McMaster Carr is $47.  Probably another $20 in shipping.

I do have 1" round stock.  I ordered 2 bearings 2" o.d. with flange for a 1" shaft.  Slid a bearing in each side of the flywheel put the shaft in and rested the ends of the shaft onto a pair of saw horses.  ( jack stands would work also).

It worked very well.  The flywheels turn easily in the bearings and always come to rest in the same position.

[scrapman]

A question for all that Ive never seen asked is has anyone put a dial indicator on out side of the flywheels and determined the run out due to driving key home and are both flywheels the same ,also where in relationship to top dead center?
Peter

[BruceM]

I think the runout problem something easily remedied by fine balancing.

Great idea using 2" OD, 1" ID bearings, 2Ringers6.

[shiftless]

What a great thread! Thanks for taking the time to work this out. I just bought that Metro 6.5 HP engine that was for sale in Kalamazoo. It is direct injection with an aluminum piston and is a "scooter.." Definitely needs some balance work and while some of these posts are hard to understand, I think I got the gist of it. I want this thing running smooth as I can get it. The main thing that concerns me is getting the gib key out! The previous owner already took off one wheel and put in a new key with a big ledge that makes it easy to remove. Guess I better get to soaking the other one...

[jfgalaup]

Hello,

See the link below. It is theoric for dynamic balancing.

http://www.emachineshop.com/machine-shop/Dynamic-Balancing/page187.html

I don't try it.

Just for your information.

Best Regards.

Jfgalaup