Value of Engine Balancing

[Charles P]

The "pivot and scales" method with a simple jig was the one that I was going to use.
For the record I'm buying some scales for the workshop. Too much jeopardy in "borrowing" ones from the kitchen.

Charles

[Ruairidh Dunford]

The one in my picture is my garage set - £3 from Asda, very useful.

[Alan]

Garage set?? Please don't tell Judy which ones I use.

[Colin Reed]

Hi All, Whether you balance the rods yourself or not the Balancer will still need the rods including shells if fitted & Pistons . this is because  half the rod is  rotating  and the other half including piston is reciprocating  and they need to add  weights  on the Big end journals  to replicate  this weight for balancing.
My preference is to balance the crank like this then add flywheel and pressure plate and rebalance this means on the second balance only these two items have weight add or removed.

This is just my way of doing it and food for thought
hope this is not to contentious
Colin

[Bob Culver]

Hi Colin

What you state applies to V8s, flat twins, v twins and such like for which balancing is a tricky  topic often not much understood by many doing it! But not required for symmetrical inlines etc. 


And Nick
I am curious that new cranks are significantly out of balance dynamically. Hopefully are at least in static balance!

Balancing here was an expensive process, in large part because the local practioner instead of working to commercial tolerances persisted to the limits of his machine.

(Unrelated to our engines, but let loose on flat twins he expensively removed vast material making the engines much less smooth then originally!)

[Nick Turley]

Hi Colin

What you state applies to V8s, flat twins, v twins and such like for which balancing is a tricky  topic often not much understood by many doing it! But not required for symmetrical inlines etc. 


And Nick
I am curious that new cranks are significantly out of balance dynamically. Hopefully are at least in static balance!

Balancing here was an expensive process, in large part because the local practioner instead of working to commercial tolerances persisted to the limits of his machine.

(Unrelated to our engines, but let loose on flat twins he expensively removed vast material making the engines much less smooth then originally!)

The cranks I have had are in balance statically but not dynamically Bob

[Charles P]

I built a jig for mounting rods and weighing the ends. 
Just need to decide where to remove the weight around the big end

   

Charles

[Ruairidh Dunford]

I only weigh and balance the little ends like that Charles - then weight in total, removing material from big end to adjust balance.

[Alan]

I'd start by "adjusting" side clearance. Up to 25 thou is fine on a high revving engine. That should give scope to get the weights equal.

[Charles P]

I'd start by "adjusting" side clearance. Up to 25 thou is fine on a high revving engine. That should give scope to get the weights equal.

Thanks Alan. Exactly the advice needed. 
I nipped out and did some measurements, did a like calaculation and taking the heavy rods up to 20thou side clearance should get everything to within 1 gram at the big end.

Charles