Well balanced 'roid!

[Hibbo]

Just stumbled across this http://www.youtube.com/watch?v=3a6RZFHyIdQ&NR=1

Do the balance of an engine differ with load? (what I'm trying to ask is would any imbalance manifest itself more when loaded?)

[Reno Speedster]

The first one is nifty and the second very interesting.  In the second I love the shot of the guy beating on the engine with a sledge hammer (looks like he was beating on the crank shaft!)

[Doug]

He was, thats a Gib Head key being smashed in

[ronmar]

Do the balance of an engine differ with load? (what I'm trying to ask is would any imbalance manifest itself more when loaded?)

The balance itself dosn't really change as the same moving parts are moving the same way wether loaded or not.   What does come into play is the difference in applied torque to the flywheels.  In that first video you linked to you will notice the engine jump around a bit right after it first fires.  That is because the governor is holding the rack at full throttle position trying to accelerate the flywheels to the governed RPM.  The mass of the flywheels is of course resisting this change and provding a load so the engine block is trying to torque the opposite direction and is basically pulling a wheelie on every power stroke.  The only thing keeping the engine block from toppeling over is the overall weight of the entire engine resisting this force trying to lift it up onto the back edge of the block.  Once up to RPM, it takes very little torque/throttle to maintain that RPM with no additional load so the movement settles down and looks good with a glass of water setting on top.  IF it had a generator bolted to it and a load was applied to it, it would again start to move around a bit and the engine case would start to wheelie again.  Since the overall mass of the engine has not changed, This movement would not be as extreme as that at startup as the power stroke would occur over a much shorter ammount of time and at a quicker rate.  This would look more like a vibration, but it would be torque related.   

Ron

[Reno Speedster]

He was, thats a Gib Head key being smashed in

That could explain why my bearing races were so screwd up.  They showed a line in the race for every roller.  I thought it was from rattling in shipment but if thats how they put the gib keys in!  Beating like that is incredably bad for a tapered roller bearing. I'm hoping to get my crank back with the new bearings pressed on today so I can get it back together soon.

Do you actually have to beat the keys in that hard?

[Andre Blanchard]

Do you actually have to beat the keys in that hard?

Not if the shaft, hole, keyways, and key are properly sized.

I made an arbor a while back for grinding some parts.  The end of the arbor fit in a hole in the part.  The arbor was split in one place and had a tapered hole in the center with a matching tapered pin.  Hole in the part was about 0.0003" larger then the arbor.
One light tap on the pin from a 6 oz. hammer and you may as well have welded the part onto the arbor.