Crank balancing question

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CanukNortonNut said:
I believe Ed balanced that crank to your piston, piston rings, the small end of the connecting rod, etc, or whoever, when the engine was built. I use Forest & Forest here in Ontario and they do the same thing with holes in the cheeks. Herb Becker uses these guys as well and he recommended them to me.
Cheers,
Tom
Click to expand...
This would be Dynamic balancing ? Did Forest & Forest drill your flywheel for Static balance also, or just the crank cheeks ?

Mike

Does that make replacement weights of pistons, wrist pins and rings more critical to balance then standard static balancing ?
 
When weight needs to be removed from one of the "cheeks" the most common way of removing same is to grind it off followed by machining .

Best
 
RoadScholar said:
When weight needs to be removed from one of the "cheeks" the most common way of removing same is to grind it off followed by machining .

Best
Click to expand...
And it’s the best way as it doesn’t weaken the structure as drilling can.
 
Fast Eddie said:
And it’s the best way as it doesn’t weaken the structure as drilling can.
Click to expand...
That was my thought also, but I don't know squat in this area and if Herb Becker recommended a shop that does it this way to CanukNortonNut, then it must be a proven method and good enough for me.

Thanks for your input !!
Mike
 
RatedSpeed said:
That was my thought also, but I don't know squat in this area and if Herb Becker recommended a shop that does it this way to CanukNortonNut, then it must be a proven method and good enough for me.

Thanks for your input !!
Mike
Click to expand...
Exactly… I didn’t mean it to be something else to worry about !
 
My -73 850 flywheel, holes everywhere but none deep enough to put a rod in. So it was back to the old "rod through the rods" method..... worked fine. Not sure, but it seems the holes in the wide side is filled up with something, lead? A bit strange since there are holes in the narrow part as well. I mean they could have skipped those and not having to fill in the other holes, I don´t get this.
Crank balancing questionCrank balancing question
 
Could be Mallory metal

Mallory metal - Wikipedia

en.wikipedia.org en.wikipedia.org

Its primary use is as a balance weight which is added to the crankshaft of an automotive engine, where the existing counterweight is not large enough to compensate for the weight of the reciprocating and rotating components attached to the crankshaft's connecting rod journals. Rather than add to the counterweight by welding or fabrication, holes are drilled in structurally safe positions in the counterweights, and "slugs" (cylindrical dowels) of Mallory metal are inserted and fastened securely.
 
kommando said:
Could be Mallory metal

Mallory metal - Wikipedia

en.wikipedia.org en.wikipedia.org

Its primary use is as a balance weight which is added to the crankshaft of an automotive engine, where the existing counterweight is not large enough to compensate for the weight of the reciprocating and rotating components attached to the crankshaft's connecting rod journals. Rather than add to the counterweight by welding or fabrication, holes are drilled in structurally safe positions in the counterweights, and "slugs" (cylindrical dowels) of Mallory metal are inserted and fastened securely.
Click to expand...
Interesting, is that method known to have been used by the factory? But it still seems very unnecessary to drill the holes in the narrow side, becomes pretty counter productive.
 
fiatfan said:
Interesting, is that method known to have been used by the factory? But it still seems very unnecessary to drill the holes in the narrow side, becomes pretty counter productive.
Click to expand...
If you still have the flywheel loose can you weigh it ? Would be informative.

What is the width of the wide end ?

Mike
 
RatedSpeed said:
If you still have the flywheel loose can you weigh it ? Would be informative.

What is the width of the wide end ?

Mike
Click to expand...

Mike,
I have a 750 flywheel separated from the cheeks, Casting # 06-0732. This is set asides for another project...ie spare engine from a collection of parts gathered. Weight is 11 lbs (weighed on a bathroom digital scale)... so its not going to be accurate to the gram. No pin, no nuts/bolts or studs...just naked.
and it is 2.227" wide at the widest point.
No dynamic balancing, but as it came from the factory... OEM... to my knowledge. I am not 100% sure of the vintage.
I bought this crank assembly as a unit, but have no engine cases to confirm the date of manufacture. I believe it is a Commando era 750.
Cheers,
Tom
 
CanukNortonNut said:
Mike,
I have a 750 flywheel separated from the cheeks, Casting # 06-0732. This is set asides for another project...ie spare engine from a collection of parts gathered. Weight is 11 lbs (weighed on a bathroom digital scale)... so its not going to be accurate to the gram. No pin, no nuts/bolts or studs...just naked.
and it is 2.227" wide at the widest point.
No dynamic balancing, but as it came from the factory... OEM... to my knowledge. I am not 100% sure of the vintage.
I bought this crank assembly as a unit, but have no engine cases to confirm the date of manufacture. I believe it is a Commando era 750.
Cheers,
Tom
Click to expand...
Tom,
Thanks for the specs. How many relief holes are in that flywheel ? It appears common ? that it's 1 hole in 750 and 2 in the 850's.
You specs look closer to Marinatlas and mine, width between the 2 -1/2" 750 and the 2-3/16" 850.

Mike

I'm starting to compile flywheel specs to try and make some sense of this.
Displ. Width Weight
Torontonian: 850 2.1875
Grrumpy Knob: 850 2.182
Arch: 850 ? 11 lb-6ozs

John Tickle: 750 2.500
Kommando: 750 2.500
CanukNortonNut: 750 2.227 11 lb
Casting # 06-0732
Grumpy Knob: 750 2.516
Arch: 750 ? 10 lb-11.5

Marinatlas: Unkown 2.32 ( 58.9mm)
Ratedspeed: Uknown 2.32
 
Dynamic balancing is usually done to adjust secondary balance - the rocking couple. On a big 360 degree twin, the rocking couple is usually negligible. My 850 crank is standard commando. It has the big hole drilled into the counterweight which I have filled with a steel plug. The plug brings the balance factor from 54% to about 72% which better suits a rigidly mounted motor revving to about 7000 RPM. Most road bikes probably get ridden at at revs around 4000 RPM.
I suspect the Commando crank is simply the Atlas crank with a hole drilled into the counterweight. My mate's racing Atlas motor revs to about 8000 RPM and has a balance factor of about 79% It is in a featherbed frame.
 
It is really funny. When my motor is idling, the whole bike moves backwards and forwards. But when it is at peak revs, it is dead smooth. You would not want your road bike to be like that. It is no wonder the smoothness of the CB750 Honda freaked Norton out. The Hondas were good for the duffle-coat brigade. Wooses don't want to ride real motorcycles.
 
acotrel said:
It is really funny. When my motor is idling, the whole bike moves backwards and forwards. But when it is at peak revs, it is dead smooth. You would not want your road bike to be like that. It is no wonder the smoothness of the CB750 Honda freaked Norton out. The Hondas were good for the duffle-coat brigade. Wooses don't want to ride real motorcycles.
Click to expand...
What I'm noticing is, there's a few flywheels that have a width in between the standard 2.500 (750) and the 2.1875 (850). If you look back at post 34 you see that Canuk's flywheel weighs in at 11 lbs and it's a 750 casting ( 06-0732 ). Aren't 750's usually in the 10.750 lb range?
Was the Combat flywheel a little heavier for the higher compression and RPM range ?

Mike
 
RatedSpeed said:
How many relief holes are in that flywheel ? It appears common ? that it's 1 hole in 750 and 2 in the 850's.
Click to expand...
I believe that there were three holes but I am at work now so need to recheck when I get back home in a couple of days.
I'll report back.
 
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