Commando Crankshaft Porn

Dances with Shrapnel said:

Good stuff there Jim.

I just watched the video and wondered what it would be like if one of those got loose in your shop. :lol:

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Yeah, I thought about that too. The only crank I had spun that fast was the crank from my bike. It just sat there at full speed.

When I was making the video I was wanted to show how much the crank was shaking but I knew it would be hard to see. So I cranked it up -and held my breath.

Before I do that again I think some safety loops might be in order. Jim

Before I do that again I think some safety loops might be in order. Jim

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Now where's the fun in that in this digital video aga. Maybe just creep up on rpms to detect flight attempts to correct long before speed of lift off. May have to train someone else to handle the tedium of flood of cranks to smooth out.

Thanks Man! After 38 pages I feel like this thread just dropped it's solid rocket boosters and now heading for hyper space! .....and we get to come along for the ride! Awesome, thanks!

Thanks for showing us. Static and dymamic all in one video, makes it all the more convincing. Glad though you and the camera man/woman survived to tell..
Just wondering: the parts that are normally attached to the crankshaft like sprockets, rotor, etc, should they be mounted during balancing, or can they safely be ignored?

Wow, im impressed and a bit scared for you (should've had a MythBuster's shield)...

I make the assumption that the weights added are equal rod and piston collective? :? :? :? im not sure (as are others maybe) is that so ? ..

I also noticed that within the static balance part of vid, the crank was stopped at 180 degree placements (eg 90 & 270 degrees). So, in my SOC head it should balance at 1-7 oclock, 2-8 oclock etc or anywhere within the 360deg's to be balanced :? :? :? :? .

I ask this question out of ignorance because i've never been privy to "dynamic balancing" of a norton crank before...



( i feel like im doing another apprenticeship, since i found a Norton)



.

slimslowslider said:

Thanks for showing us. Static and dymamic all in one video, makes it all the more convincing. Glad though you and the camera man/woman survived to tell..
Just wondering: the parts that are normally attached to the crankshaft like sprockets, rotor, etc, should they be mounted during balancing, or can they safely be ignored?

Click to expand...

First you would want to balance the crank alone. Then if you wanted you could put the rest of the parts on and check it. If there was a change then you would remove material from the parts you install. Since the parts are small diameter they would need to be quite a way off to affect the balance in a big way. Jim

http://www.lindskog.com/automotive-balancing/ Lindskog's Zint did Ms Peel's 1st crank and included the alternator rotor which definitely added to Peel's disheartening about 2000 rpm.

olChris said:

Wow, im impressed and a bit scared for you (should've had a MythBuster's shield)...

I make the assumption that the weights added are equal rod and piston collective? :? :? :? im not sure (as are others maybe) is that so ? ..

I also noticed that within the static balance part of vid, the crank was stopped at 180 degree placements (eg 90 & 270 degrees). So, in my SOC head it should balance at 1-7 oclock, 2-8 oclock etc or anywhere within the 360deg's to be balanced :? :? :? :? .

I ask this question out of ignorance because i've never been privy to "dynamic balancing" of a norton crank before...



( i feel like im doing another apprenticeship, since i found a Norton)



.

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The bobweights are a total of the rods big end with bearings [rotating weight] plus the balance factor X the rods small end and piston weight [reciprocating weight] plus the weight of the oil that would be in the crankshafts sludge trap.

In the video I started with the standard Norton bob weight and then modified the bob weights to get the best static balance.
If I were actually balancing the crank I would have modified the crank to obtain balance instead of modifying the bobweight.
When static balancing the crank would stay in any position and not favor any one spot when you give it a little push. Jim

comnoz said:

Dances with Shrapnel said:

Good stuff there Jim.

I just watched the video and wondered what it would be like if one of those got loose in your shop. :lol:

Click to expand...

Yeah, I thought about that too. The only crank I had spun that fast was the crank from my bike. It just sat there at full speed.

When I was making the video I was wanted to show how much the crank was shaking but I knew it would be hard to see. So I cranked it up -and held my breath.

Before I do that again I think some safety loops might be in order. Jim

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Hoops to hold the crank but a full guard is needed to catch any counter weights that may come apart.
When I was an apprentice my boss balanced a v8 crank as a favour for a local speedway driver, got it all balanced and thought he would try a high speed spin, one of the bob weights broke, he paniced, hit the stop button,and hide down behind his machine as a v8 crank started playing pin ball between the roof ,balancer,walls and floor, at 2500rpm it rooted every thing it touched.
If you keep waving your hands over them while they are spinning you may very soon be a one handed Norton mechanic

It would be interesting to see you spin up a crank like in your video after it has been dynamically balance. Of course we would hope it would be smooth as silk.

New one on me, crank balancing installed in cases with barrel and jugs, huh.

[video]http://www.youtube.com/watch?v=jEmSJYGB-ws[/video]

kentvander said:

It would be interesting to see you spin up a crank like in your video after it has been dynamically balance. Of course we would hope it would be smooth as silk.

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Ok, here is the crank out of my injected 880. It was dynamically balanced many years ago. Jim

[video]https://www.youtube.com/watch?v=H-KxDZj0yA4&feature=youtu.be[/video]

Hello All
This is still going strong as a very informative thread. It began with the manufacture of the crankshaft, and all that involves, now has moved to the balancing process. A clear sequence. Please keep it going Jim, till you have at least got a running motor.

Jim, from all of the above, am I wrong in assuming that a part in perfect static may give unacceptable results at high RPM. I dont know much about balancing.
Up until now, I would have thought static was quite good.

thats what makes this so interesting, one can really learn sound stuff from this.
Bradley

B.Rad said:

Hello All
This is still going strong as a very informative thread. It began with the manufacture of the crankshaft, and all that involves, now has moved to the balancing process. A clear sequence. Please keep it going Jim, till you have at least got a running motor.

Jim, from all of the above, am I wrong in assuming that a part in perfect static may give unacceptable results at high RPM. I dont know much about balancing.
Up until now, I would have thought static was quite good.

thats what makes this so interesting, one can really learn sound stuff from this.
Bradley

Click to expand...

A crank that is in perfect static balance or balanced on a single plane balancer can be way off in dynamic balance and can cause more vibration at any speed.
Of course any balance problem is going to grow much larger at higher speed. Imbalance forces grow at the square of the RPM just like centrifugal force. Jim

I have riding friends who claim their non Commando bikes shake hard at a certain speed, then smoothen out greatly at a higher speed, say rough at 70, then smooth as glass again at 80 and on up.
I have never experienced this, other than the Norton Isolastic smoothening after 3,000 rpm where the rubber starts to work, which is a different thing again.
With any solidly mounted bike I have owned, the faster you go the more it shakes. Slow down and the shaking diminishes, seems natural and straightforward.
Is there anything to this idea that an engine is balanced for a certain speed, say 80 mph, so it will be vibratory at lower and higher speeds?

Glen

I would think components like the alt rotor, drive sprocket and timing pinion could be individually balanced. I wonder what effect torsional loads from the drive train and timing train have on the balance of the crank. It makes sense to concentrate on the fixed components and leave the variable ones out of the equation.

worntorn said:

I have riding friends who claim their non Commando bikes shake hard at a certain speed, then smoothen out greatly at a higher speed, say rough at 70, then smooth as glass again at 80 and on up.
I have never experienced this, other than the Norton Isolastic smoothening after 3,000 rpm where the rubber starts to work, which is a different thing again.
With any solidly mounted bike I have owned, the faster you go the more it shakes. Slow down and the shaking diminishes, seems natural and straightforward.
Is there anything to this idea that an engine is balanced for a certain speed, say 80 mph, so it will be vibratory at lower and higher speeds?

Glen

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Engine balance factors can be changed to change the plane of vibration. IE, 0 % balance factor would mean the engine shakes fiercely up and down but no forward to rear shake. 100% balance factor would mean the engine would shake very little up and down but it would shake fiercely forward and rear.

Any solid mount motor is going to have a certain frequency that it resonates at. When it resonates then the vibration will be amplified greatly. Many times you can reduce the tendency for a frame/engine assembly to resonate by changing the plane of vibration.

It has normally been found that a featherbed frame/engine assembly would resonate somewhere over 5000 rpm with the stock balance factor of around 65%. People who wanted to use the engine at a higher rpm would commonly raise the balance factor to around 80% so the engine's plane of vibration shifted more to the horizontal plane. This allowed them to rev the engine higher without exciting the resonance. Then the bike would shake more at lower rpm so it is a trade off.

Not all frame/engine combinations react the same as the featherbed bike. Raising the balance factor may make the resonance problem worse at high rpm in some cases. About the only way to find out is to cut and try or find someone who has a similar setup and copy it. Sometimes things as simple as handlebar bend and footpeg placement can affect the resonant frequency.

So no -you do not make the engine vibrate more or less at a certain rpm by changing the balance factor but you can certainly change how that vibration affects the bike at a certain rpm by changing the balance factor and thereby feeding the forces into the chassis in a different direction. Jim

Frank Damp and Steven Shiver and likely some others know that a good Commando should isolate pretty close to 2000 rpm giver or take 4-500 rpm. If its not rubber supported then no matter how turbine perfect the spinning parts spin the annoying hi freg. valve train buzz gets through. Oh sure the best solids are pretty darn smooth but not as completely as a decent Commando hour after hour, state after state. I rode Cdo example that hurt to ride till 33-3500, which in tight Mts or towns with cars means ya either suffered or go too fast for conditions. If it ain't smooth it ain't really a Commando so anyone waiting till 3000's, ugh, sorry you do.


CR and combustion act like taking mass on and off the counter weights or pistons for a variable BF to some degree and of course attached drives on either end tug and jerk on crank springyness. We saw the crank about to jump ship, that dynamic out of balance is not completely in vertical plane and what isn't might be passed on by the cushions.

comnoz said:

kentvander said:

It would be interesting to see you spin up a crank like in your video after it has been dynamically balance. Of course we would hope it would be smooth as silk.

Click to expand...

Ok, here is the crank out of my injected 880. It was dynamically balanced many years ago. Jim

[video]https://www.youtube.com/watch?v=H-KxDZj0yA4&feature=youtu.be[/video]

Click to expand...

Your a very brave man.... Please, Please, Please get some safety enclosure to contain a "runaway" please!!!!!!!!!!!!

What revs did your cranks reach.... 1st vid static balance only .... 2nd vid dynamic balanced

After looking at the 1st vid showing a "statically" balanced crank, which i would think should be an improvement on factory items, im nearly tooooooo scared to rev my 850 over and above minimal requirements..... FOR SURE AND CERTAIN AFTER WATCHING THESE VIDS I WILL BE INVESTING IN DYNAMIC BALANCING, NO QUESTION!

Its scary to me to think that some factory issue crank would be soooooo unbalanced and some ask why they vibrate. Its a bit of a "no brainer" now.. thanks for sharing this enlightening "revelation" to us..

olChris said:

comnoz said:

kentvander said:

It would be interesting to see you spin up a crank like in your video after it has been dynamically balance. Of course we would hope it would be smooth as silk.

Click to expand...

Ok, here is the crank out of my injected 880. It was dynamically balanced many years ago. Jim

[video]https://www.youtube.com/watch?v=H-KxDZj0yA4&feature=youtu.be[/video]

Click to expand...

Your a very brave man.... Please, Please, Please get some safety enclosure to contain a "runaway" please!!!!!!!!!!!!

What revs did your cranks reach.... 1st vid static balance only .... 2nd vid dynamic balanced

After looking at the 1st vid showing a "statically" balanced crank, which i would think should be an improvement on factory items, im nearly tooooooo scared to rev my 850 over and above minimal requirements..... FOR SURE AND CERTAIN AFTER WATCHING THESE VIDS I WILL BE INVESTING IN DYNAMIC BALANCING, NO QUESTION!

Its scary to me to think that some factory issue crank would be soooooo unbalanced and some ask why they vibrate. Its a bit of a "no brainer" now.. thanks for sharing this enlightening "revelation" to us..

Click to expand...

I'm not normally much of an 'elf n safety zealot, but I recall that the man behind CMA (makers of 8 leading shoe front brakes and cast wheels) was killed by wheel ejecting itself from the lathe...