Dynamically balanced crank

Need advice on which oil to use or which tyre best suits you? Share your topic and get help here.
Post Reply
User avatar
sirch345
Site Admin
Posts: 22108
Joined: Mon Aug 25, 2003 10:35 pm
Location: The West Country.

Dynamically balanced crank

Post by sirch345 »

Could someone explain to me what the difference is between a balanced crank and a dynamically balanced crank or is it the same thing just with a fancy name ?
Chris.
User avatar
firestorm996
Posts: 617
Joined: Tue Jul 16, 2002 10:15 am
Location: Oop North
Contact:

Post by firestorm996 »

I dunno what the difference is, but my bike's got a dynamically balanced crank. :wink2

Just thought I'd share :biggrin

Del should be able to shed more light on this.
Firestorm996
'98 VTR in black - road whore - track bitch
User avatar
delmeekc
Posts: 744
Joined: Mon Jul 22, 2002 8:34 pm
Location: BlueWater

Post by delmeekc »

Errr, it's more expensive :? to get it dynamically balanced.

Dynamic is better so I have been told as (as is Firestorm996's VTR - one of my engines) the pistons/rings/small end and rods and big-end shells are all weight matched. Then a weight is made to the exact weight of the above. This is fixed to the crank pin, evething else is put on too, both end of the crank and then it is all balanced to with in 0.02oz (think it's 0.02) whilst spinning and all together, ker ching ££££

I'll ask him when I see him next and get the full story.

Before I get it done I did find a website that explained it all and nascar engines are balanced dynamically as above.

Del.
User avatar
sirch345
Site Admin
Posts: 22108
Joined: Mon Aug 25, 2003 10:35 pm
Location: The West Country.

Post by sirch345 »

Thanks Del for the info.

Firestorm 996 I knew someone on here had one.

cheers Chris.
User avatar
BazilD
Posts: 33
Joined: Sat Sep 27, 2003 7:06 pm
Location: Brisbane - Arsetralia

Post by BazilD »

Sirch345: to answer your question I guess basically, you are talking about the same thing, a balanced crank.

There are two balancing methods used for various purposes:
1. Static balancing - usually used on large slow rotating objects, such as large propellers for aircraft. Heavier blade falls to the lowest point etc etc.
2. Dynamic Balancing - where the component is rotated and the amount of unbalance is measured on planes.

My guess is it would be impossible to statically balance a V crankshaft, incidentally, it's quite difficult to dynamic balance a V Crankshaft too, as Del correctly said a mass is attached to the big ends which is a proportion of the weight of the con rod, small end, piston & rings. The proportion depends upon the angle of the V.
An inline engine it's just a case of balancing the crank on it's own and removing material from the heavier side of the crank.

I hope that helps.
BazilD
Sometimes you're the bug, and sometimes you're the windscreen!
User avatar
sirch345
Site Admin
Posts: 22108
Joined: Mon Aug 25, 2003 10:35 pm
Location: The West Country.

Post by sirch345 »

Hi BazilD
Thanks for the info
cheers Chris.
Post Reply