Re: Let's Talk About Adding Weight to an HPI Inner Rotor

Matt Smith /
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I have a theory about things going wrong with crankshafts with lightweight ignitions. It has to do with Torsional Vibration.

By swapping the stock flywheel for the much lighter mini-rotor ignition, there is greatly reduced inertial dampening on the ignition side of the crank. You also have the force impulses from the piston/combustion increasing in both frequency and amplitude due to your more powerful and higher RPM setups.

Every time you get a pulse from the cylinder, you are winding/twisting up the crankshaft in between the clutch side and the crank cheeks like a torsional spring. Then it unwinds. Back and forth. At 10,000+ rpm. When you lighten the ignition side, you take away dampening and create a more asymmetric reaction on each end of the crankshaft.

I deal with this on propeller shaft installations on boats. For every boat we design we have an outside company evaluate all the components in the drive train (Propeller, Shaft, Engine, PTO Items, Etc.) They look at the engine impulses driving everything as a system of torsional springs. Looking for harmonics especially. There is a lot of Finite Element Analysis and I only read the reports, but we just had a boat that we had to add a mass disk to, for this very reason. Without it they were predicting that we would have destroyed the drive shaft in no time.

My prescription, add rotational mass back to the ignition. It's not weight, it has to do with rotational inertia. You may not have to add all of it back.

http://www.livephysics.com/physical-constants/mechanics-pc/moment-inertia-uniform-objects/

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Subject Written By Posted
  Let's Talk About Adding Weight to an HPI Inner RotorTopic by: Dave Steele Dave Steele 06/27/14 09:26AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Flagrant - Flagrant - 06/27/14 10:52AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Ryan . Ryan . 06/27/14 11:15AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Jr. Want A Knobby Jr. Want A Knobby 06/27/14 01:41PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Dave Steele Dave Steele 06/27/14 04:28PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: GET REALIZED! BE HERE NOW! GET REALIZED! BE HERE NOW! 06/30/14 06:59PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: *.* HONDA *.* HONDA 06/30/14 07:39PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: #CrazyWayne™ rocks. #CrazyWayne #CrazyWayne™ rocks. #CrazyWayne 06/30/14 07:57PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: #CrazyWayne™ rocks. #CrazyWayne #CrazyWayne™ rocks. #CrazyWayne 06/30/14 07:52PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Flagrant - Flagrant - 06/30/14 10:11PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: #CrazyWayne™ rocks. #CrazyWayne #CrazyWayne™ rocks. #CrazyWayne 06/30/14 10:41PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: #CrazyWayne™ rocks. #CrazyWayne #CrazyWayne™ rocks. #CrazyWayne 07/01/14 03:32AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 07/31/14 12:45AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Daniel '' Daniel '' 07/31/14 01:46AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 07/31/14 02:02AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: #CrazyWayne™ rocks. #CrazyWayne #CrazyWayne™ rocks. #CrazyWayne 07/31/14 02:05AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Matt Smith Matt Smith 07/31/14 01:47PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Michael Mike Naz Michael Mike Naz 07/31/14 02:54AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Jesse Stephenson Jesse Stephenson 07/31/14 03:09AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: #CrazyWayne™ rocks. #CrazyWayne #CrazyWayne™ rocks. #CrazyWayne 07/31/14 03:17AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Ryan N. Ryan N. 07/31/14 01:08PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: SABAT! andDestroy SABAT! andDestroy 07/31/14 04:15AM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 07/31/14 12:38PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Dave Steele Dave Steele 07/31/14 12:41PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Big Al's Moped Shop Big Al's Moped Shop 07/31/14 01:06PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 07/31/14 01:17PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Big Al's Moped Shop Big Al's Moped Shop 07/31/14 01:27PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 07/31/14 02:59PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 07/31/14 01:42PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 07/31/14 01:53PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Dave Steele Dave Steele 07/31/14 02:37PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Dave Steele Dave Steele 09/05/14 02:35PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 09/05/14 03:04PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Dave Steele Dave Steele 09/05/14 03:27PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 09/05/14 03:43PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Big Al's Moped Shop Big Al's Moped Shop 09/05/14 04:12PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 09/05/14 04:24PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Dave Steele Dave Steele 09/05/14 04:34PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 10/13/14 03:20PM
  Re: Let's Talk About Adding Weight to an HPI Inner RotorRe: Marc Friedman Marc Friedman 09/05/14 06:25PM

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