[NSRCA-discussion] Nose Ring

[Dean Pappas]

Hi Jim,
You weren't sleeping ... just that the whole story is fairly complicated. 
Let's say there are three vibrations being sourced from the engine: an up-down one, a side-to-side one, and a torsional one.
In these enlightened times we have learned that the torsional one is the biggie.
The other two are small by comparison.
The axis, around which the rotational inertia of the engine is a minimum, is at some funky angle to the centerline of the crankshaft.
That axis probably runs from just below the middle of the cylinder to a point just under the engine, below the carburettor.
The last sentence means that any movement in any one axis, will couple to create movements in any other axes in which the engine is free to move. That's the cause of crazy nose wobble without a nosering. 
So we make a big tradeoff: the engine is held fairly stiifly from wobbling the crankshaft, which attenuates the cross couples.
The cross couples are real bad, and even a tiny amount of play in the nose ring lets any movement turn into more shake at more different frequencies (RPMs) than if the nose isn't allowed to move at all. 
Not to mention Dave 's very good point about another high frequency content banging against the play in the nose ring.
But the biggest reason I use a friction fit, rather than a mere tight fit is not for rotational forces, but to dissipate the energy when the engine is rotating at its highest degrees per second, at the idle resonance.
At full throttle, the peak rotational degrees per second is actually lower than at idle, because the small time per revolution prevents the engine from having enough tim to accelerate to any appreciable rotational speed.
Energy absorbtive damping also lowers the resonant RPM, so that with a good Hyde or Speedmax mount, you might end up with a resonance that is below your lowest practical idle.
Then, you win!
later,
Dean
 

Dean Pappas 
Sr. Design Engineer 
Kodeos Communications 
111 Corporate Blvd. 
South Plainfield, N.J. 07080 
(908) 222-7817 phone 
(908) 222-2392 fax 
d.pappas at kodeos.com 

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of jivey61 at bellsouth.net
Sent: Thursday, December 22, 2005 10:50 AM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Nose Ring


But Dean!
My learning of this, was that, the torsional forces are absorbed by the main mount,whatever configuration and the nose ring is used to keep the crankshaft from wobbling up-dn,left-right.It seems that a tight nose ring transfers  more of the bang to the fuse and creates more noise.  I guess some mounts need  help with the torsional forces by tightening the nose ring.
Was I sleeping in class?
 
Jim Ivey

----- Original Message ----- 
From: Dean  <mailto:d.pappas at kodeos.com> Pappas 
To: NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org>  
Sent: Thursday, December 22, 2005 10:00 AM
Subject: RE: [NSRCA-discussion] Nose Ring

Hi,
A tight nose ring offers some friction damping to the large movements that only happen at idle.
My typical soft mount actually uses a clamping nosering, to dial inn that friction loss.
A Merry Bah Humbug to all! (vbg)
        Dean
 

Dean Pappas 
Sr. Design Engineer 
Kodeos Communications 
111 Corporate Blvd. 
South Plainfield, N.J. 07080 
(908) 222-7817 phone 
(908) 222-2392 fax 
d.pappas at kodeos.com 

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of Tomc at buyrc.com
Sent: Wednesday, December 21, 2005 7:49 PM
To: 'NSRCA Mailing List'
Subject: RE: [NSRCA-discussion] Nose Ring



I used the new silver one and had to remove the hub to get it to slide on. It's very tight, but I think works better than the looser one.

 


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From: nsrca-discussion-bounces at lists.nsrca.org [mailto:nsrca-discussion-bounces at lists.nsrca.org] On Behalf Of jivey61 at bellsouth.net
Sent: Wednesday, December 21, 2005 1:25 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] Nose Ring

 

Dave

 Either one will work.I would prefer a little loose.The gold nose ring isn't available any more. That is reason to sell the new solid alum. version.  Actually I run a Webra 145 with no nose ring The AR mount is stiff enough to do this with a 2 S.

 

Jim Ivey

----- Original Message ----- 

From: Dave Smith <mailto:davidsmith at ns.sympatico.ca>  

To: nsrca-discussion at lists.nsrca.org 

Sent: Wednesday, December 21, 2005 3:06 PM

Subject: [NSRCA-discussion] Nose Ring

 

I think I sent the following to the wrong address. If so,my apologies.

 

I have a Central Hobbies nose ring (the one that is silver coloured and tapped for mounting bolts).

It fits my OS 140 tightly.

 

I also have the older gold coloured nose ring that has a very slight amount of clearance between it and the engine crankcase

Engine mount is a Hyde AR.

 

I don't think the tight nose ring is the way to go,but I might be wrong.

Anyone use this tight ring?   Opinions please.

 

Thanks,,,,,,Dave


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