Fw: TEST- now motor mount Poll

[Bob Pastorello]

Have to throw in a comment or two...
    1.  Used the Hanson RotoRMount in 1997-98...good mount, lots of adjustability, and worked well - IF - you kept the center bolt snubber in the firewall snug enough, and maintained the tubing as it wore pretty quickly.  For me, using it with YS 1.40's at the time, it needed frequent adjustment.
    2.   Did my own anti-rotational mount based on a sketch someone gave me at a contest once, lots of iterations of that principle, nothing really new....except ....  the Nose Ring...

As some have already said - the Nose Ring, in my experience also, is a MAJOR contributor to noise and wear.  If too snug, way too much vibration is transmitted to fuse.  You can feel it when holding the nose of the fuse during start/run up.  4C are bad, but the big 2 strokes pound like CRAZY and the lower the idle, the greater the impulse, the higher the amplitude of the vibration, although the frequency is lower.  The 2C hits nearly as hard, and TWICE as often as a similar sized 4C, and this is actually less vibration/impulse to deal with.  The total vibration issue is one of frequency of impulse, duration of impulse, and AMPLITUDE of impulse.  It's really a "cut and try" kind of issue to solve.

One of the most productive experiments over a period of several years was discovering that the nose ring is probably much more important than we think.  I've used a variety of grommets, bushings, and settled on a dual-concave 3/16" thick O ring from McMaster Carr.  Sandwiched between 1/16" ply plates, and removable, it allows easy replacement.

I also can testify that the MK Mount - again, in my limited experience - probably is something that is MUCH better left at the seller's pegboard, rather than in our airplanes.

Bob Pastorello, Oklahoma
NSRCA 199, AMA 46373
rcaerobob at cox.net
www.rcaerobats.net


  ----- Original Message ----- 
  From: Wayne Galligan 
  To: discussion at nsrca.org 
  Sent: Saturday, January 03, 2004 9:10 AM
  Subject: Re: TEST- now motor mount Poll


  Firing stroke impulse, inertia from moving parts, size of components(prop, piston,square of stroke)  all have an effect on vibration.  I have been trying a few things in search of that all elusive vibration free setup. Does a 3 blade prop run smoother then a 2 blade prop? I have been making nose rings out of 1/8" urethane sandwiched between 1/32" ply.  The urethane holds the nose in place without having to have too snug of a fit at the crank end and it so far doesn't seem to wear as quickly as lined nose rings.  On my Entropy with an OS 1.40 is super smooth and quite at idle and through most of the rpm range.  My Aries with the Mintor 1.70 bangs like a 4-stroke at idle and there was a noticeable reduction in vibration when I switched the nose rings.  I make a home made soft mount using Bob P. instructions and it weights about 3.3 oz and handles the Mintor quite well. 

  you can view it at this link

  http://www.rcuniverse.com/gallery/galleryCat.cfm.cfm?memberID=6463&CFID=862285&CFTOKEN=3b3a471-7dc5463c-19d1-4704-bd2f-605a2511e969

  Wayne G.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.f3a.us/pipermail/nsrca-discussion/attachments/20040103/b96cc57d/attachment.html