[NSRCA-discussion] Soft Mounts (Beam)

[Paul LaChance]

Lance,

The bolt does not thread into the rubber on the mount I have.  Bolts go through the runner and have nuts on the other side,  A spacer keeps you from crushing the rubber too much and has washers to prevent the bolt from pulling through.  Maybe there are other tyles, but this is the only type I have seen.  It was a true DB VibraDamp beem style mount.  This was the second one I had used through the years.  The biggest thing I do not like about them is you need to keep the rear of the enginge centered.  Almost need a nose ring type device in the rear to keep the engine centered in the rear just as you do in the front.

Paul
  ----- Original Message ----- 
  From: Lance Van Nostrand 
  To: NSRCA Mailing List 
  Sent: Saturday, December 15, 2007 11:06 AM
  Subject: Re: [NSRCA-discussion] Soft Mounts (Beam)


  Sorry to be naive but a bolt screwed into rubber will not easily pull out?  The DB isolators have an embedded blind nut in them.

  I've been using isolators from mcMaster that are virtually the same as the DB ones.  McMaster has the advantage of offering male/male fem/fem or the male/fem we are used to.

  --Lance

    ----- Original Message ----- 
    From: Paul LaChance 
    To: NSRCA Mailing List 
    Sent: Friday, December 14, 2007 6:37 PM
    Subject: Re: [NSRCA-discussion] Soft Mounts (Beam)


    Lance and others interested,

    Find a bet that is bigger than the isolator in all direction.  Mine was for the blade drive on a riding mower.  I cut the pieces to the original dimentions using a scroll saw.  The I drilled the holes in the rubber with a small drill bit and worked my way up to the right size.  It takes SEVERAL times drilling with the correct size drill bit to actually open the hole properly.  The rubber will keep trying to strech instead of letting the bit drill cleanly.  Then, mount as usual.  I have used these home made isolator for about 20 flights with no sign of wear.  Until that time they were cracking or turning into gummy bears about 1 a day, so every 4 days of flying required all 4 isolators to be replaced.  

    Strangly I never had this problem about 10 years ago.  I do not know if they changed the rubber they were made from, but the new rubber does not last like the old rubber did.  Also the ones for World Engines brand mounts work but are VERY hard and stiff.  They shook the plane terribly and had to be removed after 2 flights.  

    Paul 
      ----- Original Message ----- 
      From: Lance Van Nostrand 
      To: NSRCA Mailing List 
      Sent: Friday, December 14, 2007 7:28 PM
      Subject: Re: [NSRCA-discussion] Soft Mounts (Beam)


      Paul, intersted in more details of how you fabricated an isolator from a belt.

      Still, anyone melting vulcanized rubber has some serious cooling problems.

      --Lance

        ----- Original Message ----- 
        From: Paul LaChance 
        To: NSRCA Mailing List 
        Sent: Friday, December 14, 2007 6:10 PM
        Subject: Re: [NSRCA-discussion] Soft Mounts (Beam)


        I had the same thing happen.  Even a new set just purchased did the same thing.  I ended up making my own out of a belt for a riding mower.  The belt was $10 and you could probably make about 100 isolators out of it.  The good thing is it is designed to take the heat and be break resistant.  The cloth molded into it makes it almost impossible to tear.  Just make sure you cut the piece to shape and drill the holes accurately.  I used the home made isolators at the Triple Tree contest this year.  Give it a try.  It seemed to have the damping as the priginal isolators.

        Paul
          ----- Original Message ----- 
          From: Bill Thompson 
          To: nsrca-discussion at lists.nsrca.org 
          Sent: Friday, December 14, 2007 6:47 PM
          Subject: [NSRCA-discussion] Soft Mounts (Beam)


          Has anyone had the rubber for these mounts soften and melt. This is the second time in the last year it happened.The mounts are MK using Dave Brown VibaDamp 4/C Isolators.
          BillT


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