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Engine mount rubbers - YAK-50

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gord(at)thedampub.ca
Guest

Posted: Thu Jul 13, 2017 4:07 am Post subject: Engine mount rubbers - YAK-50

We just installed a zero’d M-13PF with Barrett Pistons which dyno'd at 435 HP on my YAK 50.   Performance is much enhanced however we have just found some engine mount rubbers  are being torn up because the metal sleeve is moving and cutting the rubber.  The airplane is being flown under the G limits however during the air show sequence I am sometimes seeing +8 and -5 G.   We never had this problem with the old 360 HP engine.  We have a new set being installed in the next few days which should yield more information.  Does anyone have experience in this area?  Thinking of bonding the sleeve to the rubber to prevent the sleeve movement.  Thanks in advance.  Gord

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Dawg

Joined: 19 May 2013
Posts: 355

Posted: Thu Jul 13, 2017 4:48 am Post subject: Engine mount rubbers - YAK-50

at our age, 8 g is to painful. -5 is worse. My suggestion, stop doing that. Problem solved.



 	  Quote: 	
		   On Jul 13, 2017, at 21:04, Gordon Price <gord(at)thedampub.ca> wrote:

 

 

 

 

 We just installed a zero’d M-13PF with Barrett Pistons which dyno'd at 435 HP on my YAK 50.   Performance is much enhanced however we have just found some engine mount rubbers  are being torn up because the metal sleeve is moving and cutting the rubber.  The airplane is being flown under the G limits however during the air show sequence I am sometimes seeing +8 and -5 G.   We never had this problem with the old 360 HP engine.  We have a new set being installed in the next few days which should yield more information.  Does anyone have experience in this area?  Thinking of bonding the sleeve to the rubber to prevent the sleeve movement.  Thanks in advance.  Gord

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_________________
Dawg

JL2A

Joined: 07 Apr 2015
Posts: 113
Location: Australia

Posted: Sat Aug 05, 2017 3:41 am Post subject: Re: Engine mount rubbers - YAK-50

We have experienced poor longevity from the rubber mounts even in the CJ6. We installed a set that was made from a type of urethane that is still soft enough yet does not perish when constantly soaked in oil.



Since then we have installed 5-6 sets of the red urethane mounts, the first set are still fine, something like 1000 hours and 4-5 years later.



I'm just waiting on the spec sheet of the material to send to Doug Sapp. A set made here in Australia is about $300 or thereabouts

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GeorgeCoy

Joined: 02 Dec 2010
Posts: 310

Posted: Sat Aug 05, 2017 8:31 am Post subject: Engine mount rubbers - YAK-50

Hey Guys, I am not sure where the problem is with the good old rubber

mounts. Worked pretty well for the last 60 years or so.

I suspect many or the problems are caused by self-induced.



First, rubber has a shelf life as well as a use life. If you are installing

"New" rubber mounts that were produced in 1994, then you will have problems.

Second, the M14P instillation calls for 14 of 506400-05 mounts  and  2 of

the 5064000-35 mount.  (the -35 parts go behind the magnetos and have a

slightly smaller metal bonded face to prevent interference with the

magnetos). It also calls for a specific washer (50640002) by the mount face

that must be installed with the curved face to the mount. There is a second

oblong washer (506400-03) under other end of the mount assembly. 



Third, there is a specific dimension  (34.6 mm) between the face of the

motor mount and the top of the -35 washer under the nut end of the assembly.

The nuts are tightened to a dimension , not a specific torque.  Over

tightening and or under tightening will cause problems as well.  



We offer new rubber mounts made within the last year, as wells the proper

washers.  These  mount sets are priced competitively.  



I am not a big fan of the DRE ( Direct Rectal Extraction) engineering

method, so tend to stick with the original system that has worked well.  



You can find an instillation diagram with all the part numbers on our

website.

George Coy

MotorstarNA

714 Airport Rd.

Swanton VT 05488

802-868-5633 off

802-363-5782 cell

802-868-6632 Fax

george.coy(at)gmail.com

http://motorstarna.com/

SKYPE george.coy

--

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j.mevis(at)computer.org
Guest

Posted: Sat Aug 05, 2017 11:31 pm Post subject: Engine mount rubbers - YAK-50

Thanks George,



Actually we never had any problems with the original mounts either, not

even with an M14R bolted on the plane.



Good website!



Jan



On 05/08/2017, 18:29, "George S. Coy" <owner-yak-list-server(at)matronics.com

on behalf of george.coy(at)gmail.com> wrote:



[quote]



Hey Guys, I am not sure where the problem is with the good old rubber

mounts. Worked pretty well for the last 60 years or so.

I suspect many or the problems are caused by self-induced.



First, rubber has a shelf life as well as a use life. If you are

installing

"New" rubber mounts that were produced in 1994, then you will have

problems.

Second, the M14P instillation calls for 14 of 506400-05 mounts  and  2 of

the 5064000-35 mount.  (the -35 parts go behind the magnetos and have a

slightly smaller metal bonded face to prevent interference with the

magnetos). It also calls for a specific washer (50640002) by the mount

face

that must be installed with the curved face to the mount. There is a

second

oblong washer (506400-03) under other end of the mount assembly.



Third, there is a specific dimension  (34.6 mm) between the face of the

motor mount and the top of the -35 washer under the nut end of the

assembly.

The nuts are tightened to a dimension , not a specific torque.  Over

tightening and or under tightening will cause problems as well.



We offer new rubber mounts made within the last year, as wells the proper

washers.  These  mount sets are priced competitively.



I am not a big fan of the DRE ( Direct Rectal Extraction) engineering

method, so tend to stick with the original system that has worked well.



You can find an instillation diagram with all the part numbers on our

website.

George Coy

MotorstarNA

714 Airport Rd.

Swanton VT 05488

802-868-5633 off

802-363-5782 cell

802-868-6632 Fax

george.coy(at)gmail.com

http://motorstarna.com/

SKYPE george.coy

--

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