[R.Sonnel]

I mounted a CRCC Pro 26cc gas engine on a Twist 150. (cut off the cheaks and reinforced the firewall). This is my first gas airplane. I new there was going to be more vibration than glow. After first flight,flew great lot's of power, I went home and installed steel washers with hard rubber backing on one end of the stand off's (closest to engine)and a very hard dense rubber shim at the firewall.The vibration level was way less than before.I would guestemate 50% less vibration, give or take a little. My question is, do other people with gas engines use any kind of rubber dampers to lessen vibration.

Thanks.

[RAMJET]

be carful putting anything under the motor mounts as this will let the motor twist and apply uneven force to the lugs on the motor & may cause breakage .if you want to rubber mount ,first mount the motor and its standoffs solid to a dummy firewall & rubber mount that to the present firewall .you could use a 1/8 " 3/16 " thick piece of aluminum sheet metal and bolt it to the motor & drill another set of holes to mount it to the firewall ,put rubber between the 2 firewalls & behind the bolt heads inside the plane .(to answer your question it is rare to rubber mount a motor that small )I think when you fly gas you get used to seeing the vibration (check the prop balance though) .Roger

[Nev]

OPTION 1
ENGINE VIBRATION ISOLATORS $20.95 from Bennett http://www.bennettbuilt.com/page4.htm
They are quite large so you need space...I have a set with spare rubbers if you want you buy them off me brand new never used.


OPTION 2
Large Engine Isolation Mount from Great Planes
http://www.greatplanes.com/accys/gpmm1080.html


I was advised against any form of rubber mounting...as there have been cases where the rubber can apparently occilate out of sync with the engine vibration causing a worse effect. I still want to try it though. So keep us posted.

[Luke Planemaker]

I had found and saved this pic, thinking I might try something similar. Might give you some ideas. Maybe rubber instead of springs.

[3dflyer]

another thing that is missed is the needle settings on the carb.i have come across this from personal expierence ,until the motor is completely broken in you will experience some vibrations even with the prop being balanced.after the engine is broken in by adjusting the lowend needle in will cause the motor to smooth out.also when breaking in a new engine they are run in rich oil mixture until broken in .once you have switched over to a leaner oil/fuel mix after break in than you will probably have to tweak the needles abit and by doing that usally you will have a smoother running engine.just my 2 cnts.

[g-manz35]

Your CRCC is probably EI, but if you are running a mag engine you will always run a little rougher at idle due to the advanced ignition. My conversion smothened out a lot when I converted it to EI especially at low idle.

I should add that I'm talking about auto advance EI.

Cheers. George

I have soft mounted glow engines since the early 90's with great success. About 10 years ago I started dabbling in gas engines and figured that IF I soft mounted glow you MUST soft mount gas. I tried everything, the Bennett mounts, Lord mounts, rubber this, rubber that and had nothing but terrible experiences. Broken cowls, cracked canopies, loose covering, broken mufflers.

All along I kept reading and hearing DO NOT soft mount a gasser. Their crazy I said but after years of frustration I finally gave in and mounted them HARD to the firewall. Guess what ? All my problems went away.

As already mentioned, proper needle settings are MUCH more important than any mount you may try. A lot of guys are afraid to move the needle valves. I hear time and again " the needles are still factory set". I have never ran a new engine for over 1 min. without making some kind of adjustments. After all most of these things are set up in climates totally different than the end users climate.

Anyway that's my .02 worth. I'm not perfect or a know it all but have learned a lot through sweat and frustration.

[R.Sonnel]

Originally Posted by Don M.

I have soft mounted glow engines since the early 90's with great success. About 10 years ago I started dabbling in gas engines and figured that IF I soft mounted glow you MUST soft mount gas. I tried everything, the Bennett mounts, Lord mounts, rubber this, rubber that and had nothing but terrible experiences. Broken cowls, cracked canopies, loose covering, broken mufflers.

All along I kept reading and hearing DO NOT soft mount a gasser. Their crazy I said but after years of frustration I finally gave in and mounted them HARD to the firewall. Guess what ? All my problems went away.

As already mentioned, proper needle settings are MUCH more important than any mount you may try. A lot of guys are afraid to move the needle valves. I hear time and again " the needles are still factory set". I have never ran a new engine for over 1 min. without making some kind of adjustments. After all most of these things are set up in climates totally different than the end users climate.

Anyway that's my .02 worth. I'm not perfect or a know it all but have learned a lot through sweat and frustration.

Hi Don,
Thanks to everyone for all the imput. I love these informative threads.(no verbal abuse)It really helps an intermediate modeller like myself. I will go with the consensus, no rubber mounts.

Thanks again.

Hey Bob, I just realized who you were. How's the starter working ? I had a guy at the field the other day with a 50cc gasser he couldn't start. He asked if I had a starter that would turn it over. I just have a little glow starter that I use a 3S lipo on. I remembered that I had a 6S ( 25 volt ) lipo battery with me so I said let's try it. Well it started that 50cc like a .61, couldn't believe it.

Then smoke started coming out of Buddies hand and my starter wires were on fire Fixed it up as good as new when I got home. We could have used that big Dynatron

Set that gasser up right on the needles, bolt her fast to the firewall and you'll never look back. You just learned something in a couple of days that took me years ( I'm stubborn )

[R.Sonnel]

Originally Posted by Don M.

Hey Bob, I just realized who you were. How's the starter working ? I had a guy at the field the other day with a 50cc gasser he couldn't start. He asked if I had a starter that would turn it over. I just have a little glow starter that I use a 3S lipo on. I remembered that I had a 6S ( 25 volt ) lipo battery with me so I said let's try it. Well it started that 50cc like a .61, couldn't believe it.

Then smoke started coming out of Buddies hand and my starter wires were on fire Fixed it up as good as new when I got home. We could have used that big Dynatron

Set that gasser up right on the needles, bolt her fast to the firewall and you'll never look back. You just learned something in a couple of days that took me years ( I'm stubborn )

Hi Don,

The starter works great. Man,I shouldn't laugh but I can imagine the look on your faces when the smoke was comming from the starer, and the wires caught fire!! BTW the little 26cc is a little power house. Pulled the Twist 150 5 feet down the runway and 90 deg. straight up.

P.S Still laughing. Sorry Don.