The type A mount although will give you better vibration damping than the DB mount it has the same problems with thrust line change during flight......Pulling or pushing corners, changes in throttle setting as in any change in throttle setting whether its gunning it to full or moving it up 2 clicks from half throttle.....the thrust line will change slightly.....Its because the forces are allowed to work in a direction not radial to the crank shaft......

If the front of the motor is held in place the amount of non radial force is minimized by the flex of the airframe...and is not independent of the airframe.....Any motor that is not supported solid enough and allowed to flex independent of the nose of the plane will cause head aches in the trim process.....


There are other solutions......the type AR are the normal standard mounts with a fuse mounted nose ring...You could install rail supports that extend out on the sides of the mount from the engine box to support the nose ring.

or

The type ARI stands for "Ring Incorporated" meaning its part of the motor mount....But you have to have a pretty stiff firewall to support everything from the motor mount and firewall.....I would venture to say at least 3/16" aircraft ply firewall....for this mount...

The just Type "A" with no nose ring are good on sport type models but without a nose ring the thrust line will change during flight...as you pull or push the thrust line will move with G forces as well as gyroscopic forces from the rotational motion of the prop.....As the motors become bigger ( 60's and above this becomes an issue because the props are bigger and there is more of a gyroscopic effect...larger diameter, more mass. ect ect.

The YS engines have more kick actually all the 4 strokes and thus this kick will also cause more movement.


Then you can go lighter with the AR (A) and ARI (A) the (A) after stands for (Aluminum beams) These (A) light versions tend to be stiffer a little bit because of the isolator shape and tension on the rubber. But stiffer is not really better......I think the motors should be allowed to move and just support your pipe and header so it can move too.....

So the Type A isolator has many different forms....A by itself is no nose ring...These are stiffer and a wider foot print to help stop some of the thrust line changes...but not eliminate it.

The AR and AR (A) mount is the most efficient both weight wise and structure wise....


The ARI and ARI (A) work great in planes that have a cowling like the Focus or other ARFs....But you may need to beef up the firewall like add some 1/8" aircraft ply behind it to get it to at least 3/16" and its better at 1/4" ply......Then use some triangle balsa to make sure its in good and stiff...


So the type A's are for beam mount engines....or the most common types....


Merle also makes the Type B mounts for Backplate mounted setups...these are most common the big mounts like the gas motors they mount to the backplates of the motors and again he has some that nose ring and some that don't



The best setup for pattern and IMAC stuff is a nose ring and the reason is the thrust line stays fixed and held by the nose ring.


Its tougher to fly a plane with the motor moving around in it.


Troy Newman