Changing Engine Orientation
 

Hi all,

I have recently purchased a Groovy 3A (ARF) from The World Models and I plan to put a TT PRO 46 in it. The engine orientation in the instruction manual is shown to be inverted but I would want to have it sideways (90 deg). The holes for the engine mounts are already drilled in the firewall. I have heard there is a "template" technique to achieve this. I would request somebody here to guide me go about it (changing the orientation). What do I need to do and what are the "caution points"?

Thanks

RE: Changing Engine Orientation
 

Many of the World Models ARFs come with a mount that allows you to orient the engine at any of the multiple of 90 degree positions you desire.

RE: Changing Engine Orientation
 

That was fast, Chuck! Thanks!

But how do I find out if the same holes in the firewall would do? I mean I can screw on the engine mount at 90 degrees also with no problems - I tried it. But how do I know whether that would change the thrust line or not. The instruction manual is silent on this "universal" mounting feature.

RE: Changing Engine Orientation
 

Although I don't know that particular plane, usually rotating the engine mount will not change the thrust line at all. If it does, it will only be a fraction of an inch and won't affect the way the plane flys.

Dr.1

RE: Changing Engine Orientation
 

Determine the thrust-line of the design and mark both the thrust-line and centerline on the firewall (thrust-line = up and down location and centerline = port and starboard location. This should end up looking like the cross hairs in a rifle scope. Make a hole pattern template of some stiff material that matches the existing hole pattern on the firewall (I like aluminum as it will keep the drill from wondering during drilling). If needed, drill out the existing holes so dowels can be inserted to fill them in and sand flush. Rotate the pattern template the way you want, align with cross hairs on the firewall and drill new holes.

You will need to raise the fuel tank to accommodate the new-higher carb. level.

I agree with your decision to do this! Why manufacturers have decided to design airplanes with inverted engine installations is beyond my comprehension!! Yes, they seem to work better for 4 strokes, however, I still think it makes life more complicated!

RE: Changing Engine Orientation
 

rajeev,

i'm not sure if I understood exactly what you want to do, BUT if you just want to "test" IF the thrust line will be affected by changing the mount orientation you can do this:

1- place the engine on the mount but with the shaft (where the prop goes) facing backwards almost touching the firewall, and secure it using a drop of CA or some zip-ties
2- stick a piece of paper on the firewall
3- mark the place in the paper-on-firewall where the shaft touches, maybe draw a circle with a pen around the shaft on the paper
4- remove the screws that hold the engine mount to the firewall and rotate it to the position you want to achieve
5- see how different the position of the shaft is in relation to the circle you draw around it on step 3

if there is no change then go ahead an mount it in that position and save you the drilling of new holes

Hope this helps :)

Joe :D

RE: Changing Engine Orientation
 

May need to raise the tank, may not. It's quite common for the tanks to be too high for inverted engines. Mounting it sideways may actually put the carb at the right position.

As for why engines would be mounted inverted, perhaps for those of us who don't like seeing a cylinder head sticking out of the cowl. An inverted mount of a 2 stroke can make it less obvious than sideways mounting.

RE: Changing Engine Orientation
 

I stand corrected! I should have said: You "MAY" need to raise the fuel tank to accommodate the new-higher carb. level.

I guess seeing the cylinder head sticking out of a sport airplane doesn't bother me at all! As a matter-of-fact, I prefer sport airplanes that have the whole frigging engine sitting out in the breeze, easy to work on and inspect for problems!

RE: Changing Engine Orientation
 

I won't say I prefer it, but I certainly understand the value. The Uproar I put together last year was a nice change from all of the other cowled in engines.

RE: Changing Engine Orientation
 

You guys are a legend. Fantastic responses. Thanks guys!