Engine mounting question
 

Hi all!

I'm finally getting my TH Kaos 40 ready to go. Basic assembly is complete save for mounting the engine. I'm using an OS 46 AX and the one-piece metal motor mount that was included with the Kaos. This mount is the kind where the engine is held down by a flat bar held over the engine flanges with two bolts which go through nuts on the bottom of the mount.

The problem is that the needle valve covers access to the engine mounting bolt directly underneath it. This happens when I try to balance having the required clearance between the prop and the leading edge of the cheeks with using the existing holes for the flat bar holding the engine to the mount. I tried swapping the valve to vertical but it's still in the way. So I figure I've got a few options:

1. Tighten the obstructed bolt as best I can and go with it. I don't like this idea much.

2. Drill holes in the mount for new bolts that would pass directly through the holes in the engine flanges. This would ditch the flat bar arrangement entirely.

3. Use a different mount.


Thoughts?


J

RE: Engine mounting question
 

Not sure of your thread size, but maybe you could replace the obstructed screw with a cap head screw? Many hardware stores carry small standard size cap head screws, you can tighten these screws at an angle with an alex wrench. Or, tighten that screw with locktite, then slide the engine into place and tighten the other three.

RE: Engine mounting question
 

Here is the way I do it. Tighten the obstructed bolt to where it is just below the flange before installing the engine. once you tighten the open bolt it will be plenty tight.

RE: Engine mounting question
 

WHICH needle valve is causing the obstruction?

If it's the rear one, simple remove the whole assembly from the retaining brace, put the engine on and then put it back in place.

I doubt the front needle valve is to blame, but if it is use an offset screwdriver, or change out the mount.

RE: Engine mounting question
 

I have a wildstick-40 that I had problems with mounting the needle valve assembly using an OS 50 SF. The needle valve assembly was attached to the rear engine plate and everything was so tight that it was impossible to mount the engine correctly with the mount I was using (Sullivan flex mount). So, I mounted the needle valve assembly to the fuselage and simply ran the tube from the needle valve to the carb. It looks somewhat dumb, but it works. Done deal.

Meaning, there is always a way to do something with those remote needle valve assemblies.

CGr.

RE: Engine mounting question
 

Number three is your best choice. Get one of the Dave Brown mounts of the correct size for your engine. Drill and tap the mount to fit the engine. The Dave Brown mounts can usually be removed from the plane with engine mounted if needed. They have center lines cast on the radial part of the mount to make alignment a snap.

I just finished my second ARF, a Phoenix Fun Star (crashed my four star 60 and needed something other than the trainer to fly and didn't have a kit far enough along). It had the type mount you are talking about. The kit calls for either a two stroke 40 or four stroke 52. The mount may fit the two stroke, but was about an inch short for the four stroke. A little work popping out the blind nuts and putting a donut with new blind nuts to fit the Dave Brown and I was in business. There are other mounts that would work, but the DB's are inexpensive and easy to drill and tap.

Don

RE: Engine mounting question
 

Amen brother!

Chondar take that cheezy mount find the nearest lake and throw it just as hard as you can. With those type mounts you will always be fighting a loose engine. Seems we finally got the word out to manufactures of kits many years ago and that type mount just about became extinct.

Seems as though now some of the misguided ARF manufacturers are now trying to pawn them off agine as their latest and greatest thing to the newbys.

Only just my opinion

John

http://www3.towerhobbies.com/cgi-bin...?&I=LXB874&P=7

RE: Engine mounting question
 

Another possible solution: Put the screws in the mount going UP from the bottom. Then you just need to squeak a wrench in there, and screwdriver from the bottom. In this case, any threads in the mount itself should be drilled out, and double nuts used on top. I usually mark the nuts with a sharpie, creating a "witness mark" which allows a quick visual check to see they haven't moved. None have to date.

J

RE: Engine mounting question
 

I just dealt with this exact issue. You can take out one of the screws holding the needle valve to the mount (the one that is right over the hole you can't access) and turn the needle valve 90 degrees out of the way. This will give you just enough room to get a small screwdriver down to the screw hole to tighten that screw. The reinstall the needle valve.

RE: Engine mounting question
 

All excellent suggestions, thanks! It seemed like the suggestion of mounting the engine first THEN attaching the needle would work with the least fuss, so I tried that first. I spent a while wrestling with it (it's still quite a tight fit in a very limited space in there) before one of the nuts fell out of the bottom of the mount. Rather than stomp the poor thing I'm going to go to bed now and drop by the LHS in search of a Dave Brown mount tomorrow after work.

Looking over at my Avistar, it has the same mount. The OS .40 LA fit much easier there than the .46 AX does here!


J

RE: Engine mounting question
 

Just a follow up, since I hate it when threads end without resolution!

I picked up a .46-.50 Dave Brown mount from my LHS but it proved to be too short: the engine rails weren't long enough to hold the engine far enough forward for the prop to clear the LE of the cowl cheeks. Short of hacking up the front of the Kaos or adding a spacer between the firewall and the back of the mount I instead gave the original metal mount another try and managed to make it work after all. Amazing what a little patience will do sometimes. :D It's a very tight fit, but all seems well.

There's a [link=http://rocketcityrc.com/events/2008-BigBird/2008-BigBird.html]big bird fly-in[/link] at my club field Friday and Saturday, but with a little luck she'll maiden on Sunday. She looks great now, just something about the Kaos says 'airplane' to me, and already I'm thinking I'd like to try building a 60-size Kaos variant someday...

Thanks again!


J