I had my Evolution .46 on my nexstar and am wanting to fit my JBA .56 onto it. With the Evolution the muffler is just near -1/16 th off the fuselage but the JBA .56 actually rest directly on the fuselage, zero clearance. I notice that the motor mount is 1/4 off center to the right side. My question is -> Should I create a wedge to straighten out the firewall and remount the engine on center or should I make a spacer for the muffler to extend it out an 1/8 th or 3/32 nd to give me the desired clearance. I don't want to cook the skin off my bird.

This angle that you describe is supposed to be there. So, do not wedge the engine to 'straighten' it out. The plane requires a right-down thrust angle.

The best solution is either to make the extension you are talking about, provided you have the mechanical ability to machine out this extension, or go to a place like Macs and get a replacement muffler with extension for that engine.

CGr.

If you lack machining abilities, you may be able to carve a "trough" in the fuse side for the muffler. Just a tiny bit of clearance is enough. If you remove wood from the outside to provide clearance, you may be able to build up inside to take any loads, if you need to. Partially buried pipes are pretty common. Here's a more drastic one on my 'stang...

Definitely don't alter the engine thrust angles. You could make a muffler extension or possibly use a readily available one: http://www3.towerhobbies.com/cgi-bin...?&I=LXD638&P=7

Since this is your trainer and not some masterpiece that you've spent months building, I would just carve some material off the fuselage where the muffler hits. Be sure to fuel proof that area with some covering or epoxy. Sure it's a little crude but trainers tend to get bashed up anyhow.

A muffler extension may work too.

Muffler extension sounds like the way to go. I have some Alum stock so i will get to making one up. The reason I considered making a plate to alter the thrust angle was that I believe the angle is to agressive. I haft to use all the trim to make it fly straight. I have places washers behind the left 2 mounting bolts to bring it out half way. This works fine and gives me some more trim to play with when needed.

Thanks for the help!

I have a Phoenix Tucano 40 size that I want to use an OS 70 Surpass.
Cowel clearence can work but my question is about installing the engine
in the inverted position. Do or I should I have any concerns? I have seen many
planes use four strokes inverted but I want to cover my base so to speak.

Thanks,
Damian

It's not a big deal to mount the engine inverted.

The engine may be a tad "tighter" in it's tuning requirements, but that is about it.

Siphoning, if your tank height is off, may be a small issue.

I run almost all of my engines inverted.

Very nice -Thanks for the prompt response!!

Ok, got another one.
Using the FS70, is ok to use a mount where the beams are independantly mounted on the firewall or
would it be better to use a mount such as a Great Planes mount where the beams are mounted together.

I hope this makes sense.

I know exactly what you mean and it makes no difference at all.

Thanks Opjose & Missleman. Now I have to get to work, I have an engine to mount...

Does it matter if the muffler is rubbing against the side of the plane? Mine is.

I'll make a heck of a racket very least or you'll have that special exhuast sound system.

and it'll put your new Radio equipment through the stress and vibration test
And you'll know for sure if those servo are as kick butt as the manufacture say they are.lol

And the LHS guy will be your best friend becuase you're buy glow plugs all the time
from running lean becuase of Bubbles.

Then it'll melt whatever covering or plastic it touches...that's okay, it's call war scars.

argh. [:@]

How much clearance do I need? Will 1/32" to 1/16" cut it?

It was so much work to get the engine to even drop into the plane, but it required the muffler resting on the side of the plane. It would take a 3.5" cut out of the side of the plane.

Does anyone know of a muffler extension that is only 1/8" to 1/4" long, or where to get one? The ones they have on Tower's site are much longer than I need. I'm actually looking for a gasket, which would probably do the trick, but there is none for the OS46AX. There are gaskets for the GMS .47, but I don't know how different the shape is.

Don't worry.... by the time to get through you'll be able to take it apart and put it back together in your sleep.lol
It always take forever in the first time for everything.

You did use BLUE locite...didn't ya. (BLUE you can take apart again)
RED...you might have to take a drimel to it.lol

If you didn't use any loctite..
mmmm I found like....12 muffulers just beyound the flight line oneday. None matched mine.lmao
And I couldn't even find mine.

you need more, or at least mine did. I thought I could get away with 1/16"...(not).
The engine vibrates when you throttle up or down.

I say at least 1/4 or more to be on the safe side.

Make a gasket from a 12 pack cardborad or something simular.lol

Or just run down to your auto parts store or machine shop they should have gasket material.
Or you can pay the machine shop to mill you an extension.

Or try those DuBro extensions that u cut with a hack saw or drimel ...I guess.

You absolutely do want to move the muffler away from the fuselage or the fuselage away from the muffler. No matter how strong motor mounts are, there is nothing good that comes from the engine contacting anything at all.

The more clearance you have the better. There is also little or no benefit to keeping the gap to a minimum. That hunk of muffler is out there and being close to the fuselage isn't going to hide a bit of it. And being further out isn't going to affect anything either.

A gasket isn't going to do the trick. Our systems don't usually benefit from gaskets anyway. And usually do not need them.

Go with the OS extension that fits your OS. They're available, and that's 99% of the problem with our model engines. If you notice, OS's are everywhere in huge volume and not all of them have extensions available. And almost no other brands have extensions at all available. So finding extensions, same mfg or not, just doesn't happen.

BTW, if you're worried about a muffler sticking an extra 1/8" into the airflow, it'd be much easier to cut the fuselage back than it'll be to find a perfect length extension. But neither are worth it.

Yeah I had to get a dubro muffler extension, and will have to extend the mounting holes a little to fit the .46AX. Its 1 mm different than a bunch of other .46 layouts. Thanks for the input, I bought the extension (1/2") oniline last night.

Are you talking about the Cheaks of the fuse, or the fuse itself. If it's just the cheaks like on most trainers, they serve no structural function anyway. Just carve it down until your muffler clears. If it's the fuse itself, then yes--an extension is in order.

the cut would continue from the cheeks onto the fuse. i got the extension; tower said they missed a 'side note' saying that one is required, and hobbico verified it.