How Close To the Engine Is Too Close??
 

Hi,

I'm working on an open-install project where some of the servos are in close proximity to the hot area of the engine. The servos are about 3" off to the side of the bellmouth of the pipe. When the engine is running, I can put my hand between the engine and the bellmouth (closer to the servo, of course...) and it's WARM, but not uncomfortable.

How close have you guys seen in installations where the plane didn't crash because the servo melted?

RE: How Close To the Engine Is Too Close??
 

Enough room to get your fingers in there enough room for a heat shield should be fine. Will be even cooler while flying with all the air blowing through.

RE: How Close To the Engine Is Too Close??
 

Here's the rule of thumb.

Anything over 120 degrees, you can touch, but you will have to take your hand away.

Anything under 120 degrees, you can keep your hand on (of course till you get too cold).

The servos are rated at least to 150 degrees cause I have temp probed them at that temperature before.

Now, for the "touch" test of a fuse.

Fiberglass starts getting soft at around 155 degrees. So there is some temperatures in between what you can't keep your hand on, but is perfectly safe for your airplane.

Best to have an IR temp sensor available on new install first runs in case your install puts you in the range between 120 and 155.

I have seen prolonged exposure at 145 that did nothing bad to the airframe, but you could not keep your hand on the fuse.

RE: How Close To the Engine Is Too Close??
 

Sean,

Damn fine information. Thanks.