Should I do it or not.

New Thunder Tiger Pro 46 on my newly finished Sig Somethin' Extra.
Forecast high is 38 for several days and by next Friday maybe 49 for a high.
Is this too cold?

I may not fly this plane until spring, not only is it cold it has been windy.

Bill

Hello!
No problem at all...only see to that you run the engine up to speed so it gets warm ...never let it four-cycle at low rpm. That is if it is an ABC, AAC, or an ABN engine.
Here in Sweden we sometimes get real cold weather in the winter, 22 degree celsius is the coldest temperature that I have flown a R/C model airplane...Brr!!

Regards!
Jan K
Sweden

22 Deg C? Heck that's about 71 F... downright toasty!

Bill,
Personally I'd wait till spring when it's warmer.
Then again, if you have a heated garage or basement with a very good exhaust fan, you could do it there.
My reasoning is this:
The main reason for breaking-in an engine is to heat stress and run-in the internal parts. If it is cold outside for you just think of the windchill factor of the prop-wash blowing across the head.
Are the cylinder sleeve, piston, head, etc., going get hot enough to be properly heat stressed? Are you going to want to spend an hour or so outside doing it.
Having flown off of snow and general cold weather I can definitely attest to the difference between the ambient temp and prop-wash chill! A simple needle-valve adjustment will quickly freeze your fingers! (Numb fingers don't hurt as bad however when you get bitten by the prop! )

Then again, I could be wrong. I am not a gear-head or metallurgist but, it makes a bit of sense to me.

I think a friend of mine broke in a Pro 46 on skis. It took a lot longer and had little or no ill effects on the engine. He may have run it a bit in his basement first...?

You could always wrap the cylinder head with tin foil or something else that's appropriate.

Patrick

I've run new engines in the cold before without
any trouble or concern . It is true that it will take
longer to heat up and perhaps "break in"along
with adjusting for a good idle etc but it
shouldn't pose a problem or be detrimental .

By the way "wind chill" won't apply to the motor,
it will however apply to your fingers.

Regards
Roby

Ambient temperature DOES have an affect on the performance of an engine. Being that the engine in question has a prop on it it will run with a colder head temp. (It's heat will be dissipated more quickly not to mention the cooler intake air.)

It is FUN though flying off of snow!!

I'm sure jaka was talking about 22 degrees BELOW ZERO! It's a common phenomenon up here.

Well, I have not made up my mind.
Here is another question on the same line....
Would it be better not to break it in if I am not going to fly it this winter?

I really don't think the weather will cooperate, I am a fair weather flyer.

Bill

Here's something that suprised me. I tried to start a 0.20 engine while holding it in my hand once (only put a few drops in carb so I wasn't planning on running for any length of time). Flipped it over and after a quick blip on the throttle, the engine was VERY hot. I got curious and while my TT .46 pro was cold at the field I started it and immediately touched the head. Within one second it was hot. These things don't take long to 'warm up'. The main thing is to have the engine inside the house before you start it so that it's doesn't get down to below freezing temps. If the planes inside at a nice 72°f then you go outside and start it the ONLY difference is that the intake air is cooler (okay ambient is too so cooling will be better but that just makes for a safer breakin). Don't sweat it, but then again dont leave your engine in the freeze for 3 hours then fire it right up as the metal has different expansion/contraction coeffecients.

- Joe

I think since you're not planing on flying the plane till spring just wait till then and keep that motor virgin.....

Bill, if it were me, I would wait. Not because of concern about the thermal expansion rates being different in cold weather, but because you will have to worry about corrosion of the engine more once you introduce the alcohol and nitro of the fuel. If the engine is REALLY tight when turning over by hand, you could either heat it with a covering heat gun before starting it, or keep it inside until ready to fire it up.
F. P.

OK,

I am going to wait.
I will put some after run oil in it and put it in a zip lock baggie.

Thanks everyone.

Bill

If I remember correctly - Wind chill is a measure of perceived coldness and is calculated not measured. As mentioned your fingers will feel wind chill but I don't believe the thermometer will. Ambient temperature is different !

As I understand it, as the moisture in your skin evaporates the temp drops, cooling by evaporation. The harder the wind blows, the further the temp drop. Also the reason it doesn't work on metal, no sweat.

http://www.learner.org/exhibits/weather/act_windchill/

Guess this explains a little.

I ran my MDS .68 in a couple of days ago in 40 degree weather and it was no big deal, I let it warm up at just above idle for a few minutes and then set the throttle at 6,000 rpm, after 25 minutes it was running at 6,900 rpm just from limbering up, I then ran it up to 11,700 and a few for a couple of minutes, it held that rpm steady, so I backed it down to 7,000 rpm for 15 more minutes. I then pulled the back plate off and it had no visible moisture in it. I sprayed the rear bearing and rod with Corrosion X and put the Back plate on and will run it again soon.