Is it safe to do an engine break in on a prop with no spinner?</p>

If you are talking about the plastic spinner, then yes it is okay to run your motor. Make sure the prop washer and the prop nut are installed and are tight. Good Luck, Dave

Absolutely, Some people even fly without a spinner.

 it is an arf and  i can't seem to find the right screws for the spinner that came with it and i would like to break this os in right now.

Hmmmmm...I remember having a spinner on my Edge once...until it met Mr Tree.

Yes you can break in and fly without a spinner. Some planes even just looks stupid with one on

I fly most of mine without spinners., That way if I want to change props I don't have to take everything apart.

I like spinner nuts. They are fairly small and replace the propnut entirely and they don't break like the plastic spinners but they do resemble them in shape but not in size and work good with a starter

As a side note, I just looked at the parts list for the OS 75 AX, looking specifically for a prop nut. The one they list in the parts list shows for an OS 91 Surpass engine.

http://www3.towerhobbies.com/cgi-bin...I=OSMG0575&P=Z

Are they the same?

CGr.

Yes they are the same.

Thanks.

CGr

Only reason to have a spinner is they look cool and the starter fits them very well. The spinner nut is one of those forgotten items and well worth remembering. I have them in my box in several sizes and a couple of different shapes, cone and nut. As long as you can start the engine then a spinner isn't needed. I have some Bipes that would look down right stupid with a spinner on them. I do admit to having more planes that would look even dumber without a spinner though.

In your case it will work with or without, but if the engine is in a cowl such as a decathalon then a spinner should be used as it directs more air into the openings for proper cooling. Most modern full scale aircraft can not be run without the spinner for this reason. This is only a factor on true scale aircraft, but can be critical.

DuBro makes a variety of sizes and colors of very nice Spinner-prop nuts. All you need to know is your shaft size and thread.

http://www.dubro.com/hobby/ecatalog/dubro/00001.htm

http://www.dubro.com/hobby/ecatalog/dubro/00052.htm


Harry Higgly has a lot of neat things, and a chart for engine - shaft size - and thread.

http://www.harryhigley.com/index.htm

http://www.harryhigley.com/ShaftSizes.htm

http://www.harryhigley.com/EngineAccessories1.htm


Scale/semi-scale models deserve a good spinner such as Dave Brown Products or another popular brand much over-priced, IMO.

The use of a Prop Spinner-Nut is FIRST CHOICE for all others. Makes life much more simple.

Prop shaft / spinner nut size 5/16 x 24

One of my LHS started selling Magnum spinners a few years back, I strated using them and think they are as good or better then the bigger name brands. Cheaper and come with the addapter that often/sometimes even fit your engine. For cheap I still like the cone shaped spinner nuts. Like other Gene said, it's just easier to remove the nut when you need to do anything like change a prop. At the price they are one of the best deals in town.