Can a Tee See 049 spin a 1.5" spinner

It will do it. Far from ideal though. How much does the spinner weigh?

I am horrible with math, but seems to me the weight would have more effect the further out it goes from the crank centerline.

Sure it will spin it. But how fast? Who knows? Might be adequate depending on your mission. If you're a speed demon, forget it. Try it out and let us know.

Might be a dumb question (still an honest one) but why would a spinner reduce the rpm?

If we assume it is balanced well enough, and not remarkably heavy, all I can think of is a minor flywheel effect that it may cause. Also some drag while flying obviously but a spinner is more aerodynamic than a bare engine without a spinner. A large spinner obviously covers part of the propeller blades but that should increase the rpm somewhat, right

Any input from the experts would be most welcome  

KariFS wrote:Might be a dumb question (still an honest one) but why would a spinner reduce the rpm?

If we assume it is balanced well enough, and not remarkably heavy, all I can think of is a minor flywheel effect that it may cause. Also some drag while flying obviously but a spinner is more aerodynamic than a bare engine without a spinner. A large spinner obviously covers part of the propeller blades but that should increase the rpm somewhat, right

Any input from the experts would be most welcome  

Yes, my thoughts as well!  

I guess I should have been more specific. The larger spinner will blank out some of the prop, therefore possibly reducing some thrust with a resultant lower forward speed. As I mentioned, if speed isn’t a factor, it might work out just fine.

Thanks Tee Bee and ’Nut for your answers! I was thinking ”power = rpm”, but it is not that straightforward obviously. Thrust is what makes airplanes go, not rpm

Perhaps the reason for misunderstanding engine loading is the load variance while running is difficult to visualize? An IC engine actually has a power stroke and an exhaust stroke where the power (combustion) stroke accelerates the piston but the exhaust (pumping) stroke slows it down. A spinner or flywheel will load the engine (no matter how little) and cause a small loss of power.

I think we tend to forget this because they sound more like a turbine than a tiny IC engine.

I never entered a model contest where speed or aerobatics was a goal but did use a few spinners on really hard to start engines so a starter could be used. Found out early on that plastic spinners were not up to the task.

Bill

A spinner will have minimal impact on thrust. The center of the prop is particularly draggy, so a spinner will likely improve speed, but this really depends on the rest of the airframe. The outer 1/3 of the prop blade does 90% of the work.

The biggest issue with a large spinner on a small engine is getting it installed so it runs true and has the balance needed to run as fast as they do.

20 years ago I was flying electric racers with 4.75"-5" props in a 1.5" spinner at ~30+kRPM on a motor with a 1/8" shaft and it went over 150MPH.

Thanks for the input gentlemen. I think I will revamp the plane around the yellow Cox spinner. The plane will be smaller and lighter.

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Just so you know, the outside 10% of the prop puts out the majority of the thrust. That's why planes with big radial cowls don't suffer much, and also why larger spinners don't take away any significant amount of thrust.