Discussion in 'Electric Propulsion' started by Armilite, Jun 30, 2019.
Electric Motor with Prop on Test Stand at about 4000rpm.
The electric Waiex was quieter in flight than I thought that it would be.
A slower turning prop would make it even quieter, as would a more streamlined airframe.
Have ya ever heard an R/C Zagi at full revs?
Super annoying loud when set up for high-speed. Small props and high revs equal big noise. I really like the turbo-prop sounding systems offered by electric power....but that's just me.
I measured a Zagi type with my sound meter at the club field. It was louder than a modern OS 40 glow two-stroke engine which do have quiet mufflers.
One must always consider noise. It is produced by the fuel/electricity one purchases, and does not manifest itself as thrust.
Hince, if the system is loud, you should try to isolate where it is coming from.
Keep in mind that the electric motor by itself would be a whole lot quieter than an IC engine. Remember IC engines have from 1 to 8 (or more!) explosions per revolution.
A lot of the noise (in the OP video) would be from the air from the prop hitting the support frame, From what I see there would be 8 "opportunities"---2 prop blades x 4 support frame members. This can also be a source of vibration in the airframe. I remember reading somewhere about how to reduce this, at least for a pusher prop.
Then more noise from the prop itself disturbing the air.
All of these can happen regardless of the type of motive source used.
As pwood66889 said, any noise you hear is an indication of lost energy not going into thrust. So it would be worthwhile to eliminate or reduce it as much as possible.
If you park that OS 40 on a wing and spin the prop right on the trailing edge, it's going to make a whole lot more noise too.
The zagi types are loud because they notch the trailing edge of the wing and spin the prop very close to it. LongEZ's make the same noise. The difference is the frequency because the model prop is turning so much higher rpm.
If you want a really loud electric, just spin the rpm up till the tips go near sonic. Even a 5 nch prop can generate quite a bit of volume. I have changed out drives on my pylon racers from 5 inch props that spin over 40,000 rpm to very high pitch 9 inch props that only spin 10-12,000. You barely hear it now and it still goes 190mph.
Yep, that shows the problem is the prop not the engine. The super quiet YO--3 of course had an engine, but the prop required the most design change.
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