I have just purchased 4 new Graupner 10x5 Propellers to replace the existing APC 10x4.5 slow fly props on my TBS Style Quad as I was not happy with the vibration levels.
Thought I would share the results.
Vibration levels for APC Props
Vibration levels for Graupner Props
I had spent a lot of time trying to balance the APC props but could never get much improvement. I just balanced Graupner props very quickly and got the above result
David Ardis
Comments
Yeah, it's a miracle these the APC SF props work as well as they do. And indication that APC is a high quality product that is overdesigned. I've been using them on a medium-lift octo with a fair amount of power. But I'm switching over to APC MR's.
Slow fly propellers where never meant for this. They are made for low rpm's on light weight planes, not high rpm lifting like we are doing.
Gary. You are are right but I was not expecting that much change between two sets of balanced props.
Thomas. Unfortunately I cant get APC Multi rotor props the postage is more than the props.
Shanthosh. I was measuring the vibration in flight using the APM 2.6 all test where done indoors all that changed was the props.
May do a few full power runs with each set of props and post the results tomorrow.
may i know what setup did you use to measure the vibration ??
Interesting. We should do more testing like this. I would believe that the SF props cause a lot of vibration. They are quite flexible. I've been doing some testing which involved strapping my quad to the bench and running it with props on, and it's really surprising how much you can see the prop disk wandering around, even at less than half throttle.
I've purchased some of the new APC MR props, and they are quite a bit stiffer, I bet they create less vibration.
However, that's not the full story. In fast forward flight, stiff propeller will probably cause MORE vibration. This is because of disymmetry of lift across the prop disk, due to the parallel component of the oblique flow across the disk. The advancing blade has a higher effective Angle of Attack than the retreating blade, which causes a torque. The torque comes and goes as the prop aligns with the incoming airflow. This results in a torsional vibration.
Helicopters have teetering or hinged rotor heads to alleviate this, because they allow the blades to "flap". However, rigid blades used on multirotors do not allow this, thus the vibration. The more flexible SF props may in fact result in less vibration in fast forward flight, because they can flex to allow a bit of flapping.
Hi David,
It does look like you have a small improvement, but since the 2 charts are shown at different vertical resolutions they are a bit misleading,
You need to show the second chart such that the numbers on the left exactly correspond to the number on the top chart.
Taking that into account it does not appear that the Graupners are very much better, although both charts look like you are in the range of + and - 1 or 1/10G which normally is a very acceptable vibration range.
Best Regards,
Gary
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