Read ECalc's essay on coaxial efficiency and how it can improve.
http://www.ecalc.ch/calcinclude/help/xcoptercalchelp.htm#hints
I have 3 Y6's. Not one of them react the same when choosing props. Variables such as frame size, axial distance between props, motors etc. make prop choice a crap shoot up front. I normally use cheap props to test, then throw down bones and choose the better props (T-Motor etc.). Sometimes the choice is right, others not.
My latest Y6, a Sky Hero 750 is a challenge because I don't only go by how the copter flies, but also look at the data which shows I believe that there is much room for improvement.
PWM spread is a common problem on Y6's and coaxials in general. Ideally the top and bottom like to spin close to the same rpm, but the bottom props a bit faster (read ECalc's explanation). Currently I am using Gemfan 14x5.5 on top and Tarot 15x5.5 on the bottom, the "test" props. Using the same size/pitch causes a pwm spread makes the bottom props work work (motors get hotter), and stability suffers somewhat. Again, every Y6 is different.
At ECalc's suggestion through posting at RCG, I swapped the props; 15x5.5 on top 14x5.5 bottom with predictable results, including yaw issues and overall poor flight performance. The data shows it.
This is with 14x5.5 top and 15x5.5 bottom currently the combination that works reasonably well, but the bottom motors are working harder than the top which causes heat issues, although my motors remain cool since junking the Sky Hero motor mounts in favor of Kylin- huge reduction in heat and vibration levels improved.
Also predictably, the current draw rose slightly with the small props on the bottom. Obviously in order to gain efficiency the bottom props (top picture) need more pitch. The problem is prop choice for CF is very limited and generally TM style range from 14x4.8-14x5.5 and 15x5-15x5.5. There's no way to get 1.5+ lower pitch on the bottom.
T-Motor makes BW props with more variety, but only with 13" and 14" props to get a more desirable pitch difference; 13x6.5 and 14x5 to be exact. With those I believe the mid-throttle will be higher than desired and because they can only be purchased in sets, if they don't work it's $220 down the toilet. Currently mid-throttle is ~45%.
Then there is Xoar props. They have props that meet every combination under the sun, and I can buy matched pairs or single props unlike CF. Their pricing is reasonable as well. Why you can't buy single CF props is irritating.
So the bottom line is, I am tempted to experiment with Xoar props, probably 15x5 for the top and 14x7 for the bottom, but I have no experience with them. I think increasing the axial distance between the props would help on this copter, which would be accomplished with the Xoar as they require the use of prop adapters giving an extra 10+mm or so. One down side is with a high pitch on the bottoms, if one of the top motors fail, it is possible, although not certain, the bottom prop could stall, and everyone knows what that means. Are there MR fliers here that use or have used Xoar PJN props for their MR and do they work well? How do they compare in efficiency and thrust (apples to apples) to the more popular CF/APC et al props?
Thanks for your time.
http://www.ecalc.ch/calcinclude/help/xcoptercalchelp.htm#hints
I have 3 Y6's. Not one of them react the same when choosing props. Variables such as frame size, axial distance between props, motors etc. make prop choice a crap shoot up front. I normally use cheap props to test, then throw down bones and choose the better props (T-Motor etc.). Sometimes the choice is right, others not.
My latest Y6, a Sky Hero 750 is a challenge because I don't only go by how the copter flies, but also look at the data which shows I believe that there is much room for improvement.
PWM spread is a common problem on Y6's and coaxials in general. Ideally the top and bottom like to spin close to the same rpm, but the bottom props a bit faster (read ECalc's explanation). Currently I am using Gemfan 14x5.5 on top and Tarot 15x5.5 on the bottom, the "test" props. Using the same size/pitch causes a pwm spread makes the bottom props work work (motors get hotter), and stability suffers somewhat. Again, every Y6 is different.
At ECalc's suggestion through posting at RCG, I swapped the props; 15x5.5 on top 14x5.5 bottom with predictable results, including yaw issues and overall poor flight performance. The data shows it.
This is with 14x5.5 top and 15x5.5 bottom currently the combination that works reasonably well, but the bottom motors are working harder than the top which causes heat issues, although my motors remain cool since junking the Sky Hero motor mounts in favor of Kylin- huge reduction in heat and vibration levels improved.
Also predictably, the current draw rose slightly with the small props on the bottom. Obviously in order to gain efficiency the bottom props (top picture) need more pitch. The problem is prop choice for CF is very limited and generally TM style range from 14x4.8-14x5.5 and 15x5-15x5.5. There's no way to get 1.5+ lower pitch on the bottom.
T-Motor makes BW props with more variety, but only with 13" and 14" props to get a more desirable pitch difference; 13x6.5 and 14x5 to be exact. With those I believe the mid-throttle will be higher than desired and because they can only be purchased in sets, if they don't work it's $220 down the toilet. Currently mid-throttle is ~45%.
Then there is Xoar props. They have props that meet every combination under the sun, and I can buy matched pairs or single props unlike CF. Their pricing is reasonable as well. Why you can't buy single CF props is irritating.
So the bottom line is, I am tempted to experiment with Xoar props, probably 15x5 for the top and 14x7 for the bottom, but I have no experience with them. I think increasing the axial distance between the props would help on this copter, which would be accomplished with the Xoar as they require the use of prop adapters giving an extra 10+mm or so. One down side is with a high pitch on the bottoms, if one of the top motors fail, it is possible, although not certain, the bottom prop could stall, and everyone knows what that means. Are there MR fliers here that use or have used Xoar PJN props for their MR and do they work well? How do they compare in efficiency and thrust (apples to apples) to the more popular CF/APC et al props?
Thanks for your time.
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