Welcome to PhantomPilots.com

Sign up for a weekly email of the latest drone news & information

Tri blade propellers

Discussion in 'General Discussion' started by boat chaser, Aug 8, 2013.

  1. boat chaser

    Joined:
    Jul 2, 2013
    Messages:
    223
    Likes Received:
    0
    Location:
    Fremantle, Western Australia
    Martcerv posted about these a while ago and I decided to try a set. I had to ream them out to 8mm to fit the motors and some serious balancing was needed but the result was a faster and much more responsive machine. I don't know how much faster I was going in attitude mode but it was definitely faster with more lift when needed. I would have made a quick video but I headed out in between rain so didn't chance the gimbal or camera on the first run. I will post some video soon of two identical runs, one with triblades and one without. So you can see the difference in speed. Check them out.
     

    Attached Files:

  2. Sac D

    Joined:
    Mar 3, 2013
    Messages:
    419
    Likes Received:
    1
    Location:
    Northern California
    I've been using 9045 tri-blades on my F450 for a while and really like them.
     
  3. Scalpel78

    Joined:
    Jun 18, 2013
    Messages:
    36
    Likes Received:
    1
    Where did you get the tri blades for the Phantom?
     
    corvetteman likes this.
  4. bumper

    Joined:
    Aug 6, 2013
    Messages:
    94
    Likes Received:
    0
    Not speaking specifically about quad propellers, but propellers in general though most of the "rules" I think would still apply.

    It's been said propeller design is both science and black art. However, there are fundamental truths that are hard to get around. One of these is that the fewer the blades the more efficient the prop will be. This is due to interference drag - the following blade, if its placement is closer to the preceding blade, then it will also be closer to the disturbed air left by the preceding blade and this causes "interference drag". Single blade props are more efficient than two blade and two blades are more efficient than three.

    So how come those WWII fighter planes had multi-blade props, some with 5 blades and even contra-rotating two props? They had to harness the increasing horsepower in a given prop arc. So max prop efficiency was not the major design goal.

    All else being equal, and is seldom is, 3 blade props will run smoother than two. They also tend to have more static thrust and to climb slightly faster than two . . . but, they aren't faster. On a Mooney, a 3 blade will be 4 or 5 knots slower.

    As blade length increases so does efficiency. But, few dispute that multi blade props look cool - - on airplanes it's called ramp appeal.

    I'll be keeping two blades on my Phantom for now, flight time is more important to me than speed, and I suspect flight time will suffer with 3-blade props.

    bumper
     
  5. Driffill

    Joined:
    Jun 14, 2013
    Messages:
    529
    Likes Received:
    3
    You may want to investigate further, tri blade props do give longer flight times, I wish I have mine by next Saturday!

    A single prop is unfeasible as you could never balance it! Two blade props are easy to balance and store etc, three blade props will have more lift, therefore a lower rpm is needed, and less power is used!

    Three blade props are the most efficient set up for wind generators (as I rambled about in another thread)

    As for the trailing drag from the extra blades??? Have you ever noticed your fuel economy drop if you draft a bus or truck! I assume the same thing would apply to the drag on and before any two blades on a given prop.
     
    Khrattos likes this.
  6. bumper

    Joined:
    Aug 6, 2013
    Messages:
    94
    Likes Received:
    0
    Drifill,

    I can tell you are not an aerodynamic engineer (but then, neither am I :) ). However, I'm an aircraft owner and pilot who has lots of experience working on planes, balancing props, and flying behind them.

    As far as using drafting behind vehicles to prove a point, it's not the same principle at all. I suggest doing some searches on line and look for things like <interference drag>, <propeller efficiency> etc.

    Single blade propellers ARE in use - - see Alisport Silent for one example - - but I agree with you, not so practical unless there is a design reason for them, as is the case with the Silent. Still, it's an irrefutable fact that for the same design airfoil, two blades will be more efficient than three. In real airplanes, the point of cross-over when a 3-blade even starts to make sense, is around 300 hp. With upwards of that much power, the other advantages of 3-blade props start to make sense as there's enough engine power to overcome the decrease in prop efficiency (that, for testing by Aviation Consumer).

    All of the above should be taken w/ the usual salt dose - - when scaling to model sizes, Reynolds numbers don't necessarily transfer directly from full size.

    bumper
     
  7. TickTock

    Joined:
    Mar 31, 2013
    Messages:
    171
    Likes Received:
    1
    bumper, I agree with all your points. It is my understanding that the only reason you see tri-blades on aircraft is extenuating circumstance (like ground clearance). HOWEVER, my test comparing the GWS 9050 tri-blades did result in a noticeably increased hover time. I used the same battery and was able to monitor the pack volts via fpv. From full charge to constant red flash I gained over a minute with the only change being the props.

    carbon fiber:
    start pack volts 12.16V
    constant red flash @ 10.65V, 7:45 minutes

    triblades:
    start pack volts 12.16V
    constant red flash @ 10.64V, 8:53 minutes
     
  8. boat chaser

    Joined:
    Jul 2, 2013
    Messages:
    223
    Likes Received:
    0
    Location:
    Fremantle, Western Australia

    multicopter sells them online. Bit harder to balance but once you have done one the rest get easier.
     
  9. martcerv

    Joined:
    May 27, 2013
    Messages:
    1,002
    Likes Received:
    2
    From my testing with these they give a pretty significant boost to a phantom. I am no engineer but do like to do lots of practical testing and always try things many others say not to just to see what happens in the real world. ;)

    In the Phantom I think the main reason for the better performance and efficiency is that the stock 2 bladed 8045 props are very much under propped for the weight of the phantom using these motors especially if you add more gear to it and fly around 1.2KG total. With regular props it is struggling to lift this and so needs much higher RPM purely to get the thing off the ground and hover, sure the larger triblades will use more power at the same RPM but with the much greater lift flying in the same way as you would with the regular props will give you more efficient flight and longer overall flight times.

    In GPS mode and ATTI mode there is altitude hold going on so for slow flying in these modes the props will be spinning pretty slowly and so use much less power to achieve the same flight behavior as regular props. What you can also do is due to the greater amount of lift its also possible to get more performance out of it and in a multi more lift also can give more speed. The way you move forward or any direction is by pitching the quad in any given direction, the higher the pitch angle the higher the speed but if your props dont give you enough lift then at high angles you will also lose altitude, so higher lift lets you maintain higher pitch angles without losing altitude so it can go much faster with greater lift. This is mostly noticed flying manual mode but you also can get much more speep flying in ATTI though you are always fighting the max pitch angle limits within the controller and it does the throttle control to maintain level flight at 50% throttle.

    Using manual mode you can get it into some crazy pitch angles and with the right throttle percentage you can get it going very quick. The funny thing is when doing this as soon as you level the craft but dont reduce throttle quick enough it will shoot to the sky in a big hurry as there is no altitude hold going on. Also in manual mode you can do a very simple test for lift by seeing how much throttle you need to maintain a hover. My first test flight after using triblades going to carbon reinforced 8045 dual blades I nearly crashed when switching to manual mode as I needed so much more throttle to hover after the switch. I didnt expect this and used it at a level I was with the triblades and it came down very quickly :D

    Here is a video doing some manual mode flying in calmer conditions using these props and some tiger motor's mt2216on my phantom weighing 1170g. Flying like this gets me flight times closer to what I get with stock props in GPS or ATTI mode but clearl much more performance due to the extra lift here. Flying regular slow style I get about 1 1/2 minutes longer in this setup compared to regular props.

    [youtube]http://www.youtube.com/watch?v=7jTnb-szvYE[/youtube]

    A basic way of explaining the reasons for more performance even though the motors are pushing more props can be seen here. Where driving a Prius vs M3 when you push the prius to its limits and drive the much more powerful M3 to just keep up the prius will use more fuel. Sure you wouldnt drive a prius like this all the time and using a smooth driving style in both would make the prius more fuel efficient but flying a heavy phantom with stock props is pretty much flying it at its maximum. With larger props unless also pushing very hard you will get more efficiency out of the greater lift props that don't need to work as hard to achieve the same performance. Go to 3:30 in the video below but if you watch the full video it pretty much explains my theory on the phantom and larger props quite well using supercars and fuel mileage.

    [youtube]http://www.youtube.com/watch?v=JmxUsGiGp3w[/youtube]
     
  10. jumanoc

    Joined:
    Jan 21, 2013
    Messages:
    700
    Likes Received:
    8
    I bought these.... still on the way... no tested yet.

    [​IMG]
     
  11. bumper

    Joined:
    Aug 6, 2013
    Messages:
    94
    Likes Received:
    0
    Sometimes it's necessary to eat crow (even though it doesn't taste all that good unless battered and deep fried :c)

    Okay, I've ordered the GWS 9050 on eBay to test. Considering the testing other's have done, bigger prop "rules" may not apply.

    BTW, after spending $10,500 for just one 2-blade MT prop for my Husky :shock: , these tri-blade props seem quite a good deal.

    bumper
     
  12. martcerv

    Joined:
    May 27, 2013
    Messages:
    1,002
    Likes Received:
    2
    I will get a couple sets of these also to try, I have tried 8040x3 GWS props but they weren't much good I think mostly because they are just too soft for lifting something as heavy as my phantom. They just dont give me too much confidence in the air so I have only done a few short flights with them.

    Its possible that a larger 2 bladed prop may be more efficient then a smaller 3 bladed prop if they both have similar lift. The thing with a phantom is the small frame size does limit prop size and 9 inches is pretty much the max you can go and so I triblade will give the most lift possible in that size using this frame. From what I have read elsewhere a 9050 triblade will have similar lift to a 1040 dual blade, on a larger frame it may be better with the larger dual but on smaller frames the tri blades will be better if your running out of lift with a dual blade prop. I have tried about 6 different props so far and these 9050x3 are easily my favourite, they need a bit of balancing and id love something a little stiffer but the extra lift makes these my number one choice atm.

    I have also tried some graupner clone carbon 8x5 props, they are nice props very strong stiff and light but the profile at 8 inches is no good on the phantom. Much less lift then the stock 8045 props as the graupner style has a much narrower blade tip so less surface area. These give me the worst lift of all my props and make the phantom a pig to fly.

    At the price of these they are well worth a try and have given my phantom a nice boost all round so I am happy.
     
  13. Scalpel78

    Joined:
    Jun 18, 2013
    Messages:
    36
    Likes Received:
    1
    I just bought these from ebay:
    [​IMG]

    They should fit, right?
     
  14. martcerv

    Joined:
    May 27, 2013
    Messages:
    1,002
    Likes Received:
    2
    Those look the same as mine just the hole looks a little different, by the look of it its larger and coming with 8mm inserts would say this. The ones I have would need you to drill or ream out the center of the hole as it is smaller then 8mm there and I used two 5mm inserts to fit my shafts but with that and the 8mm you should be able to use it on the phantom without needing to alter the hole.

    Here is a pic of all the props I have tried on my Phantom

    [​IMG]

    Left to right
    GWS 9050x3, DJI Phantom white stock, Carbon 8045, Black DJI Phantom Stock, ARK 8x5 Graupner clone Carbon, GF 8045 Carbon reinforced, GWS 8040x3

    Of all these the 9050x3 are easily the best ones for me, needs balancing but easy enough to do, the worst are the ARK 8x5 simply not enough lift out of the thinner blade but they are the best made and most solid props I have which is a real shame. THE GF 8045 carbon are way out in the hub and a PITA to balance which I still haven't managed to get spot on.

    The 9050x3 do break and bend easily in a crash so best to get a few as you dont want to risk flying a damaged prop but they do ok cutting through some grass and branches unlike the 8045 carbons which break on impact with most things.

    The 8x5 carbons are so stiff and solid they would likely break your motor before they break so not sure if that is a good thing but I would like some carbon props made that well in a better profile for a phantom. Maybe in 9 inch triblades :)

    I have seen some other triblades others are using on their quads but only available in the US. 9x7x3 by Master airscrew about $7 per prop and not sure about the pitch angle on these but I will order a set to try out on my phantom.

    http://masterairscrew.com/3-bladeseries.aspx

    [​IMG]
     
  15. bumper

    Joined:
    Aug 6, 2013
    Messages:
    94
    Likes Received:
    0
    Good info Martcerv - - thanks.

    I see you have a short length of 1/8" ID tubing (probably silicone) on the balance shaft of your Du-Bro balancer.

    My guess is this goes into the cone side of the reversed cone to add pressure and friction to the prop hub to keep it snug on the centering cone.

    The problem is that with the reversed cone it's difficult to keep everything compressed while tightening the collet and end up with a prop that is pinched tightly

    I made something similar on my metal lathe out of black Delrin plastic, Shaped like a top hat, there's a 1/8" hole for the balance shaft. The "brim" is 1/2" diameter with flat face to register against the opposite side of the prop hub and press the prop against the fixed centering cone. The narrow part of the "top hat" goes into the "female" cone and compresses against a 1/8" ID O-ring (the elasticity of which provides the tension). Very easy to use when mounting and remounting several props - - and doesn't lose it's tension while sanding a blade to balance without first taking it off the shaft.

    bumper
     
  16. Skylane765

    Joined:
    Aug 25, 2013
    Messages:
    103
    Likes Received:
    0
    Yes, the les blades you have the better power you get. I have a 3 blade prop on my new 182Cessna and like it for looks. But a two blade is more efficient. We use a 3 blade to get more ground clearance and better balance.
     
  17. Skylane765

    Joined:
    Aug 25, 2013
    Messages:
    103
    Likes Received:
    0
    That is fixed pitch on the Husky? Try $35,000 for the 182T
     
  18. Skylane765

    Joined:
    Aug 25, 2013
    Messages:
    103
    Likes Received:
    0
    All very true, on my plane I also have 3 blade and it is a simatar type prop that now are used on new props for AC.
     
  19. martcerv

    Joined:
    May 27, 2013
    Messages:
    1,002
    Likes Received:
    2
    I do agree with you here but in some applications there are physical limitations meaning you need to use a smaller prop then you may want. The more prop surface area then the more lift it will be able to generate and multirotors arent like planes they have the prop providing lift mostly as you would never fly it directly into the oncoming wind as on an airplane. So the principles will be a little different but obviously if you look at big heli's they use a huge 2 bladed prop.

    The phantom shell limits the maximum blade length you can use at 9 inches and the suggested weight of 1kg to a max of 1.2kg is mostly due to the prop size. The exact same motors can lift much heavier weights on a f450 as it can take larger props and the stock 8 inch phantom 8045 struggles much over 1kg with flight time drastically cut with every gram above that. The stock props dont have enough lift and this forces the motors to run close to max rpm where they use the most power using 9 inch dual blades will help but using 9050x3 is equivalent to flying 1040x2 which you cant physically fit on a phantom. The larger dual blades are likely more efficient but as they arent enough prop for anything but a stock phantom with no extra weight. Using the 9050x3 gives you the most possible lift in a phantom and this also gives longer flight time if flying the same speed as you would on regular props. You also get the benefits of better flying capability due to this lift and this can either give you more flight time or faster flying if using the motors as hard as you would need to with the smaller props.

    When I first thiught of looking into trying 3 bladed props I searched online and all the experts were saying the same as you. 3 blades will be worse but the funny thing is none of then had ever actually tried them and I have found with many things not to take experts opinions too literally when they havent actually tried something in the exact circumstances they are commenting about. I found a big difference in various 2 bladed prop designs at both 8 and 9 inches giving big differences in flight times. Generally the smaller the blades surface area the worse they were I terms of lift, the less lift the less flight time I got so thats what made me try the triblades. This gives me the largest surface area possible on the frame and 9050x3 is 33% more prop then 9050x2 as there are 12 blades instead of 8 at the max length you can fly on the frame. I thought it cant hurt to try and amazingly the extra props translate very well to similarly the same extra lift.

    Also when looking at a large propped quadcopter there is already so much turbulance with 4 high spinning blades spinning so close to each other that its all going to be pretty different comparing forward flight with a single prop plane flying directly into the wind and a 4 propped multirotors using the 4 props mostly 90 degrees to its flight direction.

    The funniest thing I have found so far is all the experts were saying graupners are the best props yet in my testing they are easily the worst prop design I have ever put on my phantom in terms of lift, flight time and manouvarbility. They may be much better on much higher rpm quads using 9 or 10 inch graupners but a phantom at 8 inches they are complete rubbish and 9 inches they dont even match the dji 8045 props.

    I am far from an expert at anything but I tend to look at all problems from every side not just what has already been done by others. Sure if someone is doing something getting better results then what I am I will give that a go too. But if I want to get more out of something there is little point I trying the same things expecting different results. I have had lots of fails but have also found many surprising results in some things that I wasn't so sure about and gett8ng much better results then I thought were possible and getting the performance out of the phantom when at 1275g with 2 gopros and fpv setup that wont even lift off with regular props is pretty clear proof to me that 3 blades are the go on the phantom. I think if DJI tried some out they would find they could make a much better 3 bladed 9 inch stock prop to give a good boost to the phantom over the props they come with atm.
     
  20. martcerv

    Joined:
    May 27, 2013
    Messages:
    1,002
    Likes Received:
    2
    To add to my essay, I think the gws 9050x3 props are far from a perfect prop, these could be made much stronger and stiffer but even as they are soft and floppy they are easily better then all the other props I have tried so far. If someone were to make a better version of such a prop even work on the profile to best suit a multi then they wouod surely be on a winner. Look how many people are making specific props for small multicopters and phantoms but they are all pretty much the same. Only difference is build quality mostly between the and its quite hard to find quality props these days with so much crap around. If someone made good quality well balanced or easy to balance props then id pay much more then the current going price for all the cheap junk that so many companies are producing. This the reason the graupners are considered so highly as they are well built props but just not for a phantom unfortunatly. The graupners I had and also the quality carbon clones I have are the best built props I have bought but as they dont fly well I got rid of the graupners and the carbon clones are gathering dust. Whilst flying some cheap soft flexible triblades though fairly well built props compared to some others I tried simply because they outperform the rest.