Trike Modifications and Improvements
Efficiency: Perfect pitch UAVs and airboats lead to new propellers (at least some good from UAVs / Drones)
Finally found that article I was looking for on the trickle down effect of drone research-- better props for us. they mention and picture Sensenich by name ...
Unmanned aircraft and airboats would seem to have little to offer general aviation, but growth in the two industries is spurring advancements in propeller design and other technologies—with positive implications for aircraft owners and pilots. Sensenich Propeller has long produced wood, carbon fiber, and metal propellers for UAVs, airboats, and GA. And lately, substantial investments in specialized tooling and tough, lightweight materials for UAVs and airboats have led to a variety of new aircraft propellers—and lower prices.
“We’re producing large numbers of carbon ... for the full story, click HERE
HERE was Ken's earlier story indicating that maybe propeller technology had plateaued-- well, maybe some leaps in technology have occurred. All I know is that when Henry put on his Sensenich two-bladed prop (before he switched to 100HP even), he noticeably outperformed me (in Idaho mountains in summer)-- before that, I usually was a bit faster.
Comments
I've read that the fewer blades the more efficient the prop, even that one blade would be the best if it didn't need such a heavy counter weight. When I think about this I wonder why they still make three and four blade props, and here are these guys making the up to six blades..... There must be more to it than simply " less blades is more efficient". I guess that's why they make props and I milk cows ;-)
I'm in aircraft design and testing for the Navy and I can assure you, more blades (along with numerous other factors), the more efficient. The latest C-130J and E-2D are examples. Now that is weighing thrust and speed as a factor. Notice you won't find any 6 bladed solar powered aircraft. So then it's a curve modeling where a given number of blades creates x max thrust against y fuel efficiency. That's where high bypass ducted fan jet engines come in. Lots of prop blades! The jet compressors are rather small in comparison.
Hey Wile E., cool to have an expert here. Tell us more. So I had also heard the rumor that 2 blade props give more thrust than 3, but that multi-blade props are quieter. When you mentioned Navy, I thought of the huge multi-bladed props on subs-- but there one goal is also stealth. Noise and cavitation are just sources of power loss.
When people talk about efficiency, it's often extracting the most useful energy from the source with little lost. However in some applications of converting raw power to thrust, like a dragster, it's not necessarily efficient at all (lots of waste), but ultimately more thrust is acquired. (Which just happens to remind me of a cool example of acceleration in action I posted here a long time ago)
So, help us out understanding all this converting of horsepower to thrust stuff.
from my understanding its the length of the prop that creates more thrust from horsepower.the longer the blade the more thrust . but in a trike you are limited by prop arch room so as i understand it you increase the thrust by multibladed prop within a limited prop arch increasing the thrust just not as effieciently.the c-130 swings 4 very wide short blades per engine,no room to swing hugh single long prop. i agree please do help us understand . givin the same types of engines the largest diameter prop arch circle would produce the most thrust givin the same rpms.in adding more blades you are adding more weight and more parisitic drag .more parts of prop that are simple not doing much.on my soaring trike my 22 hp with single blade wooden prop produces almost as much thrust as the kawasaki 340 at i think 29 hp could be wrong on hp but in there somewhere, with a three bladed ivro prop. but if that kawasaki 340 had room to swing a longer single bladed wood prop it would kick ass relevent to the hp. think about it if you were canoeing in a boat which would you want a light long paddle or a light short small paddle. not saying iam totally corect just saying this is my understanding on it as far as trikes and trike engine go. so moving into the curve of ducted fans turbo props and turbo jets thats a whole different ball game i believe.wile scott iam not disagreeing with you just stating that is my understanding so feel free to corect or critic my understanding as it is limited.personally i would love to see a fuel efficient ducted fan for a trike. wile how about a second job?
when you enter the realm of turbo fan jet engines you are using the prop to send super speeded air into fuel mixer and burner into a ventury creating enourmous thrust. changing that to the more bird like flight the wing acts like a super efiecient propeller with very little drag. the short winged sparrow has a very fast flap rate and uses enormous amounts of energy and cannot maintain it for long.but a albatrous with his long wings in sink may flap for short durations and is exstreamly effiecient. i believe these coefficiants apply also to trikes propellers engines.as that curve moves up to the supersonic we leave the trike realm way behind.
Interesting discussion. To be useful for the trike world we probably should limit prop discussion to engines of less than a certain amount of hp, perhaps 100-115 for LSA. But the parameters become even more restricted for the smaller hp engines used on UL. While it is true that for a given engine (say a Kaw340) the thrust is proportional to diameter of the arc inscribed by the prop, there are limits. If one could fit a long 2-bladed prop (say 70") on an UL with a 340 you would not necessarily get better thrust than say a 64" prop UNLESS you have essentially an unlimited number of reduction ratio options to play with. This is because efficiency is lost when prop tip speeds get too high and this is especially true for lower hp engines. I have seen some theoretical work stating optimum tip speed is around 0.82 Mach but I know from experimenting with my little 26hp Simonini Mini 2 plus that even that is too high for this engine. I experimented with multiple reduction ratios and props and found this engine lost substantial efficiency with tip speeds higher than 0.7 Mach. It could well be that higher hp engines maintain good efficiency up to about 0.82 Mach. In any case above example is kind of a moot point because adequate prop clearances are always of concern in design and I don't believe I have ever seen a true UL trike with a prop length greater than about 62" (maybe up to 64") and almost all are less than that.
Many variables play into what is best prop for a given engine. One can see some of these in prop calculators. Flying speed is a good one. Every thing else being equal, a multibladed (say 3 or more) prop set to a lower pitch will loose more efficiency at a higher flying speed than will a 2-bladed prop with a higher pitch because it still retains some ability to bite the air. But multibladed props might be better suited for climb performance or towing (like aerotowing HGer). But I think if you are more interested in cruise performance and say reducing engine rpms (and fuel consumption) for your typical trike trim speed I was always under impression that this could be accomplished better with a 2-bladed prop. BTW, all my comments and experience are with lower hp engines (40hp or less) commonly used on true UL. So it may well be that say a 912 has so much hp that it requires 3 or more blades to properly load the engine for typical prop lengths needed.
My main point is that with lower hp engines maximizing prop efficiency is very important because we can't afford to give up a large percentage of available hp and not get any thing out of it. We are often dealing with marginally sufficient thrust just to get airborne and usually lower climb rates. This is why I think it is often useful to experiment with different reduction ratios and props to optimize performance. In any case, I have really enjoyed doing such experimentation. Oh, and I can also confidently say that thanks to my experimentation on my ATF I was able to save my bacon in clearing some trees when I one day exercised some questionable ADM flying low and simultaneously got caught in a pocket of sink.
I do not want to misrepresent myself. I work all day, every day, with 1,000lbs brain (aero-space engineers) and I am a test designer. The engineers design for a given performance and I design the test to ensure it performs as expected in the "real world". Often those guys never even see the real aircraft! it's all a computer world for them. I am a super geek and I love to discuss all their charts, graphs and Greek mathematics. Ultimately they leave me in the dust and I can't argue their third level dynamics. lol
I do love it though and often have in-depth discussions about this topic with them. Right now I am working with a high bypass ducted fan. It's very much a shrouded propeller mounted to a tiny (powerful) jet engine. Most of the diameter is not a compressor design; it's a prop. My good friend is working with the E-2D. It is a turbo prop with 8 blades! The prop shape is designed to unload vortices through the arch plane.
The most interesting thing I have learned is that any given prop is designed to be most efficient at a given altitude, airspeed, and thrust combination. Once you depart from any of those fixed variables, it looses efficiency; sometimes greatly, sometimes not.
Trikes do have a limitation on arch diameter. Arch diameter and prop tip Mach must be managed to avoid noise and concurrently energy loss. Most of us do value quite props. Pitch and horsepower are related ratios. Even the design of the tip of the prop is directly related to the amount of lift a prop design can provide. The sharper the tip angle, the more efficient it is at higher airspeeds. The more square the tip, the more bite it has at slower airspeeds (added P factor too) and can provide higher FPM climb.
My vote for best blend of these factors in a trike is the Arplast, three bladed, skewed tip design. Very quite, fast enough, and pretty good efficiency. Even this design could be bettered depending on which variable you want to improve on. It's always a blend of variables to get what you want. I want quite, speed, and fuel efficiency. Your results may vary.
Thanks Wile E, so rereading the article about trickle down it seems the biggest effect of UAV prop production is price decrease / mass production efficiency. Reading Ken's article maybe props are as good as they can get? Do you think there are any leaps in technology to be made?
Glad you like the Arplast-- that's what I got ;) So the Sensenich is hollow- swinging less weight takes less energy right, so that energy can be converted to thrust instead.
With all the compromises of props and pitch for certain speeds, altitudes and climb or level, is the best way to get better efficiency to change the law regarding in-air adjustable props on LSA's ?
Hey Sorry ULT, I read these in backwards order (like I read magazines). I just read what you wrote now and I really appreciate all the insight (especially directly trike related) that you guys are giving. Unfortunately, I can't add a lot of personal knowledge to prop questions, but I am really enjoying absorbing what you guys are putting out there. Please keep it up.
After a discussion I had with Boeing's lead engine designer on our program, his prediction is that current prop technology (for us small engine folk) has peaked out on materials science and fluid dynamics design. The only area he sees for improvement would be skewed blade designs and that is complicated. If LSA did allow for adjustable pitch, we would have a new set of variables to include. His point on that though is we as Trike flyers do not typically go into the altitudes regimes where adjustable pitch gives us the greatest benefit; generally above 10K. Looks like my Arplast is about as good as it gets until we see new materials. Maybe carbon nano-tubes will buy us some speed in 10 years or so.
wile scott high bypass ducted fan wouldnt that be something in say a dragonfly i think that there is alot of applications out there engines prop ideas that have never been fully investigated.inovation is moved by sales and affordability.could you imagine if all that brainpower that you work with could concentrate on say designing a very efficient light wieght engine and prop for a light trike. i wonder what it would look and perform like being designed by some of the brightest minds availiable. its important to look at how the hang glider trike industry has progressed over the last 40 years. the arplast prop has had some pretty high tech engeneering .i was very supprized to learn that when i looked at the wieght difference in going from my zenoh g25 engine with a wood 54 24 pitch prop to a kawisaki 340 with a 3 bladed ivro prop that the gains in actual thrust were not that great minimal at best, so horsepower does not nessasaraly translate in to more thrust . i had a lot of dicussion with lee boone who sold his sky cycle to jebb with the kawasaki 340 , fine for jebbs hook in weight .lee boone has a great site for helping you calculate your thrust correctly (ill see if i can find it and post it up)but now it looks as though ill be achieving my better climb rate with the same wieght kaw 440.it gets confusing to me and iam trying hard not to make expensive mistakes good to have this discuccion right now as i proceed in my changeover. ultratrikepilot ill be posting and putting up my progress as i get going on your group site 103 2 to three weeks away when i get all the parts. good discuccion guys keep it goin.
I'm not a technician but in my opinion there are a lot of different factors which determine what prop to use. The most effective is 2 blade prop. But, why the pilots (manufacturers) are using multi blades props? As Bill wrote one blade prop will be the best but they aren't balanced. Then 2 blades are the best? Maybe yes, but we are restricted by their diameter. Bigger is better, because - very roughly - for every 10 cm bigger diameter = 10 kilos of additional static thrust. For example: I tested a new SkyGlider 12,8meter wing with Verner VM-133MK engine. It was a manufacturer demo trike, demo engine 84HP/5500RPM with WarpDrive 2 blades with ground setting prop diameter of 192cm. It was a special trike with high mounted engine. With Verner's test pilot in the back seat we had stabilized climb of 7,5m/s at 75km/h speed. Alone I had stabilized climb of 11,5m/s (!!!). My actual trike is ordinary trike- Low mounted engine (VM-133MK) because low center of gravity is better for flying and for moving on ground. So I must use a smaller prop - 170 cm. Two 170 cm prop blades don't have enough power, or I would have to change the gear reduction. Then I used a slower rotation (by reduction gear) with a 3 bladed prop. I had to use another setting and now my engine is operating at 80HP/5000RPM. My stabilized climb is around 4,5m/s with passenger and about 7m/s alone.
The next factor we must to know is RPMs. If prop RPM is 3000/min or more, the blade tips exceed the speed of sound. It's more noisy and its dangerous to the prop's structure. Because a lot of small aviator engines are 2 stroke (Rotax, Hirth) and they operate at high RPM, we must to use a gear reduction to decelerate the prop. High RPM blades making an air vortex behind and high speed blades entering into this vortex will rapidly lose efficiency. A bigger reduction gear can greatly reduce the prop's speed and we can then use multi blade props, because their blades won't enter the air vortex of the blade before.
Next factor is torque. Torque on 2 stroke engines depends on RPM. More RPM = more HP = more torque. Look at a power diagram of 2 stroke engines to see for yourself... 4 stroke engines have better torque, and the design and profile of the prop is different. For better torque, some people are using a motorcycle or car engine (BMW,Honda, Yamaha, Subaru, Suzuki, Nissan...), but they are heavier. These are factors you should know when deciding what type of prop to use.
I think, these factors can be much more, which I don't know... I'm a pilot only, not technician :)
Jozinko, White Eagle,
The engine is where I see we have room for great improvements. The Revo and Tanarg have very nice chassis designs (IMHO), there are a few great prop designs out there to choose from, we have some sweet wing choice now (Riva "S", Quest, Mako, etc),. Our engine choices are abysmal! Rotax has the market cornered and it's nice but OLD, OLD, school tech. They just gave us fuel injection,,, REALLY!? How long have the benefits of fuel injection been out there? I've had high hope for Wankel rotary engines for a long time. They just can't seem to crack the fuel efficiency problems. I still have hope though. Other rotary designs are on the horizon. Take a look at the RadMax by Regtech. Very cool design! Already demo-ed and doing well. The ICE engine is a dinosaur that won't die easily! Reliability, Torque and horse power need to be maintained while you reduce engine weight. It can be done! Thermal management can also be done without tons of complicated cooling loops (Yes Rotax I'm taking to you!). Ok, venting over...
wow scott ul jozinko the information just blows my mind . i was talking with mike theakie discussing my engine changeover on my soaring trike. he was explaining to me why a rotax 447 puts out to much thrust for me at 40 hp and why its not the same with a kawasaki 440 40 hp, it depends on the length of the compression stroke. rotax 447 has a longer cylinder and piston compression per rpm hensss more thrust. so it looks like a balancing act in reliability.i can use the kawasaki 440 and will translate into much better climb rate we calculated the 340 and there just wasnt enough gain in thrust to translate into a significant climb rate. but the 440 should do the job just cant use the rotax 447 id risk bending battons.iam not much of an engine guy ,i can do complexed michanics i just prefer to get mad and kick a dent into my car door.when looking at changing out a engine it seems prettty ambiguous on what to do , at some point you halve got to make a decision and hope you come up right.