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#11
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Morgans wrote:
This has been done with a extremely swept back shape, called "scimitar", that as it unloads at high speed, the tips twist back to higher angles of attack. I am unaware if this is currently being produced. The trick is to select materials and thickness, to get the twist just right, to work as desired. Hartzell, very popular with the racing and nonracing Lancairs... Nice photo of one he http://www.ramaircraft.com/Whats-New...-Propeller.htm Thrust comparison he http://www.beryldshannon.com/Hartzell/chart.htm |
#12
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Can you also provide the proper vehichle for the test period?
Nope, I can't even fly, unless of course I talk one of you guys into taking me up. ![]() I find the prospect of building an airplane very interesting. I've studied the skills required, and have decided that I can handle it. I've also studied the time required and found I'm not even close! ;( I thought it might be interesting to play around with building a prop. I own a machine shop complete with design tools, CAM software, and CNC equipment. I have a better than average grasp of high school math, but obviously can't handle the kind of design work it would take to pull of a project like this. I enjoy wrapping my brain around a problem, and coming up with a low tech solution. I don't have the time, or budget to get involved with a large project, but thought a prop might be within reach. After reading the group's responses, I'm still confident I can build one, but I don't think I can design it. ;( |
#13
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![]() Has anybody tried making a flexible prop? Yes. Warp drive makes a flexible prop with a steel rod in the middle that twists the tips with an electric motor, to change profiles for climb to cruise. That is one feature that had better not be copied. I want to say that the IVO prop has this mode of operation. I have not looked at the Warp Drive closely enough to validate what you are saying. The IVO has some drawbacks, however. I don't believe it's compatible with 4 cylinder lycomings (torque pulses are damaging...) and i know of a few who have tried to use the IVO in flight adjustable prop for high speed flight, and found it less than satisfactory. Since the inboard portion doesnt rotate as much, it must produce some "flat plate" drag.. anecdotal reports of a 10 mph penalty on a 200 mph aircraft are what I recall. For the slower planes, this may not be an issue.. Dave |
#14
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In article wtn4e.12908$Vx1.12789@attbi_s01,
"LCT Paintball" wrote: Are there prop styles that can be copied without patent infringements? Try at the Prop Carving website; http://www.wood-carver.com/store.html |
#15
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![]() What about titanium? I think that the lack of titanium bladed props is purely economic. It is a very tough material, so I don't think strength or brittleness would be a problem. Compared to wood, aluminum, and composite construction, it is very expensive. tom |
#16
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i know of
a few who have tried to use the IVO in flight adjustable prop for high speed flight, and found it less than satisfactory. Since the inboard portion doesnt rotate as much, it must produce some "flat plate" drag.. anecdotal reports of a 10 mph penalty on a 200 mph aircraft are what I recall. Thats at least partially true of all inflight adjustable props. For a particular speed and power there is an ideal shape that can be achieved by fixed pitch props. The adjustable (CS) props design their shape for an average effect over the speed range. But the adjustable prop still gives a decent high speed efficiency while giving that extra safety factor at takeoff and landing - takeoff like a slingshot and you can really slow down the plane on landing with low pitch setting. So you have to take your choices - can't have everything. ---------------------------------------- SQ2000 canard http://www.abri.com/sq2000 |
#17
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A number of aftermarket manufacturers make coil springs for racing
cars. Titanium has good retention for a short period but eventually loses shape under high stress - see description at http://www.coilspring.com/performance/auto_racing/ particularly the comment: "Titanium springs are not 'forever'..." |
#18
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LCT Paintball wrote:
Can you also provide the proper vehichle for the test period? Nope, I can't even fly, unless of course I talk one of you guys into taking me up. ![]() I find the prospect of building an airplane very interesting. I've studied the skills required, and have decided that I can handle it. I've also studied the time required and found I'm not even close! ;( I thought it might be interesting to play around with building a prop. I own a machine shop complete with design tools, CAM software, and CNC equipment. I have a better than average grasp of high school math, but obviously can't handle the kind of design work it would take to pull of a project like this. I enjoy wrapping my brain around a problem, and coming up with a low tech solution. I don't have the time, or budget to get involved with a large project, but thought a prop might be within reach. After reading the group's responses, I'm still confident I can build one, but I don't think I can design it. ;( http://ernest.isa-geek.org/Delta/Lib...wIMakeProp.pdf -- This is by far the hardest lesson about freedom. It goes against instinct, and morality, to just sit back and watch people make mistakes. We want to help them, which means control them and their decisions, but in doing so we actually hurt them (and ourselves)." |
#19
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abripl wrote:
i know of a few who have tried to use the IVO in flight adjustable prop for high speed flight, and found it less than satisfactory. Since the inboard portion doesnt rotate as much, it must produce some "flat plate" drag.. anecdotal reports of a 10 mph penalty on a 200 mph aircraft are what I recall. Thats at least partially true of all inflight adjustable props. For a particular speed and power there is an ideal shape that can be achieved by fixed pitch props. The adjustable (CS) props design their shape for an average effect over the speed range. But the adjustable prop still gives a decent high speed efficiency while giving that extra safety factor at takeoff and landing - takeoff like a slingshot and you can really slow down the plane on landing with low pitch setting. So you have to take your choices - can't have everything. Variable pitch isn't only useful over an aircraft with a wide speed range, it is practically necessary for a turbocharged engine. If the engine maintains power up at a high altitude, coarser prop pitch is required to take a bigger bite out of the thinner air. I should be more specific and state a turbo-normalized engine (or supercharged-normalized, if such things exist in great numbers). Point being a powerplant that produces it's rated sea level power at high altitude. |
#20
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I know of two company that sell propeller design software, and there are
some other online, but them seems all to be incomplete, I am not saying this to sell more, just fact, but some don't calculate the Diameter ! one of the most important design criteria, other lack strength and safety calculations... I made my program for my own use, then I have changed it many times to be more user friendly and complete, Rome wasn't built in one day, so I have but in many hours making the program work as I wanted it and by requests from customers, and not least making it work with both US system and metric system, and on computers all around the globe. My program is made for the home builder in mind, it is not that difficult to make a wood prop, if you can make a airplane you can make a propeller, calculate it can be time consuming, isn't that the reason we have computers? all the time we save with the computer... or is it spend with the computer? anyway, Now it is possible to calculate a prop in a minute, make it in a CAD program in 10 minutes, make drawings and templates or even let a CNC router make the prop. (but we have to glue the laminates together) Making it by hand is still an option, and very satisfying when finished, not all have a home made prop in the nose or rear, at the fly-ins! Real Propeller design software cost some, but that is saved in on the first propeller made. then you can make props for your friends too. Jan Carlsson www.jcpropellerdesign.com "LCT Paintball" skrev i meddelandet news:wtn4e.12908$Vx1.12789@attbi_s01... I've been reading every post here for a few weeks. I am absolutely amazed by the amount of knowledge that lives here! With the butt kissing done, I hope you'll excuse my ignorance. ![]() I was interested in the discussion concerning the weight of different prop materials. Has anybody tried to make a hollow aluminum prop? What about titanium? Carbon fiber? What kind of testing needs to be done on a home built prop? Are there prop styles that can be copied without patent infringements? Has anybody tried making a flexible prop? My thinking is that it might be possible to create a prop with a low angle of attack for high power take offs, then have it flex to a higher angle of attack as the load decreases. Could something like that give the performance of a constant speed prop without the complexity and added weight? If I were to play around with different prop designs, is there somebody around here with the knowledge and time that might be willing to test them for me? -- "Don't be misled, bad company corrupts good character." www.LCTPaintball.com www.LCTProducts.com |
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