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Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Patrick wrote ...
in a hover, we have 100% slip, right?
So how are we to figure on pitch? i keep thinking about static thrust and screw threads in wood. but my brain breaks...
We don't have 100% slip compared/relative to the accelerated column. We will have some slip, though. The thrust of the accelerated column in newtons MUST be 9.81 times mass in kg of 'copter when hovering.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
ok so we need to know the inhaled velocity and exit velocity. (since we cant know the prop plane velocity) so what would the pitch be ? In the range of 5.5in for 14" dia, to 9in at 9in.
so it seems in RPM changes from 6000 rpm to 1500 rpm, we see about 4.5 in difference. we cant interpolate perfectly, but id be suspicious of a pitch number that falls out side a similar number.
email:
Hi Patrick, I apologize for the data being unavailable for so long. We found some errors and are working on resolving them. The updated data should be available in January. I have attached the old data for your reference. Please note that results at low efficiencies do not match test results very well.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
Ash Small wrote ... Well, if we have three 26 inch props, we divide total mass in kg by three then multiply by 9.81 to get thrust required from each prop in newtons.
Wha is the proposed all up weight of the 'copter? How many props are we planning to use at the moment?
the tri-copter is more of a pain, so ill keep it a toy. lets count on quads from now on. there easier to verify, tune and so on. I have multirotor and other props, that i could chop up in 1 inch pices, from tip to root. measuring the dimensions and profile as i go.
As for the all up mass, were entering the 10-20kg range. no more small stuff. ive learned enough from these recent machines to realize its distance/duration and payload that are needed for a useful civilian drone.
the specifics of what i want are: 19g/W effcient motors or there abouts. lipo batteries, 20Ah or so (not sure) 26 -29 inch rotors.
To get ultra long range, i may add a alcohol/piston hybrid system.
There are more than 800 drone companies in the US, most of them basically like the child-toy ones, just with a 70,000$ price tag. And I just know there's' a dot-com-like machete on its way. I plan to survive.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
Patrick wrote ...
Ash Small wrote ... Well, if we have three 26 inch props, we divide total mass in kg by three then multiply by 9.81 to get thrust required from each prop in newtons.
Wha is the proposed all up weight of the 'copter? How many props are we planning to use at the moment?
the tri-copter is more of a pain, so ill keep it a toy. lets count on quads from now on. there easier to verify, tune and so on. I have multirotor and other props, that i could chop up in 1 inch pices, from tip to root. measuring the dimensions and profile as i go.
As for the all up mass, were entering the 10-20kg range. no more small stuff. ive learned enough from these recent machines to realize its distance/duration and payload that are needed for a useful civilian drone.
the specifics of what i want are: 19g/W effcient motors or there abouts. lipo batteries, 20Ah or so (not sure) 26 -29 inch rotors.
To get ultra long range, i may add a alcohol/piston hybrid system.
There are more than 800 drone companies in the US, most of them basically like the child-toy ones, just with a 70,000$ price tag. And I just know there's' a dot-com-like machete on its way. I plan to survive.
Sounds good. I've had a drink or three. So we agree on 30" props then?
Registered Member #4266
Joined: Fri Dec 16 2011, 03:15AM
Location:
Posts: 874
I think the foumla is pitch or more cut deepth, say about 10mm RPM say 10,000 30inches 750mm
if the tip of the blade is traveling 750*3.142 = 2356(2.3meters) and it is doing that at 10k/rpm, we have 23km/min / 60 = 383m/sec, we devide that by 10mm cut, from front to back of blade, and messureing from the tip(can use parts along the length) we get 38.3m/sec, if the effeincy is 40% thats 15.3m/sec linear flow, at dia of blade tip 0.0471(i think)m2 = 0.72063m3, at 0.72063 * 1.22kg = 0.879kg or about 8.79N
1/2mv2 = 102.88kg of thrust, assuming that the tip is a magic float tip blade, or divide by some ratio, maybe 102/6.28 to get the kg of lift.
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Propeller Physics and VABs Program.
