AMP draw is slightly higher but so is thrust, I can add them to your kit if you would like. We also will have both prop size available on the store if you want to try the other.
+1 for the higher pitch if it doesn’t have too much negative effect.
@Pdwhite, please do ship my kit with the higher pitch props. I ordered a batch 2 kit. Will this message suffice or is there a preferred method for specifying this detail?
Assuming 19kg thrust per prop, each prop will require around 4.3kW of mechanical power. With the drive as is, the efficiency of inverter and motor will not exceed 80%, it will need around 5.4kW of electrical power, so the ESCs will each need to handle 121A on a good day, and the batteries 484A.
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Ill get that updated for you.
I have tested the A draw and it is not 121 but closer to 110A. The ESC can handle that current with adequate cooling (which it has and its mounted on the arms and have plenty of airflow during flight). The batteries also can easily handle that current also. Even with just two Bonka 22000mah packs, they have a continuous discharge of 550A and a burst discharge of 1100A. http://www.bonkapower.com/a/Multicopter/20150825/11.html
Hello Paul
You are suggesting 22x10 CW and CCW wood pairs
What is the limit in diameter ?
Is a 23x08 (CW or CCW) passing physically in rotation (free tip airgap) ?
Louis
A 23in will just barely fit. There about a 1.5 gap between props now.
Is it worth specifying a 100A ESC for the higher thrust prop? It would then put the current within the 10 second rating of the ESC.
I have been investigating prop sizes and a 22 x 10 prop can typically develop 35lbs thrust @ 7450 RPM which gives a total of 140lbs of thrust. As yet I haven’t found any motors that can deliver that rpm for a 22 x 10 prop even the best American motors by KDE can’t deliver that power. Is the 155 lbs max thrust a judgement call or has this been measured?
There has been a change to show an optional 22x14 prop, which should deliver the originally specified thrust, albeit with a higher current draw. Paul has suggested that this was just over 110A per motor with the 22x14 prop (I get closer to 120A, but I am assuming a lower efficiency from the Block Commutating ESC drive). Getting 19kg of thrust from a 22x10 propeller was ‘optimistic’ - It confused me for quite a while (I thought that I had missed something in my efficiency calcs, as it put them at over 100% at some points). There are quite a lot of incorrect manufacturer quoted figures in the battery, ESC, motor and propeller specs that you get for RC stuff (always optimistic), but that’s because they don’t normally get used on something that is connected to a human. The paramotor is a prototype, so test it very hard on the ground with your setup before strapping it to your back (particularly battery, ESC and motor). Take a typical flight of full thrust for 2 minutes (900ft climb), then 40% for how long you would want to altitude hold, and play that profile in to the paramotor. Personally, I would put a bigger ESC on the motors, and one which is phase and bridge current limiting. Normal ESCs don’t understand inertia, so they will often voltage control only, and exceed both battery and phase current limits during throttle transients.
What motor can drive a 22x14 prop to produce a thrust of 18kg?
There are a number of >5kW machines around. Ideally a 7+kW machine would be best, just make sure that the bearings are arranged such that they can react push force (most are set up for pull only)
I have only found ones made in China and reliability looks questionable can you suggest some that might be suitable.
I can’t imagine that you will find anything that isn’t made in China, even if it has a different badge! The original (non-custom) machines were these I believe GA6000.8 GA6000.8 They claim 6.8kW with 180rpm/v gain. No idea if the custom machines have the same continuous power.
If I was looking to launch from between 4,000 - 10,000 and fly up to 12,000 would different props start to be a good idea?
I just tried to figure out how the new 150 KV motors will work…
This is the original 180 kv 12s version:
This is the new version 150 kv 14s:
And this is the 150 kv 12s version - looks like they have to use the 22x14 propeller:
There is a possibility that the 150 kv 12s version with the 22x14 props will be more silent and more
effective… Maybe we need then really the 100 A ESC’s!!!
If you want the higher pitch it would be best to lower the kv even more and stick with 14s. I agree the higher pitch would be more silent because you could use lower RPMs but not sure how that would effect efficiency. There’s been a lot of talk on hear about using less pitch to improve efficiency but it’s all been just talk because nobody has actually tested and reported. Lower RPM would reduce tip vortices but higher pitch would increase them so I don’t know which way the scales would tip here for efficiency.
Found this company they seem to have really nicely built props. I for one would be willing to spend $400 on a nice set of props that will last and be quieter. But i do think we will need new standoffs. This company says they will drill holes to suite the customers requirements for mounting. @Pdwhite
https://shop.mejzlik.eu/detail/propeller-22x74-p-3956
Perhaps we could do bulk order and get the price down, first someone should test a set.