EDF Power systems and choices - 70mm
Time to outline the various things I have discovered/learnt on my detailed journey across model aircraft... and EDF's...
How will you power your EDF jet? That is sort of the main topic of it all, and a list of many options that there are, and what I found and think of them.
This section will only do 70mm jets, and a touch on 64mm I guess....
Last edited by PeterVRC; Sep 16, 2013 at 08:16 AM.
Most PNFs come with 5 blade fans of very budget/low quality. Lucky if balanced at all, more likely just bolted all together and run "as is" to BURN in the blades that rub the housing! LOL
They are also pretty well always underpowered - mainly in older generation models, so there are more recent releases getting better in power terms - still terrible in assembly/quality terms, though not as bad as the older generation stuff.
But take note.... unless you read up on a specific foamie, in most cases you won't truly know what is in it. So read around forums FIRST to get more info on planes you want to buy! Some are terrible! Some are great!
I am only going to cover "High blade count fans".... not 5 blade... 6 blade... or Wemo (which are a great fan really - and note they have just released a range of high blade count fans too)....
High blade count fans means 10, 12, 14 blades. They cause a far more 'silent' airflow and this allows you to hear the 'white noise' of the airflow through the aircraft's ducting paths - inlet and exhaust. The result is a far more "jet-like" sound.... it is the "whoosh" portion of high speed air of a jet engine, but missing the combustion "roar" they have (real ones). But it is the best we can get in EDF's.
Low blade count fans sound like a garden leaf blower!!! (A Wemo sound result, even though a lower blade count fan, is some amount between the two)
Whilst Wemo can sound ok, they cost a lot more than the main "Chinese" high blade count fans around. Those being ChangeSUn (CS), XRP (probably made by CS), and Lander (also sold as DrMad by HobbyKing).
Chinese around $17, Wemo around $50 - but the Wemo is a far better designed and produced, quality, product!! The CS etc are 'good' and their low cost swings the scales notably in their favour.
High blade count fans put more load on the motor than a 5 or 6 blade 70mm fan does, so they need to run at lower RPM to produce the same thrust as the 5 or 6 blade fans. This means you need to know what motors are suitable and what results you will get - according to what you want, or can afford in power/battery supply.
Last edited by PeterVRC; Sep 18, 2013 at 06:37 PM.
The fan range
CS making 10 and 12 blade fans
XRP making 10 and 14 blade fans
Lander making 10 blade
All the 10 blades are as good as being an equal load/result.
The 14 blade is bit higher load above that,
The 12 blade is a bit higher load again above that.
One key point to ME is the rotor's motor shaft adaptor. I want a 'grub screw' attached type - the other form is a "collet" type, which clamps a split shaft adaptor onto the motor shaft. Collets can actually be fine - more so for just 'assemble and use' fans, but they are a bit harder to Dynamic balance. Which is why I wan to use grub screw adaptors.
Only the Lander comes with grub screw types now. But you can get adaptors for the CS and XRP from 3rd party sources. Getting the Lander parts to make up a fan is 'messy'... you pretty much need to buy the rotor and adaptor from HobbyKing and then a housing (Freewing 70mm) also from HobbyKing.
The Lander shaft adaptor also fits the CS12 70mm fan. So you can use it (for $4) instead of the CS12 collet. BUT, the CS12 housing has an 'issue' (later....)...
The Lander grub screw adaptor is good quality. The CS ones (not around now) were average/so-so quality, Generally OK, but not perfect. 3rd party ones that you can also get are costly, but are also great quality and precision. (From ExtremeRC or Tamjets).
So.... what to choose???
The CS10 and CS12 can only fit up to 28mm motors.
The XRP10 and XRP14 can fit up to 30mm motors.
The Lander, seeing you need to use a Freewing housing, can fit up to 29.5mm motors.
The benefit of being able to use larger diameter motors is a MUCH wider range of cheaper, but still good, motors. Mainly the Lander range of motors (at the moment), which are also badged as CyclonePower and DrMad (DrMad being the cheapest form of them).
So at the moment the 'assemble it yourself' best fan solution is the XRP10 or XRP14, which also have 9 stator housings of very good design (and 30mm motors). BUT you need a 3rd party adaptor for them. bah. Unless you just assemble them with the collet adaptor and the extra balancing difficulty of that.
The CS12, which allows use of the 'good' Lander shaft adaptor is a slightly larger rotor diameter than all others! This locks you in to housings you can use - you can not use their stock one if you want to use the larger motors as the CS12 housing is only 28mm motor capable. The rotor can fit into the Freewing 70mm housing and the Dynam 70mm housing (hard to get on their own), but the blade tips are VERY close to the shroud due to that larger diameter! This means you need to centre the motor PERFECTLY (which is always a good thing to try to achieve anyway), and make sure the housing has ZERO pressure on it when installed - so it does not distort its shape even a micron! And even then, if you run very high power - say over 1300W - it can just end up scraping the housing a bit at times anyway!
You could trim the rotor down a bit..... to reduce its diameter.... but that is very hard to do properly, and basically reduces its blade area, and thus load/thrust, so its end result heads more towards a CS10 - though still has more blades for its slightly different sound result.
Once again, the current state of fans makes the XRP10 & 14 the two best choices:
Great housings (and 9 stator), strong and can take 30mm motors. BUT, collet adaptors and need you to buy grub screw type if you want that.
And just on that grub screw adaptor point..... Third party cost about $15, and if you add that cost to the fan then you can NOW buy the Wemo Evo high blade count fan which is a grub screw adaptor AND a much better design and quality fan unit! The XRP totals $32 and Wemo at $50.... still $18, but that amount is worth the difference you will get. When at $32 difference it leans towards CS/XRP solutions.
Last edited by PeterVRC; Sep 18, 2013 at 06:50 PM.
There are some CHEAP and workable options, then some medium cost options, and the costly options.....
One of the main criteria I have is to use at least 4mm motor shaft motors! NOT 3.17mm, as it is weaker and can bend FAR easier! (There are a few 5mm shaft motors too - just 1 or 2)
HobbyKing L2855 Series Outrunners
At the lower end the HobbyKing L2855 series motors - which are outrunners - have prove to be great value for money! VERY cheap, but still great value!
$13, and they come in 2100kv, 2300kv, 2800kv versions.
All can run to near 60A and survive fine. All have poor bearings that may, or may not, already be so-so when you get them(!), but that is not a big issue really. All are 4mm shafts. They are also not balanced very well but in general can work fine as they come - but if you can balance a motor then it is use to do that too!
Lander / CyclonePower / DrMad 29mm Inrunners
High Power at low current
I was experimenting with various setups to try to get high power for low(er) Amps in Twin 70mm jets (My Su-35 and Me-262). You basically need more VOLTS to achieve this.
But I also wanted a reasonably cheap way to achieve it - which is not totally possible, but I did still find the 'best and cheapest' way to achieve it!
The DrMad 2200kv motor, which is a 1600W capable motor. $35 approx
At that KV you need a 'lower load' Rotor so that you can run the higher volts.
With a CS/XRP 10/12/14 setup that 2200kv would run on 6S for about 1300W (1500W peak) - this is 65A to 70A region for 2.0Kg or so thrust. That is a LOT for a twin.... 130A to 140A !!
Or that combo can run on 5S for 1100w region at 56Amps area, for 1.5Kg Thrust. = 112Amps. In-plane thrust will be down from the "3.0Kg potential" and more like 2.5Kg. Not that great for planes of this size.
If you use the Wemo Rotor - Pro or EVO - then you can run 7S and 8S on this motor for very efficient results! The EVO gives a bit more power/load/thrust an sounds better - so that is the one to use. It costs about $22 for a Wemo EVO Rotor and Adaptor, which you can run in a $6 Freewing housing perfectly fine. So at $28 approx, it is more than a CS/XRP at around $18. But it is the best way to achieve this goal....
7S 50Amps 1200W 1.85Kg thrust. So 100Amps total... MUCH more viable! And a good thrust number for that too.
And you can use the HobbyKing SS ASeries ESC's, or the HobbyKing Red Bricks', which both can do 7S and are CHEAP. But to have good leeway I use the 90/100A version(s). About $25 each.
This will give approx 3.1Kg to 3.3Kg in-plane for most cases. Plenty for this sized jet.
But on 8S it goes ballistic!!!
8S 67Amps 2040Watts!!! 2.65Kg thrust !!!
Now this is a HUGE Amps number total for a twin. 134Amps, but at least it is no worse than the 6S CS10/12/14 combo. Plus, when you run it at the TRUE power area you would use, it is only around 55 Amps region. 110Amps total.
Using the FULL power capability would be rarely needed, so it is like aving some "Super Boost" possibility that it has available, LOL.
To match the 7S output the Amps would be in the 47Amps area... 94 Amp total, of 8S.
But the BIG issue with 8S is that you need to use HV ESC's then!! And they ALL cost a LOT.. even "cheap" ones! About $84 area each. So you really only want to use 8S if you really WANT... or NEED.... that TON of power capability!
You also need to use it sparingly and short term, to protect the motor!
The 7S setup of this combo is very well suited to all typical 70mm twin jets!
So it is CHEAP.... has very good EFFICIENT power/thrust.... and still sounds great!
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