TOPIC: e-HG NZ style

Hi All

Well as far as I know this will be the second e-HG to be built in New Zealand. The first can be seen by searching YouTube for "Callum22".

The world pioneer (I think?) for e-HG is Reidar Berntsen's team in Norway and they called their system e-Help to ensure people understood it was for assisting hang gliding flights, rather than as a method of flat-land launching.

But that's enough on Hang Gliding!

My rig uses the following:

Motor: FreeRChobby (China): MP12090 80kV 15kw ~3kg motor. This could be relatively easily rewound but I haven't as yet (after I burn it out )

ESC: Flier 22S 320Amp running factory V3.0 firmware (I tried V3.1, o' the frustration!)

Prop: 34" x 18" 3-blade CF folding. Custom tweaked by Manfred of MAGCAD during manufacture to have a pitch of 18" (normally 22.5")

Prop hub: DIY milled aluminium (handy to have friends!)

Controller: DIY Handset/Pot with a skydiving Bite-Switch (its actually what it sounds like), with these inputs processed by a Pololu servo controller (adds some safety smarts and timing etc)

Chassis: Welded aluminium rectangular extrusion (70mm x 17mm) with lightening holes to fool me into thinking its light

Wiring: ESC/Motor run, 2 x 8AWG PVC sheathed vehicle audio cables in parallel for each motor phase - don't want I2R losses! Rest is 3 x 12AWG silicone from Hobbyking (HK)

Connectors: XT90 x 10. Master "key" AS150 anti-spark connectors

Batteries: HK Zippy Compact 8 x 5.8Ah 7S. 4 in parallel to make 2 banks, which are then in serial (4P2S). Total pack: 14S (~50V) 23Ah.

Suppliers:
- FreeRChobby
- Flier
- MAGCAD
- Hobbyking
- Jaycar
- Pololu
- RS Components
- Local laser cutting crowd
- M10/Bunnings
- Mate who has access to mill and TIG welding.

Software:
- Sketchup (3D/CAD)
- Polulu app
- Flier ESC PC app
- Excel

Stage this is up to. HK are "Processing" my order for 4 lipos packs. I can then check my calcs for 14S in practice. If need be I can order the last four lipos in the same style, but a 6S or 8S (less Volts, more Volts).

I hope this ramble is useful for someone. Also I would really welcome feedback if I've had any 'duh!' moments

Cheers,
e-HG (aka: argoHG, aka: Brendan).

Just to welcome you to this forum , and to say thanks for the Info , We all like to see the different ways of achieving our own project dreams so its always nce to pick up on new ideas and methods the ultimate goal being common shared knowledge and ideas . So just wanted to say thanks for joining our forum and even more thanks for sharing your project with all our members and like minded souls .

Hi Guys

Well it works And although unplanned, it works in the rain too

Proof you say? Well here we go:

I also did a "making of..." vid, its here:

What a blast to fly! I've got quite a number of tweaks to do but great to have the maiden flight behind me.

Cheers,
Brendan.

First attempt and everything works... that's a rare "animal" - Lol. Congrats Brendan. It looks really nice. Good job

Thanks, Gamba.
There was a lot of ground testing first, but super pleased how it went on the day!
Cheers

Hi and nice work!

I just got the freerchobby motor and am testing now with an MGM controller. How did you burn yours out? did it have a temp sensor? How much power DID you get out of it as it does not look like it can do the job... thanks, Peter

ozeflightclub wrote: Hi and nice work!

I just got the freerchobby motor and am testing now with an MGM controller. How did you burn yours out? did it have a temp sensor? How much power DID you get out of it as it does not look like it can do the job... thanks, Peter

Alas, no motor winding practice for me - the freerchobby (fRCh) motor keeps going, no matter how much abuse I give it

Jokes aside, I've only run it up to 7.6kW and it got flat-white warm. In other words, I could leave my hand on it (my temp sensor) indefinitely. If you want to heat your motor up, run it without a prop! The Io (no load) heat stays with the motor and it gets up to "hot" pretty quick. Also to mention, the Flier ESC only got lukewarm at full 7.6kW.

I'm tempting fate, but the motor really feels solid. Given I'm only running it up to half-full-power, it should do. In fact, given this experience I've asked Lisa of fRCh if they would consider building a 10kw motor - MP12050 let's call it.This could get it down to 2kg in weight with the same usable output. She said they will consider it after Chinese New Year.

I've done a bit of testing now and can report thrust/power results. I'm pretty confident in these numbers as I went to a bit of trouble to get them. Here they are:

Falcon Prop 34 x 10
Static-Thrust: 28kg
RPM: 4500
Amps: 122
Volts: 54.1
Watts: 6.6kW
KV: 83.2

MAGCAD 34.5 x 18 x 3b
Static-Thrust: 27.5kg
RPM: 4380
Amps: 140
Volts: 53.0
Watts: 7.4kW
KV: 82.6

AeroStar 32 x 12
Static-Thrust: 22kg
RPM: 4530
Amps: 107
Volts: 54.0
Watts: 5.8kW
KV: 83.9

A couple of interesting things coming through. See the 'commutation-slip' coming in as the load increases? In other words, the bigger the prop the lower the KV. Also useful to see the effect of pitch. Changing pitch by itself doesn't effect thrust, but it sure loads up the engine. That bloody expensive MAGCAD should have been at a pitch of 12" or 14". I'm wasting kW with an over-pitched prop. It also shows that a $100 beechwood Falcon prop is pretty damn good! Takeaway learning - do your tests on cheap props before getting carried away with eye-candy carbon fibre!

Speaking of props, what pitch do you guys use? Given PG speeds, you would want pretty low-pitched props yeh? Also, I think I saw you guys put out a vid of a folding CF prop, mind me asking where you grabbed that from?

Cheers, Brendan.

Hey Brendon.. thanks for the reply. Interesting.

We really need 15 kW for our foot launch off the beach and it the order of 50kg of thrust, so I'm suspicious still of the freerchobby motor.. And I can't get the motor up to full power as I get a 'hall sensor error'. Not sure if they gave me the 27 kv motor instead of the 55 kv. I've asked for some help, but so far it's quiet.. prob cuz of the New Year thang.

the folding prop is from Bolly and it's a nice prop but big - 1.37m and a pretty large pitch: 22. the folding mechanism is from the airtime guys in Melb from memory who no longer do that stuff.

I've tried other motors including the url=http://revolt.org.il]revolt[/url]out of Israel.. check them out.. but they are heavier. btw I have a throttle made for a HG bar. thumb type but it straps to the bar. not great for me but you may like it.. I'll send a pic a bit later..

good luck.. Peter

Ops replied to your other post. while you were here

Ah Bolly, yeh started with them. As you say they aren't into that anymore. So that was actually a Mossie prop? Yep big.

Will answer more on your new thread

Rain stopped long enough to carry out eHG flight#2, this time in almost nil-wind conditions. It can be seen here: and here: doarama.com/view/1900526

Bit disappointed with climb-rate. At WOT I got +0.4m/s (79fpm). Airspeed was 31km/h (17kts), give or take. I had to have WOT for most of the flight and with my 11.5Ah 14S system I got a ten minute flight. I need to buy the other half of my battery set and I think increase the propeller diameter up a couple of inches (go to 36").

Man it was a hot day. Not often that a landing hazard is sunbathing folks on the beach!

Did something wrong in yours calculations between the real work?

Luckily I used my GoFly vario to log my flight to XCSoar on my phone. After I analysed the IGC file vario results I saw I had better climb-rates than I 'felt'. Two things I wish I'd done differently: 1) Left all my expectations of flying this familiar site at home (I'm so used to flying this site with wind and good lift!), 2) Just concentrated on getting height by doing lazy climbing circles, instead of trying to have a normal distance flight.

But yes, the thing I under-estimated was dynamic thrust. I found yet another calculator that although very simple, represents the effect of increasing airspeed on thrust produced (it's attached to this post) . It ignores the 'spooling-up' effect of an electric motor as the load comes off it, but even if I put in the maximum RPM the motor will run at (ie: no-load) I find the thrust at my flying speed to be down to 18kg. Its of course an easy fix - increase the pitch of the prop. I'm thinking, a prop of 12 or 14" (same diameter). But to do that I'll need to add more lipos to cope with the increased current draw during static conditions (no airspeed).

Along with the dynamic thrust calculator, I've attached jpgs of the SeeYou plots

EDIT: Can't attach xlsx files. Here's a link: goo.gl/yI8voK