Experimental sailplane self-launch electric conversion

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sdupre

Member
Joined
Oct 10, 2014
Messages
6
Location
Colorado
Hi all,

I would like to convert an experimental glider to be electric self-launching. The desired major components are: 35 kW BLDC motor, 4-5 kWH lithium battery, a suitable motor controller, and a small in-cockpit control head to control and monitor the system (on/off switch, throttle, a display that shows RPM, power output, battery capacity remaining, motor/controller/battery temperatures, etc.). The exact propulsion system geometry is not critical to the question. Let's say it'll be a belt-driven, rearward folding prop on a streamlined fixed mast. So a nose-mounted FES-style conversion (i.e., from LZ Design) is not an option.

The question: Is there a company, preferably but not necessarily in the U.S., that sells an integrated package of the major components (motor, motor controller, in-cockpit controller, propulsion battery, BMS) suitable for my intended conversion project? My budget for the project is $10K-$15K.

I suspect that I'll ultimately have to cobble everything together for an entirely DIY conversion. But if a vendor offers an electric “flight package” that would shorten my work, it would be a good thing.

I'm aware of Randall Fishman's offerings at http://www.electraflyer.com/price_list.php, even if the website appears quite dated. Just hoping to be referred to similar offerings that would make my project go faster.

Thanks in advance.
 

Riggerrob

Well-Known Member
Joined
Sep 9, 2014
Messages
1,365
Location
Canada
Sorry, but my imagination ran wild when you suggested electric self-launching.
My first thought was an electric winch pulling a fixed cable. Just lay out a kilometre of steel cable and anchor the up-wind end.
Install the winch and a stack of batteries in the glider.
Then I asked myself: “Who wants to carry a kilometre of cable?”
Since few do, my next thought was “How do you arrange an automatic disconnect - to drop the cable - at the top of launch?”
Then my next question was “Can you run electricity - up the tow cable - to power the winch?”

Do I ask too many embarrassing questions?
 

sdupre

Member
Joined
Oct 10, 2014
Messages
6
Location
Colorado
Some interesting thoughts and suggestions -- some more practical than others :)

I'm familiar with the better known brands, including Rotex and MGM Compro. Pipistrel's electric propulsion kit approaches the integrated solution I'm hoping for. But, as expected, their online price list shows that it all comes at a price I'm unlikely to go for. A similar solution could be had for far less, or so I think and hope.

Currently, I'm leaning toward using freerchobby's MP20280 55 KV 45KW BLDC motor and kellycontroller's KHB14401 motor controller. Kelly's salesman says they sell their hardware to MGM Compro. If true, the price difference between the two brands is huge for the same hardware.

Motors, ESC's, and batteries seem relatively easy to get. But some of the “little" components could really challenge my project. For example, an in-cockpit control head that must be small yet reliable and informative. LZ Design’s FES package has a nice FES Control Unit that fits in a 57mm panel hole. (http://www.front-electric-sustainer.com/technology.php). Unfortunately, I can't buy just that component, according to their U.S. dealer.

Or can I? Does anyone know if the LZ Design's FCU or any similar compact in-cockpit control head can be bought separately (anyone has a used one to sell)? It lets the pilot turn on the propulsion system, control the motor speed with a knob, and displays RPM, power output, remaining battery capacity, battery/ESC/motor temperatures, etc.

If not, could an equivalent DIY solution be as “simple" as using a servo tester as the throttle and an Arduino-driven TFT or OLED display and some sensors to monitor RPM and temps?

Then, maybe in a different thread, we can discuss some other fun components, like a folding prop hub. Similar questions there – buy or make? I started looking, and it's looking like a Graal-style (DIY) hub swinging ground-adjustable Ivo Prop blades might be in my future.
 

opcod

Well-Known Member
Joined
Aug 28, 2010
Messages
51
Location
Canada
Kelly ctrl can be fine, but only if you want to save money. Mgm is nearly half the weight and size and uber more important are the data function and logging.
 

Exian

Active Member
Joined
Jul 26, 2018
Messages
41
Location
BORDEAUX
For my self-launch sailplane project, I finally choose motor RET60 and contoller HBC-280120-3EI from MGM compro. I will take delivery directly at AERO 2020 in two months.

Since I am going for a FES type installation, I was at first more interested in LZ design system, but :
- They only sell complete system, but I didn't want their batteries since they don't fit in my 13% thick wings... Their motor and spinner/prop was nice, what a shame!
- They sell to "amateurs" but on the condition that they do the installation/ electrical work themselves for liability reasons (had problems with first customers it seems). This is understandable, but bringing my finished plane in czech republic is still far. And it means you have to design and build exactly for this system in advance, without having it in front of you, which is a nonsense for a single HBA (design is done on the workshop floor!)
- Price, being increased by the labor cost of the custom installation.

I didn't know about the pipistrel conversion kit, but it has the same problem of battery size, cost, and is a litlle to powerfull (but interesting for my next two seat project).
 

blane.c

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HBA Supporter
Joined
Jun 27, 2015
Messages
3,862
Location
capital district NY
Batteries are the heaviest part? If they are shipped at the cost of shipping to say CZ and then reshipped to you the freight is incumbered twice. Getting direct shipping of the cells and assembling your own batteries would cut out the middleman who just assembles the cells into a box of convenient size to him/her not knowing what size box is convenient for you.
 

proppastie

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Log Member
Joined
Feb 19, 2012
Messages
4,436
Location
NJ
=simple solution=to rewinde stator with better insulation...
I can not imagine doing that or defending the necessity of doing that. What should be YELLED is "these vendors lie do not buy their junk."

I doubt designing a 20-30KV motor is as simple as "just rewind the stater".....If you are going to go that route, you are doing a completely separate development project.

Lots of hype, and Youtube of first flights etc. but very little engineering data on real performance.....

We have an Electrical forum ....post your real world flight data......Only "unverified" scraps and teasers so far.

The abundance negativity revolves around my perception of fraud on the part of many vendors in of this section of aviation.
 
Last edited:

John.Roo

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Joined
Oct 8, 2013
Messages
329
Location
Letohrad / Czech Republic
OK, reality....
During flying with my D-14 project I have been using 33 kW motor from Rotex (custom made). Controller MGM 280 A / 120 V. Battery Li-Po from 135 GeBattery cells, 11 000 mAh. Nom. voltage 99,9 V. 27S/5P. 5,5 kWh capacity.
Than I bought MGM 400 A / 400 V and I increased nom. voltage to 144 V. 39S/5P. Capacity 7,9 kWh. The same motor.
Just give me know what exact data from fying do you need :)
 

John.Roo

Well-Known Member
Joined
Oct 8, 2013
Messages
329
Location
Letohrad / Czech Republic
I don´t know what glider are you modifying, but two recommendations:
1) don´t use belt, go direct
2) prop on mast = more drag = calculate with a bit higher power (add some reserve).
If is one seater than 35 kW for self launch should be OK.
 
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