Our latest arrival:
The brand new Schuebeler HST-propulsion-system

With the DS-94-DIA HST & DS-77-DIA HST Schuebeler Composite launches a completely new jet propulsion system. The system is based on a new 12-blade axial compressor wheel which is driven by the all new Schuebeler electronic commutated motor.

The 128 mm axial compressor (DS-94-HST) generates a surpassing compression ratio and can therefore be integrated much more efficiently in huge jet models than classic ducted fans. The rotational speed level is only 26.500 rpm at an impressive exhaust speed of 95 m/s and a thrust of 10 kg. This high thrust impulse is therefore generated by a high exhaust speed and a high inner efficiency of the axial fan stage. In figures that means you can integrate this fan in jets up to 11 kg and an exhaust diameter of just 105 mm.

The design of the 12-blade axial compressor wheel is based on speed ratios which are similar to the ratios of a full scale turbofan. That results besides a high efficiency in a perfect optical scale appearance and a sound which can only be compared to full scale jet engines. A silent whispering and fizzling of the axial compressor at idle rpm is predominated by an impressive jetstream noise coming from the exhaust at full throttle.

An extraordinary challenge was the development of an electronic commuted DC motor that perfectly fits to the axial fan. The 12-blade compressor demands an impressive torque of 2,2 Nm at 26.500 rpm which can only be generated by a high torque motor of high diameter and shorter length. Consequently the new DSM 6740 Schuebeler motor has a diameter of 67 mm and a magnet length of 40 mm. This motor is fully integrated in the axialfan to assign a huge area for the main airflow. In addition to that the motor is perfectly.

Cooled and needs no efficiency decreasing internal ventilator. The motor is based on a two pole design to allow a flexible fit of the motor characteristics to the needs of the axial fan. Nevertheless the windings sit in a 12 slot stator to increase the torque and to avoid any winding deformation at high temperatures. The magnet is attached to a sheeted magnet holder and reinforced by a bandage made of IMS carbon fibre which allows a high rpm tolerance. The whole motor design was optimized in respect of excessive heat tolerance and of course a high efficiency even at high currents. The mechanical design of the Schuebeler DSM 6740 motor is based on established mechanical engineering and distinguishes itself by a shaft mount consisting of a fixed bearing and a prestressed floating bearing. Front- and endbell are fixed by 8 countersunk head screws, all surfaces are protected by hard anodizing. The result is a very high durability in combination with a low mechanical soundscape which allows the whispering of the axial fan to predominate even at idle rpm.

The conjunction between motor and axial fan is made by 4 handmade carbon stators which also guide the 3 motor phases through the UHM carbon sandwich shroud. The conversion of shaftpower to streampower is accomplished by 12 handmade carbon rotor blades which sit form-closed in precision aluminum swivels.

The DS-94-DIA HST propulsion system is 100 % made in Germany.

Technical data DS-94-DIA HST with DSM 6740-600:
Inner shroud diameter:              128 mm
Fan swept area:                        94 cm²
Weight:                                   1380 g ( incl. wires, connectors, Secure Fan Fix and DSM 6740)
Thrust range:                           86 – 98 N
Exhaust speed range:                88 – 95 m/s
RPM range:                             24.800 – 26.800 rpm
Input power:                            5,8 – 7,0 KW (up to 7,5 KW in narrow ductings)
Allowed battery:                       13 – 14S 6000-8000mAh
Overall efficiency:                    66 – 67 %

Click HERE for more info on the DS-94-HST Fan

Technical data DS-77-DIA HST with DSM 6740-650:
Inner shroud diameter:              120 mm
Fan swept area:                        77 cm²
Weight:                                   1360 g (incl. wires, connectors, Secure Fan Fix and DSM 6740)
Thrust range:                           80 – 92 N
Exhaust speed range:                93 – 100 m/s
RPM range:                             25.650 – 27600 rpm
Input power:                           5,6 – 6,9 KW (up to 7,5 KW in narrow ductings)
Overall efficiency:                    66 – 67 %

Click HERE for more info on the DS-77-HST Fan

Videos of the HST Fan in Action:

Maiden flight of the DS-94-HST in a ~11kg heavy F-20 Tigershark

The HST Prototypes in action during the 2009 Salzburg EDF meet

With larger and more powerful EDF power setups beyond 5S the need for an anti spark circuit becomes important.

Although many modern ESC have either an in-build spark eliminator (example: Kontronik Power Jazz 63V) or come with a separate anti spark connector (example: HET 100A ESC), there are still ESC’s out there which come with neither (example: Hyperion 90A).

This article is intended for modelers which such a ESC’s.

What does an anti spark circuit / arrester do?

Basically it eliminates the spark/arc which is created between Battery connector and ESC Connector when initially connecting a high voltage battery to your ESC.

Why is there are spark?

The current spike which is generated when you close the circuit (connect the battery) is the cause for this spark.
The spark usually becomes properly visible (and audible) with setups of more then 5S.

The higher the voltage of the setup you are using the larger and louder the spark will be.

So why not spark away?

Although we have not experienced this by ourselves yet, there are reports from modelers that the voltage spike can permanently damage the ESC.

Fact is however that the spark will damage your connectors as they are slowly eroded away with each connection you make. This will in return increase the electric resistance of the connector possibly causing it to fail due to heat build up one day.

What can be done?

There are multiple DIY solutions available in the net, ranging from simple to highly complex
Here we would like to describe a simple solution by using 1 resistor only.

As mentioned above the spark is generated from the initial high current spike when connecting the battery to the ESC.
To eliminate the problem the ESC needs to be slowly "charged up" before the battery is connected fully.

The "charging up" is done by loading the electrolytic capacitors on the ESC (see picture).
 

Each ESC comes with 2 or more of these capacitors. Once they are charged up the battery and ESC are in an equally loaded state which means that no current spike and therefore spark will be generated.

Building the Spark Eliminator

Items required:
- 1x short piece of silicon wire
- 1x Resistor of suitable value for your ESC
- 1x heat shrink tube

If you are using Gold connectors between esc and battery:
- 1x male + 1x female connector (same type as you use between ESC and Battery)
   example: 6mm gold connector as shown here

If you are using Deans connectors between esc and battery:
- 1x small polarized connector pair (e.g. mini deans)

Before you start shopping for your resistor you need to calculate the size required for your ESC/battery combination.

Although in general a small Ohm resistor with 1/2 to 5 watt will work you can adjust the value depending on your ESC and intended "charge time".
Click here for a link to a great tool which will do the calculation for you depending on battery size, capacitor and charge time (we will describe the calculation method another time).

Now you can start building. Depending on the connector you use between ESC and battery follow either diagram below.

Using Gold Connectors:

Using the spark eliminator:
- Make sure the male/female connector we prepared above is only connected to the ESC via the cable/resistor
- Connect the minus pole of Battery to minus pole of the ESC
- Connect the battery plus pole to the male/fame connector
- What 1-2 seconds
- Connect the male/female connector to the plus pole of the ESC

Using Deans Connectors:

Using the spark eliminator:
- Connect the small polarized connector between battery and ESC first
- What 1-2 seconds
- Connect the battery to the esc with the main connectors.

Whether you are using the deans or the gold connector version (or any other connector), in all cases there should be no spark. If there still is a slight spark then the capacitor on the ESC are not fully charged yet. In this case wait 1-2 seconds longer the next time before you make the final connection.