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250 Detail program description - Ring limiter

Control of Voith Schneider propellers in model ships

Scroll with the selection keys on the left or right touch 
pad to the menu option »Ring limiter« in the multi-
function menu: 

MIX active/phase

MIX-only channel

Dual mixer

Fail-safe adjust

Teacher / pupil

Tx. output swap

Profi trim

Trim memor y

Telemetr y

Channel sequence

Multichannel

Ring limiter

MIX-only channel

Dual mixer

Swashplate mixer

Fail-safe adjust

Teacher / pupil

Tx. output swap

Profi trim

Trim memor y

Telemetr y

Channel sequence

Multichannel

Ring limiter

Tap briefl y on the center 

 key of the right touch 

pad to open this menu option:

R I N G   L I M I T

4

4

9

11

SET

4

Input

3

3

3

3

X

Y

4

10

12

X

Output

Y

OFF

OFF

OFF

Œ

This »Ring limiter« is primarily intended for the 
control of up to three so-called Voith Schneider 
propellers in ship models. These are positioned 
beneath the ship where they are exposed to a free 
fl ow of water in all directions. The control of these 
drives and turning their vertically oriented propeller 
blades is done with two servos per Voith Schneider 

propulsion unit whereby, for mechanical reasons, 
the propellers of this type offered by Graupner under 
order nos. 2358 and 2358.BL have a maximum 
control travel limitation of 4 mm each. 
As long as the joysticks for forward/reverse and left/
right are operated individually (see section "Column 
Input") this is no problem because travel for the 
two servos can be appropriately adjusted, both 
mechanically as well as in the »Servo adjustment«
menu. However, this becomes problematic when, for 
example, one joystick is 100 % forward and, at the 
same time, the other joystick is pushed completely 
to the right to arithmetically produce a 141 % sum for 
the two servo travel vectors. The mechanical controls 
of the Voith Schneider propellers will collide with their 
limits; in best case only drawing an unnecessary 
amount of electric current, in worst case causing 
damage or even bursting the linkage..
In order to avoid this problem, the 

mc-20

 HoTT 

transmitter has a maximum of three "ring limiters" 
available in the "SET" column of this option's fi rst 
display page (see fi gure at left) that can be switched 
"ON" or "OFF" individually. In the fi rst line on the 
setting page for a given "ring limiter", its maximum 
travel can then be set for a range of between 25 and 
125 %. The second line provides a setting for the size 
of limitation of overall defl ection between:
  0 % circular limit ( )
100 %  no limit ( )

(limitation is strictly a matter of the given 
joystick's mechanical stop)

The adjacent sketch illustrates the 
effect for a 0 % setting. The cross-
hatched area of travel is curtailed 
and appears as a "dead zone".

With the standard preset control mode 1, all three 
ring limiters are pre-assigned to inputs 3 (forward/
reverse) and 4 (left/right) which are actuated by the 
left joystick. However, this pre-assignment can be 
replaced anytime by any other transmitter control 
combination. Use the selection keys on the left or 
right touch pad to move the marker frame to the 
desired value fi eld then briefl y tap the center 

 key 

of the right touch pad:

R I N G   L I M I T

4

9

11

SET

4

Input

3

3

3

3

X

Y

4

10

12

X

Output

Y

OFF

OFF

OFF

Œ

4

Select the desired control channel (1 … 12) for the 
value fi eld now displayed in inverse video by using 
the

cd or ef selection keys. However, do not 

forget that if a control channel in the range of 5 … 12 
is selected, it must also be assigned to a control in 
the »Control adjust« menu, see page 108. Briefl y 
tap the center 

 of the left touch pad or the center 

 key of the right touch pad to conclude your entry.

In principle, the other inputs are to be handled in the 
same manner.
A tap on the 

cd or ef keys of the right touch pad 

at the same time (CLEAR) will reset the active value 
fi eld back to its given default value.