wilysloth

Vintage servo is now reversed mystery

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In the process of returning my vintage Blackfoot to running order I have encountered a mystery.

Back in the day my Blackfoot steering was set up as follows:

  • Acoms AP227 Mk3 Techniplus transmitter.
  • Acoms receiver (I don't have the model number to hand).
  • Acoms IC AS-7 servo.

The steering worked correctly.

Fast forward to now.

The Acoms transmitter is no longer in working order so has been replaced with a Core RC Code 2.4G FHSS 2 Stick 3Ch transmitter (CR151) and a Core RC Code 2.4GHz FHSS receiver (CR152). The Acoms servo remains.

The Blackfoot was completely disassembled and reassembled according to the manual and the servo is in the same position/orientation. However, the steering is backwards (left is right and right is left). I have reserved the steering in the new transmitter but how did it ever work before? Was there a way it could have been reversed in the old set up? Or do old receivers simply work backwards? The Acoms AP227 does not have servo reversing (from what I can see).

The one extra wrinkle was that the old Acoms servo leads did not fit into my new receiver so I made adapters like so.

My understanding is that if I had got the cables mixed up then the servo would either fail to work or simply fail, not reverse itself. The throttle servo, via MSC, is working as intended.

Any insight is much appreciated.

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Perhaps you rewired the transmitter and forgot about it. Was it also not possible with those transmitter to unscrew the stick housing and turn it round so that it operated in the opposite direction ? 

BITD when I need a servo to operate in the reverse direction for a dual servo clod buster setup, I took apart the servo and swapped the wires round on the motor and potentiometer. Externally looked liked an unmodified servo but operated in the opposite direction. 

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16 minutes ago, MadInventor said:

Perhaps you rewired the transmitter and forgot about it. Was it also not possible with those transmitter to unscrew the stick housing and turn it round so that it operated in the opposite direction ? 

BITD when I need a servo to operate in the reverse direction for a dual servo clod buster setup, I took apart the servo and swapped the wires round on the motor and potentiometer. Externally looked liked an unmodified servo but operated in the opposite direction. 

The Blackfoot was built for me all that time ago so it is certainly possible. But doesn't that imply that the steering servo in a stock Blackfoot is backwards? I.e. The Blackfoot would be incompatible with a transmitter without servo reversing (as a software option, hardware switch or hardware modification). I can't find that mentioned anywhere in the Tamiya manual and it would seem an odd design decision for Tamiya (given a lot of the beginner transmitters of the era didn't easily support it).

Do all servos rotate the same way on a "right" signal? Anti-clockwise when mounted spline side up as seemly required by the Blackfoot?

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Short answer is, no, servo s do not all rotate the same way! Futaba and Hitec for instance, rotate opposite ways...not sure about Acoms, although i do have some..

Before servo reverse became more or less standard, there were servos that were made either right or left hand, depending on the colour of the label on the servo...

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33 minutes ago, Palfertronic said:

Short answer is, no, servo s do not all rotate the same way! Futaba and Hitec for instance, rotate opposite ways...not sure about Acoms, although i do have some..

Before servo reverse became more or less standard, there were servos that were made either right or left hand, depending on the colour of the label on the servo...

Aha, that might explain it then.

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1 hour ago, wilysloth said:

Aha, that might explain it then.

But only if the transmitter was modded to reverse left/right. Unfortunately, it no longer works so I can't test. It still seems unlikely though, in my case, that the transmitter was internally modded (and the left/right gymbal faceplate hasn't been rotated 180° as the trim adjust still sits below the stick) so I'm still scratching my head.

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6 minutes ago, wilysloth said:

But only if the transmitter was modded to reverse left/right. Unfortunately, it no longer works so I can't test. It still seems unlikely though, in my case, that the transmitter was internally modded (and the left/right gymbal faceplate hasn't been rotated 180° as the trim adjust still sits below the stick) so I'm still scratching my head.

Some transmitters had some jumper wires on the circuit board that one could re-solder in a different position for servo reversal.
I believe I also reversed it once by swapping the 2 outer wires of the potentiometer of the steering-stick.

Some transmitters of that era also could have had the reserve switches under the battery tray lid. Or on the narrow bottom side (the one furtest away from the antenna).

Even without software-setting, many variants exist to get a servo reversed.

One could even go as far as opening the servo,  swapping the 2 outer wires of the axle feedback potentiometer, and swap the motor wires.

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