Info wanted on making use of ex aircraft ‘Trim Servo’

[Ian PParticipant @ianp]

One of the items that I have hoarded for many years is a Smiths servo unit that contains a motor, electric brake, electric clutch all geared together in such a way that the output gear is normally free to rotate.

 

It occurs to me that I could repurpose (I hate the word!) this unit as a milling machine table feed, the best feature would be that it not effect manual operation.

 

Because this servo is fairly old (WW2 to1950s at a guess) I dont want to dismantle and modify this unit if its the sort of thing that is keeping some historic aircraft grounded! If anyone has any experience of aircraft restoration and can tell me anything about this item I would appreciate any comments.

 

It is a Smiths Type A Trim Servomotor, 186-1 EAP in a black anodised aluminium casing about 120mm diameter and 120mm Long.

 

Ian

 

 

 

 

or would be

 

 

[Ian PParticipant @ianp]

[Chris TriceParticipant @christrice43267]

For what it’s worth, I believe most aircraft of that period used a 24 volt electrical system but you probably knew that already from whatever spec labels there are on the unit.

[Ian PParticipant @ianp]

Posted by Chris Trice on 27/08/2011 01:43:29:

For what it’s worth, I believe most aircraft of that period used a 24 volt electrical system but you probably knew that already from whatever spec labels there are on the unit.

 

Whilst there is no voltage noted on the identification plate, internally the motor is marked 115V and runs to 20,000RPM, the clutch has no ident but the electrical brake is marked ’12 Volts maximum’ so thats unusual. Most of the DC aircraft stuff I have come across seems to be made to run on 28 Volts.

 

Ian

[Anonymous]

The 28V DC system on aircraft is still based on 24V. It is just that the alternator voltage is used. That’s the same as your 12V car system. When it is running it will not be at 12V, but is more likely to be nearer 14V.

 

Larger aircraft also have an AC electrical distribution system. Normally 115V, 400Hz, three phase.

 

Regards,

 

Andrew

[Author]

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