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2 speed wipers for MM ~ Part 1

 
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Bally
At rest


Joined: 19 May 2011
Posts: 219
Location: ACT

PostPosted: Mon Sep 15, 2014 2:12 pm    Post subject: 2 speed wipers for MM ~ Part 1 Reply with quote

G'day all
Anyone with a side valve MM wishing to fit two speed wipers would probably be aware of the difficulty of fitting a later two speed motor, and having to change the rack and wheelboxes which is major surgery. I have been able to successfully modify the wiper motor on my 1952 MM to give two speed operation. The motor as standard is shunt connected ie. the field and armature are connected in parallel. The mod involves disconnecting the field from the negative lead and joining a wire to the disconnected end and bringing it out to a separate terminal to enable the field to be externally switched either directly to the negative terminal to enable the motor to function as normal at 36 cycles per minute, or to switch a resistor in series with the field so that it operates at a high speed of 59 CPM no load or 58 CPM on a wet screen. These two speeds satisfy the requirements of VSB 14. The attached pics show the nameplate, external terminals before commencing and a circuit of the changes made. The switch is a double pole double throw with centre position being off. On low the field and armature are connected in parallel as standard, and on high a 25 ohm resistor of at least 25 watt rating is switched in series with the field to enable the increase of the motor speed. I will give a follow up posting of more details of the mod.





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