Thanks for the heads up,
Fortunately I'm not responsible for this repair, basically just an interested party. I wouldn't normally get involved with the control side of lifts as I have no experience at all in this field. Like I state, I was asked to have a quick look and you could clearly see the brake not disengaging properly causing the squeal as it bound on. You could see the armature move back to open the brake shoes but there appeared to be not enough clearance. It appeared as though the return spring was too strong and the armature shaft was not moving fully in position.
Since this brake system had been removed and fully re-furbished, my first question was regarding the adjustment, and the engineer told me that it was adjusted, set and tested as per design spec. Obviously I'm in no position to argue this. The cover was off to the terminals of the solenoid so as they tried the lift and the brake attempted to dis-engage I tested across the terminals a couple of times. This is when I got the 169/170V ac readings. The I.D plate though not clear appears to state 185V dc.
So, with no experience in these matters my assumption is/was that the applied voltage was firstly ac not dc and secondly too low to operate the solenoid as it was designed to do, thus causing the brake to bind on.
The lift is now back in operation, so I assume the problem sorted, though I have no details on what was done to achieve this.
Cheers for the reply. If the lift company have re-commissioned the lift,then no worries.
I would have the same interest as yourself,in such a device and it's problems,especially if of a vintage ?
My concerns were not intended to spoil any interesting discussion on the function of period DC equipment,but to warn against a well intentioned and honest offer of assistance,allowing you to be drawn in to a possible can of worms.
In the past,i have seen and been closely involved,with such incidents,and it is not always the true villians,who the courts,or our safety friends in Sheffield,finally crucify.
I was once asked to "cast an eye",on a similar lifting device,having found myself in the middle of a falling out,between two,rival lift maintenance companies,and a building maintenance outfit.
The many visits and parts fitted,with no lasting fix,resulted in one of the engineers,and myself,inspecting the winding gear,where an old trick with yellow marker,revealed a siezed sheave,which the rope had cut through,almost to the bearing. This was the cause of noise,stretch and mis-timing.
This was an obvious long-standing issue,and had been missed by the engineer or his team,so put his company on the spot,but my involvement with LOLER and PUWER,meant i had a duty of care,regardless of any professional employ. He bit the bullet,and submitted an amended report,which allowed mine to remain in me diary?
At no point,during any of the above,did i receive payment,or even a "thank you"..... the lad asked me where i bought me yellow marker from,but not even a cup of tea... ?
