Sunday 8 May 2022

Bijur lube pump

The machine has the traditional Bijur-Delimon automatic lube pump for lubricating the slide ways. These are designed to deliver a fixed (but adjustable) squirt of way oil periodically, at a fixed interval which is determined by the gearing within the mechanism.



Mine's a C-2896, which is:
  • 120VAC
  • 1 pint(!) reservoir
  • 7.5 minute cycle time (at 50Hz) 
  • 0.2 - 1.0 ml per stroke, set by an adjustable collar. 

Usually these things are intended to be continuously powered while the machine is operating. Depending on the stroke, that would amount to between 8ml per hour and 1.6ml per hour. Sounds reasonable to me, so no need for a separate control to space out the events. However, I will enable it from the power circuit that runs the VFDs and servo drivers, so it's not simply pumping away when the PC is powered up with no actual movement happening.

120VAC power?
I will require a 120V transformer somewhere to power both this and the hydraulic solenoids used for the turret and tailstock. The total power draw will be miniscule, so it needn't take up much space.

Let's sanity check what the solenoids draw. I can't see it specified anywhere. The hydraulic solenoids are Sperry Vickers 414521 model and although it comes up in searches, there's no mention of power draw.

DC resistance measures as 27R, so clearly the inductance is the significant factor that determines the current draw. Rather than measure the current, let's estimate what it will be.

Out with the inductance meter. It rarely gets used but this is one occasion where it is actually helpful. 


130mH is an impedance of about 40R. In conjunction with 27R resistance, that would suggest a total impedance of around 50R. Clearly not - I guess the inductance increases significantly when the solenoid closes.

With a plug-in power meter and one of those 240-120V stepdown transformers, I'm seeing a static current in the transformer of 240mA (presumably that's all inductive) and a loaded current of 620mA. I can't be arsed to calculate the circuit values but the meter also reports 60W, which I assume is the real component that is responsible for the heating effect. That's a lot more than I'd expected, so I may need a few hundred VA worth of transformer in the end. 

A job for later, perhaps....

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