UK electronics forum

The Shop > Electronics & IC Programing

<< < (3/4) > >>

John Swift:
Andrew

"Oh Gawd now I feel really old "

that's what I thought a few weeks ago when I realised I can apply for a bus pass in a couple of months :(

John

vtsteam:
I've made a spot welder from a big transformer before. The hard part was pulling out all the old wire from the secondary. It was varnished in there, or something, and tight as heck. But eventually I got it chopped out.

Later I bought Harbor Freight spot welder for $125, on sale, and have used that a lot.

geoff_p:
I don't really want to sidetrack this thread but ...
Back in the early '70s, I was a draughtsman at Martin Electric, Theale, where we made spot welders. Our 'small' ones used a 25kVA transformer, which delivered a mere 500,000 Amps - the secondary-cables were about 1.5 inches diameter. All parts of the secondary circuit i.e. transformer, cables and welding-head, were water cooled, they reckoned the current 'leaked' through the water was negligible compared to what went through the weld.

The transformers had 3-phase primary windings and a secondary comprising two turns. Each of those turns was cast copper, up to an inch by four cross section, with a coolant-pipe cast-in, in the form of a U-shape and connected in series. The secondary voltage was probably only a Volt or two, it was Amps we wanted!

The controllers comprised a timer switching thyratrons - the valve-type precursor to the thyristor (thyratron transistor ) - on all three phases of the mains power.

Since then, my interest in electronics has used FAR smaller currents but has gradually dwindled. I built my first CNC machine to overcome my failing eyesight so as to drill the holes in my PCBs.

And that in turn has led )eventually) to my current build of a CNC milling-machine.

Which is calling me just now to do some more work.

Geoff
Thailand

DavidA:
...My first project was a crystal set ..

I still have a genuine cat's whisker.

1959.... The year I left school.

Dave.

BaronJ:
Hi Guys,

Talk about dating ourselves :bugeye:

I got my first "cats whisker" from the radio shop across the street. That would be around 1955, I was ten. The chap who ran the shop was an ex RAF wireless technician. My dad bought a 10 inch Bush TV from him in 1952/3 and the whole street was in our house watching the coronation of the queen. I used to spend hours in his shop. Mother always said she knew where to find me when a meal was ready.

:med: :med: :med:

Navigation

 Message Index

Go to full version