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  1. H

    Torque difference between 1PH and 3PH motor

    Not quite, really, the Americans get short measure on pints, theirs are only 16 fluid ounces versus the Rest Of The World getting twenty (and quarts and gallons follow suit) - elsewhere when folks my age were at primary school we were taught "A Pint of cold water weighs a Pound and a Quarter".
  2. H

    VFD for a Clausing Colchester 15?

    A VFD is the easiest method unless you want to spend more on a Phase-Perfect or ready-built RPC, building your own RPC is quite involved - I built one for the other machnery (Mill, TIG, bandsaw, pillar drill etc and anything I should drag home from an auction or work on for someone), but have...
  3. H

    British/European screwcutting benchtop lathes?

    Holbrook did some nice small lathes, very, very nice, toolroom quality along the lines of the Rivett 608 benchtops - pretty rare but worth looking for, I have one of their larger toolroom lathes, the C13 - for 1955 it's very modern apart from its beautiful curvy styling :)
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    VFD Loud bang.

    Book Learnin' can be a dangerous thing (especially when it's ony the course syllabus) - I've worked on a lot af AC-DC convertors and large amplifiers (e.g. servo amplifiers moving 60-foot dishes horizon to horizon in a few seconds), capacitor ESR is a big issue when you suddenly have to dump a...
  5. H

    460 motor to 230

    It's not that much work, maybe an hour if you're unfamiliar with the guts of a motor - it's often done by home shop machinists here in the UK as our domestic mains is 240 vs industrial 415 3-phase and 240 to 415v VFDs are still more expensive than straight 240-240. The star point is always...
  6. H

    Anyone try running a step down transformer in reverse to power a machine?

    Here in the UK domestic power's 240 single-phase, industrial's 415 3-phase, so I put the transformer (take a 9KVA oil-cooled welder, strip off the welding winding, 3D print a bobbin and wind on root3 times the primary turns, pot with epoxy) BEFORE the rotary converter, works pretty well (have a...
  7. H

    220v single phase to 220v three phase

    Always handy, it lets you plug-and-play when you want more machinery (and you surely will!) I home-brewed mine (I think there's a write-up and some wiring schmatics in the RPC thread), and can run lathe, mill, bandsaw, TIG welder, humunguous pillar drill (a halfway-radial, Meddings F14) and...
  8. H

    Phase Converter Troubleshooting

    Not quite, it uses the incoming power line for 2 of the phases, digital bit steers the generated phase (or so i'm led to believe), which is generated like one leg of a VFD but not frequency changed, just phase-shifted to keep the 3 phases balanced. I think.
  9. H

    rewiring 380 2speed motor for 220v

    Can you post a pic of the diagram inside the motor cover? There are two ways of getting two speeds, completely separate windings for each speed (costly, larger motor) or a "Dahlander" winding which swaps connections - picture a delta winding triangle, with centre taps in each phase - by moving...
  10. H

    240 Single Phase to 440 3 Phase

    Keep the three ends already there, and when you've found the star point you can buzz out the windings - as long as power goes to the existing terminated lead wires (lets call them "start"), the other three lead wires you've added from the star point, (lets call them "ends") can come out to three...
  11. H

    VFD's "burn up" a motor?

    No argument with that, load inductors aren't necessarily that expensive though - I wound a set on three matching old 24v control transformer cores, I'm like that - once you determine what inductance you need (and can measure it! Credit-card sized LCR meters are stupidly cheap now!) from the...
  12. H

    Running 575v 3-phase from 240v 1-phase?

    Helps it they're submerged in transformer dielectric oil, too, and exceed UL and CE creepage distances, were Hi-Pot tested beyond EU approvals spec voltage (2kv) - and yes, well enough versed in transformer construction from 50Hz up to a couple of hundred MHz, a kilowatt or more, thanks. Afraid...
  13. H

    Running 575v 3-phase from 240v 1-phase?

    True, but makes one wonder why there's so much info' on homebrewing RPCs if everyone just goes out and buys them - this sub-forum has more than a handful of posts on that subject? Fine if you can justify the cost of a COTS solution, but a significant fraction of the subforum is precisely about...
  14. H

    Running 575v 3-phase from 240v 1-phase?

    Probably is, but my Holbrook has a 415-only 3-speed motor (although it's now run from a hacked-at-home VFD that makes 415 from 240 between 10 and 85 Hz, to give lower and higher spindle speeds), and the standard in Europe (and most of the world) is 3-phase 50 Hz around 400v (Europe, e.g., was...
  15. H

    Running 575v 3-phase from 240v 1-phase?

    I got around a 415-only motor on 240 by putting a step-up before the RPC - the transformer is an old oil-cooled welder with the low voltage winding stripped off and a new secondary wound on a 3D-printed spool to fit the laminations - fairly easy to work out the turns ratio,wind 10 turns of...
  16. H

    An unpleasant surprise in my Pratt & Whitney 12C

    I had to adapt taper rollers for my Holbrook Model C, the QCGB originally had 1985/1986/1922B - the B is flanged and long-obsolete! I was offered the set as special-order for £500 per bearing, minimum order quantity 500... so I put a circlip groove in the outer diameter of standard 1922 outers...
  17. H

    Inductive linear scale

    I don't think you need to replace op-amps, if the fault was in those it would affect all the tracks' outputs and it's likely all the digits in the scale would be crazy! If you do, the NE5532 is a good low-noise small-signal dual op-amp if you need to substitute. (assuming 8-pin package it's...
  18. H

    Inductive linear scale

    Hi Zilot, As the rest of the bits fed to the display are counting correctly (I assume - looks that way in the video) you can assume (I know, ass of u and me...) that the analogue amplifier side is working correctly. Looking at the counts and the schematic, only one track of the sensor head is...
  19. H

    ID this old attachment

    You'll offend a lot of collectors of Might_Be_Usefuls if you scrap it - see if anyone wants it a-is first! Dave H,.(the other one)
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