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| Fitting a Variable Speed Motor to a Dore Westbury Milling Machine |
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| Ned Ludd:
Hi Andy, With regard to your round column and loss of registration, have you thought about using a laser level mounted on your mill head, pointing to a vertical line on the far wall of your shop. If you have a Pound shop near you, they can be bought for, surprise, surprise, a Pound, less batteries of course. You don't get much for a Pound these days do you? :( Ned Ludd |
| andyf:
Thanks, Ned. I got a laser from the local pound shop with exactly that in mind, but on thinking more about it I went no further. There were three problems: 1. The best wall for the job is obscured by tools hanging from racks and hooks. 2. The mill sits on a stand which can shift in position slightly on the floor if I bump into it during the course of a job, 3. A round column, though it can be a nuisance, does have one benefit. The ability to swing the spindle in an arc from side to side sometimes enables me to get the spindle over the extreme ends of the table and beyond, in effect extending the X axis travel of the table. This can come in useful, but to use a laser it would mean drawing an exactly vertical line down the wall every time I changed the position of the spindle along its arc (perhaps, rather than "exactly vertical", that should read "parallel to the column", which would make the line more difficult to draw). For Sale: Laser, as new. £0.99, batteries extra. :lol: Andy |
| DMIOM:
Andy, have been in the same dilemna with my manual Warco round-column mill. I too though at first I could have a static vertical line and always keep the laser on it - but found that (since the stand isn't bolted to the deck) it does walk around a bit. What I came to realise is that the laser/line alignment doesn't need to be absolute & permanent - it just needs to remain consistent whilst you're elevating or lowering the head. Mine stays reasonably consistent, but before I start moving the head, when I switch the laser diode on, I either say "OK, its on the line" or "its 2/3 right of the line, 1/3 left" and I know I just need to get it the same when I've finished moving the head. If its a long way off, I either swing the machine or the laser. I have come to learn that once I tighten the column clamps, it will move by about 1/4 a spot width! The further you can get the line away from the laser, the longer the light-lever and the more sensitive the alignment; I use a commercial laser diode and a plumb-line at about 3m and I find it does a good enough job. Dave |
| Darren:
I like the plumb line idea, KISS .... always the best :clap: |
| andyf:
Final update: I made a plastic holder with a transparent front into which I could slip different dials to suit various pulley/gearbox combinations, and got as far as calibrating a dial. Then :bang: :bang: I realised that it would after all be possible to fix the actuating magnet for my bike speedo/tacho, in the recess on the underside of the gearbox casing, I salvaged the little magnet which triggered the running machine’s speed sensor from one of its pulleys, together with the counterweight dummy magnet, made little housings for them from scrap white plastic, and attached them under the gearbox. The tacho’s sensor head (the part meant to go on the front forks of a bike) was fixed to the rear of the spindle head on a bit of bent metal, held by two existing bolts. The display works fine when the gearbox isn’t being used and is rotating as a single unit. When the gearbox is in action, its casing and the magnet fixed to it are immobilised, so the tacho doesn’t work. I doubt if there will ever be much need to find out the exact speed of the spindle in low gear, but just in case I have retained my dial holder with a simple dial, showing arbitrary markings. With the gearbox out of action, the tacho can be used to set the speed at 8.8 times what I want and the dial reading noted. Then, the gearbox can be engaged and the dial set to the same reading to get low speed more or less right. Here’s the tacho in action. It can be hard to read if light falls on it at the wrong angle, so it is on a bracket allowing it to be swivelled for a better view. 105.2 kph = 1052 rpm (and it thinks I've cycled 5.65 km this morning!). Sorry these photos are so big. The tacho looks a bit out of place, but it's convenient having it just above the control knob. If I want 120 rpm using low gear via the 8.8 to 1 gearbox, I would set the machine to run at 1052 rpm or thereabouts, stop the motor, set up the gearbox,and wind the motor up to 8 on the dial again. The tacho would read zero, but 1052/8.8 = 119.4, which is near enough to 120. Footnote: To turn it into a tacho, a “bicycle computer speedometer” should be programmed as if on a pushbike with wheels of 1667mm circumference, and to read in kilometres per hour. The reading x 10 then represents rpm. Mine (an “Echowell Star” at £9 from Halfords here in the UK) reads to one decimal place up to a maximum of 199.9 kph/1199rpm. It only updates about once a second, so a moment’s pause is needed after altering speed, to let the reading settle down. Andy |
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