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Notice the patent of the day today? Lets see now. Inclined drum and recirculation pump. Zan IZ anyone?
Why not a new’un? Try B&Q or Homebase for,one of their compressor & nailgun kits. £70-ish last time I looked, and even have a carrying handle.
Problem with suspended floor is that they are a variable. Consider:
I occasionally work with laboratory centrifuges. heavy rotor (maybe a half the machine’s mass), but samples are loaded very precisely, so the unit rotates with perfect balance. The a/v mounting feet are just that- to damp motor noise from travelling through the bench.
Now your w/m is a totally different ballgame. A light stainless steel drum (rotor) filled with your washing packed in god-only-knows which way. A massive imbalance. We offset that by mass-loading the outer tub with the motor, lumps of iron or concrete, whatever. But that aint enough to fully control the movement of the tub on it’s suspension so… the movement is damped by shocks. Just like a car.
Problem here is that “for every action, there’s an equal and opposite reaction”. What this really means is the tub will try to pull the machine off the floor.OK. We know this, so does the manufacturer. He has to design the suspension spring/ damper combo so that acceleration/ decelleration of the tub is controlled without transmitting too much to the chassis. The levelling feet then control this movement of the chassis.
But when you set the machine on a suspended floor, you are really setting the machine on another spring. Springs have a resonant frquency. If it just so happens that the floor and the w/m have a similar resonance, then (basically) the floor will try to pull away from under the machine. This antiphase can result in twice the peak displacement, and so could very well be enough to make the whole machine levitate off it’s a/v feet and gently glide accross the room, making a terrible racket.
So. The floor is a variable. Better than that, it’s an unknown. The manufacturer can neither design a w/m for your specific floor nor really advise you on your floor ’cause he can’t see it or measure it’s properties. He can recommend that you increase the strength and mass of the floor in that area. But it’s only advise. He could perhaps add a specification in the sales blurb with a required constant for floor strength or resonant frequency. Would it help? not really.But a mod kit for the machine to try and contol the tub and chassis relative to the unknown spring it’s sitting on is a pretty good response in the circumstances, no?
DavidAnyone got an “expired” disc they’d like to donate to science?
It’s amazing the variance there can be in the supply of technical info- look at the motor trade, many manufacturers won’t release *anything* yet Suzuki for example will sell you (over the counter, retail) a cd containing factory service info inc. diagnostics and wiring diagrams for not much more than the price of a haynes book…
sounds a bit like a reed switch OK. Try holding a magnet beside it and checking it for continuity again 😉
Doesn’t have to be anything too special. CPC do a good range or you could look at some of the specialist test& measurement companies like ATP (atp-instrumentation.co.uk) or Testo (testo.co.uk)
I can recommend item IN02030 from CPC- it’s an autoranging DMM with a type K input, RS232 out, and data logging software. Even with a cal cert it’s less than £50.
if you need differential inputs you could look at (say) IN00715.Just need to select your choice of thermocouple.
Plus, for some applications (as long as the item isn’t too shiny) the non-contact laser-sighted IR devices are useful. Instant response! see IN02294 and similar.Gotcha. You’re quite correct. I was simplifying it too much for my own good…
Are there may w/m motors that have independant control of the field coils? Seems that with a bit more juice to the fields starting torque would be improved, no?
David
3-phase stuff is becoming more and more prevelant and therefore simpler and cheaper. The motors tend to be cheaper than their capacitor-start equivalent, certainly more reliable, and on top of that today’s control gear is much simplified over the stuff of yore.
Indeed, Andy. You’re talking in specifics now, rather than general terms, and whether we talk of current or voltage control in a “universal” motor (brush and commutator) we are clipping (removing) part of the AC wave with the resultant power control.
It’s interesting that you should mention phase chopping to control an induction motor although in this case we most definitely are talking about current control as in a synchronous motor reducing the supply voltage increases the running current (a common failure mode in power washers, air compressors is when the customer runs the item off an extension lead and the run current increases- this ends up burning the motor out due to the increased dissipation…). I don’t think I’ve ever seen this kind of control in any of the kit I look after (lab centrifuges etc)
On the LG machines, I know nothing of their particular control method but normally these disc motors are just flat multiphase induction motors. Sometimes, however they’ll use one or more hall-effect sensors to establish rotor position an assist the timing of the drive pulses. The little fans used for cooling PCs are a good example of ths, and are more like a stepper motor…
Aye, induction drives are clever stuff. I was changing the bearings in a centrifuge motor today. 3-phase motor with direct drive (no reduction) to the rotor, and able to accelerate about 5kg of rotor up to a maximum of 14k rpm. Said motor is less than half the size of the average w/m motor…Are you thinking of an induction motor or a brush motor? Brush motors are variable speed based on voltage whereas induction motors are locked to supply frequency. In the case of the induction motor, consider the number of poles as a multiplier.
So in a brush motor run on AC you can “chop” the top and bottom off the sinewave to alter it’s effective voltage and control the speed. Bung the input from the tacho into a feedback circuit and bob’s your proverbial.
Induction motors are a different kettle of herrings as you have to alter the frequency to alter the speed (unless you’re looking at one of the old SOLE multiwound multispeed motors…). So this is why the latest big WMAs have an inverter with it’s associated high voltages. Now you’re rectifying mains AC, then using the resultant 400v or so DC to power the motor- it’s switched to each of the three phases of the motor in rotation, and the speed of the motor is locked to the speed of this switching.
make sense?
David
Guys, if you’re doing any amount of smd work, treat yourself to one of the cheap gas irons- I use an Iroda 70- and get a hot air tip for it. a mere waft of the tip over the component and you can pluck it off with tweezers. I’ve used this technique with gullwing ICs too, but a bt of patience is needed.
Oh, and plenty of engineers will tell you it’s impossible to work with smds without a hot air rework setup, but that’s £1000 I don’t have, LOL.
david
