My Bench..... taking ages!!!

[jsmith]

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[jsmith]

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[jsmith]

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[jsmith]

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[jsmith]

Here's a few jpg's of my bench design... I've been accumulating bits (mainly via ebay) and hope to start building soon.

All the piping is standard toilet fitting stuff, but the orifice plates and housing will require a few lathe/mill hours!!!

Let me know what you think about the idea.

The main thing I don't like is the valves for directing and regulating the flow.
In my mind I think I would like to be able to regulate vacuum with a variable resistor (speeding up and slowing down the motors as required). I'm an electronics dunce though, so I would like some opinions as to whether this is possible.

[84-1074663779]

I assume you are using normal vacuum motors, these are a brush type universal ac/dc motor and the speed may be controlled simply by adjusting the ac supply voltage.

The easiest and most trouble free way to do it is with a variable voltage transformer or "variac". Have a look on e-bay for some pictures. These variacs are always readily available secondhand. They are rated for output current, so you can get a two amp variac, or a ten amp variac and so on.

In theory you could use a suitably high powered light dimmer but these do not like motor loads and usually self destruct. High powered electronic motor speed control units are available but are not a cheap solution. A nice large variac will last a lifetime and is not going to go "bang" or burst into flames on you.

One caution though, brush motors will work fine at reduced voltages, but induction motors cannot be varied in speed by just dropping the voltage. To do this you need to vary the mains FREQUENCY as well as the voltage. So if using a variac make sure your motor is the brush type.

[jsmith]

I'm using these YDK motors:



See pic attached.

[jsmith]

I'm in the UK (240v 50hz).

If they are wired seperately, with a dimmer each, do you think the dimmer would survive?

How many amps can I safely draw from a single wall socket (standard fuse is 13a - would this be enough for 2 or 3 of these motors running flat out?)?

The variac's on ebay seem quite expensive and I guess I need quite a powerful variac in order to provide enough current for all of my motors.

The vacuum cleaner that the motor comes from is advertised as 1400W, can I assume then that each motor draws 6 amps???

P = V x I
I = P / V
I = 1400 / 240
I = 6a

If I use 3 motors, should I assume they will pull 18 amps (3 x 6amps). Therefore is this safe from a single wall socket? Does the required variac need at least 18amp rating, is there any chance of 3 dimmer switches surviving?

The best dimmer switch I have seen advertised is rated at 500W - I guess this will be struggling at 1400W, I don't want to start a fire....

Sorry for all the questions, but electronics aren't my strong point and a mistake could be dangerous!

Thanks.

[jsmith]

What do you reckon to this dimmer found on Maplin website?
I have also found some standard 1000w lighting dimmers, maybe they would be powerful enough (1 for each motor).

With this dimmer it is possible to control filament lamps, heating devices (e.g. soldering irons), collector or split-pole motors. The maximum current input of these devices may not pass over 1200W. Fluorescent lamps, quartz lamps, energy saving lamps and motors with a starting capacitor (e.g. washing-machine motors) should never be connected with this dimmer module. maximal capacity:1200W @ 230Vac, continuous power of 600W.

[Mouse]

I have been using a router speed controller, from HarborFreight ($24.00 reg. on sale now for $12.??) on my shop vacs. It is rated for 15 amps and works well. Doesn't drift, surge and hysterises are good.

Forget light dimmers. They suffer all of the symtoms I mentioned above.

John

[Greg]

You probably only need to vary the speed on one motor for fine adjustment. If you have a separate switch on each you can flick on enough motors to provide the depression you need. This would make for a cheaper speed controller as it needs a much lower amp rating.
I have run separate wiring from the fuse box through 3 240v 20A breakers to 3 lots of 4 1kW motors (only using 8 to start with) but that is in a workshop with pretty heavy duty wiring to the fuse box, I'm not sure what normal domestic wiring will take?

[jsmith]

I like the sound of that....

But will it be ok for British 240V?? I found the harborfreight website and I think I found the controller that you mean:



It says that it is ok for 250VDC??

The price apparently is $19.99.....

Is this the one?

[jsmith]

The Superflow SF110 runs at less than 10amps (240VAC)...

How do they manage this???

[Mouse]

Yeah that's the one. It must be a local sale. I forgot about the 240V. Looks like it won't work.

As for the SF110 @ 10 amps, it's the 240 volts that brings down the amps. It would draw a lot more amperage at 110 volts. Power = current X voltage

John

[jsmith]

The Superflow pulls 15a max at 110v - I guess this suggests that it only uses 2 vacuum motors.

What did you reckon to the power controller that I posted on page 1 of this thread?