Over the years, I've remarked on my preference for very quiet workshop vacuums a few times.
In the same vein, I'd like to share todays workshop project. Adding a variable speed control to an oldish commercial vacuum that I bought second hand through ebay a few years ago.
First the vac : this is Nilfisk GD930 low noise commercial vac.
1200W with good suction and well built.
These machines are like a donut with the motor in the centre. They must be used with a bag but the bags are quite large and surrounds the motor helping to damp the motor noise. Noise is low 60's dB which is VERY quiet.
I have a big nilfisk attix shop vac out in the workshop but this isn't something I want to drag indoors to clean up after a small job so I find the 930 useful and because it's handy I quite often hook it up to powertools. The one snag with this is that the (nice quality) turbine in the vac relies on the exhaust air to cool the motor. Not a problem when used as a vacuum cleaner but if you connect a tool like a sander that chokes the airflow and gets used for quite long sessions, this type of vacuum is prone to overheating.
The answer is easy. Wire a simple, cheap, variable speed module into the vac, after the piwer switch and before the motor, then you can dial down the airflow when needed.
A fact that I learnt from the radio and stuck in my memory is that the amount of power generated by wind turbines increases with the cube of the airspeed : double the wind speed and they make eight times as much power. Flip this idea on it's head and I expect that if you halve the air speed in a vacuum cleaner, you will probably reduce the power needed by more than just half, and the waste heat likewise. So slowing down the vac with a variable speed control should reduce the risk of overheating when I hook up a random orbit sander.
It was a bit of a gamble but I happen to have a small variable speed module that works like a lighting dimmer and the back of the 930 has a power switch in one corner and a strange power takeoff socket in the other to power a motorised brush head. I decided to scrap the socket and try to squeeze the module into that corner of the body. After trimming away some parts of the plastic moulding, the controller did squeeze in and sits there like a blue volume control that has lost it's knob.
Here's the module. Something from the parts bin and rated 10A, about double what is needed.
Here's the corner that it squeezed into once some of the plastic just left of the cable entry was cut back.
Here are some shots of the domel turbine that sits in the middle of the vac, just held in place by a couple of springs that are compressed when the base is screwed on.
It's all wide open so that the air filtered through the bag can cool the motor and vent out around the bottom of the vac.
And one novelty, a little pcb with some simple high value resistors to allow static to dissipate. This is interesting because this is a double insulated machine. It has no earth connection even though the dust bin is pressed steel.
The variable speed module I used does have an earth terminal and I imagine this is needed for it to work reliably. I swapped out the original mains cable for one with an earth, but I only connected that earth to the variable speed module so that it could switch reliably. I left the original double insulated design and static dissipation resistors unchanged.
How does it work ?
Great
What does it owe me ?
About £40 total including the vac. Bargain !
I'm sure there are plenty of other secondhand commercial vacuums that could easily be pimped the same way and variable speed modules are cheap on ebay...
In the same vein, I'd like to share todays workshop project. Adding a variable speed control to an oldish commercial vacuum that I bought second hand through ebay a few years ago.
First the vac : this is Nilfisk GD930 low noise commercial vac.
1200W with good suction and well built.
These machines are like a donut with the motor in the centre. They must be used with a bag but the bags are quite large and surrounds the motor helping to damp the motor noise. Noise is low 60's dB which is VERY quiet.
I have a big nilfisk attix shop vac out in the workshop but this isn't something I want to drag indoors to clean up after a small job so I find the 930 useful and because it's handy I quite often hook it up to powertools. The one snag with this is that the (nice quality) turbine in the vac relies on the exhaust air to cool the motor. Not a problem when used as a vacuum cleaner but if you connect a tool like a sander that chokes the airflow and gets used for quite long sessions, this type of vacuum is prone to overheating.
The answer is easy. Wire a simple, cheap, variable speed module into the vac, after the piwer switch and before the motor, then you can dial down the airflow when needed.
A fact that I learnt from the radio and stuck in my memory is that the amount of power generated by wind turbines increases with the cube of the airspeed : double the wind speed and they make eight times as much power. Flip this idea on it's head and I expect that if you halve the air speed in a vacuum cleaner, you will probably reduce the power needed by more than just half, and the waste heat likewise. So slowing down the vac with a variable speed control should reduce the risk of overheating when I hook up a random orbit sander.
It was a bit of a gamble but I happen to have a small variable speed module that works like a lighting dimmer and the back of the 930 has a power switch in one corner and a strange power takeoff socket in the other to power a motorised brush head. I decided to scrap the socket and try to squeeze the module into that corner of the body. After trimming away some parts of the plastic moulding, the controller did squeeze in and sits there like a blue volume control that has lost it's knob.
Here's the module. Something from the parts bin and rated 10A, about double what is needed.
Here's the corner that it squeezed into once some of the plastic just left of the cable entry was cut back.
Here are some shots of the domel turbine that sits in the middle of the vac, just held in place by a couple of springs that are compressed when the base is screwed on.
It's all wide open so that the air filtered through the bag can cool the motor and vent out around the bottom of the vac.
And one novelty, a little pcb with some simple high value resistors to allow static to dissipate. This is interesting because this is a double insulated machine. It has no earth connection even though the dust bin is pressed steel.
The variable speed module I used does have an earth terminal and I imagine this is needed for it to work reliably. I swapped out the original mains cable for one with an earth, but I only connected that earth to the variable speed module so that it could switch reliably. I left the original double insulated design and static dissipation resistors unchanged.
How does it work ?
Great
What does it owe me ?
About £40 total including the vac. Bargain !
I'm sure there are plenty of other secondhand commercial vacuums that could easily be pimped the same way and variable speed modules are cheap on ebay...
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