I'm glad to see I'm not the only one who sometimes quotes a post he has just made when what he actually wanted to do was edit it.... 
Flymo speed regulator
- Thread starter Jonnyspeed
- Start date
Sometimes the frustration of dealing with stubborn people gets too much.
There are certain criteria to be met for its intended use so I will achieve it I have no doubt. It's ok guys. Safety first n all.
Just because I am using the blow setting doesn't mean I'm blowing it into the hood btw.
And recycling is what we do nowadays. Most components in various appliances can be reused but instead we buy them newly packaged as something else.
Versatility is the future for us as these kind of websites become even more popular.
I am working on the possible motor cooling problem. But like I said there are no fumes near/passing the motor at any point.
Nor any spark near the exhaust.
Saving a few quid is what I'm doing and it will be done correctly.
Thanks for the link. And thankyou for your concern.
And godnight..
If you were doing it correctly you would be getting it certified by an independent body such as http://www.baseefa.com/
Is that what you are doing?
No - he thinks he's being clever by cobbling something together out of an old lawnmower to remove fumes which are explosive and possibly noxious from somewhere they should not be.
When in reality he is being very stupid.
When in reality he is being very stupid.
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OK you say safe I will believe you. So looked up flymo motor and it seems to be a standard AC/DC motor i.e. it does not really care if AC or DC it still works.
The field current to armature current relationship will alter speed and torque. As the field current is increased so does torque and as field current is decreased so speed increases.
Since field and armature are in series it is hard to alter one without the other in theory you could both reduce power in using say a 500W quartz lamp then also increase field to armature ratio by putting a 60W bulb across the armature.
The problem is getting the ratio right to reduce speed without also overheating either set of coils.
I would consider it is the wrong type of motor to play with.
I once use a dynamo to power a model train with a rheostat on the field turning to zero resistance to start and as the train gained speed slowly adding resistance to the field. Very similar to steam where we notch back the valve gear allowing steam into the cylinders for less and less of the stroke as the speed increases.
However fun as it was it took skill to balance toque and speed. And we were looking to increase speed not decrease it. To decrease speed we removed power.
From the C5 car the idea of regenerative breaking has been with us but this is far from simple and if you look at the calculations it is not for faint hearted.
So if I had to do it I would not attempt to slow the motor I would simply bleed some of the gasses round in a circle.
But this is the whole problem of re-cycle. Although one can use an old fan or even a whole building sometimes it waists more than it is worth and often new is more environmental friendly. With this in mind there was a scheme where you got government help fitting new motors rather than rewind the old one. Because the new motor was far more efficient.
Look at an extractor fan power requirements and compare with a flymo and one will see it would not take long and new fan would be cheaper.
If your really into using the flymo then swapping a bulb is easy and having a bulb holder in series with motor gives a very easy way to test how many or what size bulb is required. Clipping the wave form with a dimmer switch clearly uses less power.
The field current to armature current relationship will alter speed and torque. As the field current is increased so does torque and as field current is decreased so speed increases.
Since field and armature are in series it is hard to alter one without the other in theory you could both reduce power in using say a 500W quartz lamp then also increase field to armature ratio by putting a 60W bulb across the armature.
The problem is getting the ratio right to reduce speed without also overheating either set of coils.
I would consider it is the wrong type of motor to play with.
I once use a dynamo to power a model train with a rheostat on the field turning to zero resistance to start and as the train gained speed slowly adding resistance to the field. Very similar to steam where we notch back the valve gear allowing steam into the cylinders for less and less of the stroke as the speed increases.
However fun as it was it took skill to balance toque and speed. And we were looking to increase speed not decrease it. To decrease speed we removed power.
From the C5 car the idea of regenerative breaking has been with us but this is far from simple and if you look at the calculations it is not for faint hearted.
So if I had to do it I would not attempt to slow the motor I would simply bleed some of the gasses round in a circle.
But this is the whole problem of re-cycle. Although one can use an old fan or even a whole building sometimes it waists more than it is worth and often new is more environmental friendly. With this in mind there was a scheme where you got government help fitting new motors rather than rewind the old one. Because the new motor was far more efficient.
Look at an extractor fan power requirements and compare with a flymo and one will see it would not take long and new fan would be cheaper.
If your really into using the flymo then swapping a bulb is easy and having a bulb holder in series with motor gives a very easy way to test how many or what size bulb is required. Clipping the wave form with a dimmer switch clearly uses less power.
Recycling is nothing new! Over 40 years ago my old man used a record player motor to power a fan blade under his inglenook open fire to get it going. 'Twas too big for the newspaper sheet trick.
He also told me ( aged 8 ) that it was the reason the coal or logs sometimes "whistled". Took me 30 odd years to discover that was a porky
He also told me ( aged 8 ) that it was the reason the coal or logs sometimes "whistled". Took me 30 odd years to discover that was a porky
Do not forget that removing the field current when the motor is running can result in the motor over speeding ( at very low torque ) and in extreme cases destruction of the motor. The mechanical load of turning the fan will ( probably ) limit the speed but the armature current will increase and damage to brushes and commutator will occur.
http://www.youtube.com/watch?v=JpLA4SBm-A4 for a demonstration of the effect of reduced field current.
In the fume hood application what measures are you taking to detect and react to fan failure. ? Fan failure may require evacuation of the room ( building ) where the hood is located to ensure the safety of staff.
http://www.youtube.com/watch?v=JpLA4SBm-A4 for a demonstration of the effect of reduced field current.
In the fume hood application what measures are you taking to detect and react to fan failure. ? Fan failure may require evacuation of the room ( building ) where the hood is located to ensure the safety of staff.
At 600W, with a universal brush motor, an electric drill controller from a mains drill would reduce the speed.
However that does not stop this project from sounding like a dangerous and possibly illegal botch-up.
However that does not stop this project from sounding like a dangerous and possibly illegal botch-up.
The idea to use a lighting dimmer is not as simple as it sounds. The dimmer must be suitable for inductive loads and the one quoted earlier in this thread was certainly not. Even proper inductive load dimmers have to be used at half rating. i.e. 1000watt lighting; 500watt inductive.
The back emf from the motor will kill alighting dimmer very quickly. Use a drill controller.
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