Depends on how much of a DIY person you are.
If you want one that easliy fits without too much work I agree with PH.. Those places should know what they are selling and offer advice regarding start up and speed etc.
or if you are a hacksaw and meccano man use a motor off something else.
The gearing set up on extractors always reminds me of brace and bit hand drill, and as there are extractors for sale that can be used with a cordless drill, why not think along those lines.... Depending on what extractor you have surely it cant be too much work to remove the handle and use an electric drill of some sort.
The satandard unit is only 80W (not sure whether that is input or output, but probably input). It is not actually referred to as a motor in engineering speak. It is a 'geared unit' ie a motor and gearbox designed together as a single entity.
The reduction gears or whatever (often a large and smaller gear (expensive and larger), or crownwheel and screw ('worm drive') need to be matched for speed and torque. The torque increases as the output speed decreases for any given input speed), so JC is very correct in what he says about safety.
The normal electric motor runs at circa 1400 rpm and the speedier ones 2800, so a reduction of 10:1 is required for the normal drum extractor (280 rpm) as size is an important issue in this application.
Now, I cast around for a motor/gear for mine and picked up a whole extractor for thirty quid. The extractor was rubbish and the drive only a single direction. It was a Th*rne unit from earlier days.
That is the way I would recommend if you have time on your side.
The manual drive could be exchanged to the other extractor to recoup costs (fleabay?)
If going the 'make it', I might suggest a suitable windscreen wiper motor as a starting point? They are cheap and used to be very robust (not so much these days!) or the motor from a larger sewing machine (already has the contoller!)
Speed control for a DC motor could be a simple field current rheostat, for A/C a thyristor control (armature), or frequency changer if an induction type (squirrrel cage), motor.
I simply went the wait-and-watch route because it was simple and easy to make the change, and does not look too Heath Robinson. Even drive couplings can be a minefield these days.
I on this mission myself and have in store a couple of motors off an electric wheel chair, these may well be useful for the project i thought. Two per chair maybe designed for a 16+ stone loading, should make one ok for an extractor ? They are similar to the parvalux / old type windscreen wiper motor, not sure they would have enough womph.
Must be readily available these days.
parvelux motors are the best suppliers in the country , they can supply you with any type of motor and if you get a dc one its very simple to uise a small dc motor speed controler rather than pullies and belts , but as with every thing there is a cost to it as they are sell one of the best products at one of the best price hieghts,
i motorised a old extractor for a friend last year and we used a small electric drill from tool station that cost us £20 to buy and the morning drinking tea and paying with bits of metal to form a bracket to hold it in place, it comes with a trigger type speed control so its good enough if you can be bothered to hold the trigger or use a velcro strap to hold it in place
we were looking at replacing it for next year with a dc motor at 12 volts and getting three controlers installed into a box on the top so we could have three set speeds and timed programs to run it for us so we could be un capping whilst it spins around