Hi Nick
Two motors are quite common on industrial-size planer thicknessers of about 18in or above, the main motor drives the cutter block and the smaller one the power feed, normally through a gearbox. Personally, I wouldn't fancy taking this machine on, despite havoing my own FLT to move it. From my recollection RMs weigh-in at about 1250 to 1500kg so your first problem is going to be getting it delivered and into position. It's a specialist machinery remover and Hiab lorry job - no way is this going into a Transit van, even a Luton will prove very difficult because of its width. Can you get a 16 tonne flatbed up to your workshop door?
The RM is basically a late 1920s design (yes, really) which was replaced by the model FM in the mid to late 1950s (it is listed in the Wadkin 1936 catalogue I have). It utilises a large drive gearbox on the feed drive which produces feed rates of 20, 30 and 46 fpm (6, 9 and 14m/min) and that gearbox is the achilles heal of these planers. Don't consider buying one unless you can ascertain for yourself that the gearbox is not noisy, that all three gears are working ok and it isn't cracked or leaking oil. Although the boxes are generally fairly robust, I've come across a few at auction which were defective, turning the machine into scrap as the cost of having a replacement gearwheel cut was more than the machine was worth. The feed motor to this is 1HP and the main motor is generally 5HP, so if you replace this motor you'll need a very big main motor indeed! The motors are located outboard of the machine on an extra casting and so are quite accessible. They are the normal foot-mounted type. The main motor has to spin a 22in x 4in diameter solid steel cutterblock up to 4200rpm, so you'll almost certainly need to invest in a soft-start controller as I doubt that you'll find a single-phase motor with a sufficiently large capacitor start to be able to run that motor up to speed - they do run-up quite slowly. BTW, one major advantage of three-phase over single phase is the ability to wire motors in star-delta fashion - ideal for starting under load. Rather than convert a machine like this to single phase you'd be better off using a rotary phase converter (statics don't always generate full sine wave on the third phase which might goose your motors). It will probably need to be at least 10HP capacity as I don't recall RMs having a star-delta starter, meaning that they draw a large amount of current on startup (circa 20 to 25 Amps at 415 volts if I remember right).
There is another issue here as well, that of safety. A cutterblock of that size and weight will a take 10 minutes or more to run down once the motor has been switched off. The last minute of the run down is the most dangerous as the block keeps rotating but is almmlost silent. It doesn't care if you are a professional woodworker or not, it will still remove a finger or two if you accidentally place a hand on it whilst it is still rotating (don't laugh, it was/is a common cause of injury), so it needs to be fitted with a motor brake - £300 to £400 if done properly.
Lastly, have you checked the price of planer irons on this machine? They are a lot more expensive that those on a modern 12in or 16in planer/thicknesser, and you'll need at least two (or better three) pairs to keep it going.
I am not trying to put you off of buying a Wadkin - just make you aware of the problems posed by a machine of this size and weight. In essence it's the difference between buying a car and buying a heavy goods vehicle. In an earlier shop I eventually had the sister machine to the RM, an RE 20in thicknesser (same as the RM, but thicknesser only) and it was a good solid machine, but heavy. I quickly replaced that by a Robinson VZ/T 24in 4-knife machine with sectional feed which was far better (and heavier still). 4-cutters do give a better quality of surface finish but are rare on machines prior to the 1980s. Nowadays, for comparison, I "get by" with a Casadei 16 x 9in planer/thicknesser (4-cutters) which does for 95% of my needs. Unless you are doing really heavy joinery a 20 or 24in machine is probably overkill.
Scrit
PS Sorry this was a bit long
