Faster Motor (Bosch Exxcel1200)

[Stevethesax]

Hi Folks,

My old Bosch 1400 Exxcel threw a wobbly over the weekend when it decanted its load of water on the floor (probably related to the severe juddering when it spins...currently under investigation) - so I nipped down to my local white goods store (AKA the local tip) and picked up a Bosch 1200 Exxcel Express for £20.

Bit smelly, but a few service washes etc. should cure that - but otherwise functional. However, the motor chirped and crackled a fair bit so I decided to swap it out with a spare from a previous 1400 Bosch that I'd 're-brushed'.

I've often wondered what the difference between the various spin-speed models was, and when I pulled the 1200 motor out and compared it to the 1400 I noticed that the pulley on the 1400 was a bit larger than on the 1200...so 'they do it with gearing' in this case.

That said, I also noticed that the drums are specifically marked '1400' and '1200'.

Anyway, all seems to be well - but this throws up a couple of queries:

If the drums are marked with the maximum spin speed, could upgrading the motor lead to mechanical failure?

Perhaps they're weighted differently?

The other issue is that the normal wash speeds now seem a tad brisker. This would suggest that there's no electronic speed control and that it's 'all done with gears' - which is fine, but does this mean my pants are going to get the pummelling of their life?

I'd appreciate any sage advice. If it's deemed to be a no-goer then it's a simple matter for me to service the 1200 motor and pop it back it....but otherwise I'd be happy to leave a working machine well alone.

Cheers,

Steve

[Whitegoodshelp (Andy)]

The way they get the extra speeds is often very simple and costs them very little, but they charge a premium price for them. Very often it's done electronically but often also have a different sized drum pulley to help. It's hard to know if the motor is genuinely going to run at the full speed because it may need a different control module too but if the drum is turning obviously faster it may not be good for delicate items requiring reduced agitation.

[Stevethesax]

Many thanks for that.

I did some measuring of the motor/drum pulleys and scribbled a few numbers down on a piece of paper....but halfway through I forgot exactly what I was trying to work out (I managed to prove that a 1400 spin speed machine spins at....1400 rpm).

And then it occured to me that it would be far easier just to turn the blooming machines on and count the revolutions of the drums during a wash.

So, with the aid of a torch and a stopwatch I found out that I'd been fooled...and that the 1400 Exxcel washes (30 degree cycle) at 54 rpm while the 1200 does so at 46 rpm.

There's some slight difference in the diameter of the drums (15 1/2" on the 1400, 15" on the 1200), but by this time I'd figured that the difference wasn't worth worrying about and that my pants won't get mullered in the wash.

What the final spin speed of the 1200 is now is anybody's guess - but having read the article about spin speeds I'm none too bothered.

Cheers,

Steve

[edhorwood]

Washing machine motors are controlled by a board. They have to be. If you take any washing machine motor and put pure uncontrolled voltage into it, it will spin like a jet turbine. I've seen this with the sensor on the motor shaft removed. This sensor reports back to the control board the revs of the shaft, so the power can be adjusted accordingly. It doesn't just give the same set voltage everytime the machine spins or washes, because it simply wouldn't work. A full drum is not going to spin at the same speed as an empty drum unless power can be increased. The motor will be turning at near enough the same speed as the old one but obviously the pulley wheel sizes will influence the overal drum rotation speed because they are essentially gears. So, if you put a motor rated at 2000 rpm spin (just as an a silly example) into your machine, the spin speed will be reduced to 1200 by the board because the revs are monitored and controlled from there. Taking it the pulley sizes are the same of course.

[Stevethesax]

Sure thing, there'd have to be some sort of controller otherwise all the speed changes for and during the various wash programs would have to be done via gears...which would make the machine rather complicated...and heavy (though possibly more fun). But the slightly larger pulley on the 1400's motor seems to suggest that that speed control module (in itself) is the same across a given range of machines, and that the relatively minor change in top spin speed is done via gearing. It would make sense from a cost perspective - and the speed differences in the 30 degree wash cycles seem to tie up nicely with the relative difference in motor pulley diameter.

The sensor/load/power relationship makes sense - when I take the 1200 motor apart I'll have a look for it.

Cheers,

Steve

[Whitegoodshelp (Andy)]

Hoover used to fit the same module or programmer to 800, 1100, and 1200 spin machines and the same motor. Instructions were to cut this link for 1200, cut this one for 1300 etc. The faster spin machines had a smaller drum pulley too.

[Stevethesax]

Well, I stripped the 1200 motor down today to give it a bit of a service - and while I was there I had a good look around for the speed sensor. Couldn't find one. Apart from all the usual wires and connectors the only other item of note was a temperature sensor.

If there's one at all I'd imagine it'd be on the drum casing somewhere...unless they're getting feedback from the motor in some other way.

Cheers,

Steve

[Whitegoodshelp (Andy)]

The speed is controlled through monitoring the small tacho coil and magnet at the end of the motor where the motor plug is. As the armature turns, the magnet revolves and the control board can count the revolutions.

[Stevethesax]

Aha! That would be the odd-looking 'doughnut' just before the rear bearing. I wondered what that was for...and now I know!

Cheers,

Steve