I never did bother to calculate the centripetal/centrifugal forces for our first automatic washing machine drum (The very first Hotpoint Quartz model which did away with the rather klunky electro-mechanically driven "programmer switch" by using a micro-processor controller board).
Strangely enough, this modern doff of the hat to "reliable state of the art electronic control" was the very first failure after just a week or so (possibly straight from the off - the details are now shrouded by the mists of time) requiring a visit by a service engineer (covered by the warranty) who changed the controller board out.
After that, we never suffered any further controller board faults in the remaining 20 odd years that I was able to keep it going, not even after I modded the board with additional ttl chips mounted "dead bug" stylee to adapt an ex-Bendix washing machine motor used as a free alternative to the disgustingly expensive Hotpoint spare.
The Bendix motor was retrieved from a washing machine that had landed up in our works skip as a "Just might come in handy item to possess". How little did I realise that my 'foresight' would be put to the test! :-)
Anyway, I digress from the point I'm about to make but I think this anecdote about being able to fit *any* washing machine motor that you can get your hands upon, providing it's the same basic design with a tacho sensor (as they all are - apart from differences in mating plug, grooved shaft diameter and the number of pulses per rev from the tacho sensor), is worth reading.
When I first considered using my "Bendix Spare", the very first thing I noticed was the rather convenient feature of the drum/motor mounting bracket(s) which suggested that Hotpoint wanted to be able to change motor suppliers at the drop of a hat. Presumably a practice in manufacture that's not confined to Hotpoint alone.
Physically attaching the 'foreign motor' was the least of my problems. All I had to then do was identify the 6 wires (armature, field and tacho wire pairs) on both motor connector blocks so I could swap the connector block over to the Bendix motor, work out the number of poles used by the tacho rotor magnet (6 and 8 poles, afaicr but don't ask me which way round it was) and compare the belt pulley diameters (basically, identically grooved motor shafts - afaicr 1 inch and 1 1/4 inch shafts).
Unfortunately, the difference in tacho pulse rates didn't compensate for the larger diameter Bendix motor shaft come grooved pulley so I had to 'invent' a 'clever circuit' to divide down the incoming pulses before they hit the i/o pin on the controller so as to maintain the original
1200rpm spin speed (I didn't want to compromise the spin dry performance but neither did I want to overstress the bearings - I was acutely of the square law relationship regarding rpm versus stress on the shaft bearings).Now, speaking of "shaft bearings", this brings me to the point I wanted to make and it is this. About a year or so after owning this machine, I found myself having to buy and fit a drum bearing kit. This bearings kit consists not only of the two *taper* roller bearings themselves and replacement shaft seals but also a replacement "Crush Spacer" and preload tightening up shim".
According to the instructions, the shim (about 4 or 5 thou thick) is only used when sogging down the end nut onto a shoulder so as to get the desired amount of crush on the aluminium pre-load spacer before undoing the nut to retrieve and discard said shim and then finally tightening the nut onto the shoulder of the shaft thus correctly pre-loading the *taper* bearings.
Now, having helped my brother re-assemble the engine on his Velocette Venom with all the palaver involved by the use of *taper* roller bearings on the crankshaft, some years earlier, I knew full well the importance of the need to use pre-loading with this type of bearing (*taper* roller bearings), so when, a few months later, I noticed that the washing machine drum had lost its initial 'stiffness' I became a little concerned.
Within a year of replacing the bearings, I found myself once more faced with fitting a second bearing kit. However, *this* time I did *not* make the mistake of 'discarding' the pre-load setting shim as per the malicious instructions but held onto it ready to refit it as soon as the first hint of any slackness would appear.
A few months later, I decided it was time to add the shim back and the machine never needed another set of bearings for the remaining 16 years or so before we were offered a hardly used replacement washing machine which the missus was only too happy to accept from her daughter.
The important lesson to take from this anecdote is that it is far better to slightly overdo the pre-loading than under-do it when it comes to
*taper* roller bearings even if it means editing the final instruction given by the "helpful" instruction leaflet so that you *don't* discard the shim and keep hold of it to refit after a few months of service has further crushed the crushable pre-load spacer. IOW, don't always assume that 'helpful' instructions are always in your best interest. :-)Normal roller and ball bearings have the optimum 'pre-load' built in "by design and accurate manufacture" so this problem doesn't arise. Possibly not every brand and model of washing machine uses taper roller bearings for the drum but the problem I had with that Hotpoint highlights the problems of shortened service life due to high rpms whenever there is a significant and unavoidable imbalance to contend with such as residual imbalance of the load in a washing machine drum or the balance factor of a single or parallel twin motorcycle engine where these forces on a high revving engine can far exceed the static torque thrust forces due to a chain sprocket drive.
Note to anyone rebuilding a Triumph motorcycle twin cylinder engine; replace *both* shaft bearings with SKF ball race types, the flexure in the crankshaft ensures that a roller bearing on the drive side *will* disintegrate in short order if ridden enthusiastically (every 14000 miles in my case) whilst the timing side ballrace remains in perfectly serviceable condition notwithstanding that logic dictates you replace it anyway.
The additional sidethrust is a trifling additional force exceeded by several orders of magnitude just by revving the engine when in neutral! Don't be kidded by BSA's faulty un-thought out logic in cursing the Triumph T120V with a roller bearing on the drive side of the crankshaft.
This is yet another example of the falsity of that stupid saying, "If it ain't broke, don't fix it!" Luckily, when it finally dawns on the owner that it was broke to begin with, the solution is very simple! Keep the replacement parts order simple. Just order a *pair* of SKF *ball* bearings, no need to make the order any more complicated than that. :-)