Why do frontloaders use so much less water?

[lowefficiency]

>> First, most bearings favor only one direction of operation; top-loading machines require the bearing to
>> both resist forces side-to-side (from spinning or rotating) and up-and-down (to support the basket and/or
>> agitator/impeller). No bearing is excellent for that -- roller bearings would not do well with supporting the
>> weight, ball bearings wear out faster in this mode than in other modes, and the bearings that set rollers at
>> a 45 degree angle, which in theory would help in this mode, are not very good at hight speeds for spinning.

Is that really a problem though with proper bearing selection?

For example, tapered roller bearings handle all kinds of continuous hard loads in service as automotive wheel bearings, including high side loads at speed. I'm not a subject matter expert, but a quick look at the SKF website shows all kinds of tapered roller bearings with extremely high speed ratings... such as the SKF 30202 which is rated for 17,000 RPM use with a do-not-exceed limit of 20,000 RPM. If our washing machine baskets could hold together at that speed, we wouldn't need dryers at all!

 

[earthling177]

Dave (LowEfficiency) asked:

« Is that really a problem though with proper bearing selection?»

Well, it depends quite heavily on who you ask. And, I am probably not the right or best person to ask. If you knew my dad, you could ask him, or I might ask him when I visit him in July or so. He was a professor of mechanical engineering since before I was born and retired in the last decade.

So, what you are getting here is essentially second-hand info, but I grew up hearing all about that kind of stuff.

Yes, a tapered roller bearing, usually a bed set at about 45 degree angle, can support such loads better. You will usually need 2 of them though. And they are way more expensive than a regular bearing.

I may be wrong, but I have never heard of *any* vertical axis washers using such bearings to support the basket/agitator, they may use them elsewhere in the transmission.

This market is riddled with manufacturers trying to cut every corner to save a few cents.

A regular ball bearing *will* more than likely outlast the machine, if the seals hold, and they save money on the seals too, instead of getting the highest quality stuff. Engineering is often a place where you need to balance how long something will last vs. how much they cost. It's true that a washing machine bearing generally wears out a bit faster then if it were in another machine, but if people are doing laundry right, the seals are more than likely to hold and the bearings will not be the main cause of trouble.

Also, sure, you can ask Timken, SKF, and many others for specialty bearings for nearly any situation. SFK, I believe, started making a special bearing for FL washers back in the 70s or 80s, and the whole purpose of the bearing was to enable the manufacturers to shorten the amount of space in the back of the machine, so you could either have a smaller machine for the same size/capacity basket, or you could have the same size machine with a higher capacity.

I find it hard to believe, however, that bearings for the speeds you quoted are for automotive wheels, those are much more often under 1,400 rpm and even more commonly, under 850 rpm for the common speeds.

In any case, my whole point is that the things people tend to say to poo-poo horizontal axis machines in US are often not true, or just partly true, and even now they've been disappearing, because the washing machines manufacturers are now making horizontal-axis washers and lost interest in hurting their competitors.

Cheers,
      -- Paulo.

 

[johnb300m]

I agree Paulo.
Front loaders get a bad rap for bearings not because of the inherent design of the front loader itself.
But because the manufacturers use the very cheapest bearings and seals they can afford.
And leave it up to the jaded engineers to sort it out with the pittance of a budget they’re given.

 

[henene4]

While there are bearings that can support loads in more then 1 dimension, those are often more expensive and can't quite absorb the same forces in each direction for the same size and price.
And those bearings often if not always need to placed in pairs to create a symmetric load patern.

Thus it is more common to just use 2 bearings or if loads in one direction are minute to just slightly increase the rating of one bearing to absorb the additional loads.
Most bearings can actually absorb loads in 2 dimensions, just that one dimension is orders of magnitude less loadable and overloading in that direction is way more damaging way faster.

You can quite exactly calculate the lifetime of a bearing under certain loads and conditions.
And the lower the requirements there are the cheaper you can make them.

Much of that comes down to lower material and precission requirements.

Which in turn can also interact with sealing of bearing in question.

There can also be many ways a bearing can fail.

The running elements, be them balls or zylindric shape, can wear down uniformly. That wear happens gradually and can be verry much reduced by good lubrication.

If those elements are manufactured badly they can wear down unsymentricly causing much faster wear.

If the material run of the rotating elements creates larger particles wear on the bearings is faster.

And once a bearing ages and there is more play in it, quickly changing loads over time can cause even faster even more catastrophic wear (hammer on nail principle, especially significant with the highly hardend brittle materials used in bearings).