I have a gentleman down the street, fixed income, no kids to help him out, can't
get a car, rides bikes from the thrift shop, $10 to $30 range.

He rides very slowly, to and from the store, doctor and park but has had three
bikes develop the same problem. He is not heavy, 180 maybe.

The rear wheel gets badly warped and the crank bearings come loose.
I have fixed the crank bearing on two of the bikes several times. I do
my own repairs and have never had a problem with mine and I do 60+
miles rides on a regular basses. I have done the rear wheels several times
and he came by today with the wheel on the Schwinn Varsity completey
bent against the frame. He said it happened while he was just riding down
the street, started rubbing and then stopped altogether. None of the spokes
are broken, but the wheel has a flat spot now, about a foot long.

What am I missing here?

If I thought it was just the bikes, I would go to Wally Wally and get him a
new bike. But there is some thing else here??

Sounds like the BB needs to be overhauled and tightened up but loose on the bearings. I would suggest truing the wheels up maybe even overhauling them but if the rims are flat, not much you can do other than replace the wheel.

One thing I notice about older folks who aren't "knowledgeable" riders in a sense - let's say early 50s and up - is that most will ride the bike 100% in the saddle.

Literally, when they approach a pothole, edge of a curb, etc...it is literally - PLOP! - and continue on. All the weight was driven directly into the wheel.

This will take out undertensioned steel rims in no time at all....same for alloy wheels but a tad longer.

Sometimes the best solution for determining what is really going on - sorry to say this - is to observe how they ride. If it sounds like spying - welp that's what it is.

Once had to drop a customer who kept scaling up his wheel builds attempting to build the "ultimate" and "elusive" "light but strong" wheel. Got tired of seeing a wheel come back every week or so.

Then one day, I saw how the customer performed left and right turns - suffice to say they weren't turns by any figment of the imagination. Flat out refused to build any more wheels for that customer after that.

=8-)

This gentleman is in his early 70's! He has knee problems.
His seat is too low and likes it that way. At least on
the Schwinn it will only go so far down, unlike the
MTB he has, he looks like a grasshopper riding a bike.
And yes, he never stands on the pedals.

I have torn down the BB and cleaned and inspected
ever thing and they look fine, but in a week or two
they are loose again.

I think he is messing with them, although he says not.

He needs:

1. Double-wall 26 x 1.75 or 700 x 35c rims. (Think Rhyno Lite...or cheap Kruzer Kings...)
2. Single-butted 2.3/2.0 spokes.

Would be nice if he could go with solid axle hubs with M14 axles...but the dropouts call the shots here. Best thing you can do for the hubs in such wheels is to make certain they have hardened chromoly axles and the the dropouts on the bicycle are properly aligned - i.e., perfectly parallel in plane.

=8-)

How about finding him one of those "full-suspension" BLOs (Bicycle Looking Objects) from any convenient department store?

They're perfectly fine for that kind of sedate riding if you check the assembly and should do wonders for reducing the shock load on the wheels from a rider who can't /won't go light when hitting a known obstacle. Maybe swap in a SS hub for a stronger rear wheel.