Not sure how common the problem is but I did find a drum with cracks and had to replace it on the WD45 I completed a year ago. Some pictures on my thread. New drum was about $80.00 I believe. I got mine from Sandy Lake.

Once the final is removed, and what's left of the drum knocked off.

A good way to get the remaining hub off is.......

Find a good tapered-end punch. (~ 5/16 dia tip works good)

Select a corresponding drill and drill a hole into the hub over the key, but not through the key.

Support the hub on the opposite side with a heavy buck; a third hand is ideal for this.

Or lay it down on an anvil or something that won't give. 

Start the punch in the hole and give it a few substantial whacks with a 2# hammer.

Hub should crack along the keyway.

The idea is to make use of the taper to force the hub to crack apart.

It's helpful to use a thin grinding blade to slice into the hub as deep as possible above the key.

We used the punch method for all of our brake jobs on A-Cs with those type of drums.

There were plenty of cracked drums to be found.

Good advice from Sugarmaker.

IIRC, the axle seals were leather.  New ones will be rubber,

Installing new drums can be a challenge too.  Best to uniformly heat them up and slide on.  Make sure to they are seated on the round ring.  A long pipe that will fit over the axle & sledge at the ready will help to drive it home.

Worst case; remove axle from final housing and use a hydraulic press to do the above.

Keep track of all shims !

I'm not far away, just a few miles east, south of Tofield.  Apparently those drums are a bear to get off.  So far, Ive been lucky and haven't had to replace one.

Sent you a PM.

Neighbor many years ago asked me to help him out... the tractor he and his father bought in the early 70's hadn't been run in over a decade, and needed to be awakened... having a serious emotional attachment, he couldn't work on it alone, and of course, he wanted someone with a bit more hands-on experience leading the way... so I did it.

Short story, I got the carb cleaned, everything  checked, battery in it fired up, aired up tires, went to back it out to give it a short drive-test, and he offered me a warning:

"Hey... just so you know... it's an old tractor... one of the brakes doesn't work!!"

My answer was:

"You mean ONE of the brakes actually works???"

It took him a moment, then he got a great big grin...

I have suffered the drum failure on my wd45.  I have found a bunch of videos by Nash Summers on Youtube.  My question is can the assembly with the bull and pinion gear and the shaft with the brake drum be pulled out and then deal with destroying the pin at the bottom should it not come out for me.  I am thinking that pin might be bent or damaged as something was making noises and vibrations before and after I decided to tow it instead of driving.  Looks like about 5 or six inches of the outer portion broke off. Some pieces came out but some there is a piece too big to come out the hole at the bottom.

Thanks