Tumbler doesn't start rolling when powered on with barrel on

It might be slightly overloaded. If it doesn't start, take the barrel off and start the base then put the barrel back on.

This happens to be on both my 33b and qt66. I've replaced belts but sometimes it still happens.
Usually a little lubricant on the bearings keeps things rolling for me...

I too had this problem on my 1960s? Lortone QT6 recently. So I experimented w flex seal. Issue: Nudging the barrel helped only intermittently. I sand papered the drive shaft on it and I replaced the old round belt. Sand paper on the super dried out (old) barrel didn't help. When that didn't help I decided to spray the barrel with flex seal. That sort of helped. When I put the barrels onto my QT66 and nudged it finally started rolling. Flex seal did not adversely affect the QT66 drive shaft (yay) but stuck a little to the QT6's vinyl coated drive shaft. I think the load may have been too heavy on the QT6, that said, it has just a one year old motor. I bought a new drive shaft for the QT6 and it's covering is more rubberized. I have yet to install but hopefully that will solve the issue. I'll report back on flex seal.

In a strange coincidence, I had two different Lortones stop last week, both bases for 12lb barrels. Both still have power, but no rotation, even after the barrels were removed. It bothers me to think of current going through any motor but not rotating the motor shaft.

I always keep a spare motor at the ready and have been through this before. So, I use this time to do a "refurb" which involves cleaning the bases thoroughly, making sure shaft end "bearings" are okay or not, and rescratching the shaft sleeves. I use 60 grit sandpaper folded, and do this pretty vigorously along the length making the sleeves grabby again. Then I check the belt and pulleys. I've never had much wear on the large steel driven pulley. But after some experimentation and trial and error, have learned some things about the belt and aluminum drive pulley.

A new belt and new drive pulley will meet such that the belt is too wide and high to seat fully down in the groove. It will set down a bit more than 1/2 and leave perhaps 1mm above the pulley. Now, both wear down and the belt goes further down into the pulley as both wear. That's why we have to retighten the belt now and then. If the belt gets low enough in the pulley to bottom out, friction is from that point forward a problem and tightening the belt won't solve it. So I check these each time.

More or less, I've learned that if the belt seats entirely within the pulley w/o any sticking above, to go ahead and put on a new belt and pulley both. If done this way, then I will often get 2-3 years after w/o even having to retighten anything.

As to the motor, I've never had one fail per se. After taking the one off that failed to turn, I first see if it will rotate by finger and it always does but only with pressure--not good. Then I blow it out hard all over with compressed air and all kinds of dust and crud comes out. Then I put 5 drops of oil in each oil hole and let set for an hour. Then I plug it in and it's like new and becomes my backup for the next time this happens. Not sure why this happens. I do put a drop in the motor now and then, but the owner of Lortone told me that doing that too much will cause as much problems as doing it too little so be careful.

I also now and then scratch the outside of my rubber barrels the same way, lengthwise. These barrels get glossy after a while and rescratching gets things going well again. I probably have to do this about once/year.

I think the ideal timing would be to put one drop of oil on the shaft ends monthly but sometimes I remember and sometimes not.

On the flex seal: if the temperature is hot where you are running your tumblers the flex seal could work against you. It stuck on the roller a bit. I suggest what someone said in a different thread: rubber bands around barrel... can't take the credit on that but don't know whom to assign it:)

Well, oddly, since this thread started I have had two Lortone tumbler bases stop rotating, both of the type that hold either 12 or 6lb barrels. So, I did my refurb like before. This time one motor failed again a few days later. I had never had this happen before. For it, just holding it on the bench and gripping the shaft with my fingers in a very hard grip with a rag I can stop the rotation. I could never do this before with this test, so it's weak. No wonder. However, it has been cleaned, it runs well and I can see no problems. I tried putting it back on the tumbler several times and to no avail.

If I hold it still, or if I find it no longer turning, I can feel the hum of it with the electrical current, yet apparently nothing goes wrong even though this scares me a bit. I have not yet called Lortone, but will. What in the heck can cause this? If there are no brushes to wear down and the bearings are lubed and run freely, what can "wear out"? It, like my others, is about 7 years old.

That's actually a specific issue in mine, and it doesn't have a barrel guide (mine is from the 80s I think). I've got a piece of cardboard that I put on the bottom of the barrel, and I've been running fine since. Cardboard grinds on the frame, but doesn't cause enough friction to create issues with the rollers.