TLUD biochar problems

I thought asking here might save some time experimenting.
I have made charcoal a couple of times in a 55 gallon barrel that I cut the side out of, it works pretty well but I don't like standing there feeding the fire for several hours.  Last weekend I tried to make a TLUD from another barrel.  I drilled 3/4" holes on a 2" grid covering the bottom.  The after burner was made from an old burnt out burn barrel about 16" tall and I found something for a chimney, a piece of thin walled pipe 8" in diameter and 28" long.  
The problem occurs after 45-60 minutes.  Initially the burn starts great, no smoke and a roaring fire but then it starts to smoke a little, the longer it goes the more smoke.  First time at 60 minutes it started smoking, I thought it might be done so I closed up the barrel top and sealed the bottom.  When I opened it the next day about half the contents was charcoal and half was still wood.  
Today I reloaded it, including the un-charcoal, and started again.  All went well until about 45 minutes then. the problem repeated., a little smoke that gets progressively worse.  After 5-10 minutes lots of white smoke was billowing out, again I closed everything up, sealing the barrel.  I know that most of the wood is still wood.
Could the chimney be to short, inadequate draft?  There is quite a bit of air flow in the after burner, perhaps too much, again inadequate draft to pull air through the bottom?
I like the fact that I just fill/light and watch while doing other things but I have to get it working better.
The wood is dry, cut last winter and stacked out of the weather.  

I think everyone using a TLUD has experienced the same issue.  I had much better luck when I used a second full barrel as a chimney.  Restricting the flow at the top of the first barrel never worked well for me.  

I tried holes in the bottom of the barrel as you did, but it's much easier to tell when the burn is complete if you make the holes on the sides of the barrel about an inch or so above the ground.  You can just look in the holes and see that the wood at the bottom has turned to glowing red coals.  The wood won't be turned to charcoal everywhere at once, so when you see bright red glowing coals inside any given hole, you can push dirt over that hole with your foot, and then watch the other holes.  If you want to try that, the holes in the bottom of your barrel won't hurt anything, just set the barrel directly on the ground rather than propped up on something like I assume you are doing now.

One other thing that helped me is to drill a ring of holes near the top of your main barrel.  That allows some air to get in after you put the second barrel on as the chimney.  That seems to help with an "after-burn" to help burn up the smoke that starts partway into your burn.

Hope that helps.

Thanks for your reply, I will try your suggestions.

I have had some bumps along the road, but I have used the TLUD very successfully for many years.  Here is the original video I started from:

https://www.youtube.com/watch?v=YIbGkmt1VdE&t=43s

I don't think that closing the top will help you.   I had some problems like this but I had a chimney that was about 5 inches wide. When I switched to a chimney that was 10" wide, it got much better.  Another thing that helped was that I realized it burned better with the chimney on. When I added more wood, instead of taking the whole thing off and putting a lot of wood in, I just tilted the chimney and shoved a piece of wood in quickly and didn't put in another until that one started burning a bit.  

I don't burn biochar in the winter because it is so cold, wet and dark here that it's just not worth it.  I stopped about Dec. 1.  I won't burn again until March, probably.  

Is the wood packed in densely or wet? You don't want either of those situations.  

The air is supposed to move smoothly up from the bottom so that the gas coming off of the wood burns, and goes smoothly out the chimney, maybe reburning some of the smoke to clean it as it goes up.  

I'm sure that this can be fixed.   My TLUD works great and I bet yours will too.

JohN S
PDX OR