As some of you may know, I am in the process of building a 7" batchbox RMH. It will be replacing my 8" J tube core in the shop.
To utilize the higher heat output of a batch, I need more "ISA" internal surface area.
To gain quite a bit of that ISA. I will be adding a second 55 gallon barrel on top of my first.
I innocently assumed that adding a second barrel was as easy as sitting one on top of the other and clamp ... not so!
Luckily I posted this question at Donkeys pro boards. Peter answered promptly and gave me the needed information.
To start , two bung barrels(non removable lid) ,will not clamp together as is. The rims are thicker on the non lidded barrels... Who Knew?
I tried and confirmed this ... it "almost" works but...not good enough, I would not trust it.
However, judicious grinder work on the lip, can remove enough material to allow a barrel clamp to get a solid grab.
There is also the Tim Barker method of removing the entire lid with a grinder.
Standing a barrel on end. A grinder is used on the lip. Round and round ,keeping your grinder horizontal. Soon a crack will appear, follow it around the lid and when it comes back around ... your entire lid falls inside the barrel!
This works very well, leaving a smaller lip still firmly attached to the outside of the barrel. Plenty for a clamp to grab on to.
An alternate method comes from Ernie Wisner. I have not tried this yet.
Two removable lid barrels , one lid and two clamps are used. The lower lip on these barrels is not as thick as the bung barrels.
Cut the bottoms from both barrels. Use one clamp to connect bottom to bottom. One open end goes down on top of the core and the other end gets its original removable lid and clamp.
Of course those with a welder can simply weld both barrels together.
I also am wanting to add a second barrel for my workshopdragon to extract more quick heat out of it. Since I don't have the horizontal space to add any more heat extraction methods but have over 10 feet of vertical to go up, I went with this option. Being my workshop which really benefits from quick heat while I'm in there on and off through the day, adding mass would not help very much.
I managed to get one end off using the Tim Barker method as Thomas described.
The only thing at this moment that I would add to the description is once the lid falls free, the remaining lip just needs to have the sharp edges rounded with a file. Also, don't think that you can remove the remaining metal that wraps around the lip which secured the lid the barrel. The crimp is so tight that the metal just doesn't want to let go as if they have almost merged together.
Total time to do one lid was about half an hour and used up about a 1/3 of my metal grinding wheel.
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