Here's the bottom of my smoker. Trying to figure out the best method of attaching these casters. The smoker will weigh around 200 lbs by the time it's full.
That's what I was thinking. Make it look like a cart that movers use for heavy furniture and screw that to the bottom. I think this is what longrifle is thinking too.
Lag the casters directly to the ends of the legs. For each one, use 4 lag bolts (with washers) that are about 1/4" dia. by maybe 2" in length. Mark and drill full length pilot holes that actually angle inward maybe 5-10 degrees so that the lag bolts tend to travel slightly towards the middle of the 2x4s. Make the pilot hole pretty close to full diameter so that coupled with angling towards more meat, nothing splits. That's only 50 lbs per wheel with two lags per board. Should be fine unless your towing it with your truck.