Designs for movable RMH for my garage?

New to the forum and this is my first project. I am wanting to build a RMH for my garage when I am out there but would like for it to be movable. Saw a few designs that use a 55 gallon drum that gavery me the idea to build one and put it on a 4 wheel drum cart so I can move it if needed. I think someone called it a 55 gallon pocket rocket. Any suggestions would be greatly appreciated

Here is one that was built at a Pyronaut workshop a couple of years ago. It uses a commercially produced combustion core, but you could cast your own core if you can follow directions exactly.
https://permies.com/t/55001/Teeny-Tiny-Mass-Heater-Kickstarter#456526

Ask if you want more detailed information on doing this. There are also other designs that might do what you want, like this which is similar to a pocket rocket: interior view of the Nymph.

Looks a bit on the large side. Could I do something similar with a 55 and 30 gallon drum instead?

Howe about a design like this one? Is it efficient? Kinda like it because being a carpenter I get a lot of scrap lumber including 2x4 and other long pieces and it will accommodate them.

Both the Minnie Mouse and the Nymph are based on a 55 gallon drum. The Nymph actually would look and work pretty much like your picture; but it is lined and divided with firebricks so that it has some mass, and will burn hotter and more efficiently without destroying the barrel quickly.

I didn't see a minnie in the post. So what if I pot a 30 gallon inside a 55 and fill around the 30 with insulation mixture. Then build a divider from the bottom to just below the top in the 30. So 2 chambers like yours. Then have exhaust go most of the way down in the 1 chamber and same for the feed tube in the other chamber.

This is kinda what I was thinking. Sorry I'm not much of an artist.

Oops, sorry, I gave the wrong link above, to the Fat Rabbit instead of the actual Minnie Mouse heater description. This is what I was talking about: https://permies.com/t/40/44671/rocket-mass-heater-pyronaut-event#411317

The Nymph design will work well (tested and proven), and be much more durable than the apparently all-metal design in your sketch. I am not confident about the multiple ups and downs you show, either - they would cut draft strength.

Since what you are talking about would not connect to a mass or serious radiator, insulation around the combustion zone would make for a nice hot fire that doesn't do much of anything to heat the space. You need the firebrick lining, which will slow the heat transmission a bit, but store a lot of heat and radiate it out to the room. It would probably warm your shop for an hour or more after the fire is out.

O ok. So maybe eliminate the inner wall? And does it have to be fire brick lining? Was planning on putting some in the bottom and the rest was going to be a mixture of vermiculite and other stuff.

Not just eliminate the inner wall. I would suggest looking closely at the Nymph, since that is the basic concept you want to develop, and following its construction details. Erica has done a lot of research, and knows a lot about what works and what doesn't.
Specifically, you do not want to use any vermiculite or perlite (unless in the base to protect the floor/pavement); you want thermal mass, not insulation, and materials that will resist many cycles of extreme heating and cooling in an oxidizing atmosphere (not steel).

I saw a picture of it. Any chance you have a drawing possibly with some measurements? I decided to experiment and make a mini one out of a paint can. Turned out pretty neat and kinda understanding how they work a little better now. Also is their a formula for designing one? Such as feed tube angle and diameter, connecting tube length and diameter, burn chamber high and diameter.

The pictures are of Erica Wisner's prototype, and I haven't actually been able to find more information on it. She may not have published the full details yet; maybe asking her in this forum would bring out enough info.