Pocket Rocket materials and dimensions questions

Hi,

I'm considering a pocket rocket for my 6' diameter sauna. I much prefer to use items I have on hand but will get different materials if what I have will not work well.

I have a 14" diameter x 24" long pipe. So, a couple inches bigger in diameter than a 5 gallon bucket. The steel on this pipe is thick - 1/8". I was thinking I could cut it to whatever length needed then weld on a bottom and top (holes for feed tube and chimney).

I also have a similarly heavy 6" steel pipe that could be used as the feed tube.

Lastly, I have lots of 6" stove pipe.

I have much experience with various wood stoves but only knowledge of rocket stoves. I assume a pocket rocket with a diameter of 14" will be plenty for the 6' diameter sauna, correct? (my idea was to surround the bottom half of the pocket rocket with rocks)

Will the 6" feed tube and 6" stove pipe work ok for my 14" pipe....or do the ratios need to be different?

I like to run my stove pipes vertically with no elbows. However, in the case of my sauna, it would be much easier for me if I were to run the stove pipe vertically about 3' then run it at a 90° through the wall then another 90° to get it vertical again. Will that work with a Pocket Rocket.....or is it critical I run the pipe vertical all the way? (if it matters, I'm concerned with smoke.... i.e., I'm hoping to have something that draws well so I won't have the smell of smoke (excessive) distracting from the experience)

All insight appreciated! Thanks!

rusty

Rusty, it will only be temporary. Metal don't last well in rockets.

Tho, for a pocket rocket, you could try it.

So, lining the bottom with firebricks could be interesting.

https://permies.com/t/55001/Teeny-Tiny-Mass-Heater-Kickstarter#457129

Make your top removable, for cleaning, and repairing. Make your metal feed tube removable, for replacement.

Thanks for the info, Satamax! I could understand the metal in a barrel or bucket burning out rather quickly. But this is steel that is at least 1/8" thick...perhaps as thick as 3/16".

For a sauna, that will get used half dozen times a year, I was thinking that thick of steel would outlast me. Granted though, I have no personal experience with these particular stoves.

Thoughts?

Well, now it's all left to you.

I have never killed a pocket rocket. Never ran these for long enough. But some people have, and have done it fast. Tho, they were barrels or buckets. I have killed a super insulated J tube in something like 30 burns. I even managed to make the 1/8 thick steel sag under it's own weight.

Thanks. I just came in from looking at my pipe and it is thicker than my earlier guess. It's a whopping 5/16" thick!

Any thoughts on the size of the feed tube and chimney for my 14" pipe diameter? I see that Ianto recommends a 4" chimney for a smaller 5 gallon bucket. I reckon 6" would be roughly right for mine....but then would I need to have a bigger feed tube...like 8"?

Both tubes should be the same iirc.

What makes pocket rockets so hot is velocity of the gasses.  It's ramming in oxygen as if you were using a bellows.  If you have a nice long chimney to make a good draft and an intake  that isn't too large(and not too much air leakage around the lid) you get plenty of suction down the intake pipe right at the fire- that makes high velocity = rockety.
If you think your elbows are restricting flow at all you just add a few more feet of pipe above them and you'll get a better draft- the longer your hot gasses stay in the pipe the more "suck" you'll have at the intake.

Thanks for the info, Roy!

And Satamax....I'm probably going to feel silly for asking....but, what is "iirc"?

Took me ages to figure that out
If I Remember Correctly

On the subject of pipe size though... You're taking in cold air and heating the crap out of it making it expand greatly. In my mind I'm thinking the intake should be a bit smaller than the exhaust to promote high velocity flow. If both are 6" but there's some wood(fuel) standing in the intake pipe there's your restriction.  

Ah. Thanks!

Re the feed and chimney pipe sizes: I've thought about this overnight and looked through Ianto's book again. I wonder if it could be analogous to putting a small tip on the end of a garden hose....creating high pressure....which, in the case of a smaller chimney, it might force the emissions out and through at a faster rate which pulls in air in at a faster rate??? Just thinking aloud here.........  

Of course, I have no idea. Ianto seems pretty clear on the proportions though, and the chimney is smaller. Wish he would have explained his reasoning behind that.

Here's what I came up with. (sorry, it's the best video I have of the stove). The stove itself consists of 4 pieces: the firebox (14" dia 5/16" pipe), feed tube (7" dia 3/16" pipe), 6" chimney, and the top which is a disk from an old farm disk... welded on concave side up so it serves as a place to melt snow or steep water with essential oils. The stove does not have a bottom. It just rests on the cinders that insulate the sauna's floor. Very simple and solid.

Very happy with this set-up. The stove burns very fast and hot and seems perfectly suited for this 6' diameter sauna.

The sauna itself is a grain hopper/silo that was headed to the scrap yard. The walls and benches are redwood and the ceiling a mix of redwood and cedar. The floor is fir, bearing on cinders harvested nearby. With the exception of two stove pipe elbows, some silicone, and nuts, this sauna was made entirely from materials being discarded or burned.

Nicely done! If it is only used a dozen times a year more or less, it will probably last a good number of years, maybe as long as the enclosure. Certainly worth the work of building it and diverting the materials from the waste stream.

Glenn Herbert wrote:Nicely done! If it is only used a dozen times a year more or less, it will probably last a good number of years, maybe as long as the enclosure. Certainly worth the work of building it and diverting the materials from the waste stream.

Thank you! This is its second winter. Been fired up a ~dozen times total. Really enjoyed building it and have enjoyed using it even more.