Input requested on rsmh build

Hello everyone. Thankful for this forum. Would appreciate your input.

After what I thought was sufficient research, (yes I have "The Book" lol) and close attention to the proper dimensions,

I started in on my first rsmh -

1 1/4" x 9 x 4 1/2" firebrick lined, three 8" masonry chimney flues - 36" tall.

Burn chamber is (approx.) 7 3/4" tall x 5" wide x 13" deep.
Total burn area is 21" long including the 8" flue width.

Feed tube is a 6x6 rectangle metal tube cut at a 45 d angle.
(This angle was chosen to allow for a self-feeding pellet option at future date).

A 1" high metal grate sits on the brick and fuel then sits on this grate while burning.

Door when open fully allows air into burn chamber opening which is (as above) 7.5"h x 5"w.

Two air intake baffles allow adjusted air in under the 1" metal grate when door is closed.

Burn chamber is insulated 1 1/2 w/Perlite both sides, but not the top or bottom.

Top of stove was not fully sealed. (No gasket material installed yet on the top inspection plate).
Consequently, stove was losing heat out of the top before it could be directed down to the exhaust pipe.
Can be easily rectified with gasket material installed.

Exhaust diameter is 8".

Chimney is insulated with 1 1/2" Perlite all four sides.

Fired the prototype up yesterday.

Stove drew well, little smoke back-up. After 4-6 mins, no smoke out of exhaust flue.

Heat at the top of the chimney was + - 425 d. F.

Problems:

Stove doesn't achieve that "rockety" sound when burning.

Could not detect the vortex type fire expected in the flue.

Should not the stove generate higher temps?

My thoughts are:

1. Because of the angle of the feed tube, (45%) the wood is burning too close to the chimney, with not enough (length) time for a good burn?
In other words, burn chamber needs to be longer?

2. Burn chamber is too tall?

3. Burn chamber is too wide?

4. Needs insulation bottom and top of burn chamber?

5. Feed tube is too large due to the angle? A 5"x5" tube at 22.5 d would be better?

Those are my thoughts.

Your thoughts welcomed and appreciated.

Hi Thomas; I need pictures to visualize this

Feed tube needs to be vertical.


IIRC, about 15" 38cm high for a 8 incher, from the very bottom to the top. And burn tunel lengh should be about 8 inch. (18cm for me)

Yep, pics are needed. And burn tunel+heat riser should be insulated all around.

Thanks for your replies.

Feed tube is about 18" tall bottom to top. Any harm in being taller than 15" ?

I've seen feed tubes angled like in the photo.

Why does the feed tube "have to be vertical" please?

Thanks, TW

Thomas Winters : 90% of all our previous remarks can be thrown out the window, we didn't know you were trying to combine a Cob-Build style Rocket Mass Heater
With an All Metal Wood Stove, All I can say is good luck !

A final suggestion, even though I hate most of the Crap that passes for Rocket stove Builds in You-Tube land, you should go to You-Tube, and type web4deb into
You-Tubes search engine, from there you should be directed to the 'web4deb channel' scroll down to the set of rocket stove videos he has put up there!

Again good luck ! Big AL !

Yep, seen those videos Big Al.

Thanks for your input.

Thomas, an all metal construction is doomed! Been there done that. Won't last. I burned my first , melting a gas bottle in less than 30 burns. 5mm thick steel getting to the verge of being liquid and bending downwards because of gravity.

Tell us, so we know, are you intrested in making something cool and which you will be able to brag about? Or make a working and clean rocket? As in clean emissions. Metal lined with firebricks, and insulated on the outside is possible for example. Angled feed doesn't give enough turbulence.

"Thomas, an all metal construction is doomed!"

Absolutely agree.

That is precisely why I did not build an all metal rocket stove mass heater.

Thanks for your input.

Tom, a couple of thoughts.
One, the picture you posted to demonstrate that people have used angled feed tubes seems to have caused some confusion. People are assuming that is a picture of your project.

Two, have you experimented with your airflow by restricting the feed tube opening? Seems to me it would be a really fast test to see whether or not you're getting too much air into the system, which might contribute to lower temperatures and prevent the full "rocket" effect.

Other than that suggestion, I've got nuttin'

That photo is a picture of my project.

Good idea Peter. Yes, I did do a minimum of testing with the air flow. I'll play with the air intake once I get the stove installed with the longer length of exhaust pipe I have planned.

The stove actually achieved 452* as a high temp, not 425*.
That temp was measured on the metal on the back side of the stove at the top of the outershell, not in the heat riser itself.
My guess is the heat riser temp itself was a bit higher.

Also, it was a 90* + temp day, so the draft was not quite as good as it should be under normal cooler/colder weather use.
And the exhaust pipe was only 9" long.

Thanks for your input. T