How critical is ?

Hello and good day to you all.
Having recently completed a rocket mass heater to to specifications of "the Bonny" plans by Ernie,i realise that a bigger (larger diameter) fire feeder tube is needed for the purposes i require. Although the b"bonny" uses a 8 inch tube system,i have had to use 140mm tubing (+/-) 6 inches diameter some the fire feed tube is the same. My question is ,what is the maximum diameter to which i can increase the diameter of the fire feed vertical tube? If anyone has done this type of adaptation ,or knows the dynamics of this ,i would sure appreciate your input before i go cutting my stove about..

Martin, this book gives all the critical measurements. http://www.rocketstoves.com/
Have a Great day. Jay

Martin Jackson : I second Jay's suggestion, Ernie and Erica Wisner have to assume you have done your homework when you buy their plans, an 8 inch system
should be 8'' Inside diameter everywhere, to give you the Constant Cross Sectional Areas through out your build, ''The Book" Jay is referring to contains the
simple instructions to Allow you to figure this C.C.S.A. out for yourself.

There is also help with understanding the Ratios of Depth of Feed tube, to Length of Burn Tunnel, and Height of the Heat Riser!

Rocket Mass Heaters, 'The Book', mentioned here is also a valuable source for quickly learning the vocabulary of our little craft, making sure that when a
Fellow Member comes here with a question or comment on an observation, that he is using the same words to describe the same Part/section, its size, shape, and
orientation to its self and other Parts/Sections ! The $18. cost of a PDF Copy of 'The Book' would have saved you from this basic mistake, saving you time, money
and frustration ! Once you have a more thorough grounding in the fundamentals, you can come here 24 / 7 and expect to find Help from your Fellow Members !

For the Craft! Think like Fire! Flow like Gas! Don't be the Marshmallow! As Always, Your Comments and Questions, are Solicited and Welcome! PYRO - Logically Big AL!

Thanks for the advice folks. Maybe i can get upto speed now ?

Hello lovelies,

I want to build a 7" batch with a metal barrel as part of its bell system.

My guess is that the longevity of the lid of the barrel/ bell depends on the distance of this, i.e. the lid of the barrel, to the top of the heat riser.

In order to avoid it warping/ decay prematurely, what is a safe/ recommended distance between these? I am struggling to find this number now.

As far as I understand, for the same heat riser diameter, a batch will produce more heat than a rocket. I am looking for the safe distance between those two things for a batch mass heater.

Cheers