Two way diverter valve in rocket mass heater?

I'm wondering about putting a valve in the piping downstream from a rocket mass heater barrel, to divert hot air from one area to another on demand. Is this feasible?

For background, I want this rocket to heat a bench and a set of hot frames. Both many not need to be heated at once, and I don't want to waste heat. The whole rocket is under cover but outside, so potential for a deadly accident if something goes wrong is lower.

If putting some sort of two way valve into a rocket is OK, what kind of hardware would be best for this? I'm thinking I should make it double as a clean out so ash and stuff does not get hung up there.

Hi Gilbert.

Although I can't direct you to a specific example, there are Rocket Stoves with diverters, to channel the hot gasses from the barrel into a different set of mass bench pipes, or into a bell (stratification chamber), so one could alternate.  It seems logical to do as you mentioned: to also have a clean out at this location.  The easiest place to do so would probably be at the manifold outlet; I have seen a video where this was done, but I don't have a link for you.  I am considering something similar.  Surely someone with experience building these will chime in.  I think any heating supplies store that sells ducts and stove pipe would be able to show you how to build it.    

Good point; the piece I am looking for should already be used in ordinary duct work someplace.

I don't think you will find a suitable drop-in item. I think you will need to modify a standard damper with an off-center unpierced sheetmetal flap to block off one path or the other. This would mount in the fork of a "Y" or tee fitting.