Hunting Trailer Mini Stove

[Blitzkrieg]

Absolutely correct Mech, this was after about 4 hours of burn time and with no forced air circulation in the trailer, ambient temps were all over the place. I had readings of 55F on the floor and 120 on the ceiling. With such a small trailer having so much exterior surface area it's going to be hard to get a steady even ambient temp.

What it does show me in these early stages is that there is minimum heat transfer through the side shield. I had thought about running a fan in there to mix the air around but I was afraid it would skew my results of close to stove temps by convective cooling.

There is still room to upgrade and I think my next step will be to place shielding over the top of the stove to force all the heat up and outward from the stove.

 

[bholler]

If it is an interior wall and ambient is 85, your wall temp must be at least 85 as well to have reached steady state. You need to run the stove at high temp for a much longer period of time to get an accurate measurement of the wall temp.

Yes run it atleast a full day normally to get everything up to normal temp. Then run an entire full load wide open. A chimney fire should really be tested as well but I don't know how you could contolably create 2200 degrees in the chimney

 

[SpaceBus]

I think Vermont Stoves stopped making them around 1989, but we did have some folks getting them direct after that. wkpoor had one and Bushman bought a new one around 2009? or 2010. Might have been making them one off, but prolly not now. They still do rebuilds and refurbishing last time I checked.

That's pretty cool that they stayed in production for so long, especially with the pyrex window! The cylindrical style is very pleasing to the eye, especially with the other details.

 

[maple1]

There will likely be some compromise in the end regardless, in trying to heat that tiny of a space, with a wood stove. I don't know if one could be made that would comfortably sustain a fire that small for any length of time. Interesting project though!

 

[Blitzkrieg]

Another one of my plans was a gravity feed pellet fired rocket heater and I almost finished one but in the testing stage I couldn't get it to draft properly. I'm sure designed properly it would have worked by I complicated things trying to make a cross flow heat exchanger from the exhaust so that combustion air was taken from outside passing around the exhaust and pre heating it.

The real main reason for this whole project other than the pure fun of it is that my propane furnace is horrendously loud and wakes me up everytime it either kicks on or off. I have plans to mitigate that as well with a PWM voltage controller to dial back the fan speed so that it just blows hard enough to trip the sail switch.

In the end if all I can manage is a couple hours of fire with residual heat dropping off an hour or so later, I can set my propane heat to minimum and at least get a few hours of uninterrupted sleep without using any battery power or propane. I'll call that a win.

 

[begreen]

Another one of my plans was a gravity feed pellet fired rocket heater and I almost finished one but in the testing stage I couldn't get it to draft properly. I'm sure designed properly it would have worked by I complicated things trying to make a cross flow heat exchanger from the exhaust so that combustion air was taken from outside passing around the exhaust and pre heating it.

The real main reason for this whole project other than the pure fun of it is that my propane furnace is horrendously loud and wakes me up everytime it either kicks on or off. I have plans to mitigate that as well with a PWM voltage controller to dial back the fan speed so that it just blows hard enough to trip the sail switch.

In the end if all I can manage is a couple hours of fire with residual heat dropping off an hour or so later, I can set my propane heat to minimum and at least get a few hours of uninterrupted sleep without using any battery power or propane. I'll call that a win.

If this is an old Suburban Propane or Atwell heater then yes, they are noisy. The newer models are much quieter. The Suburban NT-16SEQ has a different blower system that is supposed to be very quiet.

FWIW I would not alter the airflow of the existing unit. It probably depends on a certain amount of airflow to keep the cabinet cool.

 

[Blitzkrieg]

You guessed it, suburban. The fan goes like a bat out of hell but part of that is probably because of my large battery bank anand solar array. My battery voltages are always sitting close to 12.7V (100%) and these furnaces are designed to work with one marine battery that might drop down to below 12 volts overnight. If I can dial back the voltage to the fan alone, as long as the sail switch activates it should be perfectly safe to run.

I've heard of some people bypassing the sail switch but then you're asking for trouble. If it doesn't flow enough air it will overheat.

 

[begreen]

I'd replace it with a new system. Maybe you could find one out of a wreck.

 

[Blitzkrieg]

The newer furnaces are extremely hard to find, they are incredibly expensive new and if you can find a used one they are treated like gold. I'll work with what I've got for now.

 

[Mech e]

I have plans to mitigate that as well with a PWM voltage controller to dial back the fan speed so that it just blows hard enough to trip the sail switch.

If you are going to do that, I would make sure there is a functioning high temp limit switch on the heat exchanger. I would not want to rely on an airflow switch to keep the unit from overheating.

 

[begreen]

The newer furnaces are extremely hard to find, they are incredibly expensive new and if you can find a used one they are treated like gold. I'll work with what I've got for now.

It's about $450 for the 19,000 btu furnace new.
Amazon product ASIN B00HSO2QL2

 

[Blitzkrieg]

There is probably already some other type of overheat kill circuit in there. I'm not talking about squeezing it down to 9 volts or anything, maybe 11.9-12. Anyway, if the stove works out well I may never need the propane heat while I'm sleeping in there. I can just set it to minimum while I'm away from camp to make sure the water lines (and more importantly the beer) doesn't freeze.

 

[Blitzkrieg]

Just a little update, I think the flue system is good to go now but I've started with modifying the baffle plate. My original design had a sharp downward slope to try and force smoke back down into the fire while lettingthe hotter gasses escape just before arriving at the door.

I'm going to try out a flat baffle plate with the same exhaust port size and see if it let's more of the heat out the flue with the same burn time. I'm also going to drill out my primary air manifolds to 1/4" from 3/16" since it always seems to be starving for air.

Last but not least I've ordered a piece of neoceram glass for the door which should make the testing process easier in the future. I'll share results when I test it again.

 

[Blitzkrieg]

In this pic you can see the secondary manifold in the top back with the two secondary burn tubes running above the fire brick on either side. The old baffle plate was bent up and over this manifold so that all of the holes were in the burn chamber. The new baffle will run on top of the side tubes and terminate below the holes in the secondary manifold.

I may have to plug those holes that will be above the manifold as I'm not sure how it will react. They could A) let fresh air into the flue effectively cooling it, B) mix fresh air with hot flue gasses causing them to burn in the flue, C) let smoke be pulled into the secondary system and sent back to the burn chamber, or D) anything else.

I think I'll run it once with the holes unaltered and see how it goes. The window is really gonna help with diagnosing the burn.

 

[moresnow]

One change at a time would be my recommendation. Good luck!

 

[Blitzkrieg]

Update!

I installed the glass in the door as well as the new baffle plate and I drilled out the bottom primary air manifold.

The window makes a huge difference, instead of adjusting by sound I can really see what's happening in there. The baffle plate has solved the smokeback on startup and the extra primary airflow makes fine tuning the flame so much easier.

I was able to test and finally see the secondary burn working, it almost looks like propane burners on the top sides of the burn chamber. I will have to cover those holes in the secondary manifold that are above the baffle plate. Its drawing fresh air into the flue which is cooling it down instead of heating it up. That should be a quick fix.

Here's some pics, you can sorta see the secondary combustion in the top right of the last pic.

 

[begreen]

Nice improvement.

 

[Seasoned Oak]

I would start by getting rid of the grate. It is a woodstove, not a fireplace. Then build smaller fires.

Good advice. modern wood stove manuals state DO NOT USE A GRATE .

 

[Blitzkrieg]

I've gone back and forth with and without the grate trying to see what works best. So far I've noticed that the fresh air flow is better with the grate installed since air can pass under the wood and get to the back but getting a new split to start on the coals is much more difficult since the hot coals fall below the grate.

I think I will keep the grate out from now on.

 

[Blitzkrieg]

The stove is running quite well with the current setup but I think it could be better. Tomorrow I will block off the secondary holes that are above the baffle plate and give the secondary a true test.

I also had an idea to try installing the baffle plate backwards in the stove, it should do the same job but should allow more hot gasses up the flue and draw more fresh air to the rear of the firebox. The only downsides would be possible smoke coming out the door and less heat on the top of the stove.

The only way to know is to test it out. I will let you guys know how it goes.

 

[SpaceBus]

Honestly for a home brew stove this is pretty impressive.

 

[Blitzkrieg]

I decidedto try something a little different today, were in the middle of a blizzard so I didn't feel like hauling the stove into the garage to weld up the manifold holes.

I made up a makeshift pellet basket to see what kind of burn time I can get on a load of pellets. If it works out I can burn cordwood during the day and load up the basket for all night heat

This is only a test basket and I don't expect it to last very long since it is thing gauge steel. So far so good, it took around 15 minutes to really get going then flue gas temp climbed to 600F with the door closed and primary air wide open. The last 45 minutes it has very slowly dropped from 600F to 510F.

 

[Blitzkrieg]

Honestly for a home brew stove this is pretty impressive.

Thanks SpaceBus! I really enjoy building things myself and trying to make them better when I can.