Lopi Freedom Air Modification

[TradEddie]

When cleaning the slider air control on my Lopi Freedom, I decided to learn what I could about how the air control works, and to see if I could find a way to override the minimum air control.
Firstly, the air control consists of two sliding plates, each with a rectangular hole, pushed up with springs against matching inlet holes on the underside of the stove. What I noticed first was that contrary to my original thought, the relative proportion of each air supply does not change with slider position. There is a triangular hole on the primary air inlet, but the matching hole on the slider is rectangular and smaller than the triangle, so the resulting opening will always be a rectangle.
My second surprise was the relative size of the holes, the inlet for the primary air (doghouse and air wash) is about 1x2.5", while the secondary inlet is about 3x6". This does not necessarily correspond to much higher airflow since there may be more restrictions in the secondary piping, but I was not expecting this large a difference.
The slider has two separate plates which can easily be removed and for those interested in "tuning" their stove, these plates could easily be fabricated to give a custom air mix.
The full closed position is limited by two bolts which stop the slider moving any further, leaving an extra 3/8" of travel possible if the bolts are removed before the slider will stop against the end of the housing. Using an insence stick, it was very easy to confirm that removing the bolts allowed complete closure of the air supply (see pics).
I am interested in completely closing the air supply for two reasons, in case of an overfire or chimney fire, but mostly to eliminate the significant downdraft I experience when the stove is not in use, which is 5 days a week in Winter, and all through the rest of the year. I didn't want to lose the current stop position, but wanted an easy way to override if necessary.

Comments, thoughts, suggestions. Pictures to follow.

TE

 

[TradEddie]

First, the problem. Cold air coming into the house when the insert is not running. If I'd found a leak this big when airsealing I'd have been overjoyed.
You can also see the hole for the stop bolt in these pictures.

 

[TradEddie]

Now the solution. One on each side.
To close the air fully, simply lift the slider handle slightly. Obviously I still need to file the bracket slightly, but it's in field trials as I type.

 

[TradEddie]

Update after a few burns, the fix works well, no issues accidentally closing the air fully, and no problems lifting the plate to get to the full closed position. Before the modification, the metal at the intake was ~50F and the stovetop was mid 60s with 30s outside. With the fix in place, all metal is about 70, same as any other surfaces in the room. I expect that the summer smoky downdraft smell will be addressed too. The fix stays.
TE

 

[jcjohnston]

Man how I get a kick out of running into guys more anal then me on this site. This solves a problem that has bugged me since I got this stove, thank you Tradeddie

 

[TradEddie]

I had given up on a simple solution, I had resigned myself to just removing the stop bolts at the end of the season but then I was working on something else entirely when I saw this old baby gate bracket lying on my workbench and it was a eureka moment. The holes and one bend were already there, two cuts with the hacksaw, bend in the vise, hit with a hammer, quick bit of filing and it was done. I suppose there is the possibility of warping the plate by raising it slightly, but that wouldn't affect the operation of the spring loaded top plate anyway.

TE

 

[TradEddie]

One more update; classic spring "smoky smell" conditions here over the last few days, and with the modification in place, not a whiff of smoke. This could also have been helped by adding a block-off plate last fall, and properly sealing the top plate. I'm 100% satisfied with the results.

TE