30nc auto draft

[realstihl]

This is the part that fits over the 3" inlet behind the stove that regulates the draft. Now all I need is linkage. It's just exhaust tubing with a butterfly.

 

[mellow]

So are you doing something similar to Dans smartstove?

(broken link removed to http://inveninc.com/SmartStoveForum/index.php?topic=75.0)

 

[BrotherBart]

Interesting to follow. I have wanted to try something like that for years but lack the fabrication skills.

 

[realstihl]

So are you doing something similar to Dans smartstove?

(broken link removed to http://inveninc.com/SmartStoveForum/index.php?topic=75.0)

Yes, it's similar but not smart. There are no electronics with my design. Just a simple bi-metallic coil on top of the stove. I've already posted the pics in another thread. I'll try to get them here.

 

[realstihl]

Here's the bi-metallic control pics.
.

 

[JA600L]

I like what I see. Good stuff. Where will the bimetallic control go?

 

[realstihl]

Here is the finished project excluding paint. I haven't decided whether to go with chain or solid linkage. It's been trial and error so far and hard to get it dialed in. I need to locate a spring handle if I decide to go with this.

 

[begreen]

Does the butterfly pivot smoothly enough to close when the chain is slack? If not it may need a weight or spring assist.

 

[realstihl]

It's very smooth. If you look closely towards the rear of the lever there is a counter weight.

 

[realstihl]

I thought I would give an update on the operation and settings. It hasn't really been too cold here to really test this thing out. Here's the way it works. From a cold start the lever needs to be at the 12 o'clock position. The draft fully open at this position. Start the fire as normal. Temps slowly climbs and ends about 400-450°. Draft is mostly closed at this point. This is kind of the sacrificial load since everything is just warming up. Once the temp is up it time to load stove with larger splits so the lever is pulled forward to about the 10 o'clock position. The draft will slowly close once temps approach 500-520°. I kind of weird to watch it go from primary to secondary burn automatically. Once the stove temp drops to around 300-350° it's time for a reload, draft is about half way open and the cycle repeats. It's not fully automatic, but is less time messing with the draft control. It seems to be very smooth as to the way it throttles back the primary air.

 

[realstihl]

Made a spring handle for it also.

 

[mol1jb]

This is really interesting. So is it the heat from the firebox make the mechanism work?

 

[realstihl]

Yes, it's directly related to the stove top temps. The hotter the stove top, the more the coil expands. The more the coil expands, the more the draft closes.

 

[JA600L]

So, if the system were to malfunction could the stove run away? I saw the counterweight on the butterfly. I'm just curious if you leave the primary on the stove wide open.

 

[realstihl]

So, if the system were to malfunction could the stove run away? I saw the counterweight on the butterfly. I'm just curious if you leave the primary on the stove wide open.

I suppose it could. There is still forward weight on the draft arm even with the counter weight so if the linkage or spring would happen to break the damper would fall to a closed position. I designed it that way. The draft rod is left wide open in front. Remember there is no modification to the stove that can't be reversed.

 

[blades]

When you get a little more run time on this , please report on your coal build up level. Great build by the way.

 

[realstihl]

When you get a little more run time on this , please report on your coal build up level. Great build by the way.

I do have some run time on it now and the coal build up seems to be no different than when using manual draft control. I do like the fact that as the stove cools, the draft opens to burn help down the coal bed. I am having a problem with air leakage somewhere because when the valve is closed there is still air leaking in somehow. I think maybe the in rushing air through the tubing is slightly opening the butterfly valve when the draft is high. This may be solved by going back to solid linkage. Other than that, it is working very well.

 

[stevemd]

I do have some run time on it now and the coal build up seems to be no different than when using manual draft control. I do like the fact that as the stove cools, the draft opens to burn help down the coal bed. I am having a problem with air leakage somewhere because when the valve is closed there is still air leaking in somehow. I think maybe the in rushing air through the tubing is slightly opening the butterfly valve when the draft is high. This may be solved by going back to solid linkage. Other than that, it is working very well.

If you can perfect this you can make a lot of money I would love to to have a automatic draft control that I can just bolt on

 

[realstihl]

Here's a new cover for the coil and lever.

 

[mol1jb]

That is for manual operation of the damper?

 

[realstihl]

That is for manual operation of the damper?

No, this adjusts the bi-metalic coil that is connected to the primary air. The further forward the lever is pulled the longer it takes to close.

 

[JA600L]

How is the secondary air adjusted on the nc30? If it is one control does that mean the butterfly adjusts them both proportionately?

 

[realstihl]

It's for primary air only.

 

[blades]

There is no control of the secondary air intake same with the air wash intakes- only the primary air has a damper-