bridging continued, eko

[bird hunter]

I can say I am not unhappy with the eko's performance, but bridging has been a big hurdle. After many hours following this forum I think it is the smaller units 25 and 40 that have the most trouble. I have changed fan speed, adjusted primary and secondary air flow, adjusted fan shutter and still have bridging. I was at 60% air speed and that wasn't enough during cold weather and seemed to blow alot of coals through the nozzle. Occasionaly a coal would plug the nozzle and fire would stop and give the dreaded fuel indicator. I now believe at this moment (subject to many modifications) that ash accumulation on the u shaped refractory blocks in the lower chamber are a big factor. I now run an 80% fan speed, doesn't plug nozzle and clean the u shaped goove every day and have no bridging issue, please note I am also splitting wood much smaller 3" to 4" .Any input would be welcome.

 

[Duetech]

Once I was able to "balance" my primaries externally I found that my secondaries were causing forceful over turbulence at the nozzle. I have had to drop my secondary air to around 1 1/2 turns out. (I observed blow holes in my flame that have mostly been removed with the smaller blower & secondary settings.) My primary air is down to about 6mm and will actually still produce enough fuel for a flame (though anemic) even when I turn the primaries off. I can now turn my blower shutter from wide open down to my current setting with little adjustment (open to close) to the primary and none to the secondary. The bridging is more prevalent and likely at wider blower shutter settings and fuel consumption is higher per burn with almost two hours less burn time at the widest setting. Larger splits that were rained on then subjected to the last deep freeze are more prone to bridge but I think the moisture was driven into the wood because it will burn fine if it is place on top of the load and gets a chance to dry some (it actually sweats if placed too close to the coals). I have also found the larger splits have less tendency to bridge if their length does not go over 18" and I can squeeze a 21" piece into the chamber. Most of my wood was cut at 20" and works fine as long as the coal bed is level and the splits are smaller (3-4"). I saw a video of a "40" in Europe that was using several counter spaced and recessed 10 mm holes per side (instead of the two 17-19? mm per side we have) for the secondary air and was producing a very uniform torch type blue flame. The maker of the modified refractory for the secondary air was trying to address the bridging/turbulence problem (claims to have fixed it) and the PM I got to go along with the video clip said that Orlan/EKO was supposed to retool their newer models to reflect the mods. (EKO sells bags of their refractory cement for those of us who like to tinker). All that being said I think we have a design encumbrance (plus all the other variables) that is causing us U.S. users more difficulty achieving optimum settings.
http://www.youtube.com/watch?v=EpbUUGYbv8M