here is a thought for a cleaning rod/brush
take a length of speedo cable, and carefully untwist a couple inches
then bend in the sharp ends and rewrap it back again, the result should look like a barrelled out end
that tapers back at the end,,
i would think that this might work without damage to the tubes and be fairly easy to clean as well.
cheap too if you have a section of old speedo cable laying around, even the new cable core kits are pretty cheap
fwiw, truck speedo and tach cables are larger in diameter than pickup and car cables, but iirc they will still fit down the inside
of a quarter inch tube just fine.
one might even use a variable speed drill to spin the cable a bit to further scrub the innards of a tube,
just a thought.
also for those that might be interested i have a design and built one to fit my changfa 195 that so far after maybe 25 hours
of mixed fuels use has proven to be self cleaning, it manages to drop the exhaust temps from 640F input to 225F ouput
which scavenges most of the available heat without condensing for the most part. it self cleans at each cold start up on its own.
i have been considering drawing up the plans, theory of operation, a bill of materials and offer it for a modest cost to cover
the expense of producing the document, maybe 10 bucks or so, maybe a bit more depending on costs to produce.
it can be scaled to any engine size, and the materials are commonly available stuff, the skills required to assemble are modest,
requireing a bit of welding but not much, certainly something a 120volt mig from harbor freight would handle just fine.
it also does a very good job lowering the db level as well, and
in preliminary tests my fuel consumption per kwatt/hr produced decreased ~3% under that of the original changfa muffler
(can't say if that is because it is so good, or if the oem changfa muffler is restrictive)
to my knowlege there is no other exchanger that works on this principle, the one i built is approx 36" long and was built for less than
75bucks in about an hour.
if there is sufficient interest i will put together an info kit on the exchanger and offer it to the group.
i guess it will come down to whether one can make a compromise of not being able to get the last few btu's with the ability to
not have to clean the thing as being worthwhile. according to my calc's it is approx 75% efficient at harvesting the available heat
from the 195 changfa exhaust, the numbers were checked by a thermal engineer.
