According to Scott Rao, the best drum roasters are double-walled. The advantages are primarily a decrease in the risk of tipping, scorching, and facing. So this got me thinking of whether there might be a way to mod the Huky 500 to obtain these benefits.

I'm using the solid drum version with the supplied IR burner. This burner when turned up to higher gas levels seems like it has the capacity to overheat the single wall Huky drum due to the direct radiant heating of the drum.

So the idea I came up with was to create a heat shield to block the direct radiant heating from the burner using a perforated heat shield. I picked up some sheet aluminum from Home Depot and cut it with some shears with some tabs on the four corners. I also drilled a bunch of holes in it to allow airflow through it.



The heat shield clips onto the cross braces inside the Huky 500 and sits about a half inch from the drum, effectively making the roaster more like a double walled roaster. Here's a pic from underneath.



So far the results have been favorable. When roasting I don't have to worry so much about about tipping and scorching as heat is applied more with convection using increased airflow. The heat shield also seems to moderate the roast and makes the roaster respond fairly gently to changes in temperature and airflow. Tonight I roasted some natural process coffee and got the following profile.

It's a great idea. I'm working on a similar approach to my 1 kilo Ambex clone for the exact same reasons. In some form, you're effectively making your roaster act like a Diedrich roaster.

I wonder how much impact adding the grate that comes with the perforated drum would have on the solid drum...

SJM wrote:So essentially it looks like you've encased your solid drum in a perforated drum? Does it go all the way around or does it just cover the bottom like the grate that comes with the perforated drum?

I wonder how much impact adding the grate that comes with the perforated drum would have on the solid drum...

The perforated shield just covers the bottom of the drum and protects it from the direct radiant heat from the burner. It really doesn't need to cover the entire drum. So yes, it's like the perforated drum grate.

This makes it a lot easier to ensure that the drum temp is not getting too hot. The hottest part of the roaster now is the top (heat rises) where the the ET probe is located. So if I keep that temp say around 460F then I can be sure the drum isn't too hot. But without the shield the drum can actually get a lot hotter than the ET probe temp due to the direct radiant heat hitting the drum surface.

The nice thing about it is that it just hangs on the cross braces with the tabs I created and is easily removable. No messing with the roaster is required.

I really do like your simple but effective solution. But I do question the reason for doing it. I have a similar setup of the Huky (solid/IR/72rpm/...) and I have not had any problems with scorching/tipping in my now one year (say 200 roasts) of roasting with that setup. That may be due to me being quite gentle with my charge temps, as the starting directions seems very high (maybe recommeded for a perf. drum). For a full (500g) I start at 240C and only 140C for a 200grams load. I dont use any heat for the first minute, but have my roaster coast down to the loading temp I'm looking for.
The parts for remaking the Huky to a perforated drum roaster is airborne at the moment, so hopefully I can make some tests of a similar setup to yours (with the original Huky grate that is) as I soon will have both drums to play with.

This diffuser is similar to what I had Mr. Li rig up for me way back in the early adoption time of the Huky.

It was basically a double-louver setup where one set was fixed and the other was actuated via the standard movable louver capability of the Huky. The theory behind it was to act a bit more like a heat exchanger, producing more convective heat over conductive/radiative heat. But since my particular setup was atmospheric (BlueStar Range) rather than with radiative-IR burners, I felt the feature went to waste. That said, folks with IR heat sources (i.e. most Huky users) may see benefits with this or a similar setup.

Louvers are closed in photo below:

slickrock wrote:This diffuser is similar to what I had Mr. Li rig up for me way back in the early adoption time the Huky.

Very cool! That's exactly what I was aiming to do - increase convective heat and decrease conductive heat. So I guess I just reinvented the wheel, but at least I was on the right track. Thanks for the link.