So after buying a used M3 and roasting a couple times with the stock thermometer, I decided to do a full tear-down of my M3. Inside all looked relatively good, and unless the previous owner cleaned the inside perfectly, it looks like it's only seen a half dozen roasts before me or so. But I made a bit of a mistake not having the filter on the air intake properly when doing my first roast, and I wanted to season the drum, and not knowing the condition of the internals...I decided a good cleaning should be in order before getting too far into learning my M3.

So after reading around a bit, I had determined that I either wanted to paint my drum, or season it with oil. For the first round and because removing the drum was pretty easy for me...I decided to go with oil seasoning. Pretty basic technique, just wipe on some vegetable oil (I used flaxseed since I had it on hand, but any kind of high-temp oil I think would be just fine...even olive oil would probably work fine since really you're just looking to get it charred), and bake at 500F for a 5-10m (I put in a cold oven and let it heat up). Then do that again with only a minor cooling in between. So basically just 2 coats. Here's what I ended up with:



I was thinking about roasting it over a propane burner to charr it even more, but I think just roasting a few batches will do that itself, so I didn't bother. I'll check it again after 5 or so roasts and update this thread.



My second mod was based on what a hassle it was to not only get to the re-circulating fan, but the set screw on the fan shaft stripped out, so I was unable to actually remove the fan totally. Anyway, my momma always told me "an ounce of prevention is worth a pound of cure" (or I probably read it on the internet), so I decided to go with a mod that covers the fan with a filter.

I used a 75 micron paint straining filter, also used for making bio diesel, or filtering any kind of liquid. I used for making rootbeer, but no longer use it so I decided it made a great filter. It's very strong, and breathes easily.



Cut to size



Installed, to do this I stretched the filter a bit, and punched holes carefully where the screws would go. It's not quite drum tight, but I didn't want it to get sucked into the fan over time.



I'll try to post an update to this thread once I've used these mods for a bit, to see how well they break in, but thought I would post up front in case I lose these images or something.

If that filter method works, it would be very cool. But I'd fear it would greatly restrict the flow of an already anemic fan.

I'll be sure to report back. Under a dry-run, it puts out roughly the same feeling to the hand...I know, very scientific approach. My other scientific selection method was to put my mouth up to the filter and see how much force it required to breath...for me it was breathing almost as normal.

I have also made a guess that I'd likely have to clear off the filter after each roast, hopefully it doesn't clog up so fast during a roast that airflow suffers...only one way to find out anyhow.

EspressoForge wrote:...I have also made a guess that I'd likely have to clear off the filter after each roast, hopefully it doesn't clog up so fast during a roast that airflow suffers...only one way to find out anyhow.

That's the problem I foresee. It will likely clog up quickly and greatly reduce your airflow when you need it most. I imagine it will end up looking like the tip of a cigarette filter.

I could not get the tiny hex screw that holds the fan fins in place loose, ended up rounding it.

However it is still possible to soak the partial fan assembly by first removing the motor frame/ stator? from the rotor which is connected to the fins / fan housing. Remove the 2 screws on the bell end cap and it will come out easily.

Using espresso machine cleaner (backwash powder) hot water in a small ice cream tub, holding the assembly by the rotor, gradually make the water level high enough so that it sits just under the bottom (now top) of the fin housing and leave it it soak for 10mins.

The fins come out clean as a whistle and the process softens the crud just above the water line enough to give it a wipe clean and tidy up with alcohol swabs and a straightened paper clip.

I made sure it was all clean and dry for a day before putting back together, lubing the end bearings with machine oil.

Fan works to well now.

Also I agree with Tom, the filter idea seems good, but I think its going to clog very quick and you are going to end with very little air flow.

EspressoForge wrote: So after reading around a bit, I had determined that I either wanted to paint my drum, or season it with oil. For the first round and because removing the drum was pretty easy for me...I decided to go with oil seasoning.

Good decision to go with seasoning. Most heat resistant paints are enamel, which have a lower emissivity typically than dull stainless alone. True oil paints have higher emissivity, but those are harder to find in heat-resistant form. With seasoning you are, after all, using oil to begin with.

OldmatefromOZ wrote:I could not get the tiny hex screw that holds the fan fins in place loose, ended up rounding it.

However it is still possible to soak the partial fan assembly by first removing the motor frame/ stator? from the rotor which is connected to the fins / fan housing. Remove the 2 screws on the bell end cap and it will come out easily.

Using espresso machine cleaner (backwash powder) hot water in a small ice cream tub, holding the assembly by the rotor, gradually make the water level high enough so that it sits just under the bottom (now top) of the fin housing and leave it it soak for 10mins.

The fins come out clean as a whistle and the process softens the crud just above the water line enough to give it a wipe clean and tidy up with alcohol swabs and a straightened paper clip.

I made sure it was all clean and dry for a day before putting back together, lubing the end bearings with machine oil.

Fan works to well now.

Also I agree with Tom, the filter idea seems good, but I think its going to clog very quick and you are going to end with very little air flow.

I spun a 1/16" wrench in my set screw too, I probably should have tried using a heatgun first, but maybe next break-down to check the filter I'll try that out. Even still I would prefer the filter method. I'm hoping the screen at the top helps as a pre-filter enough so that the lower filter doesn't get clogged. My next idea is to try something like this (more like a fabric that I've seen doesn't clog as quickly):
http://www.frozencpu.com/products/16607 ... Thick.html

Getting the density vs filtration right for the fan should be the trick, but I don't see why in principle it wouldn't work, at least for a while.

slickrock wrote:Good decision to go with seasoning. Most heat resistant paints are enamel, which have a lower emissivity typically than dull stainless alone. True oil paints have higher emissivity, but those are harder to find in heat-resistant form. With seasoning you are, after all, using oil to begin with.

Yeah, mostly I didn't like the idea of paint since the whole thing is stainless steel and I'd prefer to keep it that way, but also partly I didn't want to get the wrong kind and have to scrape it off and try again, not to mention roasts possibly tainted or ruined.

I'm sure some types of oil have the chance to mess with flavors in roasts (at least for the first few), and the argument could probably be said that some types of paint may be less reactive than oils...in the end the oil seemed less risk to me.

I had also assumed that oil may not be as efficient as a paint would be, and would be happy with 50-80% of what people report the paint to do. If it's even better...then great!

The CPU fan filters look like an interesting avenue to pursue, let us know when you test it out.

If you still want to try the paint at some stage, the type you want is 100% silicone based pot / kettle stove paint, mine is recommended for temps up to 540°C.

I wonder how well this would work. It's toxic because it's acid, but if it etches and leaves a dark surface after cleaning, the acidity can obviously be neutralized.

http://www.caswellplating.com/metal-fin ... fl-oz.html

I still have no issues with mine being painted. It's temp safe to 1200°F and there's clear evidence of it conducting heat into the drum better than left untreated.