UliD wrote: The airflow in the Quest is a mystery to me. With an old, unmodified Quest the air was probably mostly sucked up at the front of the roaster. I think TomC posted a drawing of the airflow somewhere.
Now if you drill holes in the front, will not a big part of the air take the direct (if somewhat narrow) way up the frontplate instead of going round the back?

Air (like water) takes the path of least resistance.

If you think of the pressure gradient (caused by the fan) as potential energy, and the air path as the resistance - the airflow increases as the resistance to it decreases. (this is the pneumatic equivalent of the hydraulic effect of a gicleur - you have a potential difference of pressure across the gicleur - and the maximum flow is determined by that pressure gradient and orifice area).

So then - look at the shortened drum - the gap in the front - as you pointed out - still exists - but it is a narrow path (high resistance). The holes at the back (or the grill) is low resistance - so most of the air will be pulled in from the back. That will be a mix of cold air from the rear vent - and hot air from the heaters and the top.

What I proposed was that closing the back hole and drilling a few holes in the front (the area between the inner and outer drum) will result in air flowing around the heaters. I don't really like the mod idea because it is irreversible. I am now thinking of drilling holes in the front 1st inch of the outer drum (just like I drilled holes in the inner drum) and shortening the lagging by an inch. Maybe just at the bottom of the drum - forcing air around the heaters.

AssafL wrote:Air (like water) takes the path of least resistance.
What I proposed was that closing the back hole and drilling a few holes in the front (the area between the inner and outer drum) will result in air flowing around the heaters. I don't really like the mod idea because it is irreversible. I am now thinking of drilling holes in the front 1st inch of the outer drum (just like I drilled holes in the inner drum) and shortening the lagging by an inch. Maybe just at the bottom of the drum - forcing air around the heaters.

Hmm, out of curiosity, would this have significant advantages over the copper tube setup?

goducks wrote:Stephen, just got M3s and the handles I have seen on this post that you do are amazing. Is it possible to contact you about these?

Regards,

Goducks

Send me a PM and I will give you what I am currently doing with handles. The Trier is the only one necessary to operate the roaster easily and really the only one necessary.

TomC wrote:I slide the copper pipe right out for periodic cleaning.

+1 Yep, just slide it out and slide in the vacuum nozzle (when roaster is off and cold).

rbk wrote:Hmm, out of curiosity, would this have significant advantages over the copper tube setup?

Probably no. My folded brass tube is just a pain to remove. I guess it is time for a real tube.

Thanks guys for the responses! I will make the tube more easily removable then.

I removed the copper tube and did a roast just to see if it makes a big difference. It does, especially obvious during the warm up phase. There are more minor fluctuation (wavy waveform) in the MET line in general. Presumably that indicates it's more sensitive to air draft around the roaster without the copper tube.

Without the tube mod, the MET climbs up much faster, and BT follows (more heat transferred via a hotter drum - conduction-heavy?). When the wattage is dropped (650 watt), the one without copper tube drops much faster and lower in both MET & BT. Don't know what this mean exactly though (more heat loss??).

Note : all preheat/warm up was done by 1000 watt & fan 4-5. Once BT reaches 200C(392F), the wattage is decreased to 650-700 watt.



The next two graphs are warm up sessions (all with copper tube) from different roast sessions to show the roaster's repeatability. Tracks pretty closely to each other.

Awesome. Thank you for proving the hypothesis.

Not sure how many of you are using the TC4 Hardware PID, but I'm curious what you've found to be good settings. I feel like the settings I have are pretty good but I'm always looking to improve.

Also, I recently did the fan mod (resistor clip), huge difference!!! However I'm having a hard figuring out a good workflow now without killing my ROR' I didn't have that problem before. Any suggestions?

I am using:

#define PRO 2 // initial proportional parameter (for high heat mass - low PRO to minimize over shoot
#define INT 10 // initial integral parameter - not sure
#define DER 0.5 // initial derivative parameter - react quickly to rate due to high thermal mass and slow response

1. It oscillates.
2. It is rather slow to react.
3. It can't predict changes due to airflow, reaching 1stC, etc.

Hence, I don't use it to roast. I only ever use it to heat up the roaster (while I prep the coffee batches, cooler, etc.) without demanding attention. Once the roaster is hot I can then switch to proportional %heat controls.

@AssaFL, you lost me....are you modifying the user.h file or are you setting the PID in the Control box within Artisan?