My second BT probe ...

[beananimal]

I tried some different configuration of the probes and now the results seem to become plausible again. The problem is really the 17mm tip: the metal piece obviously has not a good contact to the cable tip.

I had a roast with the plain cable probe (of the killed 17mm tip) installed in the exhaust. The behaviour is similar with what I know from the past with similar probes. The crossing point BT <> Exhaust is around 190°C and the shown exhaust temperature is limited around 200°C.

The second roast was with an original Huky TC which is just 15mm inserted on offset-BT position. In both cases the thread for fixing is "imitated" with teflon tape.
It follows the normal BT much better, but still is a bit behind.
In the near future I will try to get this probe another 5 - 10 mm deeper into the beans and will check with a contact thermocouple if the frontplate much be somehow colder than in the middle of the drum.

Then I made a 80g sample roast. The plot shows that the offset-BT might be less good for normal roast sizes, but it gives quit good information at that small size, while the normal BT is not really showing bean temperature.

I will upload photos and plots later today after some sorting.
(My old roasting notebook is not protected and connected to the outer work. )

[beananimal]

Here are the photos and plots to explain the different test configuration of the probes and the results.

First confirguration, already with the MET from inside-out installed, so that the hex-flange was inside the Huky, and could not cool the probe. With this MET followed not only until 160° but until 180°C. (red line) But still not useful.


333g Colombia decaf

BT: original Huky TC
MET: 10mm
Exhaust: 10mm
BT-40mm-offset: 17mm



++++++++++++++

Next I made a second roast with the plain cable probe installed in the exhaust (from the killed 17mm tip) . The behaviour is similar with what I know from the past with similar probes. The crossing point BT <> Exhaust is around 190°C and the shown exhaust temperature is limited around 200°C. (purple line)
I believe this plain probe in the exhaust is a good reference point.



333g Sumatra

BT: original Huky TC
MET: 10mm
Exhaust: plain tip
BT-40mm-offset: 17mm





Here the picture to see the probe location and the teflon tape for adapting the diameter





Just to mention that the additional BT-offset is 40mm to the left, but on the same height as the center / axis of the drum, that is higher than the original BT.

+++++++++

The third roast was with an original Huky TC which is just 15mm inserted on BT-mod position (40mm offset) in both cases the thread for fixing is "imitated" with teflon tape.
It follows the normal BT much better, but still is a bit behind.
Maybe the area close to the frontplate is really a little bit less hot than the center of the Huky.

BT: original Huky TC
MET: original Huky TC
Exhaust: plain tip
BT-40mm-offset: original 70mm Huky TC, but only 15mm inserted


Honduras 333g








+++++++++++++++++++++++++++++++++++++++++++

Then I made a 80g sample roast. The plot shows that the offset-BT might be less good for normal roast sizes, but it gives quit good information at that small size, while the normal BT is not really showing bean temperature.
This version should be pretty good for a sample roaster. Again to mention that the TC is at the height of the axis, also for this 80g batch. A little bit lower could be even better for this batch size.

To note that for this very small batch I reduced the drum speed to 48rpm (although using the solid drum for all these roasts) by adjusting the voltage from 24V to 16V to have the beans less in the air.  ( I forgot to give more power after turning point.  It was only ~0.8 kPA gas for the first 4 minutes. Should have been about 1.5kPa starting latest at 2 minutes acc. to my plan)


80g Colombia

BT: original Huky TC
MET: original Huky TC
Exhaust: plain tip
BT-40mm-offset: original 70mm Huky TC, but only 15mm inserted





It is interesting to see that the 80g green beans fill almost the full window.
They are focused close to the frontplate running left side uphill. The brown beans even fill the full window.
Last picture: ~70g of beans are not much to fill a roaster.
(edit: several small correcctions)

[beananimal]

Now it is visible why the 17mm probe is so sluggish. I wanted to modify it to make it faster.





I used a file to open the tip from two sides. The idea was to have the plain probe tip in the beans, but protected by a remaining frame.
But there is no tip. At least almost no tip.    The tip ends at about 4-5mm inside the hex-flange, which is nearly in the wall but not in the beans.
I am curious on the answer of the manufacturer

[edtbjon]

Now it is visible why the 17mm probe is so sluggish. I wanted to modify it to make it faster.

We don't need duplicate pictures.

I used a file to open the tip from two sides. The idea was to have the plain probe tip in the beans, but protected by a remaining frame.
But there is no tip. At least almost no tip.    The tip ends at about 4-5mm inside the hex-flange, which is nearly in the wall but not in the beans.
I am curious on the answer of the manufacturer

That explains a lot. I'm curious too about what the manufacturer have to say. I will most probably send the TC's back, as I don't think they are even close to what is described or at least what I expected.

[beananimal]

Today, 8:30 I had a sorry-email asking how many replacements I need

(Anyway, it cost me some nerves the last days) 

[beananimal]

I received replacements for all my probes from Sensorshop24.
Today it was the first chance for me to roast with the new TCs.

I am absolutely annoyed. It is really the same behaviour.   
Shown temperature increase is max ~10°C per minute. Max value of exhaust shown is 140°C.

For sure I will open also a new TC and check for reasons, but I will not do it now, as my time and my energy is currently very limited.
For the next days or weeks I'll go for some tasks with a more possitive prognose for the results.

[edtbjon]

I received replacements for all my probes from Sensorshop24.
Today it was the first chance for me to roast with the new TCs.

I am absolutely annoyed. It is really the same behaviour.   
Shown temperature increase is max ~10°C per minute. Max value of exhaust shown is 140°C.

For sure I will open also a new TC and check for reasons, but I will not do it now, as my time and my energy is currently very limited.
For the next days or weeks I'll go for some tasks with a more possitive prognose for the results.

Yes, I did a couple of roasts a few hours ago with the new TCs which had exactly the same behaviour as the old ones. I do have some other TCs (chinese) which I will test, once I get hold of the proper nuts to bolt it onto the front plate... (The package says M6, but it's probably some UNC equivivialent.)
On the other hand, my bent BT TC does work well, it's just a matter of some fine adjustment, so that it doesn't push the door open when the beans push between the TC and the door... (I just turned my head and all of a sudden there were hot beans all over the floor.  )