question for i-roasters

[ivdp]

As a distributor of the I-Roast, I have sold since the middle of December around 100 I-Roasts to several countries in Europe.
Some 4 to 5 machines were faulty and have been replaced.
A lot of questions on roasting and temperature readings have been asked initially. Now it is much quieter and it seems as if people are more relaxed, try a bit more before asking.
A am noticing that some machines will roast in 7 to 8 minutes, whereas an other category will need 9 to 10 minutes on the Presets. Individual settings are different of course.

I have not yet determined what the course could be on this difference. It could be machine settings but also amount of beans used, ambient temperatures, voltage, dimming devices in the circuit.

I believe that I can say that the very vaste majority of the users are very satisfied.



--
Ivo van der Putten


www.ongebrand.nl

[wang]

Gouerezi - the increase in bouncing and moving about after five minutes is due to the fact that the beans lose water, expand and become less dense. You can notice this easily after the roast where the roasted beans will take up more space than green beans, but yet are lighter by 10-20%.

This increase in volume and decrease in weight allows the semi-roasted beans to be pushed around the chamber easier than the unroasted ones as they've more surface area for the fan to push against and are lighter. I'm afraid the dooser at work is actually the roast process

[Gouezeri]

Wang,
I was actually taking this into account (along with the doosers). I very much doubt, considering the noise that the machine makes that you would be able to hear a difference in fan speed (other than the cooling stage which serves to drop the bean temp a good 160C in less than a minute). However, the difference in movement is much more dramatic than just a decrease in mass. This can be observed by using lower temperatures (as hearthware suggests) which are reached quicker, long before the beans have lost much mass at all.
Ivo, the variation in results you have seen, do you know if these people adjusted the chaff ring at all? Depending on the amount of chaff (both in the ring and in particular on the wire mesh), I have seen a difference of 2 minutes in roast time, leaving all other variables the same. This is most probably the cause of most variance.
Dom

[ackers]

I saw a cartoon once of marching men and a little boy saying to his Mum 'look Mum they are all out of step except our Jim', I feel a bit like Jim at the moment but I will persevere for a bit longer. As suggested by Hearthware I checked the resister and it is a 1K, I changed this for a 4k7 and tried the preset 2 profile using the last of my Sumatra Mandheling. The onboard thermometer quickly ramped up to 225-230 with the fan on slow speed, after 30 seconds the fan then started to pulse into fast mode (same speed as cooling cycle) using 2 second burst, this maintained the temp for the next 6 mins and then the temp dropped to 215 for 4 mins and then increased to 230. All this time the fan pulsed on and off in 2 second burst. All times and temperatures are approx because I was not geared up for a proper scientific run. You will have noticed that these times and temperatures match the profile. The only problem is that the roast is far too light, I have gone from one extreme to the other. Tomorrow I will fit a 2k2 resistor and see what happens. Ackers.

[AlanP]

For what it's worth this may or may not have some bearing on your problem

(Bottom of the page)
Quick Alteration to Chaff Collector for iRoasts that are running too dark
http://www.sweetmarias.com/hearthware.i ... sheet.html

[Gouezeri]

Alan P,
From previous conversations with Alan "Ackers" he has done this mod.
Ackers,
Glad to hear that your results are getting closer to what you are looking for/would expect. I've read of the "pulsing fan" but never experienced it myself (quite possible that my temps are simply higher). If I can, I'll try and get into Maplin on Tott. Court Road in London and get some resistors as well and try them here. At the moment I've been using a sample weight of 140g and a profile of 204/2 232/3 242/1 with some "La Manuela" and I've been measuring the temp with my new DMM and thermocouple. So far I am getting approximate "bean temps" in the right region, but the onboard temp displayed is not what would be expected. Thanks for sharing your "experiments" I'll try and look into this as well and maybe the pair of us will start walking in step!
Dom

[ivdp]

Rubber ring modifications.
I am, after hearing Hearthware, advising against rubber ring modifications.
Stress on the lid when the heat increases might damage parts.

I do strongly emphasize that the upper lid must be cleaned of chaff after every roast.

It is obvious that when you are able to keep the upper lid free of chaff, you influence the rpasting results. More air escapes (=heat) and the machine will need more time to reachthe same roasting colour.

I do not have the impression that my clients are modfiying their machines.

Ivo

[Gouezeri]

Ivo,
It is not so much a matter of modifying the rubber ring, as maintaining the chaff ring in contact with the chaff collector and there are various different techniques for this (without touching the rubber gasket). If the chaff ring can move within the lid then it is too loose and chaff (depending on bean type of course) is likely to block the fine mesh on the top and this has a major effect on profiles (ie. the roasts they produced were undrinkable with my unit, there was lots of smoke and way too much oil from a "light" profile). Chaff in the chaff collector is to be expected of course. Though, as you rightly state, it must be cleaned out after each roast.
It seems that HW is aware of this problem and have communicated possible "fixes" to Tom at SM. It is also possible that not everybody has this issue, but I've not looked at enough I-Roasts to judge this for myself.
For anybody reading this who has not seen it for themselves, we are far from the realms of PIDs and Pressure mods (or wooden mallets!) but in essence, it is about creating reliable, repeatable and comparable results.
Thanks for relating your experience Ivo
Dom

[ackers]

Got it at last. I fitted a 2k2 resistor and tried profile 2 again using Brazil espresso perfeito blend, I was taking temp readings every 20 seconds and it was controlling perfectly then I hit the cool button by mistake and that was that. I then tried a profile that Dom had used with these beans of 176/3 220/3 240/4. For the 1st minute the temp seemed a bit high at 194 but the fan started to pulse into high speed and kept the temp fairly stable at 204, when the fan kicks into high it drops the measured temp down by about 15 deg. After 3 mins the fan stayed in low speed and the temp increased to 225/227 and then the fan started pulsing again for the next 3 mins and kept the temp at 227, the temp increased to 244 for the last 4 mins and I stopped the roast with 10 seconds on the clock. Now I can start to play. Ackers

[Gouezeri]

Excellent news Ackers,
I'm glad things are finally progressing as you would like. I've not had the chance to look into changing resistors yet, but I hope to test that soon (possibly today). What I will say, however, is that the onboard temp is not necessarily a fair judge of the bean temp. Remember the on-board temp displayed is somewhere directly in the hot air column, so it will be affected by changes in air speed. This is why I've been playing with a thermocouple taking measurements in the middle of the pot, deep in the beans which so far has shown that the beans are reaching the profile temps. Once we're getting stable results, I'll try measuring again with the smoke vent in place to see what kind of a difference this makes.
Dom

[ackers]

The main thing for me is that I can now see variations in the temperature and it follows a programmed change (both increase and decrease). It is now doing what I expected it to do. I realise that one mans temperature is another mans burnt bean but as I have said, I can now start burning and it will be my fault and not the machines. Just a quick word on the chaff collector, I followed a suggested mod on SM which involved moving the countersunk screws to the non countersunk holes under the rubber sealing ring, this worked and it did take out the slack in the chaff collector, but it losened the way the top part fastened to the roasting pot and it used to vibrate loose during roasting, I put the screws back to original and I now use a set of brass shims on top of the collector. Ackers