Post By DesigningByCoffee
Corretto Paddle Extender
I've been doing some larger batch sizes (700g green) and have been getting some great results.
But as I've been playing with probe placement to get an accurate reading, I've noticed that lower down in the bean mass with larger batch sizes, the mass temp reads 7-8° lower than I'd expect. This had me slightly concerned about evenness of the roast.
This was further heightened by the fact that at the very end of the roast, by the time the beans have expanded, there is very little mixing happening in the top layer of bean, where it had been mixing fine at the beginning of the roast when they are small.
I'd also noticed a 'fuzziness' in the start/end of first crack / second crack, making me suspicious that the beans on top of the mass are coming on sooner, especially at the tail end of the roast, with the lower regions taking longer - maybe not even reaching second crack when dumped.
Anyway, long story short - made a paddle extender! Included a photo of it installed, plus the template used to make it (kinda like a one legged Marge Simpson gingerbread man with a sore hand!). Works an absolute treat! Full pan mixing right to the end of the roast, with a much more defined first crack & second crack (ie louder, harder - all beans going at once). In fact it was almost too effective with the mixing - I've had to further mod my lid & pan as I lost some beans over the top! So I've trimmed little bit off the extender now too…
But well worth it so far - should make for a much more consistent roast :-)
It's one of the things I'm worried about with mine. What was your original paddle shape? Great fix but damn that template looks ugly haha! Function over form :P
You need to be a bit careful mate that you don't overdo the size of the paddle extension. Too much and the motor will be overloaded so it might pay to keep an eye on motor temperature, or any obvious signs of stress in the motor/gearbox region.
All you need to do really, is just alter the pitch of the existing blade(s) if that is possible, so that beans are being lifted as well stirred. This will ensure that operating stresses are kept below that which will possibly cause early motor failure.
I also extended my paddle so I no longer had to stir with a wooden spoon towards the end of the roast,
I just riveted a thin strip of metal to the original paddle and it works well.
Did another batch last night - worked superbly!
Required a few more mods. Trimmed the extender down as mentioned, had to raise the lip on my 'inlet splitter' and then also had some camping toaster mesh that I got from BCF that I used to cover the inlet - the first batch my splitter filled up towards the end! So now that whole inlet section is relatively 'sealed' from bean ingestion
But very happy with the evenness & consistency now of the roasts…
Interesting reading here Matt. I did an 800g roast the other night for the first time. (I've been doing 600g up till then). I noticed all the things you did, possibly to further extreme in relation to temp. My FC started at just over 180 deg. I wasn't expecting it till 205. Prior to that however around 140-160 my ROR plummeted. I already had the HG on high fan and high heat so I couldn't do anything about it. When I got FC at 180 I started to get concerned that the beans on the top were actually at 200 or thereabouts and I just wasn't getting enough agitation. FC was carrying right through till my probe read about 210. I think by then the beans were mixing quite well because SC was quite pronounced, certainly moreso than FC which was quite spread out. The result was actually surprisingly good. Just received a message from one of my friends currently drinking it on plunger, commenting that it's just as good as my normal 600g roast.
Without a paddle mod though, I don't think I'll persist with 800g batches. Just didn't have enough control with the HG running on full from very early on.
Yep - the paddle sorts out the mixing unevenness but I had to drill a second probe hole 20mm higher in the pan to even out the temp readings, but once done I was back to 202 and 222 on the knocker
800g is useful though - 2x 250g bags for passing on or selling and 120g for QA. I also found that larger roasts need longer times - so maybe your HG won’t need to be on full?
BTW that was a concept paddle. Later ones were simply shaped sheet aluminium pop riveted to the paddle.
That is actually a very good point. I was thrown off by the template profile which I did with a 600g roast. It has only just now occurred to me that I was flogging a dead horse trying to match that profile. I don’t know why I didn’t realise that at the time.
Yep. Lots of trial and error proved to me that to get a similar flavour in the corretto with larger batches I had to extend my roasts 3-4 minutes. I think the more 'focussed' heat source (from one corner of the lid, although my splitter helped a lot in this area) means that to get heat into a larger bean mass works better if you just take a little longer and go a little slower. Just a roaster dynamic quirk - I doubt commercial drums work the same way.
Let the taste be your guide!