Really needed a destoner for the roastery, hand sorting 10kg of beans at a time is a laborious task  Trouble with destoners is that they are a sizeable investment for what is a pretty simple product, 8k is a starting price for a traditional style and about 3K for a compact blower style.
After looking at lots of different designs and having a 200mm high powered fan in my possession  I decided to build a compact blower style for myself.

So here's the prototype. Pour the beans in the top at an even steady pace, fan on full pushes the beans up the chamber and over the bend falling into a collection bucket, any stones stay in the tube and are prevented from falling down to the fan by the centre screen.

Took a little bit of trial and error with getting the tube lengths right and best position for the input. Prototype works like a charm small rocks, big rocks, green beans, whatever I mixed in was caught in the destoner screen every time.

For a small to medium volume it's perfect, most expensive part was obviously the fan, found that on the web with a discount code for $240 shipped, the rubber collar was $42 and fitted the fan and 90mm plumbers pipe perfectly. The plumbing fittings were a total of $45 add in the braces at $18, had the trolley wheels lying around and the timber was an off cut of the roasterys new table.  $345 total cost, not too bad.

That is brilliant C!

hey Cosmic, nice destoner.  I've just decided I need a project like this so was hoping you'd be able to shed some light on parts you used - in particular the pivoted filter screen and the rubber collar / adapter going from the fan to the pipework.  Can you describe what they are or might be able to be found by, and even where you picked them up if possible (as an indication of the type of store where they were found) 

ok, so found https://www.bunnings.com.au/rain-harvesting-90mm-easy-clean-mozzie-stoppa_p4814163
One down, one to go

Hi Brett,  sorry for the late reply but seems you sorted the right parts to do the job. The hardest thing I found was getting the tube lengths right and the point of entry for the beans. To long and everything just sits in the tubes and or the beans have to be added so slowly you may as well hand sort. To short and everything just blows through at a great rate of knots including the stones.

I will have to measure the lengths but I think they were final cut lengths of 150mm.  The bean entry chute must be right at the top of the mozzi/stone stopper and only protrude internally a few millimeters so as not to disturb the airflow and beans, the angle must also be as flat as possible to avoid to much air flow returning up the 50mm tube but still enough angle that the beans will discharge into the 90mm destoner tube.  I used normal plumbers glue to join pipe but left the join between the stone catcher and the top section dry as occasionally you may need to get in from the top due to a large stone not allowing the spring door to open. For strength of the join for the bean entry chute I used a 90mm pipe hanger down to a 50mm bracket on the other end.  All parts came from the bunnings plumbing section, the feed funnel is a down pipe leaf catcher.  At the lengths I played around with I can now just freely pour the beans in and never overload the destoner, she never fails to clear the tubes bar 1 or 2 beans and gets every stone every time. I do find using a 10 ounce takeaway cup as a stopper in the feed in funnel helps the beans flow through. Working on some magnets now to ensure no small metal foreign objects sneak through.

Let me know if you need any other info.

It's looking great Brett & Chester.

You may also wish to consider experimenting with a slightly longer length vertical lift section as this could assist with debris separation but more importantly if you tune it correctly it may also be less sensitive to the variances in bean shape, size and density, e.g. less fiddling with adjustments for each time you use it.

When you have a longer column for the beans to rise inside of a vacuum, it may also assist in stabilizing pressure around the entire surface area of the orifice, rather than differentials (vorticity) that develop across areas of the pipe (it's a bit complicated to explain, somewhat like an irrotational vortex, e.g. particles moving or rotate at different rates to others).

Of course, changing that length will mean the airflow pressure needs to be adjusted.

A future mod to the design might also consider a vent with filter or sock to catch the fines from the agitation of the beans during destoning. As the beans are brittle and husk will be dislodged, this makes for a cleaner finished product, but alas it will return you back to the start again in tuning flow.

Thanks for the input mycuppa 

Brett, I found I achieved better bean flow when I moved the entry point as close as possible to the swing door trap, also I switched out the 90mm y section to the 50mm feed, again created better control.  Good job though and pleased you  took my project and made it work for yourself. Let us know how its going.

For me a very capable destoner for just under $400, has made my weekly kilos far easier to manage.

Anne Cooper showed me an idea of a large earth magnet on a cooling tray arm for collecting any foreign metal matter, not cheap at $240 but works a treat.

magnets are an interesting concept, but not new.
A few years ago I evaluated Loring's 35kg Kestrel platform.
At the time, Loring did not have available any type of de-stoner solution.
Their approach was to implement a rare-earth magnet (not sure which type) on the mobile weigh loader for the green coffee transport to the roaster's hopper.
I really liked this system - it was a mobile trolley with integrated weigh scale, powerful rare earth magnet and fast, effective loader.
Being the skeptic, I saw first hand small stones being isolated on the magnet - remember, this is on the raw coffee side.

I'm not sure how effective this solution would have been long-term and I'm sure a 3rd party destoner could have been bolted-on.

Loring have since developed a traditional destoner.

One day when I have time I will play around with these rare earth magnets specifically for raw coffee handling.

got any photos of your setup?

might be easier to troubleshoot if there's a visual to refer to?

best,

pat

Probably the simplest design I've seen for a domestic situation, is via the use of a Vacuum Cleaner that you can vary the speed of. Using a bucket and a pickup nozzle, you adjust the speed of the VC until all beans are picked up but rocks and other denser materials are left behind... 

Several designs can be found on a number of coffee forum websites, etc... 

Mal.