MonthAugust 2015

It’s all about the Benjamins

Over the past month we’ve been freshening up our corporate branding and we’ve worked with a professional designer to come up with some new logos and colour swatches that we think are pretty “kick ass”. We’ve been busy applying these changes to our website and trying to tidy things up a bit.

Old Digital Homebrew Logo

Our old logo

New Digital Homebrew Logo

Our new logo

This update also coincides with a bit of a quiet point in our trading as we’ve recently spent a month abroad and many of our products have run out of stock. We’re frantically ordering new parts and getting production back underway, but we’re also feeling the crush of the weakening Australian dollar stronger than ever. Digital Homebrew is primarily an electronics tech company and without much of a local industry we have to order most of our raw materials from overseas in USD. Meanwhile, up until now we have been selling our products in Australian dollars, so as our dollar has been slipping we’ve also had to frequently increase our prices and it just feels a little embarrassing. I don’t like the thought of our customers recommending our products to their friends only to find that the prices have been jacked up again!

AUD over the past 12 months

AUD over the past 12 months

With a long-term vision to be a global company, there has to come a time where we change our primary currency to something more recognisable than the Australian dollar. This week we’ve taken that leap and our website now defaults to USD. There is still a drop down menu where customers can select AUD as well, and the prices will be altered based on the current exchange rate at the time of purchase and the PayPal payments are always made in the currency that you select which means you still never pay a ripoff exchange rate or currency conversion fees.

Currency selector on our website

Currency selector on our website


Unfortulately we’ve had to bump our up prices a little during the conversion since our dollar has fallen so far, but it wouldn’t be fair to pass this onto our customers that have been waiting for us to get our equipment back into stock. That’s why we’ve added some coupons codes that can be used during checkout to achieve the older prices. They are:

Stir plate kits: OLDDIYKITPRICE

All coupons will be valid until October 18th 2015.

Onwards and upwards!

P.S. You can learn more about Benjamins here.

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Designing a fermenter for Xymo

Xymo’s purpose is to make it easy to brew great beer by ensuring a perfect fermentation. With so much emphasis on monitoring and control, we had some unique considerations for Xymo’s fermentation vessel, such as:

  1. Thermal Conductivity – We want to control the temperature inside our fermentor in the most convenient way possible (for the brewer) and by keeping our cooling apparatus completely external to the fermenter, there are no extra parts in contact with the wort that need to be cleaned and sanitised. Stainless steel is our favourite choice of material because it has decent thermal conductivity and a lot of desirable properties for brewing and longevity. Glass would be great too, but we steered away from it because it rately has a perfectly uniform shape, it breaks easily and can be dangerous, and also because it’s a poor thermal conductor that wouldn’t work well with our design.
  2. Overall shape – With the aim of attaching an external heater/cooler, thermal efficiency is important and we were looking for a fermentation vessel with walls that we could easily affix a thermal transfer plate onto, that would also fit easily into an insulating thermal jacket. With the expectation that our fermenter wasn’t going to have any flat sides (because corners are bad for fermenting and cleaning), we wanted a vessel that would at least be cylindrical. Unfortunately, many of the existing fermenters on the market actually have a very slight conical and oval shape to their walls and this would necessitate costly CNC work to fabricate a mounting plate that would fit. Legs were also a disadvantage because they would complicate the fabrication of a fitted insulating jacket.Fermenter shape
  3. Sensor attachment – In order to support the sanitary attachment of an airlock and sensors, we needed a fermentation vessel with modular mounting holes. The “gas in” and “beer out” posts of a standard corny keg were a tempting compromise, but they’re just a little small for a blow-off tube connection and many brewers report that they are easily clogged. Also if we wanted to fit sensors in there they would have to be extremely tiny. Some customisations will be necessary if we are going to use a corny keg.
  4. Sufficient volume – Speaking of corny kegs, while plenty of home brewers ferment in corny kegs, it is very limiting for the batch size that can be produced. If our ultimate goal is to serve from a 19 litre keg, then our fermentation vessel has to be at least a few litres larger to account for trub and krausen. A quick email to A.E.B confirmed that they can’t produce large corny kegs (>19litres) on their current factory line so I’d have to find my own supplier.
  5. Air tight – Some time ago I imported a number of Chinese kegs that were anything but airtight. The lids were warped and didn’t seal unless the clamping ring was done up extremely tight with a large spanner. Since this unfortunate purchase I’ve come to respect the importance of a good sealing fermenter design. In order to support natural carbonation and pressurised transfers, Xymo needs a reliable lid seal that works.
  6. Easy cleaning – Fermentation is messy, so for most home brewers, the ability to “reach inside” a fermenter for cleaning is considered mandatory. Unfortunately, this requirement rules out using the “commercial” style kegs as a fermentor because they only have a small opening for a Micromatic spear or similar. This is a shame because commercial style kegs are a huge market, produced by the tens of thousands and a fermentor based on these kegs might benefit from the existing economies of scale.
  7. Shippable – We want Xymo to be a “global” product that we can ship direct to our customers all over the world. The trouble of course is that the shipping for a single fermentor can range from “ludicrous” to “highway robbery” depending on your choice of shipping carrier. That’s why it is important that shipping weight (including volumetric weight) is a strong consideration in our product right from the outset.

So with these goals in mind we set about sourcing a fermentation vessel that we could customise for Xymo’s needs. Not surprisingly, many of our design criteria immediately steered us towards kegs because they’re reliable, strong, affordable and designed for efficient shipping. Furthermore, the “corny” style kegs have a removable lid that allows you to reach inside for cleaning. We just needed a corny keg with a large enough volume for single batch brewing, some nuts welded to the side so we can mount our cooler and to exchange the keg posts for a more universal type of fitting that could support our sensors.

The Samples

The moment we landed in China we started organising to have some samples shipped from various manufacturers around the country. A lot of our contacts appeared to sell the same products and it was a little time consuming to separate the manufacturers from the distributors, but a few simple questions about customisations and most of the distributors quickly lost interest. Three kegs arrived ranging from 19 litres to 25 litres and each had very different manufacturing techniques.

19 litre keg

19 litre Chinese keg

The 19 litre keg

This keg was the smallest of the three and although I was looking for a 25 litre keg, this 19 litre version was sent because it’s all the manufacturer had in stock at the time. The manufacturer assured me that they can also produce a larger 25 litre version of the same keg and that the diameter will be the same. This way I can still evaluate their build quality and move forward with our jacket and heatsink designs, knowing that it will all fit the O.D of their 25 litre keg later when it becomes available.

19 litre keg handle

The handle feels good

Keg handle welds

Keg handle welds

Nice seam welds

Nice seam welds

Untidy welds

Some untidy welds

Construction: Seam welded. Bottom is domed outwards. Rubber base added for stability. One comfortable handle. Feels solid and heavy for its size.
Surface Finish: Pickled and passivated leaving a smooth matte grey finish.
Weld quality: Seam welds are slightly raised but smooth to touch. Most welds are great, but quality looked a little worse near the complex “T” intersection of welds. Overall the welding appears to be similar to that found on A.E.B kegs (need to confirm with microscope).
Pressure rating: The lid is stamped as 130PSI.

Overall I am very happy with the quality of this keg. It feels sturdy and although the welds aren’t perfectly flat, they appear to be smooth and sanitary. Some are a little splotcy to look at, but even still they feel smooth to the touch. I would be happy to proceed with the 25 litre version of this keg.

23 litre keg

23 litre keg

23 litre keg

The manufacturer of this keg was very helpful to us even while we were organising our trip to China. The sample arrived quickly but unfortunately I have a few concerns about its suitability for home brewing.


23 litre keg top

Posts are mounted at the front

23 litre keg welds

Welds appear to have been grinded smooth

23 litre keg lid tabs

Lid tabs have black scale near their mounting welds

23 litre keg handles

Handles are a bit sharp and rough

Construction: Tall and skinny. End pieces are capped to overlap the main tube then welded on the outer edge only. Bottom is domed inwards like a drink can. Two carry handles that are sharp on the edges.
Surface Finish: Appears to be electropolished, shiny silver finish. The edges are sharp and a little rough in places. The lid has black around the attachments and there is visible pitting in areas.
Weld quality: All of the welds look quite good, but there are no welds on the inner joints of the end caps.
Pressure rating: No pressure rating mentioned on the keg or the lid.

My primary concern about this keg is that it is constructed with end caps that overlap the main cylindrical tube and that the inner seam isn’t welded. I worry that this may leave a tight groove that can harbour bacteria and yeast. Also, the inner edge is rather sharp and rough and this would also make sanitary cleaning difficult. Finally, the surface finish, lack of markings and general loose feel of the lid doesn’t fill me with confidence.

25 litre keg

The 25 litre keg

The 25 litre keg

This keg immediately showed itself to be a good candidate for Xymo. It looks and feels like it is built with high quality. The surface finish is consistent and there are no sharp edges.

The welds are almost perfectly smooth

The welds are almost perfectly smooth

Laser engraving

Laser engraving

The base of the keg looks like a giant soft drink can

The base of the keg looks like a giant soft drink can

The handles are interesting and very functional

The handles are interesting and very functional

Construction: Shorter and wider than the others. Metal parts are seam welded. The bottom end is domed inwards like a drink can. The carry handles are comfortable.
Surface Finish: The keg has been electropolished leaving it with a shiny silver finish. The surface has a slightly rough texture to it that is consistent all over.
Weld quality: The seam welds are almost perfectly flat. Special attention has been given to make the welds as tidy as possible.
Pressure rating: The lid is stamped as 60PSI.

Over all, this is my favourite keg of the three. It is hard to fault and I feel the welding is of a higher standard than even the A.E.B kegs we have at home.

Meeting manufacturers

With sample kegs in hand I was able to start designing our heatsink and thermal insulating jacket, but customisations still had to be made to the kegs to support our sensors and temperature controller. All three of the samples came from manufacturers in the East of China which meant that I would have to fly a long way to meet with them.

I organised a day trip to Ningbo to meet with the manufacturer of the 25 litre keg first, because I felt this keg was constructed with the highest attention to detail. The day started our with a generous spicy lunch followed by a tour of their metal working factory where they were just finishing a manufacturing run of thousands of commercial style kegs. I was lucky to see how their kegs are formed by drawing a flat sheet of stainless steel into a bell shape that forms the top or bottom halves of the keg. Structural curves are rolled into the sides of the keg, a hole is punched into the top bell and a fitting is welded in place. Finally the two halves are welded together on yet another automated welding machine and the base and lid handles are welded to the outside. All said, the process looks unnecessarily difficult and expensive, but the upshot is there is only one single seam holding the keg together instead of the three seams in a corny style keg.

A change of plans

Once I understood the construction process, I began asking my host about customisations such as replacing the beer in/out posts with small tri-clamp fittings. It turns out that my host had a lot of experience with tri-clamps and he showed me a commercial style keg that had a large 133mm ferrule instead of a small spear connection. This got me thinking…

  • The 133mm (5″) tri clamp creates an opening that is easily large enough to fit an arm inside for cleaning. Much like the corny keg lid, but with a better seal.

    Large Tri Clamp ferrule

    Large Tri-Clamp ferrule

  • The 133mm blanking plates are available with threaded holes in them. Perfect for mounting airlocks, spunding valves and sensors.
    5" tri clamp cap with threaded hole

    5″ tri clamp cap with threaded hole

    A 5" cap with two threaded holes

    A 5″ cap with two threaded holes

  • The commercial style kegs are technically superior to corny kegs because they have only one seam weld as opposed to three. They “should” cost much more, but they are actually cheaper due to economies of scale.

    Welding seams that contact the beer

    Comparison of welded seams that contact the beer

  • The commercial style kegs are also available in 25 litre sizes with flat, vertical sides. Almost perfect for mounting our cooling block to the side!

    25 litre commercial keg

    25 litre commercial keg

This changes everything! So now we’re busy organising a sample of this new 25 litre commercial keg with 5″ tri-clamp. The heatsink will have to be altered with a gap that accounts for the middle seam in the commercial style of keg, but overall this is looking like a very promising development for Xymo that will result in a unique and effective fermentation vessel.


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Designing Heatsinks

Yesterday was an important day in Xymo’s development. It started out with a bullet train ride inland to a city called Dongguan, and when I disembarked I was greeted by three members from a prominent heatsink manufacturing company. My hosts were very accommodating. They filled me with Chinese cuisine before shuttling me to their factory for a tour and a chat about business.

This meeting didn’t happen spontaneously, it was a culmination of numerous emails, Skype chats and iterations of 3D CAD designs to reach a design that would meet Xymo’s technical requirements while also being manufacturable at a reasonable cost.

Here’s a picture of our current heatsink design.

Xymo Heatsink Closeup

A closeup of Xymo’s heatsink fins

Xymo's heatsink

Xymo’s heatsink

Overall I’m very happy with our heatsink design, I’m sure it will perform adequately and we ended the day with plans to have two samples manufactured for us in the coming weeks.

Why all the fuss about heatsinks?

So first, a little background. Xymo’s primary goal is to make brewing great tasting beer easy and repeatable by tackling the biggest variable in home brewing – fermentation. At his heart, Xymo is a computerised fermentation controller and his primary function is to maintain wort at an ideal temperature throughout the different stages of fermentation, all thanks to the heating and cooling abilities of thermoelectric coolers (often referred to as the Peltier effect).

Xymo’s heatsink is one of its most important components because in order to cool beer, we need to dispose of a lot of heat (up to 300 watts of heat!) and the better we can dissipate that heat, the more cooling capacity Xymo will have, and the more efficiently Xymo will operate.

The heatsink we’ve come up with has a number of cool features and this was largely thanks to the design input from the experts at our heatsink manufacturing company.

The Fins

One of the main awesome things about our heatsink is that it is being built with a manufacturing process called “Skived Fins” which is very different to your typical heatsink.

Most heatsinks are produced with an “extrusion” process where metal (Aluminium or Copper) is heated and forced through a die that is cut the the shape of the heatsink’s final profile. While extrusion is the cheapest method for mass production, the disadvantage with extrusion is that you’re limited in the height and number of fins that can be stacked in a given space, meaning you need a relatively large heatsink for any given amount of power to dissipate.

Taking things a step up, a common solution to obtain higher fin densities and performance is to use a “bonded fins” manufacturing process where small channels are cut into a base block, and vertical fins are glued into these channels. While this process can yield a better heatsink with a much larger surface area for cooling, the trouble is that the glue isn’t great at conducting heat, so the fins are slightly thermally isolated from the base of the heatsink reducing performance.

For Xymo, we’re using a process called “skived fins” where the fins are actually sliced from the base of the heatsink and bent up at 90 degrees to it. This process requires some very interesting machines but it will give us the best performance possible for a moderately sized heatsink.

Heat Pipes

Heat pipes are truly amazing devices for distributing heat. They contain a liquid that’s under vacuum such that it is in a constant state of being partially evaporated, along with a wicking coating on the inner walls that can distribute the moisture inside through capillary action. We’re having prototypes made both with and without Heat Pipes so that we can evaluate their benefits for Xymo. On one hand, they will distribute the heat away from the thermoelectric coolers to the extremities of our heatsink, but testing will show if this is necessary.

Parallel TECs

This is a cool one (no pun intended). Thermoelectric coolers can be pretty complicated to model. When you pick up a TEC that says Qc 100watts, that doesn’t mean it will cool 100 watts, nor heat 100 watts. On its own it doesn’t mean much at all for a real life scenario. My first prototype for Xymo was a single-Peltier affair, and I found that while I could get a pretty sweet delta T of over 10 degrees celsius below ambient, it took about 24 hours to get there so I knew that more than one TEC would be required. Rather than building more prototypes, I then began running some thermal modelling with 2 or more thermoelectric coolers. From the software simulations I found that running three devices at a slightly lower voltage I found my coefficient of performance to be higher meaning less overall heat being produced for the same cooling effect. This has relaxed our heatsink requirements and lowers Xymo’s power requirements a little.

The curved base

This post would be incomplete without talking about the curved base that’s in the pictures as well. This concave block of machined aluminium will contact the side of Xymo’s stainless barrel to transfer heat. We are working with some stainless steel manufacturers to have our fermenters manufactured with nuts welded to them (more on that in another post) and it is very important that the two shapes mate up well. You can see one of the grey nuts at the top of the picture, this will actually be welded to the fermenter rather than being a part of the heatsink.

Xymo's Spacer

Xymo’s Aluminium spacer.

The size of this spacer is no accident either. Xymo will have the technical ability to heat at almost 300 watts, however this is far too much for single-batch home brewing needs and will be limited in software to around 30 watts like a regular heater belt. To size the contact patch with the fermenting barrel I calculated the contact patch of a regular heating belt and made sure that Xymo’s contact batch was significantly larger. Given the larger contact patch and the ability to apply only the amount of heating power that is required I believe Xymo will be able to heat a brew much more gently (and of course accurately) than a traditional heater belt.

Another interesting fact you might realise is that the curved heat spreader block is physically smaller than the heatsink. It is in fact only 80mm wide and 200mm high whereas the heatsink is 94mm wide and 240mm high. This is actually due to the Coefficient of Performance of the Thermoelectric coolers being far less than 1.0 during normal operation. E.g. When we are cooling, if we are drawing 20 watts out of the fermentor, we may we using 80 watts of power do do this, meaning although the cold side has to move 20 watts, the hot side has to move 100 watts total. This is why the Hot side is larger than the cold side.

Well that’s all for today. If you have any questions about the progress of this design, please feel free to post.


Michael Burton.



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Social Media Here We Come….

We have never been big on our social media and have always thought we have nothing much too talk about so why post…but now surely that we are over here in China we have something to say that might be of interest.

For this reason, we have set up this blog and we will also be posting regularly to our Facebook, Twitter and YouTube.

Follow us here: –
facebook bottle captwitter bottle capyoutube bottle cap




We will be posting every few days to keep you all updated about what we are up to and what we have planned whilst here in China.  Michael is next inline to write a post (and perhaps record a video) and he will have plenty of info for you.

This is an exciting time here at Digital Homebrew and we can’t wait to share this journey with you all.


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