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Not so much a 500g 'bake-a-round' anymore!
Hi all,

First post and new to the forum. After owning a Gaggia Classic for a few years and still unable to make a nice coffee with Supermarket beans, I thought I should give this a go.

To my surprise, I managed to find a “Bake-a-Round” as soon as I started looking. $15 to buy and $18 postage! I think they’re probably quite rare in Australia.

The standard Master HAS-043K heat gun element and Chefmate cocktail shaker are too expensive or had to find in Australia so I’ve got a couple of 1500W plastic welding ceramic ones from ebay for $10 each and are contemplating casting a refractory cement element holder and “bake-a-round” base, something like Linnaeus’s excellent 3d printed/cast roaster,…. although I’d have to try making a mould manually.

The 1” diameter plastic welding elements are quite restrictive to airflow Linnaeus mentions, so my intention was to use two but I’m not sure if my house power supply can do this unless I rig up the elements to two different power point outlets. Our outlets are 240v 10A or 2400w. I think a special oven one might be 15A.

I’ll probably start with Fuji PXR4 PID (Is there a good cheaper version that does the same thing?) and speed controller although I did order a TC4 v4 from Oshpark and would eventually like to set up the android roast profiler….. If I can manage it!

Can anyone give advice on whether?

1/ A stronger motor than the one Linnaesus’s (18V 120W) would be able to force more air through a restrictive single coil. I haven’t yet purchased a motor but maybe something like this 2nd hand 960watt spa blower for $150.

2/ The best idea for wiring two coils.
sethyrish attached the following images:
stainlessmica.jpg coilplug.jpg powerboard.jpg coils.jpg linnaeusmotor.jpg

Edited by sethyrish on 03/03/2018 3:30 AM
That ceramic piece strangle the airflow too much, you should think to other heating element, imo.
Check a cheap hot gun instead, those models having the heating wire coiled on a mica cross, like this:
DIY: TO based IR 750g
Moded commercial: Dieckmann RoestMeister, Nesco, popcorn.
TC4ESP, PID controllers, MS6514 USB/Artisan/Apps
Grinder: MBK Feldgrind, mod'ed Porlex to 47 conical burrs, vintage PeDe Dienes, Kinu M38
Gaggia Mini, Aeropress, drip


sethyrish wrote:
... A stronger motor than the one Linnaesus’s...

Check out my recent post.

With a 4000W modified element, I need a 700W vacuum motor.
At a 500g batch size, the engine power to pickup the beans is 34% from 700W.
At 580g, it's 20% more, therefore 54% from 700W.
Thanks Guys.

Will2, What's the diameter of your element and pipe to roast chamber? It might give me an idea of whether mine will work. I had taken a look at your post and love your designs. Are you working with 3 Phase? you seem to have a lot of power at your disposal.
The diameter of the ceramic element is 35mm, the outside pipe diameter (from a heat gun) is 39.5mm.
Do not buy a element, buy a suitable heat gun. it is cheaper.
Everything can be seen in the other pictures.
I have 240V/16A (also 20A, 25A) single phase, or 3x400V/25A three phase (whole house).
Element 4kW is 1 phase 240V 14.5ohm, diameter of kanthal wire 0.7mm (now).
Can I show a chart of roasting or csv file, where is seen % of engine power and % heater power.
Hi and welcome to another Aussie!

A stronger motor would push through a bit more air but hard to say if it'll be enough. I got a $40 2in1 Stick vacuum off ebay to use the 600W blower. These are more than enough for 500g. I'm going to attempt to do 1.2kg with one in my current build.

Not sure what you mean by your second question. They should be in parallel and connected to a power circuit capable of supplying enough current. Running two 1500W elements plus a blower would be too much for a single power circuit. It could work, but I wouldn't risk it. If you want to run more than one you'll probably need a second circuit.

I use the elements out of the cheap Ozito heat guns from Bunnings. They measure about 31.5 ohms so about 1800W. They're about 38mm diameter.

Also, with a single 1500W element, 300-350 grams will probably be your max load unless to recirculate exhaust air to make it more efficient.
Thanks for the help.
Things seem clearer now. It's good to see how an Aussie does it, as things seem to be harder to get here. I'm having trouble finding things like Kanthal wire of the right resistance. There's only vaping stuff available!

After seeing Will2's pictures of a dissected element, I've decided to use both of my element/nozzle's to increase flow but I'm removing half the element from both to make 30 ohm's. These look like such nice units and hopefully the ceramic will help. Here's some pics
sethyrish attached the following images:
wire.jpg apart.jpg
I broke the wire in one, making it 12.8 ohms and the other is 14.2, so that's 27 ohm.
According to the online calculator that's 2133 watts at 8.9 A. Plus a 600W Stick/vacuum from big w ($29) motor makes it 2733W to run on a 2400W outlet. Is this pushing it to much?
If Will2 only has vacuum at %50 I guess it's probably ok??
sethyrish attached the following images:
stickvac.jpg totalcoil.jpg
Depends on your wiring/circuit breakers. But probably fine.

Nice find with the BigW stick vac. I didn't think any local places sold them so got mine off ebay for $40. I have another one that I use in my 350g roaster. I start the roast at 20% power and end at 10%. They can be a tad noisy but not too bad at lower speeds.
I picked up the stick vacuum today. At 600W, the motor looks tiny.
sethyrish attached the following image:
I can't get your picture to open Viliam.
Not sue what the problem is.
Don't throw away those old toilet pan collars. They could come in handy!
Coffee anyone?
The collar just happened to be the right diameter for the "bake-a-round".
I'll try using it to cast a refractory nozzle.
Edited by sethyrish on 02/24/2018 2:04 AM
Making progress with the "bake-a-round" but now I'm contemplating these two Pyrex cooking bowls which are made in France and rated to 300 deg C. Is this enough?

The top is a Primus lantern cover of pyrex. The water filter I got off the side of the road at our yearly throw out. I'm guessing this will allow me to do more than 500g if I want and the thing looks nicer, like a bubble gum dispensing machine.
What do you think?
Edited by sethyrish on 02/22/2018 3:28 AM
Ok!...I found out why no one uses pyrex bowls. It's similar to tempered glass and just cracks as soon as drilled.
Apparently if you have a kiln you can anneal the glass first and are then able to drill it. The second photo is a standard glass vase which can be drilled easily.
I notice Alex Bright on youtube uses a vase from ikea. He's able to use without it breaking due to thermal shock. I guess this is just hit and miss with regards to glass quality.

I should probably just go back to the tried and tested 'bake-a-round'.
I'm going to attempt to use a vase in my current build. 6 inch diameter with the base cut off.
greencardigan attached the following image:
Are you going to test it first or dive right in.
This guy says a rapid change of over 150 deg C will make normal glass shatter so hopefully a slower change should be OK.

I'm going for the gumball machine look so might try these cheap "durable" salad bowls from Target.
I received this TC4 v4 from Oshpark on Friday. I'm having trouble finding a post on how to modify it to a more recent version. I'd like to eventually set it up for the bluetooth android so may need some help later.
I've have limited experience with SMD components though, so will have to see how I go!
I was planning to just test it with some old beans first. But I guess I should run it without beans for a while first.
Do your tests with chickpeas instead coffee, similar shape and caloric/thermal properties, roast temperatures also in the same ballpark, i.e. will not char at 200C/400F,
Must cheaper... but will not crack :)
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