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BigBadWolf

Building a Handgrinder around 83mm Robur Burrs

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Hello everyone!

 

Since the HG One is 1000£, and thus roughly 1000£ out of my price range, I thought about building a hand grinder around the 83mm Robur Burrs myself.

I don't know if anyone here has tried this before, but any input or links would be appreciated!

 

Also, if you want to discourage me before I start, that's cool too.

If you don't manage to discourage me, I will try and document the results, and then post them on here. Regardless of the outcome.

 

Thank you for your time and have a wonderful evening.

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By the time you get it to work well I'm sure you'll be down more than the price of a hg1.

 

*unless of course you have a cave of machining tools.

 

What's the motivation for doing it?


Coffee making stuff :coffee:

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The first motivation is being an engineer, and I get a kick out of making things myself.

The second really is money, I don't want to and I can't spend hundreds on a grinder, but I want a decent one.

However, buying the Burrs, mounts and the adjustment..thing.. would take out the hardest parts, I think. That's around 180£.

 

I could theoretically use the workshop at my university, if I really huge tools. I will definitely make the frame there.

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I wish you all the best with this! I've been thinking about the same sort of thing but powered. I suspect it's not as easy as it looks. What did you have in mind for the adjustment mech?


Rocket Giotto Evoluzione v2, Eureka Zenith 65E, Niche grinder, Pharos grinder with VoodooDaddy mods, Eureka MDL, Torr Goldfinger, Smart Tamp. Various coffee stuff.

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@Rob666:

 

Thank you! I agree, the more I plan, the less of a plan I seem to have.

As for the adjustment, I'm not really sure. So far I have mainly been thinking about how to mount the burrs so that they really just rotate around their own axis, and don't wobble or move in unwanted ways. I imagine even almost undetectable wobbling will make the grind inconsistent, and I really hope that's not going to be a problem. I haven't done a lot of mechanical engineering so far.

 

Edit: Oh and I almost forgot: Atm I'm thinking worm drive.

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Worm drive good but complex. I think careful measurement and massive and precise construction is the answer to the alignment. But that is only the beginning of the issues. There is the big problem of what happens to the grounds when they leave the burrs. If the path is straight you end up with a doughnut. (Have a look at the videos of the HG1 and Versalab.) I've been thinking an offset funnel might be one answer.


Rocket Giotto Evoluzione v2, Eureka Zenith 65E, Niche grinder, Pharos grinder with VoodooDaddy mods, Eureka MDL, Torr Goldfinger, Smart Tamp. Various coffee stuff.

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Well, you can devise the wormdrive by calculations and then calibrate it, or you can just get one and measure how far it moves the burrs per tick, and adjust your scale to it. Maybe I'm oversimplifying here.

As for the offset funnel; I think you would mainly increase the amount of grind lost in the grinder, which you wouldn't have with free falling grinds.

Do you think the HG One has a bad solution for what happens to them once they leave the burrs?

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I know the robur is conical but I am going to suggest that you try to find drawings or examples of the EK or Santos grind chamber assembly in order to clarify in your mind how this has been done well before but on an electrically driven grinder. Those old designs have stood the test of time for a reason. Relatively speaking, adding a drive shaft and hand crank should be simple.

 

I too have wondered if it would be viable to re-create the Santos in a workshop but using 100mm or 120mm burrs

 

The same should apply to conicals but the history of these is more recent

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@Bigbad wolf. The direct output approach does produce a doughnut from conical burrs. Therefore not really suitable for direct grinding into the basket, hence the HG1 catchpot. My Pharos' do the same thing. Have a look at the Megalith.

Although the video doesn't make it very clear there is definitely an offset in the delivery chute. Even with this though the distribution is a bit of a faff.

The other thing I've been thinking about is tilting the burrs in the same manner as a Mythos. I suspect the vertical burr orientation in the EK and Santos is responsible for the low retention. It's just an idea but I think it would be worth experimenting. My thinking is that it should be possible to reduce retention to minimal and improve the delivery pattern to the point where you could grind directly into the basket.


Rocket Giotto Evoluzione v2, Eureka Zenith 65E, Niche grinder, Pharos grinder with VoodooDaddy mods, Eureka MDL, Torr Goldfinger, Smart Tamp. Various coffee stuff.

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One further thought. Could it work with conical burrs mounted horizontally a la EK etc. with an archimedes screw feeding beans into the burrs?


Rocket Giotto Evoluzione v2, Eureka Zenith 65E, Niche grinder, Pharos grinder with VoodooDaddy mods, Eureka MDL, Torr Goldfinger, Smart Tamp. Various coffee stuff.

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@grumpydaddy: Thanks for the input, great suggestion! Flat burrs need more rps than conicals to work, since the beans have to be "thrown in" to the burrs, and I think it's much more complicated to devise a flat hand grinder than a conical one. (just look at the simplicity of the hario skerton, for example).

 

@Rob666:

ah, I see what you mean. Again, flat burrs work throw zentrifugal force, which needs a certain amount of rps. The logistics would be totally different, since conicals need gravity to push the beans through. I believe tilting the conicals beyond ~30° would take a lot more thinking and planning, so the best option to avoid doughnutting may be to tilt them just a few degrees and make a very steep offset ramp (again just a little more than 10°) so you get a very narrow and small ellipse instead of a circle, which may be closer to what you're looking for.

Having the burrs tilted, however, makes the adjustment mechanism a lot more complex..

 

Another Idea: Mount a REALLY heavy flywheel, so that it's difficult to get it moving, but so it can grind on its own for quite a while, and make the output hole really small, then aim it between the edge and the center of the portafilter and turn the filter with your thumb. This doesn't sound very convenient, I know, but you might want to think about having a little workaround like this instead of making the whole grinder much more complex.

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If you read about any of the grinders that have been custom built on HB, or here by DSC, the price for constructing su h a thing always seem to be in the 'dont ask' category.

 

Such a thing, to be any good, needs to be engineered to the smallest tolerances you can get so there is as little play as possible in the mech.

 

A chat with DSC would tech you a lot about such a project and where the costs come from.

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Interesting stuff! Not so sure the narrow nozzle is a good idea. If there is any static I would think the chances of sticking and maybe blockage would be quite high. It would be a very interesting design to to see though.

 

I was thinking that mounting conical burrs horizontally with an augur feeding beans to the burrs might be the simplest to construct. The adjustment mechanism could be similar to an EK and there would be one shaft straight through to the handle (or motor) at the opposite end. It should also be possible to have a sweeper or sweepers at the output end thus dealing with grounds stuck to the delivery side of the burrs and the inside of the delivery chamber.


Rocket Giotto Evoluzione v2, Eureka Zenith 65E, Niche grinder, Pharos grinder with VoodooDaddy mods, Eureka MDL, Torr Goldfinger, Smart Tamp. Various coffee stuff.

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@ Dylan Sorry I took along time over the last post and missed yours.

 

Yes, I have read those threads and I'm sure you are quite correct about the costs. From what I've seen of it DSC's amazing project is a tour de force of engineering expertise and obsessive attention to detail and even he still has problems to solve. This makes Doug and Barb's achievement with the Pharos even more remarkable. An affordable big conical burr hand grinder that actually works, albeit with a bit of faff in the absence of the VoodooDaddy mods. Similarly, the HG1 goes a long way to achieving the goals.

 

All this doesn't stop us playing with other ideas though! :)


Rocket Giotto Evoluzione v2, Eureka Zenith 65E, Niche grinder, Pharos grinder with VoodooDaddy mods, Eureka MDL, Torr Goldfinger, Smart Tamp. Various coffee stuff.

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Wow, I just read up on the Pharos and DSC's project, and I have to agree. That's pretty amazing. I think I'm going to buy a Pharos and take a little more time working on my own grinder, but I can't seem to find where to buy the Pharos.. on OEHandgrinders they just say it's out of stock.

Would any of you know where to get it?

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They have been saying for some time that they are not going to build any more. There was a small batch a month or two ago and that is supposed to be the last.

They might of course find enough bits to do another batch. The only way to find out is to keep visiting their website. The unmodded version is OK but can be a bit of a faff. The important VoodooDaddy mods roughly double the price but are well worthwhile IMHO.

 

You should be able to find one second hand though without too much bother.

 

I might sell my unmodified one once I've sorted out a powered grinder. If I do it will appear in the sales sub forum.


Rocket Giotto Evoluzione v2, Eureka Zenith 65E, Niche grinder, Pharos grinder with VoodooDaddy mods, Eureka MDL, Torr Goldfinger, Smart Tamp. Various coffee stuff.

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It seems to be the best Grinder for my price-range, if it's true that its quality is en par with the Robur, and I've read that a couple of times. Can you concur, Rob?

And I'm currently living in Austria, so I might have trouble buying off the forum. But I will keep looking for a used one.

As for my design, I may be influenced by the HG One. As of now, it looks exactly like the Hg one.

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Sounds like a great idea.

 

I think if you can sort out the machining side of things yourself.

 

That should take care of a significant portion of the costs.

 

Buying the standard parts - Burr sets, bearings, motor or gear sets should be cheap enough.

 

The rest is just your investment in the time and your Engineering/Design problem solving ability.

 

I think terranovas re-engineering of the versalab grinder is a clear example of what can be done, if you are engineering minded.

 

I say good luck to you and if nothing else you will learn something from the exercise.

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@Bigbadwolf Although I have little to compare it with I am very happy with what the Pharos produces. Much better than almost all the local (and not so local) coffee shops. So much so that I think I'm spoilt. Definitely not happy with results from SJs and larger etc. in local coffee shops so don't want to go that route. Looking for 'budget' 'titan grinder'.


Rocket Giotto Evoluzione v2, Eureka Zenith 65E, Niche grinder, Pharos grinder with VoodooDaddy mods, Eureka MDL, Torr Goldfinger, Smart Tamp. Various coffee stuff.

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@squarepusher: That sounds interesting, but I can't seem to find anything when looking for terranova's re-engineering of the versalab, would you happen to have a link for me?

@Rob666: Wow. My first goal was to aim at a grinder that is "good enough", so coffeeshop quality would already be great. Now I definitely want a Pharos.

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@BigBadWolf The Pharos is good exercise too. :) The unmodified ones can be a pain to get into alignment and keep there once aligned, the grind adjustment could be easier but I don't have any trouble. The modified one has stayed in alignment since I've had it (5 or 6 months) and is more convenient to use. I was lucky enough to find one ready done but so far as I know the bits can still be obtained from VoodooDaddy in the US.

Keep an eye on the 'For Sale' thread or try a 'Wanted' post. You should reckon to pay around £180 for an an unmodified one and up to double that for a modified one depending on what's been done to it.


Rocket Giotto Evoluzione v2, Eureka Zenith 65E, Niche grinder, Pharos grinder with VoodooDaddy mods, Eureka MDL, Torr Goldfinger, Smart Tamp. Various coffee stuff.

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I think its an interesting idea, Funnily I was admiring the HG one yesterday and contemplating something similar.

The HG one and Pharos are great inspiration. From reading about them its clear that they both needed a lot of development.

You are fortunate to have access to a machine shop and most likely some CAD software.

Building something similar to these grinders wouldn't be too difficult, I think real challenge will be in refining the process.

I don't think its a crazy idea, from an engineering point of view its a very simple process, you just need to build some high quality parts to fit it all together.

 

Have you found any stock parts yet to get you started?

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