Geoffrey, interesting observation regarding the burr. Honestly, I have such a limited experience with grinders that I didn't recognize it as a feature. However, you are correct in that it is basically impossible to bind the burr due to that smooth exit. I also believe that it helps to encourage dispersement of the grind upon exiting the burr. Despite the impressive nature of the Robur burr, it seems natural that once any grist has been generated after the first crack any conical burr would be self centering. I'd bet there's a study out there somewhere!

I chose that burr based on the findings in the Titan project. In hindsight, it may not have been the best choice for the shear size (and thereby horsepower) of the burr, but I love how quiet and smooth it is on the hand grinder. I've considered just building a 2:1 gearing for a hand crank to run in a similar design to those we've seen in this thread as well.

I am pretty confident that the apron on Versalab's shaft in the burr is for popcorning. Given the extremely narrow resulting entrance to the burr, I think we can be confident that coffee beans are disinclined to bridge under the circumstance. Just give them a route to the burr, and they'll get there.

The hand grinder was my first real project that I cut on the Bridgeport. If you look closely (I don't recall if it shows in the images) one can make out the 'steps' in the stepper motors going around the turn. I don't really care too much about that level of detail, but it was fascinating that it showed through. The project taught me a lot about both the milling and the grinder requirements. I've also got a sizeable lathe that I'm even less skilled with and have yet (probably never will) to convert to cnc.

Big toys are a benefit of being part of an old farming family

edgar

If I were shopping for a conical burr today, I would look very hard at the Kony burrset as it appears to be as well built as the Robur, but smaller in diameter (about 15% smaller). The possible upsides being less need to funnel the grind, and less horsepower into the burr. Downside would, at the least, be slower grinding per shot; but I don't really care about speed at home. It also carries less surface area for grinding, which may affect flavor profile; however, I expect the real flavor issue is more likely a function of temperature resulting from manufacturer speed and burr mass.

For those of you who've plumb your espresso machines into the house water supply, you could always liquid cool your grinder burr with the water on its way to the machine! A couple wraps of copper tubing around the outer burr would probably transfer a lot of energy, an pre-warm the water to boot.

edgar

Edit: I looked back over the Titan project and found that Jim had already done some temperature curves between the Kony and the Super Jolly with interesting findings: Titan Grinder Project

BTW, I finally took a moment to check the internet archive for the infamous Ashlar Vellum article on the M3 burr design process as the links that have been posted on this forum are no longer valid. Here's a link to the pdf version:
http://web.archive.org/web/200612072008...110512.pdf

edgar

Another option of supporting the inner (driven) burr from below the adjustable outer burr by arming back to the uprights statically. I'm still pretty undecided about the necessity of doing so, but I was curious what it could look like on my current iteration. The nice thing about this particular method is that I don't have to worry about the bearing having to slide vertically in addition to centering the rotating burr as it is independent of the carriage.
edgar

arriflex wrote:Dsc, you could do some tests with some beans and find out what the bridging is like. I like the way you've got a simple short taper to the burr entrance and could easily have straight sided hopper above. My gut tells me the beans will flow fine as you've illustrated it.

I like the idea of supporting the large upper pulley on both sides, and agree with the notion that belt replacement is a rare occurrence. It may simply be aesthetic, but one could support the bearing above the pulley from between the two pulleys and not have added complexity to belt changes since most of the force is aimed at the motor pulley...

edgar

<image>

That's how I would do it, except making the arm beefier and a bit slanted to make it more esthetically pleasing and tougher. A simple sheet metal cover could then serve as the belt guard, maybe fastened with a big thumbscrew that screws into the arm.

arriflex wrote:If I were shopping for a conical burr today, I would look very hard at the Kony burrset as it appears to be as well built as the Robur, but smaller in diameter (about 15% smaller). The possible upsides being less need to funnel the grind, and less horsepower into the burr. Downside would, at the least, be slower grinding per shot; but I don't really care about speed at home. It also carries less surface area for grinding, which may affect flavor profile; however, I expect the real flavor issue is more likely a function of temperature resulting from manufacturer speed and burr mass.

For those of you who've plumb your espresso machines into the house water supply, you could always liquid cool your grinder burr with the water on its way to the machine! A couple wraps of copper tubing around the outer burr would probably transfer a lot of energy, an pre-warm the water to boot.

edgar

The water cooled part is kinda nifty, but a bit too complicated. Maybe an optional accessory? How about a water-jacket and some grooves in the outer carrier for a "saturated" burr?

Sure, if you spiral those grooves around the burr you'd have a pretty efficient heat exchanger design should be easy enough. And oh, so important!

Hmm.... Espresso parts has three conical burrs available:

Kony 63 mm $165
Robur Single phase, 71mm $201
Robur three phase, 83mm $156
Edit:
They also have:
Rossi 68mm $244
Innova ??mm $56

Mark

Attaboy, get your shopping on!

I haven't handled the Kony burr, but it really looks identical in about every way except scale to the Robur 71mm that I have. It appears to likely have maybe two or three fewer beans able to enter the coarse top of the burr than the Robur. It would be nice to have slightly lower torque requirements for the motor and a slightly smaller diameter exit path to deal with. Not to mention the price difference. I think I got mine on eBay a few years ago, but I don't honestly remember if it was there or EspressoParts anymore.

edgar

All this burr talk got me thinking how hard it would be to draw one. I did this in just a few minutes, I know it needs a ton of refinement in angle and cutting edges, but it's kinda fun.
Autodesk inventor