Damn, I forgot all about this thread. I will try to get my idea drawn up tomorrow, it's not anything jaw dropping, but might be interesting non-the-less.

Hi guys,

I'm pretty sure the shaft is so thick to compensate for the lack of lower support bearing and to inscrese stiffness. I dunno how big the forces acting on the burrs are during grinding, but better make the whole thing bullet proof than worry in my opinion.

Cool idea with the side adjustment, makes it a bit easier as it removes the upper screw, but also adds the spring, so it's something for something. I've modified my design and now it hides the rotating elements between the plates:



the rest is pretty much the same. The sides are transparent simply to show how it looks like inside, I might make the plates rectangle shaped as it will be easier to cover everything up.

I was asking about the bean hopper as I'm not sure how 'steep' it has to be, whether to make it narrow near the burrs or not. Guess it's a bit like the funnel design, try out various things and then decide.

Re sketchup I do the same, I usually draw a line from the circle to the centre, it always snaps to the centre point and you can align elements easily.

Regards,
dsc.

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

At the torque that I was measuring using my hand grinder, the horizontal force that the motor should be imparting at the 2" radius of my big drive pulley shouldn't be more than around twenty or so pounds. I don't think the upper support for the drive pulley is all that feasible as long as there are two bearings underneath. However, it does afford the opportunity to make the whole upper plate quite a bit thinner if one doesn't need to house two bearings, so it could be more economic.

Personally I like the turntable look of an exposed drive mechanism

edgar

Hi Edgar,

I agree with the mounting of the top bearing, I just thought hiding the pulley might look better. One can always do a simple |-| support just above the pulley, attached to the sides of the main top plate, easier, cheaper and probably effective as well.

For your side adjustment mechanism, you can use steel rods as well, mount them on the sides of the carrier and put springs at the bottom ends which is probably what you are looking for. The downside is added cost as you need rods and linear support for the carrier, but it would probably work nicely.

Regards,
dsc.

BTW, I honestly believe that the spring idea pushing against the adjuster is a good idea for any design to minimize backlash and improve repeatability in the adjustment system.
edgar

Dsc, it is true that I could use the rods likely as effectively or moreso as the slotting system I've illustrated. Cost and simplicity are what are driving those decisions, the more I can do with fewer components the better! Eventually I would like to explore the aesthetic interpretation of the engineering requirements; to my mind the fewer engineering requirements I impose upon the aesthetic design, simpler and cleaner it usually ends up. In the end, this thing is going to live on my counter, and it has to be both attractive and useful to my wife to stay!

edgar

The different design criteria and different approaches for the same end goal makes this a very interesting forum. Great work!

IMO, having a cover over the belt addresses an important safety issue. If I remember correctly this was an issue for some users of the Versalab grinder.

As for the bean and grinds path here is how Versalab does it:

http://www.versalab.com/server/coffee/grindernew.html

It is interesting to see what appears to be an "anti pop corning" device below the tapered section of the shaft?

Geoffrey

P.S. For those who are interested here is an article that discusses some aspects of the design process:

http://www.informatics.sussex.ac.uk/cou...Ullman.pdf

Cool article. The anti-popcorning considerations are important, especially if the hopper is particularly short. I have always fought popcorning in my hand grinder implementation; running around the kitchen picking up rogue beans before my baby girls got to them. Versalab seems to be very pro-active on that issue; however, I seem to recall seeing a picture somewhere on this forum where a user had a tupperware lid cut around the shaft as a hopper cover nonetheless.

I am very pleased with the constructive nature of this forum, rather than what often because destructive. Kudos to all for a great attitude! Keep the drawings flowing, whether on paper or screen and whether posted or not.

BTW, despite owning a cnc mill, an old Bridgeport that I replaced all the controls in so I could interface with a 'modern' computer, I haven't got the slightest how to use it properly. Anytime someone has machine advice, I welcome it!

edgar

edgar,

I agree with you the constructive tone of this forum. It is what makes it so successful and interesting.

I think we can safely assume that any part on the Versalab grinder is there for a function. Hence my observation and question as to the function of that part on the drive shaft. It may not be an "anti pop corning" device. Maybe it helps the beans flow downward, or trap them in the chamber, or all of the above? Any other ideas?

You are very fortunate to have a CNC converted Bridgeport Milling machine. I assume that the parts on your hand grinder shown in an earlier photo are made on it? If so they excellent, and machined the old way using a rotary table would probably not produce such good results.

I looked again at the photos of the burrs you are using. The lower section of the inner burr has a smooth conical surface at the bottom. In my limited experience not all burrs have this feature. Maybe this is the key to your "burr self aligning" success?

Geoffrey