DIY robur belt-driven grinder

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bostonbuzz
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#1: Post by bostonbuzz »

Today my metal finally came (except 1 piece), so let the building begin!




Those are 71mm Mazzer burrs, to put the metal in perspective. I'm going to build a belt-driven motor out of aluminum. The design will have 2 bearings on either side of the large pulley for optimal stiffness. I will be using manual machining tools at a local facility. Wish me luck! I will update as things progress.

I've been thinking about doing this for some time, but I wasn't aware of the great resources here in Boston for doing work like this. I parted it out, and to my surprise, the parts cost was below the cost of an HG-one - so I figured I'd go for it. The time milling and using the lathe will likely be a LOT, but it's a pleasure to work on.
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kwantfm
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#2: Post by kwantfm »

Nice project. I'll be watching with interest.
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jsolanzo
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#3: Post by jsolanzo »

Interesting. I wanna see the outcome of this one. I think if you can keep the burrs stable, then you're pretty much good to go.
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dsc
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#4: Post by dsc »

Good luck! always nice to see someone experimenting.

What motor is that if you don't mind me asking? I reckon it will be a single dosing machine?

Regards,
dsc.

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bostonbuzz (original poster)
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#5: Post by bostonbuzz (original poster) »

Thanks for the support!

I'm using this motor http://www.bodine-electric.com/Asp/Prod ... Sort=11064 with the large capacitor. It will be single dosing (I don't believe in hoppers). I'm assuming that I will have to have the motor running while I put beans in, but if not, then great. It's an AC motor, which have less startup torque, but it still has plenty of torque, considering the 3:1 reduction gearing.


As far as burr stability, I will post videos of dial indicators. I'm aiming for as precise as my equipment can supply, but we shall see...
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Randy G.
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#6: Post by Randy G. »

That pile of parts looks like a machinist's fantasy!
"What to build... what to build?"
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dino
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#7: Post by dino »

to quote Nike...... just do it
we all want to see it - post lots of pics please & good luck with it :lol:

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jsolanzo
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#8: Post by jsolanzo »

if successful, put me first in line if you end up sharing the wealth lol.
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TomC
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#9: Post by TomC »

You should make friends with Terranova and take notes :) This is going to be cool to watch develop!
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bostonbuzz (original poster)
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#10: Post by bostonbuzz (original poster) »

So I spent about 8 hours at the machine shop yesterday getting familiar with how everything works and doing a little squaring and turning. First, here is the basic design of the grinder. The giant square piece will hopefully end up round (if I can figure out how to use the CNC mill), and will have a large round bar threaded into it that will hold the outer burr.



I managed to get one of the bearing blocks all squared up- it looks great. It's square to within .002".



and all finished .... (should I round the ends?? hmm...)



I also finished the top and bottom "washers" that will be secured on the shaft by an allen key. I made them out of this bar stock.



Here is the top one, which will sit above the top square bearing holder. It has a cutout for a thrust bearing that extends about .5mm from the bottom - nice.





I started on my "QD" bushing, with the 4" aluminum stock. It took forever to get the lathe set up 0 mostly because it was my first time. Then I realized that the available cutting tools are quite dull (.002"/per pass at 2 inches = TIME). It was late, so I called it a night.

I'll be out of the country next week and weekend, so I probably won't get to work again for a coulpe of weeks. In the meantime, I ordered some indexable lathe tools to speed things up significantly.

One question maybe some of you could answer- how far do you think I should place the bearings? I can adjust this by boring the bearing holes deeped in the aluminum blocks. I could even put two bearings above and below the pulley - but I think this is overkill. I think 2" apart is better than 1", but I'm not sure... This grinder is a prototype, so some things will have to be learned by trial and error.
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