Any machinists want to build a custom part?

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mitch236
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#1: Post by mitch236 »

I don't know who else to ask since I'm not a designer nor have any backround in machining. Here's what I want to accomplish. I would like a tamper like device (a piston) that I would use to apply pressure to beans in the throat of my grinder. The base of the piston would be rounded much like a curved base but much more (I have a shower flange that the curve is perfect as a template). It also would have a doughnut hole in the center for the burr bolt to be able to reside and push the random bean into. There would also be a sleeve which the piston (the tamper like part) would slide into. The sleeve would fit snuggly into the throat of the grinder to give the piston stability up and down and would extend appox 1" above the throat.

Anyone feel like tackling this project? I wish I could draw so I could better describe what I need (or think I need).

da gino
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#2: Post by da gino »

HI Mitch, I know exactly what you are looking for and it was easy for me to build one out of wood when I was testing out a Macap M7D. I didn't make an elegant one since it wasn't my grinder and i was just checking to see if it was a good idea, but it worked very well allowing single dosing to imitate a full grinder, where before my single dosing results on that grinder had been erratic . I don't do work for others since I am not fast enough to justify the time vs profit, but I imagine Dave (Cannonfodder) could make you something that would be great. If you wanted something heavier than wood, he could have a weight that screws onto it or obviously make the piston larger. I was going to determine the pressure from a column of beans and adjust the weight of my piston to match, but did not get around to it before I returned the grinder. I still plan to do it some day.

Custom Wood for your Espresso Machine

Hugh

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decaf_Ed
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#3: Post by decaf_Ed »

Or you could maybe assemble one from common plumbing parts, like the white PVC shown middle and right:

There's two PVC reducer bushings joined by an unseen brass nipple (brass for more mass), with a brass plug at the top for a handle. Weight is around 140 gram, if I remember correctly.
The corners of the hex on the two PVC fittings were filed a little bit to fit in the "hopper".
Since this picture was shot I've added radial slots in the bottom so that a slow spinning of the plunger by the handle (while grinding) destabilizes beans that sometimes get hung up.
-Ed

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DJR
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#4: Post by DJR »

Here are a couple pictures of a device I made for my Rossi 45 (now not mine) which did the job. The purple plexiglass holds the plunger which has a lip on it to keep it from hitting the center screw.



Here's another. Ignore the stepless mod.



There were two 0-rings let into the purple tube to hold it in the throat of the grinder. The plunger was a piece of oak firewood. It also had an 0-ring which rested on the top of the purple tube.

The purple tube is plexiglass. I think I got it at Tap Plastics. The whole thing is easy to make -- half an hour, but not possible without the grinder, and if you send me the Robur, you might get back something else.

dan

mitch236 (original poster)
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#5: Post by mitch236 (original poster) »

Ed gave me the idea for this version of his single dosing mod. What I did was use a PVC pipe and two Set Screw Couplers (a 2" and a 1") and the tamper piston from a tamper I no longer use.

Here's a picture of the coupler (You can only see the 2" coupler. If you look closely, you will notice the tamper piston on the left end):



The underside showing my solution to the beans not allowing the piston to stay on top of the burrs (You can see the 2" coupler with the 1" coupler on the inside and if you look really closely you can just make out the threads for the tamper piston inside the 1" coupler):



The grinder with the PVC and piston in place (you can see how much I had to adjust from my 18 mark to achieve the same pull from 18gm using single dosing):




The setup works perfectly. It took a while to dial in a consistent grind and I had to add WDT to my prep but I am happy overall. Now I am converting my grinder to a dosered version.

decaf_Ed
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#6: Post by decaf_Ed »

Looks very robust.
mitch236 wrote:I had to add WDT to my prep...
And heavy. What is the equivalent bean column height?
-Ed

mitch236 (original poster)
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#7: Post by mitch236 (original poster) »

decaf_Ed wrote:And heavy. What is the equivalent bean column height?
-Ed
I'm not too sure but I assume it doesn't really matter in my setup since I have an auger. Maybe I'm wrong but unless you're crushing the beans into the burrs, I don't see how having more than a full hopper would affect my grind. The way I think about this is I want as much consistency as possible. With a hopper, the column height is constantly variable which may or may not affect the grind but my approach is constantly consistent which can't be a bad thing, can it?

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decaf_Ed
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#8: Post by decaf_Ed »

I totally agree on the concept... mass that isn't changing (plunger) is high, mass that is changing (beans) is low, therefore consistency. It's just the comment on having to add WDT to the prep that kinda suggests the possibility that the auger isn't totally isolating the burrs from the effective weight on the beans.
But if you got to where you want to be, congrats!!!
-Ed

mitch236 (original poster)
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#9: Post by mitch236 (original poster) »

I think the reason is that I get so many more fines or chaff and that negatively affects distribution. I think most of my distribution issue develops late in the grinding process when the beans are no longer affected by the piston and are free to bounce around below the auger. I am hopeful that once I convert the Robur to dosered, my grounds will be "blended" sufficiently to eliminate the need for WDT.

mitch236 (original poster)
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#10: Post by mitch236 (original poster) »

Just a quick followup after a couple of weeks spent fine tuning my setup. I converted the RoburE to the dosered version using the parts from my Mini doser and a new housing. Even though this setup allows for very good distribution, I found the following protocol gives the most consistent results.

I no longer weigh the shot after ginding. I found after much experimentation that if I weigh my beans before grinding and add roughly 0.2gm I end up with my 18gm dose within acceptable tolerances. I also found that although the doser does a good job of distribution, it is not good enough for my VST basket. Therefore I use WDT to re-distribute the grounds. This has given me beautiful pours and consistent shots.

I am now making the best espresso I've ever made. I finally feel like all the pieces have fallen into place and now my journey to discovering the nuances of brewing parameters and coffees can begin!

I owe a big thanks to this website and all the great contributions the members have made.

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