Grinder Project - Update - Page 8

Grinders are one of the keys to exceptional espresso. Discuss them here.
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TomC
Team HB

Postby TomC » Sep 06, 2017, 11:21 pm

Matt that thing is absolutely beautiful. Glad it's working out after all your efforts.

Thanks for sharing all the progress.

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MB

Postby MB » Sep 07, 2017, 1:11 am

Ok, here it is in action. Apologies for the background air conditioning etc.

LMWDP #472

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Randy G.

Postby Randy G. » Sep 07, 2017, 12:07 pm

Impressive, to say the least! My only commen is that the small-diameter rod sticking out from the main shaft and above the "bean hopper" certainly precludes the wearing of any dangling jewelry or loose, long-sleeved clothing!
Espresso! My Espresso!
http://www.EspressoMyEspresso.com

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MB

Postby MB » Sep 07, 2017, 1:08 pm

Good observation. That pointer is removable, as I wanted to be able to maintain my setting while I wasn't around to keep an eye on it, if you know what I mean. Once dialed in it's easily taken out until needed again. Now placed at work, the grinder is on a deep counter in the corner which helps in case I forget to remove the pointer.
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slipchuck

Postby slipchuck » Sep 07, 2017, 2:10 pm

MB wrote:Ok, here it is in action. Apologies for the background air conditioning etc.

<video>

Can't see the video :)
Oops there it is!

Randy
“There is nobody you can’t learn to like once you’ve heard their story.”

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MB

Postby MB » Sep 08, 2017, 7:25 pm

Here's a sound reading of the machine grinding beans in the kitchen at work. I held my phone at ear level when operating, so that's the closest anyone is likely to get. It's not super quiet at about 79 decibels, but one of my coworkers commented that it was quieter than she thought it would be. That's really what I'm after.

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MB

Postby MB » Sep 24, 2017, 8:04 pm

Well, after using the Colossus grinder a bit, I noticed that the lower funnel felt slightly warm compared to my home grinder with the same burr. Since I dose 20 grams at work and only 16.5 at home there's more opportunity for the burrs to warm up. Additionally, there's more static, even with RDT.

I had glued the variable speed switch to full speed to keep the momentum high when I was having all of the drive belt issues. The speed is definitely faster than my setting at home, which helps explain both the warmth and more static, due to the friction and perhaps evaporation of the RDT misting. The static is a little less with beans right out of the freezer, which seems to support the heat causing evaporation notion.

Although I realized fixing the speed issue would require a new switch, taking a lot of things apart and rewiring, the more I thought about it, the more I was resigned to address the issues. Unfortunately, an exact replacement switch was not available without getting the full drill, so now in addition to a new switch, I have a backup motor.

Here's the new switch, and instead of cutting the entire trigger face off, I just trimmed it and melted the coupling nut into it, gluing it into place.

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Fortunately everything went really well. The speed control works, even at fairly low rpm with beans. I'll have to test it a bit more, but it was working at a lower speed setting than I intend to use. Also, the static seems much better. I'll give an update and another sound reading once I get it back in the office.
LMWDP #472

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MB

Postby MB » Sep 29, 2017, 7:12 pm

At the lower speed the sound reading is similar. It continues to grind well at the lower speed and with significantly less static (still with RDT). I'm very happy with the way things turned out.

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MB

Postby MB » Jan 14, 2018, 2:40 am

seanc56 wrote:Look at swapping to HTD with 5mm pitch and 15mm belt width if you can accommodate the size. I don't think you will ever get the XL to work in this setup. Going to larger pulleys will help reduce tooth load as it will bring more teeth into mesh too.


Yep, this comment back in August was on target, too much load on the teeth after all.

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As you can see, the teeth were sheared off. With the current space limitations I can't fit the suggested 5mm pitch pulleys, but I can increase the pulley diameter. Less torque would be required and more teeth would be in mesh supporting the load. I'm going from an 18 to a 30 tooth pulley, so 60% of the force is spread over 60% more teeth. Not sure of the tooth load math, but if I understand correctly then that's 36% of the original load on each tooth. If correct then I think we're in the ballpark, since it held up for a while with the previous configuration.
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MB

Postby MB » Jan 14, 2018, 6:00 pm

So here's the revised look with the larger pulleys. I had to use a smaller shaft to go to this larger pulley size as it they don't offer it with the same shaft size. That meant using a collar inside the bearings. Worse was that the narrower shaft is too small to drive the socket. (I had squared the end of the larger shaft to fit in the socket.). So, I'm trying JB Weld to fill the space between the smaller shaft (also squared off) and the socket. I am hoping that it holds under this compressive use. If not, then I'll see if I can find a square tube with an outer 3/8 x 3/8 dimension.

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[Edit: Seems to be working so far. We'll see over the long run. Thanks for tuning in.]
LMWDP #472