Can someone explain the Normcore tamper to me? - Page 3

February 3rd, 2023, 1:57 pm

Primacog wrote:Thanka for your revuew. Do i understand correctly that you dont feel anything at all as you press down? So there is no feeling of hitting the bottom at any point nor is there any tactile response such as a click?

@MB said it perfectly: "You just press till you feel or see the handle bottom out against the part that sits on top of the basket. You can't push down any further and the motion stops at that point."

#22: Post by MB » February 3rd, 2023, 3:26 pm

LittleCoffee wrote:...So the idea that the Normcore helps you compress to the same pressure every time is utter nonsense - it's just no possible to do that. Sure maybe you can learn the feel of a certain amount of compression for your particular spring and try and achieve that every time, but that's really not that different to tamping a bog standard tamper and learning the feel in your arm for a particular pressure and doing that consistently every time...

I get what you are saying when the tamper is not pushed all the way down, but I don't believe it's intended to be pushed down partially or by feel. It looks like it's meant to be pushed down until it bottoms out, at which point the inner spring is compressed a specific amount against the compressed volume of coffee. So, if I'm using 16.5 grams of the same coffee each time, the pressure of the tamp is consistent. Obviously, it will change if the dose is different or maybe even for a different coffee, but it will be a new consistent pressure for that combination which is all I need for a dialed in coffee.

February 3rd, 2023, 3:33 pm

It looks like it's meant to be pushed down until it bottoms out, at which point the inner spring is compressed a specific amount against the compressed volume of coffee.

It's possible you right - I have no idea. I do know for sure though that the "25lbs spring" (sic) bottoms out at 40lbs - so if your goal is 25lbs, then that can't be done by bottoming out...

#24: Post by MB » February 3rd, 2023, 3:54 pm

Yeah, agreed. The first thing I did was switch to the lightest spring and lube it with Molycote 111 while I had it apart.

#25: Post by **RC27** » March 13th, 2023, 10:30 pm

Digging this topic back up quickly...

I've found the best way for me to achieve a consistent tamp with the Normcore V4 tamper is to ensure I stop just shy of "bottoming out". Logically, once the tamper bottoms out it's just like using a solid non-spring loaded tamper ie. you are no longer using the spring to apply pressure and the amount of weight applied while bottomed out varies depending on the amount you keep exerting, how quickly you back off etc. I tested this using bathroom scales - when just stopping shy I found peak tamp pressure was within 100g each time. Bottoming out was much more inconsistent and applied a number of kilograms more weight with a higher peak variation in my testing.

#26: Post by **BaristaMcBob** » March 13th, 2023, 10:54 pm

The guys at Barista Hustle published an excellent study of tamp force. Check it out - I'm sure it will answer your question.

https://www.baristahustle.com/blog/how ... -you-tamp/

#27: Post by **espressoren** » March 14th, 2023, 12:43 am

LittleCoffee wrote:
I'm not sure I follow your second point - for my Normcore medium spring (I can't bring myself to call it 25lb spring as that's a lie) the force needed to fully bottom out - i.e. compress it the maximum amount possible is about 40lb - so depending on how compressed my spring is I'm getting something between 0 or 40lbs.

Just as a quick example, a preloaded spring could be tuned to not even start to move until you apply 25lb. That by itself indicates that a preloaded spring can be tuned to operate within a smaller range of force than one might expect if the spring weren't preloaded.

With the dual spring action it's even more complicated because maybe just the handle is on the preloaded 25lb spring, pressing on the basket ridge. So the tamper doesn't even start pushing until you cross that force and then the tamper head itself is on a second spring and internal rod that is free floating and will retreat into the handle at pressures beyond 30lb like a prop knife. The primary spring itself is what moves the visible handle though and it bottoms out at 40lb while the internal one is applying a separate degree of pressure to the actual puck.

I'm not declaring that's precisely how these things work, I'm just trying to explain how the range of pressure a spring applies can be tuned. There are lots of examples of say 30cm long springs that are compressed into a tube and operate at a fairly constant pressure within a 5-10cm travel.

#28: Post by **espressoren** » March 14th, 2023, 12:52 am

RC27 wrote:Digging this topic back up quickly...

I've found the best way for me to achieve a consistent tamp with the Normcore V4 tamper is to ensure I stop just shy of "bottoming out". Logically, once the tamper bottoms out it's just like using a solid non-spring loaded tamper ie. you are no longer using the spring to apply pressure and the amount of weight applied while bottomed out varies depending on the amount you keep exerting, how quickly you back off etc. I tested this using bathroom scales - when just stopping shy I found peak tamp pressure was within 100g each time. Bottoming out was much more inconsistent and applied a number of kilograms more weight with a higher peak variation in my testing.

I don't know how much difference it makes but this seems non trivial to test accurately - say within 100g. You'd probably have to rig up something so the force applied to the part that sits on the basket is separated from the force of the part that rests on the puck. So you'd have to compress that outside ring without that force pressing on the scale. Or maybe you could estimate by just figuring that force separately and subtracting.

#29: Post by MB » March 14th, 2023, 1:35 am

RC27 wrote:Digging this topic back up quickly...

I've found the best way for me to achieve a consistent tamp with the Normcore V4 tamper is to ensure I stop just shy of "bottoming out". Logically, once the tamper bottoms out it's just like using a solid non-spring loaded tamper ie. you are no longer using the spring to apply pressure and the amount of weight applied while bottomed out varies depending on the amount you keep exerting, how quickly you back off etc. I tested this using bathroom scales - when just stopping shy I found peak tamp pressure was within 100g each time. Bottoming out was much more inconsistent and applied a number of kilograms more weight with a higher peak variation in my testing.

This is not how the force works. You get the most consistent tamp by bottoming out, because once you do that any extra force you apply beyond that is not transferred to the tamper base, it's applied to the rim of the basket. So, measuring it on a scale doesn't tell you the tamp force on the puck as you press harder after you bottom out. You could apply 50 lbs of pressure to the handle and the tamp will only apply the same limited force of the main spring once compressed between the bottomed out handle and the compressed puck face.

#30: Post by **RC27** » March 14th, 2023, 1:50 am

Yes thinking about it more, its not as straightforward as a quick test on a set of bathroom scales

I haven't had a chance to look at the design of the shaft but if it still has spring travel once the handle bottoms out against the levelling collar then that changes the equation also.