What is the difference between a gear driven pump vs. rotary? - Page 3

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lagoon
Posts: 503
Joined: 14 years ago

#21: Post by lagoon »

The Rocket R91 uses a variable speed magnetic gear pump. I'm not sure who manufactures the pump though.

It's very responsive to the proportional paddle input and will quickly ramp up and down as required.

ira
Team HB
Posts: 5475
Joined: 16 years ago

#22: Post by ira »

Ah, learns something new every day. Since most of the gear pumps are magnetic driven I guessed slip would refer to the magnetic connection slipping. Never imagined that slip would be used to describe a slow leak.

Mike-R
Posts: 268
Joined: 14 years ago

#23: Post by Mike-R »

lagoon wrote:The Rocket R91 uses a variable speed magnetic gear pump. I'm not sure who manufactures the pump though.

It's very responsive to the proportional paddle input and will quickly ramp up and down as required.
I recently learned about R Nine One and I'm curious to know if they really use a gear pump. Rocket's website and literature never mention a "gear pump", they say they use a "permanent magnets volumetric pump". For example, see their brochure.

Volumetric pump is another word for positive displacement pump and includes gear, rotary vane and vibration pumps. For reference, see this Fluid-O-Tech webpage describing volumetric pumps.

When I looked up a replacement pump using the part number on the parts diagram, they are showing a Fluid-O-Tech GA Series pump, which is a vane pump. Not sure this replacement pump is really the correct one, though, because the replacement motor looks like the brushed motor option which the data sheet does not show as variable speed, although that doesn't necessarily mean it can't be used for variable speed.

Does anyone know any reliable references that confirm they use a gear pump?

Just to be clear, I don't think it matters whether they use a gear pump or vane pump. Both should work well for variable speed pressure control in an espresso maker. This is just intellectual curiosity.

Mike-R
Posts: 268
Joined: 14 years ago

#24: Post by Mike-R »

I'm starting to wonder if many (but not necessarily all) of the variable speed pumps used in espresso machines are actually rotary vane pumps. It's just a theory at this point, but I'm starting to gather evidence.

I already mentioned Rocket R Nine One in my previous reply. Now I found that the Sanremo You might be another one. Some people say it has a gear pump, but their brochure really only says "volumetric pump" which could be gear or rotary vane. In this video at 13:06, I can't see the model number but it sure looks like their using the Fluid-O-Tech GA Series Vane pump.

I believe the early use of variable speed pumps started with multigroup commerical models which expressly used gear pumps, and I wonder if this perhaps led many to assume that only gear pumps can be variable speed.

Once again, I don't think gear pumps are necessarily better performance than vane pumps for the application of variable speed pumps for pressure control in espresso machines. My musings about this are just intellectual curiosity.

Jrodanapolis
Posts: 147
Joined: 4 years ago

#25: Post by Jrodanapolis »

Hey, that's my video! Glad to see it made it over here. Inspired by the Chimera/Chiara projects, but wanted to figure everything out on my own as I recently took a new job in the electronics industry and had no experience with software/hardware/electronics just a few years ago. I've been working on this for about a year now... have always planned to make a post, but wanted to get it cleaned up a bit more before posting for everyone on HB.

I recently got the pump, power supply and flow meter mounted to a bracket and installed inside the machine. I also have my Lunar talking to the controller via Bluetooth, so I have the brew by weight functionality on top of the EMP/profiling. All of that can be seen in my most recent video below. PCBs are in the works to get the mess of wires cleaned up, as well as a bigger/better screen with a full UI.

The gear pump has been amazing and allows me to grind quite a bit finer than using a stock LMLM (I have two and end up going back and forth when the gear pump machine needs to be fixed... which happens a lot, haha). The peak pressure is very dependent on grind size, as expected. I have the pump software limited to run at a max of just over 3 volts if I remember correctly, which correlates to about 10 bar in the LMLM.

As others that inspired this project have said... once you go variable flow rate, you never go back!