The Updated Wiedemann Flow Control Paddle

At the time of publishing, the updated flow paddle featured in this article is available on select machines from Lelit and Profitec and will be made more widely available over time. If you don't see the paddle as an option on a machine you are interested in purchasing, please contact a member of our sales team.

Current Machines Include:

• Profitec Pro 500 PID
• Profitec DRIVE
• Lelit Mara X
• Lelit Bianca

Introduction

When it comes to innovations that have reinvigorated the home espresso scene, the E61 flow control device majorly impacted the trajectory of feature development on home machines and breathed new life into the E61 brew group. We’ll be taking a look at the device that started it all, and how we've worked with our friends at Wiedemann Manufaktur to design an elegant alternative to the commonly seen ball knob and oversized paddles that are currently available.

In modern times, machines like the Dalla Corte Mina and the upcoming Fellow Espresso Series 1 have taken the ability to control brew water flow rates to the nth degree with the inclusion of sophisticated digital controls. This momentum towards developing new means of flow rate control was undeniably spurred on by the overwhelming success of manual, group mounted flow control devices. So, we'll start with a brief look back in time to understand how this feature has come to dominate the market.

The History of the E61 Flow Control Device

Given the ubiquity of flow control devices on modern E61 group espresso machines, it might be hard to imagine a time when they weren’t everywhere. That time, as a matter of fact, was pre-2018 before the Lelit Bianca V2 burst onto the scene with its group mounted flow paddle. The Bianca was a sleeper hit of sorts and set off an arms race of sorts with multiple manufacturers working furiously to respond with devices of their own. Fortunately the groundwork for the device was laid back in the 1960s with the original patent filed by Carlo Ernesto Valente. This patent made it possible for multiple manufacturers to put their own spin on the design which was not owned exclusively by Lelit.

The technology is simple. The flow control device is essentially a valve that you install inside of the E61 group and the valve permits or restricts water flow from the group; what’s most important about the device is that it can be adjusted by hand while the pump is running. While there are many possibilities introduced by adding this kind of control, one of the simplest and most impactful benefits of adding the flow control device to a machine is unlocking the ability to pre-infuse coffees by reducing the flow rate of water coming out of the group.

Pre-Infusion

Prior to the introduction of flow control, there were only a few options for pre-infusing coffee on E61 prosumer machines. By far the most vaunted of these early options is line pressure pre-infusion which uses the line pressure from your home water line connection to gently push water into the portafilter rather than running the pump. Because water line pressure needs to be significantly reduced for use in espresso machines, line pressure pre-infusion is typically at or below 2 bar as opposed to the traditional 9 bar of pressure used for espresso extraction.

While this method works quite well, it came with the fairly steep precondition that the machine had to be able to plumb directly into a water line. This excluded essentially all vibration pump machines, meaning that only models on the higher end of the price spectrum could make use of this feature. Additionally, while line pressure pre-infusion was a very attractive feature, it was still limited in the sense that you could only pre-infuse at a fixed flow rate based on your home line. Through the introduction of flow control devices, any machine with an E61 group is capable of low flow pre-infusion, which is especially beneficial for models with vibration pumps.

Early Days and Designs

Lelit’s own paddle, while very innovative at the time, was inherently held back by its oversized design which to this day prevents it from making a complete 360° rotation. As a result, the device can’t be used to its full potential. Instead of being able to access the full range of flow rates achievable by the device, you have to set your desired range using a set screw in the back of the paddle and adjust the threaded post to your desired position based on how you want to brew. If you ever want to change your potential flow rates, the paddle needs to be removed, the valve adjusted, and then the paddle reseated and resecured.

In 2019 we partnered with Michael Hauck at ECM/Profitec to help him develop a flow control device that could be installed on their machines, in particular the Pro 700 and Synchronika. The original buzz around the topic was highlighted in an article from Howard Bryman at Daily Coffee News. The photo used in the article is actually of the original prototype design for the device that used a much larger knob similar in size to the brew lever knob from an E61 group. The unbranded gauge would also be updated for both brands to feature their respective logos. While the original design was functional, it had the same issue as the Lelit knob in that it couldn’t make a full 360° rotation and ultimately limited the utility of the device.

The prototype design wouldn’t last long, and after a handful of iterations, the current ball shaped design was settled on. If you’ve ever wondered why the flow control device looks the way it does or is shaped the way it is, the answer is simply “functionality.” By making it much smaller, it could be fully rotated without impacting the front of the panel of the machine and ultimately allowing home baristas to make full use of the possible flow rates.

Other Designs

After the launch and wild success of ECM’s flow control device, several other manufacturers created their own versions of the device. Quick Mill made theirs very similar with a small knob instead of a ball, but still capable of multiple complete rotations. Bezzera also designed their own flow control device, solving the rotation issue by simply making the device taller and angling the knob outward so it would clear the height of the panel.

Bezzera would later update the device itself to change the threading inside of the valve to make it far more sensitive. While it appears the same visually, internally the length of the needle was shortened so that a greater degree of flow rate change can be achieved with less movement. At the same time this means that you have to be more precise when making adjustments.

Our New Design

Over the last year we’ve worked with Wiedemann to create an updated flow control paddle that would retain the benefits of full 360° rotation but improve on the ergonomic and tactile experience. While ECM’s ball design does allow for full rotation, its small size can make it difficult for people with larger hands to manipulate the device without potentially touching the brew group. On the other hand, Bezzera’s design, while fully functional, is less subtle by comparison making it a bit more polarizing when it comes to aesthetics. Personally, I think the design really matches Bezzera’s style, but I get that it might not be popular with everyone.

Prototypes

We went through several iterations of the flow paddle design using a 3D printer to test various shapes and thicknesses to find one that worked best. The prototype CAD designs were created in-house and we extensively tested each one before settling on the design we liked best. Early versions experimented with different thicknesses but maintained a similar geometry to the final version.

The Final Design

Our paddle is significantly smaller than the Lelit design, meaning that it can rotate completely, but unlike the ECM design, your fingers are still protected from the metal by the full wood exterior. The paddle also fits over the entire metal post so it doesn’t distract from the design of each machine. Being a custom component from Wiedemann, the flow paddle is available in four wood species including Blackened Oak, Maple, Olive and Walnut so it matches with their robust assortment of custom machine components and premium accessories.

Using the flow paddle, I’ve found that personally, my preference is to pinch it between my thumb and forefinger when making smaller adjustments, and using my index finger to make a full rotation as needed.

Compatibility

At the time of writing this article, we can confirm that the new flow control paddle can be installed on flow control devices from the following manufacturers.

• Bezzera
• ECM
• Lelit
• Profitec

Based on our testing, the post used in the flow control device produced by Quick Mill is too short to be properly secured inside of the paddle.

Why Rotation Matters

I’ve mentioned rotation a few times in this article with the point being that flow rate is connected to how far open or closed the valve is. If the paddle on the device does not allow it to rotate completely, then you can’t utilize it to its full potential. That said, it’s also important to understand that flow rates on machines can vary by model and manufacturer. Using a precision scale that can measure within 1/10 of a gram can help you determine flow rate based on the position of the valve. We recommend closing the valve completely and taking measurements at every quarter turn and recording the results.

For reference, I’ve included some results from our own flow rate testing on popular machines from ECM and Profitec using their flow control devices to demonstrate the utility of being able to make complete rotations with the device.

Measuring Flow Rate

Our preferred process for measuring flow rates on machines is simple. Start by closing the valve so that no water can flow through the group. Then, remove the portafilter and perform the following steps:

1. Place a cup and scale underneath the brew group
2. Open the valve by ¼ of a turn
3. Raise the brew lever and run the pump for 10 seconds
4. Cut the pump and record the total weight of the water dispensed
5. Divide the total weight by 10
6. Repeat 5x times to ensure accuracy and record the average of the results
7. Repeat steps 1 - 6 until you have opened the valve completely

Once you’ve recorded all of the flow rates based on the valve position, you can determine how you want to install and orient that paddle on your machine. What I mean by this is that if you’re like me, you’ll most likely want the default position for the paddle to be facing forward at six o’clock like the portafilter. Now, it’s up to you to decide what flow rate you want that six o’clock position to be, whether it’s to have the valve fully closed, at the stock flow rate, or at some other value based on your preferences.

Wrapping Up

More than five years on, it's easy to see how flow control has become a staple of home espresso machines and established a solid foothold as a feature and not a fad. Having gotten in at the ground floor we are very pro-flow here at Whole Latte Love and our latest collaboration with Wiedemann and are excited to share this new paddle design with you. Within the last year, things have started to "heat up" when it comes to innovation in the E61 space, but for now I'm comfortable with saying that flow control is still the king in my book.

Photography by Grace Walker

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