La San Marco single group lever

Posted on January 7th, 2016

converted La San Marco single group lever

Dual boiler, dual PID commercial lever beast!

This beast started out life as a La San Marco 85 series, single group volumetric heat exchanger. I bought it last year as a fixer upper, the boiler was over filling and it needed a general going over. 9 months or so later and it’s a very different machine to the one that came in!

Turns out the over filling problem was a fractured heat exchanger, so that ruled out keeping the machine conventional – the heat exchanger would have to be decommissioned, capped off and become part of the steam boiler volume – I didn’t like the chances of a successful repair.

At that point it became a total strip down, and while I had the bare chassis on the bench, I started playing around with the possibility of fitting a lever group that I had spare. With an extra cross member in the chassis, it would totally work! So, off to see my mate Gonz who worked his magic and welded in a cross piece to take half the group flange. The group was already fitted with cartridge heaters, from back in the days of the Quick Mill Achille testing with Talk Coffee, so why not take advantage of that? Then, why not add some extra precision with a dedicated brew boiler as well? Yep, it would fit with a bit of wrangling. I also adapted a small volume heat exchanger into the existing steam boiler to provide pre-heated water to the brew boiler. Serious overkill at this point but why the heck not?!

So, this ended up being the most advanced lever machine I’ve built to date, with a PID controlling the group and a PID controlling a dedicated brew boiler just behind it, temperature control is phenomenal. By tweaking the two set points, you can even control the shape of the traditional lever temperature profile.

The original boiler is slightly under-specced at 1700W, but it allows the total machine wattage to stay at approx. 10 amp draw, with 600W in the brew boiler and 200 in the group. It takes a while to reach 1.5 bar, the group is hot well before then – but is ready to go after 25 min approx. and steam pressure is never an issue due to the huge volume for a single group, and added insulation.

It’s plumbed in only, as the line pressure primes the brewing circuit and is used for pre-infusion. The spring installed in the group (new of course) generates 10 bar peak pressure. It’s a delight to use and pulls wonderful shots. I’m mad to sell it, but that’s the reality of running a business, I can’t hang on to everything!

Summary of work done:

solved issue with heat exchanger crack
entirely new brewing system – group, boiler, pre-heater, PID control X2.
new autofill controller, SSRs, wiring as required.
rebuilt all existing valves, plumbing.
powdercoat exterior panels in electric blue hammertone (bold, I know, but it looks stunning!)

It’s probably the most advanced lever machine in the world, in terms of temperature control (at the time of writing – 2016). Offers will be considered. I am in the process of finalising fitment of the front panel, as it was never intended to cover a lever group. Once that’s done she’s ready to go, will not take me long!

Linea Mini paddle modification

Posted on January 6th, 2016

La Marzocco Linea Mini paddle modification

enabling the true function of the Manual Paddle

As usual, there are aspects of any piece of equipment that can be improved. My main gripe with the Linea Mini is that as standard, the paddle switch is not a ‘real’ paddle switch.

Let me explain – the original MP ‘mechanical paddle’ group is much loved by baristas for the control it allows over the pre-infusion phase of espresso brewing. The mechanical nature of the group allows the water flow to be turned on first at a lower, or ‘line’ pressure – this is simply the water pressure present in the mains and through the boiler/group, usually around 3 Bar. When the paddle reaches the end of it’s travel, the pump is engaged, and full brewing pressure (around 9 bar) is applied to the coffee. This two stage operation allows a skilled barista to perfect each shot by allowing the most critical first stage, where we want an even saturation of the coffee bed, to happen at a lower pressure. This improves the chances of the coffee puck saturating evenly, giving us a tastier shot.

So, a Mechanical Paddle group is a good thing in terms of control, but, being mechanical, there is a down side. It’s relatively complex to make and thus expensive, and, requires fairly regular replacement of o-ring seals. La Marzocco chose to fit a paddle switch to the Linea Mini, but the important distinction here is that it does not operate a mechanical valve, but a single microswitch which engages the water flow and the pump, practically simultaneously. Thus, the ethos of the paddle is lost because there is no first stage. It doesn’t matter how you move it, quickly or slowly, the result is the same. All this is not to say that it doesn’t work – clearly it does, and well, we just lose out on control over the infusion process. Perhaps La Marzocco chose this for reasons of simplicity – my argument would be all well and good, but if there is a paddle switch present, the expectation is that it works like a real one.

Well, we can make that happen! On the pump outlet I’ve added an extra solenoid with an adjustable needle valve, that is switched on as soon as the paddle is out of it’s stop position. This allows the first stage of the paddle’s movement to replicate the line pressure stage of a mechanical paddle group. In fact, the pressure can be set internally by adjusting the needle valve setting to give whatever pressure is desired for the pre-infusion phase.

Then when the standard microswitch is engaged mid-way through the travel, the bypass solenoid is switched off and the pump comes to full pressure. In addition I’ve added a spring loaded pre-infusion cylinder to the group to further soften out the pressure ramp-up and decline. The group pressure control ends up being a hybrid of Slayer, Kees van der Westen Speedster and La Marzocco Mechanical Paddle – with the best of all worlds. All electric, no seals to replace and fully adjustable. I’m very happy with the result!

Summary of the modification:

two-stage operation with adjustable ‘line’ pressure
spring-loaded chamber further smooths out pressure ramp-up
All electric, no seals to wear out
works in tank mode or plumbed in, with adjustment of needle valve accordingly
hybrid of Slayer, Speedster and La Marzocco pre-infusion systems
paddle action refined for perfect smoothness and feel

At this stage the installed modification is only available for machines brought to my workshop, and there are no plans to distribute a kit as modifications of factory parts, plumbing and electrical connections are required. If you are confident to handle this work as a DIY install, please contact me for pricing and availability. Alternatively you could contact a trusted technician local to you to perform the install work with my instructions. The modification is available for both 230V and 110V machines.

SOLD – Bo-Ema single group lever

Posted on November 23rd, 2014

SOLD – Bo-Ema A3

single group commercial lever

For sale as a completed project is my Bo Ema lever machine from the late 60’s, made in Revesby, Sydney. This is one of the only two single group machines I have ever seen, and has been restored to better than new condition.

Starting with a powdercoat for the aluminium base, this machine has been fully rebuilt with new seals and gaskets, and functionally improved with an autofill controller and solenoid valve, plus a modern pressurestat/SSR combo for perfect reliability. It’s had a new element, new group spring, new boiler insulation, new paintwork, new gauge, new tap handles and many other practical improvements, all together totalling roughly 100 hours of labour.

The final touch is a thorough bench test to fine tune pressure and temperature characteristics, this machine behaves exactly as a big commercial dipper style lever group should, with effortless consistent pours back to back once everything is properly warmed up.

If you’ve been looking for a vintage lever that’s ready for a new lifetime of service, this might be the one. Get in touch to arrange a demo if you are interested.

This is a 10 amp (standard household power) machine and requires a plumbed mains water supply or flo-jet pump and drainage.

SOLD