Over a year ago I posted instructions on how I have made one hole bullet shaped steam tips for La Pavoni machines.

La Pavoni steam tip - How I made one:

This morning I made one for the MCAL. I first computed the maximum size of hole that the tip should have so that the heater could produce enough steam for continuous use. After some calculation I decided to go with a #55 drill, diameter 1.321 mm. An online steam oriface program at

http://www.tlv.com/global/TI/calculator ... ifice.html

predicted that this diameter should pass about 1300 g/hr of steam at 1.2 bar. The plate on the bottom of the MCAL says 850 watts. Hvap for water at 120 degrees is 2.2028 kJ/gram. Thus 850 watts should be capable of producing 1425 g/hr of steam since there are 3600 seconds in an hour. There is some thermal loss, but this seems close to ideal.

One cannot take 6mm acorn (dome) nuts and drill them like some do for La Pavonis because the threads on La Pavoni machines are standard M6x1.0 but the ones on the MCAL, at least ones like mine, are M6x0.75. I wanted to have the tip threaded the whole length of the MCAL steam arm threads, and I did not want it to stick down too far so I made the rounded tip shorter than with the La Pavoni ones. Thus I had to be very careful when turning down the tip to a point after drilling it. Someone once said, "Remember if the i.d. be greater than the o.d. the hole is on the outside!"

When I finished I carefully washed all the machining oil off the tip and tried it out. The stock tip has 3 1.0 mm holes. I just enjoyed a cappuccino made with it! Remember to put Teflon tape around threads of steam tips whenever they are removed.

Do you find that the stock 3-hole system is too strong, or are you saying
that 1300 g/hr of steam at 1.2 bar is near what the stock tip puts out?

I ask as it sure seems like it steams very quickly for me (an odd thing to say,
as people usually want it to go faster). It seems like I am "cooking" the soy
milk very quickly.

I note that a lot of people plug up some holes, so adding one that is larger
is an interesting idea. How does the steaming compare to the stock unit?
Faster/slower/more control/better turbulance?

Thanks.

The three hole one is too weak. The hole diameters are only 1.0 mm. This results in too slow steam velocity to suit me. I drilled this one to 1.32 mm One of the problems with smaller diameter tips is that liquid water constantly condenses in them and restricts their effective diameter so that they tend to behave as if they were smaller than they really are. Liquid water has dramatically higher viscosity than vapour. I think I could have been able to have used the 1.397mm size drill, #54. (The strange number letter gauge system in which all the drills are weird dimensions is designed for doing things like this. The sizes rise in somewhat by percentage rather than evenly by dimension. Drills like this are sort of worthless without an entire set, however.)

If you have the size too large (or too many holes for the size) the heater cannot produce enough steam to maintain pressure and the pressure falls. That is why I did the calculations described in the initial post. I have experimented with this tip, the MCAL 850 watt heater indeed is capable of delivering continuous steam without the pressure falling.

The stock tip would be great with a 2000 watt heater and the holes bored out to 1.3 or so.

Also, I like the bullet shape because it draws air into the vapour stream better making better foam. Because of the larger diameter bore and less wall friction, it produces MORE steam than the stock and requires a bit more care to avoid flying milk.


Below is an image of the tip on the machine.

I used to love the 3-hole tip from the Elektras (I've sold both, MCAL and Semiauto ). I miss their steam. But in fact I usually steam 120-150ml of milk. I would be curious to see this 1-hole tip in action. Nice job!

I'm using a Silvia's arm (new version, with 1-hole tip) on the Achille, so less steam available (at 1 bar) as the boiler is smaller.

Márcio.

My MCAL's steam tip is soldered to the copper pipe. No single hole for me. I do have one of Careiro's extra springs though.

I always enjoy your posts and work Robert.
I liked seeing the lab scale in the background of your last photo too. Staying old school through and through.

I commonly make a "pseudo cappuccino" that contains mammoth amounts of cocoa powder. When I have guests that are "chocoholics" they always seem to demand more. This requires changing the normal cappuccino stoichiometry so that more milk and foam is required. This tip is wonderful for this because the foam tends to be finer, and less time is required for the whole procedure, since the steam delivery is calculated to be near the maximum possible without its pressure falling from the 850 watt element. I notice it makes a bit more noise than with the three hole tip.

(Recipe:

I mix 10 to 12 grams of dry powdered cocoa with a teaspoon of xylitol or sugar and about 1/8 tsp stevioside. (Stevioside is a powerful synergistic sweetener from a Peruvian plant.) You could just use a tablespoon or so of sugar. I add a small amount of milk and stir to get a thick paste.

In a steam picher I place 180 mL of milk. I steam it. The time to do this is less than it was with the stock tip, and I find the foam finer.

I have 16 grams of ground coffee ready, and pull the MCAL's lever twice into the chocolate sweetener mixture. I stir this. Then I pour the espresso-chocolate mixture into a large mug, and then pour in the foamed milk.)