Londinium piston modification? - Page 3

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walt_in_hawaii

Postby walt_in_hawaii » Aug 09, 2018, 1:13 pm

Phaedrus wrote:Forgive my ignorance, but wasn't this solved on the L-R by using custom seals? Or is this an issue specifically with the L1? (Asking because I plan on getting an L-R someday)

Phaedrus, I wasn't willing to put down as much as a new LR would cost simply to scratch an itch. I already am very happy with my Strega.... the Londinium was purchased because I was curious to see if there was a palpable difference between the 2. I'm still evaluating, have to straighten out the seals before serious evaluation comparisons can be done. So don't ask. :)

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FotonDrv

Postby FotonDrv » Aug 09, 2018, 6:32 pm

I switched from stock seals, to Cafelat seal, back to "New stiffer" Londinium seals (did not like them as much because they were a PITA to get in place and they changed nothing), then back to Cafelat finally. Cafelat worked about the best but the Bosco silicone was just slightly stiffer but I noticed no performance difference in where the lever engaged. Most of the time I was getting about 20 degrees off of level from a fully pulled lever before engagement.

Cafelat seals are the best bang for the buck imo after owning 2 Londinium machines.
That Light at the End of the Tunnel is actually a train

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TomC
Team HB

Postby TomC » Aug 09, 2018, 6:55 pm

Paul Pratt and custom pistons! Reminds me of how awesome Paul Pratt is, and super helpful to the HB community :D

walt_in_hawaii

Postby walt_in_hawaii » Aug 09, 2018, 7:39 pm

Tom, I am much in agreement... Paul? Any way I could get some dimensions off you for those pistons? Would LOVE to machine one for myself...

walt_in_hawaii

Postby walt_in_hawaii » Aug 09, 2018, 7:56 pm

FotonDrv wrote:I switched from stock seals, to Cafelat seal, back to "New stiffer" Londinium seals (did not like them as much because they were a PITA to get in place and they changed nothing), then back to Cafelat finally. Cafelat worked about the best but the Bosco silicone was just slightly stiffer but I noticed no performance difference in where the lever engaged. Most of the time I was getting about 20 degrees off of level from a fully pulled lever before engagement.

Cafelat seals are the best bang for the buck imo after owning 2 Londinium machines.

Stephen, I know you do machining too. Did you think of trying a very thin delrin ring, maybe split along a diagonal, to put in under the silicon rings to give them a little help pushing outwards more? sort of like a less messy 'wrapping Teflon tape around the piston' solution that I saw on the londinium forum.

I just ordered a set of Sorrento seals this morning, it was said that they are a little stiffer than the cafelat. I'll be careful swapping them, though, looks like I may have to keep my cafelats. But I hope Paul answers....

mivanitsky

Postby mivanitsky » Aug 09, 2018, 8:15 pm

I wonder if Paul would consider selling single use licenses along with a copy of the necessary CNC files, for us to make our own, if he has no plans to make and sell them. He spent a lot of time in the project, and I'm sure more than a few of us would be happy to reward him for his efforts.

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FotonDrv

Postby FotonDrv » Aug 09, 2018, 8:15 pm

walt_in_hawaii wrote:Stephen, I know you do machining too. Did you think of trying a very thin delrin ring, maybe split along a diagonal, to put in under the silicon rings to give them a little help pushing outwards more? sort of like a less messy 'wrapping Teflon tape around the piston' solution that I saw on the londinium forum.

I just ordered a set of Sorrento seals this morning, it was said that they are a little stiffer than the cafelat. I'll be careful swapping them, though, looks like I may have to keep my cafelats. But I hope Paul answers....


I honestly had zero problems with the Cafelat seals so no shimming was necessary at all. Lubricate them properly and they will be good for a very long time. If any stuttering is noticed then clean and lube, do not replace.

I thought about machining off the top of the piston to make it possible to put the 4th seal on with a washer as the top cap for the seal, just the way Bosco does it, but eventually came up with why mess with it. Removing that piston, and therefore the spring, is not an easy thing. I have the tools but thought it an exercise for the sake of liking work not for improving anything.

The only problem I had with the Londinium machine was a poorly centered spring to cylinder wall alignment making for a rubbing noise. Once I got the spring centered properly the machine worked as well as a commercial Lever can work. Bosco adds the 4th seal and has the different water flow path to the Group which accounts for some shot/temperature differences in the Group.

What pressure you are running in the L-I?
That Light at the End of the Tunnel is actually a train

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FotonDrv

Postby FotonDrv » Aug 09, 2018, 8:16 pm

mivanitsky wrote:I wonder if Paul would consider selling single use licenses along with a copy of the necessary CNC files, for us to make our own, if he has no plans to make and sell them. He spent a lot of time in the project, and I'm sure more than a few of us would be happy to reward him for his efforts.


That is a good idea.
That Light at the End of the Tunnel is actually a train

greg-g

Postby greg-g » Aug 09, 2018, 8:21 pm

This has been discussed before.
Assuming the seals are perfect and there is no leakage past the seals, the height at which the lever grabs is almost totally dependent on the pre-infusion pressure.
When the lever is pulled down and just before the middle seal passes the water inlet holes, the piston chamber is full of air (Pulled up through the puck). When the middle seal passes the inlet holes the chamber will start to fill with water, but there will always be an air pocket at the top of the chamber. The higher the pre-infusion pressure the more this air pocket will be compressed.
The original L1 has a pre-infusion pressure equal to the boiler pressure which is normally about 1.2 - 1.4 bar. This pressure is the shutoff pressure for the Pressure Stat (PS). The switch on pressure for the PS will be lower. Giving the steam lever a quick flick will normally turn the PS on and bring the boiler up to maximum pressure.
The newer L1-R generally has the pre-infusion pressure at about 3 bar (user adjustable). This will therefore compress the air pocket to a smaller volume allowing more water in the chamber hence allowing the lever to catch at a lower position.
The Londinium lever initially exerts a pressure of about 9 bar when released. The lever movement between the fully down position and the catch position is proportional to the compression of the air pocket above the piston assuming no leakage past the bottom seal.
Personally, I'm using the genuine Londinium seal in the lower position that I generally find needs replacement every year. I'm still using the older type seal for the upper seals as they aren't as critical, and I had a stock of them.

Javier

Postby Javier » Aug 09, 2018, 8:27 pm

TomC wrote:Paul Pratt and custom pistons! Reminds me of how awesome Paul Pratt is, and super helpful to the HB community :D


+ 10000
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