Ponte Vecchio Lusso piston removal - revisited

#1: Post by **mousetail** » January 27th, 2009, 8:11 am

Slightly weary of circus tricks with clamps and performing seals, I've come up with a different method of piston removal.

Essentially, it's a piece of 70mm x 45mm scrap wood cut to length and profiled to fit in place of the drip tray, with a hole drilled exactly under the centre of the group. Into said hole fits a threaded rod with a plastic end cap (also a piece of scrap found in the shed [not sure what it was originally]) and three nuts.

The top two nuts are tightened together to provide a bracing point and the third nut is threaded on loosely below. The rod then sits in the hole with a washer under the bottom nut.

Slotted back under the group, with one spanner or wrench on the top nuts, the bottom nut can be threaded with a second wrench/spanner down on to the washer so raising the rod up to support the piston.

Then it's a simple matter of removing the lever pins and lowering the piston by turning the bottom nut the other way in a controlled fashion. Replacement, as they say in all the best manuals, is achieved by reversing the procedure.

And IT WORKS! Presumably also would on other machines, mutatis mutandis.

#2: Post by **timo888** » January 27th, 2009, 8:33 am

Nice

I am going to clamp such an apparatus to the chassis of my Club! The black plastic disk looks like a bicycle hub's locknut protector.

#3: Post by **Quadrifoglio** » January 27th, 2009, 8:45 pm

Ditto on the "nice". The threaded assembly looks a lot like the threaded glides off of a bedframe or furniture.

#4: Post by **mousetail** » January 28th, 2009, 4:07 am

Quadrifoglio wrote: The threaded assembly looks a lot like the threaded glides off of a bedframe or furniture.

The black end cap is separate on mine, but it does look like a foot from something. Your idea looks much simpler and better.

#5: Post by HB » January 28th, 2009, 7:38 am

Bob, thanks for contributing your how-to, it's a smart, simple, and safe solution to removing the Lusso's piston for gasket replacement. I've added this thread to the FAQ and will link it from the review.

#6: Post by **espressme** » January 28th, 2009, 9:01 am

Great idea! It should also work for some other spring machines!
FWW
If you put the box end of the wrench over the nuts and around the threaded shaft you will have no problem getting the wrench placed correctly on the nut when you want to turn it. Do this prior to placing the assembly under the group.
Don't do this on a hard to fit copper water line!...... Don't ask!

Again Great Idea!!!
Cheers
-Richard

#7: Post by **grong** » January 31st, 2009, 12:10 pm

Very smart solution!

#8: Post by GB » January 31st, 2009, 12:20 pm

What an elegant idea and excellent solution for PVL spring compression.

However, IMO it is not the solution for all spring lever machines as others have considered. Allow me to explain, on the PVL the grouphead is directly attached to the frame via a front plate etc, and when using this fixture the spring compression load mostly translates to shear on the group head studs and a little frame flexing etc. No worries! But on my Ponte Vecchio Export using the same technique the same spring compression load I estimate translates to an extension load of about 2700 pound on the two boiler studs!

I do not mean to belittle mousetail's ingenuity. This is an excellent solution for the PVL and possibly other machines where the grouphead is directly attached to a bulkhead etc. But for machines like the PVE where the grouphead only attaches to a vertical boiler and the bottom of the boiler is bolted to the base with a couple of studs it is probably not a good solution.

Regards
Geoffrey

#9: Post by HB » January 31st, 2009, 1:42 pm

Hmm-m. I'm not a mechanical engineer, but the grouphead's mount safely distributes the downward force on the lever necessary to fully compress the spring for years without issue, so couldn't it safely withstand a fraction of the (opposite) force of the spring's return once every couple years? That is, the fixture only needs to compress the spring just enough to remove/insert the retention pin at the piston's at-rest position.

#10: Post by GB » February 1st, 2009, 8:04 am

Damn! In my previous post I made 2X error in my estimate of the loading of the bottom boiler studs on my Ponte Vecchio Export when using a screw jack to the compress the spring. Conceptually I think I am correct but the number is way off and much less alarming.

Maybe someone else can help here? What is needed is accurate calculations using actual spring compression data, and materials strength info etc to see if the loading on these studs is really a problem. As for the loading the same studs during normal lever use IMHO it is many times less than when using a screw jack. But I could be wrong!

My apologies to all
Geoffrey