Restoring An Mb 146G (1950S) - My Journey

[slippery when wet]

Hello slippery. Hope you're well.

 

I'm not clear why friction would be needed? When the piston unit is removed and out of the pen, both stages of the piston work, ie it fully extends and fully retracts, without any external friction. Why would it be different when fitted in the barrel?

 

Just wondering.

Regards, CS

I was only referring to when the piston retracts, I've had an occasion when the piston would not retract without the section being screwed in and the piston extended fully against the backside of the section shoulder (in axial plane), happened twice while I seviced a couple of my pens, may not always be the case though, I also recall Francis saying something similar (don't quote me on this)

[CS388]

I was only referring to when the piston retracts, I've had an occasion when the piston would not retract without the section being screwed in and the piston extended fully against the backside of the section shoulder (in axial plane), happened twice while I seviced a couple of my pens, may not always be the case though, I also recall Francis saying something similar (don't quote me on this)

 

Ah, I see.

 

Thanks.

[fountainbel]

I was only referring to when the piston retracts, I've had an occasion when the piston would not retract without the section being screwed in and the piston extended fully against the backside of the section shoulder (in axial plane), happened twice while I seviced a couple of my pens, may not always be the case though, I also recall Francis saying something similar (don't quote me on this)

 

Exactly !

Given the radial pretension of the cork considerably increases the actuating torque , the slipping clutch inside the filling knob should be properly "armed" by "backing-up" the piston cork enclosure nut against the section, ensuring the full 2 stage retraction stroke .

When the radial pretension of the cork seal in the barrel is at the low side backing-up may not be needed.

However if the radial pretension is at the higher side backing up is always necessary

Personally I always make my cork seals with a radial pretension of 0.15-0.2mm , the finished cork being minimally 0.15 mm larger as the barrel bore, maximally 0.2 mm.

I make the cork seals as such ensuring the cork seal can cope with lengthwise diameter variations and ovality of the barrel bore, problems which are both triggered by irregular shrinkage of the celluloid .

Hope this clarifies the matter !

Francis

[siamackz]

This is the tool I use to remove a 146 piston

I saw this on a website. It says it does not engage the hole in the piston as the hole is not meant to be engaged. How does this tool work then?

[slippery when wet]

 

Please keep in mind this jig is designed for a 1950's 146 and not the 136 in the photo, it basically clamps around the metal shoulder to the piston, it has the exact tolerance for it to grip firmly without slipping or damaging the shoulder.

This is my own jig, tried looking for a thread where I show it with the correct pen but discovered my content only goes back to December 2016 which means I can't access a lot of my earlier stuff

[slippery when wet]

Exactly !

Given the radial pretension of the cork considerably increases the actuating torque , the slipping clutch inside the filling knob should be properly "armed" by "backing-up" the piston cork enclosure nut against the section, ensuring the full 2 stage retraction stroke .

When the radial pretension of the cork seal in the barrel is at the low side backing-up may not be needed.

However if the radial pretension is at the higher side backing up is always necessary

Personally I always make my cork seals with a radial pretension of 0.15-0.2mm , the finished cork being minimally 0.15 mm larger as the barrel bore, maximally 0.2 mm.

I make the cork seals as such ensuring the cork seal can cope with lengthwise diameter variations and ovality of the barrel bore, problems which are both triggered by irregular shrinkage of the celluloid .

Hope this clarifies the matter !

Francis

"Armed" and "backing up" perfect words to describe what takes place , well done Francis

[hari317]

Tried this, but the piston still doesnt engage both phases - only one phase seems to be working. The other phase just has the blind cap turning but no movement of the piston.

 

I guess I will need to open the piston up. My tool came in but its not what I needed. Will need to order something else.

 

Ill report back after I have the right tools!

my recommendation at this stage is to send off the pen to a pro like Francis, or Max or Tom. Repair of the filler might require removal of knob from the filler unit, special tooling and depending on why the second stage is not working, some metalwork repair reconstruction to actually remake some component parts.

[siamackz]

 

Please keep in mind this jig is designed for a 1950's 146 and not the 136 in the photo, it basically clamps around the metal shoulder to the piston, it has the exact tolerance for it to grip firmly without slipping or damaging the shoulder.

This is my own jig, tried looking for a thread where I show it with the correct pen but discovered my content only goes back to December 2016 which means I can't access a lot of my earlier stuff

Would a bionic wrench do essentially the same thing then? Something like:

[siamackz]

my recommendation at this stage is to send off the pen to a pro like Francis, or Max or Tom. Repair of the filler might require removal of knob from the filler unit, special tooling and depending on why the second stage is not working, some metalwork repair reconstruction to actually remake some component parts.

This is wise, of course. I have connected with Francis at the outset and told him that if I am out of my depth with this restoration then I will surely request him to save the pen. Being the kind person he is, he has been offering advice and cheering on thus far.

 

To me, the significance in this pen is restoring it, more than merely owning it. I will open it open with some tools. If there is a part missing or broken, then I will send it off the Francis. However, I want to assess the challenge first. Even with only one stage working, the pen can function sufficiently well. So, there is no hurry to fix it back to 100% now that I can access the cork and replace it.

 

This is the ultimate project pen for me, so I'm going to persevere a little more...

 

Your continuing advice will be of great help

[slippery when wet]

Would a bionic wrench do essentially the same thing then? Something like:

I couldn't say with out seeing it first hand, it needs to fit into the space created when the filler knob is fully extended

[siamackz]

I couldn't say with out seeing it first hand, it needs to fit into the space created when the filler knob is fully extended

I will be receiving it soon, so will report back.

[hari317]

I have the smallest 6 inch version of the loggerhead tools bionic wrench. It closes to around 6-7mm diameter minimum. I don't remember the OD of the filler tube offhand, so I am not sure if it is larger than 7mm so that the wrench is able to grip it reliably.

I'd be worried about deforming the filler tube if gripped there or the shoulder trim ring if gripped there when a bionic wrench is used. With a bionic wrench the only end stop is provided by the work piece being gripped, and if it is compliant, it will deform.

Maybe you can explore modifying an ordinary C-spanner, thinning it suitably and drilling one jaw and passing a 1mm drill bit shank through it as the driving element.

[slippery when wet]

I appluad your courage for giving it a go, but please always apply the gentlest of pressure, never force otherwise breakage will occur and instead of discussing "how to" we will be talking about who's the most capable of fixing your pen.Just a side note, I have pulled about half a dozen 2 stage pistons and never needed to heat the celluloid, this is not a recommendation though

[slippery when wet]

My jigs overall thickness is 4.5mm part of which sits over the shoulder ring , without a 146 it's a bit tricky providing exact details and I remember it fitting into the space snuggly

[siamackz]

Hari, good idea about the c spanner. Im going to gsend be that a go.

 

Slippery, I will definitely keep your advice in mind

[fountainbel]

I appluad your courage for giving it a go, but please always apply the gentlest of pressure, never force otherwise breakage will occur and instead of discussing "how to" we will be talking about who's the most capable of fixing your pen.Just a side note, I have pulled about half a dozen 2 stage pistons and never needed to heat the celluloid, this is not a recommendation though

 

Montblanc always secured the telescopic fillers with a sealing kit in the barrel.

Unnecessarily, but they most probably they did so avoiding unqualified - non Montblanc - repairers would start working on their pens.

This kit became stone hard during the 60 years since the filler was installed.

So if the filler was never taken out since its initial installation, heating up the filler is neccesary in my experience, surely if your tool does not feature a 1mm transversal pin which engages in the filler housing vent hole.

Just my 2 (Euro) cents…

Wishing you succes !

francis

[hari317]

Hari, good idea about the c spanner. Im going to gsend be that a go.

 

Slippery, I will definitely keep your advice in mind

The filler tube OD is approx 7.18 mm. A 7 mm wrench can be used as a starting point for your tool. It is easily available at most hardware shops in Bombay.

[siamackz]

The filler tube OD is approx 7.18 mm. A 7 mm wrench can be used as a starting point for your tool. It is easily available at most hardware shops in Bombay.

Yup, will keep this in mind. And then drill a 1mm hole. Im travelling at present, but will sort this out as soon as Im back

[siamackz]

Update:

 

The piston came out. I put blue tac on the celluloid part of the blind cap and on the barrel. Then I heated only the metal piston on high. There was so much glue when I opened it up that it would have been virtually impossible to open without heating. Here's the tool I used:

 

I cleaned up the piston, it was full of gunk! But the problem persists. See pictures 1-3 below. They show how the first stage does not move the piston, only the second stage does. So, what do I do next?

 

Edited December 10, 2017 by siamackz

[fountainbel]

The picture on the right side shows the filler only at the end of the first telescopic stage, in fact the second stage still has to start at this moment.

Not sure, but I expect the female threads of the large screw spindle - which is generating the second telescopic stage - are seriuosly worn or stripped.

This female secondary thread is cut at the entry of the smallest tube ,on which the piston seat is mounted at the other side.

The secondary stage threads are rather weak and sensible to wear out when movement is forced in case the piston is contaminated.

You can test easily if these threads are effectively stripped : screw the piston out as shown on your "Opened 2nd stage" picture, and then pull on the cork seat out.

In case you are able to pull the second stage fully out the threads are effectivly stripped .

Francis