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« Ultimo post da fountainbel il Giugno 13, 2024, 16:49:04 pm »
"Repair" of a Conway Stewart “Winston” FP
Never encountered such a poorly designed pen….
Hi all,
A few days ago a friend came in with his leaking CS Winston FP and asked for a repair.
This “looked” a nice and hefty OS piston filler, weighing 55 grams.
So I've expected no problems in getting the pen repaired.
Heated up the barrel threads to get the section out, un-screwing, pulling ….no succes
Putting the pen front in an US cleaner for 30 minutes@ 35°C, un-screwing, pulling no succes …
Started wiggling and pulling the section and finally the section seat came out the barrel .
Although I could only pull the section approximately 25mm out, I could see a thin convertor screwed and glued in the section end.
The convertor wall had a radial crack at the seam between the converter and the section, triggering the experienced leak
Heated up the section end and tried to unscrew the convertor, but as somewhat expected…. it broke.
OK, then I had to find another solution, but first I had to get the convertor out of the barrel.
No way to get the dammed convertor out, not from the front nor from the barrel end!
The male barrel blindcap threads being 9mm, and the protruding riffled filling knob being 7mm,I decided to enlarge the bore in the male filling knob threads 7.5mm.
No result , so I decided to make te bore to 9mm, removing the male threads completely, and finally I had the convertor out.
Inside the barrel there was a thick walled brass tube, being over the total length of the barrel, I could also see the bore was internally stepped .
After processing the barrel for 30min @ 35°C in the US cleaner, then heating up the brass pipe at the inside, I hoped I would to able to knock the brass bushing out of the barrel.
In vain…. the brass tube was permanently glued in the barrel.
So to the lathe : centering out the barrel perfectly and turning the diameter 7/11mm brass tube completely out.
Enlarging the bore in the brass bushing was no alternative, since a brass piston bore would corrode quickly when at contact with ink. ...
Using small diametrical passes I finally succeeded to get the bushing out and enlarged the bore to 11.2mm resulting in a perfect smooth piston bore.
Having my own screw piston filler design,I decided to implement my piston filler in the pen.
The filling knob of my filler being 14mm longer compared to the original blindcap , I’ve shortened the barrel with 14mm and provided the necessary M12x0.75mm threads in the barrel end to screw my piston filler in.
Not having the original acrylic I’ve made the new filling knob from hard rubber
Made an appropriate piston head with a 2.2mm thick O ring and installed my piston filler, perfect!
Made and installed an epoxy glued diameter 11.2 x 8.8mm transition ring in the barrel front and epoxy glued the section in.
Pen is filling royal 2.4ml of ink, worthy a pen of this size!
A serious upgrade compared to the silly 0.8ml the convertor could take !
Attached a picture of the repaired pen and the remaining parts of the original pen.
Took me over 11 hours of work, but both my friend and myself are very happy with the result !
During my work on the pen I was astonished seeing how poor and unnecessary complex this pen was designed...
CS clearly wanted a ”hefty" pen, being the only reason why they integrated the heavy brass bushing.
However due to the internally stepped bore, the brass bushing can only be installed/ glued in the barrel after the convertor is introduced in the barrel !
And only then the convertor can be screwed/ glued in the section!
Although I admit the pen is surely esthetically pleasing, I never encountered such a maintenance unfriendly, overcomplex and poor design.
Just my 2 Euro cents..
Best regards,
Francis Goossens
PS : After comparing the original barrel entry bore through which the convertor should be installed with the maximum diameter of the( GP )part off the convertor the convertor is effectively 0.03 mm larger in diameter, so could not be installed not removed from the front.
Could this have been caused by over time shrinkage of the acrylic also lightly deforming the brass bushing ?
I seriously doubt it...
Whatever, the barrel bore should have been made at least 0.3mm larger coping with this risk.
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