ABC gudgeon pin query

Looking through my dismantled 500 SIOE ABC this morning, I realised that
there is no apparent means of retaining the gudgeon pin in the piston. It is
quite small in diameter & has a flange on one end. The other end is plain.
It is a tight push fit into the piston, but not tight enough to make me a
happy puppy! The cast iron piston has different machining on either side of
the bosses.
There are no aluminium pads amongst the bits, the mortal remains of two
engines.
H-o-w-e-v-e-r ;o)) there is a long copper tube with a swaged end and the
other drilled out as though to remove swaging. It is quite thick walled
(more than petrol pipe) and is a perfect fit into the gudgeon pin. Has
anyone ever heard of this being done? It's a new one on me & obviously I
need to get this right as it will affect the balance & it is designed to run
at 3,600rpm.
formatting link

Regards,
Kim Siddorn
Reply to
kimsiddorn
Loading thread data ...
If it's that old, maybe it's just a poor design that was prone to loose pins and the copper pipe you have is a later retro-fit to fix this?
Reply to
Andy Dingley
Seen similar on a Scott engine (ISTR early Squirrel) where individual end pads were made of ally tube 'upset' into a mushroom shape - not a single tube going all the way through pin though. Does the swaging look good enough to be original?
BTW effect on balance will be less critical on flat twin than some layouts - just a tad more rocking couple if it's wrong.
NHH
Reply to
Nick H
The two ends of both gudgeon pin and the machining of the OD of the piston are different. I think that originally the pins were a light drive fit into the piston & that Andy is right that the copper tube is a fix when one came loose. There is only one with the four pistons I have. My plan is to get a couple of ali mushrooms turned up to suit - I only need two as it cannot escape being of a shouldered design. I base this theory on photos I have saved of two other engines that have appeared on e-bay in recent years. They were both stripped down & neither had this copper tube thingy.
The engine is in pretty good order internally - I'm going to try & put the rods & big ends on the crank tonight - but externally the ferrous bits have suffered very badly from corrosion & the inlet manifold needs remaking or at the least, some serious work. The exhaust system is long gone, but should be easy enough to re-create.
I had a new fuel/oil tank made by Frank Gelder utilising the old mounting brackets - very sturdy & fit for another 100 years! I'll take it along tomorrow & get a quote for a decent paint job from Brian our Chairman, a car body man of some note.
Regards,
Kim Siddorn
Reply to
kimsiddorn
Daughter passed her test on Saturday & took Hazel off for a celebratory drive! Therefore, I spent a constructive afternoon in the workshop with my 1915 ABC 500 twin. I've started to write this rebuild up for SEM now & here are the salient paragraphs from today - I apologise that they have a sentence or two of ground already covered here.
The box of bits contains the mortal remains of two engines & there is certainly enough to build one runner. One crank has had the mainshafts Diamond Hard Chromed back to size, so they must have been really badly pitted. There are four rods & pistons & a day was spent meticulously cleaning, wire brushing & selecting the best two of each. Only one showed serious rust pitting of the skirt and I'd use it if I had to as the pitting would simply retain oil better! All the rings were free and undamaged. They have diagonal ends, so I removed them with thin strips cut from a spray can as it hurt the pinkies too much to try & get them off the usual way. Finally, I selected the best rings & pistons, oiled & cleaned them all & removed a little staining.
Time now to assemble the crankshaft. The connecting rods are slim with huge big end eyes & assemble to the one-piece crank by threading them over the narrow crank throws. The 12 quarter inch rollers fit into the rod eyes readily enough and are retained in place by a floating two-piece collar that fits on the pin next to the rod and acts as a thrust washer. The mainshafts are keyed into the crank webs and have special thin nuts with concave faces on their hexagons. These fit closely against the floating collars and thus the nuts are secured from loosening without further attention. Very ingenious, Mr. Bradshaw!
Regards,
Kim Siddorn
Reply to
kimsiddorn

Site Timeline

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.