Gudegon pin circlips

[Boxprod]

Forgive me if I'm asking a VERY stupid question, but why are gudegon pin circlips usually plain wire - with or without tangs?
Every circlip elsewhere seems to be pressed out of steel sheet, I guess, with either internal or external "eyes" for our trusty circlip pliers.
But when it comes to the gudgeon pin, it's plain round wire, and if they don't have a tang and the piston doesn't have a small slot, they're almost impossible to remove without damage. Yes, I do understand that they shouldn't be re-used in case of disaster, but it does seem a bit primitive.
And what happened to teflon buttons - which were all the rage in racing car engines when I was younger?
Just asking...
Best wishes to all,
Peter.

[IanHood]

My understanding is that the slight taper that is typically found at the end of the gudgeon acts to more firmly seat the wire clip into its groove whenever there is any lateral force. That way, even is there is some minor wear in the groove, it will always be seated firmly, and there will never be any risk of the clip turning or chattering. A 'normal' circlip (i.e. with eyes) would transmit those lateral forces sideways and possibly wear the slot.

Ian

[blethermaskite]

Peter, As said above, the bevel end of the gudgeon pin traps the wire circlip in its groove as a failsafe when the pin moves side to side in the piston during running, this doesn't work with flat stamped 'eared' circlips which also can have the 'ears' fracture off during running causing piston and bore damage. Generally speaking 'wire' circlips are used in high performance engines, (if these wire circlips have ears they should be removed before fitting ). Most pistons that use them have a little slot to aid removal, it doesn't matter that you will ruin them, you are not going to use them again. Teflon buttons ????? sorry don't know.
Cheers, George

[Boxprod]

Thanks for the wisdom.
I completely understand the taper on the gudgeon pin pressing the round wire circlip into its groove.
Some digging into the internet about teflon button history reveals that folk who build Mini engines for racing still tend to use them:

For those who have lathes, it's easy to turn them up, so you don't find them listed as popular "tuning" parts.
But it also seems they are commonplace in old air-cooled VW engines.
I'll stop now!
Peter.

[blethermaskite]

Peter, very interesting......got to admit "never heard of these" I only wonder if they are for ;competition' use how long would they last in ordinary long term road use?
Cheers, George

[DBDBrian]

One more little point, re flat eyed circlips, there should be no radius on the end of the pin, so it make contact with the clip tight up to the grove.
Also most clips have a sharp edge on one side and a slight radius on the other if stamped out, it's good practice to install the clip with the sharp edge away from the pin, as it is then less likely to ride out of the grove.

[themoudie]

Aye Peter,

Nigel, if I remember correctly cautioned me against the use of Teflon buttons, but for the life of me I cannot remember "Why?". Eldert may also have experienced comment to make.

As for the extraction of earless circlips, sharp picks, a sharp slim straight screwdriver, of the type used for terminal blocks and needle nosed pliers, usually sends the wee blighter flying across the workshop.

Good health, Bill

[IanHood]

Bill,

If they are used in an engine that doesn't very efficiently filter oil (like ours), they can trap unfiltered particles in the teflon which then acts as a nice abrasive pad against the cylinder wall. A least that's what I've been told.

Ian

[themoudie]

Aye Ian,

Now, that rings bells! Thank you for the reminder.

Good health, Bill

[ranton_rambler]

My Rudge has brass buttons to locate the gudgeon pin. There’s been a recent discussion on VMCC forum about different materials for this purpose.