Repair of broken 12v (4.5v) couplers

[Dread Pirate Rob]

As there is a thread on repairing 12v motors and one on couplers, I thought the old timers here might be interested in my technique for repairing 12v couplers. I'm sure this must have been tried before but I couldn't find any previous threads.

I turned the drill bits with my fingers but a quality drill should do even better. I worked my way up to the correct diameter through three different bits to avoid stressing the plastic, then shaved off the resulting lip with a sharp knife.

(Mandated Government Warning: Lego was harmed in the making of this post (but it was only technic)

Repair of Lego 12v and 4.5v train couplers by Canvas Rails, on Flickr

Repair of Lego 12v and 4.5v train couplers by Canvas Rails, on Flickr

Repair of Lego 12v and 4.5v train couplers by Canvas Rails, on Flickr

Repair of Lego 12v and 4.5v train couplers by Canvas Rails, on Flickr

Repair of Lego 12v and 4.5v train couplers by Canvas Rails, on Flickr

Repair of Lego 12v and 4.5v train couplers by Canvas Rails, on Flickr

Repair of Lego 12v and 4.5v train couplers by Canvas Rails, on Flickr

Repair of Lego 12v and 4.5v train couplers by Canvas Rails, on Flickr

[Andromeda]

Nice tutorial Pirate Rob ! How did you fix the new piece into the coupler? I would recommend welding it with a small drop of MEK.

[Dread Pirate Rob]

That a good idea. By slowly working up through my drill bit sizes I actually have a pretty tight fit and it doesn't move in the hole (it still rotates freely in the buffer assembly though). If they come loose due to long running at Brickexpo I shall follow your advice and hit it with the Kragle.

Cheers,

Rob

[dr_spock]

Nice fix.

I think you can use one of these to save cutting a Technic pin in half (ouch).

Also machine screw, washer and nut would work too but that's not purist.

[deraven]

I'm not a fan of harming Lego, but drastic measures to save 12v elements seems reasonable.

Wow- I'm impressed that you were able to cut that pin in half so well! Still have all you finger tips, I hope! A half-pin would probably be easier as dr_spock noted, but I think your result looks better in the end than that would. This is great little tutorial to have up here; nice contribution to the community!

[harnbak]

Clever fix! I should have known this before...

[Dread Pirate Rob]

Nice fix.

I think you can use one of these to save cutting a Technic pin in half (ouch).

Also machine screw, washer and nut would work too but that's not purist.

I'm not a fan of harming Lego, but drastic measures to save 12v elements seems reasonable.

Wow- I'm impressed that you were able to cut that pin in half so well! Still have all you finger tips, I hope! A half-pin would probably be easier as dr_spock noted, but I think your result looks better in the end than that would. This is great little tutorial to have up here; nice contribution to the community!

Dr Spock and Deraven you are correct, I should have just gone for the easy option. I just gave the half stud a try on my third broken coupler and it looks quite neat.*

Technic half pin by Canvas Rails, on Flickr

Now I also have an additional useful stud in a similar position to the one on top of the PF coupler.

This was not as drastic as the repair job on my unserviceable 12v point motor:)

I still have all of my fingers, but not for long at the rate I'm going. Don't tell the purists but there are two cut pins used on each side of my Emerald Night that I modified to run on 12v track geometry. Even the half pins are a fraction too long for this application so I cut full pins and inserted them from the inside so the cut is invisible.

Modified narrow emerald night by Canvas Rails, on Flickr

Clever fix! I should have known this before...

Yes, I'm sure someone must have done it before. It looks too obvious to be a new idea but I can't find photos or instructions anywhere.

*Self assessment only, not a peer reviewed comment.

[Younge]

I love all these little fixes for old parts. Keep them coming!!!

[zephyr1934]

Thanks for an excellent tutorial... and like the others, I am in awe of your ability to cut a full pin in half so cleanly. I will never approach you when you have an xacto knife in your hand (grin).

[peterab]

Dread Pirate Rob, that is a nice, clean looking repair job. I'm surprised the Sharpie looks so effective.

I would recommend welding it with a small drop of MEK.

For those in Australia; it is worth noting that MEK is a regulated substance since it can be used in the manufacture of drugs. It is generally unavailable here and may provoke questions if you try and find or import it. While MEK is the most effective glue for ABS there are other glues which will also melt ABS, notably some of the ones used for PVC pipes.

[dr_spock]

Dr Spock and Deraven you are correct, I should have just gone for the easy option. I just gave the half stud a try on my third broken coupler and it looks quite neat.*

*Self assessment only, not a peer reviewed comment.

Great. The safer alternative worked. People should use the half pin. Cut full pin at own risk. That should limiit your liability in case someone gets hurt chopping a pin in half.

[Dread Pirate Rob]

I love all these little fixes for old parts. Keep them coming!!!

For my next 12v trick, I will fix the excessively high price of a second hand 7750. No, sorry, I failed

Thanks for an excellent tutorial... and like the others, I am in awe of your ability to cut a full pin in half so cleanly. I will never approach you when you have an xacto knife in your hand (grin).

I practiced by removing the tops of champagn bottles with a saber

Dread Pirate Rob, that is a nice, clean looking repair job. I'm surprised the Sharpie looks so effective.

For those in Australia; it is worth noting that MEK is a regulated substance since it can be used in the manufacture of drugs. It is generally unavailable here and may provoke questions if you try and find or import it. While MEK is the most effective glue for ABS there are other glues which will also melt ABS, notably some of the ones used for PVC pipes.

MEK was such a useful glue. It was my go-to adhesive as a kid making Kibri kits. I don't know if it was the kits or the fumes but I remember it as a happy time in my life...

Great. The safer alternative worked. People should use the half pin. Cut full pin at own risk. That should limiit your liability in case someone gets hurt chopping a pin in half.

I'm less worried about litigation than being beaten in a dark alley by angry purists . Interesting where we all draw the line though, I will not paint bricks, yet I used a sharpie on a modified brick... I suppose double standards must be twice as good

I'll change my Government Health Warning to: Keep Calm and Pretend it is a Rare Piece You Have Never Seen Before.

[LEGO Train 12 Volts]

Great topic ...thanks for sharing!