Steering Lock

steering lock - removing cross pin and clip

The Manurhin has a lock on the steering column - not for an ignition as might first appear (there is no ignition security key on a Manurhin) - its a steering lock.  Allegedly there should also be a lock on the drivers seat to restrict access to the petrol tank - but I don't appear to have one of these.

Obviously, my scooter doesn't have a key for the steering lock.  But fortunately the lock is not in the engaged position so the steering turns freely.
As I have been preparing the frame for powder-coating, getting the lock mechanism out seemed sensible even though I could probably get away with simply masking it off and leaving it in place.  Trouble is, its a real bugger to get out without a key.  I should have just left it, but it started to niggle me and I felt driven to investigate (especially as I wasn't prepared to spend what one locksmith quoted me to get it removed and fitted with a new key... £130!).  Over the period of several days I kept returning to this little puzzle wondering what on earth could be keeping it from sliding out.

Fellow Manurhin owner Roy had already told me about his own experience with removing his steering lock which resulted in drilling it out.  I was keen to avoid such destruction but was grateful to learn however that the lock is German-made by Neiman.  You can buy Neiman locks on eBay (though I cant find one to my exact dimensions) so I did a google search for "How to remove a Neiman lock", and turned up a couple of forums discussing this very problem (it seems I'm not the only person to have bought an old motorcycle with no keys)  Sadly though these discussions don't answer the problem completely so I was still in the dark as to how it operated.

marking where the restriction is.
Note there is no external pin or fitting here

The lock is very small; a mere 12mm diameter brass barrel and bolt, and it simply slides in a steel tube welded to the headstock of the scooter frame.  After removing a spring clip and a cross pin, I could slide the lock assembly laterally back and forth within the tube by about 6mm, but there was a dead stop that was preventing the barrel from removing fully.  Investigating with magnifying glass and mirrors down the headstock provided no clue as to what might hold the barrel in place - there was no obvious retention or lip.

To prove its free movement to myself I cut a long 3mm wide strip of Guinness beer can and carefully slid it between the brass barrel and the steel retaining tube.  I was able to push this thin strip all the way along the tube until I could see it pop out in the headstock tube - there was nothing in its way.  Withdrawing the strip, and repeating the process around the complete circumference of the lock barrel I was to discover that there was one place where (at about 1 O'clock) where the strip hit a restriction.

drilled out outer tube, and internal pin

The thing that puzzled me was that I could find no external evidence of a retaining pin and as the steel outer tube was no more than maybe 2mm thick, there surely wasn't going to be a stepped ridge.  However, I was now very intrigued, and as much as I didn't want to do anything destructive, I decided to drill a 5mm dia hole into the tube at the place where I had deduced the restriction to be.

Sure enough, drilling a hole in the external tube at this point revealed a pin in the brass barrel that once removed (drilled with a 2mm drill) allowed the barrel to slide easily out of the outer tube.

Once out, all became clear.
This is an incredibly simple design.  Simple but ingenious.
Once again, my assumptions about the engineering principles let me down; I had assumed that the outer tube was 1. simply a carrier or support for the lock mechanism - I would never have guessed that it was actually part of the lock mechanism, and 2. it was too small and skinny a piece of tube to have any integral machining done to it.

note the 2 grooves machined inside

A closer inspection inside this steel tube reveals that the inside wall has two machined grooves in it (remembering that this tube is 12mm ID with 2mm thick wall - this is an intricate bit of machining) and it is these grooves that the pin in the brass barrel/bolt engages with.
[apologies for the poor quality of photo - taken through a magnifying glass with flash - but hopefully you get the idea]

So I had settled my curiosity, and I can now send the frame off for powder-coating without fear of damaging the lock....... what a shame I damaged it by removing it :-(
I dont think I have done anything irreparable to the frame - though I am reluctant to weld that drill hole up now as this would certainly ruin the internal grooves.  Even with this hole, If I find a replacement barrel/bolt, it should still operate properly.

perhaps this hole can simply become a jolly big greasing point.

Just in case anyone is ever after a replacement steering lock.....