Headclip stem & crushed steerer tube
Gavin Gilbert
Posts: 4,019
Borrocks 
An engineering question for the collectors....I picked up a frame at Ripley this morning. It's a rather rare and very expensive mid 1930's bike. Building up this evening I have run into a nasty problem.
I can't fit the stem into the steerer tube - it's the correct size, but I suspect the clip has been overtightened without the stem in place and the tube has been deformed. As with most clippy steerer tubes, there is a cruciform cut in the tube the top of which is about 1/2" from the lip of the tube - i.e. the locknut sits just above this.
I can only advance the stem in as far as the top of the cut. There is no debris in the tube and I am using a light coating of copper grease. I don't want to force the stem in because it looks as if there is a slight deflection and I'm afraid of causing even worse damage.
At the moment I am at a loss of what to do. I have considered inserting the stem as far as it will go and then attempting to tease open the cruciform slot with a screwdriver - all in the hope that the clip will properly reform the cut when fastened.
The other solution would be to polish off a millimetres metal when I polish the stem ahead of replating - but then I would need to trust the polisher to get it right and in partlicular not to go too far or ovalise the thing.
Or of course I could stop playing around with old bikes and concentrate on building modern ones that fit together properly.... :?
Help chaps, I need support on this one
An engineering question for the collectors....I picked up a frame at Ripley this morning. It's a rather rare and very expensive mid 1930's bike. Building up this evening I have run into a nasty problem.
I can't fit the stem into the steerer tube - it's the correct size, but I suspect the clip has been overtightened without the stem in place and the tube has been deformed. As with most clippy steerer tubes, there is a cruciform cut in the tube the top of which is about 1/2" from the lip of the tube - i.e. the locknut sits just above this.
I can only advance the stem in as far as the top of the cut. There is no debris in the tube and I am using a light coating of copper grease. I don't want to force the stem in because it looks as if there is a slight deflection and I'm afraid of causing even worse damage.
At the moment I am at a loss of what to do. I have considered inserting the stem as far as it will go and then attempting to tease open the cruciform slot with a screwdriver - all in the hope that the clip will properly reform the cut when fastened.
The other solution would be to polish off a millimetres metal when I polish the stem ahead of replating - but then I would need to trust the polisher to get it right and in partlicular not to go too far or ovalise the thing.
Or of course I could stop playing around with old bikes and concentrate on building modern ones that fit together properly.... :?
Help chaps, I need support on this one
0
Comments
-
Gavin if you post me the forks and stem I will see what I can do. What is it?0
-
Hi Gavin,
I had the same problem with my 1937 Hetchins. Trying to ignore the remarkably thin wall of the headclip steerer tube I used a wedge type ITM quill stem to reshape it. Insert stem to appropriate depth, gently take up slack with expander bolt, twist stem from side to side. Repeat until headclip stem just fits....
This did the trick for my forks, however, I was dealing with a badly pitted, nothing to lose frame.
Good luck
AndrewAndrew Granger0 -
Gavin take your frame into any small engineering workshop and they will have an expanding parallel reamer which will leave your head tube round and only take a few minutes to sort out.Chris.
Classic Lightweight Bicycle group
http://www.flickr.com/groups/oldcycles_/
every year I find new hills on the same roads.0
