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Technical & Reference Section => Tech and Restoration => Topic started by: oldschoolace on July 14, 2013, 04:30 PM
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Hey guys, i usually just crack on with these mad ideas but i thought i would do a build thread for this one as it will take a while to do and it would be good to get some opinion/input.
So the basic idea is a Mongoose/Redline style double clamp stem to fit a new school ride.
(http://i1182.photobucket.com/albums/x455/oldschoolace/dclampstem3_zps6cdf0925.jpg) (http://s1182.photobucket.com/user/oldschoolace/media/dclampstem3_zps6cdf0925.jpg.html)
The steerer clamp is internal with the slot facing forwards and the stainless steel plate will bolt down into it while the bar clamps bolt right through the plate and the 2 clamp halfs.
Im wondering whether to bolt the bar clamps from underneath the plate and tap the top piece so it appears boltless. What do you guys think?
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Bolting from underneath shouldn't be a prob providing the threads are ample to take the tightening torque.
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What will happen to the front end of the stem Clint when its tightened around the steer tube?
A normal rear slotted stem would allow movement in the metal when clamping but by going off tye drawing I cant quite see how it would work?......is the centre are independent from the rest?
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OG one's are like this Gav:
(http://www.radbmx.co.uk/archive/albums/r189/jjvh66/Parts%20Guide/Goldstem.jpg)
And yeah, deffo go for the underneath fixings - will look a ton better imho :daumenhoch:
Just re-read your post Gav, and you didn't need to see that pic ;D Looks like the bottom fixings independent at the clamping area.
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I'm hoping to use the same inner pinch principle as this Gav :daumenhoch:
(http://www.radbmx.co.uk/archive/albums/x163/dedmann3/b092d706.jpg)
If all else fails i could cut a dog leg on the end of the slot out to one side so the pinch travel would be the same as a normal stem
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Spen has/had a NS stem that looked a lot like that Clint
Was on his Knight Goose
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while i admire your inventive skills, i have to ask WHY? ???
On a new school bike it will look awful (just my view of course) there are so many gorgeous new school stems about for around £40 which i'm sure yours will cost twice as much to produce?
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Cheers Griff :daumenhoch:
Just had a look and its quite interesting. I was worried that the double clamps would set the bars too high as they have to sit on top of the steerer clamp section but it looks fine on Spens :)
It seems to toe in in this pic which looks a bit odd and i think it looks a bit clunky as the front half of the double clamps is thicker than the rear but its given me more inspiration to crack on with it :daumenhoch:
(http://www.chainreactioncycles.com/Images/Models/Full/19615-1.jpg)
(http://www.chainreactioncycles.com/Images/Models/Full/19615-3.jpg)
Pickle, if we asked why every time someone tried something new we wouldn't be the great nation we are/once were :daumenhoch:
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Got some time over lunch to knock up a rough model to try the pinch principle. It was struggling to pull up until i cut the fine notch between the pinch slot and what would be the front mounting bolt hole for the stainless steel plate.
(http://i1182.photobucket.com/albums/x455/oldschoolace/2013-07-15144536_zpsd7bcc104.jpg) (http://s1182.photobucket.com/user/oldschoolace/media/2013-07-15144536_zpsd7bcc104.jpg.html)
I think with the excess material removed it will pinch up fine but should i need to repeat the little notch it shouldn't affect the front bolt hole integrity or its thread. :daumenhoch:
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What about inserting an half mood woodruffe type key, so as you tighten, the key is forced onto the head tube pulling the body of the stem onto the fork steerer?
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(http://farm4.staticflickr.com/3702/9295690652_3fa1bbebce.jpg) (http://www.flickr.com/photos/johndub71/9295690652/)
test (http://www.flickr.com/photos/johndub71/9295690652/) by johndub71 (http://www.flickr.com/people/johndub71/), on Flickr
Not the best, but you get my idea?
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Cheers John :daumenhoch:
Yeah been thinking about a few mechanisms, wedges, keys etc. I'm trying to keep the design as simple as possible (i know that sound like a contradiction with an internal pinch)
The easiest option is to dog leg the pinch slot out to one side but i'm hoping 2 m8 bolts will be enough to pull up the very small amount needed to clamp the stem.
I actually managed to sheer off a stainless steel m6 bolt where the thread meets the straight section of shaft with my first attempt :shocked:
Expected the threads in the Ali to give way first... just goes to show how tough T6082 is i guess :daumenhoch:
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I just sold that stem for £15 to Sean (Stidds) as it was for a 1" diameter bar so couldn't grip o/s 7/8" bars :'(
The control tech stem was lush and the build quality ace so I was gonna get Steve Animal to weld a plate around the bars to increase the diameter but I didn't want to fook up the bars so I flogged it and went with a retro DK in the end.
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Thats a shame Spen, it does look like a quality bit on engineering :daumenhoch:
I guess you could have used a shim but its never the same really is it! :'(
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If your bolting from the bottom with the threads in the top part of the stem, simply machine the botton holes elongated so they can allow for the stem closing in closer at the front than behind :daumenhoch: