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PostPosted: Sun Apr 15, 2012 3:40 pm 
Dirt Disciple
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Joined: Sun Apr 15, 2012 2:41 pm
Posts: 39
Location: Aberdeen, UK
Hi All,

I've an X-lite/Raleigh Ti bike from ~1995 that has been in the garage for the last 10 years and is now getting some attention. I always loved the light frame so I'm bringing it into the 21st century with new XTR mechs and shifters, Raceface XC SL chainset, etc. Aiming for something ultralight for XC rides, and a bit retro mixed with ultra modern.

The only part I cannot easily upgrade is from vees to discs. There are one or two bolt-on options available which attach via an adjustable arm to the canti brake boss, but I've never liked the look of them and I'd be worried about the ti frame flexing at the single brake mount under load. I could weld to the frame, but this isn't the easiest, and it seems a shame to permanently mod the frame.

So this weekend I fired up the CAD on the laptop and designed a strong bolt-on IS disc bracket that clamps onto the drop-out and rear stays. It is designed to spread the load through the main tubes with a big footprint contact area, and also butts up onto the dropout for added support. It stiffens the whole lower corner, so frame flexing shouldn't be a problem. In aluminium the weight is 135g for this Mk1. It uses titanium M4 socket heads to clamp the halves together.

The hardest part has been sizing it to fit the stays in 3D space. I eventually resorted to a combination of vernier measuring and taking high-res pictures in 3 planes, then scaling the images to known dimensions and measuring the tube centres and X,Y,Z locations.

Before getting one machined I'm checking the fit - I have a 3D printer so I'm doing a 3D print run just now. It should be ready in the next few hours. If it turns out ok, I'll post a few pix so you can see how the project is progressing. And if it fits the frame perfectly, I might even do a quick ANSYS run and look to thin things a little to save a bit of weight on a Mk2 before machining one for real.

Its taken quite a few hours to get this far, and I'm not planning on doing other sizes just now. It is sized specifically for my own bike geometry, which is medium, but if it works would anyone else be interested in a bracket too? I've a pic below of the rear drop-out (sorry about the quality, it was taken just now on my phone).


Also, as part of the rebuild I will probably have some barn find components up for sale, assuming the above bracket works as planned:

Middleburn RS-DH 175mm cranks (in blue, good condition)
Pace RC36 EVO II 100mm carbon / magnesium forks (VGC)
Ultra rare Goldtec 8 speed aluminium and titanium rear cassette (mint condition. Trial ridden once for ~10 minutes so light chain marks only)
8-speed XT F&R mechs,XT vee brakes, XT vee levers, LX shifters

Cheers
Rae


Attachments:
File comment: Mk1 bracket
RY-001-1002a.jpg
RY-001-1002a.jpg [ 224.99 KiB | Viewed 1363 times ]
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 Post subject: Hot off the press
PostPosted: Sun Apr 15, 2012 4:46 pm 
Dirt Disciple
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Joined: Sun Apr 15, 2012 2:41 pm
Posts: 39
Location: Aberdeen, UK
Just finished on the machine


Attachments:
File comment: printed parts
3D Print.JPG
3D Print.JPG [ 251.53 KiB | Viewed 1341 times ]
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 Post subject:
PostPosted: Sun Apr 15, 2012 4:57 pm 
Retro Guru
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Joined: Sun Jan 11, 2009 10:50 pm
Posts: 612
Location: Lazy Town
Hi Rae, I'm really interested in your project. Keep posting what you do on it.
Regards


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 Post subject:
PostPosted: Sun Apr 15, 2012 5:18 pm 
retrobike rider
retrobike rider

Joined: Sat May 29, 2010 3:44 pm
Posts: 1508
Location: Leeds
I like the look of that and bearing in mind that most of the stress is going anti-clockwise and putting the component in compression there is room to loose some material.

If you need a road tester, i'm willing.


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 Post subject: The finished Mk1
PostPosted: Sun Apr 15, 2012 5:47 pm 
Dirt Disciple
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Joined: Sun Apr 15, 2012 2:41 pm
Posts: 39
Location: Aberdeen, UK
Here are a few pix of the finished clamp on the bike. I agree, the main supports are probably a bit too thick. I might shave some weight off there and instead add stiffening close to the axle.

The fit is near perfect on the geometry,which is surprising given that dimensions were scaled from pictures. A little bit of careful filing with the eng-blue on the finished article to get a perfect fit at the stays is probably all that is required to get the parts perfectly aligned.

Will post some pictures of the Mk2 design when it is finished.

Rae


Attachments:
Bracket Mk1.JPG
Bracket Mk1.JPG [ 291.03 KiB | Viewed 1305 times ]
Bracket - reverse.JPG
Bracket - reverse.JPG [ 432.98 KiB | Viewed 1305 times ]
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 Post subject:
PostPosted: Sun Apr 15, 2012 5:51 pm 
Old School Grand Master
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Joined: Tue Oct 04, 2011 4:15 pm
Posts: 3499
Location: Behind you with the duct tape pulled out.
Could you not make it single bolt on the end that hangs off the stay to give a more rounded smoother look. Be less like to collect stuff in the undergrowth.


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 Post subject:
PostPosted: Sun Apr 15, 2012 6:22 pm 
retrobike rider
retrobike rider

Joined: Sat May 29, 2010 3:44 pm
Posts: 1508
Location: Leeds
Like it, looks good and well designed.

Do not know whether the symmetry would be lost by putting a single bolt under chainstay, Mk1a?


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 Post subject:
PostPosted: Sun Apr 15, 2012 6:29 pm 
Old School Grand Master
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Joined: Tue Oct 04, 2011 4:15 pm
Posts: 3499
Location: Behind you with the duct tape pulled out.
I wasnt looking at the asthetics of it more practicality of use. I do like it looks a much more classy solution than those other adaptors that are around. Bravo keep up the work.


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 Post subject: Bolts
PostPosted: Sun Apr 15, 2012 6:40 pm 
Dirt Disciple
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Joined: Sun Apr 15, 2012 2:41 pm
Posts: 39
Location: Aberdeen, UK
Yep, I agree the bottom bolts could be tidied. In theory all the load is compression anyway, so bolts are probably overkill on the underside. I was worried though that the springy ti frame itself might flex and bend while cycling, which would break contact at the lower and put all the load through only the upper stay, hence clamping it on the lower too.

The quick and dirty FEA run is looking pretty good. Checking with 400kg / 4000N acting on the rotor bolts in the direction of rotation, when the clamp is preloaded up. Compression-only supports on the chain-stays and dropout. Grip at the rear wheel will be lost long before it sees 400kg, and it would probably bust a weld on the frame stay too, but the clamp itself is looking fine.

Rae


Attachments:
Clamp FEA.jpg
Clamp FEA.jpg [ 136.04 KiB | Viewed 1282 times ]


Last edited by Rae on Sun Apr 15, 2012 8:23 pm, edited 1 time in total.
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 Post subject:
PostPosted: Sun Apr 15, 2012 7:33 pm 
retrobike rider
retrobike rider

Joined: Thu Apr 17, 2008 1:24 am
Posts: 7563
Location: Manchester
Very interesting.
I think I have the same frame, but it's a large!


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