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PostPosted: Tue Apr 17, 2012 10:35 am 
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I was about to suggest exactly the opposite :) If the adapter contacted the whole top edge of the dropout and the lower part of the seatstay it'd spread the load out more. As it is, everything's going into a fairly small area on the stay. I know it's shared across both stays but unless it's a perfect fit one's going to see more than the other. I think more surface area would be safer.

Here's the mount off my old Mountain Cycle Moho, which interlocked with the seat/chainstays and dropout and bolted into existing holes. The funny-shaped bit between the actual brake mount holes was an exact fit with the shape of the stay. Pic of it in place is a bit tiny, can't find a better one :(


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PostPosted: Wed Apr 18, 2012 1:14 pm 
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Keep us all informed , I'm sure you'll get some orders if the price isn't too steep, just need to find a frame now(could be Kona or Orange).
Matthew


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PostPosted: Thu Apr 19, 2012 7:49 pm 
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MikeD wrote:
Here's the mount off my old Mountain Cycle Moho, which interlocked with the seat/chainstays and dropout and bolted into existing holes. The funny-shaped bit between the actual brake mount holes was an exact fit with the shape of the stay. Pic of it in place is a bit tiny, can't find a better one :(


I want one of those for my Raleigh Special Products TI 19". Please? :D


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PostPosted: Fri Apr 20, 2012 10:06 am 
Dirt Disciple
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Location: Aberdeen, UK
Great idea to mount it in the droput. The square section stays on the Moho look massively stronger though compared to the spindly ti frame. I don't think the ti frame would have the same strength and I'd be worried about the ti frame flexing and busting welds. I'll have a go though sketching something up to see how it might look. The nice thing about the stay version is that it would probably fit on any size of ti frame because the dropouts are probably standard across the range.

Thinks are moving along with the Mk2. Pictures will be up shortly. A really good machine shop I work with has offered to machine a set as a favour, so I'm working just now on reducing weight and making it simpler to machine. Once I've got the 2D drawings done I'll make them available to others.

Also, if anyone wants to try a 3D printed prototype for size, PM me and I'll post a set out.
Cheers
Rae


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PostPosted: Fri Apr 20, 2012 5:35 pm 
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Hi Rae,

On the Raleigh's the dropout will be the same, but the seat stay angle will change in line with the size of the seat tube. There were 4 sizes. 16", 18", 20" and a mahoosive 22".

Then there's mine, 19" :lol:


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PostPosted: Fri Apr 20, 2012 8:44 pm 
Dirt Disciple
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Below is a simple Mk3 mount. It is intended that this can be retrofitted to any sized ti frame because it only engages with (and clamps to) the cutout in the dropout. The dropouts are supposed to be the same on all frame sizes. It might need a bit of filing to get a perfect fit on the stay - I can print off some 3D printed versions for others to check different frame sizes if required.

The big question though is will the small engagement area be sufficent? All the torque from braking will be going through a small cross-sectional area at the dropout. It may either shear the tab on the clamp or break the rear stay.

Comments and feedback appreciated :)

Rae


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Mk3 Bracket.jpg
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Mk3 Iso rear.jpg
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Mk3 Iso Rear 2.jpg
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PostPosted: Fri Apr 20, 2012 10:33 pm 
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Tidy :) I lack the knowledge to be sure if it'll work or not. Maybe a combination of the two? I do think the large contact area of that one along the seatstay is a good idea, but clamping around the stays to keep it in place looks like a good idea too.

Can you do FEA and stuff or am I getting carried away? :)

Wondering if it's worth you getting a "sacrificial" lightweight steel frame to try a mount on -- probably wouldn't tell you if it'd definitely work on the Ti but may well tell you if it definitely wouldn't...


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PostPosted: Sun Apr 29, 2012 4:45 pm 
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I'd just like to add that these calipers are made of aluminium and attached via two M5 or M6 bolts.

Look at this, it looks as though I could bend it in half by hand I just don't think the forces are as large as you're planning for, especially at the rear. here.


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PostPosted: Thu May 03, 2012 10:23 pm 
Dirt Disciple
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Thanks for the info. I'm planning on a few more tweaks to the design this weekend then hopefully sending it for machining. I'm opting for the clamp design - I think it will be stronger.

Meanwhile I've been working on the rest of the bike build. If you are interested there are some build pix here:

http://www.retrobike.co.uk/forum/viewtopic.php?t=199812

Rae


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