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916 Rear Brake Question

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    916 Rear Brake Question

    Short story long, for those with a Ducati 916 rear wheel conversion who are using the stock Brembo P2 34 rear caliper, can you do a full rotation of the axle to adjust the chain without the caliper hitting the swingarm?

    The longer version is my projects move at a glacial rate, but I'm sticking a 916 rear wheel into my NT400 bike among other plans. I have made a sleeve for the Ducati hub that aligns the chain, and after first thinking I need another spacer I built a little jig to help measure and at the moment I'm happy the rear wheel is central (within tolerance). I've designed and machined a rear caliper hanger based on the 916 standard hanger and am just going through the issue fixing and finalising the design. The test fit with the caliper stops full rotation as it hits the top of the swing arm. I loose about 60 degrees of rotation. I have a couple of options, the first is to check with others who have the conversion if this is 'normal', or if there is something obvious with my design that I've not seen, or if I need to move the caliper mount up a couple of mm to clear the arm.

    So obligatory pictures of the design (version 0.1):



    And in the rig showing the problem, crude marks on the masking tape shows the rotation problem (hopefully):



    Suggestions or ridicule welcomed.

    #2
    Been a while since I put it on, and i'm not running that EXACT caliper, but am running a brembo p2 34... my bleeder/inlet holes are horizontal instead of vertical however. it's on bill's bracket.. and if I remember right, the hub would spin all the way round. someone else with a better memory may chime in though.. doesn't it only go 180deg with the stock setup? you may want to have a look at bill's posts on his hanger.

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      #3
      Thanks. Not sure what the original setup allows as that is buried somewhere at the back of the garage. But the more I think about it the more I think having a full rotation is the right thing to do. A quick(ish) redesign and I've shifted the caliper up by 3mm. I think 2mm will do it but that looks tight still so a bit extra I dont think will hurt. It doesnt look to different on the disk either so I think this is the way to go. Might look to make some swarf later this week...

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        #4
        Pretty sure the original setup is on the top 180⁰. Don't forget to be aware how chain adjustment affects geometry.

        Wwr's is offset on the bracket, it's not flat. I think there's a spacer between the rotor and hub too. I would really say take a look at his, maybe shoot him a message. Hell he may still have one he'd sell you, he makes seriously nice stuff.

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          #5
          Thanks. I understand that I need to make a chain guide as well, thats likely to be the next thing I look into.

          I think I've seen WWR's which is nice, but I've got the tools so want to try and make my own version, just because. Should make things interesting. I've made the sleeve for the hub which aligns the chain and after thinking I needed a spacer for the axle I knocked up a jig (no pictures, my welding is very much 'functional') and I think the centre line of the rim runs true +-0.5mm so am happy to progress without anything more using the 916 hub and axle.

          As for the bracket offset as it were I need to update my design to allow for the disc bolts, so the body at the hub is 12mm but the main bulk is 9mm as it needs to clear the bolts so the mounting points are 10mm. That might not make sense so I'll put some pictures up of versionv2 once its done. I'm currently arguing with fusion over a 3mm filet which I'm sure someone who knows what they are doing wouldnt have a problem with...

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            #6
            F360 can be tricky/picky with fillet blends. Sometimes, just blending slightly below desired width (I.e. - 2.98 instead of 3.00mm) will work. Other times, I will pick just the problem area (usually shows in red) and figure out the maximum blend allowed there, and then taper up/blend into the rest at 3mm.

            Hope that makes sense.

            WW/R
            Life is a journey, not a destination.

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              #7
              Yep that makes sense, thanks. I've just had another go (after another, and another, and another, and, well you get the picture) and I think I have it. I suspect it might have been some 'construction' lines that I'd drawn over or the order I extruded it, but I now have the filets I want. I had them before fine but when I made the change to allow for the disc bolt clearance it decided to not play nicely. I did experiment as to what size it would allow but I really wanted 3mm on the basis that I have a 6mm ball nose end mill already set up.

              Now hopefully I can get all the tool paths done and have a go at version 2 over the weekend.

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