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  1. #1
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    spiderless chainring - open source

    Hi guys,

    spiderless chainring - open source-snap2.jpg

    After reading all this drama with the only two companies (names withheld) around not delivering product, I'm taking the initiative to get a spiderless chainring made myself.

    I need your help to figure out optimum thicknesses, materials, etc. Can I get away without machining? i.e. water/laser/plasma cut plate? Then what thickness - 2.5mm? Anyone have experience with FEA/stress calcs to figure out how wide the ribs should be? If someone can make some measurements/scan of a functional ring, that'd be a good starting point.

    Thanks!

    cheers
    dave

  2. #2
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    Hiya, can someone do a bunch of work for me?

    kthxbye!

  3. #3
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    Quote Originally Posted by fotu View Post
    Hiya, can someone do a bunch of work for me?

    kthxbye!
    I actually had beer come out my nose from laughter. Thanks!

  4. #4
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    Sorry, I guess that came across wrong.

    I did label the post 'open source', and I'm still doing the legwork to get the spline and gear pattern correct, source the material, find a supplier to cut the parts, etc. I just don't have any experience with stress analysis, that's all. I'd post the final specs then you guys can tweak/source your own rings!

  5. #5
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    Stress analysis is expensive and for something like a ring it is a total waste of time and money.

    Just build it stronger then it needs to be and it will be fine. A ring needs to be pretty strong for handling log crossing and such so it is better to make it slightly beefy. Start with a weight budget and then use your CAD software to calculate weight of the part given the density of aluminum. A strong ring should have strong arms for the spider that is not there. Your current design is pretty good but I would recommend the arms be thicker and wider at the base.

    If your aim is to build the lightest chainring in the world start with something super crazy light and then replace them under warranty each time they fail with a slightly heavier version. For single speed a super light chainring will ride just fine until you try a log crossing. You could even go silly light but it will not save much weight when you factor in the complete weight of bike, rider, and his/her spare tire.

  6. #6
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    I think I'd cheat. There are lots of pictures of spiderless chain rings here. If you know how many teeth they have, you know the diameter of the chain ring. You should be able to scale the other important dimensions from the pictures, close enough.
    I would assume you want them made from flat plate to keep the cost down. The thickness of the root of the tooth will determine the thickness of the plate, more or less. You can check ordinary chain rings for that.
    They will need to go on a lathe for a quick cut to add the taper on the teeth.
    I'm no engineer but I think the biggest problem is going to be tolerance stacking of the spline with laser/plasma/water cutting. You might need a custom broach made to clean up the spline.
    You'll need to talk to the shop to see what they say.
    You could get a couple of prototypes 3D printed to check fit etc.
    Need to research types of aluminum and heat treating.

  7. #7
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    Not aluminum. Ti.

  8. #8
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    Quote Originally Posted by cdn-dave View Post
    Hi guys,

    Click image for larger version. 

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    I need your help to figure out optimum thicknesses, materials, etc. Can I get away without machining? i.e. water/laser/plasma cut plate? Then what thickness - 2.5mm? Anyone have experience with FEA/stress calcs to figure out how wide the ribs should be? If someone can make some measurements/scan of a functional ring, that'd be a good starting point.
    Material: 7075 T6 is pretty standard for chainrings because of the alloy characteristic with heat treating. Its hard (handles wear really well) stiff and durable while being reasonably light.

    As far as design goes. I would honestly go with at least 6 spokes, it will raise the stiffness considerably. Especially since the clamping surface is relying on 3 small screws on the backside of the crank.

    You can get away without cutting material out, but it will be worthwhile if you plan on selling them or making more than 10 rings..people do care about weight. Also, if you're creative enough, you can use the milled out sections for cool stuff like bottle openers and such....scrap = revenue.

    No FEA/stress calculations needed. All you need is the crank and spider, and take measurements using a caliper. If you are going to make it right, you might as well have that anyways....there is no other way of telling if it will actually fit or works if you don't! I wouldn't ask other people for those measurements if you are going to go through the work of getting the material, setting up the CNC and making a cut. You better d@mn well know it is right before you turn a machine on or you are just wasting time and money down the drain. So having the crank will be 100% necessary.

    Outside of that, if you know what you're doing, and make a quality product with a decent order completion time, you stand to make a lot of coin!
    Ibis Ripley LS
    Intense Spider 29 C
    Cervelo S2
    Trek Boone 5 Disc
    Spech Tricross Expert
    Raleigh RX 1.0

  9. #9
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    If your aim is to build the lightest chainring in the world start with something super crazy light
    Nah, just don't want it to fold on my first ride out!

    There are lots of pictures of spiderless chain rings here. If you know how many teeth they have, you know the diameter of the chain ring.
    Mountain Racing Products home of MRP, White Brothers, Kreitler, Tamer, and Power Grips | MRP Bling Ring Chainrings

    Not aluminum. Ti.
    I like your thinking!

    As far as design goes. I would honestly go with at least 6 spokes, it will raise the stiffness considerably. Especially since the clamping surface is relying on 3 small screws on the backside of the crank.

    ---snip--

    No FEA/stress calculations needed. All you need is the crank and spider, and take measurements using a caliper. If you are going to make it right, you might as well have that anyways....there is no other way of telling if it will actually fit or works if you don't! I wouldn't ask other people for those measurements if you are going to go through the work of getting the material, setting up the CNC and making a cut.
    Thanks for the tips! At least with my Shimano crank, it's all spline with a lockring holding the ring on, that's carrying the load (no screws...SRAM, right?). I'm also not planning to do any CNC work at all, and keep the lathe work to a minimum. Looks like since the base thickness is 3mm and the tooth thickness is 2mm, I'll have some to do though.

    Outside of that, if you know what you're doing, and make a quality product with a decent order completion time, you stand to make a lot of coin!
    Well I hope I know what I'm doing, but the last thing I have in mind is to go into business with this (rough crowd out there eh...)! If/when it works I'll post the files and you guys can shop it all out OR I'd do it for the heck of it and as thanks for the helpful input

    Here's the latest update. Let me know if anyone wants the cad file.
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    Last edited by cdn-dave; 11-18-2012 at 04:01 AM. Reason: added pic

  10. #10
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    Update: first laser cutter I spoke to quoted 95 euros for 2 rings, 2.5mm thick 6061 Aluminum. Just waiting now to see what he says about 7075 Al, or possibly 2.0mm Ti

    That's their minimum qty, so hopefully he'll agree to cut two different size rings instead of two of the same size. Of course its all moot if the spline doesn't fit

    Oh yah, it'll be a 34t (plus maybe 32t) spiderless ring for a shimano crank.
    Last edited by cdn-dave; 11-30-2012 at 09:22 AM.

  11. #11
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    you should call/email these guys, they do a lot of custom motorcycle/atv sprockets for us at school

    Rebel Gears

  12. #12
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    5054

    Quote Originally Posted by Metty View Post
    you should call/email these guys, they do a lot of custom motorcycle/atv sprockets for us at school

    Rebel Gears
    Thanks for the tip! I'll see if I can source something locally (Germany) first though...

    Speaking of local, any metallurgists out there?

    The first supplier I contacted can make the rings out of AlMg3, which I think is the equivalent of 5054 Aluminum. Would this be strong enough, especially with a 2.5 or 3mm thickness?

  13. #13
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    fyi - burmapeak is pursuing this and making some great progress!

    http://forums.mtbr.com/singlespeed/x...l#post10486194

  14. #14
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    You doing this and offering rings for sale, or just designing a ring for yourself and offering the design to us to source our own metal workers or DIY?

  15. #15
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    Just offering up the design, with forum reader input!

  16. #16
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    We the people ... shimano spiderless chainring for the M950 crankset

    Hey Guys, we decided to go ahead and start accepting pre-orders for our shimano spiderless chainrings for the M950 crankset. We have already had this chainring done and being tested for a long time we just haven't been able to get to production with all the other orders we have coming in for our custom chainrings. Early next week I'll have a few hours open on the laser to cut these out and mill the teeth. They will be available in Stainless Steel, Titanium and the Aluminum ones can be anodized black, red, blue, brown, gold, purple, green, orange, grey or pink. They can be pre-ordered online in which payment is only authorized online and you will only be charged when the product ships. If you have any questions just let me know, Thanks - Colin

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    Warhawk Industries - Specializing in Stainless Steel, Titanium and Aluminum Chainrings

  17. #17
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    spiderless chainring - open source

    Took me a while but I managed to make a couple 32t chainrings:
    In the middle is my worn out Warhawk ring, the other two were laser cut from 4mm Anticorodal AW6082. It was harder than I thought to reduce the thickness of the teeth to 2.3mm; due to either my (lack of) skills on the lathe or the fact I could only hold it by the middle (lots of vibration all the way out to the teeth).

    The teeth are a good 2mm longer than those of the Warhawks, hopefully that solves my chain dropping problems:


    The chain sits well and the splines fit great!






    Pmail me for the dxf

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