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"Brainless" shock blank for Specialized Epic

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Creation's quality: 5.0/5 (1 vote)
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3D model description

Disclaimers

  • Yes, this is probably - okay, certainly a bad idea.
  • Just like everything on Thingiverse, choosing to print and then use this is at your own risk. Not comfortable with it? Don't print it. :)
  • No way in hell Specialized would be cool with this. If they had any idea about it, they'd probably use it to void your warranty.
  • If it's installed and it breaks under your weight, the seat stay stiffening bridge will be driven into the back of the seat tube with quite a bit of force. Odds are good that will break your frame. I addressed this by stuffing a rolled up towel between the bridge and the seat tube. Yes, that's as ugly as it sounds, but it worked when I broke the first prototype.
  • There's a reason I named this "Brainless". Get the hint.
  • I'd really only suggest this to get you back on the road or really light trails while your suspension is being serviced. Having a spare bike is an even better solution.

Explanation

I've got a Specialized Epic, and I ride it often. Love the Brain suspension technology, and ride the bike a bunch. Unfortunately, the technology is proprietary, and routine maintenance requires sending the shocks back to Specialized. They turn the stuff around quick, but with shipping there and shipping back, it can be a couple weeks before your bike is back together.

If only there was a way we could use 3D printing to address the problem!

Before I sent in my rear shock, I took a bunch of measurements, and have created "Brainless" - a shock blank to replace the Specialized Brain rear shock on my Epic while the suspension is being serviced. It'll basically turn the bike into a hardtail and has about 20% sag designed in. The lower mount uses an M6x1.0 threaded bolt, and I've modeled this hole at 5mm so I can use a tap to cut in threads. (I like the results better than printed-in threads)

There are a bunch of reasons why this is a bad idea... (see the earlier photos with the red piece for just a small sampling if you can't think of several on your own) but I still found it to be an interesting idea and since I could try it with so little problem, (thanks to the wonders of 3D printing technology) - I decided to pursue it. Also, this isn't an integral structural part of the frame - the frame is intact and functional without this part, so the only real risk with breakage is the frame sags - and the cross brace of the seat stays could hit the seat tube, which on my bike is carbon. But - the wheels will still be attached and pointing the same direction, and the fork won't fall off.

In testing, the original PLA prototype survived a 10 mile ride with no problems including curb hopping and light off-roading as well as riding through a drainage ditch with babyhead rocks. Surprisingly, no issues. So, I got greedy and wheelie dropped off a tall curb, and broke it. Thankfully, I had wadded up a towel behind the seat stay, so I didn't smash the seat tube. PLA seems to be too brittle, and I also didn't print it at 100% infill, partially to see how much it could actually survive. I was surprised how much it did survive, and wasn't surprised that I did manage to catastrophically break it.

I've reprinted in ABS as 100% infill, but haven't put much distance on that one. Looking at the failure in the original prototype, I thought the best idea was to print it at the full width of the front bushing, then print it on the side (not the bottom) so the layers run perpendicular to the axis of the bushing. Since the failure I saw in the original prototype was mostly along a layer line split, rotating the layers 90 degrees would make a huge improvement to the strength.

The font is "Bullet" regular, which was chosen as it looks kinda slightly vaguely similar to the font used in the Specialized logo. I've got two versions of the v2.0No ("oh no", get it?) one with and one without the "Brainless" logo. I only include the original version for reference.

3D printer file information

  • 3D design format: SKP and STL Folder details Close
    • brainless-shock-blank-v2.OhNo-unbranded.stl
    • brainless-shock-blank-v2.OhNo.stl
    • brainless-shock-blank.skp
    • shock-blank-brainless.stl

    Learn more about the formats

  • Publication date: 2020/01/30 at 00:41

License

CC BY NC SA

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Creator

Note: I wanted to try Cults3D as a possible alternative to Thingiverse, but after giving it a bit of a look, I'm not super impressed. Feel free to visit my Thingiverse page if they can manage to keep that site running:

https://www.thingiverse.com/cmh

I went to school as a mechanical engineer, and got interested in 3D modeling, specifically the SDRC I-DEAS CAD/CAM software system. This interest got me my first job working for a CAD/CAM reseller doing pre and post-sales support. I was lucky to be involved in 3D printing in the early 90s - for a demo of rapid prototyping, I modeled the mouse from my HP-UX CAD workstation and it was rendered via stereolithography. I still have that model, but across the years I stopped using CAD and moved to systems administration. Now that 3D printing is affordable and mostly reliable, I've gotten into it and am having a blast. I printed all the usual cute little trinkets and tchotchkes, but quickly got bored of that. What I find most interesting is needing something, then spending a little bit of time in a CAD program and soon after that having a real, functional version of the part in my hand.

I'm a cyclist and bike mechanic as a hobby and a side job, and have found endless applications of 3D printing to both bikes and bike maintenance. Coworkers have also come to me with many varied requests, each of which has been an interesting challenge and an opportunity to learn.

I am constantly learning, constantly trying to challenge myself to learn new things and technologies, so hopefully as I progress my designs will continue to improve.

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