A hollow bolt solution would probably be the cheapest and easiest. I think this is what the benchmark fixture is using:
However, I currently have the cone tapped, whereas that design is a through hole…
Ill play around with it a bit for the next revision.
This is exciting to see. There are so many nice options available now that weren’t around 10-15 years ago.
In my designs I’ve used press fit pins for this purpose. You can have sendcutsend rough the holes for you then finish them with a reamer. Or at least that is how I did it with my small CNC mill.
80x120 extrusion is overkill for stiffness, but gives you a nice flat plane to reference off of and check everything for accuracy. I use 4.5” by 3” 8020 on my jig for the same reason.
Your angle indexing is nice, but what happens if you miter your top tube just a mm too short and need to tweak the angles to make it all work?
Alex
Thanks!
Agreed on the extrusion size. I need to do some cost-benefit analysis there.
The index is only acting as a stop. There is a handle that locks the rotating action. You can just pull out the pin and fudge the angle.
I’m not too happy with the angle-finding method. Realistically, it’s probably easier to use a digital angle finder. But I wanted a solution so people could visualize the jig setup. I’ll make little magnetic plates to stick the finder onto the fixture so you can pick the angle finding method of your choice.
Ah, I missed that detail and it makes sense. My jig just has scribe lines that are engraved with angles. It’s pretty easy to do if machined, but would be hard with laser cut.
Does anyone build full suspension frames with the off the shelf frame jig options? Would provisions for pivots and different seat tube placements add value? Probably not if price point is a main driver for this project, right?
I built my squishy bikes in the same jig I built for the road bikes. It was at it’s limit of range. The pivots were cut and placed away from this jig with a smaller plate jig made specifically for this. Going forward I am planning on making a plate jig specifically for making from front ends which will have the pivot standoffs as part of it.
I don’t know if this adds to the discussion, but Aaron Hoover did a great CAD model of an Henry James style jig and it’s free on OnShape. Onshape
Aaron passed away a couple years ago, but he used this jig in his practical engineering classes where students built bike frames. I have been slowly getting everything together for this jig, but the design that is coming together here has be reconsidering. I want to build long-tail cargo bikes, so I’d love to make a stretch model.
Ah that’s a great fixture and a really sad story. I never met Aaron, but sounds like he was living my dream: Teaching engineering and bikes at Olin. Ill try to pull som inspiration from that design and morph it into the open fixture
Looks good, I’m starting to design my jig and plan on using as many 3d printed parts as I can. I will use glass filled nylon for the material.
For 0.5 angle setting you could make another set of pins that are machined to a half circle .25" from the head to allow a positive stop at the 0.5 angle position.
Hey Everyone, I wanted to share a bit of what I’m working on. Maybe it will get its own thread soon, but I think it builds on a lot of what’s been discussed here.
I’m building a Fusion 360 parametric bike design system, where just about any parameter that you could use when designing a bike can be given a value, and the bike then generates in 3D. The 3D model is mated to a fixture design, which will be updated in real time. Please note that the fixture shown is just a stand-in. I intend to maintain the vertical HT/BB along the top rail style, but the details and mechanical design are still being worked out. Of course, the brackets for the dummy axle mount and the seat tube mount are not shown.
My thinking is that a builder could put in the specs for components like stem, bars, spacers, fork etc. Using whatever fitment method you chose, you can alter all the parameters to dial in the grip location relative to the seat and BB. Fusion will translate that to the fixture automatically, and the numbers it spits out will let the builder move the fixture blocks to those locations- likely with some adhesive ruler mounted to the 8020.
The fixture will most likely be built with OpenBuilds extrusion- their pricing is hard to beat and their quality is pretty great. I have access to a mill through school, but I’m trying to design parts that can also be sourced from SCS or 3d printed.
I’d appreciate everyone’s thoughts and feedback, and I’m happy to answer any questions. I plan on open-sourcing all of this soon but it’s obviously not there yet.
Thanks!
Cool idea! I think that style of extrusion fixture is the easiest and cheapest to build. The only downside is that it is un-intuitive to index/set up, but if the CAD help with that, it would help solve that problem.
A few thoughts from my experiences so far:
Also, personal preference, but I always hide the joints, they are so ugly and they never really tell me anything!
I look forward to seeing how the open extrusion goes. Initially, I specced 40x40mm t-slot from 8020, but I think it’s overkill.
Thanks for your thoughts!
I looked at a lot of other extrusion base fixtures. The affordability is there, but the setup sucks.
To your other points:
Good call on hiding the joints haha.
I’ve worked with OpenBuilds stuff in the past for 3D printer frames, and it’s awesome stuff.
40mmx40mm might be overkill, but with their pricing, it seems like a no-brainer for a little more rigidity: 1500mm of 5050 for $45 vs 1500mm of 4040 for $145
I’m hoping to start milling/printing/ordering stuff next week so I can start some real-world torture testing
Just playing devil’s advocate, but aren’t most fixtures kind of unintuitive to index and set up? I’ve admittedly only taken a cursory look at the other designs shared in this thread, but it seems like more or less all of them require some intermediate calculator to go from bike geometry to fixture dimensions. There are obviously advantages to fixtures that hold all the tubes in a way that looks like a frame simultaneously, but that goal can add complexity and expense to the build that may not buy that much in terms of actual usability for the typical hobbyist. As long as you have a good way to measure linear and angular dimensions, and can keep things straight, there are lots of creative (and cheap!) ways you can fixture tubes to build a frame if you’re willing to look past the “it has to look like a bike before I start tacking” paradigm.
Disclaimer: currently designing fixture, haven’t built bike yet. So take this with a grain of salt. There’s probably something I’m not thinking about.
A few of the popular ones like Anvil and Cobra are integrated into BikeCAD. It would be cool if someone who has used that feature can speak up on the workflow/ease of use.
I don’t know what people with custom fixtures are doing. It does seem like a PITA
This specific “hockey stick” style of fixture typically does not have an ST cone, so it relies on the TT miter to hold the ST tube in place.
I think there are two camps of builders:
Nothing wrong with either style. My comment about the intuitive setup is really towards the 2nd group of builders. Realistically, CAD is going to make fixturing and mitering way more precise, regardless of the fixture. Most people who are able to follow and comment on this thread probably have no issues either way.
I think that is one of the advantages of the initial design of the thread: the 1:1 layout style. It is very hands-on and beginner friendly to visualize the geometry of the frame:
IMO, the more good designs out there, the better. People can pick the method that works for the way their brain works.
I use Anvil and Sputnik jigs, it takes about 30 seconds to set-up using a BikeCad drawing.
The Sputnik is very fast. I have a dimension preset in BikeCAD that highlights the jig numbers and miter numbers I need:
Thanks @manzanitacycles and @Mark. Seems like a very solid workflow- I don’t think what I’m working on here will have any benefits to builders like you guys. If I’m wrong please let me know haha
I’m definitely trying to appeal to someone with more of a hobbiest budget at the moment.
A few questions if you don’t mind:
*Do you use 3D CAD in your workflow? Why or why not?
*Are there things you’d like to change or have changed with your fixtures?
Only recently have I started using Fusion, mainly for chainstay design and little laser cutting projects. BikeCAD does everything else quickly, especially front triangles, that it seems unnecessary to reproduce a whole frame in Fusion. Although with @Daniel_Y‘s tutorial it was fun mocking up a frame just for the cool factor.
I can see it being really useful for full suspension designs and modeling frames with lots of 3d printed joints.
The Sputnik jig is a rock solid beast. It’s the stiffest jig I’ve used, which means it can act as a go no-go gage for top tube and chainstay lengths. I realize the price of it is likely too much for the hobbyist. But it’s worth studying how it’s constructed. All the cantilevered parts use very thick material to reduce flex. When in doubt over build!
Somewhere along the line in one of the more recent updates, Fusion made this a lot better.
Anyway.
July Cycles does an interesting version of this fixture where the generate all the parts from CAD and print them uniquely for each frame. This specific execution wouldn’t really work well for metal bikes, but the concept is interesting to me. They’re also doing some very interesting work on the composites side of things, I’d recommend digging through their instagram. But that’s a different topic.
