Brainstorm: Open Source Fixture <$1000?

[Daniel_Y]

Introduction:

I have been mulling over the purchase of a frame fixture for a while now. However, I just don’t have the space and need to justify a $4k pro fixture. Reading Pi Bike’s and Ted’s build logs, as well as Walt’s Framebuilding guide made me realize that a traditional frame fixture is overkill for the hobbyist and amateur frame builder. Walt’s guide made me realize that frame alignment comes from tight joints, intermediate alignment steps, and welding sequences, NOT the fixture!

Problem:

• Existing frame fixtures are really expensive ($4k+)
• Frame fixtures eat up a lot of shop space
• Frame fixtures only serve one purpose
• Toolmakers (sadly) come and go, leaving unsupported tooling

Solution:

• laser cut and 3D printed frame fixture for <$1000
• Welding table architecture saves space and is multipurpose
• Open sourced design allows for community support and modifications

Rought Draft:

The idea is to use laser-cut fixtures (red) and welding clamps to hold everything to a welding table. The frame is fixtured on a 100mm centerline offset from the table surface. The laser-cut fixtures can easily be modified and remixed by the community to suit new bike standards. For reference, the bike in the JIG is an XXL mountain bike:

Table:

The table is based on a 36x48in CertiFlat welding table:

• $490
• 16mm holes at 2in spacing
• claimed .015in flatness [.4mm]
• With a pivoting “seat tube fixture” you can probably get away with the $350 24x48in
  • Saves money, space, and weight!
    

Laying Out:

The idea is to lay out a 1:1 print of your bike on the table, and align your fixtures to the drawing. I think this is the key to a low-cost fixture. This method offloads the accuracy and precision of your fixture to your printout, allowing you to have a simpler and cheaper fixture.

• 36x48 prints are roughly $10 based on my research
• Can be done in bikeCAD and Fusion360
  • Print Full Size Bike | www.bikecad.ca
• This method could reduce error. It’s not uncommon to have a jig setup mistake!

Fixtures:

Simple right-angle fixtures are cheap, easy to make, and easy to modify:

A simple indexing system can allow for frame removal:

• green plate is fixed to the table (somehow)
• red upright allows the fixture to slide back to release the frame

Assistant blocks (yellow) can easily be 3D printed or laser cut to fit your needs:

Precision Parts Required:

The following parts could be 3D printed, but making them from aluminum would make life easier and more precise:

• HT pucks
• ST cone
• BB puck riser
• Dummy axle:
  • to me it makes sense to use the current dummy axle standard
  • threaded rods could be the ultra-budget option

Rough BOM:

Item	Price	Qty	Sub
Welding table	$490	1	$490
Welding Clamps	$20	5	$100
Laser Cut Fixtures	$50	3	$150
Aluminum Pucks	$40	4	$160
Dummy Axle	$75	1	$75
		Total:	$975

Limitations:

• Printing out the drawing 1:1 seems like a pain… However, I don’t see a better way around it. Adding precision fixtures to the table like PVD’s Fixture drives up the cost and complexity.
• The pucks could be 3D printed, but it would be much better if they could be made from aluminum. Perhaps we can find a supplier (like Paragon) to support the open-source architecture
• The most complicated piece is the dummy axle retention device. It can be 3D printed until someone finds a better way of doing it.
• I am not sure how accurate this system will be…

Conclusions:

Well, there you have it. My favorite part is that 98% of the time, the fixture is just a table, and I can stack my crap on top of it.

The beauty of a truly community-driven open-source project is that it is a living thing. It can be remixed, improved, made cheaper, made better, and customized to suit your needs.

Let me know what you think. Will it work?

• Great idea, I would adpot it!
• Good idea, but I already have a fixture
• Skeptical, but curious
• It won’t work.

References:

• The Creator Frame Fixture | Cobra Framebuilding
• Bicycle Frame Fixture aka Your New #BFF — FARR Frameworks
• http://www.peterverdone.com/the-pvd-cyberdyne-system/
• http://www.peterverdone.com/pvd-wopr-frame-fixture/
• http://www.kongabicycles.com/
  • Bicycle Frame Buddy
• https://www.instructables.com/Bicycle-Frame-Building-Jig/

[earle.b]

The simplified Cyberdyne is WOPR.

PVD WOPR Frame Fixture | Peter Verdone Designs

I’ll have to dig into old mtbr threads to find it, but a guy used a similar table style fixture and incorporated his tube notcher into it and mitered his tubes in fixture to get his angles.

[Pi_bikes]

Looks excellent. I would make 2 minor additions, if they aren’t already in the design.

1- In New Zealand those styles of welding table are not locally made and since we live so far away they cost a lot. I just looked up the local suppliers price on the 1200x750 rhinocart and its just shy of $4300nzd. But a piece of 18mm or thicker MDF is cheap, and flat enough to make a decent bike frame. Some holes cut on the centerline of the mounts would make it easy to screw it down to a sheet of mdf if they aren’t there already.

2- A V notch or arrow built into the front and rear of the mounts. for my mdf jig I drew straight lines onto the mdf on the angles that the tubes were running on and had arrows on the mounts to get things lined up nicely.

Good to see something like this in the works, I would have had this laser cut if it was available when I was doing my first bike.

[anon68659156]

I use an Alex Meade Surface plate fixture on a cast iron T slot table from a scrapped CNC mill. With all the little bits involved I probably spent closer to $2000, (and the table weights 900lbs), but it allows me to fixture anything, not just bike frames.
Incorporating a 5" sine plate and some sliding parallels has allowed me to avoid using a full size frame drawing while also being very accurate. I will take some pics when I have time.

[Mikesbikester]

I have some thoughts about this design, I’ll list them below here.

The certiflat tables are pretty expensive and heavy. It would also make it difficult to tack one side of the frame. (Also, I’d be surprised if they’re as flat as you think they’re gonna be after welding)

I’d think that using aluminum extrusion would be preferable to a big steel table. There are many fixtures that use different extrusion sizes and have different methods of setting angles.

To me, there isn’t a benefit to being able to lay out 1:1 to a drawing if youre not using an MDF base. It’s also worth considering that printing 1:1 isn’t necessarily an efficient, affordable or accessible option to the builder who’s looking for an open source fixture.

There are a lot of ways to make a fixture, not saying one way is better than another but the PVD fixture looks like a it would be frustrating to set up and use since there isn’t a good datum to measure off of. To me a table that is a fixture would not work. It would be covered in tools, I’d lose the tool I just had under a tube, I’d have tools on it in that would get in the way of fitting up tubes, etc.

I think it’s preferable for the fixture to hold the frame in a vertical position, as it provides better visibility, makes it easier to adjust tube fit up, and a vertical position naturally holds the down tube in the right spot.

When using an adjustable fixture, it’s easy to set it with an angle finder and tape measure. On mine I set the ST and HT angles, set the BB height, and dropout height. Set the vertical distance to the bottom of the HT. Cut the top tube to the right length, that constrains the front triangle. Cut the chainstays to the right length and that constrains the rear triangle. Cut the seat stays and down tube to fit.

Have you seen this design that’s already been shared? A friend built one and I’ve used it with him some. The extrusion sizing seems like it’s maybe a bit overkill, but it works great. A couple of tandems and some other large frames have been made on it with no issues.

Bicycle Frame Building Jig

This is intended to be constructive feedback and I hope it helps. It’s just one personal opinion and different things work for different people. At the end of the day you’re going to figure out what works and what doesn’t work by actually using the fixture. If you have the opportunity, use some other builders fixtures and see what you like and what you don’t, it’ll likely save a bunch of time and money.

Keep it simple!

[Daniel_Y]

@earle.b

The simplified Cyberdyne is WOPR.

Good callout, I’ll add it to the references. I am curious about what the BOM cost is. In my experience, the 8020 and Misumi hardware adds up quick!

@anon68659156

I use an Alex Meade Surface plate fixture on a cast iron T slot table from a scrapped CNC mill. With all the little bits involved I probably spent closer to $2000, (and the table weights 900lbs), but it allows me to fixture anything, not just bike frames.

For reference: https://alexmeadetools.com/product/flat-plate-fixtures/

The cast iron t slot table sounds ideal, but 900lbs! What a chonky boy. According to fusion360 the 36x48in welding table weighs ~100lbs. Hopefully, that is it is light enough for me to move around with me.

@Pi_bikes

Looks excellent. I would make 2 minor additions, if they aren’t already in the design.

1- In New Zealand those styles of welding table are not locally made and since we live so far away they cost a lot. I just looked up the local suppliers price on the 1200x750 rhinocart and its just shy of $4300nzd. But a piece of 18mm or thicker MDF is cheap, and flat enough to make a decent bike frame. Some holes cut on the centerline of the mounts would make it easy to screw it down to a sheet of mdf if they aren’t there already.

2- A V notch or arrow built into the front and rear of the mounts. for my mdf jig I drew straight lines onto the mdf on the angles that the tubes were running on and had arrows on the mounts to get things lined up nicely.

Great suggestions. The MDF board is much lighter and cheaper. It would cut the cost of the project in half. It actually sounds ideal prototyping material before I commit to the welding table.

Centerline references built into the 90deg squares are a great idea. I’ll incorporate them in the first pass of the design.

@Mikesbikester

This is intended to be constructive feedback and I hope it helps. It’s just one personal opinion and different things work for different people. At the end of the day you’re going to figure out what works and what doesn’t work by actually using the fixture. If you have the opportunity, use some other builders fixtures and see what you like and what you don’t, it’ll likely save a bunch of time and money.

Good suggestion on the instructable, ill add it to the references. Also, all feedback is welcome.

The primary driver for this project is actually space, as most apartment/renter dwellers can relate to. I am exploring table-style jigs because they can serve double duty as a table or slid under a shelf.

From my research, the 8020 fixtures end up costing >$1000, take a lot of time to build, and require access to a mill. For my personal cost-to-time ratio calculation, I would prefer to buy a new or used fixture. That being said those fixtures don’t address the space issue I have…

I think like people’s comments on the welding table are valid. MDF might be the optimal price-weight-precision setpoint for this project.

With a sacrificial piece of MDF, you could easily mount the jig vertically and punch holes to give access to the other side (example from Starling Cycles):

[PJF]

Hello.
Only built one frame.
Homemade jig. I maybe have a pic.
This is Marino bikes jig. Looks a lot cheaper than a welding table

[Daniel_Y]

[PJF]

I live in Sweden. English is not my first language.
I cant find a pic of my jig. Its this type. Maybe $50.

Finishing my Budget Framebuilding Jig - Fiets of Strength Ep.5

[HomageFrameworks]

For your reference list, I loved the idea of the LCFF (low cost frame fixture) from the bicycle academy. Hard to get an exact price in USD because of currency conversion, but it would have been in the $1500-2000 range. They supplied everything but the hollow section beams, and it shipped in something the size of a large shoe box. It included a laser that attached to the bb post to align and correct for the hollow beam’s twists and curves. It is supposed to be coming back under a new name in January.

[Mikesbikester]

@Daniel_Y

The primary driver for this project is actually space, as most apartment/renter dwellers can relate to. I am exploring table-style jigs because they can serve double duty as a table or slid under a shelf.

I suppose we may have differing opinions on work flow in limited space. In my space it’s super important for everything to be compact and have a place where it can be put away, which unfortunately includes weld tables and working surfaces. I can pretty easily lean my fixture against the wall or take the vertical pieces off and store the whole thing on a shelf, it’s definitely less than 100 lbs. I should weigh it when I get back from holiday travels.

@Daniel_Y

From my research, the 8020 fixtures end up costing >$1000, take a lot of time to build, and require access to a mill. For my personal cost-to-time ratio calculation, I would prefer to buy a new or used fixture. That being said those fixtures don’t address the space issue I have…

I just learned that 8020 garage sale ebay store is no longer a thing, there must be something similar though? For kicks in priced out the pieces that I’m using on 8020’s site, its be less than $200 in extrusion to make my fixture again. The only machined parts on mine are related to the dropout holder, which I think could be done differently without machining.

(2) 40" pcs of 1.5x1.5 $60
(1) 60" pc of 1.5x4.5 $110

Just a thought. It’s easy to put in a foldable bike stand, with a foldable welding table the tools have good storage factor. Happy to share cad data or a list of materials if needed, just let me know.

[rainyday]

This is a great discussion! Haven’t made one yet but was planning on using 8020 jig similar to @Mikesbikester and using the fittings from http://ideas2cycles.com/the-jig/.

[sikocycles]

I love the idea of the welding table being the jig as long as it is easily removable for storage and able to use the welding table for other things. Like frame alignment and making that ever so trendy river table.
Here is my thread of my 8020 jig. I used the plans from Kris at 44 bikes. Hope he joins. He has been awesome.

The garage frame building journey

[anon91558591]

8020 fixtures are very cheap and don’t mostly require any fancy machining. There are lots of variations but basically the cheap fixture thing has already been solved.

-Walt

[anon91558591]

There’s also the chopsource jig. I only know one person who has used it but it apparently worked ok.

I think it’s like $400 plus $100 worth of tubing with very simple assembly.

-Walt

[Daniel_Y]

@Mikesbikester

I just learned that 8020 garage sale ebay store is no longer a thing, there must be something similar though? For kicks in priced out the pieces that I’m using on 8020’s site, its be less than $200 in extrusion to make my fixture again. The only machined parts on mine are related to the dropout holder, which I think could be done differently without machining.

Thanks for posting a picture of your fixture. I see what you are saying now, your design is quite simple. I was visualizing the 8020 styles as the “complete package” with linear scales, angle pivots, locking knobs, etc… That design requires a lot of machined components and is not really disassemblable.

Without the scales and the pivots, it’s much simpler, I like it.

I bet there is a happy middle ground between 8020 extrusion and laser-cut steel fixtures.

For example, this offset ST post

I played around with my CAD workflow to create these angle fixtures:

I’ll investigate the 8020 route next.

[Neuhaus_Metalworks]

Another solution could be laser cut and bent aluminum parts. Send cut send should be able to bend the attachments as needed. I can’t confirm but there is a possibility that a cut and bent aluminum part may be more dimensionally accurate than a welded laser cut steel part.

[Mikesbikester]

Happy to share! I think it just depends on what the use is. I imagine that the user for a free frame jig plan is a hobby builder. If it takes 20% longer to set up than a production level jig, but costs 10% of a production* frame jig, the hobby builder is happy because they get to make themself some frames with a tool that didn’t empty their wallet. The goal for a hobby frame builder is to make a bike. With some aluminum extrusion, some cad skills and a 3d printer it can really come together quickly and affordably.

Maybe I’m way off, but to me it seems like frame building is inherently an iterative process for a hobby builder, they want to improve on certain areas with each build, whether it’s modeling/drawing, welding, cutting, fit up, geometry, suspension design, etc. Having to modify the fixture or work around a fixture that doesn’t hold the parts correctly takes away from actually building the frame.

I think there are some important things features to carry over from production* fixture design, that can make the process easier but ultimately it can be a very simple and affordable tool as long as its capable of holding the pieces in the right spot.

*I suppose by production fixture I mean a purchased frame jig designed for custom frame builders. Anvil, cobra, etc. Not a production fixture used in manufacturing models or batches

[Daniel_Y]

@Neuhaus_Metalworks

Another solution could be laser cut and bent aluminum parts. Send cut send should be able to bend the attachments as needed. I can’t confirm but there is a possibility that a cut and bent aluminum part may be more dimensionally accurate than a welded laser cut steel part.

SCS has some surprisingly good documentation and clear pricing on their bent parts ($2/bend). That being said, I am not familiar with the dark arts of sheetmetal design.

• 3/16 bending parameters: A36/1008 Mild Steel Laser Cutting | SendCutSend
• Sheet Metal Fabrication Bending and Forming Guidelines

The CAD is easy for me, but I don’t have the intuition for tolerancing sheet metals. Maybe someone can chime in with some expertise.

[Neuhaus_Metalworks]

Just design the part around 8020’s linear rail pads, tap the holes on one side, and use set screws to take up the gap, at that point you have a lot more tolerance forgiveness.