Frame jig build.

[adarn]

Hey everyone.

Questions about home made frame jigs get asked here quite a bit, so I suppose this won't hurt to add.

Anyhow, I'm building a new frame jig and I thought it might interest some people and be cool to get some feedback/input from the community.

So my design is pretty much a blatant copy of the jig made by Kris from 44bikes. (Sorry Kris, hope you don't mind!)

There are a few reasons I went with this design. This first is cost. Buying 8020 extrusion is much cheaper than buying and machining a big sheet of aluminum. This type of jig, I feel, will also allow for lots of access to tubes for tacking and I'll be able to move it around.

Here is a picture of my last jig:

After building 7 frames on it, I've realized that it sucks a lot, but hey, it was pretty much free to build.

So from the experience with that ji and my perception of other jigs, I came up with this list of requirements:
-Straight - dead straight (the last one was not)
-rigid
-Able to handle 68, 73, and 100 mm BB shells
-Rigid and swapable dummy axle
-handle 44mm HT's
-Be able to set the jig up with minimal tools
-Be as cheap as possible (obviously)

So with that in mind I got to looking at all the options and settled on the beam style. I think Kris has his pretty dialed in and I like a lot of the things he's done.

Anyway, I have almost everything drawn up in solidworks and things are looking pretty good.



A friend has offered to let me use his CNC shop to make most of the parts, which is awesome, and I'll also have access to a mill and lathe for building the jig, All of which I don't have for building bikes.

Anyway, I'd love to hear other people's opinons on handy things for a jig to have. I'm thinking of something to center the ST on the BB and for the chainstays.

I'll be ordering material in the next week or so and hopefully cutting it up soon after.
More then,
Adam

[ToddFarr]

Any jig, tool, fixture, machine, ect. I build I always make sure to put adjustable handles at every point that is adjusted by the user. It does have some added cost, but the hassle of trying to find hex keys around the shop is just not my cup of tea. Handles or wing nuts or something you can slide stuff around and lock it down quickly with one hand. This to me is invaluable. Good luck with the build!

FYI, all those parts are easily machined on a manual mill and manual lathe. And if you are stacking material like you are don't forget it check it's dimension, 0.500" stock is rarely 0.500". So make sure to account for it in the mating parts if you aren't going to mill it down to spec.

[adarn]

Thanks Todd,

Everything is going to have adjustable handles on it. Jig 1.0 was all allan keys and I totally agree, huge PITA.

And I will certainly be double checking everything. The guy who is helping me owned a precision machine shop for years, so he has some good methods and ideas on how to keep stuff straight.

[fortyfour]

No worries Adam. Build on! Personally, I have 2 T-Handle wrenches that live with the jig and they are only for the jig so they never go missing. Have you considered the stand? Definitely consider this and attachment points before hand. It's nice to be able to have height adjustment and the ability to spin it 360* to get at tough spots to tack/weld. At the end of this video, you can see how the jig rotates and then is height adjustable via an air piston. My stand / trolley is actually an earlier version for this machine.

[edelbikes]

Just 2 quick comments on your design:
- Make sure the rotation point for the HT assembly is aligned with the bottom of the head-tube. The setup of the jig will be much easier (not clear on your drawing).
- The vertical piece of 8020 which is used for the rear axle should be extra strong. If it's too light it will have a tendancy to distort if your two chainstays are not exactly the same length... (don't ask me how I know that... )

[adarn]

Cool to see you chime in, Kris, thanks for your support. I hadn't thought much about the stand actually. I figured I'd just do something with adjustable height, but I'll look into rotation too. I'm not sure that cart is in the budget, but I'll certainly look at other options.

Edel,
The HT assemble is the last piece I have to dial in. I have the pivot point at the bottom of the plate. This is really the first big thing I've built in solidworks, so it's taking a little figuring out.
And if you see the "dummy axle" on my first jig, you might guess that I've had that same experience. Zero rigidity on that thing. The extrusion I'm using is pretty darn rigid, so I'm hoping it should do the trick. It's also pretty short because the BB is down 60mm or so (can't remember exactly right now) from the botom of the main beam, so the axle will rarely create that big of a moment on that piece of extrusion.

[fortyfour]

If I had to choose between rotation and height adjustable, I'd choose rotation personally if I was limited to what I could do with my budget and just build the stand so that it was a compromise in height for sitting and standing. I always sat to weld, but having worked in a shop where the only option was to stand to weld, I've become accustomed to both and now sometimes prefer to stand.

[adarn]

Ah, I see. I had an idea recently to just mount a pice of tubing or rod on the back of the main beam. Then i was thinking of building a trolley sort of thing and mounting a park stand on there somehow. Does that make sense?

[dsaul]

If you can ignore my sloppy wire feed welding, this worked very well for me to get my stand to articulate. It's just some 2" conduit pipe and fittings that I picked up at Home Depot. I know I shouldn't be welding galvanized stuff, but its super cheap and I don't do it very often.

Articulating mount | Flickr - Photo Sharing!

[Alistair]

Ah, I see. I had an idea recently to just mount a pice of tubing or rod on the back of the main beam. Then i was thinking of building a trolley sort of thing and mounting a park stand on there somehow. Does that make sense?

In case it helps, here's a few pics of what I built for my home brewed jig,


Jig stand. by Duncan Cycles, on Flickr



Jig stand. by Duncan Cycles, on Flickr


Jig stand. by Duncan Cycles, on Flickr


I would like to have had height adjustability as well as rotational, but in the end I went with a fixed height jig stand and figured I'd sit and stand as required for brazing/welding.

Alistair.

[Eric Estlund]

Before you drop to a knee to get lower, make sure an errant piece of 14mm seat stay hasn't rolled to your patella landing point.

I bolted my stand to the floor- cleans up the base area for my feet, and takes all the edges away in case I drop a tube.

[adarn]

Sweet! Thanks for the ideas, guys!

I like the home made stands, definitely giving me some ideas. I've got the design pretty much drawn up. Just got to double check all of those tolerances and fits and maybe change a couple of things. but it's looking good

[adarn]

So I had an idea...

I'm curious what you might think about this. It wouldn't be hard to do, Actually, I could pretty easily switch from this design to my original plan. I feel like the main advantage here would be setup time. I would have the seat tube assembly bolted in place, and could then put measurements on the jig itself for head-tube height, reach and chain stay length. So in theory I could set up the jig without any tools, which I think would be awesome, especially coming from my PITA jig.

The disadvantage that I see is more place to be out of alignment. But other than that I think this could be a good route. what are your thoughts?


Capture.JPG

Thanks,
Adam

[adarn]

Oh also, Kris, do you think your axle assembly is stiff enough? I'm thinking about beefing it up back there.

[Alistair]

So I had an idea...

I'm curious what you might think about this. It wouldn't be hard to do, Actually, I could pretty easily switch from this design to my original plan. I feel like the main advantage here would be setup time. I would have the seat tube assembly bolted in place, and could then put measurements on the jig itself for head-tube height, reach and chain stay length. So in theory I could set up the jig without any tools, which I think would be awesome, especially coming from my PITA jig.

The disadvantage that I see is more place to be out of alignment. But other than that I think this could be a good route. what are your thoughts?




Thanks,
Adam

Looks like you've increased the complexity of the design (thereby introducing likely inaccuracy) without gaining anything.

If you attach the HT holding cone assembly directly to the vertical extrusion things are simpler, and you don't lose any jig function, that I can see.

Alistair.

[Andrew Drummond]

Adam, you might consider looking into item (german brand, lowercase i) extrusions rather than 80/20. Straightness specs are tighter, and they have an incredible variety of profiles and fasteners available. It's what the Arctos jig is made from, and what I'm planning to use for my own (partially finished model below). You can buy it on ebay.

Andrew

frame jig screenshot.jpg

[prolix21]

someone should do a kit version of one of these DIY extrusion jigs. all the bolts, custom pieces - bring your own extrusion

[David Tollefson]

someone should do a kit version of one of these DIY extrusion jigs. all the bolts, custom pieces - bring your own extrusion

I'd be interested in this... Any one?

[adarn]

Alistair, I've thought about it more, and I think you're right. I think I'll just go with plan A. I could always try that other way too if I find setup too hard

Andrew, I was under the impression that 8020 was pretty flat. Do you know the tolerances? I should probably call and ask I suppose.
I'm guessing I'll have to shim some stuff anyway, even if the extrusion is perfectly flat. I've also thought about planing it on a mill. It will difinitely be checked for flatness on a surface plate once it gets here.

someone should do a kit version of one of these DIY extrusion jigs. all the bolts, custom pieces - bring your own extrusion

I've been thinking that too. Someone on the internet is selling kits to make a fork jib from some 8020. I think a lot of people might be interested in that.

[prolix21]

I've been thinking that too. Someone on the internet is selling kits to make a fork jib from some 8020. I think a lot of people might be interested in that.

do you have a link to that? i've been messing around with a fork jig using 8020 and so far its less than graceful