Another jig thread

[jclay]

Food for thought.

First: From the shop of David Yates, a frame jig built from common & inexpensive materials, simple to build with minimal need for machined parts.

http://www.daveyatescycles.co.uk/upl...intriangle.JPG

Second: What I built with aluminum plate from the scrapyard, a bunch of jigsaw blades, some machined parts from Joe Bringheli and dummy axles from Anvil.

Attachment 69837

A long time ago I had a plywood jig much like the one above in its essence. It worked quite well and frankly I'd be perfectly happy with it now, as long as I had my surface plate to align tacked sub assemblies prior to brazing.

[bencooper]

My jig is similar to the Dave Yates one - I've made a few upgrades and improvements since this pic (and moved workshop) but it's a simple design made from box section steel. Builds straight frames though.

image.jpg

[Dallas Tex]

,i dont understand why no one has done a modern take on the traditional sizing board type

Doug Fattic did an excellent version

http://ninelittletubes.files.wordpre...05/epv0131.jpg

I don't particularly like, but i have a buddy who has used everything out there, and he swears by it.

[Andrew R Stewart]

Food for thought.

First: From the shop of David Yates, a frame jig built from common & inexpensive materials, simple to build with minimal need for machined parts.

http://www.daveyatescycles.co.uk/upl...intriangle.JPG

Second: What I built with aluminum plate from the scrapyard, a bunch of jigsaw blades, some machined parts from Joe Bringheli and dummy axles from Anvil.

Attachment 69837

A long time ago I had a plywood jig much like the one above in its essence. It worked quite well and frankly I'd be perfectly happy with it now, as long as I had my surface plate to align tacked sub assemblies prior to brazing.

This. It's the builder that makes the frame right/straight. Not the tools. Good tools just makes this go faster. Andy.

[Michael Gordon]

Be The Ball.jpg

Be the jig Danny

[Doug Fattic]

I don't understand why no one has done a modern take on the traditional sizing board type

I’ve spent hundreds if not thousands of hours over years – with the help of various other specialists – designing and having laser cut a modern version of the British sizing board. I got my 1st one from Johnny Berry’s widow in Manchester and it has gone through many revisions. Mostly I’ve added bells and whistles that make it easier and faster to set up and hold tubes. When I was apprenticing in England in the 70’s, I visited a large number of builders and many of them used some version of the sizing board that F.W. Evans claimed to have invented before WWII. It is my go to fixture that I like better than my Anvils and Bike Machinery Hydra. Here is a shortened list of its features.

1. My fixture is the equivalent of an adjustable full-scale drawing that can also hold tubes. It can convert a person’s seatpost/seat and stem position into a custom frame design. That makes it possible in real life to see if everything is in proportion (like how many stackers are required above the headset).
2. All major measurements can be read and set directly on the fixture like tube lengths and angles. Whether it is fork rake (I spin 2 hex pieces together to get the measurement I need) or how many degrees of slope I want on the top tube, almost everything can be set by the fixture tooling itself. This makes it fast and accurate to set up or reset.
3. A tube miter’s accuracy for length and angle can be checked against the fixture itself (instead of using the tube to set the fixture). If it’s off, either the miter or fixture can be adjusted.
4. The alignment of the tubes in the fixture is based off of the alignment table it is sitting on so the fixture itself does not need carry the burden of accuracy. The V blocks holding the tubes can be height adjusted to put everything on center.
5. While I made mine with all kinds of features (like reading directly how far the nose of the saddle is behind the bottom bracket or the straddle height of the top tube) a simple version without measuring tools works very well. It just takes more time to set up with a ruler. It could be made out of various materials including wood (with protective sheet metal in between to keep it from catching on fire).
6. It is very intuitive since it is a literal representation of a frame’s dimensions and nothing is abstract (no trig to figure out where the bottom of the head tube needs to be). There are points that represent all major lengths. If the front clearance is not enough, it is easy to slide the head tube piece further out without disturbing its angle (or change other factors).
7. It needs to be understood that all I do in this fixture is spot tubes together and then check its alignment on my flat table. I want the freedom to braze a frame in any possible position without fixture restrictions. It is especially important to visibly make sure silver has come down all the way around inside the bottom bracket shell. That isn’t possible if the fixture is holding the shell.

I’m not a critic of other designs that follow a different logic if it works for someone else. However there is no way I would want to build frames on most fixtures I see. I would miss the features I have in mine. It would drive me crazy to loosen a bolt to lengthen the top tube and lose my head angle. Also – unless a fixture is really, really well made – I don’t trust them to perfectly position the rear dropouts so they will accurately center a rear wheel within less than half a mm. Small variations in chainstay length are magnified out by the rim.

Although I do sell this fixture I don’t go out of my way to sell them. I designed it to please me and once the work was done the laser cutting company can use the same program to make more. Mostly I make them available to students and others that realize its advantages. It greatly increases the price to have it made out of stainless steel (it actually weighs 65 lbs). It is perfect for teaching my framebuilding classes because it makes visualizing how a frame is designed easy to see and understand. Although this kind of fixture has a great track record in the UK, it is not like American fixtures so its advantages are not often readily apparent with just casual observation.

[duanedr]

Glen,
Interesting and effective approach...with more integration of 3D modeling in bicycles, this is a natural progression for computer savvy builders.

rody

While researching jig designs I came across this thread. It seems the next logical step from designing the jig settings with the frame, is to devise CNJS (computer numerical jig setup - patent pending) with servos at each joint to set the jig up based on the frame design in BikeCAD. Now the jig has to have USB as well as purge fittings!