I'm starting to work on building my own jig. I was planning on something very similar to the "simplest frame jig" on instructables, but I thought some inspiration might be helpful. If you have a minute, could you show me yours?
Thanks!
Here's a shot of my setup. Inputs are: BB drop, CS length, front-center, fork rake, ST angle, HT angle, and distance to the bottom of the lower head lug. Close-ups here:
Blaster, I've not weighed it, but it's likely north of 100 pounds. All of the big flat parts are made from MIC6, but there's quite a bit of flat-ground steel and stainless in there as well. The fixture lays back flat on a pivot (not shown) and locks into the flat position for easier setup. It also can rotate freely in the plane of the frame for easier brazing access. Both axes of rotation are balanced, so the weight is not noticed.
This one I built about 10 years ago, now being used for carbon assembly. If I build another one I'd add more offset for better tacking access. I'd probably get all the parts waterjet cut from MIC6 plate as well.
I find it interesting that for the most part people seemed to have coalesced around the plate type fixture. That is either a structure on the drive or non-drive that has bits that hold the frame offset from that.
There are other designs such as the beam type where there is a central beam along the bottom of the frame and you build upwards (many motorcycles jigs use this) or the picture frame jig. A very common design in the past. I believe Ant bikes uses this. Also, Doug Fattic's fitting jig which work from a surface plate and Alex Meade's simple fixturing solution from a surface is also excellent.
IMHO a solid, flat surface is a much more important thing to own initially than a dedicated frame jig.
All fixtures have advantages and disadvantages. but for ease of construction if I had to do it over again and was working with minimal equipment I would most likely use the central beam idea or the surface plate solutions.
I find it interesting that for the most part people seemed to have coalesced around the plate type fixture.
I have no idea how many of which commercial jigs are sold, but this observations seems to correlate with my hunch that Anvil/Bringheli/Henry James might be the most popular? [/wild speculation]
I have no idea how many of which commercial jigs are sold, but this observations seems to correlate with my hunch that Anvil/Bringheli/Henry James might be the most popular? [/wild speculation]
I don't know how many jigs the others sell, but I do know that the 67th Type 3.1 Journeyman is on the proofing table now to go out tomorrow and we started selling those in May '11.
A man must have enemies and places he is not welcome. In the end we are not only defined by our friends but those against us.
Ah, a two-stage differential jig. I played around with that design for a while, and was wondering when I'd see something like it. I think it's a great design for the garage/basement builder that doesn't have a lot of room.
You're spot on regarding the real estate. Super simple and with good rigidity and repeatability.
Originally Posted by dr.welby
Ah, a two-stage differential jig. I played around with that design for a while, and was wondering when I'd see something like it. I think it's a great design for the garage/basement builder that doesn't have a lot of room.
I don't know how many jigs the others sell, but I do know that the 67th Type 3.1 Journeyman is on the proofing table now to go out tomorrow and we started selling those in May '11.
I'm going to have to guess that ~100/year puts you at/near the top. [/less wild speculation]
Slick. Looks like you have some measuring tapes glued on there, so I assume you have a spreadsheet to calculate angles and positions. And then do you use a giant protractor or and angle finder for the seat tube?
I don't know how 3wfab does his, but on mine, you draw a nice 2d drawing in CAD. I use AutoCAD at work, so I've got good access, and 2d drafting like this is pretty quick and easy. I draw the frame out as it would sit in the bike, and then you have an offset concentrically from the bottom bracket. For mine, you basically draw a line from the center of the BB to an extension line from the head tube (perpendicular). Offset that by 3" below the centerline of the BB. From there, it's really just basic geometry to get all the lengths of tubes you need.
To do the rear triangle, you extend your "offset" line backwards past the dropouts. Draw a line from the center of the dropout perpendicular to the offset line. That tells you how far back along the fixture spine to set your dropout mount, and how far up from the spine you need to set your dummy axle holder.
It's all actually pretty slick and pretty simple to use. It's based off of a fixture that James at Black Sheep built for Rob Pennell (Badger) several years ago. Another friend has that fixture now, and I just want to build my own to a)not have to borrow his for 2 weeks at a time and b)make a few minor improvements to have more room to get the torch into places (especially under the BB).
BikeCAD here. Use the Bicycle Machinery reference for setting HT. From there, I set the ST angle referenced off of the HT (which is 90 degrees).
I use a digital angle finder to dial in the ST, which is actually the rear triangle.
I build the rear first, simply because I can get over the 'hard' sometimes frustrating part of the build first.
I've built several variations of plate style jigs and IMO, that design utilizing the 80/20 stuff is way more involved than what I want to deal with. 80/20 isn't true and a PITA for jig setup (plate style).
I'm loving this beam style. Its really simple and 'open' to work around.
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Originally Posted by dbohemian
