jerry4

I have yet to build my first bike. I am wondering about using jigs to hold the assembly for brazing. If the frame has to be cold set after removal from the jig, then what has the jig accomplished?

I really like the idea of tacking the assembly on the layout table. If one were to use several tacks, cold setting after each one as required, it should be possible to keep things straight. There would be no locked in forces ready to spring as soon as the frame is removed from the jig.

BTW, I am selling my mill, lathe and Tig Welder. Having a machine do "it" perfectly no longer gives me much satisfaction. Jerry



Jerry

unterhausen

most builders tack and then finish joining outside the jig. So the jig itself doesn't have to be very rigid. I built my tandem with just a jig that held the bb to the seat tube. Everything else was done with straight edges/sighting.

I wouldn't sell those tools unless your kids are going hungry. They are extremely useful

NoReg

Depends why you build. You seem to suggest it is about gaining skills and challenge for you, which is fine. Somewhat the same for me. For others it is about getting th job done at a high level and fast enough to keep in business. What if you came up with a way of making better frames than anyone else, but it was too easy, would you use it?

Jigs mean a lot of different things. Some of the better jigs are multifunctiona and will allow you to build without subsequent cold setting, or minimal setting. They can't hold the frame against massive forces that would move the joints around, but if the correct sequence is followed they can reduce the post forming to a minimum. They can also be pretty useful at getting parts through the process.

jerry4

I am retired and want a different "feel" in the shop. I am done with the machine shop approach. A friend is buying the mill and lathe. He says I can visit them if I need to make something. I built several aircraft fuselages prior to buying the machinery and several more since so I have some feel for the different approaches. Jerry

NoReg

Same kind of issues in the aircraft biz with some guys doing all machined copes, and tig welding, and other guys going at it with cutters and blobbing on the gas welds. I like to do it all ways.

Canaboo

I have gone jig-less when working with bamboo. A level and sighting against a set line is pretty useful for reference. So far the bikes ride perfectly straight.

fietsbob

fabricated a lugged frame in the 70's with out much more than a bench vise, and some Borrowed heat and the local Community colleges rosebud torch, (metals arts casting machine) to get heat to do the fork crown mass..
happened to Visit thru Nottingham 15 years later , as a traveler on a bike I was the guest of a man there who built frames for pro level riders , without much more than the torches to make the heat,
a wall of half round files and a bench vise in the basement of a 300 year old English house..

NoReg

With bamboo there isn't the heat distortion problem so it doesn't go as catatrophically wrong from that anyway.

https://www.youtube.com/watch?v=TMA8X5pk2kI

Canaboo

That's true. Interesting that the alignment by eye method is used by pro frame builders as well. I tack glue and then align against a straight line and lighted background just as they do in the video.
i

ftwelder

Although I use a conventional alignment table with BB attachment I really suspect that having the head tube, seat tube and rear wheel on the same plane are all that really matters. I have mastered mitreing tubes with a chop saw and 20" disk grinder. I don't do it often but it's pretty liberating. Most of the frames I make are extremely complicated and elaborate set-ups are often required so that is where I find my challenge. It took me about four months to build 25 of these. *edit Having trouble with flickr and photo posting, my apologies*

https://www.flickr.com/photos/frankthewelder/4683157591/

NoReg

Very intricate!

unterhausen

flickr and BF don't quite have the same idea about sharing images. You need to get the location of the jpg file from flickr and give that to BF. I usually get it from "share this" "get the html"
that's how I got https://farm5.static.flickr.com/4044/...a9e1ecc6d7.jpg

A lot of work in that frame, nice

ftwelder

Thanks, I make everything from raw stock and form the tubes in-house. The aluminum part of the frame is about seven lbs. (front and swing-arm combined) I think DH and cyclocross frames are the best frame applications for aluminum. It took me about five months to build 25 of those.

Oh, so you used the HTML option rather than a link? I used to have zero issues with images until the recent changes to flickr.

unterhausen

I cut the name of the .jpg from the "get the html" option. I don't use the whole html, have never gotten that to work.

tuz

whoa nice frame! Seems impossible to do

Regarding jigs, one thing I like about the ones I have is their relative adjustability. If you mess up a few mm in the fork length you can move the DT-HT angle or BB drop a bit while conserving your desired HT angle. So I guess it saves a bit of time. But redoing a drawing or a CAD doesn't take too long.

Another cool, minimalist and drawing-based jig is the one Alex Meade makes. And +1 on having a lathe/mill around! I don't use them often but I'm glad I have access to them.