apollodriver

helllo dear Friends

i am currently working on my first diy bike jig stand clamp.

well i found some nice examples in the net: see jig stand clamp


https://www.flickr.com/photos/duncancycles/6857594481
https://www.flickr.com/photos/starrcycles/25393355534
https://www.flickr.com/photos/starrcycles/8216837165

well i like them more than the one of

a. VAR and
b. the competitioners - and others that are available

what wold you do here - what do you like at the above mentioned ones
and what would you improve

look forward to hear from you

regards

unterhausen

Are you putting a fixture on it to build frames? I did something similar to those to hold my frame fixture. I think people mostly do whatever is appropriate for the materials that are easy to find. That's what I did, all scrap bin parts.
If this is a framebuilding question, I'm going to move it to the framebuilding forum.

unterhausen

Moved the thread here to framebuilding from Bike Mechanics. I am not sure if OP is going to get any answers in either place, but it might be more likely here.

bulgie 

Go for the Duncan (Alistair Spence) design if you can, the extra axis of rotation is good to have even if you don't use it all the time.

My jig is mounted to a wall, can rotate on one axis only ("roll", not pitch or yaw). I'm constrained by lack of floor space. But I'd love to have one that tilted the other way (pitch).

If you don't need the pitch rotation, then it simplifies the stand clamp. Like the one in the first Starr link. Easier and cheaper to make.
The one in the second Starr link looks borderline awful. Grub screws that bite into a tube, that you want to be able to rotate? Ugh, go with the Duncan design for sure if you want that axis of rotation.

EDIT: I should add, I made mine plug into a Park repair stand, so I didn't have to make the whole thing. Only had to make the thing that goes into the Park stand's socket, and which bolts to the jig. Gives me a good fine adjust on the friction, so the jig rotates when I want it to and stays put when I don't want it to rotate.

I'm sure Alistair's design is as good or probably better, but my way was easy.

unterhausen

I should take a picture of mine. It's a lot like the pivot that Anvil sold for their fixture. And then I have a Park stand clamp on the other side for when I'm done tacking the frame and want to finish brazing it.

I wish I had balanced the whole thing better.

dsaul

I wondered who was looking at all of those photos on my Flickr page. Please don't make that abomination that I made for my first frame jig. That was just made with conduit fittings and other things that I had laying around my garage. I struggle with deciding if I should remove some of those old photos to prevent others from thinking they are a good idea. I mainly leave them there to show my progression from hacking stuff together with basic tools to making nice things with machine tools. I have made notes on some of them to advise people not to make them, so I guess I need to add a note to that picture as well.

The other Starr link is the one that I still use on my frame jig and it works well for me. I only tack in the jig, so rotation is all that I need to get access for tacking. Full welding takes place on a combination of work stand and welding table.

MRBoston

I don't want to hijack this thread, but thought I could make a couple of comments and ask a couple of questions:
The photo series on Flickr pages from dsaul was very enlightening for me regarding the possible methods for fixturing frame members. I have zero interest in actually making a frame myself, but since resurrecting my 1977 Nishiki and making it rideable again, I have taken more interest in the manufacturing and assembly processes involved. In looking at these frame fixture stand configurations, as well as seeing other photos of various setups for mitering/coping tubular frame members, a couple of questions came to me:
1.) In designing a fixture to hold frame members for tacking/brazing/welding, is adjustability created to set exact angular relationships on this fixture that mounts to a rotating stand, or are those exact relationships set up on (for instance) a welding table or other horizontal layout surface?
2.) Is the primary determinant of angles between tubes the actual milled/machined tube end geometry, or is that secondary to setting the angles, perhaps more precisely, on a fixture such as the ones under discussion here?
3.) Is tack-welding a preliminary process regardless of whether the frame is to be brazed or completely welded?

I suspect some of this may be simply a matter of preference, but I am just curious about typical processes.

unterhausen

Usually, tacking or pinning is done in the fixture and the final brazing or welding is done in some other kind of holding device. I have a park stand clamp that I use to finish brazing my frames with after I have tacked them. A fixture generally over-constrains the frame, so what happens is it gets pushed out of alignment when the joints are heated. If final welding/brazing is done with the frame tacked together but otherwise unconstrained, that results in a straighter frame. This may not be how it was done for your bike though.

As far as your other questions, for a properly built frame the milling and the setup in the fixture will match. With vintage production frames, all bets are off. It's not uncommon for inexpensive frames to have been built with essentially no mitering at all if they used lugs.

dsaul

MRBoston

1)In designing a fixture to hold frame members for tacking/brazing/welding, is adjustability created to set exact angular relationships on this fixture that mounts to a rotating stand, or are those exact relationships set up on (for instance) a welding table or other horizontal layout surface?

-The frame fixture is designed to hold the tubes at the proper angle and distance from each other to match the frame design. In my case the frame is designed in RattleCAD and I can print out a drawing with all of the frame angles and lengths. I can also print out a page with the necessary settings to set up the jig to match those angles and lengths. In my case, and many other designs, those settings are measured from the center of the bottom bracket and the bottom of the head tube. I start by setting the seat tube angle, then the horizontal distance from the bottom bracket to the head tube and the vertical distance from the bottom bracket to the bottom of the head tube for the front of the bike. Then the head tube angle is set. On the rear, I set the horizontal distance from the bottom bracket to the dropouts and the vertical distance from the bottom bracket to the dropouts(bottom bracket drop). I designed my fixture so that any of these aspects can be adjusted individually without affecting any other aspect of the design. That was a lesson learned from my first fixture design, where it took a significant amount of time to set up the fixture correctly.

2.) Is the primary determinant of angles between tubes the actual milled/machined tube end geometry, or is that secondary to setting the angles, perhaps more precisely, on a fixture such as the ones under discussion here?

-Once the fixture is properly set up, the tubes are cut to fit in the fixture. I'll use the angles in the design drawing to cut the tubes, but they get fine tuned with a file to fit the mating tube in the fixture. The fixture is the final determinant of the angles, until the welding starts and then all of that goes out the window and you get what you get after the heat does its thing of expanding and contracting.

3.) Is tack-welding a preliminary process regardless of whether the frame is to be brazed or completely welded?

-Frames are generally tacked using the process that will be used to join the tubes. Welded frame will be tacked with the welder and brazed frames will be tacked with a torch and brazing filler. Sometimes, lugged frames are drilled and pinned instead of tacking.