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  1. #26
    Randomhead
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    it's pretty clear that those aren't vees on the sides and bottoms. They are asymmetric, for the rubber bands shown holding the tube into the vees. I'm pretty sure that the intent of the designer is that you change the height of the head tube and dropout holders to compensate for tube size. You can see that the head tube holder is slotted to allow this and easy removal. I guess they couldn't figure out how to use rubber bands to hold the tube if the vees pointed the right way.

    I don't think a large standoff jig will work well with these materials. I'd be really interested in knowing if the designer ever used this or if they have ever built a frame. Wood doesn't catch on fire very easily, or you could avoid any issues by pining the frame together. You can go to somewhere like Shars or Enco and buy precision vees for a reasonable price and then use mdf as a backplane. It's so cheap that you just replace the mdf every time. Alternately, you can glue together 3 sheets of mdf and it will be pretty stable under most conditions. And the vees would always be useful.

  2. #27
    Senior Member JonnyHK's Avatar
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    Might work well for cold processes like fibreglassing. I can see this working well to hold the key points (head tube, bb, dropouts) for a bamboo frame to be tacked together pretty accurately. Might need a mod to help you locate the seat post since you can't rely on the tubing to be even in shape.

  3. #28
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    I have three suggestions for home made jigs, it was a subject that I gave a lot of thought to at one time. I started out studying ways to make frames without jigs, and moved on to jigs just for the fun of it, nothing to do with the idea that a jig was necessary.

    First thing is to have an objective for the jig. I came up with 3 or 4 things a jig would do, and held with those objectives. Basically they were similar to Anvil jig. I can't fully remember what the objectives where, but:

    1) Hold parts firmly so that they can be joined. There are arguments all over the place about whether this is possible or desirable, but one thing that doesn't need arguing is that it is possible to make a jig that does this. So for instance there are arguments over whether laying bikes out to a thou is either possible, or whether it is self delusion cause even if you could do it, the parts are not at that level anyway. But you can get a granite table that allows you to try. Or one can argue all kinds of ins and outs about tweaking frames, but one can't argue that frames can be fixed andthen bent with a big lever. Same thing with jigs, they can be made strong enough, what happens next is another mater.

    2) Be easily adjusted to correct position, so the frame is in essence a measurement device. If parts fit when mounted on the jig the bike can be made to correct dimensions. The jig measures the bike not the other way around. Though even the Anvil doesn't do that completely. And this also means the jig is easily reconfigured to the next frame. (maybe that is two things...)

    3) The jig helps design and visualize the bike. Obviously not necessary for those on their 400th 23" road bike, but for beginers, and guys who like to mess with oddball configurations it is nice if one can build the bike in the jig before tacking anything.

    4) Access for whatever build method you use

    Etc...

    The three home made jigs that did this best for me were:


    1) Jigs based on milling machine tables. These tables are cheap, and they can be fit together at 90 degree angles, they have tons of stuff to fix stuff to and they are the backbone to a lot of other shop fixtures, like wheel truing, fork building, frame straightening, etc... You can't get 2 without a lot of additional machined parts, but 1 and 3 are easy,

    2) A jig that was developed on the old framebuilding forum, there were full CAD drawings and a version for welded backbone or machined backbone.

    3) A proper wooden jig. A lot of stuff is built to extreme accuracy on wooden jigs, but they aren't the jigs bike people normally come up with, which commonly either don't come near to real jig performance, or even attempt it. It is doable to come up with a "wooden" jig, but for it to have all the main jig features, it would need some minimal metal work as well. You end up needing a person to build it who knows how to work in wood, as a machinist, and is a frame builder to boot. Moreover they need to know how to spot successful solutions from all these disciplines. So I don't really see a wooden jig catching on. Wooden jigs are commonly used to help with "jigless" construction but that is another subject.

    The only one I built of these was the milling machine version, and then I moved along to a "real" jig. But it is still one of the most useful things in my shop, which is another cool thing about it, it can be used n the shop, or sold to a welding outfit.

  4. #29
    Randomhead
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    I have built a couple of bikes using a milling machine table and some add-ons. It worked pretty well, and the parts I made for it moved on to my current jig. The table I used is quite small and so I have it on my bench for rigging up one-off projects. I got t-nuts the right size for the t-slots, and those are really useful.

  5. #30
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    Yeah, those t-nuts are really cheap in the various chinese versions, and are relatively good quality.

    Mudboy, I have a lot of pics of different home made jigs that I accumulated over the years. I also have copies of the files for the number 2 jig I mentioned. It was made by "Mike". If you want any of that stuff for your site, PM me an email I can send it to.

  6. #31
    Andrew R Stewart Andrew R Stewart's Avatar
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    Quote Originally Posted by JonnyHK View Post
    Might work well for cold processes like fibreglassing. I can see this working well to hold the key points (head tube, bb, dropouts) for a bamboo frame to be tacked together pretty accurately. Might need a mod to help you locate the seat post since you can't rely on the tubing to be even in shape.
    This is exactly what I would NOT do/trust with this jig. In general to trust a jig to be accurate is a huge assumption. To trust a jig with so little loacating surface, that is also made with low precision methods (saw blades instead of surface grounding and threaded rods instead of ground and coned) and uses a flexible two piece base plate is just delusional.

    One of the issues with bonded frames is the ability (or inability) to align after "tacking" the pieces in position. If this was something easy to do we would see far straighter carbon frames coming out of the major players. That the initial fixing device (or mold) is what is dependent on the straightness and that it doesn't seem to work for the large scale production of bonded frames might suggest that trusting a jig is not the best approach, for bonded frames. Andy.

  7. #32
    coprolite fietsbob's Avatar
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    Better keep that fire extinguisher Real Close at Hand..

  8. #33
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    Better still get a pal to hold it for you. I have set the shop floor on fire a few times, and it is burning away for a little while before one notices. I have concrete floors, but maybe those fatigue mats aren't such a good idea...

  9. #34
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    For noobies on a budget, They might want to google on Taylor Brothers or Taylor Cycles. There are a number of sites with photos of these incredible builders laying up singles and tandems with nothing more than a flat table and various v-blocks (probably from steel, but can't tell for sure) holding the tube centers the same exact distant off the table. If I had seen those photos back in 1974-75 when I built my first tandem jig for brazing, I would have done it their way and saved a lot of time, space and money. Looking back, my gut feel is that the results would have been just as good.

    Today with the ready availability of low cost quality TIG units and the wide available of tubes made for TIG-ing, the gut feel goes up even further. /k

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