Visit the forum instructions to learn how to post to the forum, enable email notifications, subscribe to a category to receive emails when there are new discussions (like a mailing list), bookmark discussions and to see other tips to get the most out of our forum!
Imperial vs Metric
  • Few conversations spark as much name-calling among nerds as Imperial vs Metric. 

    I tend to take a different approach. I don't want to HAVE to pick one. Why can't I use both? One is better for doing easy fractions, the other is better for converting anything into anything. My mind always gravitates towards the "all options all the time" solution. 

    There's no hope of the US changing to Metric any time soon, so the GVCS will have to work for people who use Imperial (biggest economy in the world) and people who use Metric (everyone else). One system that doesn't force either group to work with stupid numbers. What's 1" for one person is 25.4mm for another. Likewise what's 3mm for one person is 0.118" for another. I think this mathematical conversion could be replaced with a physical one where any piece that's properly manufactured would automatically "convert" from one system to another.

    Is there a way to find a system of dimensions that will work cleanly in both systems? For example, Grid Beams are in Imperial, which means the hole spacing is a weird, non-intuitive number in Metric. But a Grid Beam with clean Metric spacing would have a non-intuitive Imperial spacing. I don't think there's any obvious hole spacing that would create a round number in both systems.

    However, perhaps there is a simple way to "adjust" the hole spacing so that it "becomes" a round number in either system. An oversized hole could be chosen and spacers (half-moon shaped or solid with an off-center hole) could be used to locate the fasteners in the hole. Different spacers would mean the center of the fastener would be on a round number in different systems of measure. Along the same lines, flat sheets could be placed in between the beams to keep them the right distance apart. Change the thickness of the flat sheet and you change the distance between the holes in two beams. 

    Another interesting question would be what size fasteners to use. 

    It would probably need to be some sort of equation so that the combined list of dimensions could be scaled up or down to do projects in heavier or lighter weight classes.
     
  • 10 Comments sorted by
  • that's an interesting debate when global projects are involved, obviously metric makes the most sense in regard to computer applications while basic engineering imperial has minor advantages in regard to fractions; the world in general is moving towards metric with even big american groups like NASA choosing to adopt it.  Globally the United States, Liberia, and Burma are the only people to still use imperial.  
      
    A fairly well accepted international standard for example is thISO metric screw thread (e.g. an M8 nut), using this standard can make fixings much cheaper and easier to source, as far as i know they're widely available in the US and somewhat standard.


     
  • I'm in the US and I would love to go all metric everywhere.

    I think you have to start somewhere. But I also realize that if GVCS went cold turkey on metric it would just add to the existing challenges.

    Maybe the solution is to look long term. For now do whatever works to get the GVCS 50 completed. Then next year when those 50 are being updated/redesigned with lessons learned switch to metric across the board.

    One challenge at a time!
     
  • haha yeah, GVCS is already flying in the face of a greed and selfishness based culture; i'm sure they don't need the added hassle of also opposing a moribund measurement system :)
     
  • Not everyone here is against greed and selfishness (I'm not). Either way it's a philosophical/political subject that shouldn't have much to do with GVCS. I see GVCS as a-political. It's a project of much technical merit and is about doing not about philosophizing :-P
     
  • I slept on it, and thought maybe we can sort of do an end-run around the issue.

    One of the force multipliers of the OSE paradigm is being able to not only build things out of stock, but manufacture our own stock. That means we can make things whatever dimensions we want. 

    Another force multiplier is that we're designing EVERYTHING to work together. There's little need to worry about stock flat coming with inconvenient dimensions, because we can just design the mini-mill to produce stock in dimensions that work with our system. But that follows on to everything else. People DON'T NEED to worry about calculating dimensions when they build a GVCS machine. The dimensions are already calculated. It doesn't matter what measurements we use to design the thing because all the parts will automatically work with that measurement system. All a builder has to do is just line up the holes. Whether the holes are an inch apart or a meter doesn't matter. 

    For example: if we settle on some sort of regular grid spacing for fasteners, but we also assume a combination of flat and shaped stock material, the combination will be flexible. Take Grid Beam, but instead of bolting the beams right to each other, include a flat sheet between them. The sheet would normally be used to stiffen the connection (triangular brace) but, if a brace isn't needed, the flat would just be a small spacer. 

    Now, continue that idea through to the whole machine. No one would ever be allowed to drill an off-dimension hole in a part. Everything that didn't fit the pre-existing hole spacing (maybe a motor from another manufacturer) would use an adapter plate. If the system, and by extension the machines, were designed with that in mind it wouldn't be cumbersome. 

    With that in mind, I suggest OSE plan on using Metric dimensions wherever possible. 
    Also, I suggest that (when it eventually happens) OSE make it a policy to mark the stock parts. For example, push a piece of flat stock through a metal roller that will stamp dimensions onto it. That way we don't need to pre-cut any holes because the end-user won't have any doubt about where the holes need to go. They won't care what dimensions we used because they won't have to do any measuring themselves; the part is already measured. The worst thing they'd have to do is count down the part until they counted off the right number of marks. A system like that would be dimension-agnostic. We could even make up our own dimensions and no one would care.

     
  • sorry eukreign didn't know there were any Randian's here :) i just mean that being open and sharing is often seen as an anathema to american values - did you see CNN's pro-copyright advert? they might as well have said sharing is for terrorists lol.  
      
    but yeah the technical value of this project make it much more important than politics, although the social and political implications are an interesting thing to think about - at the end of the day even if we in the west don't adopt an open-source and floss strategy somewhere around the world will and as they say 'nothing's as powerful as an idea that's time has come' it will become established and it will change the traditional methodologies of the world like it or not.  Personally i think it's one of the most important events in human history since the adoption of the scientific method, a real game changer for development and manufacturing.
     
  • Matt,

     I think that's an interesting idea but it seems to add extra steps and would require a significant amount of modification and extra skill to produce parts with dimensions already on them (and of course building the components that accurately can stamp those dimensions).

     Also, I think in the foreseeable future most GVCS implementations will be hacked together components from what people already have around them and simply use the GVCS blue prints as guidelines.

     I think people are more likely to be building the LifeTrac and other immediately useful tools using off the shelf components. I think wider adoption of the induction furnace and steel roller will come after the more pressing tools would have been adopted.

     It's kind of a chicken and egg problem but I think reality, finances and pragmatism will cause most people to put the induction furnace and steel roller towards the bottom of their todo list, some may not even bother putting it on their list.

     - lex
     
  • We're open, we're just independent. Americans don't get that "the group is more important than the individual" thing.

    I only see the extra step of carving units into the rollers that form the stock. Compared to the size of the overall process that's nothing. Recycling metal into usable stock forms is not a small job. (let alone starting with raw ore)
    As much as the GVCS lists the "furnace" and "roller" like they're machines, what we're looking at is a whole facility. 

    At any rate, it's not all that hard to impress marks into a stock piece of metal. All you need is a roller with the correct pattern and some hydraulic power to force the metal through. It will come out the other side with whatever dents you want. It's a reasonably small machine; definitely no bigger than the ironworker. A machine like that could even add dimensions to stock metal that someone else manufactured, or that was found in a scrap yard.

    It seems to me the point of designing the machines with stock metal is that it's a commodity. Only people in the absolute worst poverty will be unable to access stock metal, and arguably those people shouldn't be building a million dollar set of machinery anyway. The GVCS is going to take investment and is going to have to pay for itself. It's not going to work as a charity project. 

    I agree with the idea that people will most likely adopt pieces of the GVCS, rather than the whole set. I'm looking forward to that. I hope the fully-functional GVCS inspires hundreds of spin off projects and I hope all of the machines are still useful outside of the GVCS. 
     
  • I come from a wood working background and one thing that I was taught during my training is the importance of a "story stick". Because if you measure everything from scratch by the time you're done you would have made enough 1/16" rounding errors to make a difference. If you using something like a story stick/jig then you'll always get it right.

    For example, if you have some stock from one foundry and some stock from another foundry and while they each produce consistent marks, they could be off between each other. A story stick doesn't care.

    If I purchased some stock and it had marks in it, I simply wouldn't trust it and end up measuring everything myself. Am I the only one?
     
  • also stock sizes are generally well reasoned, i don't want to be too hasty in commending the industrial status-quo but in some things the bottom-line obsession has made them rather efficient -  it would probably make a lot of sense for projects using a GVCS compatible model produce, store and trade blanks in standardized stock sizes.
      
    If metal-workers city is just over the hill then it's probably more efficient and more sensible to make some extra cotton, capacitors or luxury food items to trade with them - certainly within the current system it'd be much easier to produce revenue by setting up a webpage and selling straight-rod in uniform sizes rather than trying to make a market for some obscure measurements.   So yeah, every effort that can be made to align GVCS projects with accepted international and engineering standards should be taken, not only will it make things easier in the short term but it'll make things easier in the long term too.
     

Howdy, Stranger!

It looks like you're new here. If you want to get involved, click one of these buttons!

Login with Facebook Sign In with Google Sign In with OpenID Sign In with Twitter

In this Discussion

Loading