A Project Quest

  • Thread starter Thread starter Bill Gruby
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By the time everything is on the table we easily gone over 50 lbs. Is the lift out really going to be that much of a problem? Just thinking out loud. LOL

"Bill"
 
In reality, probably not, Bill. But part of this project is to stimulate thinking and get people involved at least vicariously. I'm just throwing out what is going through my mind to hopefully encourage learning about the design process. Even on what may appear to be a simple mechanism such as a table that moves back and forth, once you start putting in place the theoretical desires vs practicality limits....the wheels start turning. At least I hope so. That's one thing I will enjoy on this thread. Of course, at some point, there will be less and less room for outside changes and things will bound by previous design decisions. But until then, I like the community concept of this project and seeing as many as possible put in their thoughts.

And to all you who think you aren't "good enough" or don't "know enough" I say "Hogwash!". This is your rare opportunity to engage in some work that isn't often even available to you. Talk openly about your ideas. Ask"dumb" questions. How else can you grow? Take advantage of this, please.

To Rick, on the ballscrews. I'll tackle my own answer in another thread in more depth, perhaps, but offhand my decision would be against it based on overkill, the need for right angle gearing to be incorporated, same issue on easy table lift off, and expense. My hands aren't working all that good right now due to an inflammation of my ulnar nerve where it passes through the cubital tunnel, plus my laptop keyboard (part of the cause of the nerve problem I suspect) is getting to be hit or miss on characters, requiring lots of re-typing. And I can't type in the first place. I am taking meds for it, so if/when that helps, I will go into a verbose (bad habit of mine), long winded explanation. Meanwhile, hopefully someone else will also tackle your question. I'm glad you asked it.
 
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Tony Wells said:
I don't know about an actual requirement..........that's on the designers, lol..............but yes, it would sacrifice that. Personally I have not had many pressing needs to remove a SG table, and the work required that prompted the need far outweighed the inconvenience of stripping cables or whatever drive.

But, if that were a design requirement in this case, then some consideration might be made to make the driven section integral with the table and the drive easily removable in the case of table removal.
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You could confine the rack with a guideway and have the table engage it via pins. The pins could attached to either the table or the rack.
 
The only time I have seen the table lift is when aggressively reversing direction at the end of travel. I think it's really not something to worry about.

Ball screws are great for accurate linear positioning, but as a reversing and relatively high speed drive system I think it would be a bit of a problem on a hand cranked machine. Then there is the problem of keeping the grit out of the works, surface grinders are messy machines
 
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Many of these ideas are good , some great,but we have to consider one other thing. We can't get to complicated on this because it not only increases cost considably, but over complicated systems pose a challenge to build. We need the simplest solution that will work the best, WITHOUT sacrificing quality. I am not convinced the lift will be a huge problem. Many surface grinders have a table that just sits on the ways, but they are also MUCH heavier than ours. All that said, I'm going to watch a bit and see what else we come up with. There is a lot of great thinking going on here.
 
mark_f said:
Many of these ideas are good , some great,but we have to consider one other thing. We can't get to complicated on this because it not only increases cost considably, but over complicated systems pose a challenge to build. We need the simplest solution that will work the best, WITHOUT sacrificing quality. I am not convinced the lift will be a huge problem. Many surface grinders have a table that just sits on the ways, but they are also MUCH heavier than ours. All that said, I'm going to watch a bit and see what else we come up with. There is a lot of great thinking going on here.
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Another loony idea: a chain drive. A sprocket at each end of the base, one free-wheeling, the other driven by the crank. The chain would be stretched around the sprockets with a plate in the middle with a pin to engage the table (or a hole for a pin on the bottom of the table). The plate would slide on the base or ride just clear of it. The chain and sprockets are cheap off-the-shelf parts (I'd salvage them from junk). No lift and no precision work. Could use toothed belt instead of chain.
 
I agree with Tony that some of you will miss out on a real opportunity here. As said we will listen to all and respect what they have to say. This is your project as much as it is ours. Every one of you knows something and we want to hear it.

"Bill and Mark"
 
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Mark, nearly all design work is a compromise. At this point, early in the process, the idea is to explore. Once the resources are exhausted, the choice can be made to include or exclude what fits the actual requirements, but not necessarily fits the ideal(s). On this project, the final decision(s) rest with you and Bill. The rest of us are here just to give scent to possible other avenues.

John your idea isn't loony. I thought of it earlier myself. I have used many, many feet of chain in various drive systems. Usually just one way, to sync with conveyor systems for example. Or for elevation of different sections of machinery. It's worth considering here, I believe.
 
Tony Wells said:
Mark, nearly all design work is a compromise. At this point, early in the process, the idea is to explore. Once the resources are exhausted, the choice can be made to include or exclude what fits the actual requirements, but not necessarily fits the ideal(s).
Click to expand...
Tony ,
I totally agree with you. None of the ideas are out of the realm of possibility. I want to hear everyone's ideas. Then Bill and I can decide what course we want to take. The advantage to this great thinking pool is we can look at so many ideas and come up with the best solution as opposed to one person trying to think everything out.
 
I agree with the idea that all the weight if the table, vise and such will cause lift to be a non-issue, however, here's some ideas.
  1. someone pointed out that a rail would not make contact soon enough. I immediately think "gib" to myself.
  2. rollers could be used instead of a rail. Since these are in contact at all times, you should be able to set them for zero lift.
  3. someone has already suggested putting the pinion above the rack. The only good way to do this that I can see is for the rack to be on the outside edge of the table (pinion stays still right?) this should then take care of lift all on it's own as it will physically be holding the table down. Too much acceleration would try to lift the pinion up and force the table down into it's ways. If the rack were underneath the edge of the table, you could have lifting issues, but the other way solves that.
  4. Speaking of that, why does the rack have to be orientated up or down? Once again place it on the side of the table (in or out) but have the rack facing to the side. Now any forces from the pinion are directed to the side instead of up or down. The 90 degree change makes the drive a little more complicated though.
 
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