Bench Tube Construction

[SteveMaryland]

Yes, the above pipe-in-tubing arrangements would be very heavy and likely impractical for that reason. But numerous other arrangements are possible, at lower cost than replacing with legacy tubing. It does seem to me that more SS rigidity is in general highly desirable, while more structure flexibility beyond what we already have, is hazardous.

IF SS intends to also use .050 on the way tubes (?), a potential problem remains. Here is my concern: the cross-section of circular tubing will distort (from circular) when the tube is under a bending load. It will go elliptical, slightly. The thinner the wall, the greater this distortion. Solid tube would distort the least. Headstock is locked by applying a friction clamp on the way tubes which depends on the circular tubes remaining circular. Could .050 way tubes, under bending loads + clamp load, distort (from circular) to the point where headstock friction lock is reduced or lost? That would be a hazard.

And now I learn that the Power Pro headstock is 9 lbs heavier than the legacy headstock. That adds to the concern.

[reible]

I fear that this tube design is not a good idea. If someone has a cad program with the built in capacity it would be pretty simple to model and test. I also fear that shopsmith has not done that. Sorry I lack confidence in the current company due some examples of flaky designs.

I did learn how to do that is school but no practical experience as my work at Bell Labs took another path. My recall after 48 years is pretty bad and getting worse by the year, some of which is due to age.........

I do know that about the time I retired there was a shift from doing the calculations by hand or specialized programs were being replaced with cad programs that did almost the work for you. How ever you would still need to have an idea of what steel was used and dimensions of course as well as expected loads etc.

Speaking of loads, how about the massive 35 pound universal lathe tool rest?

BTW years ago, maybe before this site existed another shopsmith users group existed. We had a lot of discussions about adding weight by loading the tubes with lead shot. You could at the time get bulk lead shot cheaply and that and plugs in the tubes could add a lot of weight but still be able to be drained for moving or other reasons with little effort. There are programs that give the amount of shot and how much weight could be gained. Now I expect lead shot is obsolete but what ever replaced it should work about the same.

It also wasn't uncommon for users to add sandbags to the shopsmith, at about 30 pounds each, well you get the idea.

And by the way people had looked at loading both sets of tubes since their use was only for the lathe.

One last thought, if one were to load in tubes then this becomes much more complex to model. While I was in school a company came in with a problem they had. A church window they had designed, talking massive glass wall now, well wind storm blew it in. Turned out they modeled as a single aluminum extrusion and ignored the thermal break, totally different problem. Tubes in a tube will exhibit a totally different result depending of many many factors, they for sure will not be totally additive.

Ed

[SteveMaryland]

Problem with calculations and FEA is that they provide quantities but then what? FEA will tell us that thinner tubing will deflect more than thicker tubing. We already know that. Question is how much is too much, and what is the criteria for "too much"?

This is why prototype testing provides such answers in many cases, including this one. Has Shopsmith tested .050 tubing under real-world conditions? And are they intending to use .050 for way tubes? I don't know. My concern is that they have not, and/or the decision was soley driven by cheaper.

I like the tube-stuffing idea because it is a cheap hack that most Shopsmith owners could do, that could fix a problem and also improve Shopsmith performance/stability/safety. What a deal. But it might also be just a solution in search of a problem.

Whatever people may try, don't stuff anything in the tubes that could distort the circular cross-section. If any casting fluid is used, it must be zero expansion. Packed sand, as Ms. Brenda has suggested, may be the best bet in the final analysis.

So if any of us Shopsmith owners have ever been told to go pound sand, now we know what they meant...