How much unsupported length before stainless will flex?

[phantomcow2]

I just got two 5 footers of 1.5" dia stainless steel at my scrapyard. I've become very good at scrounging at this place .
So my question is, will i need to support this stuff over maybe 44" of unsupported length? I was goingt o use conduit and skate bearings for my gantry, but i would think the stainless would flex less.

[Geof]

If the diameter and wall thickness of the stainless is the same as the conduit the deflection will be almost identical. For identical situations; length, diameter, wall thickness, load, all steel based alloys will elastically deflect by close exactly the same amount. The difference between different alloys is how far they will deflect before the elastic limit is reached and plastic deformation occurs. Stainless tube will definitely deflect elastically far more than conduit and will return back to its original position when the load is removed because it has a higher elastic limit; it is stronger than conduit but it is not stiffer.

[phantomcow2]

Well, this is not stainless tube. THis is 1.5" solid round

[fyffe555]

this deflection question has come up before on the 'zone. Do a search - several people have put up formulas and spreadsheets to calculate this stuff..

more directly;

A 44" 1.5"dia SS rod simply supported at the ends and a 50lb centre load will deflect ~0.012"

A 44" 1.5"dia conduit same specs will deflect ~0.023"

If you can fix the end supports - that is not just support it at one point or through a bit of MDF then the deflection will half at least. If ~0.012" deflection over 44" and with 50lbs load is ok then you don't need to support it.

[phantomcow2]

THankyou fyffe555. It says Hastelloy with a long series of # after it, I believe thats a brandname.

TO fix the ends i was thinking of using 1.5x3" stock. So there is 1.5" contacting the rod at each end. ANd then get a set screw in there for good measure, would this be sufficient?

[Mcgyver]

Hastelloy might be a brand name, but in common vernacular it means “you just can’t machine this stuff”

it might be ok for what you are doing, but I wouldn’t want to do much work on it. actually you are lucky to have it identified in that you scrounged it - could have driven you crazy thinking you were just trying to turn down or drill a few holes in a bit of stainless

http://www.carbidedepot.com/formulas-machinability.htm

[phantomcow2]

Haha, actually yea i was not planning to machine it. MAYBE use the bandsaw at school and cut off the ends. One of the ends on both are a little rough, while the others are very smooth

[phantomcow2]

Wait, with such a low machinability, will it be able to even cut the ends okay?

[jeffs555]

TO fix the ends i was thinking of using 1.5x3" stock. So there is 1.5" contacting the rod at each end. ANd then get a set screw in there for good measure, would this be sufficient?

It migh help some, depending on how rigidly the rod was attached to the 1.5x3 stock. To decrease the deflection you need cantilevered supports on each end. This basically means that each end support is sufficient to keep the rod horizontal with no movement on the other end, even if the supports are removed from the other end. The easiest way to do this is with two rigid supports on each end spaced 6 or more inches apart, the greater the spacing the better.

[phantomcow2]

Sounds like that cantilevered setup will work, i can make blocks for it no problem. IM almost wondering if i would not be better off seeing what I can get on ebay for this stuff.
Hastelloy X on McMaster is not cheap...

[unterhaus]

Yeah, Hastelloy is a superalloy that is used in the turbines of aircraft engines. So your router will work at 2000 degrees. I'm not sure how it wears, but it can't be too bad.

I actually have this same question myself -- I'm highly qualified to calculate the answer, but I'm too lazy.

[phantomcow2]

I dont my router will be running quite that hot . I've been reading up, an alloy of this caliber must not wear too badly! Im tempted to list it on ebay and see what comes from it. So far, the only place ive seen it sold is McMaster.