shiples@comcast.net wrote:
> My steel suppliers don't stock tubing that provide slip fits, either.
>
> It's not the weld, it's the selection of ID/OD that's generally available.
> It's the standard dimensions of seamed, seamless, DOM, and whatever
> that keeps you from buying tubing that you can connect with slip fits.
>
> There were several of us in a beginning welding class that thought that
> slip fits would be a great feature in our projects, but standard tubing
> doesn't
> work that way.
Here's my rambling story of mixed success...
I did get some tubing that was a sliding fit. It was square mild
steel, with a visible seam in the middle of one seam.
I used it to make a pair of "safety rails" on my hoist platform. The
Midget is so narrow that the margin of error to fall in the middle if
the hoist is only a tire width. (basically, the hole in the platform is
about the same width as the inside tire-to-tire width of the midget, so
four inches left or right and you fall in!)
So I put rails along the inside of the platform. When I drive up, the
inside of the tires run along the rails and the car stays on the platform.
However, I wanted the rails to stick up 10cm or so when the platform
was on the ground, but be out of my way when I was working on the car.
So I made the whole rail slide up and down, using the sliding tubing.
So my bar is the whole length of the platform (4m?) and has two
vertical 30cm pieces welded on near each end, so it looks like a very
wide and short pi symbol. (the 3.14 one from high school)
The two vertical pieces then slide through a short 10cm length of the
"outer" sliding tube.
Ok... still with me?
The plan was that "good old gravity" would do the work. Lower the
platform, the safety rail bottoms out first and rises above the surface.
Raise the lift, and the rail sits on the floor until it's down then the
platform lifts it up.
Problem... the "sliding fit" is far from frictionless, it turned out
to be a little irregular. Sometimes it would jam, and I'd have to stomp
on it, etc. etc.
I tried greasing it for a while, but that made a mess.
I ended up taking the angle grinder to the outer collar, slicing it
up down one side, and prying it apart to make it bigger.
It works fine, but all this to say, even when you get a sliding fit,
sometimes it takes some persuasion. Have a big hammer handy.
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