How would I secure a device inside an Aluminim tube - it has to be hand
fitted and practical to use. No bolts, glue or welding suggestions
Diameters range from 114mm - 202mm
The device itself is circular and lightweight, approx 2kg in weight
If you can't bond it or bolt it, friction is your only other option.
I'd suggest and expanding split circular piece just smaller than your ID.
Just cut the tube in one spot. Attach a small turnbuckle (rigth and left
hand screw with nut in middle) to expand against ID
I assume that by "no bolts" you mean "no bolts that go through the tube".
Large rubber bung with a hole in it, a pair of large thick washers almost
the diameter of the tube and a bolt that is long enough that you can do the
Slot the theaded end of the bolt (hacksaw) for a screwdriver.
Bolt through the washer-bung-washer sandwich, head of the bolt on the
Wingnut on the accessible side.
Keep the bolt from turning with a screwdriver, screw down the wingnut. The
rubber will expand and grab the sides of the tube.
You can use the same bolt to hold your device.
You neglected to state whether it has to be (readily?) removable, high or
low precision, or if this is a one-off application or a production lot !
That said, a piece of wire, slightly longer than the inside diameter of the
tube, held at its midpoint and forced into the desired location and oriented
across the ID of the tubing. The inserted wire will be slightly bent and
the bend will be free to pivot about the diametral line through its end
Or, with more holding force and potential for precision, a thin sheet metal
washer similarly inserted. Washer may need to have radial slits spaced
around its outer edge to reduce the insertion force and may be nearly
impossible to remove without significant damage. On the principle of
commercially available threaded inserts for common small sizes of tubing
. You may have
to make your own for larger sizes.
Or, a piece of wire, slightly shorter than the internal circumference of the
tube, formed into a split ring whose outer diameter slightly exceeds the
inner diameter of the tubing, compressed and forced into the tubing to hold
by friction or into an internal groove for greater precision and retention
force. Also commercially available.
A simpler way to expand the split sleeve is to tap a hole parallel to the
axis of the tube where you plan to slit it with a taper tap, tapping only
part way through the sleeve. Then slit the sleeve through the tapered hole.
When you drive a set screw into the hole, it will expand the sleeve and lock
it inside the tube.
What about the tapered wedge that holds the front handle bar stem
on a bicycle? Simple, holds well, easy to adjust.
Keep the whole world singing . . . .
DanG (remove the sevens)
Make a thick (.375-.5") washer about .002" smaller in diameter than the
inside of the tube. Drill and tap the end for a 1" tapered pipe plug. Cut
the washer almost the full length of the washer with a band saw through the
center of the tapped hole. If you would like, you can rotate 90 deg and make
another cut so that the face of the washer looks like a sliced pie. You have
just made an ID collet that is tightened by inserting a pipe plug.
It's really so simple I'm surprised you had to ask.
Hold the tube in your right hand. Pick up the device with your left,
and quickly insert it. The heat from your hand will expand the tube,
and when you remove your hand the tube will shrink on the device. To
remove it, just expand the tube with the heat from your hand.
What could be easier?