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My idea is for an alternative type of expanding bolt. It
consist of a bolt (whose head
protrudes very little past it's edge. onto this bolt is
placed conical
washers so that the large ends face away from the bolt
head. A large diameter washer follows these with a
nut securing all of this
in place. The end of the bolt it
flattened so as to be easily gripped by locking pliers.
To use said bolt one places it in the hole head first and
grips the flattened end with a pair of locking pliers. one
then
uses
a wrench to turn the protruding nut. this pulls up on the
bolt compressing the
stack of conical washers and forcing them to expand and
grip the
sides
of the hole. Alternatively should you want to use said
bolt
with a power drill or any bitted drill whose bit goes over
bolt heads you could hold the nut and have a the
protruding bolt tip bitted.
Dynaset drop in anchors
http://www.ramset.c...choring/Dynaset.pdf
Not exactly what is described here - just showing that there are already designs that do this job quite well. [Custardguts, Jan 07 2010]
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Annotation:
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//compressing the stack of conical washers and forcing them to expand and grip the sides of the hole// |
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Methinks perhaps you underestimate the forces required to significantly expand a presumably steel washer like that. Something like this could be used for low-clearance holes in a steel structure (although I don't know why this would be more advantageous than other existing fastening methods). |
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What [Custard] said. But the conical washers could be
designed to be more easily "spreadable". |
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Presumably you've already encountered other expanding
bolts? There are some which have a sleeve which, as the
bolt is tightened, is shortened and expanded outwards -
sort of similar idea. |
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I've used Dyna bolts before and was quite surprised that
only the last centimeter of the bolt expands to grip the
sides of the hole. Probably because for that section to
fail the rest of the hole would have to fail too. |
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Ever since I always wanted to make an expanding bolt for
use as a
universal fastener. something that could work on any
hole with a few standard sizes. these were the ideas I
considered. |
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The first design I thought might work was a thin metal
strip coiled around a tapered threaded bolt. both sides
of the sheet would be textured so as to provide more grip
for bolt bolt and hole threads. The interior sheet end
would be cut at an extreme angle so as to provide a
sloped inner hole. As the tapered bolt was screwed in the
sleeve would expand and grip the sides of the hole. This
design would allow about 1/3 expansion from original
diameter as long as length did not become a restriction |
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My second design called for a metal strip which would be
attached to a nut at one end and a non threaded
grippable end plate end plate at the other. The metal
strip would be wound like those paper towel and toilet
paper rolls except the side of the strip would be cut at an
angle so that when pushed together they would slide over
one another. One inserts a bolt of the correct size into
the sleeve and then inserts the bolt and sleeve assembly
into the hole with the materials to be fastened in
between. one then tightend the bolt while still gripping
andpreventing the turning of the end piece. this pulls and
twists the nut at the end of the sleeve pulling it towards
the end plate. this in turn forces the coiled strip to twist
around itself and expand the sleeve. The advantage here
is that it could use a standard bolt with an expanding
sleeve rather than have an entire specialized bolt
assembly. |
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the design I propose here replaces the coiled strip with
conical steel washers. |
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PS:What is the protocol when you submit an already
baked(here on half bakery) idea? Do you add your
material to the other page and delete the one you
started? What about comments? Is there an accepted
protocol? |
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//What [Custard] said. But the conical washers could be designed to be more easily "spreadable".// |
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yeah, just use split washers. |
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Hey [RichardT] - not sure what country you're from, but here in Australia dyna bolts are sold by Ramset. Ramset issue a specifiers resource book which provides information on the different anchors available including dynabolts - their load capacities in different materials, failure modes etc. You might be surprised when you see the failure mode of a dyna bolt. A whole lot of material needs to come out to pull the bolt. Other companies issue similar for their own brands - it's just the ramset one is really easy to use. They'll usually email you a copy on request. |
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I do a lot of "field engineering" in my role and often find myself needing to specify odd-job designs to facillitate plant maintenance -like fixing lifting/pulling points to concrete walls in odd places, lifting jigs, etc. I use the specifiers book extensively. |
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Coming to the point - I think you'll find that there are commercially available designs that do this job already. Dynaset drop in anchors spring to mind. |
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