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Learning how to build Lotus Seven replicas...together!
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PostPosted: April 29, 2014, 8:54 am 
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Joined: July 28, 2009, 8:17 am
Posts: 115
Location: Lincoln, NE
viewtopic.php?f=15&t=15005


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PostPosted: April 29, 2014, 9:11 am 
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Joined: November 12, 2008, 6:29 am
Posts: 3567
Lonnie-S wrote:

Do you know what adhesive they use or how it is applied?


Just use "Elcheapo" 5 minute AB 2 part epoxy.


Bent Wrench wrote:
Another aspect of a self tapping screw fastener is that in shear there is a lot of slop.

When a rivet is installed it swells and fills the hole to a press fit.


You are using the wrong self tappers then. Self tappers force their way in with an interference fit and force the material away from the head that acts as a one way gate - they won't fall out. Rivets have a higher safety margin for aircraft is all, being bone shaped they won't fall out if work loose, doesn't really apply to our lot.

Course thread for soft aluminium up to fine thread for tough steels.

Personally I think rivets are far easier - access withstanding of course.


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PostPosted: April 29, 2014, 10:17 am 
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Joined: October 24, 2008, 2:13 pm
Posts: 5326
Location: Carlsbad, California, USA
DM8761 wrote:
http://www.locostusa.com/forums/viewtopic.php?f=15&t=15005


The above is the friction drilling thread. I was very impressed by the technology and investigated it after reading the thread. I had a great conversation with an engineer from a company down in Texas that makes equipment to perform friction drilling on a number of materials with hand-held and gang mounted drills. These drills are fairly large and not your typical hand-held, consumer-level units with plastic bodies.

It turns out that to get reliable results the drills need an electronic controller that gets to a certain speed quickly, holds it for a specific period of time to penetrate and then slows down to form the threads. The controller does get feedback from the drill itself. The controller has to know which particular fastener type you're installing and into which material it is drilling. The Texas company uses fasteners from a German firm and their controllers are programmed for those from the factory, otherwise you need to develop your own programming. He told me they experimented with techniques to do it without a controller, but the failure rate is unacceptable. Failure in his context doesn't mean you don't get a hole with threads, it means the result does not reliably meet engineering requirements and specifications, so is not commercially viable as a manufacturing process.

The all-up price for a basic drill and controller was in the $15,000 to $20,000 range, I believe. The fasteners were also expensive, but I don't recall what they cost. It's a fantastic idea, but not for a Locost build IMHO, at least not at this time.

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


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