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Building Tips and technical articles. => Building techniques => Topic started by: Chris Gilbert IRL-1638 on November 16, 2007, 12:31:45 PM
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Hi Guys.
I'll be using my first (proper) Aluminum undercart shortly. What's the best way to attach it to the model - 3 or 4 bolts?
Thanks in advance,
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More details please------profile or full fuse, one or two piece gear, etc.
Cheers,
Jim
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Full fuselage, one piece gear.
As the model will be take apart I'll probably use the U/C fixing bolts (some or all) to keep the front of the wing in place.
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On the rare occasions that I have used aluminum gear, I have used three screws to attach it to the fuse.
For a model which I hope to have for a long time, I would use 4-40 socket head screws into 4-40 blind nuts.
Metric size would be about 2.5 or 3 mm, I think.
Cheers,
Jim
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No matter how many bolts you use, don't use steel screws! Use aluminum, brass, or nylon. In a hard landing, you want the bolts to break rather than ripping out the mounting plate!
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Strictly speaking, you are correct, but I do try to speak the "local" dialect.
'T wa nae do if'n naebody cud'n un'rstan' mae
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I rather like the idea of bolting the LG and wing on as a unit, tho I'm even more a fan of two piece wings. There are some who like having the LG come off in a crash, but I've found the LG will do a lot of damage to a lot more parts of the model when it comes off in a belly landing. The wing, fuselage and horizontal tail will all get some damage. I'd prefer that it stay put, but that's just my opinion. H^^ Steve
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I think your right Steve. Maybe if it stays put it will absorb more of the impact as opposed to destroying the rest of the ship ? ? ???. Wishful thinking I guess ??
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I'm putting a Sig Fazer undercart on my new Cosmic Wind. I don't really favor bent wire, for obvious reasons.
I used the three-bolt system, sort of 'cause that's how the thing was drilled as I bought it. Furthermore, I beefed up the installation with some hardwood so the bolts don't take the brunt of the load. Fasteners, as they say, not entirely load-bearing.
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If you can't find any commercial landing gears that suit your needs, you can easily make your own.
Go down to the local road repair depot and ask for an old road sign. They are often replaced when the paint is faded. Many get thrown into a scrap heap.
There are a few different thicknesses used but most are around 3/32 (.093).
It's tough enough to hold up under landing but easily bent to shape with a vise and wooden blocks.
Easily cut with a bandsaw and a medium tooth blade.
Bob Z.
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There are countless grades of aluminum and they don't all work.
You need a grade that can be bent to shape and still have some spring to it. I don't know the grades by number, but some bends like cardboard and the high end stuff is about half the strength of steel.
McMaster Carr offers all grades. Does anybody know for sure what to order. The Sig gear is ASTM B209. I don't know if that's the best, but it's what Sig used.