lml@lancaironline.net Mailing List Archive

I did some quick and dirty measurements of hinge play by clamping one half to a bench and then pushing and pulling the other half. Measuring the overall width across the pin, I came up with roughly 0.027 inches of movement (play) for the Carbinge with stock pin, 0.019 when fitted with the 0.083 VAR pin, and 0.004 for a comparable MS hinge.

I like the concept of the bonded Carbinge on a carbon fuselage, especially for a long hinge such as with the IV MG doors (45”+). Everything expands and contracts at the same rate and otherwise relative movement would add up. The length does limit how tight the pin can fit and still be inserted and removed. I spent a lot of effort to ensure a straight hinge line but even the polished VAR pin doesn’t slide easily. The doors do swing easily and there may be enough variation over the hinge line to take up any free play. Time will tell if it’s hitting on a few points and how long the hinge stays tight. If need be I think I’ll be able to use larger pins or insert new nylon tubing.

I formed circular keeper loops in the end of the pins using ring pliers, also made 90 degree bends in other pieces, so the VAR stainless alloy doesn’t seem brittle. Shown are some spring extenders that I made as well.

For a shorter hinge section I’d want a tighter fit. It does seem MS is the way to go in that case. One consideration: I’ve read that aluminum can corrode quickly if it’s in contact with carbon fiber. The solution is to have an E-glass barrier but there’s no such need with the Carbinge. -Bill Wade

From: John Barrett <jbarrett@carbinge.com>
To: lml@lancaironline.net
Sent: Friday, November 25, 2011 8:11 PM
Subject: [LML] Re: Legacy vibrations resolved

For any production hinges a tolerance is required between diameter of the orifice and diameter of the pin in order to avoid having to reject lots of parts that have too much friction. For this reason, the amount of play in Carbinge vs aluminum is likely to be similar. In either case, you can substitute different size pins in order to diminish the play.

A major and important difference between the two is that with aluminum hinges I don’t think you can avoid corrosive wear of the inside diameter of the hinge over time. Therefore aluminum hinges will always become looser over time and will tend to develop the play being discussed even if during installation the parts are match fit to avoid play.

Carbinge in our tests does not wear over time. The fit at installation should remain the same.

In either case, the pin itself can corrode. This will usually result in the pin being more difficult to remove because of rust deposits on the pin. It is good with Carbinge applications to occasionally remove the pins and clean them with Scotchbrite before re-inserting. Stainless Steel pins can decrease this concern but they tend to be more brittle and can fail due to breakage in some applications.

Regards,
John Barrett

Leading Edge Composites

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