Hinge Pins
 

I was wanting to pin some hinges on one of my planes. I've looked all through TH and can't find anything. What is used to pin hinges in place to help prevent them from pulling out?
Thanks

RE: Hinge Pins
 

You can use a small wooden dowel rod or even a round toothpick. Simply drill a hole through the wood and hinge, push the dowel or toothpick through, apply glue, and trim flush with the outer wood.

Ken

RE: Hinge Pins
 

Thanks Ken!

RE: Hinge Pins
 

I can understand that using a metal pin, cut flush with the airfoil, would provide a great improvement in retention and strength, as many people do.

However I wonder about a mere toothpick?

I can't imaging that a toothpick would add that much more strength over a properly soaked CA bond.

It would be interesting to test this.

RE: Hinge Pins
 

Not many folks pin a CA hinge. It's usually something done to hinges like the flat Dubro hinges. Works very well. I have a special burr I use to do the drilling that is a tight fit for a cut down tooth pick. I drill from the botton through the wood and the hinge and about mid way through the wood on the top so the pin doesn't show. I use a drop of thick CA in the hole then force in the pin. It lamanates the pin into the wood very well. I went back to using Pacer hinge glue and the stuff holds so well I gave up the pins.

RE: Hinge Pins
 

I also use the pacer Hinge glue, stuff holds like crazy. Will not work with CA hinges as it won't wick in. I use it for Robart hinge point, flat hinges. Never had a hinge failure. Now if I could only lengthen the expiration date on my planes I would be a happy camper:):):)

RE: Hinge Pins
 

A bit of speculative nit-picking no offense intended:


With the flat hinged inserts, I find it hard to imagine that the toothpick will do a lot for the bond over the epoxy that you may be using.

In effect the only thing you are adding is a very small segment of somewhat soft wood. Unless that is you are adding multiple toothpicks, e.g. four per hinge at the least.


A single metal pin aids things greatly and contributs to the strength of the entire area.

But I'm still confused as to where any additional strength would come from with a single toothpick?
That is it may help, but I'd imagine only a small amount and maybe not worth the effort.

You may get a better result doing as you do now, drilling a very fine hole, and wicking CA in to harden the surrounding wood, where the Epoxy may not permeate and even leaving the toothpick out of all of this.... as the wood should expand to fill the hole if the hole is fine bored. That would also let the CA seep in more completely.

RE: Hinge Pins
 

The length of the toothpick is so short that you would not be able to break it apart. Just take a round toothpick cut it about 1/4' and see if you can snap it in half. When you add CA to it, it really becomes part of the structure. If it pulls out it is going to take a lot of wood with it. Just my 2c

RE: Hinge Pins
 

Just for fun try installing a hinge, a flat Dubro, in a piece of scrap TE stock and only pin it, just the pin itself, don't even add glue. Get the pin in the hinge center. Now try to pull it out. Then you will see the light. It's only something we used to do as a safety feature on our big planes, it works but nothing is as good as doing a proper hinge job.

RE: Hinge Pins
 

The toothpick pin is VERY strong. Much stronger/harder than the surrounding balsa. CA or wood glue can be used with good results. There isn't that much load anyway and you are only trying to IMPROVE the existing bond and not rely solely on the pin.

RE: Hinge Pins
 

These are not CA hinges. The plane came with the ailerons installed with plastic hinges. Is there any trick to drilling throught the hinge without destroying the aileron?
Thanks for the responses.

RE: Hinge Pins
 

It helps if you can use a drill press and can steady the work piece real well. Use a small bit for a pilot hole first and then drill to final size. The bit doesn't like to drill through the plastic and tends to "walk". I've even drilled a very small pilot hole in the wood, then heated a T-pin and pushed it through the hinge, melting a small pilot hole in it. Sort of like using a center punch. Then drill to final size, apply glue and install toothpick.

RE: Hinge Pins
 

The issue with the pins is that you are relying on the cross grain of the wood in the toothpick. When you combine this with the fact that the hinge material and trailing edge or surface material is sandwiched, then you are actually using the shear strength of the cross grain in the wood, rather than the bending strength. Actually if you used a smaller diameter piece of steel pin, rather than the larger diameter of wood, you might end up ripping the hinge material(using the metal) with less force than it would take with the wood dowl.
Pinning these with bamboo skewers or round toothpicks adds a ton of strength.
Curtis

RE: Hinge Pins
 

The hidden trick with hinge pins isn't the pin. As mentioned, it's fairly easy to pull the TE off with a pin through an unglued hinge. It's usually balsa after all, and if the pin has little diameter it can actually cut it's way out depending on how weak the balsa is.

The same hidden trick is why flat hinges have holes in them.

The holes in the flats and the hole you drill for the insurance pin both provide a sure way to get glue back where it needs to be.

Develop your hinging technique and you'll probably discover how to glue hinges so they won't need the insurance pin. How do you find out how good your hinging technique is? Autopsy your crashes. If you aren't going to rebuild the sucker, try to pull it apart. Like, try to pull you hinges out. If you can't, don't worry about the pins. If you can, then maybe you need to drill that hole for a pin, but try to do a better job getting glue inside that hole than you got in the slot when you assembled it.

I always looked at my crashed planes as good opportunities to see how well I built the suckers to find which of my techniques sucked. Of course, some of them I looked at with a tear in my eye....... :)

RE: Hinge Pins
 

Thanks for all the replys. Lots of good info. The big problem is that the ailerions were already installed. so I don't really know how good of a job they did. I've pulled pretty hard and they seam ok. I just don't really know I guess.