ball-bearingwood
I have a fairly small ball bearing and am wanting to secure the inner ring to a wooden frame. The inner ring has a diameter of 5mm, although I'm unsure the best way to secure this. I could glue a small dowel to the frame and then perhaps lightly hammer the bearing onto the dowel, but I'm not sure if this is the best way. Perhaps somebody knows of a more reliable method?
Toenailing through the baluster on the uphill side with a finishing nail gun should be quite sufficient. The plowed channel holds them laterally. If you wanted extra strength, you could add glue just before nailing.
16 or 18 gauge nails about 1 inch to 1 1/4 long should suffice. The hole will likely be nearly invisible.
Additionally, plowed railings usually come with a filler strip that is angle cut to sit between the balusters after they are attached. If you use the nailing gun (and glue if you wish) to attach those as well, they would further lock in the baluster.
In an attempt to answer some of the questions raised in your posting let me respond in answer format.
1) It can be advantageous in some situations to affix a timber post to the brick or concrete posts/walls in either side of the gate opening. This post can then serve as a better medium into which to attach hinges and latches.
2) A 3.8 meter wide gate will develop a huge amount of lever arm out at the latch end of the gate and this needs to be taken into account when developing the gate design.
3) The size of wood used can play a big part in how heavy the gate will end up being. The type of wood can play a role as well. This is one reason that boards are often used for gate facing instead of thicker planks. Cedar wood is also much lighter than hard wood like oak and thus becomes a popular choice for gates.
4) Adding appropriate bracing into the design of the gate will keep the gate from sagging.
5) Successful wide gates can often benefit from making the aforementioned side posts much higher than the gate opening and then using a cable from the top down to the end of the gate away from the hinges to help support the weight of the gate. Sometimes you can see the tops of the two higher posts connected across by a horizontal member. This provides support from post to post to keep the weight of the gates from pulling the posts to the sides.
Best Answer
Since wood glues tend to be stronger than wood itself in my experience anyway, gluing the dowel to the board sounds like a solid plan to me with one exception...
I'd suggest reversing the order. Secure the dowel in the bearing first, since that step will put more potential strain on both parts. Particularly if the dowel breaks, you don't want it to be permanently affixed to the board when it does.
Compared to the force necessary to wedge the dowel into the bearing, the insertion into a hole in the board with glue in it will be trivial amounts of pressure.