How do I join 2x4s without mitering? [solved]
I asked this question on the Bicycles site:
DIY wooden bike rack — looking for plans
I'm planning to build this rack out of 2x4 pieces of wood. It'll live in my garage. I'm looking to make a rack similar to one of these, but simpler and, obviously, not made of metal:
(My question is, how can I join 2x4s so they'll be strong, particularly the ones that are horizontal? The stand won't support the weight of the bikes, but it will keep them upright. (Several of my bikes don't have kickstands.) I'd like to avoid mitering the joins, to make construction simpler, since I don't have a miter box. (We have a circ saw and a regular wood saw.)
I know you mentioned that you want to build the bike rack out of wood (and 2x4s) but...
You could probably build nearly that exact bike rack out of PVC pipe or even a slightly simpler design: 
http://www.utahmountainbiking.com/goodies/TruckbedBikeRack.htm
Go to your local big box store (Home Depot / Lowes / etc) and look into joist hanging / decking hardware, such as these.
I wouldn't use miter joints for a project like this anyway -- they're mainly for appearance, not strength. Unless you want it to look pretty I'd stick with lap-type joints, where the pieces overlap each other. Then you can just screw them together with deck screws, or for even more strength you can glue them too. If you want to enhance the appearance you can create an official lap joint like this: 
The advantage being that your boards end up in the same plane and look a bit less klugey. You could make these either with your hand saw (tedious), or by making several half-depth cuts with your circular saw and removing the remaining material with a chisel.
Where you need to butt a 2x4 up against the flat of another, this won't work. The best joint to use in this case would be a dado:
You can make these with your circular saw and chisel too. With some glue and a couple of screws through the long piece into the end of the butted piece, this makes for a very strong, nice-looking joint.
You don't have to worry about joining 2x4s so they will be strong. I made the simplest possible bike rack by butting them together and nailing them. It's not at all sophisticated but it is easy to build and strong enough to do the job.
I happened to have some scrap lumber, consisting of two 6-foot boards and many 30-inch pieces. The two 6-foot boards are the top and bottom of the bike rack. The bottom of the bike rack sits on the ground. The 30-inch pieces are nailed vertically between the top and the bottom boards, forming slots into which your bike tires sit. I spaced the vertical pieces according to the varying widths of various bikes' tires.
The bike rack can stand alone, but it becomes much more stable when at least one bike is inserted into each side of the rack. The vertical boards keep the bikes from falling over. There's enough friction that, on the floor of my garage, the bikes don't roll away on their own.
Here is a picture of the rack when it is fully-populated:
Miter joints are simply not strong enough here to support the loads they will see. And glue won't be strong enough either to keep the miters together. End-grain to end-grain does not make for a strong glue joint.
I've used hand cut mortice and tenon joinery on 2x4 construction before. Yes, it was overkill, but it was fun to do. :) It does yield a strong joint, one that you will trust. It is not even that difficult to do, since the 2x4s are soft wood to cut even with a handsaw and chisel. For even more assurance, after the joints are assembled, drill a hole through the joint, and insert a dowel through it to prevent the tenon from pulling out.
Based on your sketch in the link, I would just nail or screw them together. It would more than suffice.
I would suggest using a top and bottom rail of 4 * 2 and make the uprights from large diameter dowel (think broom handle). This should be more than strong enough for your needs and much lighter.
10 Best Butt Joint Methods | Woodworking Tips & Tricks
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