my second bike trailer, still not finished

I'm starting this page in the summer of 2026, when I'm not finished with this second trailer yet, but I'll show the progress.  This trailer is for much bigger, heavier loads than the first one which is described here.  Pictures and description will probably lag behind, until after this trailer is finished.  It's taking so many months because there are portions where I have to just look at it and think for a long time, and get friends' suggestions, to figure out the next step.

Why wood?  Because it's easier to cut and join than metal, if you don't have special tools.  Even a serious woodworker would have thousands of dollars' worth of equipment; but I'm not serious enough to spend that kind of money, and what I have are common hand tools, plus a Dremel, a hand drill, a drill stand to hold the hand drill like a drill press, a jig saw, a sander, a vice, a miter box for a manual saw, and not much else.  Actually, carbon fiber would be best; but again, I have no tools or know-how to make anything with carbon fiber.  Howard Hughes made his famous H-4 Hercules flying-boat transport plane out of wood, the largest seaplane ever made; so it can't be all bad.  (The critics called it the "Spruce Goose;" but it was mostly birch, not spruce.)  A video showing the size is here.  A man could walk, standing up, inside a wing.  It was intended to be a transatlantic transport plane for WWII, but the war was over before the plane was completed.

Why four wheels?  It's to give the load a smoother ride.  It's like making each bump half as tall.  Having the front and rear of each side press against each other on the same spring means the trailer frame design was a little simpler in terms of handling the forces, particularly without putting the springs inboard of the wheels which would reduce the inside width.  With better planning, I could have shortened the wheelbase by at least an inch, and the length of the wheel wells by 2"-3".

Why such small wheels?  I wanted the top deck as low as I could get it, so that strapping a big, heavy load on it, roll would still be minimal.  I also wanted the top to be like a flatbed truck, where the load can be wider than the bed, without wheels sticking up and interfering on the sides.  The wheels had to stay entirely underneath, even with full spring compression on bumps.  If I had planned better and not changed my mind about a couple of things, the top could have been another inch lower.

Why solid tires?  This trailer is for the rarer need to carry things that are too big or heavy for the first trailer.  Pneumatic tires definitely have their attractions; but since this trailer won't be needed very often, pneumatic tires would need to be pumped up every time I use it, and that's four tires, and pneumatic ones this small (8") don't leave room to get common pumps on the valves, a problem I ran into with our grandkids' first tiny bikes.  I would also have to carry another size of inner tube for fixing flats, and fixing also becomes problematic.  Solid tires avoid these problems, and these wheels are supposed to be able to carry 1100 pound each!

Here's the suspension assembly, a variation on the "walking beam" theme:

It will take several hundred pounds to fully compress the springs of both sides at once; so if I limit the load to 150 pounds (that might be gross weight), there's still plenty of room left for absorbing bumps.  The heaviest parts of the trailer are those wheels (rated for 1100 pounds each!), bolts, hinges, and huge washers, not the wood.  The dowels the springs fit over are black because they have paraffin and graphite on them for lube.

The following were taken in the process of making the suspension assembly:

The screws are 1/4"x20tpi machine screws, tightly clamping the wood between the hinges.  Again the black stuff is paraffin wax and graphite, for dry lube.

The springs, which go over 1" dowels to keep them centered, push against 2½" flat washers with 1" holes, which a neighbor welded to sections of pipe that a machinist friend notched for me, and then the neighbor applied Cerakote to:

Here's part of the trailer showing the suspension installed:

and after some more progress:

(Yeah, I should have stained the outer wood to match the rest!)  The wheel well's inside vertical surface is 1/4" plywood, and so is this fancy-cut outside vertical surface, and the load is focused down onto the thick wood bar that the wheels' frames attach to via hinges.  The darker panel lying across the top is now installed, as the front vertical wall.

The tongue area is all wood, with lots of triangles for stiffness and strength, something I learned from the first trailer that is super important.

The tongue area will also have plywood over the top and bottom when finished.  The hitch joint, able to rotate in all axes, is the same as on the first trailer.

A friend asked about my method for joining the wood pieces.  The first question was about preventing splitting when driving a screw in.  I suppose there's a name for what I've been doing, but I don't know what it is.  It has been working pretty well for me though.  For the square dowels, when I put the dowel on the edge of the first sheet of wood, it's accessible to clamp hard with a C-clamp to prevent splitting; and then drilling is not necessary.  Here you can see marks left from the C-clamps:

This is at the top, and the top deck of the trailer will get screwed down to these, which means the dowels will not be accessible to clamp to prevent splitting; so then yes, I will drill first.  I often like to put the second screw (at 90°, holding the other plywood surface) close to the first one, so each one helps hold the wood together to prevent the other one from splitting it as operational stresses are applied.  I like to make the screws long enough to get all the way through the dowel but not so long they stick out the back.  The size (diameter) of the screw is chosen so it's big enough for strength but not so big that there's a risk of splitting wood.  (There's no way to clamp the sheet of plywood screwed into the square dowel.)  I also don't want the screw or the pre-drilled hole to remove too much of the cross-section of the wood and weaken it.

In the picture above, four dowels are visible, one of them being vertical and visible only at its end.  All of these come flush.  The top deck of the trailer will get screwed down to all of these, bracing them really well to each other.

The next question was about keeping the wood layers together so a gap doesn't form when you drive a screw in.  I clamp the plywood to the dowel with clamps that will not mar the plywood.  This holds things together so they cannot separate as I drive the screw in (which I do with a screwdriver tip on the drill).  If a hole is drilled first, there's less tendency to push the pieces of wood apart.  When I can't get a clamp on it, I just push with my hand, which is probably what I'll do when I screw the top down.  I'll just remove the suspension assembly and lay the big box flat on the concrete garage floor, and push the top down with my weight while I drive a screw in.

In cases where a screw has to go into the plywood a long distance from the edge, it can be too much of a challenge to make it hit the center of the dowel behind it.  In that case, I drill a small hole from the dowel side, to come out through the plywood (easing up when I'm nearly through, to prevent breakouts), so putting the screw in from the plywood side, it will find the middle of the dowel.

Here're some more pictures:

You can see where the tips of the screws come to the surface of the smaller dowel there.  I didn't always hit the middle perfectly, but they'll do just fine for the most part.

Somehow I failed to get the smaller dowel flush on this one:

In a few places, I've done this:

For this one, I had to bend the L-bracket sideways a little bit in the vise since I needed an angle.  These two screws are machine screws, and they push through the holes in the wood and clamp it tightly with a nut.  I use flat washers there on the wood, with no lockwashers, and use blue LocTite thread locker so they cannot loosen on their own.  The square dowel there is 1", and the screw on the right goes into a 1x2 on the other side of the plywood, the 1x2's thinner edge being against the plywood.  This is in the tongue area.

I'm closing in on the finish line.  I have the top deck cut out, but I need to figure out how to make the door in it that goes between the wheel wells and runs most of the length of the trailer, and I want the whole top to be relatively flat.  The door needs to be strong to support a heavy load on top.  I will probably use lift-off hinges again, so the door can be quickly removed when I don't want it on there, and it should have some way to keep it from bouncing open on bumps if there's no load strapped down on top to hold it closed.  The frame of the top deck is 1/4" plywood (but I might add small joists for strength), and comes around the tongue area as all one piece, to add stiffness.  It will be screwed down to the square dowels that outline the tops of the vertical walls.

Pardon the poor quality of my cheap $30 Vivitar S126 pocket camera.  I don't use a cell phone, the #1 reason being that cell phones are the prime surveillance device!



posted Jul 12, 2026, page last updated Jul 21, 2026             contact:  Garth Wilson, wilsonminesBdslextremeBcom (replacing the B's with @ and .) (southern California)  No SEO spam!