Bike Trailer

This is a build log for a bicycle camper trailer that I've been working on.

It's only viewable on a large-ish screen, not on phones/tablets. Sorry. (CSS, man!)

Newest entries are at the bottom.

Picked up aluminum bar and brazing supplies. Tried to start building a wood frame and remember that tidying/reorganizing/fixing tools seems to be most of the time for most projects.
A very inauspicious start. Try to cut the first piece of wood, realize the table saw fence isn't locking properly, and spend then next 5 hours trying to un-seize a rusted steel rod in the bowels of the locking mechanism. The memory card of the camera filled up after an hour, so you're saved the excitement of me staring at it!
Initial plan was to braze zinc-plated spacers on to the bottom of the aluminum bar which was going to be a cross axle. Didn't work at all, and apparently you're not supposed to braze or weld galvanized things because they'll poison you. Oops.

Glued and screwed together a simple frame of 2x2s, it's 7' by 3' which I think is a reasonable size. Just regular SPF that was sitting in the garage, and I checked the weight for that at 7.5lbs. I have been wondering if an aluminum frame would be lighter/stronger, but simple pine seems pretty good maybe?

Also put down some old sheets of 1" XPS to try to get an idea of how much it flexes with support at various points. I'm not sure though -- not laminated with canvas yet of course, and not a full 3' span either. I also won't be standing up in a 4' tall trailer. I think I'll probably have to go 2" on the floor just in case, and hopefully can skim on adding extra cross supports to the trailer frame.

Various attempts at figuring out a roof rack to transport 4x8 sheets of foam on top of the Model Y's rack. Eventually I realized I could use the clamps from the Thule roof box, then it was just a matter of screwing some angles onto the sides and tapering the bottom of the 2x4 to match the curve of the roof rails as they go to the side of the car.
Lamination testing, for more details see Foam Sandwich.
Getting sheets of foam from the not-nearest Home Depot because the Vancouver one doesn't carry 4x8, only 2x8. This seemed pretty good until I left the parking lot and the gap between the foam sheets acted like the world's largest wind instrument reed. As soon as I drove above 18 km/h, it sounded like an obscenely loud oboe. So I drove home at 16 km/h and tried to find the smallest road and alley route home.
Very light (2.6 oz) fibreglass arrived for a tensile strength test.
Using BigPrint thinking that I'd be able to match my very fancy bezier teardrop curve if I printed out the shape at 1:1 and pieced it all together. After a lot of futzing around, I couldn't get it accurate enough across 6 sheets by 8 sheets so I bailed and redesigned the roof curve to only need straight lines or circles of known radius so I could draw them with a nail and a piece of string.
However, the BigPrint wasn't for nothing -- the full size test did tell me that I probably needed to increase the length by a few inches, otherwise my target very-comfy air mattress wasn't going to fit.
Time to start measuring curves and cutting out the profile. Just traced it on with a sharpie and then jigsaw to cut it out, followed by sanding. Only one side was drawn/cut. Cutting through a double sheet would have been asking for trouble, so after cutting out one side, I traced that on to the other side and cut it separately.
Then line both sides up with each other and try to sand them to be as close as possible. I have no idea at this point if the curve is plausible to bend the roof over.
Cutting the straight parts works better with a long sharp Olfa blade and a straight edge. Now on to trimming the two pieces that are going to be sandwiched together to make the bottom. The top one is an inch smaller all around so that the walls and roof have somewhere to register when they're added. Fraser enjoyed smashing and snapping little off-cuts.

Off camera I Gorilla Glue'd two 1" sheets together with a 1" 'dado' for the walls and roof to fit into (meaning the top sheet is inset by an inch so there's somewhere to butt the walls against).

I checked that double sheet on my temporary trailer frame and actually it's surprisingly almost stiff enough, even without any lamination. I had been thinking I'd need a fancy aluminum frame, but I think the bits of 2x2 that I pieced together might actually be enough, along with a metal axle.

I made the frame before I was sure about the length of main base, so I have to disassemble and shorten by 2". Mostly a lot of shuffling things around because there's not enough space to work on large pieces. And then I did a bad job of re-assembling it because I didn't have an easy place to clamp so that was kind of dumb.

I figured I might as well go for the first layer of kraft paper. I unrolled a 3' x 7' piece and was pleased that it would cover the whole width so I wetted it down off to the side, changed into "painting-clothes" and started spreading Titebond II.

When I went to grab the paper to put it on, it became very apparent that (surprisingly!) a 3'x7' sheet of thin wet paper rips very easily. So I tossed one and tried about 3' x 3.5'. That ripped again, but I sort of got it in place and smoothed it down. And then repeated for the other half.

I think in future about 3' x 2' will be the max I work with. This ended up "OK", but but it ripped in a few places which makes the top layer of glue hard to spread. I think with a little sanding it won't be too bad though.

Gluing the inaugural layer of kraft paper to the inside floor. Roughed it up with sandpaper, sprayed a 3x7 sheet of kraft paper to wet it, spread a layer of Titebond II with a roller. Tried to pick up a huge soggy piece of paper and move it across the garage to lay on top, predictable it ripped all over. So I tried again with about half the size which still ripped but I was worried about the glue drying so I just used it anyway (this was probably a mistake, it takes a really long time to dry, and the rip/joins are quite visible. Oh well. Anyway, probably about 2'x2' is the maximum size to work with, otherwise the paper just loses too much structure.
While that's drying, working on making an axle. I have push-button release wheels from a child trailer that I want to reuse, but don't want to destroy the trailer, so I need to figure out how to make a receiver for those. The push-button axles require a receiver that has an I.D. of exactly 1/2", and has to be about 1.9" long. It can't be too long or the ball bearing at the end won't be able to stop it from slipping out, it can't be too large in diameter for the same reason. It also can't be too short otherwise the wheel would be sloppy and slide in and out of the receiver.

After various other ideas I settled for now on a 1/2" to 5/8" steel spacer (that is, I.D. is 1/2", O.D. is 5/8"). That part fits the wheel axle quite well, but I'm not sure how to mount it. It's also not quite the right length (about 1.5" long), so I need to 1) mount it to the trailer, and 2) adjust the length a bit. For #2, I settled for now on a nylon bushing (3/8"?) that makes it a snug fit. That pretty much fixes the length, though sacrifices a bit of axle support.

To mount it, my current plan is to put the steel spacer into some 1/2" ABS (I.D. of that doesn't really match, so I ended up using a torch to burn/melt it, and then smash it in). Then, take the ABS pipe+spacer combination and smash that into a 1" aluminum square tube, which... also doesn't really fit. One end worked better than the other, but in the end with various "encouragements" I got them both in, and they seem to work OK. I Gorilla Glue'd the first one because I was worried about it moving later, but that was a big mess and very tight, so I didn't do the second one. The second one went in differently, and shaved part of the ABS rather than squishing it, so wasn't as snug, unfortunately. So... I might be rebuilding the axle eventually, but it's probably fine for now. But I'm also not sure how much weight the the 1"x1"x.096" aluminum square tube is going to hold, so something else might fail long before the receivers do. (Possibly just epoxy the receiver onto the tube, and then a pipe clamp for extra support?)

In any case, once I figure out exactly where the door of the trailer will be, I'll know where the wheel needs to be so I can bolt the aluminum tube on through the wooden frame at the right spot.

Around this time I realized that because it was made out of kraft paper, that the name of this trailer would be the "Kraftwerk Pocket Campulator" and I would be the "Operator with my Pocket Campulator". So now this project has to be seen to completion to fulfill this joke. If you aren't either German, or kinda old, and have no idea what that's about, see Pocket Calculator.
First lamination (inside floor). I didn't think I did a very good job, but because it shrinks as it dries it helps flatten and smooth. Seems like it's improved stiffness quite a bit, so I think one layer on the insides is probably enough.
New torture device that can also be used to perforate the foam before gluing. The idea is that there's more surface area, almost like little nails holding the glue/paper into the foam. I'm not sure how well it'll work, but it's less messy than roughing it up by using sandpaper, and having some sort of roughing of the surface seems like a good idea, as it's otherwise very slick and smooth.
Marking and then cutting out the door on the driver side wall.

Cutting out the main door on the "driver" side.

I wasn't sure if I should cut the door before or after putting the kraft paper on. Doing it before reduces the strength of the panel quite a bit, and makes the paper more of a pain to put on, but if I cut it out later I was worried that while cutting I'd delaminate. It seems quite strong when it's on, but still relatively easy to tear off the surface.

The two tricky parts were cutting a 45 degree angle on the bottom (so that water would have somewhere to run out if any gets in), and the curves around the top. I wouldn't say I did a great job of these, but hopefully with some sanding, kraft on top, and paint it'll be OK.

Then I used a new thingy (not affiliate link) which is supposed to be for installing carpet (?) but I used it to puncture the surface a bit. The idea is that the glue will have more surface area and grip better (to reduce that peel-off-ability).

Finally, I dithered trying to decide if I needed to reinforce the door frame, and which parts, and how. I decided to just reinforce on the hinge side so that a couple door hinges will have somewhere to attach, and I'm going to try some metal/paper drywall corner along the bottom later to reinforce the beveled edge.

Bevel on the bottom edge of the door so that if any water comes in there it drains outwards not inwards.
Adding a support piece of wood to the hinge side of the door frame and for the hinges to screw into later. I maybe should have sunk this into the foam.
Kraft-laminated the inside driver wall, with a variety of patchwork sheets of paper.

This is applying a layer of Titebond II and kraft paper to the inside of the "driver" side wall.

Possibly pre-cutting the door was a mistake as going around the hole is pretty annoying. I didn't actually cut out the window that's also supposed to be on this side but it would have been extra annoying if I had, I think. (Or maybe since it's smaller it wouldn't have been too bad, I could have just gone right over it and trimmed later.)

Also, going over the door reinforcement wood there was a bit fiddly and ripped the paper in a few places when trying to go up and over the edge. Maybe I should have sunk it in, but I didn't really want to remove any foam thickness, and I was kind of feeling lazy.

The basic formula is wet the paper, put on a layer of glue, spread and smooth the paper, add a layer of glue on top and spread it all out. I'm still not too sure about the amount of water to wet down with, nor the amount of glue to put before or after. I think I probably need to 1) give the water a bit longer to soak but also "dry" a bit, and 2) use less on the bottom layer of glue as a lot of it seems to end up on the ground squeezed out when I smooth the paper on to it. The top layer can have more or less an arbitrary amount as it just has to sit and dry for longer if you put too much (within reason).

A whole lot of glue dripping out from smoothing the paper onto the first layer of glue. I should probably use less for the first layer work it in more from the top on the second layer.
Trimming the driver side wall once it's dry. Around ridges and bends I need to be more careful as at the top of the door here there wasn't much glue and it didn't adhere so I had to go back to fill that and now wait another day. I also definitely used too much glue around that half where it was dripping off, so I'll need to get a better feel for the amount needed to coat fully but not splosh everywhere.
Door peek.
Chipping off all the extra glue from the last lamination. Yuck, need to watch that spill out.
And, lamination of the inside of the other wall.

Laminating the inside "passenger" side wall. I'm still not sure about the amount of glue to use, but I think this was closer. I've used almost 3/4 of a gallon for a single layer on the floor, and both inside walls, so ... I'm going to need quite a lot at this rate. We'll see how secondary coats go, perhaps a little less glue required.

The first sheet of paper was too big, and so went on a bit "wrinkly". It works better to smooth with your hand than trying to use the knife or trowel to do it.

But I didn't learn from the first one, and I also screwed up the second sheet.

I think keep unrolling the 3' wide paper thinking "oh, that's not too big" and cutting off a 4' length because it fits nicely on the wall panel. But then trying to pick up a soggy 3'x4' piece of paper doesn't go well at all. It's just heavy enough that you can't really slide it on the glue that's already down after you place it, and it's also heavy enough to rip itself when you try to lift it up to adjust. So aiming for ~2x3 sheets now. There will be more seams but I think they'll be sandable, or maybe not that noticeable at all anyway. 2x3 is easy to lay on more or less accurately on a first try, and much easier to adjust too.

Getting cooler in the evenings (below 10C) and the glue takes 48h+ to dry now. I thought maybe I would be able to move inside, but I realized the 36" frame is too wide to fit through a standard 32" door, oops. I can probably only work on the door and shelves inside.
I've apparently moved into the "hack it together" phase (and stop bothering to go to the hardware store to get more fasteners), so after a bit of hunting around the garage I found these not-exactly-suited brackets and a worm gear clamp to hold the axle onto the frame. I put the floor onto the frame and lay down on it. And despite it being only janky 2x2s, foam, and a single layer of paper glued onto one side, it actually feels very solid and possibly even overbuilt. Hopefully that strength will translate into solid-enough walls and roof.

I started by trimming the extra of the passenger inside wall, and then tried to add a bit of extra glue, a bit on a corner that wasn't quite laminated, and then also one spot where there was a bubble. Not sure that it helped with the bubble so that might need to be cut out and patched later.

Once that was dry, I started trying to figure out how I was going to mount the axle to the frame. Held up the wall to get a good idea of where the door opening would be so that it won't collide when it's opened, and then cut a couple cross pieces, one for farther back where the axle will attach, and one for where you'll sit down through the door for a bit of extra support.

Then, pondered how to attach it for a while. Originally my plan was to put some bolts through the axle (1" square aluminum tube), but it turned out that the bolts I happened to have were about 0.5" too short. I was going to go pick some up, but later I thought maybe it wasn't going to be that great to have a bunch of 5/16" bolts through the not-that-strong aluminum tubing. I happened to have a couple angle brackets and heavier fasteners so I decided to go with those, as well as using a single pipe clamp (worm gear clamp?) that I had that was the right size. My thinking was that most of the force is pushing the axle up into the frame (?) so, uh, it'll be fine. I'm pretty sure I'm going to keep the trailer and frame/axle relatively de-couple-able, so there's always the option of building a different frame if this one seems too janky.

Not sure about the drawbar yet, but thought about that for a while too. I think I'll be able to cannibalize a bit more of the kids' trailer (where I got the push-button wheels) just by unbolting some of its pieces (i.e. without destroying the that trailer.)

Also tried a test fit of the floor onto the frame, and the whole thing actually seems fairly solid so far, especially given the partial construction and the building materials!

Disassembled the old kids trailer and made some matching holes in the aluminum tubing to be used up the length of the body.

Working on the drawbar to attach to the bike. Start by disassembling the donor trailer, and try to figure out how we're going to attach it to the frame.

I realized because it has two of the grey parts to attach its frame to the curved part that attaches to the bike, we can actually use the "off" side, but upside down. That way the old kids trailer will still remain usable as a cargo trailer just by swapping the wheels over still.

I took the frame outside to try attaching to the bike, very fortunately with the frame bar attached only with clamps. I was mostly only testing to see if it was the right offset from the middle, but as it happened I had put it on the wrong side (the cog/derailleur side of the bike), because of course the trailer was upside down! So that was a lucky break.

After a test run, found another metal tie thing lying around, and then went to get some carriage bolts to bolt the drawbar into place. I don't think it qualifies as bulletproof, but solid enough. I weighed it just after the camera died, and the total frame is just under 20 lbs, so I think the whole trailer should able to come in under 50 lbs unloaded.

Realize that I clamped it on the wrong side (fortunately only clamped, not bolted!) and then take it for a quick test ride with a co-pilot. I really need to get some sort of a tripod that's better than "balance awkwardly on workbench".
Get things properly bolted down for real (on the correct side this time).

Prop up the walls on the frame and floor to confirm it all fits. The unplanned door reinforcement that I added at the last minute while gluing the inside butts out, so either it or the floor will have to be trimmed where they meet.

I'm not quite sure how I'm going to actually assemble the walls at this point. I think I'll have to make a shelf at the back, and some sort of support structure at the top and maybe front so that there's some supports to clamp and rest them against.

Testing to see how the router works in foam. It's pretty easy, other than spraying pink (though actually not as bad as I expected).
Test piece seems to work OK.
So bite the bullet and hit the real wall pieces. I measured and fiddled for quite a while because I was nervous about having to remake these walls. It seems to fit pretty well and I think it'll help quite a bit with stability and glue up as well. I'm not sure if the shelf will even need extra support or not once it's laminated.

I definitely need some cross pieces to have any chance of gluing the walls to the floor. I'd been planning on a shelf above feet so making it "structural" to help hold the walls, at least during gluing seemed like it would work.

I tried a simple piece that was the width of the floor first, but that was going to be hard to use (though the glue would have held it fine I think), but then decided I'd cut out a shallow groove in the walls for the shelf to fit into.

So most of this is me remembering how to use a router (you don't need to do it too "right" when routing foam, it's like it's not even there so you can go any direction and it won't pull, etc.) and then trying to figure out how to clamp a routing guide (without any long-mouthed clamps) to try to cut the groove straight.

I moved the camera for the second wall, so there's a closeup of one side. It's not very obvious in the video, but it does spray quite a lot of pink "sawdust" everywhere.

It seemed to work pretty well overall so far. I'll probably need to also do something similar at the front and somewhere along the top. Not sure yet I can do something in those spots that can be functional and structural. Perhaps some extra support on the front wall for leaning up against to make that wall more durable.

Glued up the lamination for one side the shelf and the inside of the door, with assistance.

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