I wanted lightweight wheels for my backpack/travelpack as I was going to be spending a lot of time on train stations.
Nothing seemed to meet my idea of something easy to stow as well as being easy to install and remove.

These wheels are easy to make, and can be quickly added or removed when required. The eyelet bolts are permanently fixed but are small enough not to get caught up when not in use.

Step 1: Materials Part1

Begin with a pair of small wheels (these are 75mm in diameter and have bearings), light weight rod 200mm wider than base of backpack for the axle (I used donated stainless steel rod from a lighting shop - check the wheels will fit), a packet of small R Clips, and a small length of tubing to use as a spacer on the axle.
You will also need Eyebolts - see step 4

Step 2: Axle

Drill a small hole about 5mm from one end of the rod. This can be tricky so be patient to avoid marking the steel rod. Don't cut the rod yet.

Step 3: Testing the Axle

Place the wheel on the rod and hold in place with the R Clip.

Step 4: Materials Part 2

You will need two eyebolts which hold the axle neatly, and you will also need extra (locking) nuts and washers.

Step 5: Fixing the Axle

Take time to investigate the best position for the wheels. For my backpack this was the point where sides, base and back met. The axle is clear of any weight other than the wheels and the location is forward as far as possible so that nothing drags on the ground when tilted for rolling.
With a strong sharp object eg a medium sized knitting needle (you can start with a small skewer), make a hole in the bag, put a washer on the eyebolt and poke the bolt end of the eyebolt through - this might take a bit of work but try to manage it without making a cut in the bag.
You might also want to trim the ends of the eyebolt on the inside - I'm still undecided about this.
On the inside of the bag thread the washer(s) and nuts.
Do the same on the other corner.

Step 6: Final Assembly

Now thread one wheel and a spacer onto the axle, thread the axle through the eyebolts and put a spacer and wheel on the other end.
Adjust the spacers so the wheels spin without hitting the backpack and rotate freely when it is loaded.
Mark the end of the axle - remember to allow for the R Clip - cut to length and drill a hole for remaining R Clip.

Assemble or dismantle in seconds by removing just one R Clip - ideal for train stations and airports.

Cost (plus donated rod) = $12