Shortening the kickbike

One of the reasons for buying this particular model was it looked like it could be modified easily.

Previously, I have already removed the wooden deck addition and shortened the handlebars. Now I had something bolder in mind.

I have been thinking of two ideas. One was to remove the "wings" at the side of the deck, possibly reducing some weight.

The other idea was to make the deck shorter, both to reduce a little weight and improve the maneuverability (hopefully). This seemed more interesting, and I was a little worried removing the wings might compromise the strength of the box and make it a little too narrow.

I had suspected the outer case could hold inside a relatively large "inner case", but it turned out the part that goes in is much smaller than I thought.

Sketch, not to scale

There are 4 bolts on top, 4 at the bottom, and then 2 at the sides.

Obviously one of the side bolts had to be gloriously stuck, so I had to waste time in removing it. After ruining the hex, I realized I could file the bolt into a more rectangular shape and use a spanner to turn it.

After some nudging, the block connecting the stem to the chassis falls out. The portion that goes inside is only 27 millimeters deep, and the shape is irregular. It is quite hefty.

The connecting part

I could have taken better photographs, but maybe the opportunity will yet arise.

Then began the process of measuring and deciding how much to cut away. Peeking inside, I could see there's virtually nothing at the front 14cm part of the compartment.

I eventually chose 6cm as a suitable amount. There is a hatch at the bottom of the chassis, and if I cut for example 10cm, the hatch edge would be rather close to the front. The other thing to worry is the 28mm radius cable hole in the side.

The 6cm should be significant, but this also leaves some empty space inside the box.

Not all the space is used up.

I was a little lazy and traced the lines around the box using a vernier caliper adjusted to 6cm.

After that, I started sawing with the hacksaw. This is a boring job and I split it into two sessions for two different days. Together it took more than an hour with some pauses.

I'm not very skilled with the hacksaw, but I managed to do it accurate enough. Patience is key, otherwise it's easy to start doing things too hastily, resulting in a mess.

Removing 6cm from the front...

The case is some sort of aluminum alloy, which is quite soft to cut and drill. 

Only afterwards it occurred to me the process could be generating some fine grain aluminum dust, apart from the stuff I could obviously see.

One thing to look when cutting a profile like this is to have an eye at where the other part of the saw is moving. While focusing on the actual cut, the saw might be stealthily ruining another part of the cut.

The part, cut loose

Compared to sawing, the drilling was quite easy and fast. I took the measures from the original piece, and just transferred these over to the desired positions. 

I used 2mm drill for making pilot holes, then an 8mm for the actual sizes. I used ridiculously low speeds here, probably only a few revolutions per second.

Drilling new holes

The original holes were not perfectly round, especially the side holes are more like very short routing lines. I just hope there isn't a really precise logic behind that, possibly just a result of using an automatic router.

The results

I believe shortening the deck improved the drive-ability of the kickbike. It shouldn't be a huge difference, but I think turning tighter corners is a little less precarious.

The distance between the wheels is now shorter than the Voi, which is something of an accident as I had previously measured the distances incorrectly. It might have been nice if the wheels have the same distance. Well, the subjective experience should be more important than the measures.

But did I get rid of any weight?

Carrying the bulk might be slightly handier because of the smaller dimensions, but it's such a small difference it cannot be really felt as weight difference.

I'm going quantitative

The cut part really was one of the lightest things I could remove, so the effect on that front wasn't that great. The cut aluminum part weighed only ~245 grams. Taken together with the plastics it's a little closer to 370 grams.

To put things into perspective, what things weigh:

The 6cm aluminum alloy part: 244g
The 6cm aluminum alloy part and the plastic parts together: 372g
The plastic parts: 134g
Wallet: 160g
Smartphone: 300g (!)
All the keys in my pockets: 145g
Bike helmet: 323g

The kitchen scale measures fluctuate a few grams so the values are not very accurate.

At least the removed material compensates for wearing the helmet!

It's obvious I could lose more by leaving my phone, wallet and keys home.

Measuring the cut out block against the 244g weight pointed to a material density of 2500kg/m3.

Apparently aluminum alloy density isn't likely to be lower than 2660kg/m3, I might be persuaded to believe my measurements are off. The piece has holes, the scale isn't accurate, and so on.

As a ballpark estimate, the central chassis metal part does not weigh more than 3kg. (The battery and other stuff inside are probably heavier.)

I've yet to measure the weight of the entire kickbike (Probably around 28kg originally) so I'm not sure what kind of percentages the removals represent. Also, taken together with the driver's body weight it means very little in the entire system. 

The next step is to cover the openings. I could even cut some more material and try to fit the indicator lights back the way they were.