An End To The Silence, A Few Updates, And A New Vehicle

Well, POTW escalated… slowly. I updated regularly all of three times, and then disappeared. In my defense, I’ve been busy. I just completed the fourth and final race of the Power Racing Series in New York, and on top of that, school started again. But more importantly, the races.

We raced at the World Maker Faire in New York City. A few of the regular teams were there along with some new ones. And a very, very special guest, MITERS. Specifically, TinyKart and both of the Chibikarts. Sector67 squeaked by TinyKart for a win in the 15-lap road race, and after the Bluesmobile died, I raced i3′s car to a victory in the 75-minute endurance race.

And there’s one for a college app. Ahem.

A quick note: There has been some confusion about whether or not MITERS was ever really racing. It was my understanding that even though their vehicles were well out of spec, they were still eligible to win in any of the events they entered. Yes, there has been some excessive chest-beating over this whole thing, but I hope no hard feelings. Communications in the power racing series are less than stellar, and it was most of the teams’ understanding that MITERS was competing. We even gave them a medal for the road race. But anyways, the point of PPPRS is fun and absurdity, nothing more (electrical fires excepted). There’s a reason I race in a pink helmet.

But while I was at Maker Faire, I did more than just race MIT. I drove some of their vehicles too. And let me just quickly say, I have never driven anything more amusing than a chibikart. And now I really want to build one. Charles went to great lengths to make chibikart an accessible project, and even wrote a whole book instructable on how to make your own. I’ve read it time and time again, and committed most of it to memory. But there’s one thing gnawing at my wallet me and preventing me from building one right now. The price.

So what to do? I want to build a chibikart, but I can’t really justify spending around $1200 on one. I mean, it’s cute, but not that cute. Time, then, to start cutting corners and build a cheaper chibikart (chipikart, if you will). So let’s look at the most expensive bits first.

Batteries. Chibikart uses two of these. They’re lead-acid replacement bricks, and they’re pretty great. However, they’re probably not $280 great. Add on a charger for another $70, and you have $350 in battery stuff alone. Each battery is 12v, 7Ah, which is the same as the batteries I used on TinyBike. Getting two of those would cost me $36. Plus another $15 for a charger. Granted, they do have less discharge capacity (slightly) and they won’t charge as fast, but for 13% the cost, they’re much more than 13% the performance. I also have some A123 cells lying around that might end up in it, but that’s a project for later. This is supposed to be cheap and repeatable.

Total Savings: $244

Waterjetted Bits. Chibikart’s frame is made of 80/20 extrusion held together with waterjet-cut aluminum. And everything else is waterjetted bits stacked on top of each other. This has the advantage of being easy (just send out the files, get parts, assemble), but the disadvantage of being expensive. About $450 expensive. Most of those bits look like they could be replaced with a combination of stock 80/20 brackets, little machined blocks, and some creative welding. I have the CAD files for chibikart (thanks Charles!), and am working on re-designing all the parts to be machined or made of stock parts. So far it’s looking like material cost will work out to be around $60, but I won’t know for sure until I finish the designs. So I’ll tack that on as a tentative amount.

Total Savings: $634

Aluminum Extrusion. Chibikart’s frame is made of aluminum extrusion. It’s awesome because it’s easy, fast, and very adjustable. The plans specify 1″ square 80/20 extrusion, costing $20/6′. By switching to Misumi 20mm square extrusion, I can cut that to $10/6′. And since I’m re-designing things anyways, 20mm will be close enough to 1″.

Total Savings: $664

So far, that’s about all I have figured out. I’m going to go bury myself in CAD for a while and see what comes out. So far, I’ve cut the cost of a chibikart in half (or so). However, I think I can do better. However, all that extra saving will have to be done in the small things that I’ll be cutting, like some of the nuts and bolts that are no longer necessary. And that will require a completed design. So until then, keep it absurd.

Well, POTW escalated… slowly. I updated regularly all of three times, and then disappeared. In my defense, I’ve been busy. I just completed the fourth and final race of the...