Saturday, November 6, 2010

Gecko Works, Stuff@SG, Pneu Scooter MechE

I'm just about at week 3.14 of my visit to SUTD, where one of my tasks is to help set up an interim interim workshop. The interim campus, with its Pappalardo Lab-sized fabrication facility, won't be open until April. In the mean time, we are in a workshop known as "the shed". No, seriously. Since "the shed" is not a very inspiring workshop name, we've renamed it Gecko Works. (Because the surrounding area has an abundance of geckos. And not the friendly type that try to sell you car insurance. More like the type that jump out of the toilet when you flush it.)

As of last post, Gecko Works was pretty empty. Since then, workbenches and about half of the tools have arrived. A virtual Gecko Tour:

Welcome to the SUTD interim interim shop facility.

 Here is a sample of the workbenches. This one is patiently awaiting welders.

The "What the fuck is all that noise?" table. 

 Cuttin', drillin', tappin'.

Baby arbor press is very cute. Perfect for baby wheels.

At this point, we're just lacking the Heavy Machinery: MIG and TIG welders, benchtop CNC mill and lathe. Odds of it arriving before we leave: slim. Oh well. At least we got the basics laid out. There's also a 3D printer, though it hasn't been moved down from the main SUTD offices yet. Hopefully, this will be more than just a six-month temporary shop. The goal is that it will be a prototype for a "fabrication cell" that can be copy-pasted into the interim and final campus. It's small enough that each team in a project-based class could get their own cell in which to work and store their hardware.

My in-between-other-things task has been to go around the country (it's not that big) looking for good places to buy commonly-needed engineering supplies. For anyone who happens to be in Singapore looking for stuff, here's a running list of places I've found to be convenient and legitimate sources of the types of stuff I typically need: Stuff@SG. My only warning: Do not go to Sim Lim Square.

Don't go here.

Go to Sim Lim Tower:

Go here.

They are not the same thing. Sim Lim Square is like if you took Radio Shack and made it six floors. Six floors of bullshit consumer electronics stores with two electrical supply stores hidden on floors 2 and 6. (If you expand Radio Shack to six floors, these would be analogous to the poorly-stocked bins of resistors.) But if you didn't know that Sim Lim Tower exists right across the street, and is full of real electrical hardware stores, you could easily be fooled into thinking that Sim Lim Square is the right place. Not saying that happened to me......just be warned.

Supply chain in place and tools at the ready, I decided to spend Saturday pretending that I'm a MechE for once instead of working on motor controllers. To make sure I don't revert to EE ways (and to keep the aluminum chips out of it), I moved my controller off of Pneu Scooter and onto the first official SUTD electric vehicle:

Who says electric bikes are dorky?

It's got a 36V, 46-pole (O_o) hub motor that I can use for independently beating the software bugs out of this damn controller, or blowing it up. I'd be happy with either outcome. But more on that in a later post. While I have unFETtered access to Pneu Scooter, it's time to face an old demon: mounting a Razor scooter handlebar rigidly to a custom deck. BWD had serious problems because it had only thin sheet metal flanges for mounting stuff. Even with the equivalent of a two-piece clamp holding the front together, it still makes creaky noises when you step on it and the handlebar never quite returns to the same place when you fold it up. Clearly this experience calls for a degree of overcompensation on Pneu Scooter.


From the 20 feet of 5"x1/4" aluminum I bought, this is what I needed. Ten 4-40 screws into the 0.26" side walls of the u-channel should do the trick. A few more in the front may also come later, depending on how thoroughly I feel like erasing the impending failure-feeling associated with BWD's handlebar mount from my subconscious. Mounting provisions taken care of, I couldn't resist taking it for a quick unpowered spin in the parking lot, so I put the Razor handlebar on with the original wheel:


It looks silly, but it coasts nicely enough. Only the slightest bit of noticeable drag from the motor at normal kick speeds. This is good, because if the controller fails or the battery runs out, it's nice to be able to unplug it and kick your way back home.

The last piece of the puzzle is the front fork. I thought this would be moderately difficult to modify. Not so. The Razor A3 comes with a shock-absorbing hinged front fork, as opposed to the welded solid Razor Spark front fork we used on BWD. This one comes apart with one screw, leaving two nice mounting surfaces for a custom job:

The normal fork fits flush to the inside surface of those flanges. Turns out if I instead fit a custom fork to the outside surfaces, the width is perfect for clearing the 6"x1.25" pneumatic wheels. I whipped up the necessary plate geometries out of some more of my infinite 1/4" bar stock.

It's still missing the spacer that bumps up against the rubber shock absorber. And yes, it is being held together with drill bits. I don't have the proper screws and will have to make a trip to Homely Hardware on Monday so I can finish this off. But aside from that, there are no obstacles remaining in the mechanical path to completion. Which means I'll be back working on software or something soon...

1 comment:

  1. Your lucky you have Gecko! I only see cockroach and play soccer with them until I get bored! Amazing insect. Take some pictures of Gecko. I did take pictures of cockroach eating parts of my subway sandwich :) that is a other story (blog post coming up!)

    BTW That scooter is looking GOOD!