Sledding: Newsletter Challenge (02/26/08)

Hey, Ken. Fancy an upgrade !

340 mph - not surpised it's got those wheels at the back, and being so close to the ground must make it feel like 1000. The 'pucker' effect would make seatbelts pointless.

My trike actually started off on two wheels, with foot-controlled outriggers. In fact, the cutout you can see near the nose was for front wheel clearance. (I decided not to close up the cutouts on this proof of concept prototype -- for fun, mainly -- it makes people wonder: what are those for? Aero in this one is not too important, with the "real thing" being larger.)

Two wheels can hardly be beat for aero efficiency. The rear wheel is more-or-less in the wake of the front wheel, whereas on a trike, each wheel creates its own wake. But with computer-controlled or manual outriggers, the transition from very low speed to ordinary driving speeds is still a bit tricky, causing a bit of weaving, if you're not focused on what you are doing. So, given that my vehicle will be driven by people early in the morning before the coffee has kicked in, I decided to go with three wheels. (But still, at some point I'd like to build another enclosed two wheeler -- but not for commercialization.)

My next prototype will look like this:

I've been puzzled over your pic for a while. It's ultra-cool. The picture I posted was something I saw in a magazine recently. The Acabio GTBO. I don't know much about it, but they seem to be into concept behicles, and despite the jaw-dropping performance of some, they have a seemingly serious agenda about fuel efficient transport. It was a very tenouous link to mention it in relation to sleds, but I'd be interested to hear if the topic of vehicles like yours has a home on CR4. Low-profile, economy efficient transport is a very cool topic. In my wonderings I've not seen the appropriate thread. Any pointers ?

Cheers, Kris

Hi Kris:

There have been a couple threads on the Aptera (which is a bit heavier than mine, a lot more expensive, but otherwise similar) but not many others. My guess is that by the time the Automotive X Prize gets into full swing, there will be about 30-40 teams working on very small vehicles (typically three wheel) and a similar number working on larger, four wheeled vehicles.

The way that fuel efficiency is measured on these vehicles can be really bizarre.

The actual energy consumed by a vehicle can be calculated within pretty close limits if you know weight, aero drag coefficient, rolling drag coefficient, etc. So a REAL 100 mpg vehicle (one that you can fill with one gallon of gas and go 100 miles, without any external energy source) ends up being small and light -- their's no magic. But once there are two or more energy sources, marketers find it convenient to ignore as many as they can. (It reminds me of the scene from The Wizard of Oz "Ignore that man behind the curtain." )

This manner of thinking, in which only one source of energy is accounted for, is promoted by a previous CIA director turned ethanol advocate, Jim Woolsey. In his logic, you first make a 50 MPG hybrid mid-sized car. So far so good -- just a slight improvement on a Prius. Then you make it plug-in by adding some more batteries and a charger. Then you rig the test length to use mainly batteries, and almost no gas, and calculate a believable figure, like 90 mpg. Finally, you include only the 15% of E85 that is actually gasoline in your fuel efficiency rating: 600.3 mpg! He introduced this concept in a wall street journal op-ed piece, where he called it a 500 mpg car -- apparently so he could say something like "the 500 mpg is a conservative estimate"

I'll plan to gather up some links to some of the new small vehicles coming out and start a thread soon.

Hi ken,

Thanks for the info and links, I've bookmarked them to read-up on. There's certainly a lot of jiggery-pokery involved in published fuel economy, it's another one for the 'lies, damned lies....' folder. No doubt the manufacturers will get even more inventive as green issues become more important. It would be great to read any new thread you can put together on the topic.

A mathematician named Fred
Loved sliding downhill on a sled
When he learned about μ
He knew just what to do
So now he slides uphill instead.