eta: super efficient 3 wheeled car (project thread)

[eta]

Yes, basically all the kits or plans I see are not oriented towards economy, even the 3 wheeled cars. The few that are very efficient tend to be much more complex than necessary, like the new XR-3 hybrid from rqriley.com. Dave Norton's Shrike is an example of sporty first and mileage second, but I contacted him because he is a very experienced mechanical engineer and because he welded up a space frame out of tubing. He dislikes fiberglass as I do. Look at the Vortex, the frame is thick plywood covered with fiberglass, much too heavy! I think I can do this fairly simply if I cannibalize a Geo Metro and use as many of the pieces as possible. For example I intend to use the OEM front McPherson struts because they are simple, cheap and have quite low unsprung weight. Even with 3 wheels I can still just copy the original geometry. Most people would design and fabricate double "A" arm suspension, but I'm not sure all that work would be worth it. The original Metro had plenty of performance for me, I just want a car that feels snappier around town and gets even better fuel economy.

The Bridgestone RE 92 tires got a lousy rating in the "TireRack.com" review, very few people would buy them again. The Tire Rack's technical article on LRR tires and fuel economy is very interesting. When driving in stop and go traffic around town, overcoming inertia is far more important (35%) to mileage than air resistance (5%); I am focused on light weight for now, which is why I don't like electric or hybrid. Better aerodynamics will follow, after I get a vehicle to really take down the highway.

[eta]

Does anybody have any experience with the lightweight battery made by Braille? It is called the Braille "No Weight" Racing battery, but would it work OK for the street as well? It is tiny, only about 7" X 4" X 6", and weighs only 15 pounds! But it still puts out 425 cold cranking amps. As best as I can tell, it is not high tech, just lead acid but it uses a different method of construction. It sells for $190 on Jegs.com, not too expensive. Its not deep cycle, and so not for electric cars, although Braille might make other models?

After looking around their website a little more, I realize that TireRack.com may not be the best place to look for LRR tire info. I have always liked their reviews, lots of feedback with a large sample size on different performance characteristics, so you can really compare the tires. But they don't include mileage in their list! And they don't even have Low Rolling Resistance as a tire category.

[SVOboy]

Odysessy also makes some good sealed batteries...but then, depending on the CCAs you need you could just use a lawnmower battery for about 1/8th the price,

[eta]

Well, I researched the Braille "racing" battery and found it is a re-badged and over-priced Deka. Made in Reading, PA, Deka is the leader of the battery industry in power/weight ratio. The one I'm going to buy is the Deka ETX 14, which is normally sold as a motorcycle battery. It weighs only 11.5 lbs, is very small and yet puts out 360 cold cranking amps, enough to start a car with no problem! All this info is from VWVortex.com Some of the VW guys recommend the bigger ETX 20L, at 15 lbs, for starting high compression engines in cold weather. The OEM VW battery, by the way, weighs about 35 pounds. So the good news is that a Deka battery like the ETX 14 sells for about $60 (from bigcrank.com), instead of $170 for the identical battery that has "Braille Racing" stickers on it!

"Bigcrank" claims this battery can be discharged completely without damage, and so they call it a "deep cycle" battery. Doesn't "deep cycle" really mean it is better at delivering long-term small amp loads, like powering an electric car? So if this battery can indeed be used in plug-in electric and hybrid cars, why isn't everyone using it? It would save hundreds of pounds, take up less space, and still be cheap.

[AndrewJ]

Originally Posted by eta

Doesn't "deep cycle" really mean it is better at delivering long-term small amp loads, like powering an electric car? So if this battery can indeed be used in plug-in electric and hybrid cars, why isn't everyone using it?

In short, everyone would be using it if it really was impervious to 100% DOD (depth of discharge) cycles.
It seems to be just your run-of-the-mill sealed lead motorcycle battery. Basically it WILL be harmed by running it to below about 60% DOD, it just won't be AS harmed as a normal battery.
These types of batteries typically don't have the capacity to be used in EVs or hybrids. While they are certainly light compared to a normal car battery, they have a correspondingly lower capacity (EV's measure battery capacity in amp-hours, typically how many amps can be discharged for 20 hours)
Sealed lead batteries, wether they are valve-regulated, gel, or absorbed-glass-mat (AGM) have even lower capacities than traditional "Flooded" lead-acid batteries.

[MetroMPG]

Originally Posted by eta

After looking around their website a little more, I realize that TireRack.com may not be the best place to look for LRR tire info.

That may be. All I can tell you is the Insight drivers who are really into fuel economy really seem to like the RE91's. They're also probably more willing than the average person (ie. TireRack reviewers) to give up handling/grip for better efficiency.

[MetroMPG]

Based solely on aesthetics, my hands-down absolute favourite 3 wheeler I've ever seen is this one:

Absolutely stunning. And it's an EV (dragster) to boot, so it really is efficient too.

More pics, tech specs: http://www.evalbum.com/416

[paulwelkins]

Here's my attempt at the three wheeler idea. A little different than what you have planned.
www.highmileagetrikes.blogspot.com
You'll also see some other interesting things on the site as well.
You're on the right track, rather than building from scratch like I did. automotive engines and front wheel drive are the way to go. For a glance at ultra light, look up Jory Squibb in google image search. I was just about ready to try something like his 3 wheeler, but am currently obsessed with converting my crx into HM vehicle. Jory gets 100 mph, I'm almost half way there, and I can go on the freeway in comfort and incogneeto!

[paulwelkins]

Oops! I ment Jory gets 100 mpg

[Coyote X]

The problem with using the metro front struts is that they would force the height of the front body to basically be the same as where a metro hood sits at stock. This was the biggest thing that kept me from seriously starting the triumph spitfire xfi project I originally thought of doing.

When you look at a metro the struts are like a 1/2 inch away from the hood stock. The shortest struts I have found that would fit would only lower it another inch. Adding a solid rod and pivot would let you remove the struts and replace them with a coil over setup but it would be really complicated and hard to make reliable.

I would recommend narrowing the front end by shortening the axle shafts as much as possible and trying to just keep the weight as low as possible to keep it stable. Having a wider front area to push through the wind would make it more stable turning, but then you are ending up with near the same frontal area as a normal metro would have.