eta: super efficient 3 wheeled car (project thread)
 

Hi, I'm new. "eta" is the Greek letter for efficiency; I want to build a very efficient, super lightweight 3 wheeled car. My design: a side by side 2 seater using the Suzuki 3 cylinder 5 spd drive train.

2 powered wheels in front and a single rear wheel, using as many OEM pieces as possible, front struts, brakes, steering, with a fabricated swing arm rear suspension with a coil-over shock. A steel tube space frame with bonded-on ("stressed") honeycomb aluminum body panels.

I want to make a "bare-bones" running prototype first, with minimal body panels and just a lexan windshield, no doors or other windows. Later I intend to add aerodynamic body panels and weather protection, removable "gullwing" doors, etc.

This will legally be a motorcycle, which makes all the government hassles more manageable; it will have a full roll cage and 4 point racing harnesses, helmets will be worn.

I hope to keep the curb weight down near 800 lbs and so it should be fun to drive, have excellent performance with truly outstanding economy. This 3 wheel layout gives fantastic aerodynamics, a perfect teardrop shape, less weight, rolling resistance, etc.

Your first question, will it tip over? A 3 wheeler of this "tadpole" 2F, 1R layout can be just as stable as a good 4 wheeler, if it has a wider front track, low cg, and proper weight distribution. I plan to use the right-side axles from the 4 cylinder manual trans Suzuki on both sides, as they are longer, to increase the front track from 52.3" up to 60-66".

I also want to experiment with propane. It burns cleaner, the equipment is simpler and I can use an 11:1 compression ratio possible with the 100+ octane rating to get very good efficiency. Yes propane doesn't have the energy/gal of gasoline, but it has HIGHER energy/lb.

I hope eventually this will be a universal frame design that can utilize different drive trains such as VW diesel, or electric, or even hydrogen. I have some rough drawings and notes, including a static stability calculation I can post here if there is interest.

At this point I need feed back and a real engineer to help finish the design. I have shown my sketches to Dave Norton, see his Shrike design online. So, any comments about my little project?

How big is the engine? And could you go smaller?

I believe the Suzuki drivetrain he's referring to is the 993cc version from the Geo Metro (& various clones). Could he go smaller? Yes, but that's the smallest most commonly available automobile engine in North America. (Though there's always the motorcycle fleet to pick through for smaller engines...)

I did a quick search for "Shrike", and this is what I found:

Yes, 1 liter Suzuki car engine
 

Yes I like the 1 liter 3 cylinder Suzuki engine. It is very efficient, reliable, cheap, readily available and only weighs 140 lbs! I have had Geo Metros and they get 50 to 60 mpg, and with "eta" I hope to cut the weight of the vehicle in half. I like the idea of using a automotive engine and drive train, as it will be very lightly loaded in this application. It will have plenty of torque, and over-engineered brakes, etc. A motorcycle would be more heavily loaded than it was designed for, might have cooling problems, doesn't have enough electrical output, and most do not have reverse. Dave Norton's Shrike is based on a motorcycle and it goes through tires very rapidly, has clutch problems, and has no reverse gear. I intend to get a Geo Metro donor car for cheap and rebuild the parts I need, I suspect a motorcycle might cost me just as much or more. I also think motorcycles are not tuned for economy, but power.

Sounds the a great project, I can't wait to see what it turns into, :)

Good point, which causes me to suggest you also aim for taller gearing than will come with the 3-cyl motor & original drivetrain.

Those are good points.

It's an interesting idea. All of the 3-wheelers I know of have been built for speed, not fuel economy (like the T-Rex).

Motorcycle engines have crap BSFC compared to larger car engines due to their power to weight ratios. No reverse gear isn't a big deal since we can always just use an electric motor for that, but it still may weigh more than a reverse gear in a manual trans.

Yes higher gearing makes a lot of sense with a car this light. I'm going to research the gearing options on the TeamSwift website. As I remember some Suzuki manual transaxles do have higher (lower numerical ) final drives, I think the 4 cylinder models and the XFI economy 3 cylinder version? And I could also go up to bigger diameter wheels as well. That way I might have the choice of some nice light alloy wheels and high pressure LRR tires, although it is hard to find wheels and tires that are skinny enough! The stock steel wheels are 12" diameter and just 4" wide, with a 145/80 tire, which is plenty for this light little car, it will just be driven mildly. I can just use the OEM wheels and get Yokohama Y372 tires, which are (marginally) available in 145/12 and are a good all season tire. They weigh just 11 pounds, but unfortunately are only rated up to 32 psi. Not very exciting, but adequate. And I'm not ready to run space saver spares. Any suggestions?

The Vortex 3 wheeler: http://www.vortexplans.com/ is based on a motorcycle. Go to Dan Lenox's link off that website for a discussion about building an electric reverse for his Vortex.

The non-GT 4-cyl transaxle has the tallest final drive. It's what I put in my 3-cyl car.

I think most people who know about LRR would instinctively suggest the Bridgestone P165/65R14 RE92’s that were used on the Insight as a great LRR tire.

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.

Braille light weight battery
 

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.

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, :p

cheap light weight battery!
 

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.

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.

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.

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

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!

Oops! I ment Jory gets 100 mpg :)

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.

This is all your work? Wow. Some really interesting things on that page.

Thanks, and I apoligize for the sloppy blog. Looking around my shop made me realize that I've made alot of weird stuff, and I'm tripping over these things! So, decided to show off some of my past projects to whoever is interested. I still have more photos of past projects that I want to scan and post, chech back later. :)

What you're doing is really cool; looks like a lot of fun! :thumbup:

Those are indeed some sweet machines! I'm jealous of your skill to create such things, :)

Thanks for the feed back and interesting info! Paulwelkins, like your design, but mine has to be a 2 seater or my wife won't help me build it! And if it is big enough for two, I'm going to go with the car parts. I love your little bike camper trailer, but why not have your feet sticking out into the bubble instead of your head, don't you have nightmares of being a fish in a tank?
Coyote X, yes the Suzuki struts will stick up in front. On this first prototype I am more concerned with simplifying the building and light weight than with the aerodynamics. This will be a short trip, low speed vehicle that will not even have a body, it will look like a cross between a Lotus Super 7 and a motorcycle. It will have a wide front track for stability because that is everyones first question and biggest concern. At speeds up to about 40 mph, the biggest factor for good economy is overcoming inertia, not air drag. If I can get an engineer interested, then car #2 will have an aerodynamic "kammback" body and maybe double "A" arm front suspension to lower the hood and a narrower front track.

Having your wife involved sounds great. I'm sure these boy toys us guys play with have put a glitch in a lot of relationships. As to why I put my head in the bicycle camper dome? to see the falling stars at night.

I Love My Wife
 

Getting your wife involved is wonderful. My wife actually seems to like traipsing around in muddy boneyards lookin fer stuff. :D

On our second date she helped me change the clutch in my buddy's 1989Toyota Pickup. Then we played a trick on him. I had some old planetary gearsets laying around, so we threw them in the back of his truck.
When he came to get it Barb told him these parts fell out of your tranny, but, everything seems to be werkin :rolleyes: OK. :eek:
He lost his Christianity, but I couldn't keep a straight face.
He and I still joke on that Now.

Well, if you're going to use all the componentry of a Metro, why not stick with all the cabinetry too? Whip out the Sawzall and hack off everything aft of the doors, then fab up a new single-wheel rear.

Advantages: you can lengthen the overall profile to better optimize airflow.

Disadvantages: you need good welding skills.

started to make a four wheeler with back wheels right together last summer but got distracted. with everything gone but the dog house. With the front fenders and windshield gone the frontal area actually looks a lot smaller. with nothin' but pipe frame and seat it sure does accelerate well for a 1.5L D. but the back wheels come off if I really get on the brakes. I need to move the battery to the back.

Ok, my interest is peeked. I would like to hear more as your project goes on.

BTW, that cool tin can that Metro posted -
those look like bicycle wheels. can those hold up very well during everyday car use? just curious - i know it's not intended as a cool every day tin-can.

I have been a big fan of the 3 wheeled , 2 seat configuration for a while now, although I prefer the motorcycle frame grafted to a car front end. I think this would be a great platform for a full time ev or a hybrid with a full time electric motor. The light frame weight would lend itself to a smaller motor and less battery weight.

You folks were comparing material for body panels above, what about foam board sandwiched between fiberglass? Would seem to me to be as light as it gets.

oldschool, that reminds me of another 3 wheel car. it was only a concept car but the pics made it look really sweet.
Peugeot's ultralight 20Cup concept

definitely looks a tad better than mine

but does it have 1500cc diesel engine

Eye catching! I really have a soft spot in my heart for 3-wheelers! Many overseas are never seen in the US, but that appears to be one of many Electrothon racers in the US. :thumbup:

I drove a 1966 Westcoaster 3-wheel mail delivery vehicle for years. It had an 8hp 2 cylinder Onan engine. A similar one is on www.3-wheelers.com -Mine just wore out! But I retained the nickname counters*Trike*.

Today; I stick with EV motors in recumbent trikes - open or aerodynamically closed like my avatar.

countersTrike

I thought they looked a step up from bicycle wheels. Mopeds, perhaps, or very light motorcycle rims. They appear to have hub brakes.

I don't see a "Westcoaster" entry there...can you confirm the name?

Thanks! :thumbup:

I like the shape. How efficient are the closed ones? Can you send more pics?

Possibly 'US Mail'. I got the name from the ID Plaque in it. I do not know where it was made, so maybe the U.K. connection never heard of it! The photo they have is of the vehicle (in blue, I think) with a USPS eagle decal or painting. That blistering 45m.p.h. "mini" mini van was the same size as a Zenn EV. Sure would have been ideal nowadays!

countersTrike

That fiberglass/kevlar is very flexible. It was noisier, but about 3 yards of mylar-foam-mylar and 1/4" art styrafoam helped. I have a little stereo in there; and before I couldn't hear it when moving-now I can!

It is terrific in the wind. Going along [[[[shake]]]] :eek: What did I hit??? Stop and it keeps shaking...OH!

I have about 10 pics: mold/plug, fiirst sanding, gel-coat, second sanding, both sides taped together, donor trike, several in '05, '06, & '07. I will try to export a side view from '05.

countersTrike

countersTrike

so you make a mold and lay down a sandwich and what about the plug does it need to pressed. I have been looking at airfoil shapes to put around a car size vehicle but wonder because these shapes have been designed for airplanes (high speed) Is yours as narrow as possible or derived from equations. It is hard for me to believe a shape good at 300mph would be good at 60mph.