Good idea about moving the engine, that should be very good for ride quality. If you can't spare the room behind the driver you could have the engine hanging off the back of the chassis in the same position, then have a wider swingarm reach around it.
16hp may be enough to get around town, but you can be sure people will be asking about sportbike I4s and EV powertrains pretty soon...
Yes, mounting engine to chassis would be ideal but it will create a new problems with chains and gearbox. We want to keep it light and simple. With the swing arm being 40 inches long and engine and gearbox mounted all the way forward behind the driver with upspring up and down motion of 4 inches all the way on the other end by the rear wheel. It will be about 1 - 1 1/2 inch up and down motion on the engine side if you hit a larger bump.
Rear swingarm bushings next
I'd rock it if it's dirt cheap. The Harbor Freight micrometer makes me nervous though. 
In reply to sethmeister4:
Caliper, just sayin'.
In reply to ValuePack:
Correct, my bad.
In reply to sethmeister4:
I've used mine for years with no ill effects. Cost $15. Most calipers are only supposed to be good to .01 inch and 0.1mm (1 less decimal place than displayed).
Cardboard? Yes, we are doing cardboard stencils for 6061-T6 aluminum panels that will be cut and riveted to the frame for extra strength. The strong foundation of our lightweight frame combined with our aluminum chassis panels bonded and riveted to perimeter frame tubing represents just one of the major design and functional differences between the Go3wheeler and almost every other car out there.
interesting build - but a suggestion. Don't make your posts sound like ads. Seriously, "aluminum panels riveted to perimeter frame tubing" describes a 50 year old Lotus Seven, not a breakthrough in engineering. Let the car speak for itself, don't try to talk down to a well-educated audience.
Did I read 4" of rear suspension travel? Seems fairly minimal. I'd try to get more than that.
Hard to say exact what suspension travel would be in 450 pound car. We definitely have way more than 4 inches of travel right now. Will get exact measurement when we get some real miles on the car.
I love the project, but like Keith said, try writing this more as a build log and less as an advertisement. You'll get along great here if you do that, this is our kind of madness!
Agreed
That frame design is dire.
Suggestion 1: Make the front hoop from one piece of continuous tube. That way it won't berkeleying collapse when the car goes over.
Suggestion 2: Add a pair of diagonal braces from the top of the front suspension box to the bends or corners of the front hoop. This will get rid of the hinge you've made in front of the "roll hoop".
Suggestion 3: Change that rectangular diagonal box that you've got running down the front of the car to a triangle that runs from the center of the front hoop to the front top of the front suspension box. Right now, it might be able to help a little bit with bending but it could do so much more to avoid local deflection at your pickup points.
Suggestion 4: Consider where your seat belts are going and what the loads on each attachment point are going to be. Hint: a 200 lb man in a big crash exerts a forward force of about four tons. There is absolutely nowhere on that frame that could handle the load right now.
Suggestion 5: Add a rear roll hoop. In addition to helping you avoid decapitating the driver when (not if) the thing goes over, it will also serve as an obvious location to weld everything to. The crossbar behind the seats with the two verticals going to it is just plain awful - any vertical load will bend the crossbar in half, any lateral load will shove the verticals out the sides. Make the verticals connect to the side rails instead, or get rid of them by incorporating them into your rear roll hoop.
Suggestion 6: Put the pedals behind the front suspension box. That way, the driver's shins don't get broken over bumps (the whole thing would probably fold up like a shopping cart in a crash).
Suggestion 7: Widen or extend the front suspension box to accommodate the shocktowers. That way the spring/damper unit isn't just bending the frame attachment like a leaf spring right there.
Suggestion 8: Let me draw your attention to the tubes extending from the lower part of the front suspension box. You've got a tube running straight forward and back, a tube coming in at an angle, and then, what, exactly? Draw a free-body diagram of this joint. Tell me what you need to add there.
Suggestion 9: Calculate the combination of lateral and forward acceleration needed to overturn the car, then look at your seating position again. See suggestions 1 and 5.
I do not think this car shows either competent engineering or a good fabricator's sense of what's right and not. It is worse than 90% of the frames in FIRST robots built by high school students, and those aren't manned. Good tube frames are found at any short track open-wheeler, any SAE Formula or Baja competition, or in any tube-and-rag airplane.
Please don't endanger your brave test pilot with this frame. It was useful for welding practice and deciding on the general locations of your components, but it's not suitable for road or track.
In response to chaparral HalfDork. I think you missed the whole 450 pound concept we are after. Any one can build a 3000 pound car with a price of $20.000 but don't see anything done around $3000 with 450 weight. Please understand that I don't want to bash your writing. Looks like you put a lot of work in to it and we appreciate this but don't get me wrong it sounds like you want to build a rock crawler or a race car. This is not a track car or 3000 pound monster. 6061-T6 riveted aluminum panels going to add extra strength in all directions without added weight. A roll bar will be welded as well as seatbelt brackets and few other braces as needed. The fiberglass shell will be bolted to the chassis. This vehicle is a three wheel car or considered by all 50 states as a motorcycle but will be a lot safer.
The challenge is in building a 450 lb car intelligently. Those suggestions won't increase the weight to 3000 lbs or affect the cost dramatically. They're engineering. And even $3000, 450 lb cars need engineering - especially if they're being sold.
Go3wheeler front aluminum section. 
go3wheeler wrote: This vehicle is a three wheel car or considered by all 50 states as a motorcycle but will be a lot safer.
Will you have data to back up that stement?
Link to Three wheeler on Wikipedia
http://en.wikipedia.org/wiki/Three-wheeler
I'll start be saying that I love the concept of what you are trying to do. I am a fan of three-wheelers. I come from the land of the T-Rex and Can-am Spyder, so I guess I am biased.
If this is something that you are doing for yourself, than I encourage you to keep at it.
But if you seriously intend on selling this machine for around 3000$, than you really need to do your homework.
First off, unless things have changed a lot in the last three years, a three-wheeler is not automatically considered a motorcycle in all 50 states. For example, some states won't consider it a motorcycle if you are sitting inside of it (as opposed to on top of it), or if it has a structure above the driver.
That brings me to the second point. This looks in no way safer than a motorcycle. The lack of any higher front crash structure means that if it ever crashed into a high riding vehicle, the rider's head will be taken clean off. Also, correct me if I'm wrong, but your CG looks way too rearward for stability. There is a reason why most successful three-wheeler (like the Norton shrike, the T-Rex, etc.) have the feet of the rider in front of the front axle line.
And that brings me to the last point. The engineering doesn't seem worthy of a 3000$ asking price. A cheap industrial air-cooled engine hooked-up to a kart clutch is not a great place to start for a vehicle. Especially if you want fuel efficiency. And definitely not worthy of a 3K vehicle. If you are serious, check into the chinese ATV engines. Like this. Just as powerful, more fuel efficient, more compact, lighter, integrated transmission with reverse, easy parts sourcing, and reliable-ish. I won't go into the structure, and suspension.
Like I said, if this is something you are building for yourself, keep at it and have fun.
fanfoy wrote: And that brings me to the last point. The engineering doesn't seem worthy of a 3000$ asking price. A cheap industrial air-cooled engine hooked-up to a kart clutch is not a great place to start for a vehicle. Especially if you want fuel efficiency. And definitely not worthy of a 3K vehicle. If you are serious, check into the chinese ATV engines. Like this. Just as powerful, more fuel efficient, more compact, lighter, integrated transmission with reverse, easy parts sourcing, and reliable-ish. I won't go into the structure, and suspension.
Ooh that Shineray engine looks cool. Wish it made more than 16HP though..
go3wheeler wrote: Go3wheeler front aluminum section.
And what's reinforcing the Z'd sections on the front? The front end would be a LOT stronger, and not significantly more expensive or heavier, if it were triangulated. As it is, you've got an 8 sided shape. Not good for structural integrity unless you're intentionally designing a crumple zone, and it's in the wrong place for that. I had assumed the picture of the frame was not a completed frame and that you were planning on adding more cross-braces, gussets, capping open ends, and the like before you put a skin on it.
The aluminum skin adds some rigidity, but it would be a lot better if the skin were wrapped over a stronger frame.
If you're driving a tiny 3 wheeler in traffic, you will need to assume that most drivers will not see you, just like a motorcycle. I know you said you aren't trying to build a race car, but given the risks of running something like that in traffic - you should be designing this as if you are.
Not trying to be a jackass here, just want to point out that the frame design needs some improvements before I'd be willing to take something on the road.
go3wheeler wrote: Link to Three wheeler on Wikipedia http://en.wikipedia.org/wiki/Three-wheeler
Your back-up data is a wikipedia link? 
go3wheeler wrote: In response to chaparral HalfDork. I think you missed the whole 450 pound concept we are after. Any one can build a 3000 pound car with a price of $20.000 but don't see anything done around $3000 with 450 weight. Please understand that I don't want to bash your writing. Looks like you put a lot of work in to it and we appreciate this but don't get me wrong it sounds like you want to build a rock crawler or a race car. This is not a track car or 3000 pound monster. 6061-T6 riveted aluminum panels going to add extra strength in all directions without added weight. A roll bar will be welded as well as seatbelt brackets and few other braces as needed. The fiberglass shell will be bolted to the chassis. This vehicle is a three wheel car or considered by all 50 states as a motorcycle but will be a lot safer.
1) I didn't miss the "450 lb concept". 450 lbs is VERY heavy for a single-cylinder, no-aero, tube-frame car, especially without the weight of a fourth wheel, differential, and drive axles. Any modern tube-and-rag single-cylinder FSAE car is under 400 lbs. The $3000 part is slightly more difficult, but none of my suggestions would've added more than $50 to the cost of the car.
2) "6061-T6 riveted aluminum panels going to add extra strength in all directions without added weight" - Bull-E36 M3. First, 6061-T6 panels add weight - they have mass. Second, riveted joints have a startling amount of compliance unless the right rivets are chosen and the joint is designed well.
3) Why do you need a fiberglass shell? Wouldn't some nylon over the frame tubes do the same thing?
4) Your seatbelt brackets HAVE TO ATTACH TO SOMETHING. I don't care if your seatbelt brackets themselves can take a 5-ton load, if 1/2 ton is enough to yank the tube it's attached to out of your frame.
5) Call the WPI Baja or UNH FSAE team and ask them to give you a design review, and maybe pay one of their students by the hour for design and analysis.
Let's take a look closer look at our design and very popular Scoot Coupe http://www.ebay.com/itm/100-Street-Legal-Scoot-Coupe-3-Wheel-Trike-Scooter-/231063851433?_trksid=p2054897.l4275
Specifications: Scoot coupe x - Go 3 wheeler
•Displacement: - 147.5 cc x - 420 cc
•Max Power: - 9.28 hp @7000 rpm x - 16 hp @ 3600 rpm
•Cooling System: - Air Cooled x - Air Cooled
•Engine Type: - 4 Stroke x - 4 Stroke
•Cylinders: - 1 x - 1
•Starting System: - Electric x - Electric
•Transmission: - CVT Automatic - no reverse x - CVT Automatic - with reverse
•Brakes: - Dual Piston Hydraulic Disc Anti-Lock x - Dual Piston Hydraulic Disc Anti-Lock
•Parking Brake: - mechanical cable x - mechanical cable
•Fuel Tank Capacity: - 1 gallons x - 1.75 gallons
•Fuel Grade: - 87 Octane x - 87 Octane
•Steering: - Rack & Pinion x - Rack & Pinion
•Front Wheel Bearings: - Internal Hub x - Internal Hub
•Mirrors: - Dual Side Mount w/ Turn Signal x - Dual Side Mount w/ Turn Signal
•Rear Turn Signal: - LED w/ integrated brake ligh x - LED w/ integrated brake ligh
•Interior: room - up to 6' 3 comfortably x - up to 6' 6 comfortably
•Dimensions: - 56W x 96L x 50H x - 62W x 115L x 52H
•Roll Bars: -stainless steel- chrome finish x - 2 inch black finish
• Frame -16 Gauge1X1 square tube frame x - 11 Gage 1 1/2 square tube with riveted aluminum
•Price - $7.500 x - $3000 kit $4500 completed
go3wheeler wrote: Link to Three wheeler on Wikipedia http://en.wikipedia.org/wiki/Three-wheeler
I'm pretty open-minded about this, and admit it is fairly cool in its idea. However, I think buyers will need more than a wikipedia article and a generalization about trikes being safer than bikes in order to want to buy-in to this project. Keep in mind, your average driver thinks the smart car is super unsafe and the bigger the SUV, the safer. Looking at this three-wheeler, untrained eyes will think it's unsafe. You'll need to combat this idea if you're going to sell it to commuters as opposed to those who might be racing it or using it for hobby purposes. But also, you need to be sure you're building and selling something that is exceptionally safe.
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