Building a car from scratch- how would YOU do it?

[theunchosen]

I'd do something like the Atom.

Make the whole thing out of Fiberglass instead of aluminum, since its a monocoque anyway add a little aero.

Toyota 4 AG-E Silvertop supercharged.

Or Honda H22a supercharged.

Since its FG monocoque sub 1 kip is possible.

I'm actually doing this with an aluminum rail frame and CF skeleton with FG shell for the seats. Like pod seats so no flooring and using a 4AG-e silvertop that I was able to acquire for very cheap along with all the drive train and electrical systems.

. . .For fun it will be supercharged lol, but I'll have it also able to kick lean mode with water injection with the blower on and see what kind of FE I can rake(Lean mode will be done with WOT and variable resistance between the MAP and the ECU, while the water injection will be switched on separately before initiating the WOT and resistor).

[JacobAziza]

Something similar to the tango in shape (passengers front to back, so its thin enough to park like a motorcycle Commuter Cars - The TANGO, ultra-narrow electric car for commuting; 0-60 in 4 seconds) but with a 250-500cc (bio)diesel engine and 6 spd manual transmission.
Might have to be slightly wider than the tango because it wouldn't have the heavy battery pack to give it stability.
I'd keep both electronics and amenities to a minimum both to save cost and fuel demands (no power anything). On something so small and light, power assist steering and brakes would be unnecessary anyway. Also, that way it would be cheaper/easier to maintain (and mod )
Essentially a fully enclosed 4 wheel motorcycle with a diesel engine.
Because the 70mpg I get on my ninja doesn't seem worth it during the winter rains.

[rkcarguy]

Originally Posted by theunchosen

I'd do something like the Atom.

Make the whole thing out of Fiberglass instead of aluminum, since its a monocoque anyway add a little aero.

Toyota 4 AG-E Silvertop supercharged.

Or Honda H22a supercharged.

Since its FG monocoque sub 1 kip is possible.

I'm actually doing this with an aluminum rail frame and CF skeleton with FG shell for the seats. Like pod seats so no flooring and using a 4AG-e silvertop that I was able to acquire for very cheap along with all the drive train and electrical systems.

. . .For fun it will be supercharged lol, but I'll have it also able to kick lean mode with water injection with the blower on and see what kind of FE I can rake(Lean mode will be done with WOT and variable resistance between the MAP and the ECU, while the water injection will be switched on separately before initiating the WOT and resistor).

4AGE silver top is a good engine, I'm assuming your talking about the 20V japanese version?
Only downside is the iron block, but with the supercharger it's probably the right choice.
I think the unibody is the only way to go due to the better utilization of interior space. Plus, many tube frame cars are way overbuilt. People underestimate the strength of materials and don't realize it's the shape that makes a car strong not 1/4" thick wall tubing.

[theunchosen]

Originally Posted by rkcarguy

4AGE silver top is a good engine, I'm assuming your talking about the 20V japanese version?
Only downside is the iron block, but with the supercharger it's probably the right choice.
I think the unibody is the only way to go due to the better utilization of interior space. Plus, many tube frame cars are way overbuilt. People underestimate the strength of materials and don't realize it's the shape that makes a car strong not 1/4" thick wall tubing.

Yeah I've got one lined up complete driveline and electronics for a grand plus shipping, but I'm also shipping it with several other engines(shop) so I get a hefty break on that.

I haven't really extensively worked with composites yet so I'm thinking two routes. The first is buy some fiberglass and work with it to get it down pat(CF is 60 bucks for 4 square yards and I would prefer to screw up on cheap(20 for 4 square yards) materials than expensive ones) and then build it out of CF.

The other route, which is slowly picking up favor with me, would be build the load bearing portions out of CF and as much as I can everything else out of FG. Engine mounts and rear bits would have to be CF to maintain the engine's weight along with some of the passenger weight and fuel tank, but I think I can do seats out of FG(its much lighter and cheaper), body panels and any storage compartments. With this approach I'm thinking something like a twin chassis. One chassis runs front to back with most of its strength rear biased (the CF chassis) and one that sleeves over(and bolts into) the rear chassis and provides most of the strength for the front suspension and the passengers.

I'm concerned about weight distribution going with composites though. It's going to have a 400ish lb block of metal 50% of passenger weight and probably the fuel tank sitting on the rears and no weight to speak of sitting up front. I'm considering putting the tank up front but I'm not sure. . .suggestions?

For aero its going to be a wedge entirely focused on downforce. It will be more aero than no body paneling(by a long shot) but I'm concerned about being low weight and not having grip on the front tires at highway speeds. I'm expecting the engine and trans weighs at most 600(I might be wrong on that rk I haven't weighed one) 50lb gas tank, 50 lb battery, 100-200 lb chassis, 40 lb body, so right in around 1/2 ton at 70 mph with probably 80-20 rear-front weight distribution.

[MechEngVT]

The Ariel Atom isn't a monocoque; it's a steel space frame. With the steel frame it's a stock 40/60 weight bias.

Of course nothing's saying you couldn't build a car in the same idiom using a CF monocoque but it would necessarily be a quite different car than the steel chassis Atom. If you are concerned about taking too much weight off the front I don't think it would be too difficult to move the front suspension mounting points rearward. Pictures of the Atom appear to place the front wheels ahead of the driver's feed while many race vehicles place the front wheels between the driver's knees and feet. It may require rearranging the pushrods/bellcranks to move the shocks/springs forward to maintain foot clearance.

[theunchosen]

I had considered that but I honestly can't say its going to help a whole lot without slanting the entire chassis to "lean" on the front. If its flat(and easy) the engine weight is going to literally be distributed strictly over the rears.

I'm thinking of moving the front wheels back as you suggested(it might make the steering assembly more tactile than having it extend as far) and putting the fuel tank at the front instead of sitting in or around the engine. It would also keep the height down so that the rear of the vehicle is the height of the engine mounted to the wheels and only as wide. I am also slightly concerned that if something went cataclysmically wrong the fuel tank is not a 60 lb bomb mounted to the engine. IF the fuel spills on the hot engine thre is a decent chance of ignition whereas if it dumps out front its alot less likely.

[evolutionmovement]

You might want to think about getting a fuel cell with a bladder. It's the only thing I'd put in a vehicle I'd build. Burning alive or, even worse, surviving horrible burns scares the hell out of me.

[theunchosen]

Originally Posted by evolutionmovement

You might want to think about getting a fuel cell with a bladder. It's the only thing I'd put in a vehicle I'd build. Burning alive or, even worse, surviving horrible burns scares the hell out of me.

Thanks Evo,

I was thinking take a regular 10-12 gallon tank and then put it inside a CF box under the FG body also separated from the "cab" by FG. So you get 3 layers.

I'm also considering a CO2 dump system. I've got a half dozen 20 oz CO2 cylinders. The idea would be an emergency extinguisher by suffocating the fire. I tested it on a small gas fire in my driveway and the 20 oz bottle with its dump valve pinned put out the flame rather quickly.

Since the engine will be in a semi-enclosed bay(open underneath and at the front for the air intake) I think 3 tanks purging would be sufficient to put out anything going on there(It would actually be a central case with all canisters enclosed and lines running to the bay and the gas tank). I'm fairly certain the 3 nozzles in the bay is overkill since 1 of them is enough to put a fire out in an open area, but when it comes to being burned alive. . .

Any other input? I'm very new to car design so any input is welcome.

Oh and yeah I am aware the Atom is tubed but I am aiming for a potentially lighterweight counterpart with better aero. Anything that doesn't have to support weight will be single or dual ply fiberglass not sheet aluminum.

[rkcarguy]

I agree and I have drawn my designs with the fuel tank up front. My design has a large "channel" running between the passengers to the front of the car. Just forward of the front firewall a saddle tank is the way I'm looking to go, or maybe just a 8 gallon fuel cell if it fits in there. Like already stated I did this to keep some weight forward and for safety. Remember that your car will go further and a massive SUV tank isn't going to be required to have 400+ miles of range. The bladder tank is a good idea.
Your about right on with your 4AGE weight, I wanna say around 650#'s on a pallet with the axles wiring and computer(everything needed to make it run).
I generally disagree with the frame and body form of construction. The frame has to be strong enough to withstand the forces applied, while the body also must endure wind forces rocks insects birds etc.
2 years I was on the solar car team(RC 1/10th scale in high school), and our best(strongest and lightest) design by far was a unibody built off of the carbon fiber laminated fiberglass honeycomb we used under the solar panel.

[theunchosen]

Yeah just an update I changed my mind to the monocoque CF. The Fiberglass will be plenty tough as a cloth composite instead of as a fiber reinforced composite(I accidently hit a rabbit at 70 with my fiberglass particle reinforced bumper and it did no damage). This will be much stronger and only slightly heavier than fiber reinforced(regular fiberglass for most applications thefibers are sprayed in and not in any kind of pattern, whereas this has some small strength without the matrix to bind it.)

I know I wouldn't need an "suv" tank to get all the mileage I need. . .but my dad has been considering a road trip to Alaska and I'm feeling two of these. There are a few good stretches of the plotted trip that would have to be altered strictly for fuel(to go out of the way to grab some between destinations). So I was looking to alleviate that problem and be able to drive from one stopping point to the other. I'm hoping with either the charger off, or if I can reliably get the engines to burn lean with no risks then one and lean, to conquer 50 mpg.

I'm not sure if thats a low bench mark or a high one. The 4A-GE was in the Corrolla and they got alright FE and this ought to be at least half a ton lighter than that. The aero is probably going to be very simple geometric pointy nose but I haven't quite decided.

I'm not terribly interested in the body for aero other than avoiding a cd of .5 or anything and am putting alot more time into finding the lightest weight pistons, rods and shafts that can stand being juiced to alot more horsepower(rotational mass in the engine creates much greater drag than weight mass on the frame so if I can shave a few pounds off the rods cylinders and shaft I can shave lots effective weight).

I think if I can get the lean burn to keep from eating the pistons and valves I should be able to compete with an old insight, considering I'll be able to do much higher AFRs and have alot less mass and need less power. . .So a 10 gallon tank(or a 12 like My Del Sol has) would cover 700 miles.