Skateboard Sans Fuel Cells
 

I have never been a big believer in hydrogen fuel cells, but GM's idea for a "skateboard" with the frame, engine, fuel, steering, suspension, exhaust, etc. packed into it and being very short so that it could be shared among many models of car struck me as very practical (minus drive by wire for the foreseeable future, though). Their idea was to get mass production up to lower costs, but I think the modularity would be the real advantage. It would lower the barriers to entry to both the body and engine markets and allow greater consumer choice, with a larger selection of engine size, transmission, or even how many driven wheels there are. It also means a vehicle could be upgraded in stages spreading out the cost. The modularity could be great for maintenance: if you had a breakdown, they give you a rebuilt skateboard and you go on your way. Same thing for preventative maintenance: just swap it out at regular intervals. Need a few different sizes I suppose.

I wonder what sorts of skateboard theft this might lead to? :p

I've never been impressed with the idea precisely because of the body-on-skateboard design. Everything you do body and interior-wise has to be above that board, which means the interior floor is going to be 12-18" off the ground at the lowest. That's fine and dandy if you like the SUV look and feel, but I prefer cars with a low center of gravity.
If they want modular vehicles, they should modularize major components and use common mount points for all of them, leaving the body and relatively inexpensive interconnecting bits open for model specific designs.

Since a lot of weight would be in the skateboard, the center of gravity should be very low. Keeping the skateboard thin is the biggest obstacle I see as well, although there are flat engine options. I think I heard once that GM's eventual goal was 8" high (disclaimer: my memory may be in err). How tall are frames now, out of curiosity?

Thinking a bit about standardized mounting points and power transmission seems the biggest trouble, given the variety of arrangements. I guess minimum clearances could be specified to enable different options. If you didn't obey some of them, it just rules those options out. Be easy to make a program to keep track of such conflicts. I'll think more about it. Not as modular as the skateboard, but a hell of a lot better than what we have now. It also more neatly addresses three wheeled vehicles. I guess making everything quickly swappable is another issue. Maybe a blend of the two approaches, with a convexity requirement, rather than a flatness one, so the body can still be lifted vertically off?

Eh... The body and interior components are far from weightless. The window glass alone will weigh a few hundred pounds, and only the roof is further up on the body.

That depends how you define a frame. My CRX is a unibody design, so the body is the frame. In the engine compartment, the frame rail is about 4"x8". Under the passenger compartment, the rail drops down to maybe 3"x1"... The door sill is bigger, really.
If you look at the few vehicles that still use body-on-frame design, such as trucks, you may find those 8" tall frame members down the full length of the vehicle. Unfortunately, you won't find such vehicles with a low CG.

The interface of a the skateboard with crumpling is something I've wondered about too. Need to learn more about crash safety mechanisms. This is great food for thought. I checked my car and it's extremely thin under the driver's spot.

Don't know if anybody heard about it, but government funding for fuel cell vehicles was slashed recently. It's what got me thinking about all this.

I always thought cars should be more modular, but a skateboard don't seem ideal. I was thinking more like an engine/trans module that could plug into a series of cars like a socket. If something happened to the engine/trans it could be swapped out quickly. Having a spare module would be ideal(maybe even a dealer loaner), just drop it off at the mechanic to plug into their test socket for trouble shooting or rebuilding.

Then converting from diesel, gasoline, fuel cell, etc. would just be plug and play, along with a modular fuel system. Or you could put a Ford engine in your Fiat-Chrysler minivan. :D

Front wheel drive vs rear wheel drive vs four wheel drive, etc. makes all this stuff tricky. Modularity is definitely a worthy goal, though. I've been successfully soured on the pure skateboard concept, so now I want to try and come up with something else.

Why even bother to pick the old one back up? Just keep the replacement when you get a failure. They rebuild it and give it to someone else. I can see why car companies wouldn't like this, that's for sure!

Why's that? You're replacing 2/3 of the car... I'm sure the price would reflect that.

Lower barriers to entry means a lot more competition on the components. Repair costs should also be a lot less too.