Dave Bowles

[dfbvt]

Neil

The trick with outboard wheels is how the suspension works. The Aptera has elongated 'A' arms, but the rendering above shows something closer to the Edison2. Dave, if you want to have the struts fixed, or if you want them to move up and down with the suspension -- then these are two very different designs.

You are correct Neil; these are two very different designs. What I have shown is not totally to scale but somewhat representative of what the final design will look like. However, it is not anything like the Edison 2 suspension design but more like the traditional A arms but squeezed a lot closer together with the suspension springs and shock absorbers mounted inside just in front of the firewall. This approach will certainly add weight over Aptera's original design but I hope the trade-off will be much less aerodynamic drag. I will not really know how well this will work until I get suspension design models done in Solid Works where I can do extensive stress and motion analysis. I think I can still get the wheel camber changes needed and achieved by the traditional A-frame approach along with an anti-body roll feature that is somewhat unique.

We'll see how it all works out once I get the model ready to do a bunch of analysis studies.

Thanks for the critique.

Dave Bowles

[PatQ562]

Thanks Dave for thoughtful replies. I generally agree with your positions and findings. I have some experience in Solidworks, but my previous attempts to model something along my lines using a 2CV chassis as a "skateboard" just didn't come together appearance wise. I greatly admire the elegant shapes worked out for the early Aptera and later Edison2, and I don't want to be seen in something that looks ugly. One thing I should note is that my "pontoons" are meant to be part of the body, ie, bolsters that project outwards from the actual cabin walls to enclose the wheels, somewhat like that aspect of Neil's "boxfish". This reduces swept surface area compared to detached pants or pontoons, provides side-impact crumple zones, and resolves the inside-wheel turning radius. My criticism of wheel pants is that they always seem a lot bigger than the wheel they house, which somewhat negates the value of the streamlining. Furthermore, they either need room inside for the wheel to travel (even more frontal area) or they move with the wheel (more unsprung weight). I'm trying to conceptualize a "poor man's solution": 1) smaller wheels, 2) that only have to be well streamlined in the straight-ahead position, because that's where they point for 98% of high speed cruising, suggesting 3) a well-smoothed wheel nicely filling the opening it rides in, with a well streamlined fairing surrounding the wheel, like a very streamlined cycle fender, that is small enough to move with the wheel with minimum added weight. Alternatively, said wheels are housed in a well-faired body structure rather than outboard pods, but with much the same approach otherwise.

I would also note that radically smaller wheels, if at all realistic, lend themselves more to true direct drive, as the rpm is higher.

I've said this before, but it seems to me the FIRST decision a designer must make starts with the chassis, suspension, steering and brakes. This is the foundation on which everything else must be built. It would be SO much easier, and SAFER, to use a well-proven, mass-produced vehicle platform on which to construct the streamlined body. This of course also supports a donor registration to ease the legal hurdles for DIY or kit projects. The obvious chassis candidates are the VW, 2CV, or Mini although other suggestions are welcome. The VW platform has the most aftermarket support, and is RWD, but the 2CV has a lot of advantages, being very similar to the "skateboards" that several companies have proposed. The Mini is an incredibly compact and stable package with its small wheels and low stance, but is also rare in this country.

Finally, I don't doubt that popularity and competitive dealers have helped reduce the retail price of the large Warp-9 motor/controller, but if you are entertaining any kind of volume in your program, the inherent cost advantages of more optimally sized machines must come to the fore. AC Propulsion is the gold standard, but Azure, Curtis, and others have more moderate power packs (though not much lighter than AC Propulsion). Also, I have a hard time believing that just having a differential adds 8% loss to the powertrain. If so, most of that is in the bevel reduction gears, some form of which you presumably need anyway (hopefully more efficient). The actual differential doesn't do much in straightahead driving so its losses can't be much, although it adds weight. The eVaro boldly claimed the use of dual direct-drive AC motors, but never QUITE made it to the point of independent validation, leaving the question open whether a larger slower machine is really more efficient than AC Propulsion and Tesla's light, high-rpm, low friction machines.

Anyway, all in the spirit of putting our best ideas out there for banging about.

Pat Q

[dfbvt]

Sheepdog 44

But you have the 4 wheel car issue that Aptera tried to get around. It'll be exponentially harder to get it road certified with all the regulations.

You might have missed the first sentence of my original posting which says that this design is intended to be a the DIY kit car design. So being a kit car and not a production intent car we will not need to go through the horrendous and expensive requirements of having to certify this as a roadworthy car.

This does not mean that I in any way intend to sidestep any crash safety or handling safety issues. It is my intent to follow the best practices of race car design with a tube structure designed to fold away from the passenger compartment while absorbing and/or deflecting energy away from the passenger compartment. I also intend to utilize a composite sandwich body, which will be very stiff and very strong and will help prevent intrusion of other structural parts into the passenger compartment. The design will also have a rugged roll over structure.

In the gull wing doors, I will also will have a strong steel band to help absorb a side impact and also a unique transverse composite/tube wall just behind the front seats. The reason for this is for helping to minimize serious penetration into the passenger compartment in a T-bone impact by another car or by sliding sideways off the road into an immobile object such as a large tree or telephone pole.

While I can't afford to do testing required for a full-blown crash safety program I do take crash safety very seriously for three reasons. The first one of course is I don't want to see anybody get hurt. I'm not that kind of person. Secondly, I'm only here writing this today because for some reason I was allowed to live through a very horrific car accident when I was 19. Of the five of us riding in the car at the time of the accident only four of us lived through it. In fact it was reported that I had not lived through it which quite understandably got my parents quite upset. It took me a year and a half to recover and I have plenty of scars to prove it.

Thirdly, I am a 30 year veteran volunteer firefighter and former fire chief. I joined the volunteer fire service to fight fires. However, as time goes on we seem to be doing less and less firefighting and more and more car accident responses. Believe me, I have seen some horrible stuff including cars that have skidded off the road sideways hitting telephone poles and trees sideways. I have seen cars that have bent to at least 75° angles. In short, I have help zip up too many body bags and so I do take this extremely seriously and will endeavor to do the best job I can to design a safe car.

Incidentally, I have already got a very experienced formula 5 open wheel race car driver to help me get some real track time and some expert test driving ( Man! I really had to twist his arm...). He doesn't know it yet but one of my hockey goalies who is my friends race mechanic will be shanghaied into helping tweak the suspension for good handling. Ahh, the wonders of a hockey league and a few beers.

On a far lighter note the Bebe "Pulse" sure is a cool looking rig and undoubtedly is safer than riding my Harley

Thanks for your critique and ideas.

Dave Bowles

[NeilBlanchard]

Narrower wheel fairings mean that there is more room for them to swing for steering. And smaller wheels (judging from the original rendering you are already using relatively small wheels?) mean that the length of the wheel fairings are shorter, and this would also help them swing for steering.

Oddly enough, when I saw the Edison2 VLC and the Aptera SO-1 in person, this dynamic of the front wheel fairings getting *very* close to the chassis was the most unexpected aspect, for me. That and if they are too close to your shins as you get in or out of the vehicle -- look out!

And having four wheels on 'A' arms will be much easier than the hoops the Aptera had to go through; after the Cg got moved too far back in the SO-1. Again, this is another thing that was unexpected (though I did not see the fiasco moose test in person), that the anti-roll stiffness demand on the front suspension on the SO-1 is significant. So, the body roll aspect of a vehicle with outboard wheels (and also with road-going suspension travel; rather than a race car) means that the suspension arms need to be kept as close to the body as possible; and the suspension needs to be progressive rate, and/or active to keep the body roll to a minimum, and still ride well.

[dfbvt]

Pat Q

Thanks Dave for thoughtful replies. I generally agree with your positions and findings. I have some experience in Solidworks, but my previous attempts to model something along my lines using a 2CV chassis as a "skateboard" just didn't come together appearance wise. I greatly admire the elegant shapes worked out for the early Aptera and later Edison2, and I don't want to be seen in something that looks ugly.

I can feel for you in regards to trying to get Solid Works to do nice smooth curvy surfaces. It's actually downright difficult. I tried to help Neil Blanchard out a year and a half or so ago with his CarBen project and pretty quickly just gave up. However, now that I'm getting more serious about designing my own AEV I am working hard at teaching myself how to do it. I found a great training source on working with 3-D surfaces where a fellow by the name of Dan Lavoie did a complete F-16 with missiles and drop tanks as a teaching demonstration DVD. Its about 12 hours long but for $87 its worth it. If you're interested you can download it or buy a DVD at:

http://www.solidworksf16.com/solidsmack-deal.php

Dan is also done training DVDs on the Audi R8 & the Lamborghini Gallardo. The Gallardo is only 20 hours long...... if you're serious about this I do recommend you pick one of his DVDs and work with it. He does a nice job of it and it's worth the money.

One thing I should note is that my "pontoons" are meant to be part of the body, ie, bolsters that project outwards from the actual cabin walls to enclose the wheels, somewhat like that aspect of Neil's "boxfish". This reduces swept surface area compared to detached pants or pontoons, provides side-impact crumple zones, and resolves the inside-wheel turning radius.

Well, I think I sort of get the idea but I'm not really sure. Perhaps you are thinking of something more along the lines of what Ken Fry is doing with his Zing but with 4 wheels instead of 3? his website is at the following address.

http://www.gaiatransport.com/index.html

Well Pat, you got me thinking outside of my own box again so if you could just hand sketch what you are thinking about and either scanning or faxing it to me would be great! I did look at the videos of the 2CV which I admit I had never heard of before. It was certainly a well thought out small car. The two cylinder engine reminds me that many of the earlier light weight airplanes used VW bug engines cut in half creating a two cylinder opposed engine very similar to the FPT TwinAir. A good friend of mine actually did build an airplane complete with the cut in half of the VW engine. It flew quite well!

Finally, I don't doubt that popularity and competitive dealers have helped reduce the retail price of the large Warp-9 motor/controller, but if you are entertaining any kind of volume in your program, the inherent cost advantages of more optimally sized machines must come to the fore. AC Propulsion is the gold standard, but Azure, Curtis, and others have more moderate power packs (though not much lighter than AC Propulsion).

Actually I'm not totally stuck on using just the Warp series DC motors but I'm pretty sure I will go with them for my first prototype. I got to meet George Hamstra at the EVCCON show last fall and he is a very sharp fellow for sure. As for going with a AC power train I see that Curtis Instruments has recently been jumping on the light weight EV wagon and have been madly developing higher power AC induction motor controllers to that end. I guess they have seen the light and the days of the old and iffy Curtis controllers are gone. They also had a presence at EVCCON and I will be certainly be looking at them closer this year when I go.

Thanks for the new ideas and suggestions. If you get a chance please do send me a quick and dirty sketch of what you are thinking. Meanwhile, I'm sure my mind will be churning away on some new ideas that you have already sparked. I actually find that at this stage where you have an almost clean piece of paper to start with is probably the most fun part of conceptual designing. It seemed we still have a while yet to wait to see what the final fate of Aptera is so we might as well spend it in thinking of constructive new ideas.

Dave Bowles

[dfbvt]

Hi Neil,

Oddly enough, when I saw the Edison2 VLC and the Aptera SO-1 in person, this dynamic of the front wheel fairings getting *very* close to the chassis was the most unexpected aspect, for me. That and if they are too close to your shins as you get in or out of the vehicle -- look out!

That is an interesting observation. Thanks for sharing that. It sounds like a not insignificant strike against the wheel pant idea. Hummmm...

Thanks,

Dave Bowles