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MAX Update No. 29: Cardboard-aided Design

Don't pay the ransom, I escaped! Wow, it's been a busy month for me, and I apologize for the lack of updates recently.

The last weekend in May was MAX's farewell public showing in its Escape from Berkeley trim, at a fun, wonderful event called the Maker Faire.

We were there to show the flag and drum up business for Escape from Berkeley II. I figured if the Escape folks were willing to give us five grand for winning the event last year, the least we could do is encourage others to join in the fun this year. So we pulled off the streamlined body bits and put back the stylish-but-slow fenders and lights and all, and drove down to San Mateo, Calif., for one last hurrah.

Now we're back, and we have to knuckle down on the streamlining. In order to reach 100 mpg, we’ll have to get MAX down to the drag coefficient of a typical modern sports car.

The drag coefficient (aka “coefficient of drag”, abbreviated Cd) is a comparison of the drag of an object versus a flat plate of the same frontal area. A Mazda Miata, for example, has a Cd of 0.38.

MAX gets better mileage than a Miata because (among other things) MAX is so small it doesn't have a lot of frontal area. But MAX’s Cd is about 0.7, which is pretty terrible. That’s about the same drag coefficient as a shoe box.

MAX new windshieldObviously, we have to make a lot of improvements, and one feature we can improve is a curved windshield. Hey, if you were making a windshield for a shoe box, it would look a lot like MAX's windshield does now — a flat panel right across the front of the cockpit.

But unfortunately a curved windshield will blow our $10,000 budget, because there's nothing off the shelf that will fit MAX (the windshield is only 33 inches wide — more than a foot narrower than the Miata windshield, for example) and custom-curved windshields cost a bundle.

So how about a split windshield, with a steep rake and a deep V to emulate a curved windshield? It'll be pretty cheap, and it would add to MAX's old-timey personality. I think I like it ... though I wasn't willing to commit the glass cutter before I saw how it looked.

Cardboard is a nice medium for conceptualizing design features, but it has its limitations. It should come with a sticker that reads, Warning: Remove Cardboard Before Operating This Vehicle. Nowhere would that be more important than the windshield …

Photo by Jack McCornack


Browse previous MAX Updates.
Read the introductory MAX article, Here Comes the 100-mpg Car.
Visit the Kinetic Vehicles website for more technical details on MAX.
roo trimble_2
7/8/2009 12:09:57 PM

I like to use blue masking impatient to cut all that cardboard see lots of tape on my project at ! Cant wait to see the body: also any tips on cutting a curved windshield? my first try was a disaster... hope to see MAX done soon! Roo

6/26/2009 4:37:19 PM

Hi Jack it was more about Max being 33 inches wide, the Tango is 39 inches but looks to be narrower at the screen area and also seems to have A posts! I guess I was wondering if you could just purchase one windscreen for your aero shaped MAX rather then the standard kit. If the plan is to provide a ongoing kit then yes I would agree split screen would be easiest. Looking forward to the next update. From another builder cheers Adrian

jack mccornack
6/25/2009 8:50:26 AM

Adrian, the Tango windshield is awfully narrow, I doubt they found one off-the-shelf that fit their car. I'm presuming that Commuter Cars Inc spent what they needed to have custom windshields made, and that's not in the cards for MAX. The Tango is a $100,000 car and MAX is a $10,000 car, and the Tango is designed to be factory built and MAX is designed to be built at home. For a homebuilder, I think a split windshield will give the best bang for the buck, but time will tell, and what the hey, I might as well send Commuter Cars an e-mail and ask.

6/20/2009 12:52:51 AM

I saw a story of the car over here in the UK and have been following it via this site since. A good goal to aim for and a good way to have fun along the way. If I hear of the next makerfair in the UK I would like to attend that. For a windscreen why not try and se where they got the windscreen for their Tango, let someone else pay for the development, just an idea. Cheers Adrian

jack mccornack
6/13/2009 2:19:05 PM

Thanks for the comments, guys. Uncle Rice: >Your cardboard windshield is on top of your hood. I look forward to seeing how you fix that. The options are add a wedge to the scuttle and cut a wedge out of the hood, or (and I like this one better) tilt the front roll bar back a bit to move the windshield back a bit. Mike: >Why couldn't you use an aluminum frame and lexan for the windsheld. Sadly, the Oregon DMV (and Federal standards as well) demand safety glass. As to the aluminum frame...we live in deer country and I'll probably get into that subject in another post or two. Lee: >Disregarding how it would look for a moment, could you cut the center ~12" out of a curved window and have a split curved window? "Disregarding", eh? I think it would look cool. The problems are cost and repeatability. MAX is designed to be built cheaply, with simple materials and simple tools. Right now when Kinetic sends out a windshield frame kit, we draw a (flat) windshield template on the box--I don't know how we'd do that for a curved windshield. John Adams and James: For the length of the Auburn-style boattail, I think we can get better streamlining if we have the tail section drop down as well as in...I think you've hit it on the nose when you say "somewhat sleek but mostly pretty." Perhaps a compromise is in order. More posts coming soon, I won't leave you hanging for a month again.

6/13/2009 12:56:40 PM

Your cardboard windshield is on top of your hood. I look forward to seeing how you fix that.

6/12/2009 11:25:07 AM

Why couldn't you use an aluminum frame and lexan for the windsheld. It would be cheap and light weight.

6/12/2009 12:08:58 AM

I like the Auburn idea, and I think the boat tail should improve the aerodynamics considerably. Lose the external pipes and mount the headlights in the front fenders...

6/11/2009 7:42:55 PM

Disregarding how it would look for a moment, could you cut the center ~12" out of a curved window and have a split curved window? (just thinking out loud)

john adams_3
6/10/2009 9:22:36 AM

Always fun reading about MAX. The split window got me thinking,have you thought about styling it like a 193X Auburn Boattail? Somewhat sleek, but mostly pretty, although the boat-tail and schwoopy fenders could not hurt (much). Good luck and keep up the great (and hard/rewarding) work.