Lotus 7/Locost Aero Rebody

[chuckm]

I'm not so sure, but I would not be surprised if the 4sqin per 25 hP is accurate for anything 35mph and higher. Here's my thinking:
1) The air permitted through a radiator does not scale linearly with speed. Though I don't have anything to support this other than a intuition and a Scanguage, I suspect that most radiators produce the highest ratio of cooling to engine heat production around 40mph.
2) Engines can, depending on the engine bay configuration, can shed an awful lot of heat even without the aid of a radiator, hence air-cooled small hP engines. When you are operating your engine at low load, the actual cooling requirement is relatively low, but still higher than what could be taken care of through natural (non-forced) convection, especially with a closed engine compartment. Stop-and-go compounds the issue because of the intermittent medium/high loading. But drive a constant 25mph and your fan probably will never come on.
Jack, for your purposes, I would still probably end up around 16-24 sqin of radiator opening. That's plenty of safety factor to compensate for not having a team of aerodynamicists to herd the right amount of air where you want it, not having perfectly optimal radiator placement, and a host of other unknown factors. I'll sacrifice a point of cD to insure I don't burn an engine up. The penalty for an opening that may be 6" x 4" can't be that astronomical. The penalty for a burnt engine will be much higher than any gas you'd save.

[beatr911]

Not to harp on this grill block issue too much but I really think 16 sq in will be way more than enough. 20 sq in on my 112hp 3500# Ford is enough to not even require an electric fan. My only safety is the cabin heater which is remarkably effective, but the Locost probably doesn't have one.

[JackMcCornack]

> ...you would wind up with something very much like a '70's era Can-Am...

I think 1970 is too late. By then the road racing industry had figured out that downforce improved lap times more than streamlining did. By 1964 the writing was on the wall--smooshing the tires onto the road was more important than going fast down the straightaway. For us ecomodders, the straightaway speed per hp is what matters.

And you guys have convinced me--I'll try 20 square inches for the radiator inlet.

[jamesqf]

Originally Posted by moTthediesel

...speeds of 70 mph and less. I would hope that velocity is well below takeoff speed, even for a car that's shaped like a Clark Y airfoil!

I dunno... My Cherokee will lift off at about 55-60 mph.

[JackMcCornack]

Here's what the body plan used to be, back when it was going to remain a roadster. This is from screen shots, the data is gone, but in the do-over I want to increase the raiduses of all the edges and not make the stern so steep, bring the rear of the rear fenders in a la 1st gen Insight, and add rear fender skirts. And it's agreed I don't need this much radiator inlet. The coupe conversion remains a challenge.

[moTthediesel]

Originally Posted by jamesqf

I dunno... My Cherokee will lift off at about 55-60 mph.

Sure, but I think that with a "wingspan" of about 4', the wing loading on a Type 32 Bugatti would be somewhat higher than on your Piper

[beatr911]

Jack,
I like the renderings you are doing for this stage of the project. Rhino looks like great sandbox to test out ideas.

The area behind the front wheels looks to be a massive air cooling exit on each side. If there isn't enough air to fill the void from the radiator it'll increase turbulence/drag. Maybe make these 1/2 width of the tire? Radiator air will be sucked out through the gap between the fender and the tire anyway. If the rad is behind about the front wheel centerline I vote to close the gap around the front wheels entirely and exit radiator air under the car or through the driveshaft tunnel. (I seem to be a little cooling air mesmerized lately, excuse me.)

Also in the next model, the tires could be narrower. Maybe design around some of the more common LRR tires in the Prius size. Guessing a 195/60-15, or pretty close anyway. The 3/4 rear view looks like about like a 235/40-sumptin.

I like the idea of a flatter slope to the rear. Someone here said a maximum of 11 degrees at freeway speeds is good for continuing attached flow, if there is any.

Your metro middy idea seems like a really good starting point for the clean sheet. I'd like to know more. Metros are getting old, not too many more years and it'll be hard to find good donors. (Nudge, nudge)

[QuickLTD]

That sort of reminds me of these Panoz race cars

[Peter7307]

Originally Posted by JackMcCornack

What makes this project interesting is I have about a $2000 body budget. If I had unlimited funds, I'd do something like this Bristol 450 LeMans racer (shown in blue over a red Lotus Seven) of the early '50s (though not so steep on the back because I know better--I have my Hucho and Bristol didn't). 58340131[/IMG]

Agreed Bristol didn't have Hucho but then they did have a wind tunnel and a vast amount of experience dating back around half a century by 1955.

They may not have read the book mentioned but they did write a few themselves.

Cheers , Pete.

[JackMcCornack]

> The area behind the front wheels looks to be a massive air cooling exit on each side.

Right, plus it allows the wheels to turn when you move the steering wheels.

This body project wasn't originally as pure a mileage maker as it has developed into. The original goal was a cheapo body to make Locosts equal to a Miata in CdA and lower than a Miata (or standard Locost) in lift, and with some inexpensive mods (a splitter in front and a wing in back) trade drag for downforce on track days. The slightly too steep rear deck led to a vertical spoiler, to move the center of lift forward and reduce overall lift. But now that we're in ecomod mode there are changes to be made, and this seems a better venue for suggestion than the Mother Earth News site.

> Your metro middy idea seems like a really good starting point for the
> clean sheet.

Yeah, and if I wasn't so fully committed to the MAX project I might have changed horses midstream, but a lot of people want to see how MAX turns out, so first things first. Besides, front engine rear drive cars are cool (see the Panoz pics above).

> Agreed Bristol didn't have Hucho but then they did have a wind tunnel and
> a vast amount of experience dating back around half a century by 1955.

True indeed, plus they had all the Kamm and Jaray papers that Hucho built his book around--but Bristol didn't really get rolling on the 450 until '53 (they bought the design, less bodywork, from English Racing Automobiles at the tail end of '52) and by '55 they'd taken off the cabin and were racing it as a roadster (it had less drag as an open cockpit car, with a tonneau on the passenger's side). Nevertheless Bristols were 1-2-3 in the 2 liter class at Le Mans '54 with that coupe design (shown on page 1 of this topic) so it couldn't have been a complete turkey, and if I wanted to build a $30,000 car instead of a $10,000 car I'd let the Bristol 450 be my inspiration,