Lotus 7/Locost Aero Rebody

[Tango Charlie]

Originally Posted by JackMcCornack

...somebody please tell me (in painstaking detail) how to post jpgs on this site. Everything I've posted to date has come out a thumbnail.

I'm barely computer literate, but I'll take a whack at it. This is how I do it;

1. Open another tab and go to Photobucket.com
2. Register and open an account (it's free)
3. Upload your pictures to photobucket.
4. Hover your cursor over the picture you want to insert. A list of links will pop up.
5. Left-click on the yellow box after 'IMG code' (the one at the bottom). It'll highlight.
6. Right-click and select 'Copy'.
7. Go back to your ecomodder tab and left click in your post where you want the picture. This places the cursor where you want the picture to appear.
8. Right-click and select 'Paste'.
9. Select 'Preview Post' to admire your new-found mastery of digital data.

This is me wielding computer technology;

[jamesqf]

Originally Posted by JackMcCornack

Whaddyamean, jamesqf, like the ones on my avatar?

That one missed me: I don't see an avatar. But then I do use some custom user style sheets to get things to show up so I can read them, rather than the way some web site designer thinks is cool.

Yeah, there's some low hanging aerodynamic fruit on that car, all right. Front fenders were the first thing to go.

That picture's pretty close to what I was thinking (great minds, you know :-)), though what I was suggesting with the foam is a sort of radiused effect behind the wheel, like on the original Honda Insight.

I rather like the idea of fiberglass (or whatever) over foam, especially given that there's a lot of experience in the experimental aircraft community. But then, I'v also wondered about using doped fabric to make really lightweight body panels...

[Bicycle Bob]

Doped fabric has an ancient history in automobiles. Rather than let the ribs show, as on aircraft, the Weymann body had a "conventional" wooden frame, and instead of metal panels, used upholstry techniques to get shape, and paint for gloss.

[Frank]

Neat car - I was just reading about it last night in Mother Earth.

[moTthediesel]

Jack,

I don't know just how "clean sheet" you want to go with this project, but it just seems to me that the pontoon fender style body is always going to be inherently "dirty" from an airflow standpoint.

To look to history for an example of a "clean" body shape that would also be easy to construct, how about the Bugatti Type 32 Tank?

http://www.acmenovelties.net/cars/20...pe_32_tank.jpg

That shape could be built fairly easily using big box store foam insulation board covered with fiberglass. Add a Kamm-back top and full wheel skirts and you could have a very clean and light cover for your running gear in short order.

You might wind up with something that looks like it escaped from the prop room of the Buck Rodgers serials, but I for one don't think that's a bad thing!

I love your project -- keep up the good work!

[jamesqf]

Originally Posted by moTthediesel

To look to history for an example of a "clean" body shape that would also be easy to construct, how about the Bugatti Type 32 Tank?

Interesting... But with an airfoil profile like that, wouldn't it develop lift at speed?

[Funny]

Looks like you have a lot of work to do to this thing. Any stats on what is under the hood, um "bonnet"?

There is almost an unlimited amount of variables that you could consider for this, because of the stripped down construction of the Locost. I personally like the image overlay in the first posting, but with a 'slightly' longer back end. Closing up the front fenders, like on the Aptera is another avenue you could take.



If you are limited to $2000, but are doing the glassing and bodywork yourself, I think you could make one hell of an aerodynamic vehicle worthy of 100 mpg. I look forward to more posts

[beatr911]

Jack,
Because of the cab rearward characteristic, the more or less fixed value is the low pressure in the rear of the car. As you've said, some tapering can occur but not really that much. The bright side is that there isn't alot of area to start with so potentail still exists.

Instead of trying to make it more teardrop shaped, I would think that the focus should be on smoothing. Try to ensure that each air molecule encounters only one high pressure point along its path to the low pressure area in the rear.

The rear fenders present a large second high pressure point to air that has already encountered the nose and or the front fenders. Iether fair in the rear fenders to the front, and/or narrow the rear track with wheel offset or axle width. This may mean installing half height "doors" to allow entry/exit. Fish are made with wider mid-sections, so bowing out the middle might help here also. Steeply sloped front glass would reduce the peak pressure for air coming over the nose allowing more gradual spill-off to the sides and top.


I also had this response to the MEN thread on a grille block but was unable to post:

I've read somewhere that for nascar cooling systems that are fully ducted in and out, the rule of thumb is about 4 square inches per 25 horsepower produced. For my 112 hp Ford Ranger the 20 square inches of grill that is not blocked off is plenty - provided I'm moving. The radiator fan, clutch and shroud have long since been removed.

Most grille opening tuning is done by how often the electric fan comes on with FWD vehicles. I'd suggest removing the belt driven fan if you have one and install an electric fan or closely monitor the gauge. Then make the grille opening size by the above rule should be about 5.5 square inches if I have your horsepower correct at 35 hp. Best to duct or seal to the radiator to reduce leakage around the radiator, and center the opening to the radiator.

For air exit, there should be plenty of space around the driveshaft tunnel to exit out the low pressure in the rear, if you install a full length undertray. You’d end up with air pressure in the front and suction in the rear making the system quite efficient. Monitor oil temps because the sump can do a fair bit of oil cooling. If additional exit area is needed for more cooling, the front wheels are in a low pressure area enabling more cooling air evacuation.

Test and adjust as needed for your expected driving conditions. Additionally an adjustable louver or door would allow a small advantage in cooling system aerodynamic losses when not running full throttle or in heavy traffic.

Looking forward to seeing you in the spring for our MPG Rally in Lacey, WA!

[JackMcCornack]

Thanks for the comments. y'all.

> I was suggesting with the foam is a sort of radiused effect behind the
> wheel, like on the original Honda Insight.

Well, if you could see it from the top you'd see the sides are tapered in behind the rear wheels...but you'd have to read my mind 'cause I haven't drawn it yet.

> I rather like the idea of fiberglass (or whatever) over foam, especially
> given that there's a lot of experience in the experimental aircraft
> community.

Yep, that's where most of mine came from.

> it just seems to me that the pontoon fender style body is always going to
> be inherently "dirty" from an airflow standpoint.

For those that <can> see my avatar (that little orange car) you'll see there's an unnecessary gap 'twixt the upper part of the fender and the hood/bonnet. My excuses are it's inexpensive, it can adapt to a variety of track widths and engine sizes, and I've already made the fender molds so might as well give it a try.

> To look to history for an example of a "clean" body shape that would also
> be easy to construct, how about the Bugatti Type 32 Tank?

I'm not convinced it's clean--I think it slopes down too steeply in the back. That Bugatti looks to me like a car that's begging for a Kamm tail. It sure would be easy to make, though, and MAX only goes 71.5 mph so I don't think lift is a problem. Comments?

> You might wind up with something that looks like it escaped from the prop
> room of the Buck Rodgers serials, but I for one don't think that's a bad
> thing!

I hear you. To quote my own web site re the long green Kamm tail, "... it has the designed-by-committee look—a committee of Paul Jaray, Wunibald Kamm, Jules Verne and George Jetson." If I made it out of hammered copper it would look totally steampunk.

> Looks like you have a lot of work to do to this thing. Any stats on what is
> under the hood, um "bonnet"?

Heck yeah, this car is as open source as I can make it--the web site gets down to what clutch disk and pressure plate you need. It's a Kubota D1105-T, a turbocharged three cylinder industrial engine, 32 horses with steaming flanks. It's mated to a RWD Toyota Corolla T-50 transmission, five speed, overdrive 5th.

> ...for nascar cooling systems that are fully ducted in and out, the rule of
> thumb is about 4 square inches per 25 horsepower produced.

At what airspeed? Mine's a slowpoke. Based on that rule of thumb, I'd need an intake opening the size of a playing card. But I'm testing the question at present, with cardboard grill blocks and ducts, and I'll bet it ends up pretty dang small...not playing card small, but maybe trade paperback small.

[moTthediesel]

Originally Posted by JackMcCornack

Thanks for the comments. y'all.
> To look to history for an example of a "clean" body shape that would also
> be easy to construct, how about the Bugatti Type 32 Tank?

I'm not convinced it's clean--I think it slopes down too steeply in the back. That Bugatti looks to me like a car that's begging for a Kamm tail. It sure would be easy to make, though, and MAX only goes 71.5 mph so I don't think lift is a problem. Comments?

That was my thought too about the sloped back -- there would probably be some flow separation there, but it sure looks mega-cool. With a Kamm style tail you would wind up with something very much like a '70's era Can-Am or prototype, such as the Porsche 908-3 http://www.autoblog.com/media/2006/07/300606-c-por-.jpg. With the power those cars had on tap though, I'm not sure low Cd numbers were their principle design criteria.

Your point about design speeds are well taken too, I'd bet that few race car and airplane aerodynamic studies have concentrated on 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!