Project, the Third - Now contains collabsible boat tails (1971 VW SuperBeetle)

[Sven7]

Originally Posted by freebeard

What about this one:

I have a copy of the template with a caption that suggests treating the upper and lower surfaces differently (match height for the top, match wheelbase for the underbody). I did drop the ball on matching the underbody in the subsequent illustrations.


I read that as "if your going to 'fudge' it, you should really know what your doing."

botsapper -- How about front half VW bus, back half Bowlus Papoose (clone).

That one is not aligned with the roof apex and will give you incorrect angles at the beginning of the tail.

Yeah you can fudge if you know what you're doing, but do you have a commercial grade wind tunnel? I didn't think so

If you want to mess around for awhile with ABA coastdown testing and CAD (Cardboard Aided Design) that's fine by me; it'll be an interesting read. However if you want to go with what works I'd recommend following the lead of so many intrepid souls before us.

The trailer looks like it is much, much too short!

[aerohead]

Originally Posted by freebeard

And so we come to the driver. I won't say daily driver because I divide my travel needs between the bicycle (Schwinn Collegiate with a banana seat), city bus (I'm of an age where I can ride for free) and the 1971 SuperBeetle.

It was pretty much stock when I got it, It is 40 years old and has less than 100,000 miles. Since then I've made the following modifications:
• Renewed front suspension with adjustable MacPherson struts (we lowered it until it looked *good* and then raised it until it clears most traffic control bump strips)
• Rebuilt brakes (although I now question converting the front to disks) with the drums and rotors cryogenically processed to extend the part life.
• CB Performance electronic distributor (this is a billet housing full of Ford parts, the spark curve is programmable by swapping out springs) that possibly got 4—5 mpg increase in the first car I had it in.
• AM antenna delete
• Driver side mirror delete — this is temporary (honest, officer)
• Tire pressure maintained at 40 psi
• Nut behind the wheel lightly torqued

What works against me:
• Low miles travelled. The only time I would be able to gather data is on sporadic trips out of town.
• Incomplete data. No Onboard Diagnostic Port, no MAF sensor, no GPS
• Screwy data. The gas gauge is way out of calibration. Because the front tires are 165-45/15 the speedometer, which reads off the left front wheel, it wildly optimist. I can bury the speedometer needle at normal freeway traffic speeds.
• Eh, that's enough

What works for me:
• It doesn't look shabby, at least to start (it's a 5' car, get 2' away and you can start to nitpick chips in the paint and rust in the door hinges) so anything I do will reflect favorably on my fellow ecomodders.
• I'm familiar with the platform. Ferinstance, from hanging out on thesamba.com I learned you can get the correct kind of activated charcoal to repack the gas vapor recovery system by buying a $14 Cadillac part.
• The Bug Bearer bike rack. It is mounted with some custom brackets added to the stock bumper brackets. It peaks at the Template line and is 34" wide. I could make a K-back out of 2 or 3 layers of the plastic the use to wrap palletized freight.

What I'd like to do:
• Better instrumentation. The panel van had a head temperature gauge with sending units on the #1 and #3 spark plugs on a toggle switch. I could use the AM radio antenna mounting hole to install a pitot tube for (barometrically sensitive) air speed. maybe a MAF sensor in the bottom of the air cleaner to measure intake air. Using the Airflow Meter as a Dyno I'd like an engine vacuum gauge but I'm not sure about running a vacuum line the length of the car.
• Engine modifications. A Gene Berg Jet-A-Vator. Hot VWs got xx% improvement with this. Water/methanol injection so I don't have to run Premium grade gas for the octane rating. The H2O Way Part 2 Maybe electrical tape wrapped around the intake manifold runner for heat.
• Aerodynamics. Eventually a boat tail or Template-shaped single wheel trailer. But also front and side air dams. When I repaint, move the turn signals down off the top of the fenders, unless I start liking them after I chop them down to half height and put in LEDs.
• Replace the stock rear bumper brackets with a custom built class-1 trailer hitch. This would incorporate heavy-duty sockets for the bike rack that could double as mounting points for a single wheel trailer and tabs to mount the rear bumper. This would give me three options in back. Otherwise, I think I could build a boat tail that weighs little more than the stock bumper. I have no problem with driving around without bumpers or spare tires.
• Judicious torquing on the nut behind the wheel.

But enough jibber-jabber; let's talk boat tails.

Back when I first started seriously reading Ecomodder.com, I whipped up a Template primitive .obj object and held it up against a commercial VW model to see what's what. I was kind of dismayed that the boat tail is as long as the car's wheelbase. I also looked at messing with the Template by giving it a parabolic cross section and using three for that 1930s look.


The single aeroform is maximal, I held it as far forward as I could. The interesting part to me there was the area ahead of the rear wheels. Instead of fade-away front fenders, this might offer a solution that doesn't affect the doors.

The triple aeroform in minimal. If reducing the volume of the wake is beneficial, accepting a dirtier flow off the body might be acceptable.

For purposes of this post I prepared some side views with the template:

We begin

The Template

Ground clearance

What if we only do the rear fenders?

Move the same cross-section to the roof

Truncate the lower aeroform

I think I could live with this

If you want to consider component mods,'Aerodynamic Drag',by Sighard Hoerner is your friend.Hoerner worked for Messerschmitt during WW-II and was brought over to the U.S.A. under Operation Paper Clip.Hoerner personaly did full,automobile body discard and Jaray body replacement aero comparisons.His book is a treasure trove of streamlining.Complete breakdowns of every component on an aircraft is covered as well as cars and trains.His tables will show you how to best streamline any part of the Super Beetle.The 'Template' won't be applicable for all of that.
Ask a local librarian to find the nearest library which has a volume.If you make the trip with enough cash for the copy machine,you'll end up with one of the best reference books ever written on streamlining.I found mine at U.T.Arlington,Texas.Typically,these books cannot be checked out.

[metromizer]

Some pictures of my friend Dick Beith's VW Bonneville racer. I have some picture of the construction phase as well, if you are interested (but I took them with my cell phone, not very good quality)

Mostly retired, Dick is a bit of a celebrity as he set the very first SCTA land speed record using a VW, back in the early 1960's. More or less retired now, he started this project to go race at Bonneville again. He narrowed the front beam about 10" total, removing the bulbous front fenders entirely. He stretched the nose and hood about 24". The filler panels and new nose were made by hand. The hood was fabricated from 2 beetle hoods, opens and closes like the original.

He chopped the top and shaved the drip rails and laid the windshield back to 25 degrees. He also shaved the door handles. They open by using your index finder to push in a small oval button, that is flush with the bodywork. All the rest of the door latches are factory, which is pretty cleaver. He used lexan in place of glass, flush mounting them smooth with the body.

The shot from the rear shows the rear track was also narrowed, removing the fenders and hand fabricating filler panels, just like the front. The rear view shows these interesting vertical rectangular openings, between the rear apron and what were rear fenders. It was an attempt to channel air from the rear wheel openings, and fill the area behind the decklid with higher pressure air, to reduce drag.

[metromizer]

I wouldn't discount a vacuum gauge for the VW engine. I'd use a metal line the length of the car, and short sections of rubber hose only where you need the flexibility. I have about 6' of rubber line in my metro's vacuum gauge line, and it works fine. I did have to buy an in-line vacuum orifice (the small one) to damp the vibrating needle, Balcamp brand from Napa Auto Parts I think.

I've used one of those speedometer cable gear boxes on a Nissan truck years ago. They are ok, but you need someone to initially set them up for you, someone who has several gears to choose from. I did it before GPS, the automotive speedo calibration shop i took it to had an in-ground roller set up. An inexpensive Garmin GPS can double as a speedometer, I do it when playing with VW's. There is a dashboard setting that shows MPH in real time, that I've used on rallys and racing at Bonneville. If nothing else, borrowing a GPS could help you cross calibrate your speedometer, masking tape arrows on the glass noting 25, 40, and 55, and 65mph.

[freebeard]

Aerohead -- Thanks—that's a good suggestion. Do you have the ISBN (number) or the publishing house? I suspect a librarian would want to know.

Metromizer -- I admire Dick Beith's car. My thinking is evolving away from what is shown in my profile picture. I'm going to be Away From The Keyboard for a few days. When I'm back I'll try to document an Edison inspired Very Light Volkswagen (VLVW).

The side windows are an aero-problem. The flush-mounted Lexan looks good; and I'm thinking a user applied coating like Nanoclear
(today) or Spray-on Glass (tomorrow) would make it easier to live with.

I was thinking a shop sized vacuum gauge mounted right under the backlight where I could monitor it in the rear view mirror. But then I also want a boat-tail that covers the backlight with a 20" LCD screen for the rear view webcam that I could see in the rear view mirror—in Infra-red!

[some_other_dave]

Originally Posted by freebeard

I believe the MPGuino would work with a carbed, non-OBD-II engine.

It would be difficult to set that up. The MPGuino, as it starts out at least, requires a digital speedometer signal (electrical pulses), and a fuel injection signal (also electrical pulses). Probably both in the 0V-5V range, square waves or close to it.

You'd have to either use the tach signal from the distributor (and probably filter it heavily) or you'd have to make some sort of transducer or Hall-effect gizmo to send the speed signal.

There are no injectors on a carb'ed car, so I'm not sure what you would use to tell how much fuel is going into the engine.

• I saw some discussion here of in-line flow meters that made it sound like it's hard to measure the small volume flow accurately. But late model cars do it somehow.

Late model cars actually approximate the fuel used by either knowing the amount of time the injectors are open (that's how the MPGuino does it), or by knowing the various parameters that get fed into the engine management system and figuring out how much fuel "should" be going in under that set of circumstances.

I guess my earlier thoughts were a bit of pipe-dreaming.

-soD

[freebeard]

I guess my earlier thoughts were a bit of pipe-dreaming.

I'm not saying I'm going to go right out to the shop and prove you right, I catch a train to Seattle in 3 hours; but, maybe...

I don't write code myself, but I've been close enough to Open Source software to see the way the world is going. *Anything* is possible if you can coax the source out of someone, somewhere.

Speed is not a problem, use a bicycle speedometer. Fuel flow it the tricky one. Somewhere on the inter-tubes within the last maybe 30 days I was looking at a discussion of using the turbulence of two posts in the free flowing fuel shedding vortexes to sense small quantities of fluid flow.

It's really hard to fit all this stuff in my head.

[AndrzejM]

Originally Posted by freebeard

... Fuel flow it the tricky one. Somewhere on the inter-tubes within the last maybe 30 days I was looking at a discussion of using the turbulence of two posts in the free flowing fuel shedding vortexes to sense small quantities of fluid flow.

It's really hard to fit all this stuff in my head.

You can see one of the possible solutions of this issue here: http://ecomodder.com/forum/showthrea...tml#post292922

Just read the following posts.

[botsapper]

Oh that tail. Someone has already photochopped it in...metal.

http://www.youtube.com/watch?v=4hx7qA8Ozjg

[some_other_dave]

Originally Posted by freebeard

Speed is not a problem, use a bicycle speedometer. Fuel flow it the tricky one. Somewhere on the inter-tubes within the last maybe 30 days I was looking at a discussion of using the turbulence of two posts in the free flowing fuel shedding vortexes to sense small quantities of fluid flow.

Interesting!

Another way to do it would be to approximate it. You can get the tach signal (as I said, you'd have to filter it) and add a manifold pressure sensor, or possibly two sensors--one in the manifold, and one in the air cleaner. You should be able to approximate the fuel flow through the carburetor if you know the pressure differential across the metering nozzles in the carb. You might have to add a throttle position sensor to work out accelerator pump volume.

Heh, basically you'd be doing all of the calculations for fuel injection without actually powering the injectors.

Originally Posted by AndrzejM

You can see one of the possible solutions of this issue here: http://ecomodder.com/forum/showthrea...tml#post292922

Thanks, I hadn't noticed that thread!

Originally Posted by botsapper

Oh that tail. Someone has already photochopped it in...metal.

Looks a lot like a Tatra from some angles.





-soD