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Analog Logic for Tube Based "Computer"
Analog Logic for Tube Based "Computer"
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Old 3rd August 2018, 06:54 PM   #11
PRR is online now PRR  United States
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Carburation is not naturally a job for electronics. There's no naturally electrical details. While we are surrounded by electric injectors, this can be done all mechanical. As was done on late WWII aircraft, and the late 1950s GM injection. As a contrast, look at the history of the Mopar electronic injection:
1958 DeSoto Electrojector - First electronic fuel injection?
All the cars built with Electrojectors were changed back to carbs. (One was much later gotten working OK with the fuelie.)

Don't multiply voltage. Multiply in time. Ramp waves and comparators.

Don't think in RPM. What the engine really wants is one lump of fuel for every intake stroke. The size of this lump a function of manifold pressure. For non-sync injection (works fine): at each spark trigger, a one-shot makes a ramp. A comparator takes this ramp and manifold pressure, naturally gives the Product. When the engine is cold, reduce the current to the ramp generator, you get a longer/larger lump.

Swapping-around: the ramp generator target could be proportional to manifold pressure. Now a fixed voltage comparator does about the right thing. The "fixed" voltage could vary with temperature.

There also wants to be separate trims for idle (air leakage foils accurate computation) and full-power (we normally over-compress for economy, then suppress knocking by going rich at WOT).

All of which dodges the question: why the heck injection on a flathead?? Ignoring inverted flight and hi-alt carb icing, the usual reason is that a carb must extract energy from the incoming air to do its computations and make fuel flow; the injector does not obstruct the intake air (but must get energy from shaft or dynamo). However a flathead already has such a convoluted air intake that the carb does not dominate the intake restrictions. Yes, I know: millions (well, hundreds) of Hilborns on flatties say it works. And made sense when old Fords were the only engines so abundant that you could afford to blow them up weekly. But the Caddy OHV breathes so much better it aint funny. Chevy V8s too, and are super abundant.
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Old 3rd August 2018, 08:45 PM   #12
Pano is offline Pano  United States
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Analog Logic for Tube Based "Computer"
Geez! This is a thread you can really sink your teeth into. Tube controlled fuel injection for a '49 flathead. Wow., and thank you.
Take the Speaker Voltage Test!
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Old 7th August 2018, 03:38 AM   #13
PRR is online now PRR  United States
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You want this book:

Handbook of Industrial Electronic Circuits, 1948, J Zeluff, V Markus

I'm not sure how much is directly useful. But it is a good show-and-tell prop when people meet your flathead. And it may teach you some about how they thought back in the day.

Fer example: here is an aircraft turbo control.

Some things you never see today. The power stage works on AC not DC. So while it looks like the 7C5 power tubes are driven parallel, actually only the one with positive plate conducts. This puts AC into a 2-winding motor which screws the wastegate knob.

Down right: all those curlies are on the main transformer and deliver small floating AC voltages. The four pots tap-off fractions of winding voltage. Some of them go in-phase to out-phase, which when amplified drives the wastegate in or out. A bal-pot closes the the NFB loop. (Everything is AC except the 7Y4 makes a little DC for the 7F7 gain stage.)

Power is 115VAC. Hey, a B-17's core is about the size of a house, and the heated flight-suits pulled power like a small house, not to mention a radio-rack as big as some hometown radio stations. However it was 400Hz which is awkward on miles-long lines but makes transformers and motors much lighter.

The book is full of stuff. Some quite simple, some quite arcane. But even railroad splice detectors sometimes have odd details which may be of use elsewhere. (And yes, some "audio", little of real interest.)

Oh-- the "Selector" pot is grounded because that's at the pilot. All the rest is out in an engine pod. This way minimizes wiring. While this is more likely for a B-29, here is how you service the "spark vibrator" on a B-17. (The black thing above the left corner of the ladder is the hub of the turbo.)
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File Type: jpg B17-legs.jpg (80.2 KB, 37 views)

Last edited by PRR; 7th August 2018 at 04:06 AM.
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Old 7th August 2018, 04:01 AM   #14
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Wow! That leg hole is even smaller than the smallest submarine hatch.
I bet a 491 spectrum analyzer might fit through it, but a 492 spectrum analyzer will not.
The Navy would probably reject such a small passage, or have the submarine modified.
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Old 10th August 2018, 12:06 PM   #15
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My copy of the handbook is on order. Thanks!

I admit that logic plays no role in my fascination with flatheads.
For all of his tragic flaws, I respect Henry Ford for two things; the democratization of the auto via the Model T, and the democratization of racing via the flathead. Both were previously the privilege of the aristocats and he made them available to all.
As a manufacturing engineer I also love innovations in manufacturing, and the casting process which enabled the flathead was pure genius. V8s had been known for years, but could only be produced at great expense. But "Cast Iron Charlie" at Ford revised the casting process to enable mass production.
In addition I love grassroots innovation. And as the flathead was the first low-cost engine with reasonable power it became a magnet for shade-tree innovation. Hilborn was one of the few who became famous, but others dropped flatheads into P-38 drop-tanks for low cost streamliners (or lakesters) to race on the flats (the flathead has less frontal area than OHV engines), supercharged them with military-surplus roots blowers, and invented the quick-change rearend so that the only team you needed was a buddy and a girlfriend help to reconfigure your car from drag-racing in the morning to circle-track in the afternoon. You might not win, but racing was more like playing golf or tennis. The event was generally more social than bitter competition.

My roadster has a Model T body, a Flathead V8, and a home-made quick-change. So All I am missing is a 6-71 blower and the tube-based injection that should have been built by one of those GIs who came back after working with both fuel injection and tubes. I have a pair of 6-71s on the shelf in the garage, so now let's talk about tubes...
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Old 10th August 2018, 12:29 PM   #16
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A previous reply took me here:
Audio Synthesis via Vacuum Tubes

It seems really elegant to do this with a single tube, with one signal on each of three grids.

The only tube I have found which seems to be intended for this is the 5915.

Are there others?

The data sheets for the 5915 provide curves for using either grid 1 or grid 3 for the signal, but not for using both at the same time. Are there references out there for doing so?
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