EEVblog #854 - B52 Bomber Automatic Astro Compass Teardown

[Kjetil]

Great find. These old training films are always good information. It seems like a mess of gears and shafts until you see how it breaks down into simple easily understood bits as shown in the video.

Yeah, there's lots of great info in them. It's pretty amazing to see how simple the various functions actually are when you translate them to mechanical function, and a great way to visualize the functions they actually perform

[dexters_lab]

I have already seen a star tracker dome for sale on ebay, can't remember the final price it went for. And Dave speaks about the sonobuoys in the video, I already had the opportunity to take one apart, it was a old one form the 70, in very bad condition, but still, something you don't have the chance to take apart every day ! 

i'm guessing the star tracker part went for $$$ then?

would be nice to see the guts of one...

[andy_cristea]

Beautiful machinery.

This video explains many of the mechanical/mathematical functions:

Thanks for the video!

[philpem]

I'm going to look up some co-workers from Kollsman. The inventor of the first practical aircraft altimeter.

I worked there during this time, and being in EE land, I was amazed at designs coming from experts in other fields, especially mechanical genius.

Interesting! I've got a Kollsman (actually Negretti & Zambra, made under licence from Kollsman) L31523-10-009 tachometer sat on my shelf - I picked it up in a junk shop as a curiosity.
It actually seems to run up OK, but one of the three "needles" makes a hell of a grinding noise when the motor is powered, and the needle bounces all over the place, so I suspect it's had a bit of a bump and needs some mechanical TLC.

Looking at it again there's a bit of a bead around the back... part of me is tempted to strip the paint and see if that's a solder bead like Dave's thing. Maybe I can open it up and fix it.

I have the solder tape hanging over my bench as I speak, and is easy to remove with a big ass soldering iron.

I don't suppose you happen to know what alloy it is?

Good to know it's removable with the Mk1 Bigass Soldering Iron though. I'll see if either my gas iron or my Metcal are man enough to pull it off.

Cheers,
Phil.

[f4eru]

Cool "Heavy metal" computing

similar stuff : https://www.flickr.com/photos/64683169@N00

[HAL-42b]

I don't suppose you happen to know what alloy it is?

Aluminium or Magnesium.

Magnesium is kinda fire hazard in a war plane but it is light and rigid. There are also aluminium alloys which are brittle enough to chip when hit. Al-Ti or Al-Li alloys for example.

[EEVblog]

I don't suppose you happen to know what alloy it is?

Aluminium or Magnesium.
Magnesium is kinda fire hazard in a war plane

That was my first guess and I came to the same conclusion, I doubt they'd use magnesium.

[philpem]

I don't suppose you happen to know what alloy it is?

Aluminium or Magnesium.
Magnesium is kinda fire hazard in a war plane

That was my first guess and I came to the same conclusion, I doubt they'd use magnesium.

I wasn't aware that there were any aluminium alloys which would melt at normal soldering temperatures. But then again, we have 60/40, and the melting point of both tin and lead is much higher than the melting point of 60/40 solder...

[RobertoLG]

I don't know if I'm saying some BS here, but maybe there are some titanium parts in this thing?

[HAL-42b]

I wasn't aware that there were any aluminium alloys which would melt at normal soldering temperatures. But then again, we have 60/40, and the melting point of both tin and lead is much higher than the melting point of 60/40 solder...

Well... both Aluminum and Magnesium are completely impossible to solder. The only thing that would make them solderable is some sort of plating for the solder to stick to.

[ajm8127]

You can "solder" aluminum and other metals. It is called brazing and the only difference is the temperature at which the filler metal melts. Copper, brass, aluminum, nickle, iron, steel and stainless steel (and probably others, I'm not an expert) can all be brazed. A brazed joint is usually stronger than a soldered one. I think there is some association between melting point and yield strength.

That old military training video was awesome. Of course you can use a high level language to program a computer to solve a problem, but I think using a machine so very elegant, albeit necessitated by the technology of the times. 

I would love to see a tear down and subsequent documentation of that navigation unit to figure out how it works. That might be outside of the scope of Dave's blog, however.

[bills]

Beautiful machinery.

This video explains many of the mechanical/mathematical functions:

WOW !
That is amazing, to build that type of machine with the tool's they had at hand I am in awe.
bill

[Tothwolf]

I don't suppose you happen to know what alloy it is?

Aluminium or Magnesium.
Magnesium is kinda fire hazard in a war plane

That was my first guess and I came to the same conclusion, I doubt they'd use magnesium.

The upper housing appears to be made of cast aluminum (which is why it broke when impacted). It actually is possible to solder to aluminum with tin/lead alloy solder but you have to use a very active flux to cut through the aluminum oxide so the solder can wet. If it wasn't soldered, it might have been brazed using a zinc alloy filler.

The round connectors are most likely some type of Bendix connector. The contacts and the crimp tool are readily available if you can find the correct housings.

[AF6LJ]

This was Really Good Thanks Dave

[Fungus]

I don't suppose you happen to know what alloy it is?

Aluminium or Magnesium.
Magnesium is kinda fire hazard in a war plane

That was my first guess and I came to the same conclusion, I doubt they'd use magnesium.

Plenty of WWII warplanes were made of Magnesium. It's not that easy to ignite.

(maybe they were desperate times and the other advantages of Magnesium outweighed the fact that it could burn)

[PinheadBE]

Now, THAT thing is a BEAUUUUUUTY !
I don't like it, I love it! 

[Smalltalk-80]

The D-17B was probably very highly classified and even the Apollo mission wasn't allowed to use it and had to come up with the Apollo computer.

Also D-17B was purely for inertial guidance.

Besides it was large and heavy and the Apollo mission needed three (minimum two) separate computers so this called for the development of a separate computer from scratch which won't expose any of the details of the nuclear missiles. They used the first integrated circuits in any computer.

As B-52 was very likely to fall into enemy hands it was unthinkable to put the latest technology on it. In case of nuclear exchange not many of them were expected to return anyway. Besides, it was expected to accumulate very many flight hours because they were loitering in the air over Canada 24/7/365 ready to set off for Russia at moment's notice. In this environment a mechanical system is easier to maintain by the existing personnel maintaining the other flight instruments.

The above speculation is not very well thought through or researched.
The Nike program of missiles in the 50's used analog computers of varying complexity in the same role as the D-17B. I only used it as an example because it was contemporary with the introduction of the M1.
The Apollo program had no use for something like the D-17B. It was a pretty crude and simple piece of electronics by the standard of the day that was primarily made for relative ease of manufacture and very high reliability, versus ease of use, speed, flexibility and precision.
Not using the best technology for the fear of it falling into the hands of the enemy is also doubtfull in this case. Transistorized analog computers where not bleeding edge tech in the mid 60's and the soviets had equivalents.
And you'd never hold back on using something that would give you a very real and tangible advantage in battle for the fear of it revealing secrets, even though it is a very real risk as witnessed with the Lorentz cipher in WW2.

[wkb]

I don't suppose you happen to know what alloy it is?

Aluminium or Magnesium.
Magnesium is kinda fire hazard in a war plane

That was my first guess and I came to the same conclusion, I doubt they'd use magnesium.

Plenty of WWII warplanes were made of Magnesium. It's not that easy to ignite.

(maybe they were desperate times and the other advantages of Magnesium outweighed the fact that it could burn)

It could be an alloy called Electron. Used in racing bikes for reasons of weight en strength.

[janoc]

Magnesium doesn't ignite just like that. Powdered magnesium or thin strips of it yes but a metal sheet no. It is not that much different from aluminium - that also burns really well when powdered but doesn't quite ignite normally.

[mikerj]

Well... both Aluminum and Magnesium are completely impossible to solder. The only thing that would make them solderable is some sort of plating for the solder to stick to.

Aluminium solders are readily available e.g. Multicore Alusol.

[basinstreetdesign]

BTW: the black cylindrical object that Dave could not identify at 22:00 looks to be a military style relay.  The coil voltage would be 26.5V and the contacts were rated for 5A.  The many connections on the bottom indicate that it may be 4PDT.  Many of them, then, had quite a few contacts and the military would have sealed them against the atmosphere to protect the contacts.  I have a few just like it.

[jh15]

I'll send you a length of tape (adhesive backed, by the way to get started).

I also have a sacrificial device i can un hermetically seal, and somewhere a bigg ass souldering iron. This may be my first Youtube:

look for it: Opening mil-spec hermetically sealed device or the like. Just a powerline monitor D'arsonval expaned meter in a can.

This is fun, I will learn youtube, links to dave, Fran, electric stuff, all those in our bubble. google plus links, twitter, etc.

Maybe you guys can look at previews before I publish it.

I miss Fran and Jeri Ellsworth new stuff, being forced to have commercials I guess.

P.S. I spin up my rocket gyro or whatever it is from  a Phase Linear 400 audio amp at 400cps. Fine for syncros too.

I can drive blocks with it spinnig and still have it precess on a friends table from inertia.

i used to be an audiophile, but not a phool, fun to watch those people.

[ErikI]

Could not resist.

[ShiftRegister]

Now this was pretty cool review. Hats off to whoever send this to Dave for tear down.

[broz]

That's what those synchros are for, getting input from the MD-1, and probably also operating the display. In searching around I've found some other systems where the mechanical bits were mounted directly behind the panel driving the altitude/azimuth display via direct mechanical linkage
 I'm thinking that springy bit that winds alternately between the two spools is some sort of integrator, or other math function. Might be useful to measure the sizes of the two spools with calipers and see what if any ratio exists between them - they are definitely not the same size. And in the time lapse you can see it winding up on one spool then reversing and going back to the other one.

I know old steam engines (such as those on early railroad locomotives) used a couple of spinning balls with a spring keeping them close together, and as the engine sped up, the centrifugal force compressed the spring which allowed the balls to rotate further apart which in turn closed a valve. This, if my recollection is correct, acted as some sort of regulator. Perhaps the springy bits here serve some similar functionality?

P.S. My apologies for the crudity of my explanation, have no idea what the technical terms are for everything, but hopefully it made some sort of sense!