vintage aviation gyroscope rebuild

Home Model Engine Machinist Forum

Help Support Home Model Engine Machinist Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

peterl95124

Well-Known Member
Joined
Feb 22, 2020
Messages
441
Reaction score
284
this is a WW-II vintage artificial horizon electrical gyroscope,
or more precisely just the innards, no instrument panel display
and no case, that I'm re-building, because in addition to engines
I like all things mechanical (clocks too!), and who doesn't find
gyroscopes to be mysterious and almost magical !

when I got it the rotor was so black I couldn't tell what metal it was,
and there was cosmoline everywhere (not even sure how/why it got there),
and rust in spite of the cosmoline because it wasn't where it should have been,
you're seeing it after a disassembly, clean up and oiling, and reassembly

along with not having the original housing the bearings for the outer
gimbals are missing, so making my own bearing races, and after that
some kind of bracket that will hold them and the gyro above a display base

finally I will be designing and building a 400-Hz 3-phase power supply
as that's what this one almost certainly requires (the motor is a Delta
connected 3-phase without doubt, and 400-Hz is pretty much standard
for avionics both military and civilian, but voltage is still totally unknown,
commonly used in avionics are 12, 24, 48, and 115, Argh!)
 

Attachments

  • IMG_0413.jpg
    IMG_0413.jpg
    564.8 KB · Views: 11
Last edited:
That is a nice gyro motor.

The 400Hz is not practical for general power distribution due to the excessive voltage drop, but it works well for an airplane, since it makes the motors very small for the same horsepower as 60Hz.

I think some of the original motor power systems where 30Hz, and 50/60 Hz became a compromise, I believe to reduce light bulb flicker.

Any idea what rpm?

Brushed or brushless?

.
this is a brushless motor, and its an inside out motor, the stator with coil windings is on the inside, and the rotor is on the outside, so that most of the mass of the rotor is at the largest possible radius, giving the rotor the largest possible rotational inertia which is what gives it its gyroscopic stability

as near as I can tell there's no clear way to calculate the maximum safe speed of this rotor, there's a relevant formula for the hoop-stress at the hub bore of a uniform disk (the hub is where a rotor always breaks first, EG look at a gas or steam turbine disk and you'll see that the hub is reinforced relative to the thin disk leading out to the rim), this rotor is a heavy tube with a light disk at one end and a reinforced hub at the center of the disk, not a geometry for which there are any direct formulas.

further complication is that I don't know if the speed for this type of motor is voltage or frequency dependent, its going to be and adventure :) !!!
 

Attachments

  • IMG_0415.jpg
    IMG_0415.jpg
    560.3 KB · Views: 0
Last edited:
this is a WW-II vintage artificial horizon electrical gyroscope,
or more precisely just the innards, no instrument panel display
and no case, that I'm re-building, because in addition to engines
I like all things mechanical (clocks too!), and who doesn't find
gyroscopes to be mysterious and almost magical !
.......................

Peter,
What a wonderful find of a piece of mechanical history. Is this indeed a Sperry instrument? The RPM might be as high as 20,000 rpm, based on the small size. Too bad that the outer housing is missing.

Peter, good luck on your project.
Lloyd

edit- unrelated comments removed (twice).
;)
 
Last edited:
This clip I found indicates 115 volts, AC, 400 Hz, or lower DC voltages via an inverter, so for this model, it would appear that it runs a 115 volts AC, 400 Hz only, with DC voltages being converted to 115V/400 Hz by an inverter if you want to use DC to power the gyro.

No mention of operating rpm, but it does mention that a higher rpm gyro functions better than a lower rpm gyro, which is what I suspected. Same applies to the early steam engine governors such as the Porter.

View attachment 154838

what makes you think this is a Sperry gyro, there are no markings on it what-so-ever, I'm not up on the history and don't know how much competition Sperry had if any, and even if it is a Sperry why would they all (civilian and military) be 115V ? The one I have is physically limited to about +/- 70 or 80 degrees pitch since it uses hair-spring rather than slip-ring connections, and since I don't have the case can't tell about connections through the roll gimbal, but why would they be different. Don't know what that tells, if anything, about its manufacturer.

I used the formula in Machinery's Handbook (can also find the same formula on the internet) for stress on a rotating disk-with-bore, or equivalently a tube, and assumed the rotor is made from a 60/40 brass alloy of ~55,000 psi yield strength, and come up with ~ 70,000 RPM (yield) burst speed, so I probably won't run it up past 10,000 maybe 15,000 !!! I'll first see what happens at 12V, then 24V, etc,

I've spun it up on compressed air, and just love the whirring sound it makes as it ever so slowly winds down, to me its every bit as endearing as the tick of a mechanical clock :) !!!


PS, my preference is to have a blog here on HMEM that stays on the topic of this rebuild and doesn't wander off into tangential topics like long distance electrical transmission lines, etc, etc, I've seen all too many blogs here on HMEM go bonkers divergent, and while there's a need for people to have a place to talk about what ever's on their mind I prefer that my blogs aren't like that. are you OK with that ?
 
Last edited:
FYI,

I googled aviation gyroscopes, hoping to find more information. I did find several vintage ones for sale for low bucks, in terrrible condition and probably not functional. Possibly worth trying to get one to have the case and the display and something else to play with.

I am interested in what you do with this gyro as I also like old mechanical gismos.

--ShopShoe
 
PS, my preference is to have a blog here on HMEM that stays on the topic of this rebuild and doesn't wander off into tangential topics like long distance electrical transmission lines, etc, etc, I've seen all too many blogs here on HMEM go bonkers divergent, and while there's a need for people to have a place to talk about what ever's on their mind I prefer that my blogs aren't like that. are you OK with that ?
All cleaned up now; I will get the mods to delete my blank posts.
.
Done !
Have fun ;)
 
A caution - Beryllium was often used for Gyro flywheels. Beryllium is used in aerospace applications as it is stronger than steel and lighter than Aluminium, electrically conductive and has no fatigue mechanism (inside its elastic limits) so it's good for conductive springs and such.

However Beryllium Oxide is extremely toxic - some people develop ulcerations just from touching the stuff.

That's why you can no longer get materials like Beryllium-Copper - which used to be the goto material for welding tips and projection welding tooling etc.

I used to work with Beryllium-Copper and it never caused me any problems but if you read the safety precautions you might think it as toxic as Plutonium.

https://www.osha.gov/beryllium

That said Beryllium-Oxide ceramic (sometimes used for microwave and RF insulators) is as toxic as cyanide. So if you ever strip some HF electronic device and you find blue coloured ceramic washers - be very careful.

Just a heads up - that flywheel might be Beryllium or any one of the weird alloys they use in aerospace - like Beryllium-Tungsten.

Regards, Ken I
 
Last edited:
A caution - Beryllium was often used for Gyro flywheels. Beryllium is used in aerospace applications as it is stronger than steel and lighter than Aluminium, electrically conductive and has no fatigue mechanism (inside its elastic limits) so it's good for conductive springs and such.

However Beryllium Oxide is extremely toxic - some people develop ulcerations just from touching the stuff.

That's why you can no longer get materials like Beryllium-Copper - which used to be the goto material for welding tips and projection welding tooling etc.

I used to work with Beryllium-Copper and it never caused me any problems but if you read the safety precautions you might think it as toxic as Plutonium.

https://www.osha.gov/beryllium

That said Beryllium-Oxide ceramic (sometimes used for microwave and RF insulators) is as toxic as cyanide. So if you ever strip some HF electronic device and you find blue coloured ceramic washers - be very careful.

Just a heads up - that flywheel might be Beryllium or any one of the weird alloys they use in aerospace - like Beryllium-Tungsten.

Regards, Ken I
could you please retract/delete this, it is yet another off-topic post that I'd prefer not to have cluttering up this blog (and while you mean well, its also factually incorrect in a number of ways, and no I don't want de-bunking this to be part of the blog either)
 
Studying the picture in the first post, the 2 spindles for the outer gimbal do have the characteristic 60 degree(?) included angle bearing surfaces (inner races) that was a feature on the earlier vacuum driven Sperry designed horizon indicator. Might this be a newer electrical version of the device? The 60 degree angle is quite aggressive for angular contact bearings and makes preload adjustments very touchy. That helps to explain the very large preload adjusting nut visible on the inner gimbal trunnion.
 
Studying the picture in the first post, the 2 spindles for the outer gimbal do have the characteristic 60 degree(?) included angle bearing surfaces (inner races) that was a feature on the earlier vacuum driven Sperry designed horizon indicator. Might this be a newer electrical version of the device? The 60 degree angle is quite aggressive for angular contact bearings and makes preload adjustments very touchy. That helps to explain the very large preload adjusting nut visible on the inner gimbal trunnion.
yes, for the gimbals the cones are straight and I measured the angle to be about 60-deg and the reason they work is that the cups have bearing grooves in them, the load on them is almost all radial so the narrow cones are OK, for the rotor both the cups and the cones have a "bearing groove" (and they're hardened and mirror polished) but its near impossible to tell where along the groove curve is the contact point and what the angle is at the contact point, the load on the rotor bearings is almost all axial so I'm guessing the contact point is near the base of the cone / groove where the angle is more supportive of an axial load. the gimbal bearings have 40-TPI threads and the rotor bearings have 56-TPI (they "appear" to be even finer, but that's because of the 5/8" diameter). one of the gimbal cones has a tiny central through hole, like you see in vacuum powered gyros, so I'm guessing some interchangeable parts.
I think I really lucked out in that while there was lots of rust on the gimbal cones (which I have polished out without damaging their geometry AFAICT), there was no rust on the rotor cones which would have been impossible to polish out without altering the geometry and probably totally destroying them.
 
Peter, I am intrigued by this project because I worked at a Sperry Marine facility for 25 years. It was all shipboard applications, lots of gyro compasses, and inertial navigators, but no avionics. I don't know if you are looking for a PN for this unit, but you might try this. It is a decent possibility:
MIL-I-5133, Type J8, PN 14602. I left off all the dash and rev numbers and letters. It appears to be the electrical successor to the AN-5736 vacuum powered one. The J8 does have a single 3 pin electrical connector that might be compatible with the three 3-phase power wires on your unit. It does not appear to have an additional signal output, so it would be a visual indicator only.
I agree with your earlier assessment of the unique sound of these units taking forever to coast down.
 
could you please retract/delete this, it is yet another off-topic post that I'd prefer not to have cluttering up this blog (and while you mean well, its also factually incorrect in a number of ways, and no I don't want de-bunking this to be part of the blog either)
Sorry but I was just curious as to why. I will not be cluttering up your blog
with any more reply's. You know what they say about curiosity and cats. May not kill ya, but it'll get ya inta a heap a trouble around here. I did not know that a vintage aviation gyroscope was a type of Engine, learn somthing new everyday.😢
 
Last edited:
Why is beryllium used in gyroscopes?
In gyroscopes, where heat generation is substantial, beryllium ensures even heat distribution, reducing internal stress and enhancing overall precision.

Gyroscope sphere.
please take a look at the pictures of my gyroscope, please take a look at the pictures of the "gyroscope sphere" please note that these have nothing in common physically, and that the sphere didn't arrive until the cold war long after my gyroscope, and that they were used for ICBM inertial guidance and extra-long-range bomber inertial guidance. please delete your post, you're not adding anything to this "traditional aviation gyroscope", the kind that are still being made to this day without beryllium, because only the military with is no-holds-barred, no-budgets-barred approach uses it, I know you guys mean well and are trying to help but you are not, its tangential / off topic and distracting. If you insist on posting about beryllium perhaps start your own blog titled "beryllium gyroscopes" ?
 
Last edited:
A caution - Beryllium was often used for Gyro flywheels. Beryllium is used in aerospace applications as it is stronger than steel and lighter than Aluminium, electrically conductive and has no fatigue mechanism (inside its elastic limits) so it's good for conductive springs and such.

However Beryllium Oxide is extremely toxic - some people develop ulcerations just from touching the stuff.

That's why you can no longer get materials like Beryllium-Copper - which used to be the goto material for welding tips and projection welding tooling etc.

I used to work with Beryllium-Copper and it never caused me any problems but if you read the safety precautions you might think it as toxic as Plutonium.

https://www.osha.gov/beryllium

That said Beryllium-Oxide ceramic (sometimes used for microwave and RF insulators) is as toxic as cyanide. So if you ever strip some HF electronic device and you find blue coloured ceramic washers - be very careful.

Just a heads up - that flywheel might be Beryllium or any one of the weird alloys they use in aerospace - like Beryllium-Tungsten.

Regards, Ken I
in my mind the beryllium question comes down to this, are aviation gyro rotors made from C172 Beryllium Copper or from a more common brass alloy. my back of the envelope calculations say that for the dimensions of my rotor if it is C280 (60/40 brass) then its yield strength max RPM is around 70,000, and if it is C172 (2% Be Copper) then more like 120,000. and those numbers are max, actual numbers with safety factors would be much less. and the most obvious question is could the bearings actually sustain the higher RPM that C172 would make possible, I can't answer that directly, but, having made a working KJ-66 style model turbojet engine with ceramic ball angular contact bearings, I seriously doubt it, those bearings (ceramic ball or steel ball) at those speeds require continuous lubrication because no lube stays in place at those speeds, and these aviation gyros are sealed and have no lubrication system. In my humble opinion (YMMV, yada, yada, yada) there's no reason for anyone to have used C172.

And finally, C172 with only 2% beryllium is generally recognized as safe to machine, that's one reason its so readily available, so it really doesn't matter what its made of.

So please, delete the unnecessary comment about the dangers of beryllium, there's no way an aviation gyroscope has any pure beryllium, and its unlikely you'll be able to get your hands on a real beryllium gyroscope, they were for nuclear warhead ICBM inertial guidance and nuclear long range bomber inertial guidance, and like all things nuclear you probably can't even see one without national security clearance (yes, I've seen things on eBay claiming to be beryllium from a gyroscope, take those with a grain of salt, and also realize that even if they are they did not come from an aviation gyroscope).
Talking about the dangers of beryllium in the context of aviation gyroscopes isn't any more relevant than bringing up the dangers of the leaded paint that I don't have, or the cadmium bearing silver-brazing wire that I don't have, or the thoriated-tungsten TIG electrodes that I don't have, etc, etc, etc. Yes, you meant well, but in light of how irrelevant it is, perhaps we can delete it and move on ? please feel free to start your own blog / thread maybe with the topic "dangerous metals in the machine shop" or some such ?
 
Last edited:
Sorry but I was just curious as to why. I will not be cluttering up your blog
with any more reply's. You know what they say about curiosity and cats. May not kill ya, but it'll get ya inta a heap a trouble around here. I did not know that a vintage aviation gyroscope was a type of Engine, learn somthing new everyday.😢
not only are gyroscopes engines, but so are mechanical clocks, so are cam grinders, so are drill and mill sharpeners, so are gear cutters and gear hobbers, so are EDMs, so are home built CNCs, etc, etc, etc, enjoy :) !!!
 

Latest posts

Back
Top