Seeking Information on a WW II Era Westinghouse Gyro

[bob012345]

I’m helping a friend search for information on a Westinghouse gyro from the WW II era and beyond. He has the gyro but is looking for information on the power supply to recreate it since he doesn’t have and can’t seem to find it. There also is no documentation with it. The only details from the unit is that it takes 26V, 400 Hz 3-phase power and spins at 12,000 rpm. It might be model 860 or 5318, it hard to tell what the model number is. I’ve tried numerous Google searches but no firm information so far.

My question is if anyone knows about such systems or knows of a source that would. Thanks.

 

[jedishrfu]

Take some pictures and send them to the various ww2 museums. A curator might be able to help identify it.

Check with Westinghouse, they may have a corporate history office that can track down the plans.

Are there any markings as to where it was built. You could check that site.

 

[jedishrfu]

Is it a gyro for a ship or sub or aircraft?

 

[russ_watters]

He has most of the power info already. I'm not an EE but can't he find and connect a low wattage power supply that's 26V/400hz/3ph?

 

[jedishrfu]

This markdown file might help

# Westinghouse Model 860 Gyro (WWII Era) – Comprehensive Overview

## Historical Background and Development
The **Westinghouse Model 860 gyroscopic stabilizer** was a pioneering WWII-era device designed to keep weapons (especially tank guns) steady on the move. It emerged from a U.S. Ordnance Department request (circa 1939) for a method to stabilize tank guns so tanks could fire accurately while driving over rough terrain. Westinghouse Electric’s research engineer **Clinton R. Hanna** led the development. Early prototypes in 1941 used two gyroscopes, but Hanna soon perfected a single-gyro solution dubbed the “*anticipating gyro*,” which could sense and correct for motion *before* the gun shifted significantly.

By 1942 the U.S. Army was testing the stabilizer under combat conditions, and it proved it could dramatically increase hit probabilities. Hanna’s invention was adopted for production in American tanks (first fielded in the M3/M5 Stuart light tanks and then standard on all M4 Sherman medium tanks). In 1942, Hanna received a Presidential Citation for this work. By 1944–45, the gyro stabilizer was installed in virtually all newly-produced U.S. tanks, and units were even supplied to Allies (Britain and the USSR) via Lend-Lease. This wartime innovation gave U.S. armor a notable advantage – allowing tanks to aim faster and more accurately when moving – a capability German tanks lacked during WWII.

After WWII, Westinghouse and Hanna continued to refine gyro stabilizers, and the concept found potential peacetime applications (Hanna speculated a few horsepower of gyroscopic stabilization could steady railroad coaches or automobiles for a smoother ride).

## Technical Specifications of the Model 860 Gyro

### Design and Components

The Model 860 gyro stabilizer was an electromechanical system comprising four main parts:
1. **Gyroscopic Unit** – The gyro rotor and gimbal assembly served as a vertical reference.
2. **Silverstat Regulator** – An electric feedback regulator.
3. **Hydraulic System** – A pump and dual electro-magnetic valve system.
4. **Actuator** – A hydraulic cylinder mounted to the gun.

The **gyro rotor** was a dynamically balanced flywheel driven by an electric motor from the tank’s electrical system. The gyro assembly was compact enough to mount on the gun breech and was housed in a rugged enclosure to withstand vibrations.

### Power and Electrical Specs
- **Voltage:** 24V DC (Tank's standard electrical system)
- **Frequency:** 400 Hz
- **Gyro Rotor Speed:** ~12,500–16,000 RPM (Optimal: ~14,000 RPM)
- **Power Source:** Tank’s batteries and generator

### Gyro Performance
- **Pitch Correction Range:** ±2.5° at ~1.5 Hz
- **Deflection Error:** ≤ ±¼°
- **Response Time:** Near-instantaneous
- **Hydraulic Pressure:** A few hundred PSI
- **Gun Movement Force:** ~200 lbs at the breech

The Model 860 was a **single-axis stabilizer** (vertical plane only) with fast electro-hydraulic controls.

## Applications During WWII

### **Tank Gun Stabilization**
The primary application was in **tank gun stabilizers**, first implemented in **M3/M5 Stuart light tanks** and then widely in the **M4 Sherman medium tank**. The stabilizer kept the main gun’s elevation steady as the tank moved, enabling more accurate fire on the move.

- **Hit Probability:** ~70% at 15 mph (vs. ~1% for unstabilized tanks)
- **Usage by Allies:** Supplied to British and Soviet forces
- **German Awareness:** Attempted but failed to replicate

### **Other WWII Uses**
- **Aircraft Camera & Gunsight Stabilization**
- **Naval Weapons (Limited experimental applications)**
- **Field Artillery (Unsuccessful tests on stabilizing towed guns)**

## How the Gyro Stabilizer Functions

### **Operating Principle**
The Model 860 gyro stabilizer functioned as a **feedback control system**:
1. The **gyro remained fixed in space** while the tank moved.
2. Any tilt caused the **gyro to precess**, moving the **Silverstat regulator contacts**.
3. The Silverstat altered current to **magnetic valves**, controlling oil flow.
4. Hydraulic pressure moved a **cylinder actuator**, correcting the gun’s elevation.

This kept the gun **nearly steady despite bumps and dips**.

## Maintenance and Repair Guidelines

### **Regular Checks:**
- **Pre-Mission:** Check gyro startup, hydraulic fluid, wiring integrity.
- **Gun Balance:** Proper trunnion counterbalance ensures smooth function.
- **Silverstat Calibration:** Leaf contacts should be adjusted to avoid drift.
- **Hydraulic System:** Prevent air bubbles, clean oil lines regularly.

### **Common Repairs:**
- **Electrical Issues:** Fuse checks, battery charge maintenance.
- **Hydraulic Failures:** Filter cleaning, valve replacements.
- **Gyro Bearings:** Periodic lubrication and inspection.

## Legacy and Modern Uses
The Model 860 gyro stabilizer directly influenced **post-war tank designs**, leading to:
- **Cold War-era full-stabilization systems (M47, M48 Patton, etc.)**
- **Modern MBTs (Abrams, Leopard, etc.) with advanced digital gyrostabilization**
- **Civilian Applications:**
  - **Camera Stabilization (Gimbals, Steadycams)**
  - **Anti-roll & Active Suspension in Vehicles**
  - **Inertial Navigation for Aircraft & Spacecraft**

## References and Sources
- [Sherman Tank Site – Stabilizer](https://www.theshermantank.com/)
- [WWII Ordnance Manual – TM 9-745 (M4A3 Sherman)](https://archive.org/details/TM9-745)
- [U.S. Army Field Manual FM 17-12 (1944)](https://www.ibiblio.org/hyperwar/USA/ref/FM/PDFs/FM17-12.pdf)
- [Clinton R. Hanna – Engineer & Patent Holder](https://ethw.org/Clinton_R._Hanna)
- [Popular Science (Sept 1944) – “Why Our Tanks Can Score Hits on the Run”](https://www.popularmechanics.com/)

This WWII Westinghouse gyro stabilizer was a **pioneering military innovation**, significantly improving tank fire control and leaving a lasting impact on modern stabilization technologies.

 

[Baluncore]

He has the gyro but is looking for information on the power supply to recreate it since he doesn’t have and can’t seem to find it.

If all you need is a power supply, then a Variable Frequency Drive, VFD, for 3PH motor speed control can be programmed to produce 24V at 400 Hz, 3PH. That will cost less than $100.

 

[bob012345]

Is it a gyro for a ship or sub or aircraft?

He thinks aircraft.

 

[bob012345]

He has most of the power info already. I'm not an EE but can't he find and connect a low wattage power supply that's 26V/400hz/3ph?

I think he’s worried that the phase might need precision control.

 

[bob012345]

Thanks. I found this small bit of information from the Purdue Engineer feb ‘45.

A. C. Current For Gyroscopes

Westinghouse Gyroscopic devices have had a large place in the war from its start. Small panel-mounted instruments have used air-operated gyros or a-c gyros driven from inverters, but most of the large gyros used in flight-control devices, bombsights, and similar computing devices have employed d-c motor-driven gyros. At the high... speeds at which gyros operate (7500 to 20,000 rpm) brush friction can cause precession errors and brush dust is apt to foul the bearings. Direct-current gyros are usually series-wound because of the high inertia wheels and long starting time (sometimes onehalf hour to reach full speed) and as a result the speed increases very considerably as air friction decreases at high altitudes. For these reasons, a program is underway to develop a-c gyros for the more important applications. Largest of the a-c gyros is one with a rotor five inches in diameter operating at 12,000 rpm from a 400-cycle, threephase supply. This is a vital part of an automatic pilot. The angular momentum of this wheel, in the units used by gyro instrument engineers, is 83,500,000 gram-centi-meters squared-radians per second. Smallest of the gyros is one but 2-3/16 inches in diameter, which replaces an air-driven gyro in a computing sight. This gyro produces 38,800 gram-centimeters squared-radians per second. Although "inside out' 'squirrel cage motors are used for some of these gyros, most of them are "inside out" hysteresis motors. The usual rotor is part of the flywheel and rotates outside of the air gap, the polyphase stator being wound inside of the air gap. Hysteresis motors require no squirrel cage, but instead employ discs of permanent-magnet steel for the rotor. Magnetic hysteresis caused by the rotating field causes the rotor to accelerate and finally fall into synchronism. The current drain changes very little from locked to synchronous operation, a considerable advantage when these gyros are driven from small inverters

 

[berkeman]

I think he’s worried that the phase might need precision control.

Sorry, I don't understand what that means. 3P/400Hz seems pretty straightforward to me. I don't know the cheapest way to produce it, but the suggestion from @Baluncore seems good:

If all you need is a power supply, then a Variable Frequency Drive, VFD, for 3PH motor speed control can be programmed to produce 24V at 400 Hz, 3PH. That will cost less than $100.

 

[bob012345]

Sorry, I don't understand what that means. 3P/400Hz seems pretty straightforward to me. I don't know the cheapest way to produce it, but the suggestion from @Baluncore seems good:

Ok, I’ll suggest that. Thanks.

 

[jedishrfu]

He thinks aircraft.

From the writeup I posted it's for a tank to stabilize a tank gun as the tank is bouncing up and down, going into ditches climbing small hills the gun will remain pointed at the same elevation.

 

[bob012345]

From the writeup I posted it's for a tank to stabilize a tank gun as the tank is bouncing up and down, going into ditches climbing small hills the gun will remain at the same elevation.

I asked and he said he thinks it’s from a plane because when he got it he was told it came from a module called a ‘bomb sight computer’.

 

[berkeman]

he was told it came from a module called a ‘bomb sight computer’.

That could still be the tank application that jedi describes...

 

[bob012345]

That could still be the tank application that jedi describes...

It could. Regardless of where it came from it would be nice to find a Westinghouse patent that described the power supply circuitry for that model. I’m still looking for that.

 

[Rive]

power supply circuitry

Honestly, I really doubt that you would find anything else but a mechanically controlled synchronous generator.

Ps.: but with more info and with pictures this would be a lot easier. By now I could even dig up a maintenance manual for the Sherman tanks ...

source

 

[Rive]

he’s worried that the phase might need precision control.

Well, what I've found so far the 'power supply' of the era likely was just a moderately regulated dynamotor.
Something like these (1, 2).
A proper VFD is a very safe bet to make that thing work.

 

[bob012345]

FYI, here is a photo.

 

[Rive]

No hits.

The lack of anything housing-related tells me that it was part of an encased bigger unit, and the 3ph power (instead of a plain DC motor with graphite brushes) tells me this was something sensitive => could be a part of a mechanical computer, maybe a bombsight, indeed.

I would try my luck here. Maybe it can be spotted on some images. But it'll be a tedious work.
Maybe they can even help identifying the thing?
Pretty decent collection and images, by the way.

 

[Klystron]

It could. Regardless of where it came from it would be nice to find a Westinghouse patent that described the power supply circuitry for that model. I’m still looking for that.

Not specifically gyros or tanks but I had tons of experience refurbishing, upgrading and operating A(rmy) A(ir) F(orce) N(avy) AAF/N electronic equipment originally designed during 1940s and 1950s. Almost every system requiring high frequency alternating-current ran on standard 400 hertz. 3-phase portable generators.

Standardization was ubiquitos, among the services and across varied mission requirments. Engineers really applied Modular Hypothesis, now modular and group theory. Army tank cannon stabilizer, radar-controlled firecontrol system, or airborne autopilot units might all use interchangeable units powered by very similar generators.

Remember most power supplies, voltage divider and regulator circuitry, etc. originally used nearly identical vacuum tubes and associated electronics. Westinghouse equipment was highly regarded for reliablility, ruggedness and interchangeability.

Over the years vacuum tube devices were replaced with integrated circuits (IC) and other solid-state technology but end units keep chugging along. Be careful but the basic 400 hz 3-phase supplies suggested in above posts should work. Be extra careful to observe safe electrical handling practices particularly around military hardware.

Most of the original documentation on military hardware was undoubtedly classified. Later digitization of technical manuals (TOs) was spotty and very difficult to document as printing was NOT as standardized as the actual equipment. Schematics were printed on long fold-out sheets across many pages. I wrote some papers on this topic, also classified, during the Cold War.

 

[Theo104]

Hi All:
I think you are talking about the same gyroscope that is in my possesion. I think it was used in an aircraft.

 

[Theo104]

 

[bob012345]

Hi All:
I think you are talking about the same gyroscope that is in my possesion. I think it was used in an aircraft.

Thanks. Do you have information on the power source?

 

[jedishrfu]

It says on the label 26v 3 phase 400Hz power.

So you need an avionics power supply that matches the label which is likely very hard to get. The ones I saw were single phase 115 watts.

 

[Baluncore]

That gyro appears to have very little angular compliance. I would guess that it had to be for gun stabilisation on a moving land vehicle, such as a tank or SPG. I cannot see how it could possibly function on an aircraft.

 

[Klystron]

That gyro appears to have very little angular compliance. I would guess that it had to be for gun stabilisation on a moving land vehicle, such as a tank or SPG. I cannot see how it could possibly function on an aircraft.

Possibly as a visual stabilization device for a bombsight on a US bomber. Pilot cedes flight control to the bombardier. Gyros help compensate for minor vertical lurches caused by flak bursts and COG changes as heavy bombs fall out of the bomb bays. Just opening the bomb bay doors might induce enough error that the bombardier could 'lose the picture' without gyroscopic compensation.

As @Baluncore mentioned previously this model likely made small corrections in one direction but could be mounted in pairs or triplets. I see @jedishrfu covered a wide range of applications in post #5 back in March that included aircraft.

Bombers and fighters also carried gyro-stabilized guns and gun cameras, the latter of vital importance to assess effectiveness.


[edit 20251114: Correction. I meant to remove final clause. The "doubles and triples" experiments I witnessed occurred decades after WWII and not on aircraft. Westinghouse gyros, though.]

 

[Baluncore]

As @Baluncore mentioned previously this model likely made small corrections in one direction but could be mounted in pairs or triplets.

Where did I mention that?

Gyro based gun stabilisers during WW2, only stabilised the vertical axis, pairs or triples were never used. The gun stabiliser in the Sherman tank had vertical axis only, for repeatable elevation, and the gyro was made by Westinghouse.

The example shown in this thread has a vertical axis only, with less than about ±30° of movement compliance. It was designed to be attached to a surface that remained close to horizontal.

The gyros used in aircraft were always mounted in free gimbals, because aircraft are subjected to much greater variations of orientation than are tanks. The Norden bombsight was stabilised with a vertical axis gyro only, mounted in full gimbals.

The gyro shown in this thread is clearly not from an aircraft, it is almost certainly from a tank or a self-propelled gun.

 

[Baluncore]

There is a diagram of the 1943-4 Westinghouse gyro-stabilizer, as used in tanks, shown here. https://natlib.govt.nz/records/22339506
It appears to be significantly different to the example in this thread.

 

[bob012345]

It says on the label 26v 3 phase 400Hz power.

So you need an avionics power supply that matches the label which is likely very hard to get. The ones I saw were single phase 115 watts.

We wish to find the actual design to replicate it accurately.

 

[Baluncore]

We wish to find the actual design to replicate it accurately.

The power supply would be determined by the vehicle, and could be a ;
1. rotary converter of DC, vehicle battery to 3PH AC.
2. vibrator based 3PH inverter supply.
3. 3PH alternator on an engine.
My guess is that you must identify the application before you can identify the supply.