Arri 35 Gyro Assisted Rigs

Here are some examples of different ways to use Kenyon gyros with larger cameras. I would recommend that you study all the material in this section and in Inertial Camera Stabilization before building anything. There may be easier solutions. Building simple prototypes are a great tool for discovering, balance, clearance and mounting problems. Consider making mock cameras and gyros of the same weight, mounting thread and CG positions for prototyping.

Also consider using the lightest cameras available such as an Aaton or a modified II C. The gyro noise limits sound recording close to camera. Register pins are not relevant unless shooting plates. The first two examples below of combined camera, zoom lens, dovetail and gyros weight about 35 lbs. "More professional" looking rigs could include small U-joints, rods, cables instead of the nylon cords, and of course anodized parts. But consider that the additional weight of U-joints defeats the stabilization effect of the gyros.

I have made no provision here for weight transfer as the film travels in the magazines. This can be manual or automatic as the camera rolls with some innovation. The weight should travel in line with the magazine spindles. The weight transfer when the zoom position is changed seems too small to be a problem. You will have to work out cable problems to camera, video assist and gyros. I like head mounted viewfinders, but viewfinders can be mounted on the camera system. Just keep the weight down to a minimum.

The first two configurations can be supported from below or above with almost the same hardware.

1. Arri 35 with Zoom Supported from Below

I used these custom dovetails for years before Arri went to matte box rods. It is helpful if you can provide some CG adjustment right at the CG where adjusting is most sensitive. You should also provide fine tuning CG adjustment at each gyro. In this case the gyros are located low so that the combined CG and support point is just below the camera lens. There is no zoom motor control on this prototype. We do moving tests with equally weighted mock-ups and a consumer camcorder. The unit is controlled with 2 hands in line on the CG axis. A zoom control would replace the round handle on the right side. Note the loose safety cord from above. The motor shown is home made and we have used for years. It is constant speed from 1/4 FPS to 50 FPS and runs off 30 volts. Today there are many good after-market motors made for the Arri II models. We made our own when there were only the three marginal motors made by Arri.

 

A spring and a shaft in a vertical linear bearing, damp the vertical motions. A fiberglass tent pole damps the horizontal motions with a spike in a support socket under the lens on the camera system.

2.Arri 35 with Zoom and Support from Above

The same hardware as the above example can be used for hanging by rubber tubing, springs or bunji from above. Holes just big enough for the nylon cord are drilled in line with the CG axis and the cords are attached to the trapeze bar above. Tie secure knots in the nylon cord and check periodically for wear. Make smooth edges on the holes to avoid fraying the cord. The CG is in the same place as the above rig. The trapeze transfers the CG from the holes back to the center. Note the loose safety strap to above.

3. Other Variations

You can build versions with the gyros on each side of the camera with a trapeze from above. Make sure that you follow all the "Gyro Basics" as close as you can. The transfer of weight of the film as it is used, has been solved by the helicopter ball mount. For short shots, a sliding weight would do just fine if you adjust it between takes.

For standard matte box rod systems, the support socket for the tent pole spike can be between and above the rods and just below the lens which is close enough to the camera / lens CG.

These are 1/2" EMT elbows with sleeves for the 15mm matte box rods.

4. Arri with Hard Lens Hung from Above

Here the combined camera, rig and gyros weights about 25 lbs. The gyros are close and the unit is compact for a (Body Cam) backpack support. The GC is adjustable up and down with the 3/8" bolt holding the nylon cord. The gyros can move side to side and back and forth for dynamic balancing. Here the gyros are the factory recommended, 1/2 the weight of the camera, and are very effective. The mannequin is handy for adjusting everything before putting the pack on an operator.


5. Arri with Hard Lens Supported from Below

This is a slight modification of the above rig. The gyros are mounted on the bottom of the plate and the CG is now in the middle of the 1/4" plate. A detent socket is drilled with a 1/2" drill bit almost all the way through the plate to make a socket for a spike from below. A larger socket is recommended so the spike can't jump out of the socket during a violent move by the vehicle.



6. Arri with Zoom Hung from Above with Gyros at Top

I built an Arri with zoom prototype similar to the Betacam model with the gyros above the lens. The saddle under the camera allows attachment to the CG above the base of the camera. No matter where the gyros are attached, get them close to the mass of the camera. The CG often ends up somewhere in the middle of the camera body. Putting the gyros forward and high, places the CG closer to the viewfinder. When the camera pans and tilts the operator's eye will not have to move much. This is an issue especially when the operator is sitting behind the camera. Refer to Gyro Betacam Type Rig.

The "trapeze" transfers the CG from inside the camera body to above the camera. It is attached to an above support and isolation system, in this case rubber tubing. There is no zoom control shown here and should be for the right hand. It should be centered in line with the CG of the system. The trapeze bar above should be balanced and drilled for the horizontal CG ONLY AFTER all elements are attached to the camera system.

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