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The Crown Stacker M-Series, manufactured by the Crown Corporation (www.crown.com), are walk-behind power jack/ lifts.

Physical Description:

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That illustrates the basic profile of the device. The "T" shape coming off at an angle on the left is a metal and rubber device called the "control handle". The diagonal portion that the control handle emerges from is the "main panel". The base of the machine is stabilized by the "outer straddle forks". The "inner forks" actually do the lifting.

The stackers stand from 5 feet, 6 inches in the "down" position to 12 feet, 2 inches in the fully extended "up" position.

Capabilities:

Payload Capacity: 1500-2000 lbs.
Maximum lift height- 130 inches.
Fork length- 30-48 inches.

The M-series is capable of maneuvering in relatively tight spaces- the turning radius is negligible- and the real limiting factor to maneuverability is its 50 inch width. The quoted weight capacity is something of a suggestion- I've used older and newer models from the M-series, and the older ones will loudly complain at loads at 800-1000 lbs, while the newer ones handle pallets at or near 1500 lbs quietly.

Operation:

Safety

The first and most important thing to learn about operating any heavy piece of equipment like this is an awareness of safety features. The M-series all have four main safety features- a power disconnect lever, a "safety button", the control handle, and "turtle mode".

The red power disconnect lever disables all power to the machine of any kind. If the power disconnect lever is thrown, it will not drive, none of the LEDs on the main panel will light, and (importantly) the battery cannot be recharged. The power disconnect lever can be used to stop the machine if it is not under control, but it is not the preferred line of defense in an unsafe situation- it is located on the main panel of the machine, which makes it more difficult to reach than the control handle.

The "safety button" is a red button on the control handle of the machine itself that covers about a third of the width of said handle. It is supposed to reverse the motion of the machine if it comes into contact with you. I would never trust my life to this button- if the machine is already touching me, there's no telling whether the machine will be able to reverse itself quickly enough before it crushes me.

The most important safety feature of the M-series is the control handle. When you grip the handle of the machine, it will only drive if the handle is within a certain range of angles to the horizontal. If the handle is outside that range of angles, the machine automatically applies brakes. This is very easy to control- you've already got your hands on the handle, so to stop the machine, just raise the handle outside of its operating range. Additionally, if you let go of the handle, it will automatically swing upwards to the vertical position and thus engage the brakes.

When you are first learning to use the stacker, you will probably want to engage "turtle mode". There is a toggle switch on the main panel marked on one side with a turtle and on the other with a rabbit. With the switch set to "turtle", the top speed of the machine is reduced.

Driving

Provided the control handle is held at an angle of around 45 degrees or less to the horizontal, you can drive the machine forwards by rotating the rubber grips on the control handle forwards as if you were driving a motorcycle. By rotating the rubber grips in the other direction, you can drive in reverse. The rubber grips themselves will click as you rotate them in either direction, and those discrete clicks determine the speed of motion- 1 click is slow, 3 clicks is fast. Oddly, the behavior of 2 clicks is erratic (maybe my machines are too old, but sometimes 2 clicks will be slower than 1!)

To steer, rotate the entire control handle about the vertical axis. To turn left, rotate the control handle clockwise. To turn right, rotate the control handle counterclockwise. This might seem a bit counterintuitive at first, but it really is exactly as if you were pushing a pallet jack.

When driving, it is sufficient to manipulate the rubber grips with one hand. When driving in reverse, it is preferred to use only one hand, so you can keep your body to the side, out of the path of the backwards-moving machine. If that kind of body position seems awkward, remember that you don't need to exercise force to get the machine to drive (you just need to be able to click the handle).

To lift or lower the inner forks, you have two options. You can use the gray buttons on the control handle with the "up" and "down" arrows. There is also a blue fork control lever on the right of the main panel- pushing forward on this lever will lower the forks, and pulling back will raise the forks. When the forks are raising or lowering, the top speed of the machine is reduced to the 1-click speed.

Recharging

The recharging unit is listed by Crown Corporation as an "optional accessory" on their website, though if you actually get a stacker without a charger you will soon own a 1 ton, $4000 paperweight. There is an LED-based power meter on the left side of the main panel. When the LED meter reads low or starts blinking (really low), you need to recharge soon. Make sure your recharging unit is plugged into a wall outlet, and that the unit is off. Turn off the stacker by turning the key on the control handle, NOT with the red power disconnect lever. The charger will have a second cord coming out of it, with a special proprietary gray plug on it. The stacker will have a similar-looking gray socket on it, but on different models the socket is placed differently. Some models will have the socket on the outside of the body, on the left side, about halfway down. Other models have the socket on the interior of the stacker. On that kind of model, you must physically open up the machine with a latch on the right side of the body. The gray socket is easy to locate once you're inside, because its brighter shade contrasts with the rest of the dark interior.

Adjusting the forks

To adjust the horizontal position of either of the inner forks, grasp the tip of the fork with your hand and rotate the fork up to a vertical position. The fork can now be pushed into the horizontal position you want it in. Once it is in the position you want, lower the fork back into a horizontal position.

Sources

The Crown Corporation website (www.crown.com)
personal experience with three models in the series

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