Towing Options for Mobile Hydraulic Machines

Towing Options for Mobile Hydraulic Machines

Richard Tatum | February 28th, 2018

Towing mobile hydraulic machines is not traditionally an easy, cut and dry exercise. Any time you tow or move a hydraulically driven machine without disconnecting the hydraulic motor you can damage the system.

For example, when you turn a hydraulic motor and it is not under power, it essentially becomes a pump and, because there is no inlet pressure, it begins to cavitate. This can happen over a very short amount of time and can cause catastrophic failure to not only the motor but other parts of the system when metal debris from the motor gets ingressed.

Luckily, Auburn Gear (AGI), a manufacturer of wheel drive and track drive mechanical gearboxes, thought of this. AGI products are typically used in conjunction with hydraulic motors to not only provide you with substantially more torque but also additional bearing support for your bigger more heavy duty machines. This is a huge advantage because these large types of machines typically cannot be trailered due to their size. They either have to be pulled/trailered or repaired on site which is costly.

The Auburn Gear Disconnect

The solution that AGI has developed is unique and has several options, all of which “disconnect” the gearbox mechanically from the hydraulic motor so that you can move the machine without the risk of damaging the hydraulic components in the system.

In this case, “disconnect” refers to how Auburn Gear disengages the shaft or primary drive gear from the rest of the gear in the planetary. This is important because it allows for the shaft to spin freely on the support bearing, giving you the ability to pull/push your machine while completely disconnected from your hydraulic system. This means that you can tow or move your machine effortlessly and without potentially costly damages to your hydraulic components.

Here are some towing methods to consider.

Twist-To-Tow

This towing method utilizes a handle that is located on the center hub. To engage this “disconnect” and enable your vehicle for towing, you need to pull on the handle and rotate it 90 degrees. There is a seat for the handle that locks the towing engagement into place when you release it.

Twist to Tow

Utilizing this form of mechanical disengagement, you disconnect the spindle or primary gear from the secondary gear. This essentially means the shaft is spinning freely which utilizes only the bearings on the shaft, giving you the ability to tow at highway speeds up to 70 MPH. This system is pretty common on the Auburn Gear Model 3/6B/7 units ranging from 9900 lbs of radial load capacity to 14,400 lbs.

Standard Disconnect

On all Auburn Gear planetary gearboxes, there is a standard disconnect feature included from the factory. Many people may not know this, but there are two bolts located on the outer hub of every Auburn Gear unit. If you remove these two outer bolts, remove the center small cap, then flip the cap over and reinstall the bolts, this will disengage the planetary and engage your vehicle for towing. The dimple or nipple on the cover (shown below) forces the input shaft to disengage from the primary sun gear.

Standard Disconnect

To re-engage this feature so that you have power to your gearbox, you would reverse this procedure. This form of disengagement is rated at only 25 MPH or the max rating shaft speed of the gearbox. The reason that AGI must de-rate the speed of this form of disengagement is that this method only disengages the hydraulic motor from the gearing. The gearing still rotates with the wheel however and thus there is a lot of rotating mass, which is what limits how fast the planetary can spin.

Even though you cannot tow at highway speeds, most mobile machines are not going to be towed more than 25MPH. This is more of a way to get the machine back home so that you can make the repairs that are needed in a shop rather than in the field where a remote technician can be rather costly.

Quick Disconnect

Utilizing similar technology as the previously mentioned standard center cap method, the quick disconnect acts the same way but utilizes a nice “push button” to engage/disengage the towing function on the planetary. This method can be field retrofitted with the standard AGI unit to use this push-button technology if required for machines already in service. It too is limited at towing speeds of 25 MPH or the max rated shaft speed of the planetary for the same reasons as mentioned above. The benefits of this over the standard unit style are speed and convenience.

Quick Disconnect

Remote Disconnect

Lastly, there is a remote disconnect option available that is very common for the wheel drive motor design (including cartridge motor design). The integral brake is replaced with a disconnect clutch that is shifted with a hydraulic pilot signal to engage the freewheel or towing function. Once the pilot signal is removed, the unit reverts back to driving mode. This is highly convenient for the mobile machine market, where you can select from a 2WD to 4WD on the fly without exiting the vehicle.

It can also be used to switch from high-speed tram to high-torque tram depending on how you run your hydraulic motors. This can give you all sorts of flexibility on how you use different functions on your machine. Similar to the other designs, this is limited to a 25 MPH towing capacity due to the rotating mass of gears that will be spinning inside the gearbox while towing.

Which Option Is Right For You?

All of these options have their right applications. Cross Company can help if:

  • You have an interest in towing your mobile hydraulic machine.
  • You see an area where this technology may apply to your business.
  • You want to see where you can implement Auburn Gear into your machines.

We would be happy to help dive in and answer your questions.

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Richard Tatum

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Richard is the Regional Sales Manager for Cross Company's northern region. He has a Mechanical Engineering degree from Auburn University and an MBA from Marshall University. Richard has experience in many industries including Mining, Agriculture, and Construction and has been with Cross Company since 2013. A man of many hobbies, he enjoys golfing, boating, motorcycles, skiing and anything else that will get him out in the sun to enjoy the weather. Richard is outgoing and is always willing to reach out and help you find a solution to your problem.