FAQs

What is the maximum input RPM for jacks and actuators?

Limited to 1750 RPM for jacks and actuators. Maximum input RPM may be slower than 1750 RPM depending on the dynamic load and other factors specific to the application. Refer to the JAX® Online softwareand information located in the product section for more detail or contact sales@joycedayton.com and talk with an application engineer.

What is side load?

Standard jacks and actuators are not designed for dynamic side loads. The load must be positioned axially. Static side loads are limited. Contact sales@joycedayton.com for technical assistance.

What is duty cycle?

Relationship between operation time and rest time. The allowable duty cycle for jacks and actuators is based upon several application variables such as load, speed, and temperature. Consideration must be given to the severity of the duty cycle during the product selection phase. Contact sales@joycedayton.com and talk with an application engineer about your requirements.

What are self-locking jacks?

Self-locking is a term used to describe jacks that require power to move in either direction. They hold their position when power to the system is off. Exceptions include Ball screw jacks, WJ500, machine screw jacks having double lead screws and ECA electric cylinders that are more than 30% efficient and all ball screw jacks. A brake must be used on the input shaft of any jack that is not self-locking. A brake should also be included for applications that expose the jack or actuator to vibration. Contact sales@joycedayton.com for more information.

Which jacks require a brake motor?

Any jack that will lower under load requires a brake motor. This includes ball screw jacks (WB, HWB, WBL, HWBL), ball screw ComDRIVEs® (CDB, CDBL, CDHB, CDHBL), ball screw electric cylinders (ECB), ball screw integrated actuators (BIA, HBIA), and bevel ball actuators (BB). Machine screw jacks with double lead screws and WJ500 jacks may also require brakes to hold postion.

What are travel speed limitations for various jacks?

Typical travel speeds for various jacks and actuators are measured in inches per minute (IPM). Speeds depend on the input RPM, load, internal ratio and lead of the screw. Maximum allowable travel speeds for machine screw jacks are typically slower than ball screw jacks. Wormgear jacks typically have slower travel speeds than bevel gear jacks. Refer to the JAX software for more detail or contact sales@joycedayton.com and talk with an application engineer.

How is the maximum screw length determined?

Maximum distance from the base of the jack to the end of the extended screw. It is limited by the column load in compression. Refer to column load charts or use the JAX selection software. Contact sales@joycedayton.com with questions.

What is the calculated life of machine screw jacks?

There is no formula available to calculate the life of a machine screw. If a calculated life for the screw is required, specify ball screw jacks, ball screw ComDRIVEs®, ball screw electric cylinders, ball screw integrated actuators, or bevel ball actuators. Contact sales@joycedayton.com for more information.

What is the calculated life for ball screw jacks?

The calculated life for ball screws is based on the ball nut life. This information is available for all ball screw jacks, ball screw ComDRIVEs®, ball screw integrated actuators, bevel ball actuators, and ball screw electric cylinders (ECB). It can be obtained using JAX Online Software (browser-based software) or by contacting sales@joycedayton.com with your requirements.

What are screw stops and how are they used?

Stops are offered as options for screw jacks and actuators, and are not to be used as operating limits. Engaging the stop may prevent damage to your structure but will most likely damage the jack. To control jack or actuator travel, include limit switches in the system design. Including stops may increase the closed height of the jack and the length of the protection tube. Refer to specific ordering sections in the catalog or contact sales@joycedayton.com for more information. Note: Screw stops are standard on all Joyce ComDRIVE® jacks. When screw stops are included on jacks the length of the lifting screw increases.

Why should hard stops (impacts) be avoided in normal operation of jacks?

Jacks are not designed to operate into a hard stop. Sudden impacts and shock loads may cause damage to jacks and actuators. Customers are responsible for providing travel limits to avoid this situation. Contact sales@joycedayton.com for more information on the options Joyce offers.

What is the standard operating temperature for most product?

The standard operating temperature range for most products is 40°F – 220°F. There are some exceptions. For operation outside this range, special lubricants and seals can be provided. Please contact sales@joycedayton.com for more information.

How are wormgear jacks lubricated?

Standard wormgear jacks are lubricated with NLGI grade #1 grease prior to shipment. Specific information and commercial brand names can be found in the Operation & Maintenance Manuals, which are available on specific product pages.

How are Bevel gear jacks lubricated?

Bevel Gear jacks use both NLGI grade #1 grease and oil. The upper bearing and jackscrew are grease lubricated while the remaining internal components are oil lubricated. These jacks are grease lubricated prior to shipment;however, oil must be added to the unit prior to operation. Contact sales@joycedayton.com for more information.

What should be considered when mounting jacks horizontally?

When jacks are mounted horizontally, Joyce/Dayton recommends that the input shaft (worm) be mounted below the lifting screw and parallel with the horizon. This position provides the most lubrication to the input shaft (worm), and to both worm shaft bearings. The load capacity of the jack may be reduced when the lifting screw is mounted horizontally. Bevel gear jacks should not be mounted horizontally. Please contact a Joyce/Dayton application engineer at sales@joycedayton.com to discuss horizontal applications.

What should be considered for designs that require high screw RPM and long screw lengths?

Keyed for traveling nut (KFTN) jacks with long screw lengths require additional support when the screw rotates at high RPM. Contact a Joyce/Dayton application engineer at sales@joycedayton.com  application engineer to discuss applications that require high screw RPM and long screw lengths.

What is the difference between Upright and inverted jack configurations?

The difference between an upright and an inverted jack is the location at which the lifting screw exits the jack relative to the jack base. For example, an upright jack's lifting screw exits the jack opposite the base. An inverted jack's lifting screw exits the jack on the same side as the base. The choice between inverted and upright jack is dependent upon the application.

Note: An upright jack mounted upside down is still referred to as an upright jack.

How can I determine worm shaft rotation extending the lifting screw?

Refer to the views of the standard jack with right hand screw threads below:

  • For an Upright jack:
    CCW rotation of right input shaft extends the lifting screw. CW rotation of the left shaft extends lifting screw.
  • For an Inverted jack:
    CW rotation of right input shaft extends lifting screw. CCW rotation of the left shaft extends lifting screw.

How is the linear travel speed calculated?

Each screw jack and actuator has an inherent number of input shaft turns per inch (TPI) of screw travel. TPI is the result of the jack's gear ratio divided by the lifting screw lead. The TPI can be found on jack specification pages at the beginning of many product sections. A model WJT242 has a TPI of 96. If 350 RPM is applied to the input shaft, the resultant linear speed of travel is 350/96 or 3.65 inches per minute. JAX® Online software automatically calculates travel speeds for you. 

Are screw jacks lubricated prior to shipment?

All Joyce machine screw jacks and ComDRIVEs®, ball screw jacks and ComDRIVEs®, bevel ball actuators, integrated actuators, and electric cylinders are lubricated with an extreme pressure NLGI grade #1 grease before leaving the factory.

Bevel gear jacks are lubricated with NLGI grade #1 grease and oil. The upper bearing and jackscrew are grease lubricated while the remaining internal components are oil lubricated. They are grease lubricated prior to shipment; however oil must be added to the unit prior to operation.

Linear actuators (LA) are lubricated for life.

What are the standard end conditions for screw jack lifting screws?

The following standard end conditions are available on Joyce/Dayton screw jacks:

Type 1 
plain turned end

Type 2 
load pad with mounting holes

Type 3 
male threaded end

Type 4 
male clevis end

Contact sales@joycedayton.com for information about custom end conditions.

How is the clevis, T4 end, positioned on a keyed jack?

  • Standard clevis mounting position – the hole in the clevis end is parallel with the worm input shaft.
  • Optional mounting position – the hole in the clevis end is perpendicular to the worm input shaft.

How is the load pad, T2 end, positioned on keyed jacks?

  • Standard load pad mounting position – the holes on the load pad are on the jack centerlines.
  • Optional load pad mounting position – the holes on the load pad end straddle the jack centerlines.

Can I buy a jack with a clevis on both ends?

Yes. When freedom of movement in two axes is required, a double clevis jack may be specified. Double clevis jacks are always made from upright jacks. Stroke lengths are limited based compression loads. See the chart at the end of the entry. Contact Joyce/Dayton with application details.

  • Double clevis jacks incorporate a clevis machined or pinned onto the screw end and also a clevis welded to the protection tube. Screw travel is limited. Contact sales@joycedayton.com for more information.
  • Electric cylinders, integrated actuators, linear actuators, multipurpose actuators, and solar actuators are also available with a clevis on both ends

Machine Screw Jack

Max Load

Max Rise at full load in Compression

Reduced Load

Max Rise at Reduced Load in Compression

1/4-ton 500 LB 7.00 Inches 500 LB 7.00 Inches
1/2-ton 1000 LB 9.00 Inches 1000 LB 9.00 Inches
1-ton 2000 LB 8.00 Inches 1500 LB 10.00 Inches
2-ton 4000 LB 12.00 Inches 3000 LB 14.00 Inches
3-ton 6000 LB 12.00 Inches 3000 LB 14.00 Inches
5 ton 10,000 LB 17.00 Inches 6500 LB 22.00 Inches
10-ton 20,000 LB 23.00 Inches 12,000 LB 31.00 Inches
15-ton 30,000 LB 26.00 Inches 16,000 LB 37.00 Inches
20-ton 40,000 LB 29.00 Inches 21,000 LB 42.00 Inches
25-ton 50,000 LB 47.00 Inches 37,000 LB 56.00 Inches
30-ton 60,000 LB  47.00 inches  37,000 LB  56.00 Inches
35-ton 70,000 LB 69.00 Inches 62,000 LB 74.00 Inches
50-ton 100,000 LB 90.00 Inches 94,000 LB 93.00 Inches

 

What is meant by self-locking?

Self-locking is a term used to describe jacks that require power to move in either direction. They hold their position when power to the system is off. 

What if the jack is not self-locking?

A brake is required on the input shaft of any jack that may lower under load (ball screw jacks, WJ500 jacks, double-lead Acme screw jacks, electric cylinders that are more than 30% efficient, and some integrated actuators). 

How much side load can be placed on a screw jack?

Standard jacks and actuators are not designed for dynamic side loads. The load must be positioned axially. Static side loads are limited. Contact sales@joycedayton.com for technical assistance. 

How much backlash is in a machine screw jack?

In machine screw jacks there are two types of backlash: worm to wormgear backlash (typically 8-15° worm rotation), and lifting screw to nut backlash, sometimes called endplay (up to 0.020 inches on new standard jacks). These values are automatically calculated for all products sized in Joyce's free JAX® Online Software for all products. Contact sales@joycedayton.com for more information.

Can I reduce machine screw backlash?

Yes, screw backlash can be adjusted on translating and keyed style machine screw jacks via one of the following anti-backlash options: standard split-nut design; A90 external nut adjustment; or A95 design. Contact sales@joycedayton.com for more information.

What is screw lead error?

The deviation from the mathematical lead expressed in inches per foot cumulative.

What is the amount of lead error in a standard lifting screw?

Rolled Acme screws have up to .010 in/ft cumulative error, milled Acme screws have up to 0.003 in/ft cumulative error; and ball screws have up to 0.007 in/ft cumulative error. Contact sales@joycedayton.com for more information.

Are Joyce/Dayton jacks and actuators user-serviceable?

The level to which products can be serviced in the field varies from product to product. Refer to the product Operation & Maintenance Manuals or contact sales@joycedayton.com for more information.

What motor options are available?

Motor options vary among product lines. Customers can use AC 3-phase, AC single-phase, DC motors, international voltage motors and others. Let us know your requirements.

The motors on linear actuators are an integral component. They are available in 120 VAC, or 12 VDC.

What is the clutch on a linear actuator and how is it used?

A screw clutch device is an option on linear actuators (if they do not have limit switches). This device allows the screw to turn if the actuator is operated against a hard stop. This is an emergency protection device, not to be used repeatedly as an end of travel stop.

Are limit switches preset?

No. Limit switches on multipurpose actuators (MA) are preset at the factory. All other limit switches must be set according to specific directions. 

  • Shaft-mounted rotary cam limit switches must be set to the required positions during installation.
  • Limit switches on linear actuators must be set after the actuators have been installed in order to tailor the stop position to the individual application. (O&M Manual ACO&M Manual DC)

What do I need to consider when ordering a bellows boot to protect the lifting screw?

  • Closed height dimensions may increase when boots are added.
  • The customer must specify boot collar diameter when ordering bellows boots for KFTN jacks.
  • Zippered boots are also available.
  • Special boot material is available.
  • Horizontal screw applications may require boot guides.

Contact sales@joycedayton.com for more information.

Are jacks and actuators corrosion resistant?

Stainless steel jacks are inherently corrosion resistant. All exposed surfaces are stainless steel and aluminum bronze. Most other jacks can be modified with special finishes, coatings, and seals. Contact sales@joycedayton.com with your requirements. 

What is a follower nut assembly and when is it helpful to have one?

Follower nut assemblies allow customers to gauge the wear on the wormgear screw thread of translating jacks and on the traveling nut screw thread of KFTN jacks. This allows customers to replace the nut before its threads wear too thin to support the design load. These assemblies generally consist of a gear nut or traveling nut pinned to a second nut of dissimilar material. A preset gap separates the two nuts. As the wormgear or traveling nut threads wear, the preset gap narrows. The assembly is replaced when the gap measurement reaches the design limit. Follower nut assemblies are designed for specific applications. Contact sales@joycedayton.com for more information.