Feed Table Lift Application
A steel tube manufacturer is developing a new OD polisher that will increase production by 22%. Because of the increased production time, the set-up crew is unable to set the feed table manually and is looking to automate the feed table height using worm screw jack systems. The feed table length is 24 feet and weighs 5,600 lbs with the largest diameter steel pipe. The table height will need to change approximately once every 15 minutes, but no more than 10 times a day. Maximum height change is 9 inches. The travel rate is .4 inches per second.
Step 1: Determine Specifications
- Single motor and drive, with the possibility to remove the motor and drive by hand
- The load will be in compression
- Total travel 14 inches
- .25 inches in 1 second
Step 2: Analysis
Because of the possibility to be hand driven, a machine screw jack with 24:1 gear ratio is needed to prevent back driving. Based on the mounting constraints, the upright translating jack with a clevis rod end will be the type of linear motion system used. Due to the length of the feed table, four jacks will be used in-line with a center mounted motor through a single gearbox.
The jacks will be loaded in compression and in mounting condition D. Based on the load and number of jacks, the 2.5-MSJ jack or larger could be used.
Speed and Horsepower:
Using a standard 1750 AC motor and the 2.5-MSJ with 12:1 gear ratio, the travel rate will be .6 inches per second. Using the horsepower formula on page 15 of our Worm Gear Screw Jacks Catalog, the horsepower limit would be exceeded. Using the 5-MSJ 24:1 gear ratio, the travel rate will be .45 inches per second and the horsepower per jack will be sufficient to lift the load. A 3 HP motor would be adequate for the requirements.
|HPper jack =||.0144 in-lb × 1,400 lb × 1,725 rpm||= .56 hp / jack|
|HParrangement =||.56 hp per jack × 4 jacks||= 2.92 total hp|
|.85 × .9|
LinkJac Line Shafting:
The longest center to center distance between the jack and gearbox is 48 inches, leaving a shaft length of 41 inches. Since the motor is located in the middle, only half the total torque is needed for calculated torsional twist. Using the formula on page 189, the proper Line Shafting to use would be the LJ-16.
|NSpeed =||.6192 × (||π||)2 × 1.168 × 106 = 4,246 rpm|
|NTwist =||80.64 in-lb ×(||41 in||) = .17o|
Step 3: Product Selection
Create a Reference Number for the Assembly
From page 69, create reference numbers for the following: three 2.5 ton ball jacks, upright translating configuration, 24:1 worm gear ration, 14 inches travel.
- (4) 5-MSJ-U 24:1/SSE-1/SSE-2/FC/14/S
- (1) GB210S Type D
- (2) LJ-16 17" OAL
- (1) LJ-16 12" OAL
- (8) C-1805-02 (¾ - 1)
- 3 HP AC Motor 1750rpm
Step 4: Product Data PagesFigure 1