Straightline Head

Straightline Head

   The Geo-Log Straightline Measure Head is a redesign of an older system originally used by Gearhart.  The new system is intended to be an economical and timely replacement for older wireline units being refitted, new projects, and for updating sections of the old system. The chassis, which carries the pressure roller assembly and alignment rollers, employs similar hooks, and critical dimensions to facilitate interchanging parts between the new and old system.  It is possible to put the new Geo-Log lower frame assembly on a Gearhart chassis or use the new Geo-Log chassis with the Gearhart lower frame assembly.  Some parts and sub assemblies will interchange on the Gearhart chassis only, although they are not identical.

Straightline Head Data: 

Assembly Number: 900500-100

Length: 23.75 inches

Weight: Approximately 43 Lbs.

Height: 14.5 inches 

Width: 8 inches standard pattern (one mechanical drive and one encoder drive)

Line sizes: .187" to .500" diameter

Chassis assembly

The chassis is machined from solid 6061 T6 aluminum plate, and two are required per assembly.  The standard finish is black anodized.  When the logging truck hanging/guiding system is properly balanced, the measure head assembly is subject to very little stress.  However, the Geo-Log system is exceptionally strong, and stronger than the older Gearhart system.  A generous amount of extra material has been left at each end of the chassis to customize roller spacing for exceptionally large cables i.e. 1/2 inch dia..

Pressure roller assembly

The pressure roller assembly is a subassembly of the chassis.  The roller and its shaft are made of 17-4 SS Condition 1075.  The same seals (4 required) used in the older Gearhart system are used in the Geo-Log system.

The roller bearing (2 required) is the same as the Gearhart system and 2 snap rings hold the bearings and seals in place at each end of the shaft.  The bearing block may not be interchangeable with the old system.  However, all the seals and bearings of this assembly have been made the same to help reduce inventory for users who have both systems in the field.

The Geo-Log pressure roller assembly uses slightly heavier springs than the older systems.  This gives approximately 30 pounds more pressure on average size cable.

Guide rollers

Six guide rollers have been standardized at 1.5 inches in diameter.  Standard material used is 17-4 SS condition 1075. The guide rollers contain bronze bearings.

The Geo-Log chassis is drilled in steps so that different line sizes are accommodated by moving the 4 vertical rollers to increase or decrease the distance between them for different size cable.  This feature makes it easier to standardize to one roller diameter.  The closer the vertical rollers are to the measure wheel the smaller the cable.

The 2 bottom horizontal rollers are straightline and tangent to the measure wheel surface. 

Note: The system is, in theory, exactly straightline from the roller surface to the measure wheel surface; but due to wear and the need for more than a tangental contact, there is a 0.025 invasion of the measure wheel into the theoretical “straight line”.

Side Plate Assembly

The aluminum side plate assembly consists of two 1/4 inch clear Anodized aluminum plates.

SF-12 Seal Master bearings provide the support for the measure wheel shaft.  This item is the only painted part of the Geo-Log system, and it can be easily replaced at a bearing supply store or at Geo-Log, Inc. in Granbury, Texas.

The clamping assembly and pens are aluminum and stainless steel respectively.

All fasteners are stainless steel to control corrosion.

One encoder mount and one mechanical drive connection with cover are standard.

Measure wheel

The standard measure wheel is made of 17-4 SS condition 1075.

Direct your inquiries to Roger McKenzie at 817-326-5321 or email

Assembly Drawing | Assembly BOM