TRACK SCALES.

By H. T. PORTER,

Chief Engineer, Bessemer & Lake Erie Railroad.

In looking over competitive bids for track scales from time to time, the writer never was able to find that there was sufficient information in the plans and proposals of the scale companies by which one could make a comparison of the relative merit and capacity of the scales. In sending a man around to see the scales put in for other parties, the man who visited the scales would get some idea of the service they would give, but the information he would obtain would not be of value to anybody but himself.

In order to get up a set of specifications for our road, from which proposals could be submitted, one of our Assistant Engineers has been making inquiries among scale manufacturers, and persons who at the present time are engaged in other kinds of employment, but who in the past have designed scales, and the writer submits herewith a proposed set of specifications for 46-ft., 150-ton, four-section track scale, and for a 60-ft., 150-ton, six-section track scale.

We do not submit these specifications as a finished product, but as a first effort. This is a subject on which there is very little information readily available, and the writer thinks that a move should be made to standardize track scales. We once asked for bids on track scales without any attempt to give particular specifications, and were advised by one of the scale companies that by reason of the variations in details and methods of figuring, they could furnish 49 different kinds of scales under those requirements, and asked to have a man sent on to look over their plans and determine which would best suit us. This is merely mentioned to show the necessity of standardizing, as a great many of the variations in the construction have no special merit, but became necessary to satisfy the whims of the draftsman in the office of the purchaser.

GENERAL SPECIFICATIONS FOR 150-TON 46-FT. TRACK SCALE.

Plans,

BESSEMER & LAKE ERIE RAILROAD COMPANY.

Each bidder shall submit a strain and stress diagram of the scale he intends to furnish, showing thereon the proposed sections of the various parts under strain, and all plans showing details similar to those intended to be used in the construction of this special scale; these plans to be submitted at the time of making his bid.

Length,

The length of this scale shall be known as 46 ft.; this length to be the distance between the ends of the live rail. The ends of the live rail

should be vertically above a point located not less than one-fifth of the distance between the first and second scotion, distant from the center of the end section of the scale.

Number of Sections.

There shall be four (4) sections.

Rating.

The rating of this scale shall be known as 150-ton 46-ft. track scale. and this load shall be used in the design, each section to be considered as taking one-fourth of the rated tonnage, or 37.5 tons live load.

Dead Load.

The dead load of any part may be neglected when the strain produced by it is less than 22 per cent. of the strain produced by the rated load. Impact.

An impact equal to 100 per cent. of the rated load shall be everywhere added, in designing.

Grade.

The maximum grade to which the scale rails will ever be laid is 0.3 per cent., and such grade shall be obtainable by tapered shims to be placed between the bottom of platform stringers and supports, these shims to be omitted should the purchaser desire to have the scale rails level.

Load Adjustment.

Means should be provided by wedge blocks or other device for taking up any minor irregularities of the platform supports, on account of variations in manufacture or setting.

Deck.

The scale deck will be of the rigid type, supported by the pit walls, and will overhang the ends of the platform stringers to correspond with the design of the platform length, relatively to the lengths between sections.

Stringers.

The stringers shall be I-beams of Carnegie structural steel, Manufacturer's Specifications for Steel for Railway Bridges.

The span shall be considered as the c. to c. distance between any two sections, and the maximum bending stress calculated shall not exceed 16,000 lbs. per sq. in., assuming no continuous action over supports.

The minimum depth of I-beams shall be 24 in.

The stringers shall be thoroughly braced laterally by angles not less than 3 in. in width, and by transverse diaphragms. Connections to have 34-in. rivets or larger. No structural parts shall be less than 3-in. thick.

Special Clause.

Structural Steel.

The manufacturer will submit general plan of structural steel showing sizes and total estimated weight, at the time of making his bid, and all necessary scale dimensions in final plan, after contract is signed, which will enable a structural manufacturer to fabricate the steel to fit the scale details.

Suspension Bearings.

The load of the platform shall be transmitted to the main levers by means of suspension bearings. No forged links shall vary more than 1/16-in. from the dimensions shown on the plans.

Levers.

Main levers shall be of cast steel. Other levers may be of cast iron or of cast steel. Level tabs shall be cast on tops of levers about 12 in. c. to c. and faced accurately.

The unit stresses in levers shall not exceed the following values: Cast-iron, 3,000 lbs. maximum tensile stress.

Cast-iron, 18,000 lbs. maximum compressive stress.

Cast-steel, 8,000 lbs. maximum tensile stress.

Knife Edges.

The knife edges shall be separate from the bearing in main and extension levers and of silico-manganese steel; the load per linear inch of knife edge shall not exceed 5,000 lbs. Th lin of knife edges in any one lever should coincide as nearly as practicable with the neutral axis of the lever.

Bearing Blocks.

Cast-steel bearing blocks, self-centering the bearing on supports, shail support the knife edges.

Supports.

The scale levers shall be supported by cast-steel standards resting on concrete pedestals, and no parts subject to tensile strain shall have a unit stress exceeding 8,000 lbs.

The bearing on the concrete shall not exceed 300 lbs. per sq. in. Check Rods,

Check rods shall be provided transversely and longitudinally. Multiple.

The multiple of the beam pull shall be 800, but an additional rod whose pull is 400 shall be provided for attaching to 2 to 1 lever of StreeterAmet Recorder.

Beam.

The main beam shall be graduated in thousands of pounds, up to 200,000 lbs. An auxiliary sliding poise attached to the main latched roller poise shall move over graduations of 50 lbs. for 1,000 lbs. All weights in excess of 200,000 lbs. to be hung from the end of the beam.

The graduated scales shall be of brass.

Painting.

All parts, except wearing points and brass, shall be painted before shipment.

Foundation Plan.

The scale manufacturer shall furnish a foundation plan showing all necessary dimensions to install the scale. The pit shall be amply wide to permit thorough inspection and make all parts accessible.

Purchaser Furnishes.

The purchaser will construct the foundation to the dimensions shown by the manufacturer's plan and will place all bolts and structural steel that is to be built into the masonry. The purchaser will also furnish and construct the deck, weather guards around rail chairs, scale house, and provide foundation bolts, 100 lbs. scale rails and fastenings. Purchaser will furnish structural steel to fit dimensions shown on scale plans.

Easer Rails.

Easer rails will be provided for both ends of the scale by the purchaser, but the scale manufacturer shall not consider the length of the platform as affected thereby.

Superintendence.

The manufacturer will be notified when foundation is completed, and he shall furnish a competent erecting foreman to superintend the installation of the scales; any assistance this foreman may need will be supplied by the purchaser. Erecting foreman will be paid for at a rate per day as specified in the bid.

Inspection of Material, etc.

All material or workmanship shall be subject to the inspection of the purchaser's representatives.

Guarantee.

All parts failing as a result of defective material or workmanship of any parts furnished by the manufacturer shall be replaced free of extra cost to the purchaser.

GENERAL SPECIFICATIONS FOR 150-TON, 60-FT. TRACK SCALE.

Plans.

BESSEMER & LAKE ERIE RAILROAD COMPANY.

Each bidder shall submit a strain and stress diagram of the scale he intends to furnish, showing thereon the proposed sections of the various parts under strain, and all plans showing details similar to those intended to be used in the construction of this special scale; these plans to be submitted at the time of making his bid.

Length.

The length of this scale shall be known as 60 ft.; this length to be the distance between the ends of the live rail. The ends of the live rail should be vertically above a point located not less than one-third of the distance between the first and second section, distant from the center of the end section of the scale.

Number of Sections.

There shall be six. (6) sections.

Rating.

The rating of this scale shall be known as 150 tons, 60-ft. Track Scale for Continuous Service, and this load shall be used in the design, each section to be considered as taking one-fourth of the rated tonnage, or 37.5 tons live load.

Dead Load.

The dead load of any part may be neglected where the strain produced by it is less than 2% per cent. of the strain produced by the rated load.

Impact.

An impact equal to 100 per cent. of the rated load shall be everywhere added, in designing.

Grade.

The grade to which the scale rails will usually be laid is 0.5 per cent., although this may be varied either way to suit local conditions. The grade shall be obtainable by insertion of tapered shims between the bottom of platform stringers and supports, these shims to be omitted should the purchaser desire to have the scale rails level.

Load Adjustments.

Means should be provided by wedge blocks or other device for taking up any minor irregularities of the platform supports, on account of variations in manufacture or setting.

!

Deck,

The scale deck will be of the rigid type, supported by the pit walls, and will overhang the ends of the platform stringers to correspond with the design of the platform length, relatively to the lengths between sections.

Stringers,

The stringers shall be I-beams of Carnegie Structural steel, Manufacturer's Specifications for Steel for Railway Bridges.

The span shall be considered as the c. to c. distance between any two sections, and the maximum bending stress calculated shall not exceed 16,000 lbs. per square in., assuming no continuous action over supports. The minimum depth of I-beams shall be 24 in.

The stringers shall be thoroughly braced laterally by angles not less than 3 in. in width, and by transverse diaphragms. Connections to have 3/4-in. rivets or larger. No structural parts shall be less than 3/8 in. thick.

Special Clause,

Structural Steel.

The manufacturer will submit general plan of structural steel, showing sizes and total estimated weight, at the time of making his bid, and all necessary scale dimensions in final plan, after contract is signed, which will enable a structural manufacturer to fabricate the steel to fit the scale details.

Suspension Bearings.

The load of the platform shall be transmitted to the main levers by means of suspension bearings. No forged links shall vary more than 1-16 in. from the dimensions shown on the plans.

Levers.

Main levers shall be of cast-steel. Other levers may be of castiron or cast-steel. Level tabs shall be cast on tops of levers about 12 in. c. to c., and faced accurately.

The unit stresses in levers shall not exceed the following values:
Cast-iron, 3,000 lbs. maximum tensile stress.

Cast-iron, 18,000 lbs. maximum compressive stress.

Cast-steel, 8,000 lbs. maximum tensile stress.

Knife Edges.

The knife edges shall be separate from the bearing in main and ` extension levers and of silico-manganese steel; the load per linear in, of knife edge shall not exceed 5,000 lbs. The line of knife edges in any one lever should coincide as nearly as practicable with the neutral axis of the lever.

Bearing Blocks.

Cast-steel bearing blocks, self-centering the bearing on supports, shall support the knife edges.

Supports.

The scale levers shall be supported by cast-steel standards resting on concrete pedestals, and no parts subject to tensile strain shall have a unit stress exceeding 8,000 lbs.

The bearing on the concrete shall not exceed 300 lbs. per square in. Check Rods,

Check rods shall be provided transversely and longitudinally.