Technical Information

Cast Iron

Cast sections and base plates are supplied with unmachined surfaces painted, and are machined to the following tolerances:-

Cast Iron and Aluminium

The ends of all cut sections are supplied sawn such that they will clean up to the lengths stated iin this catalogue.

Steel

All steel parts are treated with a chemical black finish (unless otherwise stated) which gives adequate protection against rusting under normal workshop conditions.
Where stated as being surface hardened these parts have a wear resistant hardness in the range 50-60 HRC.
Metric threads are to ISO Coarse series except where otherwise stated.
Our products are constantly reviewed on a fitness for purpose basis and we reserve the right to change specifications, finishes etc. without prior notice.

Plastic

Please Note:
Data columns headed with g or kg refer to the approximate weight of each product.
All dimensions in metric unless otherwise shown.
 

Spencer Franklin Product Range
Available for the past 30 years the range is particularly suitable for simple clamping and presswork applications.

Using mainly single acting spring return cylinders the range offers a simple and economical solution to clamping and presswork problems.

Air/Oil boosters and pumps are usually part of the above systems – so the only service required is an air supply.

A unique product in the range is the ‘Hydraclamp’, providing an activated clamp either mechanically or hydraulically operated particularly suitable for hand finishing or assembly work. They are used extensively in the Aerospace Industry for Turbine Blade Finishing.

Clamping Force
Clamping force exerted by piston is dependent on two factors.

a) Oil Input Pressure P
b) Effective Area of Piston A

Expressed in equation Force = Pressure x Area
Where force is in kilograms
pressure is in kgf/cm2 or bar
area is in cm2

Example: A hollow cylinder to produce a force of 2000kgs is required a stroke of 6mm and an oil input pressure of 175bar. Using the above equation

A = F/P = 2000/175 = 11.43cm2

The PowRlock openram junior head SF-3100 MF has an effective area of 12.77 so would give a force of 12.77 x 175 - 2235kgs.

Selection of Pressure Source
For most applications PowRlock Air/Oil boosters are the fastest and most economical pressure source for PowRlock cylinders. Different models or boosters are available and these vary in only two essential details namely:

Pressure Ratio and Oil volume displaced

a) Pressure Ratio
The ratio between the air input pressure and the oil output pressure.
To determine the oil pressure available from any booster use the following formula

Oil Pressure P = Air Input Pressure p x Ratio of booster R

Example: To determine the oil pressure available from a type SF2630 Booster with a pressure ratio of 32:1 and with an airline pressure of 5.5 bar

5.5 x 32 = 176kgf/cm

Actual working pressure can be up to 10% less than theoretical due to system losses. Once booster oil outlet pressure is known we can determine the theoretical working force on any cylinder using the formula

Force = Pressure x Area

Example: To determine the piston force exerted by a junior head SF-3100MF with an effective piston area of 12.77cm2 and assuming an oil inlet pressure of 175kgf/cm2

F = 175 (P) x 12.77 (A) = 2235kgf

Again the actual force applied will be slightly less than this amount by the spring force of the SF 3100MF head I E approximately 18kgs.

Oil Displacement
This is the volume of oil available from a particular booster and determines how many small cylinders or indeed how large a cylinder can be operated from the single booster.

Oil volume required = Piston Area (Total) x Stroke(s)

Example: To determine the volume of oil required to achieve a stroke of 6mm on a junior head SF-3100MF with a piston area of 12.77cm2
Volume of Oil required = 12.77 x 0.6 = 7.7cm3

If 4 PowRlock heads are needed a booster with a minimum oil displacement of 4 x 7.7 = 30.8cm3 is required the SF-2640 booster with oil displacement of 53.99cm3 would suffice.

Note:
1) On booster/cylinder systems when using flexible hoses in the hydraulic pipework approximately 2cm3 volume of oil is lost to the cylinder due to hose expansion at 200kgf/cm2 per 30cm section.

2) The number of cylinders per booster has no effect on the piston force per cylinder when the full volume
is available.

Spencer Franklin System Design
Do not use the booster or cylinder return springs as dead stops.

Take care not to subject the linear cylinders to any significant side loading as this can damage the seals.

Calculate the total oil volume per cylinder to complete the stroke required . then select a booster with a capacity of 15-20% above the calculated figure, to allow for expansion etc.

Always use bonded washers when sealing parallel BSP threads.

For general clamping applications 1.4 bore hoses and 1.4 BSP air valves are suitable. For maximum speed of operation, i.e. on presswork use 3.8 or 1.2 bore pipework and air valves.
 
The shorter the flexible hoses the less the expansion losses.

Whilst booster will operate effectively when sited below the cylinders, the bleeding of the system and maintenance are much easier if the booster is placed at the highest point of the system. The use of a self bleed reservoir SF-4957 will make air removal easier.

Technical Information

Bleeding The Hydraulic System
The bleeding of a PowRlock circuit is exactly the same principal as the automobile hydraulic braking systems, except normally the automobile is on level ground and it is recommended to commence bleeding from the farthest point of the hydraulic energy source. The PowRlock system is simpler in effect as it is recommended to bleed from the highest point of the circuit and if it also be the hydraulic energy source (i.e. Booster, Lever or hand pump) so much the better.

If the circuit to be bled is an existing one and has air bubbles entrained, consider at this point the necessity for seal and fluid renewal.

Slacken off connectors (finger tight) and introduce fluid at the highest port connection, filler plug or hose, which shall be referred to as the "high point" for convenience.

Starting from the lowest point, slacken connection to allow a flow of oil to escape from the system (wasted fluid should be prevented from contaminating floors by using a drip tray). When flow becomes continuous and free from air bubbles . tighten connection, top up system with fluid at high point - continuously during bleeding. Repeat procedure at every clamping head or ram working upwards towards high point.

Should the high point be in the middle of the circuit, start as above from one end working upwards to high point and then repeat from other end of circuit. Having secured all connections including high point, cycle unit several times and then switch off. Remove high point connection and top up with fluid if necessary, repeat until system is fully primed.

On Presswork applications the use of a booster reservoir assembly type ref. 4957 will greatly assist in the bleeding of the circuit and prove most useful as a permanent feature of the hydraulic circuit. If in doubt contact your local Sales Engineer, who will be pleased to advise you.

Recommended Hydraulic Oil

SHELL TELLUS 37
CASTROL AWS 32
ESSO ESSTIC 43
LORCO HT32
VAUGHAN HYDRODRIVE HP 150
MOBIL DTE 24
BP ENERGOL H.L.P.32
S.A.E. S.A.E. 10w HYDRAULIC
TOTAL AZOLLA 32

This list of equivalent fluids has been compiled for the convenience of users who may already use other suppliers.

DO NOT USE AUTOMOBILE HYDRAULIC FLUIDS OF ANY DESCRIPTION.

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