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Reconditioning / Hydraulics Testing / Electrics Testing
Rotor Shaft Reconditioning

Whilst we are unable to "raise the dead" we do have many years experience of reconditioning rotor shafts back to a professional level. Rotor shafts returned undergo straightness, sensitive dimension and balance checks. In addition to this customers can expect the satisfaction of knowing that all parts used are original and backed by the Bomford warranty scheme. Many of the forged flails are even guaranteed unbreakable. In the event of an accident involving flails how many insurance companies would accept third party claims where non original parts were fitted? Vibration must be viewed as a VICIOUS GREMLIN and will totally destroy a cutting head.

The first signs apart from the noise are characteristic cracks radiating from the corners of the cowl or from stitch welds. If this is not attended to at these early signs then total destruction will ensue. Vibration may be caused by a number of reasons, the most common being a bent centre core, the second through worn bearings. It should be noted at this stage that vibration from a bent rotor will inevitably cause bearings to fail. In the early stages of vibration a simple check to determine which component is causing the vibration is to run the rotor horizontally and then vertically. If the vibration varies significantly then it is more likely to be bearings at the route of the problem. However if the vibration remains constant then the rotor will be the likely cause. Other points to look for which can create vibration are lost balance weights and uneven knife and or component replacement.

This is another reason why it is important to buy original parts. All original parts are made to stringent weight constraints. When replacing flails it is prudent to replace the correspondingly opposite flail. The removed flail can be reused at a later date with an other matched worn flail. It must be appreciated that once a rotor shaft has been bent and hence deformed the bearing journals then it is just about impossible to get the journals back onto the same axis.

Our straightening process will ensure that these journals are brought back as close into alignment as possible. If this is not done then the self aligning part of the bearing will become continually flexed. This leads to premature wear and failure.

What Do I Do Next ?

Remove the rotor from your cutting head and place it in the hands of your Bomford distributor. He will obtain a job number and return the rotor to us. Everything else is then down to us. The next operation you will be doing is fitting the repaired rotor back into your cutting head. The time taken for us to do our part will be about ten days, although this is subject to seasonal demand.


Without placing the rotor between it's centres it will not be all that easy to detect any bend. The rule of thumb is that by removing flails from the centre of the rotor, mounted between bearings, and if any deflection can be measured then the rotor must be considered bent.


A rotor shaft, complete with new components that is ready to fit straight into your cutting head as shown above. It is however recommended that this reconditioned rotor shaft is mounted onto new bearings. These bearings are not supplied.


This is not that easy to accurately predict as the total cost will depend on what we have to do to the shaft and which flails are fitted. However as a guide we can predict that it will cost between a third and half the cost of a new replacement rotor. If there are any concerns over this we will gladly produce a quotation once we have had a chance to inspect the rotor prior to us starting work.




Cutting Head Reconditioning

In addition to this rotor shaft service we are also able to recondition complete cutting heads. The cutting head is the work horse of any machine so naturally gets the brunt of the damage. In many cases the cutting heads can look many years older than the base it is working on. Examples of our work can be seen in the photograph below. These three cutting heads are a recent example of three heads from the South Cambridgeshire DC, Oakington, Cambridgeshire as part of an out of season repair programme on their long reach mowing machines. South Cambridgeshire DC are unique in as much that they are one of only a handful of District Councils who are responsible for land drainage maintenance within their Council district. Cost involved again not all that easy to predict but we would expect half to three quarters the cost of new prices. As with the rotor shafts the customers would have the benefit of original parts used and assembled by specialist Bomford Service personnel.




Included in this service we would expect to change all the consumable parts, belts, bearings, flexible guards as well as giving the roller and rotor shaft a thorough reconditioning. This is then finished off with a coat of powder coat paint along with the standard head decals as seen. The condition of the motor in these cases were assessed previously when the head was fitted to the base machine, along with the pump.



It is expected that the following information is used for the purpose it was intended. The information is intended to be used by qualified Technicians who will not only be able to interpret the recorded data but who will conduct the tests in a safe and workman like manor. We cannot emphasise enough the use of sound safety practices.

Generally the testing can be carried out on Bomford Turner hydraulic flail mowers and hedgecutters with the following equipment


The flow meter should have the ability of measuring flows of up to 180l/m, pressures of up to 400 bar ( 5800psi ) and ideally have a temperature gauge incorporated within the system. A loading valve must also be available within the unit.

The feed and return ports should be in the order of 1" BSP.


This may be of either a strobe type or a mechanical direct reading type. It should be capable of measuring 4000 rpm.


The machine base designation will help you a great deal in understanding not only the reach of the machine but also the hydraulic capacity of the motor drive system.

EXAMPLE 1:   B54MPS Power Plus






EXAMPLE 2:   B608


60   6.0 METER REACH




80    8.0 METRES REACH 



"B" designated machines indicate the reach mostly in metres. Where the reach number is repeated the machine is able to cut on both sides of the tractor e.g. B45-45 or B81-81. These machines will cut this distance on each side of the tractor from it's centre line to the extreme flail.

"LR" designated machines show the reach directly in feet.

"S" designated machines again indicate the reach in feet.

Where "T" is used as a suffix it may denote that the machine is a twin pump unit. However in latter years most machines are twin pumped and the "T" will probably denote that the second arm is a telescopic arm. The letters EPP (Electronic Parallel Proportional) are used to indicate the electronic proportions controls on the machine.

We therefore have the following hydraulic systems.


7 70 litre systems - max. pressure 152 bar (2200psi ) or
 8 84 litre systems - max. pressure 207 bar (3000psi ) or
X 100 litre system - max. pressure 207 bar (3000psi ) or 
POWER PLUS 125 litre system - max. pressure 207 bar (3000psi ) or
PISTON VOLVO 90 litre system - max. Pressure 350 bar (5100psi ) or
PISTON EATON 114 litre system - max. Pressure 275 bar (4000PSI)
"S" 112 litre system - max. pressure 172 bar (2500psi)
"LR"  MKI MKII 72 litre system - max. pressure 207 bar (3000psi)
LR16/14-84 84 litre system - max. pressure 207 bar (3000psi)

Rotor feed and return pipe are either 1"BSP or ¾" BSP. All 207 bar machines have as a minimum double wire pressure hose. The piston machines with a relief valve setting of 275 and 350 bar having a minimum of triple wire pressure hoses. All unions are swivel nuts with male soft seal cones. This relates to an "O" ring sunk into the male cone. All machines with the exception of some B577, B73-73 and B83-83 are to the BSP standard, these exceptions are built to the JIC standard.


This information is essential if any of the machines are to be evaluated hydraulically. All tests should be conducted at a temperature as close to 40 degrees centigrade as possible.

The flow meter should be inserted in place of the motor. This diagramatically looks like the sketch below.


All Bomford Turner pump specifications are rated at a PTO shaft speed of 540 rpm except for the Eaton piston systems, these are rated at 1000 rpm. This speed, in most cases, is increased 3 or 4 fold to achieve the desired pump speed. It is therefore very important to ensure that the tractor PTO shaft is in good working order and that the tractor engine has enough power to maintain the 540/1000 rpm at full power. Errors through the transmission are multiplied by this same ratio. Running the test in the 1000 rpm ratio at the 540 speed can and does reduce the power available from the tractor. It is therefore possible that the tractor will stall when using this arrangement.

With the flow meter in the circuit, the PTO shaft at the correct speed, we can now take the no load reading of the pump from the flow metre. That is zero pressure but maximum flow. This nominally will be at any of the system flows i.e. 70, 84, 100 litres etc.

For the next step you may find the graph on page 6 useful. We have now to establish the efficiency of the unit. By plotting pressure against flow we can accurately do this. Fig.I shows the plot of two hydraulic pump outputs. Naturally if we only had the one set of figures then a bad pump would not be quite so obvious. The simple calculation in Fig.II can then be used to highlight the deficiency of the unit. We can therefore calculate this efficiency or by experience, look at the shape of the graph to illustrate the pumps condition, i.e. the flatter the curve the better the pump. Conversely the steeper the gradient of the graph the lower the efficiency. The graph shows a typical output for a gear pump, a piston pump will be flatter with little fall off in the early stages of testing.

To achieve the figures for this graph the loading valve is wound in to increase the load on the pump. At say 25 bar increments note the flow output of the pump in litres. These figures are then transposed into the graph form.

Pressure is only achieved by the action of work done. A pumps output is not measured in pressure but capacity. The power equation is a product of the flow and the maximum operating pressure multiplied by the efficiency figure. This will help in the identification of a poor hydraulic unit. The level of acceptability in some way will depend very much on just what the machine is being used for, e.g. the lower pump as on the graph below is absolutely worn out and not much use to anyone. However if a pump is giving a little lower than expected output then it may well be satisfactory for the lighter duties but it should be remembered that once the output falls it is only a question of time before we have a total failure. We would consider that any deficiency figure over 15-16% is too low for general operations. Progressive overheating will occur, the severity of which will depend on the deficiency figure.

Generally, even a bad pump may achieve the maximum pressure rating. However this is no good without a good flow output. The maximum pressure setting being reached will only indicate that the pressure relief valve is set correctly and in working order. The relief valve should hold pressure to just under it's full flow setting. The relief valve will then "crack" at this lower setting- something like 10 bar below the maximum. This is designed in to prevent high pressure peaks or over shoots when the valve opens. The relief valve will close once the pressure has fallen to below 90% of it's maximum setting. Failure to allow the relief valve to close will result in excessive overheating of the system. This often comes about where the operator is using one of the smaller powered machines in grass at higher speeds than should be used. In most cases this will conclude the test for the pump, however if the relief valve is under suspicion then the same test should be conducted without the relief valve in the circuit and the results compared. Care should be taken not to over pressurise the pump as damage will result.

The motor is now the next major component to consider. It should be noted that the other components should be tested out before moving on to the motor. The motors fitted to Bomford Turner products fall into four categories.

"B" Series machines - gear motors with built in check valves for dual rotation.
"B" Series machines - piston motors built for dual rotation.
"LR" Series machines - all motors are built for UNI- rotation only.
"S" Series machines - early models had separate bleed lines for dual rotation - later motors, 1990 onwards, may have motors with built in check valves for dual rotation.

There are various methods of testing the motors efficiency but as we have varying standards of motors we will adopt the safest method that can be used on all types of motors. It should be noted that in instances were no drain line is fitted any pressurisation to the return line will blow motor shaft seals.

The hydraulic test unit should now be placed into the return line of the circuit as below. 
Ensure that the test unit loading valve is wide open,

With the tractor engine stopped, stall the rotor drive. This can be achieved by using a large timber post securely held between the rotor, cowl and the ground. It is important to secure the rotor firmly and safely before progressing further. It should be noted that wedging the rotor with the direction of rotation will draw the post into the cutting head locking the rotor. This is the correct way of stalling the rotor. Under no circumstances wedge the rotor against the rotation of the rotor.

The tractor engine and PTO should now be engaged and increased to the rated speed. Gradually engage the motor drive circuit. Naturally the relief valve will blow at it's pre-set setting. The oil flow through the stalled motor is the motors "slippage" and hence it's inefficiency.

e.g.  an 84 litre system with the relief valve set at 207 bar.

Oil leaks through the stalled motor at a rate of 8 litres per min.

This calculates as an inefficiency looks likes this. 8 * 100 / 84 = 9.5%


  Oil leaking through the stalled motor at a rate of 18 litres per min.

This calculates as an inefficiency looks like this. 18 * 100 / 84 = 21.5%

Again, as with the pumps acceptable efficiency much will depend on the work the machine is doing. However, anything above 15-16% should be considered a poor reading and a motor change should be considered. Overheating will result with an inefficient motor just as with a worn pump. It is possible to gain some idea of a motors performance by using a tachometer direct onto the rotor shaft. This is known as the free air turning speed. Again the PTO shaft must be set to the correct speed and with the pulley guard removed, place the tachometer direct onto the rotating rotor shaft. Readings should be taken with the pulleys set in their fastest condition i.e. large pulley driving small.

The nominal rotor shaft speeds are listed below.

"B" series machines 

"LR" series machines 

"S" series machines 

3000 rpm

2400 rpm

2600 rpm

A poor motor will show a reduced rotor speed, unfortunately this method is not reliable and does not relate to any efficiency figures.

Fig. I


In the lower graph we can conclude the following:-

( 90 - 20 ) x 100 / 90 = 78%

By all accounts a very poor pump output at 78% deficient. The upper line is the result of a test conducted on a good pump. It is therefore apparent that the area contained between the two graphs is the area representing the pumps deficiency.

In the upper graph we can conclude the following:

( 104 - 92 ) x 100 / 104 = 11.5%


These tests are the very basic tests that any technician should know in order to asses the condition of one of our hydraulic flail units. There can be other influencing factors which may lead the technician onto the wrong track. For example; a slipping tractor PTO clutch, poorly sealing suction hose allowing air to be drawn into the circuit, a crushed suction hose and water in the oil, probably as a result of condensation or reckless pressure washing the tank top, or any other contaminant. Return line filters on their own are seldom a reason for poor performance. However long term neglect of filters will cause expensive premature wear of major components. When filter elements become blocked they by-pass un-filtered oil. This by-pass valve is set at a low pressure (1 to 2 bar ) so cannot contribute to any power losses. It should be noted that these systems are seldom totally sealed. Those systems with twin pumps, the second pump being used to power the rams, can by the very nature of the working ram draw small fragments of contamination into the system. Our filters are designed with enough capacity if regularly changed to accommodate this. However a blocked filter does not filter at all. Filter change intervals should be implemented at the following intervals:

1st filter change at 50 hours. 
All future changes at 500 hours.

It should be noted that neglected filter changes contributes to something like 80% of all the hydraulic problems encountered. A fact that should not be ignored.


It is expected that the following information is used for the purpose it was intended. The information is intended to be used by qualified Technicians who will not only be able to interpret the recorded data but who will conduct the tests in a safe and workman like manor. We cannot emphasise enough the use of sound safety practices.

EPP Controls

The EPP controls fitted to Bomford machines vary only in the amount of on/ off services needed for each different model.

All control boxes have 2 proportional services that are controlled by a single lever joystick. These services are used for the lift and reach rams only. The remaining services being operated from rocker switches and will vary in number depending on the number of services on the machine.

Consider the points of the compass. The joystick functions are out of phase by 45 degrees. The lift & reach rams and the speeds at which they move, are dependant on how far and at what angle the joystick is moved i.e.; If the joystick is moved to 45 degrees then only one ram (lift or reach) will move at the speed determined by the position of the joystick. If the joystick is moved straight up & down or left to right then both the lift and reach rams will operate together in a direction, and at a speed determined by the position of the joystick. The speed at which both rams move together can be altered by biasing the joystick more towards one service than the other.

With practice both precise and parallel movements will come naturally and with far less effort than conventional cable operated systems.

The rocker switches on the control box operate the remaining services which are "Bang"-"Bang", or on/off spools that are NOT proportional.

Depending on the model, these switches being; cowl ram, head float, slew ram, and telescopic arm ram.

Other extra services may include, rotor on/off, arm float, power turn table, & slew lock out.

The EPPII control system has passed all the EMC (Electro Magnetic Compatibility) tests. This ensures that no stray radio waves wander off and interfere with other electrical components.

EPP Controls - Trouble Shooting Guide

EPP Mk1 Boxes are rectangular and white in colour.

EPP MkII Boxes have a moulded arm rest incorporated and are two tone grey in colour.

1) All controls will not operate .

a) Disconnect power lead from control box and test for voltage at power lead plug.

b) Power at plug - Go to 2.

c) No power at plug :- Check battery terminal connections.

d) :- Check terminal connections in plug.

e) :- Check fuse and replace if faulty with identical type (15 amp).

f) :- Check continuity of power lead to check for break in wire.

g) Replace power lead if found to have break in wire.

2) Power at power lead plug but all controls will not operate.

a) No controls :- Check terminal connections of control box power lead socket.

b) :- Remove control box lid (EPP Mk1) or control box base (EPP MkII), and check that the small amber lamp is lit when the power lead is connected and the main isolator switch is set to ON.

c) Lamp will not light - If the lamp is not lit then check the 2 fuses on the circuit board and replace as necessary with identical types.

Fuse FS1 = 15 amp

Fuse FS2 = 1 amp

d) Check operation of the main isolator switch & replace if necessary.

e) No controls - Fuses are found to be OK but lamp will not light - Check continuity of control box power lead for break in wire.

f) Replace power lead if found to have break in wire.

g) No controls - Check that there is power at the dump valve connections (Pink & Black wires).

h) Power at dump valve connections but valve will not operate - Remove solenoid and check operation (magnetises when power is applied).

i) Operation of solenoid is OK but dump valve will not work - Replace dump valve.

j) No power at dump valve connections - Check continuity of wires in loom.

k) Lamp lights but no controls - Carefully inspect the circuit board for signs of damage or burnt out tracks or components.

l) If damage is found replace circuit board.

3) Rocker switch services work but no controls from joystick work.

a) On MkII boxes make sure that the joystick terminal plug is plugged in.

b) Check the joystick terminal connections on PCBoard (EPP Mk1) or the terminal connections on the plug of EPP MkII.

c) Check proportional output at solenoid connections of wiring loom as follows;

The proportional signal wires to be checked are :-

Red/White & Red/Brown - 1st Ram.

Red/Black & Red/Blue - 2nd Ram.

Test the output from these wires one at a time as follows;

1) Remove a signal wire and connect an Ammeter capable of reading up to 5 Amps between the terminal pin on the solenoid and the removed wiring loom terminal.

2) Switch on the control box and move the joystick to the corresponding position for that ram movement.

3) The readings should be:-

a) 0.7 Amps when the joystick is at its minimum movement and the relays are first actuated, - and 2.7 Amps when the joystick is moved to its full extent.

b) Repeat this test for the 3 remaining signal wires and note the outputs.

c) Replace joystick if there is no output.

e) Check the circuit board for signs of damage and replace if necessary.

4) Rocker switch service(s) will not work.

a) Remove the 2 wires (one coloured & one black) from the solenoid which normally operates the service and connect a Volt Meter to the 2 terminals.

b) Switch on the control box operate the switch and check the voltage, it should read approx. 12 volts.

c) Check operation & continuity of rocker switch and replace if necessary.

d) Check the continuity of the wiring loom and replace the loom if necessary.

e) Check the circuit board for signs of damage and replace if necessary.

In the event of a service not working, or complete electrical failure, it is possible to move the arms by manually activating the solenoid valves. This is done by simultaneously pushing in the rubber caps on the end of the dump valve ( the only single ended solenoid valve) and the relevant spool valve. Pushing the dump valve spool will cut the flow off from the tank and cause the system to charge with pressure allowing the rams to move when the associated spool is depressed. Pressing the spool valve on it’s own will not work as the dump valve will be open, and the flow of oil will go straight to tank.

We can carry out electric control box refurbishment and repairs including, switch, joystick and PCB replacements.

We can repair PCB’s or supply and fit exchange item’s where down time is sensitive.

All units are fully tested and carry a 6 month warranty on all replaced/repaired parts.

Twitter Tel: +44 (0) 1789 773383 - Fax: +44 (0) 1789 773238 - Email:
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