Technical / FAQs

# = no. of stages: 3 or 4 or other on application
3 stage has outer plus 1st, 2nd and 3rd inner legs
4 stage has outer plus 1st, 2nd, 3rd and 4th inner legs
AABB = closed and extended lengths
e.g. 1023 - closed height is 1000mm; extended height is 2300mm
1332 - closed height is 1300mm; extended height is 3200mm
1746 - closed height is 1700mm; extended height is 4600mm
M =
Motor size: 70 or 95 70 = low torque motor
95 = suits low pressure supply, uses more air

note: normal air pressure is nominal 100psi [7 Bar], low air pressure nom.
70 psi [5 Bar]
CCCC =
gearbox ratio

1142 [11:42] = high torque/lower speed
1439 [14:39] = low torque/higher speed

NOTE: high torque motor is not available with high torque gearbox

A typical part description would be: R/B TM MAXI 3/1436-95/1439.

This indicates roof bolter, Top Mount, MAXI leg unit as compared to the standard leg version, 3 stage, closed height of 1400mm and extended of 3600mm (1436) [floor to top of chuck], 95mm air motor [other option is 70mm] and a 14:39 gearbox - this is our high speed unit compared to our high torque gearbox which has a 11:42 (1142) ratio.

The most popular styles of machines are MAXI, 3 stage and 95/1439 motor gearbox combination.

The standard leg is a smaller diameter leg. The MAXI leg, as the word sort of indicates, is physically a larger leg in diameter. Using the equation F=P/A [force equals pressure divided by area], the larger the area that our 100 psi is impacting on the greater push or leg force that we'll get. If rigid roof bolts are going to be installed a standard machine is fine. If larger and longer cable or mega bolts are used go for the MAXI unit. Some times as an owner of roofbolters it also makes sense to standardise on one type to reduce spares holdings.

There could be basically 3 causes for this:

The control rod operating the leg raise lower function is out of adjustment. This can happen when the units have been in service for a period and/or the handles are used regularly to torque up the roof bolt nuts. The following diagram shows the elevate and water controls on a T-Bar roof bolter control arm.

When the elevate lever is operated you should hear the bleed port, on the side of the pivot block letting air out. This will stay ON until at about 135° and will stay off from 135° to 180°. With this adjustment set-up leg dump or retract will be optimized.

Refer to the maintenance manual on procedure to adjust.

The dump valves in the headpiece are not operating correctly. This could be due to too high a viscosity oil being used, excess oil, water and foreign matter in the valve ports creating limited operation/performance of the valves, too low an air supply pressure or the valve diaphragm rubbers being worn or U/S.

The dump valves have been tightened too tightly into the dump valve block. Turn the square headed recessed bolts ½ to 1 turn anticlockwise [loosen them].

If a) , b) or c) don't solve the problem it is likely that there may be a blockage in the porting on the machine and a further, detailed investigation might be required.

It can be said that too much oil is as bad as too little oil. In fact for the RAMBOR machine(s) oil is basically only required to provide some lubricant for the gears in the air motor. As far as valves, etc. are concerned, sometimes the oil causes 'more problems than it solves'. Nevertheless if the right grade of oil is used and IN THE RIGHT QUANTITY then you will have no problems. The typical qty of oil feed is 1 litre per 75 bolts based on a 5 minute drilling time per bolt and the grade/type of oil could be standard rock drill oils that the major suppliers offer - e.g. Castrol BIO BOLT, BP-E Rock Drill oils, Castrol Rock Drill oils - RD series.

The oil needs to be of a low viscosity type. Our literature recommends an SAE 20-30 grade [approx. = ISO 100KV].

NOTE: DUE TO THE DIFFERENT VISCOSITY OF OILS IT IS IMPERATIVE THAT LUBRICATORS ARE ADJUSTED CORRECTLY. Adjust and check before using. If this is not done your machine will get overoiled and cause valve and seal problems due to dirt/muck coagulating with the excess oil. The RAMBOR exhaust unit is such that any oil vaporization is greatly reduced or minimized by the use of foam pads within the muffler. The foam "catches" any air borne oil which then 'liquefies' out of the muffler.

The following describes the features/benefits of the key "building blocks" of a roofbolter. Some of these elements can also be applied to other RAMBOR products.

MOTORS: 2 main types, the 70mm and the 95mm motor. The 70mm motor is best suited to sites that have constant and good air pressure of 100 psi. The 95mm motor also prefers 100psi but will be able to perform in a similar manner as the 70mm motor at pressures as low as 70 psi. The 95mm motor also provides more power than the 70 mm motor.
GEARBOXES: Again 2 main types - the 1142 and the 1439 [the 11 & 14 being the primary gear tooth number and the 42 & 39 being the secondary gear tooth numbers]. The 1142 gearbox is our high torque unit where as the 1439 gearbox is our high speed unit. The 1142 g'box is only coupled up with the 70mm motor. The torque generated if we use the 95mm motor and the 1142 g'box would be excessive and potential difficult to operate. The 1439 gearbox can be used with either the 70mm or 95mm motors. Refer to individual spec sheets to determine torque, speed and other parameters for different combinations.
LEGS: Our standard Leg combinations range from a 4 stage 0821 [800mm closed height/2100mm extended height] to a 3 stage 1746 [1700mm closed height/4500 extended height]. The 4 stage units allow a much smaller machine for the same extended height if a 3 stage machine was selected. This is critical in low seam applications and the lengths of drill steels that can be used. For larger seam mines the most popular choice is the 3 stage machine. What ever machine type is selected it is good practice to make sure that the top of the machine is able to reach the roof of the seam, possibly with a little extra height in reserve.

We are able to make any variety of Rib Drill however the industry standard, to ensure the safety of operators, has limited the torque on the units to 68 Nm or 50 ft-lbf. This can be compared to a RAMBOR roofbolter, which has typically in the order of 250Nm stall torque.

There might be several issues that could cause this -

Standard things to check are low air pressure or reduced CFM or l/min of air capacity - is someone using the air outbye or nearby, is the supply hose kinked, etc.
Foreign material in the motor - dirt/dust/water
Excessive oil in the compressed air. Due to the close tolerances of the motor gears, if there is too much oil being introduced with the compressed air the gears will tend to bind. There will not be enough clearance for the gears to spin correctly. Check to see how much oil seems to be coming out of the exhaust. If this area appears very oily you may have found the problem
If the motor gears have excessive wear a proportion of the compressed driving air will effectively by pass the motor. This results in a loss of efficiency and lower power. This problem is usually characterized by the motor spinning at normal or high revs. but lacking any power under load
The bearings in the motor, the bearings in the gearbox and/or gearbox jamming may also be the cause of the problem. Is the unit noisier, does it appear to spin OK on no load, has there been excessive water evident in the air lines?

The best people to speak with are the resin and bolt manufacturer's and suppliers. But in summary some of the key points are:

The ideal hole length typically should be 50 - 60mm shorter than the bolt. This may need to be modified depending if other plates or washer types are being incorporated at the threaded end.
The correct hole diameter needs to be drilled - the suggested difference between hole diameter and bolt should be within the range of 4 - 10mm.
The hole needs to be "true" for the chemical or grout securing to be totally effective.
When using a wet drilling technique in soft roof reduce leg thrust but use increased speed. For the same wet technique, but in hard roof, increase thrust but reduce speed.