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The Tropari borehole survey instrument operates with a clockwork mechanism which simultaneously locks a plumb device and a magnetic compass which gives the inclination and the direction of the borehole respectively.

The instrument is set to lock by means of a timing ring calibrated in 5 or 10 minute divisions.

After the set time consisting of lowering time plus 10 minutes for locking has lapsed, the locked instrument is retrieved from the borehole and the direction and the inclination at the test depth can be read.

Testing at specific intervals will allow a plot of the borehole to be constructed, and any part of the borehole to be located in three-dimensional space. The accuracy of the plotted position of the borehole will depend on the distance between the test sites and the sensitivity of the instrument used.

Tropari - Setting Time

a. If the rod draw of the drill rig can accommodate the entire length of the survey train, the whole survey train can be lifted and eased into the collar as a unit by the wireline or other cable winch. The timed Tropari is inserted into the container just before the survey train is lowered into the hole.

b. If the survey train has to be assembled in the collar, then rods with hitch pin holes can be used to safely join the elements of the survey train in downward holes. In this case, the timed Tropari is inserted into the container before any assembly begins.
 

• Unthread the sections of the container and remove the two (2) rubber shock absorbers.

• Make sure that the  shock absorbers are dry and resilient- if not replace them.

• Containers marked 2E take 12.7 mm thick (½ inch) shock absorbers - those marked 3E take 19 mm thick (¾ inch) shock absorbers.

• Place one below and the other above the Tropari.

Estimate the time required to lower the Tropari to the test depth in the borehole.

Add to this:

    a) the time required to place the Tropari into the container

    b) tighten the container join with wrenches

    c) position the survey train for lowering and

    d) ten (10) minutes for the locking cycle.

Usually steps a) to c) take five minutes or less, depending on how the survey train is assembled.

Hold the Tropari in your left hand.

• Using the index finger and thumb of the right hand, gently move the knurled timing ring so that the setting mark on the ring turns to the left.

• If the gimbal has locked at an angle that makes it difficult to reach the reach the timing ring with your fingers, use the capstan bar in the holes on the timing ring as a lever to set 10 minutes of time. This releases the protractor pin so that the gimbal can be rotated to a position for easy access to the timing ring.

• Turn until the setting mark coincides with the desired amount of time. In practice, the setting mark must be turned slightly past the desired timing mark because of a small amount of backlash in the mechanism.

To check the amount of time set, turn the timing ring slightly to the right and then gently to the left until resistance to further movement is felt. The setting mark will read the operating time remaining. This test of time remaining can be used whenever a check is needed.

When the time has been set, return the timing ring to extreme right- failure to do this may prevent normal operation of the Tropari.

A side view of the inner frame showing the distinctive 5 and 10 minute marks on a model 201 Tropari. The model 211 has only 10 minute marks. Single dots on the scale represent 30 minute intervals - double dots 60 minutes.

Using a watch or a stop watch, record the time at which the Tropari is set to lock. A ticking sound will be heard if the Tropari is held close to the ear. If the back-ground noise interferes, after a minute or two check the remaining time by turning the timing ring to the left as described in section 3. If  several minutes have lapsed since the Tropari was timed, the Tropari is running.

• Look at the compass card- if it hasn't dropped to a free floating position after more than 10 minutes of timing has been set, tap gently on the crystal (glass cover) until it drops.

• The gimbal must also be free to swing on its pivots.

• Remember that if less than 10 minutes of time has been set, the Tropari is already in its locking cycle and not all the freedom of normal movement will be available.

• Insert the Tropari into the container so that the arrow on the outer frame points into the borehole.

• Place the Tropari between the shock absorbers and tighten the container as firmly as possible using arm leverage of one box wrench working against the other. Pipe-wrenches are not advised- they destroy containers.

• The survey train, once assembled, is ready to be lowered or pumped to the survey depth.

• When the survey train approaches the end of the hole or is near the bit in "through the bit" wireline surveys, slowing the descent rate to reduce impact is advisable.

• In "through the bit" surveys, the drill rod train is raised 10 meters or 30 feet so that all the survey train can pass through the bit.

• Once the time set on the Tropari has passed with the Tropari having been stationary during the last 10 minutes, the survey train can be retrieved.

• Wipe the assembly free of water that could enter the container and wet the shock absorbers or the Tropari once the container is opened.

• If condensation on the Tropari is a problem, consider methods of warming the container before it is opened.

The inclination of the borehole is read from the the tooth into which the protractor pin locked. The protractor is marked in distinctive 5 and 10 degree intervals with teeth at 1 degree intervals. The inclination reading is made by counting the number of  degrees the protractor pin is from the 0° (horizontal) mark. The 90º inclination marks can be viewed  through slots in the inner frame.

Use the relative position of the protractor locking pin and the arrow on the outer frame to determine whether the borehole was inclined upward or downward.

For clarity, The Tropari inclinometer scale is illustrated here without any weights, which would obscure one half of the protractor from view.

With a weighted inner frame, inclinations to the left of the diagram would be read from the other side of the inner frame.

The magnified diagram at the top right shows a detailed view of the teeth and the protractor pin.

The "heading" or azimuth of the borehole relative to magnetic north is read from the compass by determining the degree value which is locked at the index line.

As with all compass based borehole surveying instruments, the reading must be corrected for declination.

The azimuth (relative to magnetic north) and the inclination reading will remain firmly locked until the Tropari is reactivated by turning the timing ring.

Magnetic Cake Effects

Drill rods rotating in the hole frequently deposit a grease-rock powder-steel powder cake on the walls of the borehole. This cake is frequently magnetic and affects the azimuth readings of all compass based instruments. We recommend that surveys be carried at the bottom of the hole as drilling progresses for the most accurate results.