12" Giant Field Tripod Modifications (Classic and GPS Versions)

The original Meade 12" Giant Field Tripod was unmanageable in its standard form for portable activities when it was fully loaded with the Meade Superwedge.

It required a stepladder as part of the kit when carrying out any observations with the 10" LX200 pointing anywhere from +10 degrees to near the horizon.

And, the added problem of lifting the tube into the Superwedge during set-up and dismantling.

After careful consideration, assistance from the Loughton Astronomical Society, and messages to MAPUG, it was decided to reduce the height of the tripod by approx. 8"

The legs are made up of two steel concentric sliding tubes with two alloy moldings, one for the tube height adjusters/clamps, and one for the tripod head pivot point.

The tube height casting also has a pivot point for the leg spreaders/tensioners.

The castings are heat and glue sealed to the outer steel tube.

Assembly of these units is probably carried out using a heavy-duty press system during manufacture.

All the modification work has maintained the original angles of 60 degrees and 30 degrees to keep the rigidity, damping factor, and loading, to at least, the original design.

In fact, the lowering of the platform has increased the first two points by approx. 10-15%.

Notes:-

1. The legs are chrome plated steel and are easily cut to the required length. The 19.25" distance is between the two alloy castings. Allow the extra length, when cutting, that will be glued and pressed into the top molding on re-assembly.

2. The spreader distance of 14.5" is between centres. The end of spreader that was shortened has to be machined/shaped to match the original. The material is Aluminum. Paint the modified end with mat black enamel to match the original finish.

3. On re-assembly, align the top casting pivot points to be at right angles to the spreader pivot/leg extension lock screws.

Modification Actions:-

1. After removing the legs from the tripod platform, use a padding material and grip the leg in a 'workmate' type vice.

2. Apply heat via a blowtorch to the tripod pivot casting using a rapid circular movement. The surface finish will not be affected if this is carried out correctly.

3. After 40-60 seconds, use a drift rod or alternative implement, in the casting boltholes to twist the casting off the leg assembly. This will not require undue force as the applied heat should be sufficient to release the glue bond. Expansion of the aluminum to the steel will also allow movement.

4. Clear the inside of the casting of all surplus adhesive.

5. Now cut off the required length of the outside leg, ( approx. 8"), keeping the cut at rightangles to the tube at all times, clearing off all burs. Chamfer the edge of the cuts to aid re-assembly. Please check measurement to confirm the outside length between leg castings to be 19.25".

6. Check and clean all work surfaces before re-assembly, and that all the legs are the same height.

7. Mix up a sufficient quantity of standard epoxy resin glue, smearing it over the top of the tripod legs and the insides of the casting. (It is recommended that this action be carried out one at a time, and don't 'make haste')

8. Place the casting onto the leg tube and gently hammer home. Use a soft material, like wood, between the casting and the hammer.

9. Maintain the casting position to be at right angles to the adjustment casting using a drift in the casting pivot holes.

Allow to dry before reassembling the tripod.

Fine Level Adjustment Platform (Under Construction)

This project has been a development from a concept proposed by Brian Brooks of AstroParts UK

The beginning of prototype stage.

The idea was that the top bracket in the photo be secured to the base casting of the tripod fixed leg by it's two pressure screws. Then, after rough leveling adjustments, the bracket to the right of the photo was secured to the adjustable leg via hose clips..then the final adjustment carried out by utilizing the screw thread linking the two units. Finally tightening all tripod bolts.

The above diagram with the bubble levels. A conventional level on the left in comparison to a digital level on the right. A very high degree of level adjustment can be achieved with this setup.

The completed components ready for assembly onto the tripod.

As can be seen when comparing the original suggestion, a change of plan was made concerning the positioning of the smaller bracket to save space and to prevent the lower hose clamp becoming detached from the modification.

The larger hose clamp was used to affix the long bracket to the main tripod leg casting while the 50mm smaller unit was used to clamp the adjustment plate to the lower section of the tripod leg.

A closer detail of the adjustment section. Note the foam rubber base to protect the chrome finish of the lower leg of the tripod.

The smaller of the two brackets was clamped to the extender leg of the tripod via a 50mm hose clamp after rough leveling, the final adjustment carried out by adjusting the nuts while observing the digital bubble level. The tripod legs were clamped as normal after setting level.

The completed assembly.

The modification has proved to be very easy to use in the field, requiring no more that five minutes to set up a very accurate platform. The digital level has a setting that allows a tone to be emitted when the reading reaches 0.0 degrees.

Notes:-

After a number of field trips it was decided to increase the length of the adjustment screwthread by a factor of 2 as stated by Brian Brooks of AstroParts in his original concept. No other changes have been made.

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