EQ6 - HEQ5

[hidra]

[barberanm]

Hola, hidra.

Aquí te suelto un muerto que también puedes leer en el grupo http://groups.yahoo.com/group/HEQ5:

HEQ5 EVALUATION

Alan Buckman, AWR Technology 16th Nov 2003.
alan@buckman-hardy.co.uk
www.awr.tech.dial.pipex.com

Mount on loan from The Widescreen Centre, London for the duration of the evaluation.


ACCESS TO THE INNARDS / MOTOR REPLACEMENT

1. Remove 6 black cover plate screws (M3 x 6) over body of main casting. This cover moulding allows access to the motor adjustments and the spur gears.

2. Remove 4 off countersink bright plated screws and remove U-shaped plastic moulding containing the polar scope TOP entrance. This reveals the connectors on the circuit board.

3. Undo the 6 way and 4 way connectors which are together on the circuit board. Remove the two motors by undoing four screws on each motor mounting plate. (Why don’t they use spring washers to help in alignment / securing when in position?).

4. Screw on new machined cover plate.

5. Add new motors and slide in mounting slots until the gears mesh properly – this is not visible but has to be done by feel.


MEASURED SPECIFICATION

· Max loading 30lb (manufacturer’s specification)
· By measurement the slow motion shaft over 6 cycles – 10m 37.8s per rev at position 1
7 cycles – 10m 38.7s per rev at position 2
135 teeth is exactly 10m 38.3s sidereal
· Brass spur gear on slow motion axis has 72 teeth diameter 43.2mm (MOD 0.6) therefore one tooth travel every 8.86 seconds at sidereal rate.
· Brass spur gear on motor / gearbox has 54 teeth diameter 32.0mm (MOD 0.6)
· Main worm gear 135 teeth by calculation compared to EQ6 and new gear ratio assuming the motor is driven at the same step rate for sidereal. This is correct.
· Both motor mounting plates are identical.
· Slow motion axle, steel dia 9.0mm in standard radial roller bearings
· Slow motion end float adjusted by adjustment ring accessed on rear underneath rubber cover.
· 12V DC supply, centre positive required. Standard DC power connector 2.1mm
· Polar illuminator not fitted.
· Manufacturer’s control box up to 16x sidereal. Same as used for EQ6 drive. Motor drive rate is identical to EQ6 and gearing compensates for different worm wheel teeth.
· Main backlash adjustment is by moving worm in relation to worm wheel by same fittings as used on the EQ6 mount. This adjustment can be done without any interference from the motor fitting.
· Adjustment of mesh of motor spur gear may remove only a small amount of backlash.

LIKELY VARIABILITY BETWEEN UNITS

· Watch out for Periodic Errors of periods 8.86 seconds (tooth to tooth on the spur gears) and 638.3 seconds (one revolution of worm in main wheel). These result from quality of mechanical components (or lack of it) and adjustments. Both periods at sidereal rate drive.
· Backlash caused by mesh of worm with worm wheel. Body will rock slightly. There should be very little rocking and it should be an equal amount over all parts of the main wheel. You need to drive the worm over the complete wheel to find this out. It is possible to over tighten this adjustment causing a huge amount of force needed to turn the slow motion axle. 0.1mm of ‘rock’ causes approximately 0.1 degrees of movement in the sky and the worm adjustment bolts are out by about 0.29mm
· Backlash caused by end float in the worm axis. Same effect as mesh of worm with wheel and the body will rock slightly, but you will be able to feel the end float of the slow motion axis change when it is rocked. 0.1mm of end float is about 0.1 degrees in the sky – 24 seconds of backlash, so it needs to be much better than this.
· Backlash caused by spur gears not engaged enough. Solution is to move the motor slightly using the four mounting screws. You need to check that this pair of spur gears are not binding at any point in its rotation. This will suck power from the motor and leave a smaller amount to drive the telescope. Note this adjustment is not critical as the standard gearbox will have about 2 degrees of backlash in its output shaft. This corresponds to 0.3 teeth rotation on the spur gear (and 2.6 seconds of backlash), so any mesh better than 0.1 teeth is good.

POSSIBLE IMPROVEMENTS

· Thrust bearings at both ends of the RA slow motion axis should stabilize the end float and not cause premature failure of the slow motion axis roller bearings. This is the most critical cause of overall backlash problems assuming everything else is in reasonable adjustment. If it is done up as tight as needed without adding thrust bearings then the roller bearings will suffer as they are not designed for axial loads. Several pounds (up to 5lb?) of thrust will be present on the thrust bearing with a fully loaded telescope.
· Thorough clean of all gears, checking with a jeweler’s loupe that there are no hard deposits at the bottom of each tooth, removing with a knife if there are.
· Re-align all the adjustments. Needs a complete strip down to align the worm and wheel correctly.
· Addition of illumination for finderscope.
· Driving existing motors with third party equipment. Note the gearbox output of the original motor / gearbox is about 80Ncm of torque and hence about 90Ncm on the slow motion axle.
· Replacement of motors with AWR Technology HEQ5/KIT for GOTO operation. Motor driven in microstep mode eliminates the gearbox and hence no backlash from this cause.
· Replacement of spur gears with toothed drive belts should reduce any high frequency periodic error.



Un saludo

[hidra]

[barberanm]

Hola barberarm.
Con mis limitadisimos conocimientos de Ingles no consigo entender si los 135 dientes pertenecen a la corona de A.R. orijinal de la EQ, ni si el tiempo de 1 rotación del bisinfin es de 10m 38.3s.
Me confunden otros datos que salen como por ejemplo, de donde salen los 72 dientes, los otros 54 dientes, los otros 10m 38.7s y los 10m 37.8s.

De todas maneras muchas gracias por la molestia.
Saludos.

Intentaré hacer algo, pero aunque tengo una HEQ5, no me he dedicado a contar dientes

By measurement the slow motion shaft over 6 cycles – 10m 37.8s per rev at position 1

- 10m 37.8s es el periodo de rotación del eje a la salida del motor (va muy reducido internamente). No sé a que se refiere el texto con los 6 ó 7 ciclos

135 teeth is exactly 10m 38.3s sidereal

- Número de dientes de la corona del bisinfín

· Brass spur gear on slow motion axis has 72 teeth diameter 43.2mm (MOD 0.6) therefore one tooth travel every 8.86 seconds at sidereal rate.


Número de dientes del eje del bisinfín (la HEQ5 tiene dos piñones y un sinfín. Uno de los piñones es el del eje del motor - 54 dientes - y va acoplado a otro piñón en el eje del sinfín -72 dientes)

En resumen, la transmisión sigue la línea: motor - reductora - piñón de 54 dientes - piñón de 72 dientes - sinfín de 135 dientes, para, a final conseguir un período de la corona de 135 dientes de un día sidéreo (23 h 56').

Un saludo

[hidra]