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Alternative Layout – Be Creative!

An Alternate Tracker Layout

Imperial dimensions for use with 1/4 inch 20 tpi drive shaft @ 1rpm.

The Large Imperial version:

Similar profile to the Metric version, for exposures up to and beyond 60 minutes – say 90 minutes.

Drive Arm hinge – Drive Nut pinion / Drive Shaft centre = 16 inches; Drive Arm hinge – Contact Point = 14 inches; Drive Arm and Camera Arm hinge = 4 inches. Pack up the Camera Arm hinge with 2 layers of 80 gsm paper, because the uncorrected error after 60 minutes is half that of the metric version.

The Compact Imperial version (see Section 3 Acknowledgements – Tracker home page):

Indicates superior tracking up to 40 – 45 mins with no camera arm correction (packing up, as in the tracker design) and may be ideal for hand driven exposures of shorter duration. A computerised motor driven version should demonstrate exceptional tracking to 42 minutes – more than enough.

DA hinge – DN pinion / DS centre = 14″ ; CA hinge – CP = 12.92″ ; DA hinge – CA hinge = 1.9″. No packing is required. Calipers may be useful for measuring down to 1/100″. The alternate layout is recommended, because of the restricted dimensions between the CP and DN pinion / DS.

Resonance Damping – Motor and Drive Shaft?

Improved resonance dampers

Mounted on a tripod, the damping methods shown eliminate a large majority, though not all, of the resonance through the framework of the Tracker, operating almost silently.

The drive shaft damper and motor damper is made up of 3 washers and 2 layers of  elastic adhesive, sometimes known as Blutac or  Blutak ® (green in this case). The shaft end is pressed into the adhesive, but is not attached to the washers. Resonance is dissipated through the adhesive, as far as I know. The washers increase the edge density of the damper causing the adhesive to flex,  presumably, as in harmonic balancers, fitted to some auto engines. As a last resort, a disk shaped blob of adhesive, of similar size, will do.

Here’s a better approach to the suppression of resonance with the benefit of finer drive shaft resolution and increased torque – a Tamiya planetary gearbox – 5:1 in this case – use low resolution low torque steppers to good effect – no need for  microstepping (missed steps and low accuracy).

Tamiya plastic planetary gear-box

Here is a better method for attaching the motor shaft to the drive screw – explained on the Tracker page.

Plastic marker pen sleeve around inner plastic tube, press fit to motor shaft and threaded onto drive screw - as shown

Improved drive screw pinion – nylon collar with plastic tube insert with 6mm tapped thread – diminishes periodic error and resonance and reduces resonance.

Modified drive screw pinion