FTF3545 Measurements:

*

The overall length is 27cm of flawless perfection.

You'll have to forgive the greasy fingermarks from lots of handling throughout the day. As I admired, measured, photographed and videoed the gorgeous thing. This thing is very big, incredibly impressive and its heavy! It will end up being dwarfed by my 8" main tube. Even though this model is often fitted to relatively small APOs for whole frame or DSLR imaging.

 
The focus adjustment knob diameters are as follows:
Gold Fine 31mm Ø. Black [2nd] Coarse 44mm Ø. Larger, fine adjustment focusing knobs are available from dealers in two sizes. Providing finer, manual focusing.

The projecting thumbscrew is the pinion shaft brake & lock.
The mass of the collar and drawtube housing is just enough to start descending under their own weight. A light touch on the brake screw holds the drawtube firmly with lots of variation in pressure depending on the applied load. Focusing is silky smooth from end to end of the 114mm [4.5"] of travel. The reason I chose the 3545 model.

The lone, coarse adjustment is slightly larger than the other at 44.5mm.

The pinion housing does not readily lend itself to fitting motor brackets. FT's own motors [and others] use a clamp onto the bare housing after removal the relevant knobs. My desire is for a combination of manual and electric focusing. Daft as it may be since I will lose positioning of the drawtube and precisely why I didn't want a stepper motor system.

The brake thumbscrew certainly can't be used for holding a motor bracket firmly in place.  It needs its range of adjustment to work as intended.

I'm very wary of using the central pair of rack housing screws too. It would be a disaster if these had to be specifically torqued to apply the correct pressure between the pinion and its rack. Best left well alone I think.

Another view of the rack housing area. I'm leaning towards a thick [10mm?] rectangular length of aluminium clamped around the housing and extending downwards away from the dual focusing knobs. One must carefully avoid marring the beautiful anodizing finish. Felt lined perhaps?

I'd really like to avoid an end of shaft, extended motor. Because I am loath to have such a dangerous projection from the side of the telescope. One would have to be extremely careful not to tear the motor off when carrying out a meridian flip, parking the OTA or slewing in the dark.

Click on any image for an enlargement.

*