AotPR part 5 - more bits

A few more bits turned up this week, bringing total expenditure up to around £400.

Items coming through the letterbox included: two timing belts and associated pulleys, some more aluminium profile, more t-slot nuts, half a dozen angle brackets for the alu profile, assorted capscrews (screws with hex-driver heads) and a BIG needle-roller thrust bearing for the main mount.

Picture-wise, we've got some photos of the bits, plus the construction for the 'yaw' motor assembly.

Bits

Timing belt and pulley, with LEGO gear and beam for scale.

This will be used for the pitch control, replacing the 'winch' pulleys seen in part four. Timing belts and pulleys are pretty good at transferring high torque, low rotational speed power without slipping, making them ideal for this purpose. The pulleys are aluminium but the large ones are still bulky enough to weigh around 400g each, and will probably end up with quite a few holes drilled in them for weight reduction.

The smaller (ten tooth) timing pulley in more detail.

Note that the bush that had stuck out on one side has been removed with a hacksaw.

Needle roller bearing in place on one of the larger pulleys.

This will be the main bearing for the rotational movement of the head. The pulley will have a Manfrotto hex plate fixed to it for tripod support. The panohead will then sit on the bearing, held in place with an axle through the middle.

Second view of bearing and big pulley.

After the pulleys arrived, I went online and found a roller bearing just the right size to fit over the bush on the pulley - but I didn't realise that the bearing came without spacers/washers, so I'll have to sort out some kind of flat plate to go between the bearing and the alu profile.

Timing pulley with insert to fit LEGO shafts.

In another of those nice coincidences, I discovered that shaved down LEGO spacers happen to fit very snugly into 6mm bore holes. Add glue and you're done. :-)

Yaw Motor Assembly

Yaw motor assembly from below, attached to alu profile, with big pulley roughly in place.

The first attempt at this didn't turn out too well, unfortunately I forgot to take any photos before disassembly. But that brings up one of the main reasons for using LEGO Mindstorms in the first place - it's incredible for rapid prototyping and testing many different ideas.
Anyway, the first one was far too wobbly - this one is based around an angle bracket bolted onto the alu profile and is very rigid.

Yaw motor assembly - side view

Yaw motor assembly - close-up

In this image you can see one of the bolts that holds the LEGO firmly onto the angle bracket. The angle and position of the LEGO was carefully adjusted so that there will be very little sideways force on the beams, as they are not very rigid against bending actions.

Timing pulley with LEGO shaft insert, in place with LEGO gear and timing belt.

I don't really trust the torsional strength (resistance to twisting in non-jargon) of the LEGO rods, so in addition to the insert inside the pulley I will probably be fixing the pulley directly to the gear which will be driving it.

The last of the smaller bearings and capscrews should be turning up in the next few days...

Ian