SARCNET rotator build

One of these days I will have to start doing portable satellite operations. I found this project on the SARCNET website and decided to adapt it to my needs. I have very little experience with mechanical constructions (especially using metals), so their complete design for their MK-II rotator was a great guidance.

Materials used

Bearings

I could have bought these bearings locally, but when doing research on the web I found that Banggood had both the bearings and motors + controllers, so I bought all in one go.

The pillow block bearing with 25mm bore was US$5.09.

The flange bearings, also with 25mm bore were US$6.96 per piece and I ordered three of them.

All of them weren't aligned properly. By putting a rod in them and then using a square I carefully nudged them so the core was perpendicular to the outer rim.

 

DC motors

The DC motors were also bought from Banggood. They're 12V 2RPM Reversible High Torque Turbo Worm Geared DC Motors and they were US$9.87 each. The gears are sweating a little bit of oil, but nothing major.

 

 

 

 

 

 

Sprockets, chain and chain connectors

These were especially made for me by a local business in the next town of Zhongli. The chain is type 25 and the big sprockets are 25x32 with a 1" bore, the smaller ones 25*10 with a 6mm bore. I chose a 1" bore for the bigger ones because at the time I didn't know if I could find 25mm tubing. With a shim made of an old can they will fit 25mm tubing just fine.

I paid NT$200 for the 25*32 sprockets per piece, so US$13.5 in total.

The 25*10 sprockets were NT$140 per piece, so US$9.50 in total.

Ten feet of type 25 chain was NT$200, so US$6.50.

In total, with tax, I paid US$31.00.

 

Aluminum tubing

This were the trickiest parts to get. It was impossible to get 25.0mm tubing of any kind (alu, stainless, fiberglass), so in the end I got these two 60 cm pieces of alu-tubing with an 8mm inner diameter and 25.4mm outer diameter. With the help of BX2AB I found a metal workshop where they could be machined down to 25.0mm. The added cost of that was staggering: NT$500 per piece of tubing (US$16.50). Luckily I didn't have that much money on me when I collected them and the owner was in a good mood, so I emptied my wallet and only payed NT$600 for both of them (US$20), because that's what I had.

Cost of the material: 2x NT$250 (US$16.50 in total).

Labor cost: NT$600 (US$20)

 

 

 

 

 

H-bridges

Banggood had an offer for three LMD18200T H-bridges, which the SARCNET project also uses. I paid US$25.52 for the three and all three didn't work. The quality of the whole assembly also wasn't that great, so I counted it as a loss. Wrote a negative review on the Banggood website, but they ignored it. So I went to al local electronics store and bought an LM298N H-bridge for US$6.30 and it worked flawlessly. Later on I bought a second one from my favourite local Arduino webshop for less than US$2, so in the end I spent far too much on these rather simple circuits.

 

Enclosure

This was also a major purchase. Bought from Nonstone in Tainan for NT$1368 or US$45.60. Product number is FT202015, which means a 20x20x15cm IP66 outdoor enclosure. Very heavy, because it is all thick steel and in Taiwanese fashion not 100% perfectly made. They don't have any stock of these enclosures, so it took a three week wait before I got mine deliverer by courier.