Sunday, 31 May 2015

Tricopter updates

Having established that I could build and fly a tri it was time to update to decent quality components.

I bought carbon fibre arms, power distribution body (with onboard BEC) and tilt mechanism with Blue Bird digital servo from 

Prices are very reasonable for these excellent components and postage is only US$7 from Sweden, better than most Australian outlets.

David's tricopter parts are almost works of art, especially the 10mm square woven carbon fibre arms.

From HobbyKing I bought Hextronic DT750 motors and some Turnigy Slow Fly 10x4.5 props.

Hextronic DT750 motors

I need to share my experiences with these DT750 motors. They are well suited to tricopters but do have some design faults which need to be dealt with first.

ESC wire support
The 3 wires are not flexible, just continuations of the single core windings, and will break with bending and vibrations. To prevent this they must be supported around the base with big blob of epoxy glue. I used 5min Araldite and it worked well.

Motor shaft "pull-up"
The shaft is about 40mm x 4mm and threaded. In theory you don't need a vibration inducing prop adapter, just a nyloc nut. BUT unfortunately the shaft is not rigidly fixed to the motor bell. Tightening the nut enough to stop the prop slipping pulls the shaft up through the motor bell. This increases the bearing friction making the motor heat up and draw more current. The shaft is only held in the bell by one tiny grub screw, which is not enough to resist the "pull-up" from the prop nut.

I had some nasty crashes caused by a slipping tail prop because I couldn't tighten it down enough. Broke an arm and ruined an expensive digital servo.

The solution is to put a nut onto the shaft right down to the unthreaded part, then a washer, prop, washer and nyloc nut. That way the prop doesn't push down on the motor bell. Unfortunately I had already cut the shaft too short before I discovered this problem so have had to resort to bulky 4mm prop adapters.

Quest for the best propeller
Turnigy Slow Fly 10x4.5 props are OK but very thin and flexible.

10x5 Gemfan Carbon nylon Graupner copies from Banggood are much stiffer but less efficient giving shorter flight times.

Emax 10x4.5 props from Banggood are a bit stiffer than the Turnigys and may be the perfect choice. Testing continues.

1 comment:

  1. The ideas and strategies was very informative given by you.

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