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Archive for September, 2012
Posted by PeterVRC | Sep 24, 2012 @ 09:25 AM | 7,112 Views
Here is just a bit of bits and pieces about the A-10 Warthog from HobbyKing.
It is a twin 75mm EDF powered, 1017mm Wingspan EPS foam jet.
I have heard there are EPO versions? Maybe a more recent batch from the same moulds? But I am not sure.

Twin 75mm sounds powerful!!! But really, they are just "numbers". 75mm alone doesn't mean anything really... it could be driven by weak motors, low voltage, the blade pitch could be low.... so that it really has far less power than you might have thought.
And that is what they have done in this case - under a lame excuse of it having large fans to get more low end thrust. Which I guess is actually technically possible. And it might even be that it ends up as a more efficient way to do things - that is one thing that it seems to do from my assessment of that. It gets very good flight times for an EDF... but it is also a very weak, under-powered, plane!
And is at the cost of having huge nacelles, way bigger than scale. Looking a bit silly really.

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Posted by PeterVRC | Sep 19, 2012 @ 07:40 AM | 7,198 Views
Just a quick throw together of a Turnigy 2836-3200kv outrunner, into a CS10.

I always drill an access hole into the housing to allow an allen head drvier to get into the shaft adaptor grub screws.

I also always file two opposing flats onto the shaft adaptor to allow the use of two shifters (spanners), so you can do up the rotor nut properly. No force on the fan or motor, just on the shaft and nut like you technically should only do!

Most aircraft don't have the inlet lip on the fan when it is installed, but some do. And for bench testing you need it ON, so that the fan can 'grab' its full load of airflow - wthout it results will be WAY lower than they can do with ducting. I just use 4 pieces of fibre tape to affix the inlet ring for testing, each placed at 90deg around the fan.

BALANCE the rotor!! I static balance it first. Sometimes dynamic balance them.... but really SHOULD do that to them all. (Note: this post is 'old' now)
The balancer is a Turnigy carbon fibre heli blades balancer, disassembled and placed up an a wooden frame so I can do any rotor size, and also propellers up to about 14" or so.
For rotors I have mounted rare earth magnets so the balance shaft is suspended in mid air at one end, for zero friction, and the shaft has points ground on each end, so even the end that does sit against a magnet has near zero friction.
In a way that is TOO LITTLE friction, as the rotor can roll to a stop for the weeniest imbalance - which means less imbalance than even needed to care about. But you really gauge imbalance by how far it swings per 'rock' and how fast it 'rocks'.
Stuff small pieces of tape into the hub 'holes' between the strengthening ribs. And check again.....

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