V-2 with wings rebuild 2021

Simon, I wasn't criticising, just wondered if the shaft was brass, may be the cause of the failure was the steel was to hard combined with some sort of imbalance, wouldn't take a lot for a over tightened grub screw to cause a stress fracture on high carbon steel..

Paul
It was a ready assembled EDF. I never disassembled it or even knew that there was a flat on the shaft.
I notice many of the current fans use a 'cone clutch' type of adapter similar to a conventional prop driver which is rather a better solution from a fatigue point of view.
I have no way of knowing what broke first but loosing a blade(s) would put a huge imbalance on the shaft that could well have caused it to fail particularly as at take off I was over rating the EDF by nearly 100% using a 4s instead of its rated 3s! :ohmy:

Simon, if you disassemble the motor to its component parts I think you'll that a flat has been cut into the shaft wherever there's a grub screw fitted.
When I make a replacement shaft I use Silver steel shafting and file the flats on, the edge of the file leaves a rounded corner, unlike a slot drill that will always leave a potential fracture point.

Slowly destroying a bit more of the V-2.:woohoo:
I have removed the original "magnet" wires from the ESC to the motor. Each is 870 mm long & 1 mm diameter. The three together weigh 23 g. They will be replaced by 0.7 mm wire. Although it only has 2/3 of the cross section it will only be carrying 1/4 the amps.
I have repaired & sorted out the rear end ready to fit the 4" EDP.



but before it is permanently 'built in' I want to try the 4 x 4.5 3 blade prop. Once the EDP is in place it will require serious surgery to change the prop!

" They will be replaced by 0.7 mm wire. Although it only has 2/3 of the cross section it will only be carrying 1/4 the amps. "

That does seem awfully thin, but I guess at under a metre the resistance will not be very high & the load is split across three phases. Out of interest what will the maximum load be ?

crash
As it stands at the moment for the VTO it will take 15A from the battery. No idea what the peak in each motor might be. For normal flying I would expect it to use less than 1/2 that, say 7A, 110 W.
My latest weight guesstimation is 450 g (1lb) all up.

The repairs to fuselage formers is slow going.
The original ESC to motor wires and the snakes ran individually through the formers which worked very well but the VTO current was so high the wires actually warmed up, softened the Depron so the wires could migrate a bit. One actually moved and touched the top rudder snake and being plastic it softened that too jamming it solid.
It all took a bit of fixing but the result was a small section of each former was quite severely disrupted so it very much a 'make do' repair.
This gives an idea of the state of some of the formers.

Indeed in many cases it is only the skin keep the shape.
When I originally built the V-2 in 2016 I was very conscientious and put a 1/32 balsa strip all round the inner edge of each 3mm Depron 'ring' former.

This does not make any repairs to a former particularly easy and even more so when having to wok through a limited area of removed skin.
The major formers in area of the wing made good.

As I have no idea where the CofG will end up using the much lighter components I will continue to restore the formers but leave the skin openings as is.
As the nose is likely to have nothing in it it will be built complete using printed formers to save Depron and glued in place before siting the components to achieve the required CofG - except I don't actually know where it was! :woohoo:

"warmed up"? must have got nearly red hot to jam a adjacent snake! looked at a chaps edf (8s hawke)model over the weekend, all the wiring was in pure copper and was massive,quite expensive apparently, wish I'd taken a picture now, it was all very clever and sophisticated.

Paul
After the wire softened the Depron, 80 degrees C is enough, it moved across and was actually pressing on the snake which was an all plastic lightweight job.
It is quite possible for domestic power wiring to reach that sort of temperature. :woohoo:

The 4" EDP installed in the partly restored airframe.

As expected it is entirely supported by the fins.

The object was to measure the thrust by standing the airframe on a set of scales.
With a 'storage level' 4s it generated 535g thrust.
Not really enough so I might have to go to a 5s or even 6.

Anyway, build the nose next and see how much it weighs.

Today's progress.
Building the nose.

My usual wobbly start that relies on 'eyeball' rather than geometry.
The nose on.

Next 'difficult' job is installing the ESC to motor wires. The exact position of the ESC will depend on the battery position and that in turn will depend on fitting the servos (once they arrive!) and the control surfaces in place so the CofG can be set.
I shall have to look through all my pictures to see if I ever recorded its position.
.

Christmas competition. With the leading edge of the wing at the fuselage as the datum, where is the CG on Simon's V2 ?
Is that puffy Lipo still available as a prize ?

I can only guess.... is it where the leading edge meets the wing end plate? Oh instead of the puffy Lipo can I have the one that went swimming please?

I think I know where the CofG needs to be but unfortunately I can't get it there without using a big battery. :ohmy:

Even with a 1000 mAh 4s absolutely right in the nose the CofG it would only be just be right and that would be without the 4 servos and control surfaces which of course go right at the back. Then the problem is made worse by the fact I would like to use an even smaller & lighter 650 mAh 4s battery. :woohoo:

Clearly things have got to change.
I spent last night thinking of all the possible solutions but first I removed the nose I had just fitted before the POR set too hard.

So far the options appear to be:-
1. Go to 5 or 6s to get more thrust to allow a bigger heavier battery. It would need a new ESC. In addition neither the motor or prop are rated for more than 4s.
2. Move the servos well forward of the CofG to counter the weight of the control surfaces. The lightest way of doing this is by using pull/pull lines.
3. Move the motor forward (it is the heaviest single item after the battery) although the 4" prop is already about as far forward as it can be and remain within the fuselage profile.
4. Replace the printed duct with a lighter Depron alternative.
Or possible do all 4!

Still thinking.

Extend the nose, maybe ?