700xn

[RichardV]

Interesting looking pinion arrangement.

[mahbouni]

Interesting looking pinion arrangement.

I' sure they could have squeezed one or two more in there

[crash-test-tomo]

Knowing align gears I bet that will sound amazing in a couple of months

[chrisleematt21]

Maybe they moved the engine forward to fix a CG issue? Perhaps to late for a complete redesign or perhaps they wanted to keep as many standard parts as possible.

Would it cause any kind of power loss having to go through the extra gears?

Its a nice looking heli, might wait until the next version though

[crash-test-tomo]

Doesnt look as though the engine would have cleared the tank without them. They have obviously thought about CG though as the tank is directly beneath the main shaft

[bigpops]

Prototype pics showed the tank further back. It wasn't under the main shaft, like its competition.

So, there was either a CG issue (tail heavy due to moving the servos away from the front), or they wanted to put the tank under the main shaft for better CG.

[Grumpy]

The idler gears are to fix a tail heavy CG. Moving the tail servo into the nose might have been a better option?

[coolice]

Hey.

Interesting concept that's for sure, it's been done to relocate the tank under the main shaft. This way as the tank empties, there is no real change to the models centre of gravity which is handy.

Don't think it is, but looking at the photos, is the engine/start shaft angling away from the head to put more room between starter and rotor head? Difficult to tell with the raked skids. Not sure it is looking at the photo again.

I'll be keen to hear the mechanics in flight, as I'm sure it'll be a little noisier due to the gears. Back when I flew at a club going through noise complaint issues, without their canopies on to stifle the gear noise the heli's were slightly louder in the hover.

Ian Contessa

[aww]

Alan Szabo Jr testing
https://www.youtube.com/watch?v=136uxFsiIzQ
Anthony

[Grumpy]

I couldn't hear any unusual gear noise in the viseo. The plastic housing may do a good job of absorbing any noise? I'd be more concerned about the longevity of the gears and the tiny bearings they run in. Spinning open to air at 15k RPM+ I cant imagine either the gears or the bearings will have a long life. Time will tell I guess.

FWIW the prototype of the 700XN which was shown about 4 months ago didnt have the idler gears, it just had a convention direct pinion to main gear drive with the tank and engine further back. Align revised the design 'at the last minute' and apparently (according to those who claim to have spoke to the Align development pilots) was primarily to fix a tail heavy CG found on the prototype. The RX battery on the prototype hanging way out front is probably a sign they were fighting a tail heavy CG. Getting the tank on the CG is a benefit too for sure.

Here's the prototype pic:

[Hei1950]

It fairly safe to say the engine centre line is parallel to the main shaft otherwise you would have some funny gear set.

[coolice]

Morning Grumpy.

Sadly a tail heavy 700 wouldn't be fixed by moving the tail servo to the front, it's a miniscule weight movement considering the boom length.

You may find that the data you've read is right regarding the C/G issues, but it was caused by the fuel tank, as in the photo you've posted it is behind the main shaft.
Thus when full it makes the model tail heavier and as it empties, the C/G shifts forward again, so not ideal.

Move the engine forward via the gears, to allow bringing the fuel tank to under the main shaft and during a flight from being full to almost empty, the centre of gravity doesn't change.
Electrics don't suffer this affliction as the battery weight is constant so it is positioned to obtain the right C/G position and doesn't change throughout a flight unlike their IC cousins that empty their tanks.

It all adds up, move the engine forward to bring the changing weight (fuel tank) to under the mainshaft so it's doesn't effect the model in flight. At the same time use the forward mounted engine to counteract the tail gearbox weight on the models C/G.

Gear noise, will be good to see one first handy to fully know. A video can't really pick that out usually.
Knowing Align the bearings will probably be quite big.
I'm sure Duncs got one, but not been to the club to see it if he has.

I raised a question over the Align 2in1, a single servo connection to the Rx/FBL and the silly red JST plug to LiPo. Shame Align didn't uprate this a little more with a twin lead output, XT30/60 input plug and associated wiring and 10amps continuous output. Would have been the icing on a perfectly good Align cake that little update in my book.
But alas the Facebook experts couldn't see this ;-)

Ian Contessa

[waveydavey]

I think it looks lovely

[Grumpy]

Yeah Ian, You are probably right in that the tail servo alone wouldn't have been enough. It is unusual for a nitro to have the tail servo in that rear position though which is for CG considerations.

It will be interesting to hear how those gears and bearings stand up in service over the medium and long term. Due to them being a last minute addition to the design Align cant possibly have done any long term field testing.

[George J]

Align have have over complicated it and have just missed all the important stuff, ease of maintenance etc. CoG on this MAJ custom Trex is bang on with a 3500 pack up front so I don’t see why they’ve had to push the engine forward, just no need.

The plastic clutch stack in the old Trex was rubbish so will be interesting to see how the gearbox on the new XN performs over time.