E5 -- optimal tail gear ratio for 556/96?

[curmudgeon]

I understand that Matt recommends running the tail between 9,500-10,000rpm for a 606/96 blades.  I really enjoy the 1:4.5 tail ratio on my 12S E5s running 606/96 blades with HS 2,150rpm yielding 9,675rpm on the tail.

I am about to build a stock E5 to run 556/96 blades on 6S.  I have the gears to go with either the stock 1:4.0 ratio or the optional 1:4.5 ratio.  Ideally, there would also be an in-between option of 1:4.25, but there isn't.

Please, help me achieve an optimal setup for my current sports flying skill level trying to progress to more aggressive 3D.

1) What range of main rotor governed HS should I consider when running 556mm blades with a heavy 5A battery for my flying goals?  This would help me in figuring out the optimal pinion to use.

2) I understand that running the tail much lower than 9,500rpm starts to compromise tail authority.  How about the other extreme?  What happens if I run the tail much higher than 10,000rpm?  What sort of detriment should I expect, and how significant is this detriment?

[Chris Sexton]

I run 2350 with my 5a packs and get 5 minutes of sport flying. With the stock 4.0:1 tail ratio.


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[curmudgeon]

At 2,350rpm HS, the tail would be spinning at 9,400rpm with the 1:4.0 ratio.  With the 1:4.5 ratio, the tail would spin at a whopping 10,575rpm, which I would think would be too high and cause unnecessary vibrations, wear out parts prematurely, and be less efficient due to drag?

So, if I understand correctly, when using the 96mm tail blades with the 606 main blades, I should keep the HS lower, and the tail ratio therefore higher (1:4.5).  However, when using the same 96mm tail blades with shorter and lighter 556mm main blades, I should run the main blades faster, and therefore keep the stock 1:4.0 ratio since the 556mm blades will create less torque than the 606 blades?

[Rodney Kirstine]

I run mine as a 6S 550.  I use the stock gearing with Rail 556 mains, Rail 96mm tails, and either 2250 rpm  or 2450 rpm head speed.

[curmudgeon]

So the vibe I am getting is to keep the stock 1:4.0 tail ratio when running 556/96 blades, and don't go with the 1:4.5 ratio.

[Rodney Kirstine]

That would be my recommendation.  Matt designed the stock E5 to be a 550, after all, before designing the parts to stretch it.

[BrianE]

That would be my recommendation.  Matt designed the stock E5 to be a 550, after all, before designing the parts to stretch it.

To be fair, the E6 boom and E7 spur gears came first - Matt just designed the E5 to use either the stock parts or the E6/7 parts.  Also, the E5 was designed from the beginning to use from 6 up to 12S batteries so the stretched version was not an after thought.

[Rodney Kirstine]

My wording may not have been absolutely spot on but I think that it is fair to say that the parts that come in the box when you buy an E5 are optimized to be run as a 6S 550, which is what John is asking about.  At least, based on average head speeds and the stock gearing, that's what it would suggest to me.

[Chris Sexton]

It's a torque issue. The smaller disk creates less torq for the tail to counter.


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[curmudgeon]

In the video, Matt ran the E5 with 556/96 blades and 1:4.0 tail ratio at about 2,500rpm HS.  That would yield a tail rpm of 10,000.  Since I am planning on running a lower HS, I just want to make sure that I choose the appropriate tail gear ratio.

[Chris Sexton]

I would think you would want to error high. You aren't going to be drastically over the ideal speeds and certainly no where near too high for the blade integrity.


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[curmudgeon]

Chris.  It seems that you are steering me towards the 1:4.5 ratio.

I am planning on using the 13T pinion.  With the 1100Kv motor, the calculated sweet spot is between 2,337rpm and 2,430rpm HS.  I am planning on starting out with 2300rpm and 2400rpm HS.  With the 1:4.0 ratio, that would yield 9,200rpm to 9,600rpm tail, respectively.  However, with the 1:4.5 ratio, those head speeds would yield 10,350rpm and 10,800rpm for the tail.  Ideally, an optional 1:4.25 ratio would yield 9,775rpm and 10,200rpm.

So, for HS between 2,300rpm and 2,400rpm using the the 556/96 blades, which tail ratio would be optimal, 1:4.0 or 1:4.5?

[flyalan]

I run my E5 6S at 2250 and 2350 with the stock gear ratio and 96 tail blades. The tail holds fine. No issues. Matt recently flew my E5 and aside from an elevator bobble (fixed :-) ) he had no complaints.


Cheers
Alan

[curmudgeon]

Thanks Alan.  It is reassuring to know that you can run the 556/96 blades at HS of 2,250rpm with the stock 1:4.0 tail ratio (yields 9,000rpm tail), and not have any tail issues.

[Rodney Kirstine]

Thanks Alan.  It is reassuring to know that you can run the 556/96 blades at HS of 2,250rpm with the stock 1:4.0 tail ratio (yields 9,000rpm tail), and not have any tail issues.

But it wasn't reassuring when I said it, ten posts ago? 

That's OK, I wouldn't trust me, either... Lol