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T-REX 700 › 700E setup question
02-18-2011 07:27 AM  6 years agoPost 1
MikeM

rrApprentice

Austin, Texas - USA

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Building my 700E and I've run into a setup problem.

I spent some time setting up my head today - by the book. At 0 stick I have centered servos/wheels/bell cranks, and the elev arm is at 90, swash plate is flat and level (used swash leveler). I have very little interaction moving the stick up and down from center so that's no problem it can be adjusted out.

My problem is that as everything is sitting as above at 0 stick, there is much less room above the washout than there is below the swash. Sure enough I can only get 9 or 10 degrees positive collective but negative pitch will go all the way out to 14 or 15. Mind you I don't need more than 10 or so positive (I think) but I want to set it up right and I think something is not.

I am expecting that at 0 stick the swash/washout should be in the middle of the the shaft. Isn't that correct? Shouldn't there be about equal space above the washout and below the swash so you can get about 13 or 14 degrees in both directions?

I know I can shorten my bellcrank - cyclic links and lower the swash. But that will cause my elev arm to bend to less than 90 degrees... Not ideal.

I must be missing something. What am I missing?

Thanks
Mike

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02-18-2011 08:38 AM  6 years agoPost 2
Taipan

rrElite Veteran

Sydney, Australia

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I remember having this problem with my 700E conversion that was flybar over 2 years ago. A few others also had the same. We solved this by trimming down the link that goes in the top of the elevator A arm and shortening the other 2 links from bellcranks to swash. This lowered the swash & washout. I got +-13 degs no prob.

Btw I recommend replacing all the links & balls with the Quick UK T-Rex 700 kit. I dunno if Align have improved the plastic that they use in their 700 links but when I first built mine using their links, the slop was so bad after 40 flights it blade fluttered severly! With QUK, they last heaps longer & less slop.

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02-18-2011 02:03 PM  6 years agoPost 3
MikeM

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Austin, Texas - USA

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Go figure. I thought for sure I was missing something. That sounds like a good solution I will try that shortly. And I'm ordering the QUK link set.

Many thanks.

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02-18-2011 03:55 PM  6 years agoPost 4
nickmcdonald

rrNovice

new lenox, il

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+1 trimming the links and lowering the whole assembly. Had to do the same on my 3G 700N.

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02-18-2011 04:51 PM  6 years agoPost 5
MikeM

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Austin, Texas - USA

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Before I try it, how much are ya'll trimming off the link? I'm thinking 1 or 2mm is all.

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02-18-2011 04:56 PM  6 years agoPost 6
nickmcdonald

rrNovice

new lenox, il

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Take a little off at a time. I don't exactly remember how much I took off. But it's worth taking your time and having to take more off, then having to get out the good 'ol link stretcher to make it longer.

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02-18-2011 08:42 PM  6 years agoPost 7
Richardmid1

rrProfessor

Leeds, England

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Remember to lengthen the links going to the flybar cage aswell to keep the washout base arms level.

60% of the time, it works every time!

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02-18-2011 09:15 PM  6 years agoPost 8
MikeM

rrApprentice

Austin, Texas - USA

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Remember to lengthen the links going to the flybar cage
Yes all four, thx.
Correction: I only had 15 or 16mm of travel, not 20. See post below.

Well I measured swash movement on the shaft. I have 20mm of travel to work with. So then at center stick the swash/washout needs to be sitting in the middle of that 20mm.

With the stock elevator arm at 90 degrees and center stick it puts the swash/washout 3mm too high. Looks like Align blew it on this. Anyway...

So first thing I'm doing is I shortened my 2 bellcrank/cyclic links by 3mm. And I'm just lowering the elev arm by 3mm with subtrim for now, just to see how it comes out. Then I can decide whether to try and shorten the elev arm link or get one and see about having it modified or what ever.

Actually I'm considering the possibility of taking 1.5 mm from the elev arm link and 1.5mm off the top of the elev arm. Is that what others have done?

The other question is, and I'm guessing what most people are doing is, just letting the elev arm hang down low, below 90 and living with it. As long as you end up with enough negative travel then I believe you only have to adjust for added the elevator interaction. Perhaps all you need is an extra 2mm and that's good enough to get 12 or 13 degrees pos pitch and that's good enough.

Oh here's an interesting question someone just PM'd me. What is the difference in length between the FB and FBL shafts? Are the identical otherwise i.e. same holes for jesus bolts and the extra 2 on top?

I bought the flybar combo 700E F3C. My shaft is 212mm long. Is that the correct shaft?

Thanks!

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02-18-2011 10:52 PM  6 years agoPost 9
MikeM

rrApprentice

Austin, Texas - USA

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Ok it appears that I do have the longer shaft at 212mm:

http://www.helihobby.com/html/trex_700e_parts.html

I wonder if I have some other part designed for FBL, like the elevator arm? Sigh...

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02-19-2011 01:01 AM  6 years agoPost 10
MikeM

rrApprentice

Austin, Texas - USA

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Correction: Wasn't quite as bad as I initially thought. I was measuring swash travel with the swash all the way down, forgetting to raise it for cyclic movement. Rookie mistake.

So once I realized that and went back and rechecked it all, my swash was only off by about 1mm.

So I did the drill of shortening the bellcrank-cyclic links by 1mm and lengthening the swash-mixer links by 1mm. And I am now seeing about 11 or 12 degrees of pitch. Much better and all I need, but I still thought you could get more than that. Probably if I tried harder I could get another deg or two.

So, that leaves my elevator arm just slightly off of 90 degrees at zero pitch. I rechecked my swash with leveler and it's perfect all the way up and down. I think I can live with the elev arm being slightly off unless someone can convince me otherwise.

Thanks!

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