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Home✈️Aircraft🚁Helicoptere-AlignOther › New Trex 450 help please
07-17-2006 10:13 PM  14 years ago
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darenh

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Hull, UK

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New Trex 450 help please
Hi all

Just in the final build of my new Trex 450x CDE, that's the CCPM version with push pull controls on 2 of the servos.

A few questions if anyone can assist me.

What size servo arm are you using on the 2 push - pull servos. I have already put arms on but they are going to be to big and catch on the canopy? (how far out are the balls, I'll cut the arms down perhaps)

My battery is a 2100mha 18C pack it all so looks a little to long for the canopy when offered up, do I have to hack the frames slightly to gain extra room?

Anyone installed a battery tray for support?

Wheres the best place for the RX and the ESC/control, has anyone found?

There are a few pics of the Rex's arms and battery in my gallery(just uploaded them) just to show what I am getting at.

Thanks in advance guys this will probably save me a bit of time trial and error - ing. So I can get it ready for set up for when the connectors arrive.....


"Im out woodworking right now"
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07-17-2006 10:27 PM  14 years ago
caseyjholmes

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Portland, Oregon

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some of this might help you =)
http://www.runryder.com/t272212p1/
It's basically the same for the CDE accept for your "balls" problem. Mine rubbed on the canopy a little bit on my CDE, but I cut the servo arms down some and didn't notice it. They did rub on the canopy a SLIGHT amount, but if it is major you gotta do something about it.
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07-17-2006 10:30 PM  14 years ago
aircare84

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Marysville,OH

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The servo arms hitting the canopy on the plastic frame Trex is an old topic, do a search here & you will see some solutions. Some people mount the ball on the inside of servo arm, some cut clearance holes in canopy, heat & form canopy, etc.
I've used 12mm & 14mm length on my servo arm length, but that does hit the canopy. I cut holes.
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07-17-2006 10:33 PM  14 years ago
JVheli

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Milwaukee,WI USA

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Maybe this picture will help. I had the same prob on an xl.

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07-17-2006 10:44 PM  14 years ago
glucoseboy

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SF, CA

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I resorted to just cutting the canopy in order to make room for the arms and links.

It's a quick fix and you can't see it when you're flying!
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07-17-2006 10:53 PM  14 years ago
c mark smith

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Mt Vernon, Indiana

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When ever you run dual arms and dual pushrods between them, the arms and rods must form a parallelogram or a rectangal.

Otherwise there is a binding as the whole thing moves off center in either direction.

Both rods and both arms need to be respectively parallel to the other one.
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07-17-2006 10:54 PM  14 years ago
extreme3d

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West London, UK

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Hi Daren,

I have just used the lower links of the push pull mechanism due to the canopy interfernece problem. I have not found this to cause a big problem (but it has been talked about here, on this forum plenty of times).

The battery tray on my Trex was an upgarde for I think a Zoom heli (can't quite remember) just secured in place, after drilling a couple holes in the main frame and securing with tywraps, and then with battery velcro straps.

The gyro is placed between the frames for protection, but can still be accesed from the top. The reciever and esc are mounted on oposite sides of the frame as far away (inc the wiring) as possble from each other.

Check the pictures out in my gallery.

Enjoy!
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07-17-2006 11:05 PM  14 years ago
Boidman (RIP)

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The Home Stretch

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When ever you run dual arms and dual pushrods between them, the arms and rods must form a parallelogram or a rectangal.

Otherwise there is a binding as the whole thing moves off center in either direction.

Both rods and both arms need to be respectively parallel to the other one.
Servo arms parallel - yes. Pushrods the same length - yes. Pushrod ends mounted the same distance from the center of rotation on each arm - yes. Isosceles trapezoid - yes. Parallelogram - no.

Edit to retract:

My statement is completely wrong. c mark smith, is 100% correct.
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07-17-2006 11:45 PM  14 years ago
Boidman (RIP)

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The Home Stretch

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c mark smith, boy did I screw that one up. I apologize, sincerely! I was completely wrong. Oops.
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07-18-2006 02:38 AM  14 years ago
c mark smith

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Mt Vernon, Indiana

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Back to Geometry 101 for you,,,,,,,,,,,

It is easy to see the problem, just disconnect one of the link, just one end, then move the servo thru the full travel.

The link will match the ball at just one point, needing shortening and lengthening at the extreme travel positions.

I kinda do linkage design as part of my ultralight nusiness so linkage is pretty important,,,,,,,,,,,,,,

We do spend most of the time at the middle so servo effort is only a biggee when off center a bit. The battery drain is pretty high when this happens, and now that I think about it, I'd bet a 3 amp BEC might have a serious voltage drop as the servo gets in a real bind at either extreme position. Could lead to all manner of 'glitvhing' and 'cut out' problems, masked by a host of choices made picking components and parts layout.

My HDE has dual arms on the ailerons servo.
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07-18-2006 07:33 AM  14 years ago
darenh

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Hull, UK

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Interesting, I have push pulls on my Raptors and SE but as extreme3d has done, do I really need these push pulls on such a small but precise - ish machine.
And as c mark smith says if I am slightly out with my geometry over these sort distances this will have a detrimental effect on my battery life (let alone the ESC current handling capabilities), which is one of the reasons I opted for this particular model. (CDE + electrics pack).

Thanks the replies so far.

"Im out woodworking right now"
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