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shogo
08-29-2009, 11:56 PM
Hi folks, rcmarty alerted me about 3dx head giving too much cyclic throw using the stock 30 mm ball distance on the servo horns. I should admit that it didn't occur to me that this might be a problem when I used the standard Quick UK 700 servo discs with 30mm ball distance. When I checked the cyclic range, I was getting a whopping 18 degrees on the aileron/elevator!

So today I changed all my cyclics to a stock futaba servo horns that provides a 21 mm ball distance (Quick UK discs don't). Cyclics are now at +/- 12 degrees on aileron/elevator and when I dial the collective to the max (120%) in the vbar software, I can get 18 degrees collective range - plenty!

Do you guys think that +/- 12 degrees on the cyclic is a reasonable range?

cbdane
08-30-2009, 10:37 PM
Hi folks, rcmarty alerted me about 3dx head giving too much cyclic throw using the stock 30 mm ball distance on the servo horns. I should admit that it didn't occur to me that this might be a problem when I used the standard Quick UK 700 servo discs with 30mm ball distance. When I checked the cyclic range, I was getting a whopping 18 degrees on the aileron/elevator!

So today I changed all my cyclics to a stock futaba servo horns that provides a 21 mm ball distance (Quick UK discs don't). Cyclics are now at +/- 12 degrees on aileron/elevator and when I dial the collective to the max (120%) in the vbar software, I can get 18 degrees collective range - plenty!

Do you guys think that +/- 12 degrees on the cyclic is a reasonable range?

That's exactly what I'm running wtih the Vbar using the 21mm spacing from the servos. It has worked great so far.

shogo
08-30-2009, 10:45 PM
great, putting the motor back in, hope I can try it this week.

rcmarty
08-31-2009, 07:15 PM
Glad my armchair observations were of some help.

I'm just about to get going on my 700n conversion with the 3dx head. I was thinking of going with 12mm but if your getting 12/18 on 10.5mm then that's the way to go.

12 cyclic is good , should make for a snappy heli. Motor might not like it much if your into the pitch also but it's easy and well within spec to drop a few points for 10-11 degrees.

18 collective is good also , dialing down to 14 or so is still going to give great resolution.

I dropped the head a bit on mine also , instead of putting the bolt in the stock hole i let the head sit all the way down and redrilled a new hold in the head. Loses about another 1/2- 3/4"

martin

shogo
08-31-2009, 08:55 PM
martin, that's good. Are you sure you will not get a tail strike with the head that low? It would for sure make for one evil looking heli.

cbdane
08-31-2009, 10:06 PM
I dropped the head a bit on mine also , instead of putting the bolt in the stock hole i let the head sit all the way down and redrilled a new hold in the head. Loses about another 1/2- 3/4"

martin

Interesting! Could you measure the approximate distance from blade center to boom center. Or to the top edge of the boom if that's easier. I'd love to compare.

Thanks!

rcmarty
08-31-2009, 10:56 PM
Interesting! Could you measure the approximate distance from blade center to boom center. Or to the top edge of the boom if that's easier. I'd love to compare.

Thanks!

I'll be about 1" lower than stock. Will have an exact measurement soon enough. I seem to recall a 1.25" difference over stock. I'll post back with some pics when it done.

Shogo . not to worried about a boom strike. I was following a thread about a lowered 600n head , this was so low that he couldn't go any lower because the anti bracket was in the way !

Of course you have to run stiff dampners and CF blades.

The thread went on to speculate that heli are designed for any type of blade/damper setups without strikes, so fingure soft (or soft and trashed) dampners with wood blades.

For testing this guy put a piece of wood i recall on the tail boom , then went a thrashed on it to see how much got munched. With cf blades and good dampers he didn't hit anything.

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I lowered the head on my Trex600 a little. The blades were 5.5 inches from the boom.

I wanted to lower it more but was concerned with boom strikes. So I made a gauge out of balsa wood that I zip tied to the tail right at the end of the blades. It went straight up and had notched balsa ply. The theory was that as the blades came in contact they would wack out pieces of ply. With the remaining pieces I could measure how much distance I had to play with before the blades made contact with the boom. The ply started at the boom and went up 4.5 inches, so there was 1 inch between the blades and ply before pieces would start getting wacked.

I did a couple flights and the blades never touched the ply. Stationary flips and inverted pumps I could not get any of the balsa to get hit.

This 600 had carbon blades and a head speed of 2040.

I am currently working on lowering the head more. However I am no longer concerned with hitting the boom, just the mechanics of it all.

Hope that is helpful.
Mike
-----------------------
Check out how low he's now !!
http://runryder.com/helicopter/t524374p1/

Martin

rcmarty
08-31-2009, 11:00 PM
I think i'm going to have to get it up and running first with the head dropped like i have planned , figure out the geometry (ball spacing) , then i can lower more as i'll know how much swash travel will be required.
The 3DX head is a tall unit as compared to the FBH unit.

martin

rcmarty
09-04-2009, 10:44 AM
I got to working of the 700 today.

The 3dx head is lower by 1"

Modded the stock align wheels for 11mm spacing.

Martin

rcmarty
09-04-2009, 09:13 PM
Got the conversion done .

some pics

Check out my file , let me know if anything is off

700N/3DX v-bar. Please check over for me. - HeliFreak

martin