3w Extra 330s precision IMAC setup help.

[crhammond]

At the end of last season I bought a 40% 3W Extra 330s in "almost new" condition from Bryan Armstrong. The plane really was flawless and I flew it about 20 times before the snow flew.

In total the plane had about 40 flights on it. I came with a mixture of 8611 and 8611a servos. After 40 flights most of them have slop. The plane was set up for 3D as per the 3W manual: 1.5" arms, H9 clevises set back from the hinge line (at least 1/4” back) and 1.2" control pivot height from the hinge line.

The current setup uses Fromeco 5200 MAH packs, a PowerBox Champion and a Futaba 5014 G3 Rx. DA150 on cans. 39lbs dry weight.

Now I am setting the plane up for IMAC next season. I have the following objectives:
Keep the weight down as it flew fantastic at 39lbs.
Replace the 8611's with 5955's (I am a 5955 guy – I HATE maintaining servos.)
Replace the Seiko servo and battery with 2 x 8711's to increase precision (and maybe reduce weight.)
Use A123 batteries with no regulators.
Use an RRS so I can have 2 5014 Rx's OR 2 6014 2.4GHz Rx's - for my own piece of mind.
Replace the Powerbox with a Smartly Power Expander Sport so I can run at 6.6v – plus it is lighter than the Powerbox which is not needed when using programmable servos.

So far I have been working on the geometry for the ailerons. I have installed one servo using Dubro hardware which puts the pivot directly over the hinge line. I have the pivot 1.5" above the hinge line and a 1" MLP arm on the servo. This allows 30deg of throw which is still plenty. So far this setup seems much smoother and there is obviously a LOT more leverage for the servo. The linkage stays parallel to the servo case for most of the travel too. Am I on the right track here? Is there anything else I need to take in to account?

My plan is to stick with 2 x 5955 per aileron. With my new setup the servos will have FAR more leverage plus the voltage will be at 6.6v VS 6.0v so I am expecting much better control authority.

I plan 1 x 5955 per elevator half.

The Seiko has TONS of power but it requires a 3-cell LiIo pack of it’s own and it is REALLY heavy. Plus it does not seem to center that well (although I have read the case can be “vented” to make this better. My plan is to use 2 x 8711 in an Airwild servo tray. At 6.6V I think this will provide enough torque. Am I right on this?

So those are my plans – but I have been doing some second guessing as I read a few threads where people are going with 3 servos per aileron and 2 per elevator half… and 3 x 8711 on rudder. That is a heck of a lot of power and a heck of a lot of extra weight.

I think just with the changes I have planned I can save 1lb off the plane (mainly in battery weight and 4 oz from the Powerbox.) Not that weight is an issue... but I sure would like to avoid going up in weight.

[whaturi]

My opinions..

If you are reducing throws to maximum needed for IMAC, I think the setup you mentioned sounds just right. You are giving a lot of mechanical advantage back to the servo by using the shorter arms. Just because some people use 3 per ail and 2 per ele and 3 per rudder does not mean it is the only way. I say go with it and spend some real time getting the throws correct and matching your multiple servos for zero binding. With 5955s, that will be much easier throughout the entire range of travel compared to the 8611s.

[krayzc]

I think your set up sounds very good. Do keep us posted on how that set-up works. I am looking at changing a 40% Extra to this type of set up in the coming years.....

[crhammond]

The difference on the bench is ASTOUNDING. I set the newly setup wing next to the old. The resolution and centering on the new setup are far, far better. It also seems to have much better torque just by the movement. The old setup struggled to support the weight of the aeroperfect meter - the new one has no problem at all holding it.

I took my time and there is no binding or buzzing of the servos at all. I set the dead-band's to 1 as well on both servos!

So far I am glad I took the time to do this.

I'm not 100% sure about the A123 setup... I have a PowerBox Champion installed already and it likes a high voltage battery. I might switch to LiMn or I might switch to a Smartfly unit that has no regulators (the Pro version.) Since I am using 5955's I don't need a power box with programming... it's hard to switch out somehting that already works though. Another option is no power system at all - the RRS can handle the voltage and current; however, it does not do any filtering or servo-lead voltage compensation. I am leaning towards using the Smartfly with the RRS. Combined weight would be a little less than the current setup and I would run 6.6v without regulators. I could save about 4oz in batteries too.

Just changing the servos, using smaller arms and 1/2" shorter linkage saves about 1oz per wing... not much but at least the weight is not going up. I also added some weight because I re-wired the servos (directly off the boards) to use 20 guage wire. I don't like connectors

[crhammond]

I just did a bench test with 2 x 6014 FASST Rx's and the RRS. Wow - I think this will be a very light setup that will work fine. The resolution on the 6014's is just as good as my G3 seems to be.

Here is a diagram of what I propose. The main reason for the Power Expander is because it has the smart-switch to protect against a bad battery and it isolates power to the Rx's; also now there is no need for regulators or servo matching.

The RRS will allow my to place the Rx's at different locations and orientations. Hopefully if the 2.4 signal gets lost on one the other will still be good (kind of like having a satellite Rx on Spektrum...)

[green@3D]

looks like a great setup Chris. I think a lot of us typically "over servo" then again, better too much than too little. Rough math says it will work though, I mean 3 servos for a 1.5" arm, 2 servos for a 1" arm, call me crazy but the torque you lost on the 3rd servo is made up by the shorter arm. I will have to check that plane out this summer once you get it up and going.


Do you have a new home for the riggin from the old plane, I happen to have a good home for it all. I don't mind JR servos either, they seem to work fine for me.

Later


Brian

[crhammond]

Brian,

There were only 2 servos per wing before... and with the 1.5" arms they were probably not enough - although the plane flew just fine for sequences. In fact it flew great... so I expect it will probably just be more precise now.

I don't have a specific home for the servos yet. Some of them need new gears though so they'll need to go back to JR first. PM or email if you'd like to make an offer I have 6 of them, 4x8611a, 2x8611.

Also 6 very nice double-lock 1.5" arms and 6x3" H9 Ti pro links with hardware if you're interested in that too.

[383chevelle]

Another way you could go would be to use a emcotec DPSI RV twin. It will condense the powerexpander and RRS into one unit. check out emcotecs web site. I think that they get overlooked sometimes. Thay make great products and have alot of protection features built in. The protection from a bad battery, draws the batteries down at the same rate, and has visual and audiable alarms when something happens.

Just food for thought.

[crhammond]

Well - my servo change went very successfully and now that the snow is melting big time I am working on changing a few more things for this season. Specifically I am replacing the heavy Seiko setup with 2 x 8711's in a tray which although less powerful should be enough power for IMAC and also be more precise.

I did a lot of weighing tonight and came up with some very interesting numbers!

Here is the setup from last year:
Old ignition pack 7.60
Old Rx pack TBM 5600 8.70
Old Rx pack 8.70
Seiko 11.00
Seiko pack 5.20
Regulator and switch 2.00
Powerbox 5.70
Total: 48.90 oz

Here is basically the same setup with fresh batteries and the 8711 setup:
2x8711 tray setup 8.20
Fromeco 5200 7.00
Fromeco 5200 7.00
Ignition pack 3.30
Smoke pump 4.00
Powerbox 5.70
Total 35.20
Savings: 13.7oz!

Now - if I am willing to go A123 and use a Smartfly instead of a Powerbox:
2x8711 tray setup 8.20
A123 2300 5.80
A123 2300 5.80
A123 2300 5.80
Smartfly 2.60
Kodiak 0.80
Kodiak 0.80
Smoke pump 4.00
Total: 33.8
Savings: 15.1 oz

So my inclination is to stick with my LiIo packs and keep the extra capacity. The A123 setup would run at a higher voltage for a bit more servo power.

As far as the RRS goes I am thinking I will stay with my single Rx setup (although it will be on 2.4 FASST.)

Combined with the weight savings in the linkages and a few other things I should have not only a more prescise powerful setup - but also be 1lb lighter!

[krayzc]

good info...

[mflander]

What are you replacing the seiko with?

[crhammond]

2 x JR 8711's in an AirWild servo tray. That all-up is 8.2oz. The Seiko and 3-cell battery were 16+oz's.