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Old Jan 22, 2013, 11:02 PM
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United States, TX, San Antonio
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Ken, Looking rad there... Now about that white stuff outside the window....
jt
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Old Jan 22, 2013, 11:03 PM
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Canada, ON, Owen Sound
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I've been sidetracked with hospital visit today. Got nothing done.
Ken, you'll have to explain how you did the video some day. It looks great, nice smooth action on everything. Nice job partner!!
Total movement at the push arm is approx 13/16" , thats why we chose a 130oz servo, going down is no real issue, but takes some serious power to pull up the gear.
As originally drawn, one servo centrally located and using bellcranks on 1/16" rods did this. Somehow I don't think that worked!!
Thank goodness for modern radios with adjustable travels, in this case it allows the servo to put the exact amount of tension on the diagonal arms to assure the overcentre lock stays secure, without any power being applied when the wheels are down. Wheels up is secured by the servo arm being slightly over centre parallel to the push/pull rod.
You can see this a little in the video. Again, no power applied when in position. When powered, the servos would obviously try to prevent movement from their settings, but are not using power in position. Seems to work well so far. The other "best" feature of the new TX's are the servo slows built in. Just need more channels right, maybe the new 18!! hehe. Doug B
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Old Jan 22, 2013, 11:28 PM
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Canada, ON, Owen Sound
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Originally Posted by jpt62 View Post
Ken, Looking rad there... Now about that white stuff outside the window....
jt
According to our weather man here, we've had 70cm (approx 28") of the "white stuff" and another storm front on its way! We could get another 30cm (12") tonite. It is also very cold here, -15F, or -25C!
I don't suppose snow is something you see in San Antonio a lot, right? Two weeks ago it was green here and rain.
It assures we have a RC building season tho!! Doug B
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Old Jan 23, 2013, 01:39 AM
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Makes our 1" of snow here sound pathetic, the amazing thing is that as a country we just dont cope, everything grinds to a halt, it is unsual for us to get snow though

I wanted to ask how you designed the movement of the gear, I just find it amazing that such a small amount of servo movement results in such an action, did you make some form of mock up? what servos are you using?

Fantastic work guys
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Old Jan 23, 2013, 08:44 AM
Dont be divided from the truth
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Canada, ON, Toronto
Joined Mar 2010
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Doug,

My mozzie is only 63" WS, but a diagram of what you did would help me figure out if I want to take on trying to build a set or forgo shedding any more blood on tricking out the model...
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Old Jan 23, 2013, 08:50 AM
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Hi Ken: We didn't get the 12" of snow as threatened, and the temp have come back up to a sunny -12C, right balmy!! hehe.
I cannot take credit for the design of the retract system. I used the same locations, rod lengths as drawn on the BT plans, but substituted oleos for the uprights. Original plans shows a single servo used back in '93, using bellcranks to pull the Lg from the same points.
I did make a common jig from heavy board, remember I had to make 6 of these LG, 3 sets! I set up and tested each unit on the jig, fine tuning each lock system. Presently we are using HDPower servos, rated for 12kg @6volts (160oz). I believe they where HD1201's, but please let me confirm that, memory is what it is!
In a perfect world, I'd use JR791 retract servos at 226ozs, and redo the the attachment arm point to allow 180 degrees. At $70 each, they are out of reach for me and my partners.
In testing, I ran the 6 sets all on the same servo, 100's of full cycles, with no failures to date. The servo is accessible, if needed, we can replace the servo with something stronger, like a HD Power 9150mg, rated at 226ozs ($35). Doug B
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Old Jan 23, 2013, 10:16 AM
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Canada, ON, Owen Sound
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Originally Posted by Dangaras View Post
Doug,

My mozzie is only 63" WS, but a diagram of what you did would help me figure out if I want to take on trying to build a set or forgo shedding any more blood on tricking out the model...
If your Mossy already has mechanical retracts, I'd suggest modifying the lower section to a more scale appearance. Without a lathe, milling machine, it would be very difficult to achieve. We had to modify the nacelles too to make this system fit. At 63", your LG would scale out at about 60% of ours. Show me some pics of what you have now, there may be a way. Doug B
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Old Jan 23, 2013, 10:33 AM
...design-build-fly-publish...
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Ware, herts. U.K.
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Originally Posted by Doug Bartley View Post
In a perfect world, I'd use JR791 retract servos at 226ozs, and redo the the attachment arm point to allow 180 degrees. At $70 each, they are out of reach for me and my partners.
Doug B
Doug, wouldn't dedicated retract servos negate the benefit of your transmitter's ability to set servo speeds?
And just delay the time they started operating by the amount of time that elapsed while the signal slope reached the point at which the servo was set to recognise that it was being asked to do something? Once woken up it would then operate at its own speed.

Seems to me you need exactly what you have - a normal operation servo that will respond to exactly what your Tx is asking. Your world just got a bit more perfect... you didn't waste $70 a throw for the wrong servo!

Robin
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Old Jan 23, 2013, 10:40 AM
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Owen Sound, ON. Canada
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Ken,

pretty nice. I never realized that small movement at the servo would translate to so much travel at the wheels.

One question for you guys, what locks the wheels down to take the stress off the servo? Is there overtravel in that pivot point on the diagonal arm?
Here are some photos showing the gear down locking system.

I have also included a snow scene for the envious ones in the crowd.
Makes for great building weather.

Ken
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Old Jan 23, 2013, 11:24 AM
Dont be divided from the truth
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Canada, ON, Toronto
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Doug, Ken,

that second picture above shows the stop....

If you take a look through this thread you can see the mozzie as I build her. The mechanical retracts failed & I replaced them with e-tracts late last year.

http://www.rccanada.ca/rccforum/show...ht=BH+mosquito

The retracts take a beating because there is no diagonal to take the landing forces and I continually have to bend the music wire strut straight (at least twice a season).
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Old Jan 23, 2013, 11:30 AM
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Its sad that as beautiful as that snow scene is I have still spent longer looking at the other pictures (I need serious help)

Doug I know I should look back through the thread but what did you use to braise/solder/weld the top frame together?

Ken
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Old Jan 23, 2013, 03:08 PM
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Canada, ON, Owen Sound
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Originally Posted by eye4wings View Post
Doug, wouldn't dedicated retract servos negate the benefit of your transmitter's ability to set servo speeds?
And just delay the time they started operating by the amount of time that elapsed while the signal slope reached the point at which the servo was set to recognise that it was being asked to do something? Once woken up it would then operate at its own speed.

Seems to me you need exactly what you have - a normal operation servo that will respond to exactly what your Tx is asking. Your world just got a bit more perfect... you didn't waste $70 a throw for the wrong servo!

Robin
Now that you have brought up the questions, I'm going to have test an actual retract sero to see if my sero speed will actually slow or speed up the retract servo. I will also check the travel adjustment to see if it can alter total throw. I have one here to test. Standby!!! Doug B
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Old Jan 23, 2013, 03:09 PM
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Canada, ON, Owen Sound
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Originally Posted by Dangaras View Post
Doug, Ken,

that second picture above shows the stop....

If you take a look through this thread you can see the mozzie as I build her. The mechanical retracts failed & I replaced them with e-tracts late last year.

http://www.rccanada.ca/rccforum/show...ht=BH+mosquito

The retracts take a beating because there is no diagonal to take the landing forces and I continually have to bend the music wire strut straight (at least twice a season).
I'll have a look asap, and get back to you. Doug B
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Old Jan 23, 2013, 03:14 PM
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Originally Posted by heli_madken View Post
Its sad that as beautiful as that snow scene is I have still spent longer looking at the other pictures (I need serious help)

Doug I know I should look back through the thread but what did you use to braise/solder/weld the top frame together?

Ken
All the welding was done with a Mig welding machine running small .030 wire. I've welded wire as small as .090without issue with the Mig.
I have tried in the past to use a Tig, but it tends to destroy the temper in the piano wire. Doug B
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Old Jan 23, 2013, 04:01 PM
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Canada, ON, Owen Sound
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Originally Posted by Dangaras View Post
Doug, Ken,

that second picture above shows the stop....

If you take a look through this thread you can see the mozzie as I build her. The mechanical retracts failed & I replaced them with e-tracts late last year.

http://www.rccanada.ca/rccforum/show...ht=BH+mosquito

The retracts take a beating because there is no diagonal to take the landing forces and I continually have to bend the music wire strut straight (at least twice a season).
The piano wire loses a considerable amount of spring and strength when they chrome plate it!! I'd use one size larger wire, drill out the retract mount, double up the setscrews.
I've looked at your build, honestly don't think you'd be happy trying to get a set like ours in there. The entire wing structure would have to be gutted to the top sheet, all cross ribs removed back to the front of flaps, then all reinforced down the sides with ply to regain its strength. Not sure even then if the nacelles are deep enough. they look shallower than true scale. fwiw Doug B
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