Author Topic: Airco DH2  (Read 37930 times)

johnfireball

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Airco DH2
« on: January 04, 2012, 00:03:57 AM »
Hi all,
      I have began my next project, it's a first world war DH2 of the type my grandfather flew, bought in kit form (aerographics), 28" span and my plan is to convert it to 3 channel rc with electric power.
Some work done on dummy engine
 
And the lewis gun,  wicker seat and inst panel


More to follow,
John.
I have the body of an 18 year old.........I keep it in the freezer

Happy Days

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« Reply #1 on: January 04, 2012, 07:11:36 AM »
Hey John,
That’s a very intricate looking little model. Keep up the good work.

It might be that you already know the following, in which case ignore it, but just incase you don't :wink: ...............

Regarding powering the model………There are probably many web sites that’ll tell you how to work out the right type of motor, esc, prop & battery but for your info this is the one I use http://www.modelmotors.cz/index.php?page=1
Personally I’ve found AXI motors to be one of the best  motor manufacturers, but that’s only my opinion.

If you look at the right hand side of this page you’ll see the heading  “Fast Axi Set Up”
Use the drop bars to tell AXI what style of model you’re building and it’s weight and it’ll give you some suggestions of appropriate motors from it’s range.

If you then click on any of the motors that the selection has offered you, and scroll through their details, you’ll see what type of esc , battery & prop is recommended for that motor depending on what style of flying you intend to do.

Just going on from there; If you don’t want to buy an AXI motor (incidentally, most of the big European retailers sell them) then make a note of the recommended motors’ RPM/v
This is the  number of rpm the motor produces per volt applied to it.
If you then want to check for a similar motor from another manufacturer then use that RPM/v figure to see what a comparable motor from, say,…Hacker, or E-flight or any other manufacturer would be. (The number of rpm per volt is a good indication of the power of the motor.)

Just before to whiz off the the AXI site,………..little more info for you. Some brushless motor manufacturers show the spec of their motors’ rpm/v as “ Kv “ (1000rpm per volt)

Good Luck

Keith
Try not to run out of airspeed, altitude and ideas....... all at the same time.

johnfireball

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« Reply #2 on: January 04, 2012, 16:35:53 PM »
Hi Keith,
          Thanks for help. Here's the setup I ordered, hopefully it'll work out. What do you think? It will be my first foray into electric. My guess is that the final weight of the model with gear will be around 150grms  I would like the model to fly quite slowly to look more scale.I have also ordered a voltage regulator to power reciever and servos from one lipo.

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9386

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6455

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9028

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9670

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8044
This kit is actually quite simple but I seem to always have to complicate things. I think I'll get to fly my quark this weekend.
John.
I have the body of an 18 year old.........I keep it in the freezer

Happy Days

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« Reply #3 on: January 04, 2012, 17:52:30 PM »
From what I can see you’ve ordered an in-runner motor with a reduction gear. In-runner motors tend to have high rpm and low torque.
(Personally I’ve always preferred out runner motors which have more torque and lower rpm,…..It saves the weight of the reduction gears.)

I have no experience of using in-runners and from what I read on the website there is little detailed info about the motor/reduction gear.

The esc you’ve ordered should be okay, and I notice that it has a Battery Elimination Circuit (B.E.C.) which means that the esc will power your rx and servos from the Li-Po battery.

I don’t know which of the two props you intend to use. Although three /four bladed props look good on scale models when the model is static, I understand the don’t work very well in actual flight. Two bladed props work better, aerodynamically speaking. I know some scale flyers use two bladed props when flying and then change the prop for multi bladed ones to show the model when stationary, for a better scale appearance.

Because of the lack of detailed info on the motor/reduction gear I have no idea if you have a the right size prop or not. The esc and motor are matched, and the battery is probably an okay size as well. I have no idea how long a flight time the battery will give you because I can’t equate how much current that prop will draw through the motor. (Due to lack of details about the motor)
Certainly you should get  a few minutes of flight at least.
Best thing is to try the set up you’ve got and if the flight time is too short, try a bigger battery.
Keep an eye on the temperature of the motor and esc. If the prop is too big for the motor it will start getting hot. (The motor that is, not the prop! :lol: )
If the motor or the esc gets hot to the touch I’d get a reduced pitch or dia. prop. (If I were you I’d run a timed static test first before trying to actually fly it.)

If you’ve already ordered these parts then really it’s a suck-it-and-see situation. It’s all part of a learning curve John.
Good, ain’t it!

K.
Try not to run out of airspeed, altitude and ideas....... all at the same time.

johnfireball

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« Reply #4 on: January 04, 2012, 23:36:19 PM »
Hi Keith,
          Thanks for assistance, as you say I'll have to suck and see. So I don'tneed a voltage regulator as the esc does the job (more weight saved). The gearing on the motor is 7:1 and the long output shaft appealed as it has to go through the dummy engine. I just hope it has enough oomph to drag this fully rigged biplane through the air.
        Some more done on the cockpit

Inner side panels added ( showing rigging wires) cockpit surround added. I'm very attatched to my home built wicker seat just need to add seatbelts and a pilot.

       

These are the outer side panels originally fabric stitched around the airframe. I have used brown leatherlook embossed paper used for fancy box manufacture, will add stitching and attatch after painting.



John.
I have the body of an 18 year old.........I keep it in the freezer

Happy Days

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« Reply #5 on: January 05, 2012, 01:30:59 AM »
Very intricate work you’ve done there John. :clap:  You certainly have more patience than me!

Ah!. So the gearing is 7:1.…..Let’s see what that means:

Voltage 7.4 x 4500Kv = 33300rpm :- 7 = 4757 prop. rpm. I would have thought that was a wee bit slow for a 4inch pitch prop, but as you’ve already ordered the parts see how you go. My guess would be that you’ll need a slightly greater pitch prop. If it does fly with a 7x4 prop you should get a good flight time. (Probably a good 6 minutes)

Just another thought that’s come into my head John, relating to mounting the motor/reduction gear. Maybe you’ve already seen this coming but when you mount the motor I’m thinking that, obviously the output shaft of the reduction gear will have to be in the centre of the fuse, which means the in-runner motor (the heaviest part) will be off centre.
I remember when I had a spell of flying little indoor planes (180grm biplane) I found it most important to have the model laterally balanced. (As with all planes of course but I found it more so with the smaller models.)
Maybe other more experienced flyers of these type of models will know a trick or two but I’d have thought you’ll have to mount the unit so the motor is above or below the output shaft. If the motor is to one side then I’d imagine you’ll have to add weight to counter that of the motor.

As for the voltage regulator, no you wont need it for this model. You’ll find the esc has a plug on it that fits into your rx. (Throttle position.) As soon as you connect the battery to the esc the rx will power up. :D
The voltage regulator could come in handy though, in your gliders! :shock:  If you wanted to use a 2 cell Li-Po instead of a metal Hydride battery because Li-po’s are lighter and hold more current 8) )

Keep up the good work John, & good luck.

Good heavens, look at the time. I’m off to bed to cuddle my teddy. :oops:

Keith
Try not to run out of airspeed, altitude and ideas....... all at the same time.

johnfireball

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« Reply #6 on: January 06, 2012, 00:46:37 AM »
Hi all,
       I'm back to bore you all again. Thanks again to keith for electric advice, I believe the motor will fit in symetrically so hopefully no problem there. You could well be right about prop pitch. This is a beautiful little kit, it's my first laser cut build all others I have done were from paper plan only (what a difference in accuracy), however it's not for the novice the instructions are nonexistant and a good knowledge of build techniques and plan + parts studying is required or you will end up making a major cock up. The wood used is strong but heavy  and I fear the final weight may be more than I anticipated.
             Anyway some photos of wing build showing modification for ailerons and dihedral setting. I plan on covering the wings in one go using the covering material as a hinge so note the angle of the aileron leading edge to allow down throw.
As an aside John from up north I notice from a photo in your workshop a tigermoth GAYIT, I flew in this plane in the seventies, loops, spins, etc at a gliding event in Kilkenny. It was a friend of the Dads Jeremy Bryson who piloted. We wore leather caps and all the gear, a memory I will cherish.
John.            
I have the body of an 18 year old.........I keep it in the freezer

JohnPearson

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« Reply #7 on: January 06, 2012, 16:23:11 PM »
Hi John

Well impressed, looks great!

johnfireball

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« Reply #8 on: January 12, 2012, 21:50:03 PM »
Hi all,
      A little more progress made and experimented with a different covering film. I found a discussion group on the net and the idea looked good.

http://www.rcgroups.com/forums/showthread.php?t=274520

 So I got hold of a roll of this stuff and I can honestly say I am a convert. It's very light preglued and quite easy to use,I covered this wing in one piece for top and one for the bottom.  Available in 3 thicknesses (30 micron, 42 micron and 70 micron) and either matt or gloss finish only disadvantage is transparent only so needs to be painted. I opted for matt finish as I think it takes paint better. The water based paints that the warhammer shop sells take very well and can be airbrushed.
                 A few pics of covering procedure

Lay covering over frame on flat surface
   

Tack the edges down with the iron set on silk, Dont need to be too fussy.



Retack all edges with iron set to wool and be sure they are well stuckand then shrink all over on wool setting .

 

Finished wing (not one wrinkle)  with 200 meter roll of covering film, a lifetimes supply. The roll  cost approx €50.00
If anyone wants to try some let me know, you wont be disappointed.
John.

I have the body of an 18 year old.........I keep it in the freezer

JohnPearson

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« Reply #9 on: January 13, 2012, 16:30:17 PM »
Hi john, great idea and cheap too! would it work on foam I wonder. John I would like to give it a try. I found a place in England that supplys the film, however if there is a company local, I would try them.

johnfireball

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« Reply #10 on: January 13, 2012, 17:13:58 PM »
Hi John,
          This film is available at any graphic art printing consumables supplier it is called laminating film not to be confused with encapsulating film. The gloss finish type is cheaper but not sure about paint adhesion. If you wish I could send you some of the 30 micron in the post. This stuff is a pleasure to work with.
John.
I have the body of an 18 year old.........I keep it in the freezer

johnfireball

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« Reply #11 on: January 13, 2012, 18:04:51 PM »
Hi John,
        I tested my roll on pink foam and it takes no problem. I'm not sure if all roles of film will behave the same as on the forum link it is suggested that high iron temperatures are needed where mine will melt if iron is too hot.
http://www.presco.eu/sub-category.php?ID=4&parentCatID=1

Link to where I got mine it's the 30micron roll on the top right.
John.
I have the body of an 18 year old.........I keep it in the freezer

johnfireball

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« Reply #12 on: January 19, 2012, 00:16:22 AM »
Hi All,
       A little more done and testing of all the gear in progress.

Tailplane construction

 

Laminating fin outline



Gear installation



Overall view with base colour applied to flying surfaces



Hi Keith,
           I think you may be correct about prop pitch. With testing I can run at full power for 18+ mins per charge but feel I'm lacking thrust. No signs of overheating. Amazing power for such a small motor. Do the gears need lubrication? The motor is also turning the dummy engine and doesn't seem to be a problem. This motor could not be a better fit in this model. I could fit an 8" prop with more pitch to try gain some more push as I feel the rpm of the prop is quite low. Any suggestions welcome.
John.
I have the body of an 18 year old.........I keep it in the freezer

Happy Days

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« Reply #13 on: January 20, 2012, 07:12:16 AM »
Hey John,

As I think I mentioned before, I’m sure someone experienced with these types of models has told me that three (or more) bladed props don’t work very well at these very small diameter sizes. :!:  (Some of the racing model lads use single bladed props. Yes you read that correctly! i.e. “half” a propeller)

If I were you I’d remove that three bladed prop and fit the two bladed one. Then run it up and see if it produces any more thrust. I would imagine it would, and that the run time per charge would be reduced, showing that the motor is doing more work.


As for the gears: yes they will need lubrication, but I have no idea what would be the correct lubricant to use on them I’m afraid.

You said that the dummy engine is turning with the prop. So presumably the full size plane used a rotary engine rather than a radial one, yes?

Where are you intending to fly this home made marvel?

K.
Try not to run out of airspeed, altitude and ideas....... all at the same time.

johnfireball

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« Reply #14 on: January 20, 2012, 16:50:03 PM »
Hi all,
      Thrust problem solved with use of an 8" slow fly prop which suits my low rpm geared motor. Yes Keith dh2 was powered by a 100hp gnome rotary engine
   http://www.youtube.com/watch?v=CYc-H8Wg-MQ
 Apparently this engine was a barn find

Undercarriage and new prop



John.
I have the body of an 18 year old.........I keep it in the freezer