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Telemaster Electro Build


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#1 Mr.RC-Cam

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Posted 30 March 2007 - 05:00 PM

My Magpie AP test ship was getting a bit heavy with all the onboard electronics. So I decided to move over to HobbyLobby's Telemaster Electro ARF (ETM). It is a nice looking model that reportedly can haul a lot of weight and it can be configured with flaps. The design has been around a long time in various configurations.

Here is the link to the ETM kit: http://www.hobby-lob...telemaster6.htm

I finished putting it together last weekend. I have not test flown it. If all the stars line up this weekend, I will get a chance to do that. To minimize my losses if all goes wrong, I don't have any video gear installed. Once it is trimmed out I will do that.

Below are some photos to the things that may be of interest. Not that there is anything new to tell, but I'll share the details anyway.

Attached Thumbnails

  • etm_3.jpg

- Thomas

#2 Mr.RC-Cam

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Posted 30 March 2007 - 05:03 PM

I installed a United Hobbies HXT4250 42-50 750KV brushless outrunner. It is a nice looking motor that is very low cost. With an APC 13 x 8E prop, it is pulling 36 amps at 15.5V (>500 watts), 7.5K RPM. The ESC is a Hextronik S60, also from United Hobbies. The ESC does not have a BEC in it, so I am using the popular "UBEC" switching Vreg for R/C power.

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  • pandora2.jpg

- Thomas

#3 Mr.RC-Cam

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Posted 30 March 2007 - 05:09 PM

I am using the new technology Dewalt A123 cells in the battery pack. It is a 5S1P. These came from a Dewalt DC9360 pack that I got off eBay.

Contrary to my expectations, the Dewalt prices are slowly increasing. I think it is because more modeler's are moving over to them and are using eBay to get them. Hence, more bidding competition. In a nutshell, the $85 deals seem to be gone. The DC9360 now seems to be $110 and more. Since there are 10 cells in the Dewalt pack, I was able to build two packs for the Telemaster.

I put this pack together in a hurry. I balanced the cells before I wrapped it up. But long term, I need to pull it apart and install a balancing connector. The nice thing about A123's is that they are very safe and will not burst into flames if mistreated.

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  • a123_2.jpg

- Thomas

#4 Mr.RC-Cam

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Posted 30 March 2007 - 05:19 PM

To maximize the interior cabin space (I have a lot of stuff to put in there) I moved the rudder and elevator servos to the tail. That freed up the entire cabin area. The Berg 7P R/C receiver seems lost in there!

BTW, I hacked the Berg Rx and brought out its RSSI (relative signal strength indicator) signal on a cable. It is the blue wire seen in the photo below. I took several close-up photos, but I must have accidentally erased the flash card (can't find the photos!). So, no pretty pictures to show.

It was a delicate modification. I used Gore micro coax Teflon cable. Nice stuff, but more difficult to install. The Berg has a 31136 FM Demod IC in it; RSSI is on Pin 12. Close range RF signals are about 1.55V, long range RF is about 0.75V, and missing RF is <0.35V. The RSSI voltage will vary in each installation, so YMMV. I plan to feed the signal to the Inspire telemetry board, which displays a signal strength graphic.

EDIT: I found the lost Berg RSSI Hack photos. They were safely on the hard drive after all. See Below.

Attached Thumbnails

  • cabin_area1.jpg
  • beg7p_rssi_1.jpg
  • beg7p_rssi_2.jpg

Edited by Mr.RC-Cam, 20 January 2008 - 01:28 PM.
Found Berg RSSI Photos.

- Thomas

#5 Mr.RC-Cam

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Posted 30 March 2007 - 05:24 PM

Instead of the provided plywood parts, I used carbon rods as the center wing spars. The wing is not going to fold on me, that is for sure.

I had planned to skip the rubber band mounted wing and instead, modify the wing mount for a bolt on installation. However, after cutting out some of the modification parts, I decided to go back to the rubber band method (to save build time). However, I replaced the wing mounting wood dowels with carbon rods. You can see them as black rods in the previous photo.

I was concerned with weight, so I decided to skip standard servos and go with strong mini's. There are four Hitec HS-225HB's for aileron and flaps. The mounting cutouts on the wing are too big, so I had to make little fiberglass adapters (scrap 0.047" PCB material).

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  • hs225_2.jpg

- Thomas

#6 Mr.RC-Cam

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Posted 30 March 2007 - 05:33 PM

As mentioned, I moved the rudder and elevator servos to the fuselage's tail. I used Hitec HS-81's. The model balances fine.

The rudder also operates the tail wheel; To prevent stripping gears on that servo, I added a "servo saver" to it (Kimbrough #131).

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  • hs81_1.jpg

- Thomas

#7 Mr.RC-Cam

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Posted 30 March 2007 - 05:37 PM

I installed larger wheels too. I got the idea from Divebombdave over on RC-Groups. The main wheels are now 3.5" Dubro Treaded Lite's, and the tail wheel is a Dubro 1.5" Mini Lite. These are much heavier than the stock wheels, but I need the bigger diameter for the grass field.

The Pandora camera Pan and Tilt system mounts below the model, behind the firewall. I'm using a cased KX-131 CCD video camera on it. There is an ongoing thread that discusses the Pandora: http://www.rc-cam.co...?showtopic=1562

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  • pandora1.jpg

- Thomas

#8 Mr.RC-Cam

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Posted 30 March 2007 - 05:48 PM

Despite paying attention to the calorie count, my model ended up being much heavier than I expected. The Telemaster Electro's final weight came to 99 ounces. The video gear will add about 10 ounces to that. In contrast, some ETM builders are reporting as low as 80 ounces. But, I installed flaps, bigger wheels, and have a piggish A123 pack. But I'm still surprised by the final AUW. I have been assured it won't matter.

After the test flights, I will start installing the video gear. In the end, I plan on mounting the Inspire OSD telemetry system, Garmin GPS, FMA Co-pilot, RCAP controller, and so on.

One last photo for now:

Attached Thumbnails

  • etm_2.jpg

- Thomas

#9 Terry

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Posted 31 March 2007 - 12:32 AM

It's always exciting building a new plane :)
Looks good so far !

Terry

#10 Wavess

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Posted 31 March 2007 - 12:48 AM

Great work, seems a very capable plane for adding extra weight, does it have 0ļ diedral?
Iīve also been looking at those hextronic cheap brushless for my next electric, they are like 3 times cheaper than an axi, have you tried those before?
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#11 cfe7

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Posted 31 March 2007 - 06:25 AM

I also built a Telemaster for FPV. This is the Jamara Telemaster 60 converted to electric power (AXI 2826/12). Wingspan is 180 cm and weight is 4 kg. The maiden flight was one week ago.
There was ice on a nearby lake and nice weather, so I gave it a try. I never thought the electric motor should be powerful enough to pull the plane with camera gear and everything, but I was able to climb at ca 40ļ angle (vow was I surprised). The plane has 2.5ļ dihedral. I havenít flown with dihedral for 20 years, so I had to ďlearn to fly againĒ. Itís almost scaring when the plane doesnít behave as a neutral pattern plane.
As you might notice the camera gear is quite big (and powerful), but picture quality is outstanding.
The plane is only a test rig for my first FPV trials with goggles. In June I plan to use it for a video project from my birthplace in Lofoten, Northern Norway (http://www.lofoten-s...ngelskindex.htm).
I guess youíll be hearing more about this later :blink:

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  • Picture1.jpg

Edited by cfe7, 31 March 2007 - 06:28 AM.

Cfe7
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#12 cfe7

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Posted 31 March 2007 - 06:31 AM

This is just to post one more picture of the plane.

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  • Picture12.jpg

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#13 Mr.RC-Cam

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Posted 31 March 2007 - 09:14 PM

It's always exciting building a new plane

I used to say I would never build a balsa ARF. But thank goodness for those far east sweat shops, since I can't imagine ever getting enough free time to build the kit version. BTW, the ETM's build quality is very high (better than I could have done).

... does it have 0ļ diedral?

I would guess it is about 4ļ or so.

This is the Jamara Telemaster 60 converted to electric power (AXI 2826/12). Wingspan is 180 cm and weight is 4 kg.

Your model seems to be similar in size to my ETM, but is a bit heavier. Are the landings a bit "hot?" Did you install flaps?
- Thomas

#14 cfe7

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Posted 31 March 2007 - 11:36 PM

Your model seems to be similar in size to my ETM, but is a bit heavier. Are the landings a bit "hot?" Did you install flaps?

The model has flaperons, but I haven't used them so far. The ice I landed on was more than 2 square kilometres, so I had a lot of space to bring the plane down at high speed.
My model was originally intended for a 60 2-stroke. I guess itís much heavier than your version.
At 4 kg landings are faster than many trainers, but Iím used to fly 90-120 size pattern planes so I find comfort in the little extra speed. It prevents stall problems on final and gives a positive rudder response with engine at low rpm.
Iím going to fly this model a lot this spring to really get to know its behaviour in the air.
Cfe7
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#15 Mr.RC-Cam

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Posted 01 April 2007 - 03:42 PM

Iím going to fly this model a lot this spring to really get to know its behaviour in the air.

I just maidened my Telemaster. I'm VERY happy with it. Like you, I intend to get to know it well. :)
- Thomas

#16 cfe7

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Posted 04 April 2007 - 06:47 AM

I got a very precise scale today. My Telemaster was of course the first plane to go on it.
4046 grams. My initial guess was 4000 grams. Not bad to miss by only 46 grams :D

My PT 60 with an OS 91 Surpass weights 4017 grams, so I think the Telemaster is in the area itís supposed to be. It flies well with takeoffs less than 15 metres (with skis). Takeoffs with wheels from grass should not be more than 20-25 metres. Iíll know more when spring comes to my hometown here in the arctic.

:blink:
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#17 Mark Harris

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Posted 04 April 2007 - 04:31 PM

Spring makes it to norway? haha.. nice try!

#18 FlyingHigh

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Posted 08 April 2007 - 08:22 AM

-AT-cfe7
Do you have some video from that maiden flight ?

#19 cfe7

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Posted 08 April 2007 - 09:51 AM

Hi FlyingHigh!
Sorry I didnít record while flying that day. I was to busy learning how to fly a trainer with a lot of dihedral. I hate it when planes are not neutral in all axes ;)
If you like to see other videos I made you can look here:

http://www.megaupload.com/?d=YX06A7KH

http://www.bodomfk.n...124&module=news

By the way where are you located?
Cfe7
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#20 FlyingHigh

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Posted 08 April 2007 - 11:33 AM

Nice videos cfe7, I'm living a bit south of you.
I'm looking forward to do some fpv flying myself this spring,
hopefully in a month or so. Just waiting for the last bits and
pisces to arrive in the mail :)

Edited by FlyingHigh, 21 June 2008 - 07:45 AM.