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Old Mar 14, 2008, 05:21 PM
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manuel v's Avatar
Mexico, BC, Mexicali
Joined Aug 2004
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Bob.

I have no experience with bimotor.
What do you care so much small differences in the two RPM motors?
Are you going to use against contra props?
How much help you mix the rudder to the motors?

Manuel V
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Old Mar 14, 2008, 05:36 PM
5,200 Led Lighted Bike-Bob P.
**neons**'s Avatar
USA, MA, Swansea
Joined Mar 2003
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Nanuel,
I am using 2 motors, or as you say bimotor.I do not care to much about the RPM it turns as long as the amps are not to high and they have plenty of thrust to move the heavy twin motor plane. If i can g 30oz thrust out of the Hextronic DT759 with 9X5 or 9X7 3 blade it will be excellent. I am not using mix throttle or contra rotation motors. I think 14 turn of 21 or 22AWG wire may be close to what I need. I will use 11.1v 3s lipoos ????ma
**Neons**Bob
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Old Mar 19, 2008, 12:40 AM
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Joined Dec 2006
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Just got my DT750 today... doesn't come with any prop nuts?
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Old Mar 25, 2008, 05:36 PM
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United States, VA, Bedford
Joined Sep 2006
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Quote:
Originally Posted by warhead_71
Just got my DT750 today... doesn't come with any prop nuts?
Nope, mine didn't. I used the nuts and washers off of a GWS 400 gearbox and they worked fine. Speaking of a GWS, their safety spinner fits on the shaft of the DT7*0 too. Unfortunately, I cut the shaft of my motor shorter before I realized that fact..

-Shawn
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Old Apr 02, 2008, 12:58 PM
5,200 Led Lighted Bike-Bob P.
**neons**'s Avatar
USA, MA, Swansea
Joined Mar 2003
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Here is a link to a plane I built scratch.
http://www.rcgroups.com/forums/showp...&postcount=217

It uses the new Hextronik DT750kv motor. The videos link has 3 movies with this motor lugging around my new plane. More specs on the build will give you an idea of the flight weight and electonics also. Very nice motor. Surprising results stock.
**Neons** Bob
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Old Apr 05, 2008, 11:00 PM
willfly4$
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United States, MS, Bay St Louis
Joined Apr 2005
250 Posts
dt750

got this motor in a CM 3D-36 http://www.bphobbies.com/view.asp?id...25&pid=V189068
first ground run ripped the mount out, wayyy overkill 11x4.7sf, turnigy 25amp sc, zippy 1500 3s 20c.
turned throttle atv down to 75% and it hovers at a little over half throttle, dont know the weight of the plane but its somewhere around 25oz the specs are on the website above. im going to put this motor on a brio 10 next as it seems to be comparable with a park 480
pretty cool motor for 10 bucks, anybody notice that united is really lacking stock for the last month?
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Old Apr 05, 2008, 11:35 PM
5,200 Led Lighted Bike-Bob P.
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USA, MA, Swansea
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My motor was bench tested with a 12x6 APC thin blade from Hobby City. I have it adapted to a GWS stick mount. When I ran it the vibration was at a very bad alarming level. I spent some time with it and got it balanced the best I could. It smoothed right out like a snoozing baby. I recommend balancing props on this motor with all it's torque.
I ran an 11x7 SF APC prop (33oz Thrust 18amps)and got good power at a lesser amp draw than the 12x6 prop. The bigger prop performed better though at 22amps. The 11x4.7 did not place anywhere near that props 33 oz thrust. The 12 inch got 44oz thrust. This motor is way overkill for a CM 3d-36.
I have not checked HC stock on the motors lately. I wonder how the Hex DT700 performs. It should be better with the large props.
**Neons** Bob
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Old Apr 06, 2008, 01:47 PM
Dave North
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USA, CA, San Jose
Joined Apr 2004
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Quote:
Originally Posted by **neons**
I ran an 11x7 SF APC prop (33oz Thrust 18amps)and got good power at a lesser amp draw than the 12x6 prop.
Bob, maybe there is a good reason for rewinding. My 18T 22awg just tested about 35 ounces with roughly 15 amps (that's averaging two batteries etc) using the 1170 HD. That was just a preliminary sounding though, since I wanted to test a new toy:

I think the killer prop for this motor may be the GWS HD <- note: HD not RS) 12x6. This delivered 40+ ounces at about 16 amps. I'll trade an amp for five ounces any day!

I managed to get hold of one of these from United Hobbies. It's unlike any other GWS HD -- comes with adaptor rings for just about any mounting system and was balanced "out of the box." Ran very well!


Dave
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Old Apr 06, 2008, 07:58 PM
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Dave,
I was using the APC SF 11X7 earlier and got 33 oz thrust with a Zippy 11.1v 1600 20c battery. The best I got so far is with the Hobby City 12x6 APC thin look alike copy prop. Over 20 amps and around 40 oz thrust with a new Zippy 1800 11.1v 20c battery. I tried a 12x6 GWS DD prop and I found in the 15-20 mph wind it did not bight as good as the APC thin prop.
The 11X7 APS SF bit good with the blade area in the wind also at mid rpms. I compared the flights with 4 different props and the 12X6 performed the best after balancing. It gave me good power range in my flights for my new plane. The plane flew with landing gear at 32 oz flight weight. It did well with the 11x7.
I then added the pontoons and it still flew ok at 44oz flight weight. It was suffering in the turns with the wind. I then tried the 12X6 GWS DD and at wide open throttle the power was good. It did not do to good in the turns again. The low rpm blade area just was not there. That is when I went to the 12x6 APC thin blade copy from HC. I got good all around performance. It had nice power at the turns. Today I changed the floats for my own scratch foam floats. I saved almost 4.5oz lighter in weight. That should translate similar to horsepower. It puts me on a 1 in 1 thrust power to the flight weight ratio of this motor. I am waiting for some better weather to try it ROW. I just ordered another motor.
**Neons** Bob
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Old Apr 06, 2008, 08:45 PM
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United States, VA, Bedford
Joined Sep 2006
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Quote:
Originally Posted by **neons**
Dave,
I was using the APC SF 11X7 earlier and got 33 oz thrust with a Zippy 11.1v 1600 20c battery. The best I got so far is with the Hobby City 12x6 APC thin look alike copy prop. Over 20 amps and around 40 oz thrust with a new Zippy 1800 11.1v 20c battery. I tried a 12x6 GWS DD prop and I found in the 15-20 mph wind it did not bight as good as the APC thin prop.
The 11X7 APS SF bit good with the blade area in the wind also at mid rpms. I compared the flights with 4 different props and the 12X6 performed the best after balancing. It gave me good power range in my flights for my new plane. The plane flew with landing gear at 32 oz flight weight. It did well with the 11x7.
I then added the pontoons and it still flew ok at 44oz flight weight. It was suffering in the turns with the wind. I then tried the 12X6 GWS DD and at wide open throttle the power was good. It did not do to good in the turns again. The low rpm blade area just was not there. That is when I went to the 12x6 APC thin blade copy from HC. I got good all around performance. It had nice power at the turns. Today I changed the floats for my own scratch foam floats. I saved almost 4.5oz lighter in weight. That should translate similar to horsepower. It puts me on a 1 in 1 thrust power to the flight weight ratio of this motor. I am waiting for some better weather to try it ROW. I just ordered another motor.
**Neons** Bob
Sounds like you need a 17T Delta. Or at least that what I plan to do with the DT750 I ordered a couple weeks ago. Looks like vacation season will be over before it gets here though.
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Old Apr 06, 2008, 09:00 PM
willfly4$
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United States, MS, Bay St Louis
Joined Apr 2005
250 Posts
dt-750 overkill

took the plane to the field today and rung her out, im now using an 11x7e APC and collet adapter (prop saver is a joke) the motor will hover at a little over half throttle (throttle ATV is turned down to 75%) i got over ten minutes in the air doing fairly hard flying and put 1250ma back in the battery, the guys at the field really liked it

this is just a stock motor, im scared to try winding but tomochris has got some good numbers with his rewind
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Old Apr 06, 2008, 11:47 PM
Dave North
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USA, CA, San Jose
Joined Apr 2004
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Bob, I'm not terribly surprised. I have had good luck with the APC Thin Electrics on bigger motors -- just haven't tried it yet. I suspect the HC knockoff isn't quite as good (the few I've seen haven't been) so it might be worthwhile to grab "the real thing" and see if there's any difference. If I understood what you said correctly...

Weird thing is I'm having trouble getting my 1170 HD to balance on the threaded shaft. Everything seems fine, but it wobbles. The 1260 with its weird adapters is smooth as silk.

clea, if you got a good one (properly wound) I really don't think it makes that much difference to rewind. At least mine didn't improve all that much -- a little.


Dave
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Old Apr 07, 2008, 09:38 AM
5,200 Led Lighted Bike-Bob P.
**neons**'s Avatar
USA, MA, Swansea
Joined Mar 2003
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Dave, I have had 1 or 2 props that wobbled. My finding was the hole was off. As long as the back plate and washer compressed it flat it was ok. I found the hole was drilled crooked and I reamed it out some and it straightened out. The HC knock offs may be drilling the holes untrue. Out of 5 different size HC props wer tried I found one well off. I decided to balance a large hand full of props including GWS to correct them all. Another finding was the edges on the HC APC knockoffs were extremely sharp like a razor. I had to sand these edges down some. I had visions of getting hit with one of these. Bad.
At this time I am not going to wind a Hextronic DT 750. I have to go through my prop collection to see if I can find a 9x8x3blade prop from my old gas motors. I want to test it on the stand. I have 9x7x3 blades on hand now and the test gave me about 26 to 28 oz thrust. I think an 8 pitch will give me the thrust I need. A ten inch prop would require me to alter the twin motor plans more. I had to do that already fo the 9 inch props. Then I may have to do a hotter wind around 15 turns to handle the 9x7inch pitch props. I know the amps will go up some also.
**Neons** Bob
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Old Apr 07, 2008, 11:12 AM
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Chicago, IL
Joined Dec 2006
5,159 Posts
So I have this motor and I want to build an inter-war biplane or Golden Era racer... maybe a Travel-Air "Mystery" or a Curtiss Goshawk (or Sparrowhawk) or a P-26 or a Laird Super-Solution... something along those lines.

I'm building with FFF and want to go as big as I can and still get scale-ish flights (with a little extra power to spare for emergencies). Any recommendations for scale/weight/wing-loading? I don't need to be able to hover the plane, but I'd like to be able to do mild aerobatics -- loops and rolls and such, and I prefer speed management versus raw thrust... so what's a good prop for a balance of speed and thrust?

Suggestions?
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Old Apr 07, 2008, 12:35 PM
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My $.02. I am not an expert on selection of motors and props. The Hextronic DT750 is a good place to start if you want bang for buck. My Ugl-E Stick is 44oz with floats and a decent size plane 44" wing.. It flew, not excellent, but good with that weight. It was windy puffs of 15mph in the video link and it handled it. I could not do any verticals as I could with the wheel landing gear flights with 33oz flight weight. But for my purpose the project was a success.
See it here with the other test flight movies of the plane (14vids total all types):
http://good-times.webshots.com/video...29027590tiAHhY
I would suggest building the plane of your choice and to keep it within reasonable size and weight to fall within the Hextronic DT750 specifications. I think inthe 28 to 35oz range and you will have plenty of flight thrust with that little reserve to help you out of those bad flight situtaions. That should keep it flying with a large blade area within your needs. I think a plane in the 40 to 44inch wingspan would do well. Less wingspan with a biplane. As you can see I work more with feel than figures. With my selected 12x6 APC thin blade I use a 1600 or 1800 Mah 11.1v 20C battery. I have kept the flights around 6 minutes. I am sure it would go longer.
$.02
**Neons** Bob
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