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New H-Quad build

#1
Hey Guys,

So Im building a new H-Quad, DT750's 30A esc's KK2.0 The standard I guess...

What is different about my quad that i have yet to see on any other quad is. Mine it totally enclosed. I have a full body hatch See some pictures below.

My 1 question is, with everything i'm right around 2KG AUW with 4900 Mah on board (Iv'e factored in wiring and motors into weight even though they are not on the quad yet.

Is that too much for the DT750's?

Quad.jpg Quad2.jpg Quad3.jpg
 

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RoyBro

Senior Member
Mentor
#2
How much is the frame alone? The Flite Test scratch build was only 227 grams and they used the DT750's. Four DT750's are about 320 grams, so I'm guessing that their setup is less than half your estimated weight.
I may be completely off base (I'm sure someone will correct me if I am), but my gut feeling is that you will need bigger motors with lower KV, for more torque and bigger props. And of course ESCs to match.

But the trend right now with quads is going with higher KV and smaller props to reduce vibration. Two kg is a lot of weight. You should see what some of the larger quads are running as a comparison.

Good luck
 
#5
Post #1 2KG or 4.4 lbs.

Thurmond
Good call.


@OP: My H.A.L. quad's AUW is ~1700 grams. I use NTM 800KV motors with 10x4.5" props with a 4000mAh 4S battery for about 180 watts per motor. You're going to want a bit more power with another 300 grams of weight, which makes me feel like the DT750's wont be up to the task.
 

xuzme720

Dedicated foam bender
Mentor
#7
This is even more than my hex weighs with the battery on board! I'm using 2836's 950Kv Turnigy's with 10x4.5's if you'd like a reference. AUW on the hex is only 1696g...
Yours might fly that heavy (even that is not for sure) but you will be very close to full throttle and have basically nothing left for maneuvering...not to mention the oscillation you'll likely have due to the struggle against gravity at that throttle setting. I think lower Kv motors with larger props are in order, or just larger motors with close to the same Kv and still use larger props, or put it on a strict diet. It looks awesome just as it is now, but looks are only half your battle. It still has to be able to get airborne...
 
#8
Hey Guys, So today i got back into the workshop.

I shaved almost 1/2 a pound with my new design, i really liked having all the gear under a clear plastic covering. so i went with that concept and came up with this new prototype

I went with 3/8's ply for the body with 2 wood spars underneath for a frame. then drilled up and mounted 2.5" number 8-32 machine screws through the body. then used nuts and rubber washers to suspend the plastic plate on top.

Now it comes in almost 300G less. so now it weighs approx (w/ motor weight calculated in)

1690g

A vast improvement over the last design. thats over 8oz of shedding!
 

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#9
Also i should mention that i will be shedding another 71g with the new go pro "frame" mount instead of the skeleton case

So brings me down to approx 1619g
 

xuzme720

Dedicated foam bender
Mentor
#10
I think 2 sheets of light ply, one as a top and one as a bottom plate would be lighter than a solid 3/8"ply and if they sandwiched the arms would give both torsional stability and a cavity for stuff you don't need constant access to, like ESC's and Rx...

I'm not sure how much weight you'd shed and it looks so good as it is. Maybe for the next build!
 
#11
Yah, i'm bound to crash this one! i ran out of light ply and its really expensive where i live. a 18x12 inch sheet is $24

So you think with my new weight i should be fine with the DT750's?
 

RoyBro

Senior Member
Mentor
#12
Even so, it's still around 4 pounds. I still think you will need more power. But there's one way to find out. Strip it to the bare minimum. No GoPro, no plexiglass cover, etc. and see how it flies. You should be able to tell right away.
 

xuzme720

Dedicated foam bender
Mentor
#13
eCalc shows that it will work with 11 x 4.7 APC props but it will be very close to the amp limit of the motor. And even with that 4900Mah you will only get about 6 minutes of flight time.

So, I guess it it will work, but just barely, IF I've got the motor settings right in eCalc, and the weight estimates are not more than final actual weight.

As far as light ply, where do you live? Here in the states, craft supply stores, like Hobby Lobby, Micheal's, etc., usually have the same light ply for much cheaper than hobby shops.
 
#14
I still think you will need more power. But there's one way to find out. Strip it to the bare minimum. No GoPro, no plexiglass cover, etc. and see how it flies. You should be able to tell right away.
Well going off of what HK says about the DT750's I have over 4000g of thrust available. so say my final weight is 1700g after everything is all said and done.

4000/1700 = 2.35
so that's still a 2.35:1 and i have heard reports of having 1100-1200g which would give me closer to a 2.5:1 thrust to weight ratio.

this is going to be an AP quad/FPV platform.

I do also have an any-copter hub I could always go to an X configuration but hoping the H-quad works...
 

Cyberdactyl

Misfit Multirotor Monkey
#15
I would agree with xuzme in that you're going to want to use 11x47 props on that baby.

My wood quad was about that weight whenever I had an 'experiment' on it and the 11x47s and DT750s gave me about 8 or 9 minutes on a 3S 2200 45c.

As to 3/16" ply, that comes in different grades at Home Depot type stores. The high-end stuff is indeed expensive, But I have bought the mid-level grade and have been fine. The problem with it is when it has a slightly "ugly" side and where I cut it might have a couple of small (~1/4") voids every six square inches or so showing at a cut edge between the outer veneers. But where I was concerned, I just filled with wood glue mixed with some saw dust. Since quad or tri plates rarely break in a crash, it's virtually always the booms, I wasn't worried.

 
#16
well i'll try it with my design. might also set up an Anycopter Quad.

As for the AnyCopter frame, whats a good boom length when using the DT750's? Im looking to get 10-12 min of flight time on 1 2200 3S battery. I was hoping to get even more with 2 2200's but sounds like its too much weight for my motors. to ever achieve 20min of flight time. OR should i go with one begger pack like a 3000 or 4000? I really dont know when it comes to matching batteries to motors for flight times
 

RoyBro

Senior Member
Mentor
#17
eCalc shows that it will work with 11 x 4.7 APC props but it will be very close to the amp limit of the motor. And even with that 4900Mah you will only get about 6 minutes of flight time.
Wow, I just got a look at the eCalc site. I'll bet that it is even more accurate than my gut feeling. :rolleyes:
I didn't see a manufacturer listing for Hextronik. What did you plug in for the DT750s?
 

xuzme720

Dedicated foam bender
Mentor
#18
I used custom with what specs HK provides for that motor and guessed on what they don't...that's why I'm not real sure how accurate it is...

I would think that with an estimated 4000g of thrust that it would have better performance numbers, but with a guess on the some of the specs, only flight testing will show for sure...

At least we can be reasonably sure that it WILL fly now!