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Mar 19, 2012, 08:54 AM
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Discussion

8.5 motors DD


Has anyone run any of the brushed 8.5mm PZ and HK motors direct drive? If so what props would be appropriate?

scrubs
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Mar 19, 2012, 10:24 AM
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Done several with CommensenceRC Turboprop is very good but DD typically not for slow models and DD8.5 sucks lots of juice - 1S180 must be good lipo - smaller lipo would be too little runtimes, bigger lipo would gets heavy and not enough thrust anyway

see this DD setup in only the smallest litest (simplest=proflile) scratch

old air hogs/ITC props work too but same problem magnified...
Mar 19, 2012, 10:27 AM
Way to many airplanes!
Was interested as well, but commonsenseRC seem to have only APC propellers?? Do you have a link?
Mar 19, 2012, 10:39 AM
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here you go
http://www.commonsenserc.com/product...oducts_id=1575

sure plantraco sells em too - nope out of stock - others here might work
http://www.microflight.com/Online-Catalog/Propellers
Mar 19, 2012, 10:43 AM
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I expected they'd be juice hogs but it's not really a factor since I'm thinking of freeflight where a motor run might only be 30 sec WOT and the batteries would only see a couple of flights.

Even tho Gordie J's tables don't list it I know one guy who was running the SS blue with a U-80 prop.

Awhile back I built a couple of freeflight mini Stardusters ( nos pylon model ) but with the typical N20, 7mm DD or GWJ gearbox they were leasurely climbers at best. Did try a P51 motor and GWS 3050 but the battery wouldn't handle it.

I know the answer is brushless but don't want to go that route.

scrubs
Mar 19, 2012, 10:45 AM
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IMO - this is the best brushed DD prop for 7mm and 8.5!!!!!!! make sure you got good lipo otherwise your runtimes will be short!

seriously for the weight (5ish grams) motor+prop pushes +20grams - better with 7mm than 8.5 due motor draw
Mar 19, 2012, 10:52 AM
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Quote:
Originally Posted by scrubs
I expected they'd be juice hogs but it's not really a factor since I'm thinking of freeflight where a motor run might only be 30 sec WOT and the batteries would only see a couple of flights.

Even tho Gordie J's tables don't list it I know one guy who was running the SS blue with a U-80 prop.

Awhile back I built a couple of freeflight mini Stardusters ( nos pylon model ) but with the typical N20, 7mm DD or GWJ gearbox they were leasurely climbers at best. Did try a P51 motor and GWS 3050 but the battery wouldn't handle it.

I know the answer is brushless but don't want to go that route.

scrubs
Nice scrubs - been thinking of doing the same kinda thing - very small DD motor on Micro DLG

In this case I think I'll be going very lite weight 6mm with DD ITC puller - glider needs only the smallest amount of thrust climb... see if I can somehow make a small folding prop. should be fun
Mar 19, 2012, 12:01 PM
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A while back I used 2 PZ P-51 motors on a Micro MiG 21 (posted the build over in the Micro EDF Jets & Power Systems Forum under Start of Micro MiG-21) it was going to have a 30mm EDF but I went with the two DD motors in the wings flys great with the AirHogs Props and the BSD Yellow props cut down.

Pete
Mar 19, 2012, 12:29 PM
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heres a No Verts Wing did a while back - 7mm TT
9" Flying Wing - No Verts! (1 min 38 sec)


here is a Firefly too - 7mm TT
SF KF-Firefly (2 min 0 sec)
Mar 19, 2012, 12:56 PM
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I have used the 8.5 DD with a Plantraco tri-turbo fan prop. It gets approx 28gms thrust, but is a serious amp hog. I think that the reason most owners of PZ/Eflite Umx planes get the pulsing they do is because of this. The motors seem to max out the esc's on the bricks. Modfly did a thread on adding an external esc a few years ago to cure the pulsing problem. With that said these are still good motors they just are hogs, and it's hard to find a decent prop for them.
Mar 19, 2012, 04:16 PM
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Quote:
Originally Posted by MUTCAKE
I have used the 8.5 DD with a Plantraco tri-turbo fan prop. It gets approx 28gms thrust, but is a serious amp hog. I think that the reason most owners of PZ/Eflite Umx planes get the pulsing they do is because of this. The motors seem to max out the esc's on the bricks. Modfly did a thread on adding an external esc a few years ago to cure the pulsing problem. With that said these are still good motors they just are hogs, and it's hard to find a decent prop for them.
Is that on a milder PZ Champ motor or a hotter P51 motor?

scrubs
Mar 20, 2012, 01:08 AM
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mutcake: how much amp draw?
Mar 20, 2012, 07:02 AM
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Ok I stand corrected. Amp draw is about 1.62 amps on the 8.5 4site motor in gearbox with 5030 prop and just a bit more for dd Tri-turbofan prop. It did not go over the 2amp rating of the esc. I just have crappy old batteries.
Mar 21, 2012, 01:20 PM
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that is not that bad.....figure 1.8A or so. on an AR6400T about right.
Mar 21, 2012, 01:45 PM
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I've been running a PZ 8.5mm direct drive with a Tri-Turbo for almost a year and a half on one of my Viperwings. As long as you have a big battery in good condition, it will do just fine. Makes gobs of thrust for the weight. When you think about how much power these motors have, it actually makes the amp draw seem quite low. After all, they will produce almost twice the thrust of a blue SS 7mm motor with a Tri-Turbo prop, while drawing roughly the same current!


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