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Old Jun 14, 2012, 01:31 PM
ICrashRCs
United States, TN, Memphis
Joined Jun 2011
1,196 Posts
Very Nice! I really like that a lot.
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Old Jun 14, 2012, 02:08 PM
just Some Useless Geek
Chicagoland
Joined Oct 2008
2,543 Posts
Quote:
Originally Posted by solentlife View Post
Note the DIY motor mount that...can be 'bent' to angle needed or twisted...
Does that include getting bent by the torque, power, or vibration of the motor? What about the fact that the motor mass is hanging off of an essentially unsupported plate (only one side supported)? I've always wondered how well those kinds of mounts hold up.
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Old Jun 14, 2012, 03:13 PM
ICrashRCs
United States, TN, Memphis
Joined Jun 2011
1,196 Posts
Pj 2

Building ParkJet #2 now.
It will be a everyday park flyer. I just want this one to remain flyable for a while.
Planning to run an Emax 2812 on 3s w. a 6 x 4. Maybe even 7 x 6.
Moved the servos on top and added a carbon strip under the elevon te's.

After seeing where the weak spots were in PJ 1, I added a few strategic carbon strips on this new one.
Thought it may give others an idea to use.
In the well of the fuse I added 2 strips to hopefully help keep the nose from folding upward in a crash. You can break through to the bottom if not careful.
And in the canopy I added 2 strips to help keep the sides from busting out.
Just cut slits, slid in the strips and CA'd them shut.
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Old Jun 14, 2012, 11:34 PM
Registered User
tobydogs's Avatar
Joined Mar 2012
78 Posts
very nice nigel and ifly,keep the photos coming.

i think the motor mount will work for nigel very well and using 2 scews won't matter as the motor has plenty of surface to stay flat on the mount. the only bending that mount will get will be by hand to adjust angles....of coarse a hard nose into terra firma will disloge any good mount[don't ask how i know]
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Old Jun 14, 2012, 11:48 PM
BLANIK213
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United States, NY, Phoenicia
Joined Feb 2008
665 Posts
nice work Nigel I like the paint job ,excellent for visibility and the motor mount will do just fine and act like a heat sink for the motor. Only a hard landing or other unmentionable event will bend it .As far as torque rolls are concerned a twin doesn't suffer from them as a single does the fact that it;s a twin reduces the affect to almost nothing.
Good luck with the maiden.
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Old Jun 15, 2012, 10:10 AM
Registered User
Vienna, Austria
Joined Apr 2007
2,134 Posts
Quote:
Originally Posted by IFlyRCs View Post
Building ParkJet #2 now.
It will be a everyday park flyer. I just want this one to remain flyable for a while.
Planning to run an Emax 2812 on 3s w. a 6 x 4. Maybe even 7 x 6....
You might want to try 6x5,5, I find that prop fits the EMAX 2812 nicely, good speed and efficiency, and enough thrust for vertical on a Parkjet.
My (light) Funjet scoots along nicely w/ this combo (3s 800mA lipo, 12A ESC does get warm but not hot, it's only round 12 amps static)

Funjet elegant vs Microjet hooligan (2 min 56 sec)


in the second half of the video you see my Microjet on the EMAX 2805 2850kV, turning a 4,5x4,5 TGS. That thing is fast, and this combo would work very well on the small. sleek Parkjet...

cheers
Clemens
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Old Jun 15, 2012, 10:54 AM
ICrashRCs
United States, TN, Memphis
Joined Jun 2011
1,196 Posts
I have a 2805 here also but it's 2s only, correct?
I was considering it to save weight just wasn't sure about the power.

Thanks for all the info!
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Old Jun 15, 2012, 11:26 AM
Registered User
Vienna, Austria
Joined Apr 2007
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EMAX 2805 2850kV on 3s

it will run on 3s - like every motor, if you use the right prop. On 2s 6x4 is fine, on 3s 4,5x4,5 will work as you see in the video, I think it's around 18A on a full pack, so you need a 20A ESC, and the ESC will work hard supplying the field rotations. Turnigy ESCs make it (more than 20000 revs at a 12 pole motor mean more than 240.000 field changes per minute, some cheap ESCs are not up to the job).
The motor needs good cooling, and lube the bearings, they're the weak point on these 2805, at least the old ones had narrow bearings, maybe they changed it.
Motor should not get hot, if it does, bearings are too tight. I had that. Loosen the hex at the front fixing the bell on the shaft, move the shaft a bit so there is more freeplay. In a pusher the bell will be pushed against the mount anyway. Cured my problem, but it's still a bit loud as you can hear in the video. But motor cool again.
The AXN Floater Jet Clouds Fly replacement motor is in stock again at HK, that is made for pusher applications, and I would regard it superior at least to the 2812 EMAX. The 2805 EMAX is a lot lighter though, so if you are looking for a very light setup, this might be for you. Otherwise consider the AXN motor turning 5x5 TGS on the Parkjet, that should be a good power system (had the same bearing issue on my old 2812, loosened it, now better. But the later 2812 might have bigger bearings, like my newer 2822)
cheers
Clemens
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Old Jun 15, 2012, 06:32 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
9,004 Posts
Quote:
Originally Posted by A Useless Geek View Post
Does that include getting bent by the torque, power, or vibration of the motor? What about the fact that the motor mass is hanging off of an essentially unsupported plate (only one side supported)? I've always wondered how well those kinds of mounts hold up.
Go to your local hardware store and check out one of those L brackets ... it's far stronger and better than any mount I've had before - including the alloy mounts.

It does not bend with torque - the foam itself does.

Unsupported plate ? Check out the alloy mounts - same.

How does it hold up ? On PKJ1 - the mount has survived 3 motors without any sign of stress at all. The Alloy mount I bought specially for large motor snapped of and is why I went for a DIY mount.
Believe me - It works .......
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Old Jun 16, 2012, 01:33 AM
ICrashRCs
United States, TN, Memphis
Joined Jun 2011
1,196 Posts
Clemens,
Thanks again for the info. The video is great btw.
I just ordered a couple of axn motors and a few more 3s 800's.

I've got to build 2 lite Strykers soon so I'll have my bases covered on choices for them too.
Knowing I can run the 2805's on 3s really changes the game since they are so light.

You didn't like the APC 6 x 4 Sport with the axn motor?
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Old Jun 16, 2012, 10:13 AM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
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So a few photos of the final setting up of PKJ2 ...

Canopy is held by two bolts, one either side of mid length, to captive nuts in the base ....



2 velcro straps inside to hold various LiPos ... these are STITCHED through to the rails underneath to hold down.



Small separate RX battery (280mAh ... I have charging capability at field, even with gyro should get 3 flights minimum per charge)



GA-250 Mini Gyro on ailerons controlled by gear switch ... on/off. Set to rate mode when on.



4400kv Heli motor, with 60A ESC



The biggest problem is the amp draw .... with 5x5 prop and a 4S LiPo ... she draws 92A at WOT initially falling of rapidly to register over 1000W .....
With a 3S she initially showed 84A, falling of to show over 800W. I have no choice but to limit back the throttle to save the LiPo's and ESC ....
Throttle is at 10% !! EPA and showing 600W. I have higher amp ESC - but its so big ....

The quest for speed is a difficult road !! Somehow I have to find a way to get same RPM and prop use ... but lower amp draw ...

I may swap down to the 3800 smaller Heli motor I have (designed for 250 size heli's).



Nigel
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Last edited by solentlife; Jun 16, 2012 at 10:22 AM.
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Old Jun 16, 2012, 10:59 AM
Registered User
Vienna, Austria
Joined Apr 2007
2,134 Posts
Quote:
Originally Posted by IFlyRCs View Post
Clemens,
Thanks again for the info. The video is great btw.
I just ordered a couple of axn motors and a few more 3s 800's.

I've got to build 2 lite Strykers soon so I'll have my bases covered on choices for them too.
Knowing I can run the 2805's on 3s really changes the game since they are so light.

You didn't like the APC 6 x 4 Sport with the axn motor?
Have not tried the AXN motor but the reviews are great, and it's made for pusher applications, and I like the kV (2150, just right IMHO).
It depends on the model what prop is suited best - on the small & slim Parkjet a 6x4 is a waste of power since the Parkjet doesn't need all that thrust, and a 5x5 would be faster. On a Stryker the 6x4 will probably give you similar top speed (except in a steeper dive) but much better vertical than the 5x5, so I would also prefer a 6x4 on a Stryker, maybe try a 6x5 which might be an even better compromise, but amps will go up.
PS: glad you liked the video!
cheers
Clemens

EDIT: Just stumbled over two interesting graphs, made by Juergen Heilig some time ago. Good illustrations of the difference between 6x4 and 5x5 props, and the power requirements when going faster. 8 times the power for twice the speed, it's a bit sad ;-)
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Old Jun 16, 2012, 11:04 AM
Registered User
Vienna, Austria
Joined Apr 2007
2,134 Posts
Quote:
Originally Posted by solentlife View Post
So a few photos of the final setting up of PKJ2 ...
...

The biggest problem is the amp draw .... with 5x5 prop and a 4S LiPo ... she draws 92A at WOT initially falling of rapidly to register over 1000W .....
With a 3S she initially showed 84A, falling of to show over 800W. I have no choice but to limit back the throttle to save the LiPo's and ESC ....
...
The quest for speed is a difficult road !! Somehow I have to find a way to get same RPM and prop use ... but lower amp draw ...l
WOW, great model, and powerful setup. Why not use a TGS 4,5x 4,5, that would bring the amps down into more reasonable regimes, and should still give enough thrust for very good speed. Speed will go up quite a bit in a dive with the 4,5x4,5, but I think the aerodynamics of the PJ are good enough for 4,5x4,5 to work pretty well. The TGS / EMP delivers excellent thrust for such a small prop (and compared to other brands). They cost virtually nothing, so it might be worth giving it a try. If my rather draggy MPX Microjet (see video) perfoms good on this prop, it must be even better on the Parkjet
cheers
Clemens
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Old Jun 16, 2012, 04:12 PM
222 km/hr Parkjet flyer
solentlife's Avatar
Latvia, Ventspils pilsēta, Ventspils
Joined Jan 2010
9,004 Posts
2627 3800kv motor fitted after the larger literally wound the mount screws out !



This draws 35A ...... trouble is now it's pushing the heat on the motor ....

I hope the 2832's I'm getting are better ...

Nigel
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Old Jun 17, 2012, 01:00 AM
ICrashRCs
United States, TN, Memphis
Joined Jun 2011
1,196 Posts
after the larger literally wound the mount screws out !

Say what?
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