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Old Apr 22, 2007, 10:20 PM
treefinder
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SE MI
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Another question about j250 and 3x3 props. I put one on today in pusher mode, and the prop worked it's way right up against the motorhub in flight and slowed it way down. How do you keep it solidly mounted? CA? dab of hotmelt on hub? what's the best?
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Old Apr 22, 2007, 10:29 PM
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Southern Vermont
Joined Feb 2007
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Springer,

good to hear you're flying in the wind and doing new things.

Don't try the 5x3 prop that I'm using (mentioned earlier) on your J250.

Remember, I'm using that prop on a 180 direct drive motor which runs at a lower speed and amperage than the J250.

I think you have the largest prop advisable for the J250 motors direct drive.

I have some J250s now and will try them in Trainer One once I get the props I ordered almost a month ago. 4x2 and 3x3 as GPW recommends. I also have a 4.5 x 2.5 ( I think -- it's a used prop). Seems to draw 4.5 to 5 amps static on the J250 I have. So maybe I'll try that. The J250 is a DCM-189 type, by the way.

Tangled with another tree today, but this time only 100 feet from home so i can keep an eye on the plane -- it isn't stuck bad -- few twigs, but there was no wind at all yesterday to blow it out of the tree. Naturally, that's when I got stuck.
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Old Apr 22, 2007, 10:40 PM
treefinder
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SE MI
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I was just going back through the posts to figure out what motor you were using, cause I was guessing the 5.3 would be too much for a j250. sorry to hear about the plane eating tree. Isn't it always the best weather when you can't fly?

I actually launched mine from close to house today. Had gone way back to open fields before. So I was a little concerned that I might trash it, didn't get anywhere near the nearby obstacles, but when i brought it down in the next field, I couldn't see the last 30 ft or so (fence row trees), so guessed when to try a flare and she landed without damage (course she has the fat nose bumper for that )

Once I solve the "sliding prop" problem, I'm gonna try a 3x3 just to see how that changes performance. Wonder if roughing up the shaft with 400 grit wetordry would help?
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Old Apr 22, 2007, 11:35 PM
treefinder
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gpw: I'm clueless. BP is BPhobbies i guess, but who are FB and BH? and is the BP-21 a brushless outrunner motor?
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Old Apr 23, 2007, 07:28 AM
gpw
“There’s no place like Foam”
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Sorry Spring, I got in the bad habit of abbreviating everything ...
FB is flying buddy BH is the new name for Balsa Hobby(Balsa Products), I never get the new name right ...still enjoy their services anyway ...
The BP-21 is a nice ,inexpensive brushless outrunner , better for the larger planes like the T-150%...
A drop of ca on the j250 shaft should hold wayward props...or a few nicks with some diagonal cutters, careful you don't chop off the shaft

Got to fly the FMS version of the T-1 ... doesn't fly anything like a real one ... it's so unstable and lacks the self recovery of the genuine article ...
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Old Apr 23, 2007, 10:05 AM
treefinder
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gpw: No prob on the abbreviations, saves typing time! I guessed right on the balsaproducts but went searching in the inrunner list, obviously didn't find anything will try again. Have to check out flying buddy, haven't heard of them. Thanks for the tip on props, will fix that prob today. too windy to fly so must tinker. Also glad to hear you finally got FMS! I recall the T1 model seemed to "hobby horse" way more than my real one. Guess if i can fly the model, the real one should be easier Have you tried the stealth sport model? That model seems really smooth in FMS. A "go where you point it" vs the t1 model that never seemed to quite go where I wanted it. I attributed it to the old "Do what I want not what I tell you" problem common to computer things. I suppose one could tinker with the model parameters. . . .
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Old Apr 23, 2007, 10:13 AM
gpw
“There’s no place like Foam”
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"Have to check out flying buddy, haven't heard of them. "...the guys you fly all the time with...yeah, those guys...
The FMS SS FLIES GREAT !!!!
BP-21 @ BP, er BH http://www.bphobbies.com/view.asp?id...97&pid=U422859
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Old Apr 23, 2007, 11:04 AM
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Southern Vermont
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You might also try United Hobbies -- they have an ESC Motor Prop combo for $14.49 the Towerpro equivalents of the original BP-21. That BP-21 designation covers several motors by the way -- they've changed over time. It used to be the 2408-21T, now I'm not sure. Anyway UH has most of the Towerpro motors in combo deals here:

https://www.unitedhobbies.com/UNITED...&ParentCat=192


Got my plane out of the tree again with a long pole and a ladder, phew!
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Old Apr 23, 2007, 11:17 AM
gpw
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I can't impress the necessity enough of staying AWAY from trees..once you start climbing , it becomes a dangerous activity...especially for us old guys ...
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Old Apr 23, 2007, 11:36 AM
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Southern Vermont
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Here is a chart of all the Towerpro motor specs.

The 2408-21T is one of the lighter in weight at 50 grams. However it's a pretty high draw motor. Peak efficiency is at 14 amps.

Something I noticed -- If you look down the weight column you will come to the 2406-32T at 35 grams and a very low Kv of 980. It's lighter than any of the other motors.

Kv is the number of RPM per volt. The lower it is, the larger prop you can use, relatively speaking. It's like gearing in a way. As the number goes low the torque goes up and RPM goes down.

Our little j250 for example has a high Kv of about 4000 and thus swings a very small prop.

This Towerpro motor intrigues me -- I haven't seen anything written about it. It would seem to require a smaller battery than the others, yet swing a big prop, as well as weigh less -- its max efficiency current is around 8 amps.

What this would probably mean is it would be great for a really light AUW compared to the others, with high efficiency and low amp draw. I think it would work well with Nimhs as well.

It is more expensive than the others -- UH lists it at $16.95 for the motor alone.

Maybe some day I'll get one and try it out for a nice lightweight build.
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Old Apr 23, 2007, 12:00 PM
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GPW Thanks. Trees, yes I wish I could always stay away from them.
But I'm surrounded GPW. Small fields in the hills surrounded by trees on all sides.

From the french:

Ver = green
mont = mountain

This is RC bush piloting country. STOL flying is going to be a fact of life for me here, and any mistakes or sudden wind shifts, etc. are as likely to end up treed as plowed in .

But it teaches new techniques -- and that skill is fun to learn right now. Spiraling in and out is important. I see that. I'm getting better at that. Not perfect, but better.

My ideal plane would be designed for this kind of flying -- good lift in a turn -- high lift wings, etc. A long shallow glide isn't a benefit, unless the motor dies far away. But it would be nice to dump lift close in and really plant it when you want.

Re climbing -- don't worry, I was a professional tree climber when I was younger, and do tree work now on my property -- I built a bandsawmill and built the house with it. I was careful removing the plane, and only 4 feet off the ground on the ladder anyway. Made up a 25 foot pole. Been thinking about designing a really light long stiff collapsible retrieving pole.
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Old Apr 23, 2007, 12:42 PM
gpw
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Vtd ... you need a Hoot !!! Stable(self righting) , glides like stone .. flies very close in , high alpha kinda stuff .. that or a Dart ...
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Old Apr 23, 2007, 02:58 PM
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Southern Vermont
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a hoot?
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Old Apr 23, 2007, 04:32 PM
Tinkerer
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RI
Joined May 2005
184 Posts
Quote:
Originally Posted by vtdiy
Re climbing -- don't worry, I was a professional tree climber when I was younger, and do tree work now on my property -- I built a bandsawmill and built the house with it. I was careful removing the plane, and only 4 feet off the ground on the ladder anyway. Made up a 25 foot pole. Been thinking about designing a really light long stiff collapsible retrieving pole.
Speaking of which, I've found that the plastic electrical conduit from Lowes or Home Depot make for great plane-recovery material: easy to add 10 feet at a time, although at about 30 feet it gets a little hard to handle -- kinda like trying to poke something with a piece of wet spaghetti. But it breaks down nicely for transport to/from home :-)

--Spike
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Old Apr 23, 2007, 06:34 PM
Master of 1 point landing
Naperville, IL
Joined Jul 2005
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Quote:
Originally Posted by jfhspike
-- kinda like trying to poke something with a piece of wet spaghetti.
--Spike
LOL - reminds me of late night tv ads or one of the million ads Pfizer has out. Dont poke around with wet spaghetti - try sildenafil citrate and increase the satifisfaction of your plane! Sorry, off topic, but my mind is very strange today.
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