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Old Jan 13, 2010, 06:00 AM
Gone Flying.
ChrisWNY's Avatar
Western NY
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The belts are known to be cheap and several others within this thread have had belt failures with the stock HK-250/GT belt. Replace the belt with the Align T-Rex 250 belt and you'll be good to go, they are about $5 for two...
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Old Jan 13, 2010, 08:11 AM
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Sir J David's Avatar
Sweden
Joined Dec 2007
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Quote:
Originally Posted by Brettw View Post
Mate had the same problem however worked well with the esc placement as mentioned previously.

You should not need to remove any of the frame to mount it this way.

Just remember to cut the top of the shaft off the motor or it will rub on the cyclic servo's.

Brett
I chosed to put my cables to the right front but I removed a little of the frame to avoid damage of the motor cables. Probably not needed..


About tail belts... I have noticed that the tail belt pulley (upper gear) at some 250 kits is not so good centered, causing the gear to wobble. I guess this will short the time before the belt strips.

Anyone else here who have the copterx250? It seemes to be the same as skya/exi/hkgt with only the metal changed to cx-blue (well, it also have landing skid legs separated from bottom plate and chinese weights).
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Old Jan 13, 2010, 09:23 AM
Rotortech.ca
Edmonton, AB Canada
Joined Oct 2006
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Quote:
Originally Posted by rcnewb View Post
The belts are known to be cheap and several others within this thread have had belt failures with the stock HK-250/GT belt. Replace the belt with the Align T-Rex 250 belt and you'll be good to go, they are about $5 for two...
+1 to this, my HK250GT threw the belt on it's 5th flight. The stock Align belt is the only way to go. I'm curious to see how good the belt is on the CX250.
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Old Jan 13, 2010, 09:32 AM
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Originally Posted by Stump3r View Post
+1 to this, my HK250GT threw the belt on it's 5th flight. The stock Align belt is the only way to go. I'm curious to see how good the belt is on the CX250.
I honestly believe that cx250 comes from the same factory as the rest of the clones. I can't notice any difference of the parts (except from the skids and the blue instead of black metal parts). I have still not flewn my cx250.
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Old Jan 15, 2010, 04:58 AM
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Maiden flight today was a disaster.

Im running a 2627 4200 with a 12t pinion and it took almost full stick to get it to even look like it was going to get off the ground.

Then it shot up 12 ft and I all I could do to get it back down was to drop the throttle which saved it a little. So im up for a boom and set of blades that I can see from a quick look.

Is anyone using this motor and are you using a 12t pinion with what pitch/throttle curves.

Thanks
Brett
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Old Jan 15, 2010, 05:36 AM
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Sir J David's Avatar
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Originally Posted by Brettw View Post
Maiden flight today was a disaster.

Im running a 2627 4200 with a 12t pinion and it took almost full stick to get it to even look like it was going to get off the ground.

Then it shot up 12 ft and I all I could do to get it back down was to drop the throttle which saved it a little. So im up for a boom and set of blades that I can see from a quick look.

Is anyone using this motor and are you using a 12t pinion with what pitch/throttle curves.

Thanks
Brett
I use the same motor setup as you. Abut +/- 10 degrees. It flyes ok but I have only had one flight yet...
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Old Jan 15, 2010, 06:05 AM
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UK
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Quote:
Originally Posted by Brettw View Post
Maiden flight today was a disaster.

Im running a 2627 4200 with a 12t pinion and it took almost full stick to get it to even look like it was going to get off the ground.

Then it shot up 12 ft and I all I could do to get it back down was to drop the throttle which saved it a little. So im up for a boom and set of blades that I can see from a quick look.

Is anyone using this motor and are you using a 12t pinion with what pitch/throttle curves.

Thanks
Brett
From what you've described - it might be that you have some kind of binding or stiff links or something like that... Why would motor suddenly give that much power?

Did you notice sudden increase of RPM or not? If not - is it possible that your curve is wrong? Or links got stuck somewhere?

I had similar problem with old Walkera 22e - it was slowly adding throttle and nothing was happening while motor was increasing RPM gradually until it didn't just shot into the air - but that's well known problem with that heli - stiff links! Check them on the ground - switch the motor off (or just put throttle hold switch on) and slowly change collective pitch. Is it going smoothly?

Also - test cyclics at the same time - are you moving the swash plate accordingly? Test it at different throttle stick positions...
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Old Jan 15, 2010, 06:49 PM
I Can Fly An FP Inverted!
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Teddington, Middlesex, UK
Joined Jun 2008
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Quote:
Originally Posted by Brettw View Post
Maiden flight today was a disaster.

Im running a 2627 4200 with a 12t pinion and it took almost full stick to get it to even look like it was going to get off the ground.

Then it shot up 12 ft and I all I could do to get it back down was to drop the throttle which saved it a little. So im up for a boom and set of blades that I can see from a quick look.

Is anyone using this motor and are you using a 12t pinion with what pitch/throttle curves.

Thanks
Brett
I had the same problem as you to start off with, it was traced back to slop in the pitch control, i had to replace the seesaw bushings with bearings, and replace the washout base in order to rectify the problem
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Old Jan 16, 2010, 10:57 AM
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St-Hilaire,Québec,Canada
Joined Sep 2001
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Was supposed to get my first outdoor flight today but it's quite windy... not sure I'm going to try it finnaly
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Old Jan 16, 2010, 10:10 PM
Gone Flying.
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Western NY
Joined Nov 2006
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Just wrapping up the build of my 250GT - did any of you have issues with the right-hand servo rubbing against the canopy? The canopy seems warped or something and doesn't appear to fit very well at all. I'm probably going to need to replace it since the servo arm would not clear the canopy.

I replaced the stock belt with an Align T-Rex 250 belt, just for testing, I pulled on the stock belt as hard as I could to see when it would break, it took brute force to break it, and looking closely at the belt, it looks nearly identical to the Align belts. Perhaps HK is using higher quality belts now based on the track record of them breaking in the earlier batches.
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Old Jan 17, 2010, 12:18 AM
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Saitama, Japan
Joined Aug 2009
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Originally Posted by rcnewb View Post
Just wrapping up the build of my 250GT - did any of you have issues with the right-hand servo rubbing against the canopy? The canopy seems warped or something and doesn't appear to fit very well at all. I'm probably going to need to replace it since the servo arm would not clear the canopy.

I replaced the stock belt with an Align T-Rex 250 belt, just for testing, I pulled on the stock belt as hard as I could to see when it would break, it took brute force to break it, and looking closely at the belt, it looks nearly identical to the Align belts. Perhaps HK is using higher quality belts now based on the track record of them breaking in the earlier batches.
I've found HXT900 to stick out quite a bit, so I installed my servos with the tabs on the inside of the frame. (makes maintenance a pain in the ass, but the build looks cleaner)
Even then the arms touched the stock canopy, so I just ended up buying the wider Fusuno canopy.
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Old Jan 17, 2010, 01:04 AM
Gone Flying.
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Western NY
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Hey mark -

I switched my servos and installed them with the tabs inside the frame, what a bear. They BARELY fit in that way, but they do stick out less now. The other problem with installing with the HXT900 tabs inside is that the bolts will hit the main shaft on the 2 front servos unless you use washers. I don't think I'd attempt installing them that way again unless I completely disassembled the frame. I'll look into a wider canopy I guess, the stock canopy does not allow for much room inside.
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Old Jan 22, 2010, 08:05 AM
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So I read earlier in the thread that the stock feathering shaft is an explosion waiting to happen (250GT). Can someone confirm whether or not this is really the case? I've spun up to full RPM (Scorpion 2206-3900Kv motor, 14T, 3S 1000mAh 15C LiPo pack) and it tracks/spins smoothly with virtually no vibration (I didn't even have to adjust the blade tracking, set my linkages as per the T-Rex 250 manual and all is well).

One thing I've noticed is that at full negative, with cyclic forward, the HXT900 servo arm (the lower servo on the front) nearly touches the main gear, I've sanded it down quite a bit to eliminate the issue, but it's still very close. I found that if the servo arms weren't SLIGHTLY down at neutral, that there would be too much positive pitch (to the point of binding) and not enough negative, I like to set heli's up for equal -/+ pitch. Also had to use quite a bit of subtrim on 2 out of 3 of the cyclic servos.

My only gripe with the 250GT is the canopy, the one side seems warped and there is not enough room for my 3S 1000mAh 15C LiPo (Zippy) pack inside the canopy. Still need to tidy up wiring as I used an external BEC for the Rx/servos, which means a few extra wires to bundle up. Is anyone else using the 3S 15C 1000mAh Zippy's? Any advice on how to fit the d@mn thing within the stock canopy?
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Old Jan 22, 2010, 08:12 AM
I Can Fly An FP Inverted!
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Teddington, Middlesex, UK
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Quote:
Originally Posted by rcnewb View Post
So I read earlier in the thread that the stock feathering shaft is an explosion waiting to happen (250GT). Can someone confirm whether or not this is really the case? I've spun up to full RPM (Scorpion 2206-3900Kv motor, 14T, 3S 1000mAh 15C LiPo pack) and it tracks/spins smoothly with virtually no vibration (I didn't even have to adjust the blade tracking, set my linkages as per the T-Rex 250 manual and all is well).

One thing I've noticed is that at full negative, with cyclic forward, the HXT900 servo arm (the lower servo on the front) nearly touches the main gear, I've sanded it down quite a bit to eliminate the issue, but it's still very close. I found that if the servo arms weren't SLIGHTLY down at neutral, that there would be too much positive pitch (to the point of binding) and not enough negative, I like to set heli's up for equal -/+ pitch. Also had to use quite a bit of subtrim on 2 out of 3 of the cyclic servos.

My only gripe with the 250GT is the canopy, the one side seems warped and there is not enough room for my 3S 1000mAh 15C LiPo (Zippy) pack inside the canopy. Still need to tidy up wiring as I used an external BEC for the Rx/servos, which means a few extra wires to bundle up. Is anyone else using the 3S 15C 1000mAh Zippy's? Any advice on how to fit the d@mn thing within the stock canopy?
the stock feathering shaft is actually made out of a new kind of alloy developed by hobbycity specifically for use on their helis, its a combination of aluminium and chedder. (just use a genuine align part, its ~£3 that will prevent a ~£30 crash/injury)

I also had a similar problem with the maingear and servo horn touching (when at maxx pitch, and you input cyclic it does actually rub)

I had to move the horn one spline up and shorten the linkage rod (just snipped off about 2mm and screwed the cup back on)

zippy 1000mah 15C lipos are on the heavy side for this bird, and will perform poorly. *ideal* batteries are ~800mah and at least 25C.

and you should try to avoid subtrim as much as possible, try to level the swashplate using just the spline position/linkage length (i dont reccomend any more than 35 on a dx7)
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Old Jan 22, 2010, 08:47 AM
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Really? The 1000mAh 15C packs are 83g, the 800mAh 20C packs are 78g, if anything I needed a few more grams up front, I'm using a Park HPX-F servo for rudder, and a HK 401B Gyro, which adds a few extra grams in the rear. The guys who fly T-Rex 250's in my club all use 1000mAh packs. In terms of Amp draw potential, the 1000mAh 15C can put out 15 Amps continuous, that is plenty, an 800mAh 20/25C would ouput 16/20 Amps continuous (that's not a significant difference), that is above the rating of the motor anyway (14 amps is the rated MAX continuous current for the Scorpion 2200-3900KV motor).

I didn't want to use a battery that would (A) send my RPMs way into the upper 4000 range or (B) cook my motor. One of the guys in my club who flies competitively insisted that the 1000mAh packs were the way to go, you get a couple of minutes of extra flight time with minimal weight penalty. Based on my EagleTree testing, I was able to pull 18+ Amps out of the Zippy 1000mAh 15C without any voltage sag whatsoever. They are nice batts, sometimes the discharge rating is conservative on them. In retrospect, however, the 800mAh packs would have probably fit more nicely within the canopy, the 1000mAh are a bit wide and I think that is the issue I'm having.

Thanks for the tips on the linkage adjustments, I will shave 2mm off the links and put the arms up 1 spline, otherwise I'll be rubbing the main gear with the HXT900 servo arm. I hesitated to shorten the arms as I didn't want to lose the distance of travel in the swash as it seems fairly perfect right now, but I agree that things should be as mechanically perfect as possible to minimize subtrims within the radio.

Since I have the Align 250 feathering shaft, I'll go ahead and replace the cheesy stock shaft. However, I can't imagine the stock shaft bending unless it was in a crash. Are they bending spontaneously during normal flying conditions? That seems really bizarre IMO.
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