250GT MODS

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Here are some pics of the modifications I've done to the HK250 GT.

Starting at the front, I added a piece of 1.5mm carbon fiber to the bottom of the battery mount to allow mounting the esc further forward which I needed to do to get a correct cg.

I added rectangular pieces of CF on the lower sides to stiffen the frame and I mounted the ends of boom support rods from the 500GT to try to stiffen up the boom.

I cut a notch on the top rear of the frame and added a "doubler" made again of 1.5mm CF in order to mount a HK401 gyro in the usual position.  As you can see, the clearence between the top of the gyro case and the flybar when it is tilted all the way down, is close, but it does clear.

I used nuts and bolts to secure the tail boom and the gyro mounting plate.

With these mods and gluing the main board in the HK401 and using foam to secure the gyro's two upright circuit boards and using a Turnigy DS480 servo and a very short servo horn, I finally managed to get rid of all the tail wag.

I also did a simple mod so I could use a canopy from the Helimax Axe CP.

As shown, I just glued a couple pieces of CF rod across the frame to hold the canopy.  This plastic canopy is larger and lighter than the stock fiber glass one. 

Here is a front side view:

I'm using the "Super Tail Belt for TRex 250", which I think uses Kevlar reinforcing threads.  I got it from Infinity Hobbies.  73 flights so far on this belt with no signs of wear.  

If anyone would like detailed photos of the gyro mount, I'll be happy to post some.

Happy flying! 

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Heli_Flyer Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum (US) USERID: 115636 Bargain Addict! Joined: 26/Feb/2009 Online Status: Offline Posts: 52	Quote Reply Topic: 250GT MODS Posted: 08/Oct/2010 at 8:11am
	Here are some pics of the modifications I've done to the HK250 GT. Starting at the front, I added a piece of 1.5mm carbon fiber to the bottom of the battery mount to allow mounting the esc further forward which I needed to do to get a correct cg. I added rectangular pieces of CF on the lower sides to stiffen the frame and I mounted the ends of boom support rods from the 500GT to try to stiffen up the boom. I cut a notch on the top rear of the frame and added a "doubler" made again of 1.5mm CF in order to mount a HK401 gyro in the usual position. As you can see, the clearence between the top of the gyro case and the flybar when it is tilted all the way down, is close, but it does clear. I used nuts and bolts to secure the tail boom and the gyro mounting plate. With these mods and gluing the main board in the HK401 and using foam to secure the gyro's two upright circuit boards and using a Turnigy DS480 servo and a very short servo horn, I finally managed to get rid of all the tail wag. I also did a simple mod so I could use a canopy from the Helimax Axe CP. As shown, I just glued a couple pieces of CF rod across the frame to hold the canopy. This plastic canopy is larger and lighter than the stock fiber glass one. Here is a front side view: I'm using the "Super Tail Belt for TRex 250", which I think uses Kevlar reinforcing threads. I got it from Infinity Hobbies. 73 flights so far on this belt with no signs of wear. If anyone would like detailed photos of the gyro mount, I'll be happy to post some. Happy flying!

tornadorc Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum (AU) USERID: 302452 HobbyKing Constituent Joined: 05/Sep/2009 Online Status: Offline Posts: 131	Quote Reply Posted: 11/Oct/2010 at 9:20am
	more pics please, a full pic of the heli both sides. also that heli max cover fit ok? or did you had to mod it to fit? those 4 main bolt at the back that holds the boom, with nuts, are they stock? what size are they? how is the tail now?

tornadorc Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum (AU) USERID: 302452 HobbyKing Constituent Joined: 05/Sep/2009 Online Status: Offline Posts: 131	Quote Reply Posted: 11/Oct/2010 at 9:21am
	wiring pics to please :)

Heli_Flyer Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum (US) USERID: 115636 Bargain Addict! Joined: 26/Feb/2009 Online Status: Offline Posts: 52	Quote Reply Posted: 15/Oct/2010 at 7:27am
	Hello tornadorc, Here are a few more pics. The left side shows most of the wiring. The top view also shows some wiring. The close up of the tail support rod shows the connection at the fuselage "stiffiners" I added, looking from the bottom. I used a piece of 2-56 threaded rod, approx. 49 mm long with 2 lock washers and 2 nuts on each side. The four bolts holding the tail boom on are not stock. I removed the "inserts" from the stock metal boom holder and drilled out the holes to accept 2-56 machine screws. 2-56 equals about 2.13mm. You would need bolts about 24mm long. These bolts do hold the boom very firmly, but they don't by themselves prevent tail wag, I think because the boom itself is made of very thin walled tubing, so it flexes easily, and there is very little support for the boom in the fuselage. Good luck with your 250.

Heli_Flyer Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum (US) USERID: 115636 Bargain Addict! Joined: 26/Feb/2009 Online Status: Offline Posts: 52	Quote Reply Posted: 15/Oct/2010 at 7:30am
	Oh, and the canopy is stock except for the holes added for the top rear attachment. The hole just in front and below is the "stock" hole.

Sooty Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum (NZ) USERID: 173750 Hobbyking Addict Joined: 10/Mar/2009 Location: Christchurch NZ Online Status: Offline Posts: 2647	Quote Reply Posted: 17/Oct/2010 at 3:32am
	The gyro will get taken out by flybar in a heavy landing - cheap to replace though. I learned the hard way by doing it to an expensive Futaba gyro.

engineersupreme Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum (NZ) USERID: 454864 HobbyKing Constituent Joined: 29/Apr/2010 Location: Timaru, NZ Online Status: Offline Posts: 205	Quote Reply Posted: 19/Oct/2010 at 6:19pm
	I see the 250 was coming back into stock then its on backorder again. Have managed to find some and will reread your post and mods when starting to build those Thx for info on what you have done
	NEVER under any circumstances take a sleeping pill and a laxative on the same night.

flarssen Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum (NO) USERID: 3342 Hobbyking Addict Joined: 15/May/2009 Online Status: Offline Posts: 1248	Quote Reply Posted: 19/Oct/2010 at 6:34pm
	Are there any 250 size plastic canopies available? My FG one already have cracks in the gelcoat in the rear part after just sitting waiting for me to put the thing together. Was pretty malformed anyway. I have started assembly and plan to try 3S A123 1100 on 4200Kv with CC-10 + ParkBEC. CG might be a challenge though, hence looking for a lighter canopy.

Heli_Flyer Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum (US) USERID: 115636 Bargain Addict! Joined: 26/Feb/2009 Online Status: Offline Posts: 52	Quote Reply Posted: 20/Oct/2010 at 12:11am
	A few months ago I tried to find a 250 size plastic canopy with no luck. I used the Helimax canopy because I had it on hand. I would expect that many micro size heli canopys could be used but there is no way to tell which ones without buying a bunch of them.

dude7422 Members Profile Send Private Message Find Members Posts Add to Buddy List Platinum (US) USERID: 156650 Hobbyking Addict Joined: 28/Feb/2009 Location: Pa. USA Online Status: Offline Posts: 532	Quote Reply Posted: 20/Oct/2010 at 12:14am
	no bends in wire sharper then 5 times the radi. of wire it makes a hot spot .. the front of esc wire is a BAD bend how many wish that the gyros that we all use.,, had a female plug into the side no wire coming out for the servo connection