HK-250 with fixed pitch head conversion

[HELIHANKSTER]

First I would like to say thanks to johnnycat500...it was his fixed pitch 250 conversion that inspired me to go ahead and build my own FP 250. This is his concept, not mine…I just follow his build and built mine using the Xtreme cnc FP head assembly and wanted to share.

My HK 250 was already built so I had to remove the cp head/main shaft and I found it easier for me to swap out bearings by remove the main shaft bearing blocks from the frame. The HK-T250 and HK-GT250 kits comes with the frame per assembled with the main shaft blocks installed. You can swap out bearings with the blocks mounted in the frame, but I would recommend removing them so as not to damage the frame when pressing in the Honey Bee 7mm by 3mm bearings into the block.


The bearings I will be using to replace the stock bearings with are the main shaft bearings for the Honey Bee V2.


Removed the brass sleeves from the Honey Bee V2 bearings and removed the stock 250 bearings from the main shaft blocks.


Installed the Honey Bee V2 7mm by 3mm bearing into the HK 250 main shaft block and reinstall bearings blocks back into the frame.


1. Slide Xtreme or HB V2 shaft down though top and bottom bearings.
2. Place washer on shaft between bottom bearing and the top of the main gear.
3. Install main gear onto shaft ( push enough shaft though the bottom of the main gear to be able to install the bottom lock collar)
4. Install bottom lock collar
5. Install top lock collar


Bottom view of 3mm shaft installed


Top view of 3mm shaft installed.


That’s it!…3mm shaft is secured in HK 250 frame…too easy right…no cutting or drilling of the Xtreme shaft…sweet! The best part about this mod is you can loosen up the lock collars and rise or lower the main shaft to what ever position you need to make the fixed pitch head assembly that you are using fit right.


Elevator and Pitch Servo (placement) installed


Xtreme head assembly installed.
The head was already assemble on one of my V2s so I simply drop it on the shaft and secured it with the bolt and nut that come with the Xtreme shaft. There are plenty of thread on the installation on the Xtreme head and Bell-Hiller mod that I felt is was not necessary to do a step by step head build.


Center and leveled servo horn and installed linkages. I used the HK 250 linkage rod and ball ends at the servo horn and used the V2 ball ends on the top of the linkage that connect to the cnc swash plate.


I throw on a set of Xtreme fiber blades that were not trimmed and spun out the bird on my turn table to setup the tail. I spend 20 minutes trying to get the tail to hold… but can’t…the blades were producing too much Yaw thrust that the small 250 tail just couldn’t hold. Then I remember that John had cut his blade down…I thought the only reason why he cut down the blades was for clearance between the main blades and tail blades…boy was I wrong. I didn’t want to cut up my Xtreme fiber blades so I decide to trim a set of stock v2 blades that I had laying around. Since I was cutting the blades down anyway I decided to do a experiment. I took one of the stock HK 250 blades and placed it over top of the stock v2 blade and trace it out, then trimmed the v2 blade to the same size as the HK 250 blade. I really didn’t think the trimmed V2 blade had enough surface area to create lift, but to my surprise the blades work great! (KA-CHOW!)


Trimmed down V2 blade installed on helicopter.


Side view of trimmed blade

[HELIHANKSTER]

Components used and placement


Because of the placement of the elevator servo the stock canopy wouldn’t fit right…so to solve this problem I cut vent openings in the side of the canopy. The openings allows the servo to stick out and lets the motor breath at the same time…sweet!


Finish canopy…Yeah it’s not pretty but it works.


Front view


Side view ( almost forgot to say which flybar and paddles I’m using on this little demon)


Over the past three years of flying FP RC helicopters and modding them to the extreme I have to say that if you factor in cost to build…this is the ultimate…the best performing FP helicopter that I have ever flown.

Not counting my receiver
HK-250 kit………………………………................................... ...............................................$29 .99
Xtreme head with bell-hiller, PCF and swash plate………………………………...................$92.20
Turnigy 2627 brushless motor………………………………................................. ..................$12.01
Mystery 20 amp brushless ESC………………………………................................... ..............$10.99
Using Align gyro, but will probably stick one of my Turnigy 302 gyros on it………………….$24.79
Three HXT 900 servos………………………………................................ ...............................$8.07
FlyingHobby super belt……………………………….................................. .............................$4.95
Total…$183.00


You could cut this total price down to about a hundred bucks if you used a plastic fixed pitch head setup and a cheaper gyro. Personally I really like this setup, so I say sweet!!!!!!!!!!!!!!!

Well that's about it...Only one thing left...Here the second flight with the FP mod on my 250
[ame]http://www.youtube.com/watch?v=0My3p_Qn1pA[/ame]

[GAANDAHL]

Very cool! I'm looking forward to your impressions of the end product.....and some good videos.
GAANDAHL

[johnnycat500]

hey HH thanks for taking the time to do this thread. Your pics are great.Looking forward to the rest of the thread.

[HELIHANKSTER]

Originally Posted by GAANDAHL

Very cool! I'm looking forward to your impressions of the end product.....and some good videos.
GAANDAHL

I love this little bird...It might just become my favorite helicopter to fly...Yeah Baby!!!!

Originally Posted by johnnycat500

hey HH thanks for taking the time to do this thread. Your pics are great.Looking forward to the rest of the thread.

No Johnny thank you! You got the ball rolling...I'm just running with it.

Well I finished the build pictorial so I hope you guys like it and thanks for the support
Hank

[johnnycat500]

Great job HH When I put the bigger walkera ufly blades on I did cut them down so they would not contact the tail blades. In testing though you give it the gas and the tail can not keep up. I am using cb180 blades but really like your idea of putting the 250 blade on top and marking it.A wall and my exi250 fp had a fight and the wall won.so what a better time to get a trex 250 cf boom. I am really into photography. may I ask what camera you are using for this thread.The pics are killer.

[HELIHANKSTER]

Thanks John
Sorry to hear about the fight your FP 250 had with the wall… Hope you get it back in the air soon.
+1 on the carbon boom…when my boom gets bent up that’s what I’m buying…sweet!
Yeah I thought that was the reason you cut the blades down. The stock V2 blades cut down to 250 size seem to be working real good. They are giving the 250 good head speed and lift…the only thing that I’ve notice is that the blades will start to cone (give out) when I pull up from a high speed drive. I’m thinking a trimmed down (250 size) set of Xtreme 10degree woodies would make this little bird fly great.

It’s a Nikon coolpix L1

[FLThreeFiveZero]

Have you guys tried the 250 blades with like a wedge to give you the desired pitch? Then if you wanted to try different pitches you could just change out wedges.

[FLThreeFiveZero]

Hey Hank

Check this out I went over to Value Hobby to buy some SG90 servos (equivalent to a Hitec HS-55: 20.8 oz/in torq, 0.12 sec/60 deg @ 4.8v)
And now they carry some new servos that look like they might be kickazz for behind a gyro!!! ( 0.07 sec/60 ) and only $6.80!!!!
They also have a metal gear version that puts out 20 oz/in (at the same speed) for $8.90

http://www.valuehobby.com/products.php?category_id=60




they also have pretty good prices on Lipo's and ESC's

[Skyranger]

Anyone of you guys out there have the ring like connectors that connect the swash and control frame, not flybar to head, they would sell me. I need them fassst. PM me for address and what evr you need. Waiting on stuff from suppliers for a week. Regular mail takes 2-3 days. I'll owe you one, thanks, Dave....I have done this before, I will just do like grama use to do.....send you a bill.

[HELIHANKSTER]

Originally Posted by FLThreeFiveZero

Hey Hank

Check this out I went over to Value Hobby to buy some SG90 servos (equivalent to a Hitec HS-55: 20.8 oz/in torq, 0.12 sec/60 deg @ 4.8v)
And now they carry some new servos that look like they might be kickazz for behind a gyro!!! ( 0.07 sec/60 ) and only $6.80!!!!
They also have a metal gear version that puts out 20 oz/in (at the same speed) for $8.90

http://www.valuehobby.com/products.php?category_id=60




they also have pretty good prices on Lipo's and ESC's

Hi Bro
I’ve been thinking about using wedges for along time, but the surface area on the Xtreme head around the blade root area is small so if the blade moved side to side any… the wedge would probably fall out, plus you would have to run the blades super tight so the wedges don’t fall out in flight. It would be awesome just to use to 250 blades with wedges so if you got an idea on how to keep the wedges in place you have to share…it’s the Law…lol!

Dam those servos look sweet! And the one with the metal gears is only 5.75g…that’s light. Thanks for the link Bud
One question FL350 Do you think it will still be 0.07sec running it on a 5volt setup indeed of 6v. Hope so!

[JettaManDan]

sick dude!!

[FLThreeFiveZero]

Originally Posted by HELIHANKSTER

Hi Bro
I’ve been thinking about using wedges for along time, but the surface area on the Xtreme head around the blade root area is small so if the blade moved side to side any… the wedge would probably fall out, plus you would have to run the blades super tight so the wedges don’t fall out in flight. It would be awesome just to use to 250 blades with wedges so if you got an idea on how to keep the wedges in place you have to share…it’s the Law…lol!

Got it.

Ill have to go see what a Rex250 head looks like. I have a couple Gaui 250's I wonder how similar the Rex and Gaui heads are? I kow its nothing like my SJM 180's.....nothing is.

Originally Posted by HELIHANKSTER

Dam those servos look sweet! And the one with the metal gears is only 5.75g…that’s light. Thanks for the link Bud
One question FL350 Do you think it will still be 0.07sec running it on a 5volt setup indeed of 6v. Hope so!

Yeah the servo will be slower at 5v VS 6v. But it will still be faster than 0.10-0.12 sec
I'd guestimate like 0.085-0.09 sec..........still worth it IMHO.
With a slow servo the gyro can send out corrections faster than the servo can react and the gyro ends up having to correct corrections because the servo hasnt had time to react yet.

[Viet-Lama]

FL check out the torque on that servo, it only has .35kg at 6v and thats nothing. Now drop to 5v and you wont be able to steer.
Turnigy makes an 8gram servo (its black) with enough speed and torque to run great on both my 450s. Before I got my Logictech setup I ran it on the 250 and its not too big at all for the 250s small size. Only cost like $5 each, If your interested let me know and ill look up the link.

With a slow servo the gyro can send out corrections faster than the servo can react and the gyro ends up having to correct corrections because the servo hasnt had time to react yet.

Yep , if your gyro has a "delay" then you use it to compensate for the slower servo and eliminate tail wag.

[Viet-Lama]

HH your conversion is brilliant and I totally love it!
AWESOME JOB and of course gorgeous flying skills too

Must make that a sticky in the MOD section....MUST DO IT! Blows away the Guru Z and other expensive conversions that are made from cheap plastic components and parts that are near impossible to find as replacements. This conversion will work the same with the Align Trex 250 and 250SE and all parts are available almost everwhere. FYI, the HK250GT and the EXI 250 are the same (both manufactured by Skya) so the EXI can be converted as well.

Ill bet Xtreme 8degree blades would work great on that bird. Also remember that you can run larger (41mm i think) Align tail blades or KBDDs for better authority if needed.

[HELIHANKSTER]

Originally Posted by FLThreeFiveZero

Got it.

Ill have to go see what a Rex250 head looks like. I have a couple Gaui 250's I wonder how similar the Rex and Gaui heads are? I kow its nothing like my SJM 180's.....nothing is.
Yeah the servo will be slower at 5v VS 6v. But it will still be faster than 0.10-0.12 sec
I'd guestimate like 0.085-0.09 sec..........still worth it IMHO.
With a slow servo the gyro can send out corrections faster than the servo can react and the gyro ends up having to correct corrections because the servo hasnt had time to react yet.

Dude You have a couple of Gaui 255’s…sweetness! What size is the main shaft on those puppies? The great thing about this mod is you can always switch it back to a cp helicopter fairly easy and quick when you want to.

I was checking out the web site you give me for the servos/batteries and I saw they have the identical 250 kit as the HK-T250 Kit for the same price and they are in the U.S. Sweet!
http://www.valuehobby.com/product_de...46&item_id=297
I was so happy with this build that I was going to order another HK-T250 bare bone Kit to convert another one of my Bees, but HobbyKing was out of stock, so I was kind of bummed…but now I’m Happy. Have you place an order with ValueHobby before? Are they a good company to do business with?

[HELIHANKSTER]

Originally Posted by Viet-Lama

HH your conversion is brilliant and I totally love it!
AWESOME JOB and of course gorgeous flying skills too

Must make that a sticky in the MOD section....MUST DO IT! Blows away the Guru Z and other expensive conversions that are made from cheap plastic components and parts that are near impossible to find as replacements. This conversion will work the same with the Align Trex 250 and 250SE and all parts are available almost everwhere. FYI, the HK250GT and the EXI 250 are the same (both manufactured by Skya) so the EXI can be converted as well.

Ill bet Xtreme 8degree blades would work great on that bird. Also remember that you can run larger (41mm i think) Align tail blades or KBDDs for better authority if needed.

Thank Bud This is an awesome little bird to fly…I really think it makes for a perfect back yard flier. Don’t get me wrong…I love my Honey Bees, but this little bird is a Bee modders dream! It easy and cheap to build and its packed with everything one would want in a small back yard flier…brushless motor, belt drive tail, external gyro and the simplicity and toughness of a fixed pitch head setup. Every since I started modding my Bees this is what I’ve been looking for…that why I did the King 2 FP head conversion. I love flying FP helicopters a lot and wanted them to perform as good as possibly…without going to a cp setup.


Both sets of my Xtreme 8degree blades are being used on other birds and I dont want to cut them up just yet, but I do have a pair of guru-z 9s I could try


I've heared a lot about the KBDD blades, but untill now I've never had a reason to try them. I think Helidrect sale them...right?

VL I really hope you do this Mod. With your experience, knowledge and input plus with the help of the other guys here we could make this the best flying fixed pitch helicopter ever…seriously ever!

Thanks for thinking my build thread is sticky material, but with Bugster gone I doubt it will happen.

[JettaManDan]

Valuehobby is a teriffic company bud..i get all my batteries from there now pretty much...close to a Chineese price but super fast and reasonable shipping in the U.S...and they have answered the phone when i have called i recommend them for sure...

Dan

[FLThreeFiveZero]

Originally Posted by HELIHANKSTER

Dude You have a couple of Gaui 255’s…sweetness! What size is the main shaft on those puppies? The great thing about this mod is you can always switch it back to a cp helicopter fairly easy and quick when you want to.

I was checking out the web site you give me for the servos/batteries and I saw they have the identical 250 kit as the HK-T250 Kit for the same price and they are in the U.S. Sweet!
http://www.valuehobby.com/product_de...46&item_id=297
I was so happy with this build that I was going to order another HK-T250 bare bone Kit to convert another one of my Bees, but HobbyKing was out of stock, so I was kind of bummed…but now I’m Happy. Have you place an order with ValueHobby before? Are they a good company to do business with?

Sorry, My bad, I musta been thinking Rex 250 when I typed that. I actually have a couple Gaui 200's. one belt and one shaft tail. Both on the bottom Left.

But to answer your question the main shaft is 3mm x 84 mm..... isnt that like the V2 shaft.


I have ordered from Value Hobby.....alot.......they are great!

[FLThreeFiveZero]

Originally Posted by Viet-Lama

FL check out the torque on that servo, it only has .35kg at 6v and thats nothing. Now drop to 5v and you wont be able to steer.
Turnigy makes an 8gram servo (its black) with enough speed and torque to run great on both my 450s. Before I got my Logictech setup I ran it on the 250 and its not too big at all for the 250s small size. Only cost like $5 each, If your interested let me know and ill look up the link.



Yep , if your gyro has a "delay" then you use it to compensate for the slower servo and eliminate tail wag.

Your right....I musta missed that. The MG servo has 1.6kg thats not so bad.( like 20oz/in) Im just trying not to spend a mint on this Freestyle FP.

Yeah gimme that link for that Turnigy servo. I like to see all my options befoer I pull the trigger.