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Jan 27, 2008, 12:12 AM
www.insideheli.com
Discussion

My Backyard Heli Project - Franken Compy


Well, it's done. My backyard 300 class heli is up and flying. Before I go into the details, let me explain what prompted me to do this.

-- I do not like stocking a hobby shop in my garage to support my helis. So if I can get my helis all using the same main shafts, heads, main gears, etc, I am a lot happier. So I like my helis running Trex Rotor Heads and Tails as the parts are just about everywhere.

-- I do not care for 3mm main shaft helis. I find them too weak. This is a personal preference.

-- I started out modding and HBKv2. I modded it till its ultimate demise. I finally got to a point that the heli just could not become what I wanted it to be.


So with that, I started looking for a suitable platform to build on. I choose the Compy Fiber Frame. In its stock form, there really appeared to be very little modding needed to get it to where I wanted. It was also lightweight and compact, so it looked like a good choice.

Things that did not need changed

-- Motor Mount.
-- Servo Mounts.
-- Tail and Tail boom (already 12mm)
-- Landing Gear

Mods and Descriptions

-- Bearing Mounts. The Compy Frame is setup for 3mm main shafts. There was not enough plastic there to drill it out for a 5mm main shaft and bearings. The MX400's bearing blocks were used here ( http://grandrc.com/inc/sdetail/12420 ). They were cheap and looked like they would be a direct fit. When I got them, they were 16mm wide. The inside dimension of the Compy Frame is 17mm. So I needed to shim them a bit. To do this, I cut and CA'ed small strips of plastic from a "clamshell" package. You know, those things that just about EVERYTHING comes packed in these days and takes a steel toothed beaver to open. The screw holes lined up perfectly with holes already in the Compy Frame. One set of holes are the ones used to hold the front servo, so these screws serve two purposes, holding the bearing mount and front servo.

-- Idler pulleys. The stock mount for these only needed to be cut down and 2 new holes drilled to mount it.

-- Anti-Rotation Bracket. The Compy Bracket would not work. Its too small and in the wrong location. I ended up fabbing one up out of a bit of G10 and nylon. The MX400 Anti-Rotation bracket ( http://grandrc.com/inc/sdetail/12422 ) could have probably been used here with very little modiication. I didnít have on and was not going place an order for this. I intend on getting one in my next order.

-- 150T Main Gear and Belt Pulley. For the main gear I used a RCT 150T gear as I had them on hand. The belt pulley is a 40T from the HDX300, again, had it on hand. To attach them to the main shaft, I purchased the following http://www.cnchelicopter.com/servlet...-3dx400/Detail . I was hoping to use the 50T pulley as well, but the hub held the pulley down to far and therefore it was not inline with the idlers and the tail boom. So I only used the sleeve from that kit. Both the main gear and pulley mount to this sleeve and then the sleeve mounts on the main shaft with 2 grub screws. Pretty good design and allows you to move the gear and pulley up and down to get proper alignment. It worked out really well and needed no washers or shims to get the pulley lined up with the idlers and tail boom.

-- Micro Heli Canopy mounts were added as well. The plastic Trex ones could be used here as well, but I had the MicroHeli ones on hand.

Thatís really it. These are the only mods needed to set the frame up for a 5mm Main Shaft and 150T main gear. It went together surprising very easy with almost no complications.

In its current form it is running 250mm Blades. This can easily be changed by simply getting the right length belt and cutting a boom to the right size. For example, if I wanted to run 290mm blades, then all I would need is a stock Trex belt and a stock Trex Boom cut to length. Install and you are ready to rock and roll. This is something I was really striving for with this project. I can see this setup easily running blades up to an beyond 325mm quite easily.

What really has me excited is the weight. The AUW minus the battery is 395 grams. This is a little heavy for a 300 class heli. It could easily be lighted up though by choosing lightweight components. For this build I just used what I had on hand. But that is not the point. Let's say we wanted to stretch this out to a CNC 450 Class heli. The CNC head and tail would add around 30g if I remember correctly? Longer Blades would add 20g. Longer tail boom and belt 10g max. Bigger Canopy another 10g. You would need a bigger motor for another 30g or so. So now we are sitting at 495g AUW minus the battery. Put a 180g 2200mah battery on it and you are looking at 675g AUW ready to fly. This is 100g lighter then the average Trex 450. Again, with some care in selecting your components, you could most likely get this closer to 650g. That is VERY appealing to me.

I am most likely going to leave this in its current form as the new MSH Bird is on my list for my next heli.. I have done some hovering flights in the basement ( it hasn't been over 25F here in the last week ) and it flies pretty well. It will be a great backyard cruiser. With some good collective management and 2800 or so RPM head speed, I see no reason it won't loop/flip/roll. Later I intend on getting another Compy Frame and building it up to swing 315/325mm blades.

Current Components
- Esky 25A ESC
- HDX 300 BL Motor
- Esky HH Gyro
- Esky Servos (swash)
- BlueBird 308BB (tail)
- RCT 150T main Gear
- HDX300 40t Belt Pulley
- Phantom/Trex Plastic Head with Alum Main Rotor Block
- Trex Plastic Tail
- Modded Compy Fiber Frame
- AR6100 RX

And now some pictures for your viewing pleasure.

SPaRX
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Jan 27, 2008, 12:23 AM
The Rave.
BRAVO!!! I'm working on a 280mm bladed Compy myself. BRAVO!
Jan 27, 2008, 12:28 AM
www.insideheli.com
Thanks MicroHeli-Nut. If I can offer any assistance, feel free to ask or PM me. I will give you this advise though, MX400 frame parts work very well for this. I am even considering dropping the Compys Tail Boom block and putting MX400 boom clamps on it. The Compy block just doesnt tighten up to my liking. Basically a mix and match of Compy Frame parts and MX400 frame parts seem to work very well together.

SPaRX
Jan 27, 2008, 12:31 AM
Suspended Account
Sweet.
Jan 27, 2008, 01:54 AM
that's gonna leave a scar
WHEW...man, that is a hardcore setup !!!

looks like a killer
Jan 27, 2008, 08:35 AM
Registered User

Great Work!


Hi Sparx, congratulations on a great mod. I have been flying the stock Compy300 - didn't like the "CP2"-type head and bought the Walkera CNC head but experienced the same problem as the HDX300 - the 3mm shaft is just too weak. On spining up, the 3mm shaft just bend unless the rotor head is balanced perfectly.

My Compy300 fiber frame is on the way to me from HK and I am really interested to do the mod you did. Just a question - any problem about weight from the 5mm shaft and the TREX Rotor Head? I intend to keep to the 250mm blade because I needed a 300-size ship for my yard

If you have othe information to share on the mod, will really appreciate it. Thank you.
Jan 27, 2008, 09:24 AM
Registered User
JustPlaneChris's Avatar
Way to go, SPaRX! The idea of a sub-700g 325mm heli is very appealing. Considering the performance of my 790g Dragonus, I can only imagine how ballistic it would be 100g lighter.

I look forward to more exciting stories from the Franken Compy series.

-Chris
Jan 27, 2008, 10:15 AM
www.insideheli.com
Quote:
Originally Posted by NoseOut
Hi Sparx, congratulations on a great mod. I have been flying the stock Compy300 - didn't like the "CP2"-type head and bought the Walkera CNC head but experienced the same problem as the HDX300 - the 3mm shaft is just too weak. On spining up, the 3mm shaft just bend unless the rotor head is balanced perfectly.
This is exactly why I wanted to stay away from the 3mm Main shaft setup.

Quote:
My Compy300 fiber frame is on the way to me from HK and I am really interested to do the mod you did. Just a question - any problem about weight from the 5mm shaft and the TREX Rotor Head? I intend to keep to the 250mm blade because I needed a 300-size ship for my yard
It is a little heavier. It all depends on what kind of flying you intend to do in your backyard. I you intend on staying skids down at all times, then you should have no issues. Now if you intend on going skids up for extended periods of time, can't comment on that yet because I haven't gotta a chance to try it yet. My skill level current allows me to only do loops/flips/rolls. I am not confortable enough to do inverted hovers/flight. Also it has been too cold here for any outside flying so my testing has been hovering flights, extremely quick/short pitch punches and slow circuits in my basement. From what I am seeing, loops/rolls/flips should be no problem if you are good at collective management. Changing to 290mm blades would be a BIG improvement though. In your case, I hardly think you would notice the increase in blade size. We are only talking ~3 inches increase in the rotor disc and ~1.5 inches to the lenght. But the increase in performance would be Dramatic to say the least


Quote:
If you have othe information to share on the mod, will really appreciate it. Thank you.
Pretty much everything I did is explained here. If you have any specific questions, feel free to ask. I do not think I missed anything I did in this mod

SPaRX
Jan 27, 2008, 10:17 AM
www.insideheli.com
Quote:
Originally Posted by JustPlaneChris
Way to go, SPaRX! The idea of a sub-700g 325mm heli is very appealing. Considering the performance of my 790g Dragonus, I can only imagine how ballistic it would be 100g lighter.

I look forward to more exciting stories from the Franken Compy series.

-Chris
Yeah me too JPC. But I am gonna put it on hold for a bit right now I think. I wanna save my "toy money" for the MSH when it comes out. And who knows, by then I might have a better idea for a lightweight ballistic 325mm heli. I have my 450 weighing in at less then 730grams right now and swinging 335mm blades, so I am pretty content at the moment

SPaRX
Jan 27, 2008, 10:27 AM
www.insideheli.com
Noseout,

To add to the weight comments. There are a few things with my current setup I could do to cut some weight.

First off I forgot to mention that I am running a UBEC as well. You can see it in the pictures. This is 10grams. So if you do not run one then knock that off the AUW.

My ESC is kinda heavy as well. You could probably lose another 10grams there.

I am using 8gram servos. Swap them out with some 6 gram servos and you lose another 6 grams there. Shorten the wires and you could stretch it to 10 grams.

The HDX300 motor is 35grams. I have seen some 25gram motors out there that would more then do the job such as..... http://www.cnchelicopter.com/servlet...icopter/Detail . So you would lose another 10 grams there.

So with those simple changes you would drop 40 grams right off.

Then it just depends on how much you wanna do from there. The Trex Main shafts are solid steel and weigh 17.5 grams. There are main shafts that are hollow such as an Esky Main shaft. Trim it down to the Trex lenght and it will weight around 11 grams. So there is another 6grams. Or order some 5mm steel tubing and make your own.

There are probably more ways to trim weight I havent even found yet

SPaRX
Jan 28, 2008, 06:52 AM
Registered User

ESKY K2 main gear & belt pulley?


Hey Sparx, thanks man

I went to the LHS today to check out the King2 hollow main shaft and have a question for you.

Have you consider using the K2 main gear and the K2 belt pulley? Do you think there will be an issue with tail authority as I am not sure the resulting main-to-tail ratio.

I am thinking of setting up the Compy300 frame with the K2 hollow main shaft, main gear and the belt pulley .

I recently upgraded my Mini-T complete rotor head to CNC so I have the stock plastic Mini-T rotor head available. Thinking of using this rotor head.

This will give a CompyK2mT heli What do you think?
Jan 28, 2008, 11:37 AM
Heli Humbled Daily
Problem with king2 anything is that most LHS don't stock it.

I agree with using 150T main gear. Align stuff is everywhere, and better quality (cheaper) than E-sky.

Good job Sparx!
Jan 28, 2008, 11:39 AM
www.insideheli.com
HBKv2 belt pulley is only 32T. Also how it mounts will not work well in this application unless you drill a new hole for the retaining pin. You best bet is getting the HDX300 40T pulley and that 50T pulley and sleeve I linked above. HBK Pulley will give you a 3.2:1 ratio, the 40T will give you a 3.6:1 ratio. So it is a little better.

The HBK Main gear will work stock with that sleeve, so no modding needed there.

The HBK main shaft might need a little trimming to work. It is quite a bit longer. But by using that sleeve, you may not need to cut it. The sleeve attaches with grub screws as opposed to bolting through the main shaft.

I see no reason the Min-t Head will not work.

SPaRX
Jan 28, 2008, 11:42 AM
Heli Humbled Daily
Technically, you didn't need the larger sleeve at all. Couldn't you just drill the HDX300 pulley to 5 mm and mount it right to the shaft?

I like the longer sleeve, though. It saves the shaft from getting chewed up.
Jan 28, 2008, 11:44 AM
www.insideheli.com
Telemachus,

Nosein is in Sinapore, so HBK stuff is probably availble locally. Unlike here in the States.

Nice thing about this CompyFrame is you can tailor it to your desired specs easily.

SPaRX


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