2015 Project #2 - "Super" Trex 500

[danhampson]

I think the training gear was just a precaution in case the tail didn't hold. stock blades on the protos are 425mm with the msh stretch kit on it swings 470mm (awesome), the extra 80mm per blade must generate a hell of a lot more torque.

[Derek]

I'm guessing you have seen this video then Derek?
Insane power.

https://www.youtube.com/watch?v=orHiutfmUTQ

Yep..I've seen this video. This guy did an awesome job on his beast! What a sound it makes!!!

[Derek]

Great project Derek be following you on this,

Derek as your prob aware with concerns of the tail weight balancing the added weight at the front, the added size of the bigger 550 tail case and moving it further away from the pivot point I think will make it to tail heavy, the 500 case further away on the stretched boom might be enough in the first place, what is the weight diff going from 1 6s 2700 to the 2 4s xxxx cells that your planning on using,

I think the 550 tail will be to much mate,

hmmm, I have 6S 3000mah packs for my 500 right now. I've been flying the 3000's for a long time. I'll have to check on the weight difference between the 6S 3000 and a pair of 4S packs. I haven't decided on the MAH yet. I'm not real sure what will fit under the canopy.

[Derek]

That is bonkers.

Derek have you thought about buying some carbon tube and rod to make the boom and TT you could strip the hardware off an original TT for the carbon rod that way you may not need to mod a 550/600 boom case.

Ive seen msh protos stretched to 550 using carbon tube and a longer belt, There where no other mods other that the stretched tail gear to speed up the tail rpm.

Yes, I have thought about buying a carbon tube and rod to make the boom and TT. I might still go that route. Initially, I wanted a belt drive tail. My current 500 has a belt drive tail but I have no idea how long a stretched tail belt would be.

[Derek]

I use to put training gear on anytime I made a major change in set up, new parts etc. Saved my heli a number of times when something unexpected failed.

Training gear have saved me quite a bit of money as well.

[murankar]

I have seen this video a while ago and that's just insane. 12s on custom 500, talk about pushing an airframe. I wounder how much he gained from the build? 8s should be plenty for a 500 but you will have a clearance issue under the canopy I would think.

[pvolcko]

CoG is likely going to be an issue. You'll probably want to get the battery and ESC as far forward as you can manage.

Tail ratio... I've never screwed around with the tail ratio on a heli, have always used stock. From what I gather there are a few things to consider. First, you need to figure out what headspeed range you want to run and what pinion/main gear you will run to achieve it. That will determine what tail ratio you want to run.

8S is unusual. What are you thinking you'll be doing with this in terms of headspeed? Underspeed a typical 12S type setup and go for way low headspeed (I've seen Kyle Stacy do some amazing smooth 3D running 6S on a 12S setup) or go for a screaming oversped 6S setup (speed heli! yeah!). IF you're going to overspeed a typical 6S 500/550 type setup then you'd want to go with the slower tail ratio. If you're going to go for slow headspeed then you may want to go with the faster tail ratio to give you as much tail authority as you can get.

Or are you going to tyr to fine the right combo of part to make the headspeed be normal for a 550 size heli? In which case you can run whatever ratio gets you as close as you can to a typical 550's tail rotor speed (favoring under if you have to choose over or under, given your sport/beginner-3D flying style).

[Derek]

You've given me a bunch to think about, Paul...as expected, lol. Thanks for that!

I was doing some thinking about this helicopter, at work last night. I think I'm going to have to change a few things. Initially, I wanted to invert the motor and have it mounted on top. The more I got thinking about that, I'm not sure that I can do that because the servos and main bearing blocks would be in the way. I think I was just fantasizing about "something different". So, let's move on from that.

In fact, I think I just want to simplify things. Instead of 8S, I may just stay with 6S but I want to run an improved motor that will handle the 500mm blades and the beefed up tail. As for the head speed, I think I'm looking for around 2400-2800.

I never really considered a "speed" heli....but you've got me wondering....since I have the DX8, with the 3 position flight mode switch...can I "have my cake and eat it too"? Can I have the normal mode for getting the helicopter off the ground (in regard to throttle curve, pitch curve, and gyro settings) and then have position 2 more for my "sport/beginner 3D flying style" (as you mentioned, lol, and then have position 3 set more for speed runs? How much fun would that be? Or, am I dreaming?

I still haven't discarded the thought of an 8S setup. It's just that a 6S setup would simplify things because I already have my 6S packs. I don't have anything that runs 4S packs....yet, lol.

I can't remember which motor I had picked out. I've got it written down on some paper....somewhere. The wife did a bit of cleaning yesterday, so naturally I can't find anything, lol. She's so good to me though, lol. I did find a motor that was good to 8S and a CC 100amp esc was suitable. Damn...where's that paper!!!

[murankar]

With speed you not only need the head speed but the pitch as well. Typically you are going to run with high head speed with moderate collective pitch. Your tail gains are going to be super low, almost rate mode; in fact some pilots run in rate mode. Next is going to be the power system, most speed helis run a super beefy power system because of the amp draw due to the collective pitch and the speed of the head. On a 700 class heli your head speed is over 2500, so on a 500 your head speed maybe closer to 3K.

All that said that's for a dedicated speed machine. A trainer speed heli will not need all of that because the big thing with training is working on stall turns/half Cuban 8's, transitioning from vertical to horizontal and getting your flight line right at the correct altitude. If you never flown speed I would sit down on the sim and try it with any machine. I did and let me tell ya its tougher than it looks. Even with the Diablo setup I still had a hard time getting to right. I was making my passes all over the place but then again I am not very skilled at this point.

So if you think you might want to try speed you may want a versatile electrical system, one that can do both 6 and 8S.

I forgot one thing, your gear ratios for the tail might be different just because your running higher head speeds. You may not want to run a super fast tail. If you do have a super fast tail then may end up with to much mechanical advantage which in turn effects your tail gains.


P.S. Just to get idea of whats going on listen to the goblin speed review by Justin Pucci on RCHN. It should help clear up some of the question marks you may have or create more.

[Derek]

Thanks Matthias! I've done some speed runs with my 600, a few times. What a rush!!! Stall turns and half Cuban 8's were pretty good.

I still can't find that paper that I had two motors written down on. Both were good for 6-8S setups. I asked my wife about the paper. She said that she threw some stuff away yesterday but doesn't think she threw any of my papers away. Hmmmm...I may just have to go back through all the motors again. I was looking at Scorpion, KDE, and Quantum. I'll see if I can find it this weekend. I have to leave for work soon.

[cml001]

Don't like trailing balls!

[Derek]

Don't like trailing balls!

what do you mean, "trailing balls"?

[cml001]

I crash with'm on. Lol

[Derek]

did you mean "training" balls?

[cml001]

Oh.. Sorry bout that.. Autocorrect isn't alway correct.

[Derek]

Oh.. Sorry bout that.. Autocorrect isn't alway correct.

ha ha ha...for sure

[Derek]

Question Time, lol...

For an 8S lipo setup, I've been eyeballing the Scorpion HKIII-4025-890. However, this motor has a 6mm motor shaft. My Align motor has a 5mm shaft, therefore my pinions have a 5mm hole. If I were to get this motor and then do some shopping around in the 550-600 class area and find a pinion with 6mm hole, would the teeth on the larger pinion match up to my Align main gears?

[pvolcko]

Not sure. I'd buy the pinion you want and test fit it. That or find out if you can get a 5mm shaft for the motor. Scorpion is pretty good about having alternate shaft lengths and diameters. Other option, find a friend with a lathe and have them turn down the business end of the 6mm shaft to 5mm.

[Derek]

ha ha ha, thanks for that, Paul! I was considering those same very options, lol.

1. buying the pinion with the 6mm hole and see how well it meshes. Pinions are rather inexpensive.
2. See if Scorpion has a 5mm replacement shaft.
3. My Dad has a very good lathe, turning down the "business end" of the 6mm shaft wouldn't be difficult at all.

[Derek]

Ok...it's been a while since I've talked about this one but it's still in the works. My mini quad project definitely took over my priorities, lol. With that done, I've started my Project #1 for 2015 and I'm making good progress. This helicopter project has entered the planning phase. Because I seriously want the motor to be on the top of the frame, and not inside the frame, I've decided to use the 500 Dominator frame and parts for the frame. I'm also hoping that I can use the built in battery tray to hold one 4S pack while the other 4S pack is mounted on the top/front. I imagine the Castle 130 ESC will be mounted on the side of one of the frame halves. I'm still gonna use a 550/600 tail. Everything from the tail boom case to the tail rotor will be 550/600 size parts. Obviously the tail boom, torque tube, and boom supports will all be custom cut...but that's just a part of this project. So be it.

As for the planning phase of this build, I got on Ebay and bought a Trex 500L Dominator manual and a Trex 550 Pro DFC manual. I can use these to gather a parts list and I can be certain that I'm not leaving anything out when I order parts. I won't be ordering parts anytime real soon but I am very much looking forward to getting started on this.

Electronics that I do have picked out include:

Scorpion HKIII-4020-1350 Brushless Motor. (I like this motor because it is 8S capable and it has a 5mm shaft.)
Castle Creations PHOENIX EDGE 130 AMP (32V 130 AMP) BRUSHLESS ESC. (This esc is more than capable of handling the 4020 motor)
Castle Creations 20amp BEC Pro
Ikon Flybarless Controller

I haven't totally decided on servos yet but I want something HV, capable of 7.4v

I plan on getting Zeal main blades and tail blades

I have a guy at a local tattoo shop that has agreed to do the custom paint on the canopy for me.