Kaos E-Konversion
 

I'm doing a conversion of the Tower Hobbies Kaos and these numbers look pretty promising. Perhaps too promising? Can anyone see if I am missing something? I attach a photo of the motor mount and a set of data.

Thanks!

RE: Kaos E-Konversion
 

Not sure what you're looking for but my quick impression is that the motor is not sufficiently loaded. ~650W is roughly the power of a piped 25 or a good running 32. Your motor is likely capable of a lot more especially if it's only developing some 20A of pull on 6s.

The Tower Kaos is nice on a good 46 which can produce 900-1100 W of power. I'd aim for a lighter smaller motor that can generate the power on an 11" prop on 5s. The model will be lighter yet but will have excellent thrust and vertical performance. With that said, your current setup will certainly fly it - just perhaps not optimally.

My nickel's worth.

David

RE: Kaos E-Konversion
 

Thanks, David. The online AMA review of the Kaos (great article) said that the 46 engine used was turning an 11x6 at 11,300. I am beating that number by a few hundred and well under the lower weight threshold. So I figure I'm ahead of the power curve. What do you think?

RE: Kaos E-Konversion
 

I guess my first thought is that the performance of the 46 mentioned is a tad less than stellar. Engines this size on classics can be brought in the 13.5-14K range or better if tuned well. Of course I'm viewing this from a "classic pattern" perspective rather than a sport plane view.

My second thought is that the view of getting any prop of a given geometry turning at a given rpm is not particularly useful. For one, not all props are equal. An APC 11x6 sport is a different beast than its thin electric counterpart. Put an APC sport on the motor and you'll find out how the motor is really comparing to the glow...

What I would do though is to pick up an APC electric 11x8.5 and an 11x10 and spool up your system. You'll now see your motor come to life! Keep it within the current draw specs which I bet are at least 40 if not 50A. Now you'll be pulling ~880W on 40A or ~1100W on 50A. Keep the motor in its efficiency band and your Kaos will be a different beast. Want to fly slower? That's what the throttle stick's for. [8D]

From there on flight duration can be sorted through current draw. At 40A your battery will give you roughly 4.5 min at full throttle or ~8-10 min with throttle management.

Hopefully someone who has done an e-conversion of the model will chime in as well.

David

RE: Kaos E-Konversion
 

You may be right about the electric vs piston propeller thing. Unfortunately my motor is redlines at 700W and I am too far down the road to change now. I am thinking I will fly the Kaos with this setup to get the feel of it and then maybe go back to the drawing board for Mark 2 with a hotter motor.

RE: Kaos E-Konversion
 

One more thing, David. Is my takeoff thrust greater than 1:1 not good enough for a 1970s pattern ship? Not to speak of my 125+ W/lb. I have no experience with this so I am just going by published wisdom.

RE: Kaos E-Konversion
 

On closer inspection of your motor picture, it appears to be more of a 32 sized motor - 4250 or so I imagine. What really surprises me is that it redlines at 700W if it can take 6s! That is quite unusual for outrunners. With a low KV it can be done evidently.

On these birds with trike gear, we are usually aiming at high rpm on smaller props compared to the typical electric wisdom. The idea is to use higher KV motors that will get a smaller prop up to speed and produce good power. An identical motor with a higher KV of say around 800 would have delivered the extra Watts one might be looking for and get it into the ~900W range. 150 W/lb or more is nice on a classic for excellent performance. So you'd be aiming for 750-800W at full throttle. Your setup will be similar to the performance of a typical early 80's 40 size engine like a K&B 40 rather than a modern 46.

That said, your model will fly just fine, it just won't be quite the performer that it could be. If you decide to retrofit another motor later for more performance, you might also want to consider mounting the motor with the typical X-mount to the firewall. This is generally a more solid solution on these power ratings and it will also keep the lines of the plane cleaner. The prop adapter mounts to the can of the motor rather than using the shaft off the back. Some simple 3/8" hardwood dowels or aluminum standoffs can put the motor at the desired distance from the FW.

Enjoy!

David

RE: Kaos E-Konversion
 

This motors could be a good choice for your plane , been there ..

http://www.hobbyking.com/hobbyking/s...ner_Motor.html


http://www.hobbyking.com/hobbyking/s...ner_Motor.html

Volts times amps equals watts.

Figure 150 per pound or so watts for normal flight....200 plus for crazy power flying.

Match your prop to the motor/KV and you are good. Its simple and works every time

RE: Kaos E-Konversion
 

Personally, I quite like the specs of the Great Planes Rimfire 46 for these 40 sized classics. 42-60-800 makes for a motor that requires short standoffs and the 800 KV means that one can get an 11" or even 10" prop up to rpm and produce ~900W of power on 5s at under 50A.

A 4000 mAh 5s pack gives 5 min at WOT or ~10 min managing that throttle.

David

RE: Kaos E-Konversion
 

In the interest of helping you with your conversion here are the specs on my Conquest IVe.

My plane is considerably larger than yours with a 65" wingspan (790 sq. inch) and an 65" length. However, comparisons can be made that might help you. My gut feeling is that you need a 5s setup at maybe +/-3500 mAh. A 6s pack would seem too big and heavy in my mind. Anyways, here is my set-up:


* Scorpion 4025-10 - What is critical here is the high KV of 515,the largest prop I canfit is 13"on the Conquest IV

* APC 13x10e prop - This prop provides the best power for this plane so far, I tried 12x10's and 12x12's but 13x10 is best (I only have about a 1/2" of prop clearance!)

* E-Flight 80 ESC - I am pulling about 68 amps max so this works fine, I am not using the BEC - Separate flight pack for safety

* Sky-Lipo 6s 5000 mAh 30c cont. motor battery - gives me 7.5 mins of flight time using +/- 80% of capacity

* Set up generates about 1600 watts which works well at 9 lbs - 10 oz rtf - I would be a little happier if I could be under 9 lbs.

* Everything comes down just lightly warm to the touch

I hope this helps you in some manner.

Doug <! messag>

RE: Kaos E-Konversion
 

Adjusted per YS measuring stick

RE: Kaos E-Konversion
 

Cody,

I'm not sure I understand your comment but turning an 11x6 at 13K+ rpm on a 45 is well doable. In fact, a well tuned, piped, plugged and fueled YS 45 FR can turn a 10x9 in excess of 15K. So yes, everyone did use those engines and some, speed and classic folks mostly, still do.

The YS 45 is the class benchmark in my opinion and can do better than a Rossi 45, Jett 50 and even approach the thrust of a 55 (Webra, OS). Compared to engines such as a stock muffled OS 46 AX, the YS is in a class of its own.

This e-conversion discussion was really about getting a little over a horsepower out of the setup as far as I'm concerned. The 1 bhp power output figure equates to a decent bushed 40 in my mind (e.g., K&B 40).

David

RE: Kaos E-Konversion
 

Thanks very much to all of you. I will PDF your advice and save it up for Mark 2!

A few comments:

1. David has me worried about the nose stability issue. I will cut into the cheek skin and reinforce it with hardwood or carbon.

2. The AMA review cautioned against using a prop larger than 11" on the Kaos because the gyro effect would cause tail wag on vertical lines. My goal is to replicate the stock piston performance, not necessarily to improve on it - on Mark 1 at least.

3. The Firepower 40 is the only motor I could find on the planet which combines a 42mm diameter with 700W rating and low Kv (about 625 from bench tests). Nothing bigger than 42mm will front-mount in the nose of the Kaos.

4. The whole nose-mount thing began when I saw Franny Brodigan's gorgeous conversion of the Bridi Vagabond, which can be found in the link below. I thought I had to go nose-mount to imitate this. Now Franny is obviously a greater craftswoman than many of us guys can aspire to. So for Mark 2 I may have to hack out the nose for an X-mount instead.

http://www.frannybrodigan.com/Vagabond.asp

RE: Kaos E-Konversion
 

A few comments inline below.

That was my concern too. There really isn't much stiffness up front as there is nothing holding the sides square below or above. Your new 1/4" firewall is somewhat floating up there. Fortunately e-power doesn't produce much vibration but it can generate significant torque.

10" and 11" props are perfect for the Tower Kaos particularly on trike gear. A typical 40-46 glow setup.

There are motors on the market with 42 mm cans that can produce 700W and more. The low Kv is what you are not looking for, at least not on classics. Low Kv is desired when one wants to turn big props with lower pitches. We can afford to lower the voltage slightly (i.e., 5s) at the expense of higher currents. The GP motor I mentioned has the sort of specs desired for 40 size classics.

That's a beautiful Vagabond. The scheme reminds me of a little Tiporare I built - very nice.

However I'm puzzled. Franny didn't mount the motor like you did. You have the motor flipped 180 degrees with the stator behind your new FW and are using a shaft prop adapter. Franny mounted it like I was suggesting above using the X-mount with standoffs against the existing FW. Her prop adapter is mounted to the rotating can. This is a pretty bullet proof setup.

It wouldn't take much to flip your motor, mount it to the real FW and remove the ply up front. Pick up some aluminum or hard plastic standoffs. The latter you can cut to size easily.

Basically this type of installation is akin to a glow engine installed on a radial pylon type mount.

David

RE: Kaos E-Konversion
 

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RE: Kaos E-Konversion
 

I was also guilty of more of a sport power mentality when thinking of electrics.

turbo

RE: Kaos E-Konversion
 

I am currently converting an old Tower Kaos arf (the purple/white one) for a practice/backup SPA plane. I chose a power setup to stay within the SPA rules. I chose the Emax GT4020 (headsuprc) and intend to use a 11x7 (either 5 or 6 cell). I am mounting my motor on the original firewall with standoffs (cut off the side cheeks). I prefer mounting this way because it gives you a little room to fine tune the cg (that and the battery space).

If/when I get it dialed in, if I like the setup I will clean it up a little (build a custom cowl, wing fairings, etc.).

Right now I am in the process of cutting a battery hatch. From what I can tell, its going to be a big hatch, but I would rather have it too big than too little.

p.s.- I agree with everything doxilia says.

p.p.s-Thanks for the Vagabond link. I have one, was going to give it away. Now I may have a new project. Beautiful plane.

RE: Kaos E-Konversion
 

David is right that the Vagabond used an X-mount and my setup does not. However, I figured I probably would get a sleeker look by front mounting when the nose ring/mount is fully faired in and cowled (yet to be done). I also needed some space in the nose bay for the Ice ESC with heat sink and my setup left the bay nicely un-cluttered. Let's see if it holds up without falling apart...

I wanted the low Kv so that I could use a high voltage/low current setup. Basically I had no idea how effective the cooling would be. Right now the battery is running ~ 10C and the ESC is at 60% even at WOT which means I should be pretty safe with minimal airflow. Of course, that's useless if the bird does not fly!

RE: Kaos E-Konversion
 

Fairing the nose in on an e-bird like was done on the Vagabond build is a nice thing to do and would improve the looks of the Kaos significantly. However, using a thick 1/4" ply former up front as shown in your picture, makes life harder. You now have to fair a 1/4" piece of square ply into a circular spinner sized diameter. Not something I'd want to do. If anything, you're better off cutting a 1/4" disk the size of the spinner and mounting the motor directly to it through the front. Like you have done but not on a rectangular piece of wood.

It is considerably easier if you use a piece of 1/4" or 3/8" rectangular balsa sandwiched in between the "cowl cheeks" up front. You align it so that the hole you'll make in it will be centered on the thrust line. You then take a piece of 1/16" ply and make a ring - probably 2" or 2-1/4" outer diameter for the Kaos as this is a good sized spinner on 40's. Carve out the inside of the balsa backing from the ring opening in the ply and you have your thrust washer (prop adapter) passing hole. Behind the balsa backing "former" you add 1/2" or 3/4" tristock in the corners going back to the original firewall. Add a sheet balsa bottom and you can then carve and sand the nose to contour fairing it in with the FW in the back and the nose ring in the front. The 1/16" ply ring makes the front stiff, provides a carving guide and the whole mess is much easier to shape and sand than producing a circle out of a rectangular piece of 1/4" ply.

I've attached a drawing showing the 1/4" balsa former and rings that I've made to produce the nose of a model I'm currently designing. The 1/16" ply ring with the smaller hole is to be used as a spacer. You mount it on your engine/motor, add the spinner backplate, lock it down and then you can see exactly where the motor X-mount (or engine mount) winds up. Measure the distance from the back of the X-mount to the firewall, cut standoffs that length (as the Vagabond builder did) and mount your X-mount by passing screws through the standoffs into blind nuts in the firewall. The former on the bottom is the e-firewall. One can see the offset mounting location for the motor (right and down thrust) as well as a hole centered on the motor behind it. This removes some weight and allows airflow. The hole to the left is to pass the motor leads to the ESC behind the FW. The hole on the bottom are the main cooling passages - plenty of air over the ESC and battery which is also cooled from above over the FW (not the case with a flat top design like the Kaos). The spinner rings are 1-3/4" diameter in this case but the concept can be used for any size model with a contoured nose.

You can often place the ESC on the standoffs under the motor, or, install it on the underside of a battery plate in the tank compartment. The ESC goes underneath and the battery on top accessible through a hatch. You can make holes in the plate to lighten it and you can also make at least two holes in the FW, one behind the X-mount to allow a driver access to the motor screws from behind and another to pass the leads into the tank bay if you position your ESC there. If you are running your ESC at 50% capacity or thereabouts, it will barely need cooling. You can add other holes in the FW making sure you don't weaken it in the X-mount standoff areas to allow more airflow over the battery behind it.

I understand that logic but in the case of classics where we want to turn smaller propellers at higher rpm, the opposite equation is preferable (while it may not be preferable electrically) - drop the voltage (5s or even 4s can be used) and up the capacity - the weight can be made equal to a 6s setup. Keep the Kv high and the prop will spool up to higher rpm with lower voltage. So long as you use a good ESC capable of the current draw of 40A - 50A and a little more (i.e., 60A ESC) and provide sufficient airflow, there is no issue.

Just some ideas for "Mark II". [8D]

David

RE: Kaos E-Konversion
 

Wow, that is great input. I will have to digest it and see what I can do.

I think I will cave in to the finger wagging about power and run a bit hotter. APC 11x5.5 = 740W @ 11,700 on the bench. That should get her off the ground or kill the motor.

RE: Kaos E-Konversion
 

A couple of Kaotic images:

Photo 1: The Ino-Lab 250 is a fabulous digital servo for $20, but it's so tiny I had to make a stepstool tray to line up the pushrods. Same pic also shows the remains of my failed attempt at a trailing-edge exit air duct. Clean-up time...

Photo 2: Realized too late that the battery hatch could easily have been made flush. Next time. But AK Models does great laser cutting for cheap.