kahloq

I actually said that at the field after the flight was over. yeah....going to look at esc manual and see about doing something about the lvc point. ive disabled the lvc in some other planes before.

invertmast

My Feedback: (23)

My 335 project will be based on Don Smith plans (98" wingspan). The fuselage will be molded fiberglass, and i will probably design a gear reduction/drive shaft system for the rear engine to spin a scale size and shape (Solo) prop using a Dle-55, with a 85-90cc something or another up front (unless i can get my hands on a kohlm inlines 100cc fourstroke)
Dont hold your breath though, ive got a 1/4 GeeBee R2 and a F-14 prototype to do first, and possibly a Saab Draken

invertmast

My Feedback: (23)

I did the same on the horten after the last crash. If i had the lvc's turned off, i could of finished the turn and landed with minimal damage... We live, we learn!

kahloq

So....there's no setting in the programming for the castle ice hv2 160 that just shuts off the lvc. Is there any issue with setting the lipo count to 10s to force a cutoff voltage of 33 volts instead of using auto-detect? Currently, on auto it sees 12s so the lvc would be 39.6 volts. After landing yesterday, voltage read 3.79 per cell, which is 44.5 volts....basically storage charge, not depleted.

Im concerned that if I put it at 10s, the esc will act funny during flight thinking its encountering an over-current situation since the real voltage is 12s. The other setting I can change is turning off the over-current protection, but is that safe?

Also, default cutoff is hard cutoff. Definitely need to change that to soft cutoff so it only reduces power, not just shut off the motor. That alone though wont be enough to allow full use of the batteries, but at least wouldn't shut the power completely off at a very bad time.

Anyone with any insight here?

jrtal

I reckon that lvc occurred because you were at full throttle all the time, heating batteries with continuous high current draw.
Higher C rating batteries will hold their voltage better. Like edf guys use.
Of course a bit of judicious throttle management would help alleviate this to a large degree.

Going on the vid of your landing, the speed was fairly low, so throttle should be ok at lower level ( than full ) for cruising around.
I betcha the next flight will be A-ok.

kahloq

First flight was basically full throttle as I had no idea yet how slow it would fly. Being as heavy as it is, I erred on the side of keeping speed up till I could see how she'd react.
Once on the ground and in the pits, the batteries were not at all warm, so I don't think they were being overly stressed.

wphilb

My Feedback: (10)

Ask the Castle Creations guys, I've found them helpful in the past.

jimkron

Great job on the LVC challenge. I've lost two big planes to LVC.
Running the lipos at next to full throttle is definitely a problem. Generally, 15 seconds of full throttle is recommended, then backing off to 3/4 or 1/2 for a short period of time.
You should call Castle. I would love to know their opinion on what happened.
Again, Congrats on the maiden!

Jim

invertmast

My Feedback: (23)

Get the castle link, you can turn the lvc off with that. You can also change the cutoff style.

kahloq

I do think getting the castle link is a good idea, however, in the mean time, I just finished reprogramming the esc. I took it off auto-lipo detect and set it to 30v cutoff(equivalent to 10s as far as the manual is concerned). This should prevent the lvc from happening at least for a good while longer.
Since I got 4.5 mins before LVC happened on default esc settings, but only used around 4700mah...thats about 1000mah per minute. So I should be able to go to 6 mins and use 6500mah or so which is 80%. That would all be on full throttle. Now....reducing throttle some during the flight I may be able to stretch it to 8 mins if I pull back to half, however, at that throttle setting, id probably want to have some flaps engaged...so maybe 2/3 throttle for cruising and count on landing no later then 7 provided I don't do a whole lot of high throttle, low passes.

I also changed the cutoff to soft cut so i'll still have power even hitting lvc, but reduced. Additionally, I changed the throttle from auto calibrate to fixed and disabled the brake. With the auto calibrate, I haven't noticed any real change from 3/4 throttle to full on my D9 which also has the 65cc rimfire and CC HV2 Ice 160.

We shall see what difference it makes this coming weekend hopefully. I mentioned this before, but I went ahead and ordered two more 6s 8000's from HK. This will allow me to do a couple flights and if anything needs to be changed, I can retest the same day.

I am not sold on trying a different prop up front yet. I will do one thing at a time....test the changes in the ESC and if still I cant get 6-7 mins, then Ill invest in a lower pitch prop. So....seeing as I will try to test flight time next go around, I'll keep the plane rather high up after 4 mins. However, being high up, if I do hit lvc and it just reduces the power, I may not be able to tell right away.

Ameisenbar

I know you probably don't want to add more weight...but have you considered telemetry to let you know the in flight battery voltage from on the ground? How easy it is depends on the radio gear you have of course. We used it to good effect with an IC model to help find the best prop, one guy flying the model and the other peering over his shoulder at the TX to check the rpm readings. (You don't want to be taking your eye off the model to read it yourself!)

John

kahloq

That's not something I had thought of. But, as I have no spare channels open nor an rx that runs telemetry, I would have to invest in a completely separate system. While the idea is nice, Im not really wanting to add more complexity. The ESC has a data logger on it already, but trying to access that is next to impossible due to where the esc is located and would have to take off the spinner/prop/motor as well as the forward cowl to get to it.

jimkron

I have a DX 8 with telemetry that works great on my "simpler" airplanes and HexaCopter. If you ever change transmitter boxes in the future you'll want to add voltage telemetry, especially since you fly so many electric planes. You can set warnings on the transmitter so you never come close to LVC.

I have my DO 335 set for 8 minutes with gear down ready for landing around 7 minutes. I use the :15 seconds of hard flying followed by :30 of 3/4 flying rule.
5000mah Hyperions Lipos are never hot after landing.

Curious, are your props spinning in the same direction? We preferred counter rotating.

jim

BubbasanJohn

Jimkron, Im in San Rafael.  Where do you fly?

jimkron

Healdsburg, Wine Country Flyers.

kahloq

I have the JR 9 channel 2.4 radio. It is the version without the sim card so only 30 model memory. While I would love to have the newer JR11x cylon looking radio, I cant see spending that much for the radio. There's a few models I can offload from my JR 9ch to a different radio to make room since they are simpler 4-7 channels setups....so I bought one of those Turnigy 9XR's with JR module that has 16 model memory. Still though...no telemetry.

Anyway...ive since reprogrammed the ESC and hopefully I'll get a good deal more flight time since I know the batts weren't depleted.

As for the props. They are not spinning in the same direction. The front is currently a 20x14 normal rotation and the rear is a 16x10 counter rotating. I love the sound this thing makes in the air so I really don't want to change the props, but, I could try out a 2 blade turnigy 21x13 up front if I borrowed the spinner off my D9 or a 20x12.

The rear motor doesn't seem to be using much in the way of mah from the battery its powered by. On the charger, it only put back in 1100mah out of 5000. This really isn't a bad thing though. Definitely don't have to worry about LVC on the rear motor.
Id imagine most of the work is being done by the front motor and the "little" rear motor doesn't have much to do since the air is already accelerated windmilling the rear prop to the point that the back motor doesn't have to work very hard at all....this is just a guess.

I could throw an apc 15.75x13 3 blade prop back there, but it wouldn't be counter-rotating. On its own, a power 60 would blow up trying to spin that APC prop. I don't think it would make any difference in how the plane flies anyway, so no need to mess with it. I also have an apc 16x14 2 blade gas prop. I could put that on it, but then Id need new spinner.
I like the way the plane looks now with the 3 bladers and how it sounds....so Im not keen on investing in more spinners.
It would be cheaper if I really needed to get the amps down on the front motor to pay the $84 for a 20x12 3 blade Mejlik or $77 for a Biela 20x12 3bl

kwik

Well done Kahlog , congratulations!

One thing to consider is; If you increase the load on the aft engine, the load on the front engine will go down.

In order to keep the same speed, that is.

This means that the flying time will go up.

kahloq

I think really, the only way to increase the load on the rear motor, is to use a bigger prop. However, doing this requires the effect previously mentioned from the first motor. I could put say a 20x10 on the back, but if the front motor hits LVC and the rear motor is trying to spin that thing all on its own WITHOUT the benefit of the front's windmill effect, then the rear motor will blow up trying to turn a 20x10. So its a catch 22 of sorts.

On the other hand, as you said, increase load on the rear motor to help offset the work the front is doing. It might make a difference....maybe 30 secs worth.
Here lies another problem. I know of no counter-rotating 3 blade prop bigger then 16x10. That was part of the reason to go with the power 60 to begin with since I know it spins it fine.
But, its an interesting concept. Put a much bigger prop on the back knowing the front motor's air flow will help spin it. Will it still do that if its not CCW rotation?

I think I'd want to test fly the plane again before trying that experiment to make sure that the same result(low mah usage at the back) is confirmed.
I have power 60's on my esm me-110 turning 16x10x3's. On 6s 6000 per motor, I get 6 mins flight time and put back in 5000. Last thing I want is a big ol magic smoke trail coming out the rear of the DO-335...ie burnt up motor or burnt up esc.

BubbasanJohn

Congrats on the maiden Kahlog!!  Nice save.  Kinda like getting a free airplane.   Never once did I doubt that you would save her.  Looks to be quite a nice flying plane. 

jimkron

I agree to fly the plane again. Time to experiment with some of these concepts. Sounds like you still need to fly the plane a little slower if possible. That could help a lot with whatever caused the lipos to sag and hit LVC. Remember though, running those lipos to LVC levels is a really bad idea. You don't want over-stressed batts flying your nice investment.

Idea #1: I might consider a Eflite 110 on the back. Cost is $130 plus an extra 4.5 ounces of weight. That would give you a bigger prop on the rear and give you more push. Take some of the pressure off the front motor perhaps. You'll need to move some lipos around because of the bigger motor on the rear will affect balance.

Idea #2: I fly mine with two 160s and it flies great. Not to beat a dead horse but I put all my lipos (20s) in front of the cockpit and that was with a 160 on the rear. Balance was easy, weight was 35 lbs. I do love the 3-bladed props but I sacrificed looks for performance and I'm very pleased. This will cost extra money but you seemed committed to electric power. In the coming years I'm sure you'll find use for the 65 Rimfire and the Eflite 60.

This is all easy for me to say. Just some food for thought.

Best,

Jim

vertical grimmace

My Feedback: (1)

I think the key is to optimize the performance of both motors. It is not that the prop wash or aerodynamic effects will help your front motor, it is that the rear motor is performing optimally and taking away some of the work load of the front motor. Hence, reducing amp draw and increasing flight time.
If it were me, I would lose the 3 bladers and just go for performance, but I know that will not happen.

If I ever get a hold of one of these, prop selection will be easy. I know the best props for the engines I would use, and All I would have to do is put in more gas to get 20 min flights. Doesn't take but a couple of minuted to fuel up and fly again. But I know how committed you are to these electrics. Honestly this all seems crazy to me, for just a few minutes of flight time.

jimkron

For me, it's not like I love electrics...I just hate mufflers and cylinders sticking out on scale warbirds. I love fully scaled cockpits, weathering, scale landing gear, accurate paint colors, etc. As lipos and e-motors have advanced I've converted all my planes. But I hear ya VG, it's crazy what we do sometimes in this hobby.

vertical grimmace

My Feedback: (1)

The thing I do not like about electrics are the batteries. Kahloq could not fly again last weekend because he could not charge another set of packs. Even so, it would take around an hour.
I guess it is what bothers you more, seeing cylinders and mufflers, or being able to fly. Not having one of these (DO 335), I do not know how hard it would be to hide the engines, but keep in mind, this is an ARF, So "scale" has been compromised from the outset. Ooops, that is another can of worms though! lol

invertmast

My Feedback: (23)

You can fly an electric multiple times in one day AND get charge times under an hour, it just takes money!

My charging setup is

FMA power lab 8 ($230)
Ec5 parallel charging board ($30)
24v 1400w power supply ($180)
2000w generator ($300)

That setup will charge 13xx watts, Ie, four 6s 5000mah lipos (putting 3600-4000mah back in) in 30 minutes.

On a 12v power source (3-550 cold crank amp car batteries, plugged into a harbor freight 150w solar cell all week) with do the exact same batteries and recharge capacity in 1hr 10minutes. The charger is limited to 500-550w on 12v.

So while it is possible, it costs money and the hassle of carrying a generator (if you dont have power available at your flying field).


With the 335, theres really no way to hide the cylinder head and muffler with conventional IC motors, even the 1/5 scale models have the cylinder heada hanging out.

vertical grimmace

My Feedback: (1)

While possible, I do not find it practical, or even comfortable for that matter.

It seems that from the point of takeoff, you have to already be thinking about landing. Certainly a scary proposition if you want to fly a model like this at an event like the Warbirds over the rockies.

I think I can live with cylinders and mufflers. I bet cans would hide pretty well anyway, then all that would be seen is a head sticking out.