Author Topic: Power Systems for T-Rex (Read 2259 times)

Walter Hicks · « **on:** February 11, 2010, 08:18:22 PM »

Does anyone else besides Bob Branch have an Electric T-Rex? If so what is your set up. I have new in my hands

RSM "turnkey " set up with Hacker motor, I also have several Turnigy motors. I am hoping Dennis Adamisin will

Chime in here regarding the Turnigy power systems. I have Sk 3548- 900, SK 3548-1100 and C 3548- 800.

I also have a Castle Creations 60 amp ESC with Huben Timer. If I understand this correctly I need at least a 4 cell

14.8 v 20 c, 4 cell 4000 + mah? Roger Anderson will be testing some of these soon also. I dont quite understand

when I would need a 5 cell. It apears that you can set one up about 63-65 oz ? The 5 cell is obviously going to

weigh more or maby not?

Alan Hahn · « **Reply #1 on:** February 11, 2010, 09:21:51 PM »

You need to carry a certain amount of battery weight. That is just a statement on the energy you need to complete a flight.

To first order, it is immaterial if you use a single cell or 10 cells, as long as the total capacity has enough energy for the total flight.

Consider the motor as a transformer. Depending on the number of winds (like the secondary of a transformer), a low voltage(few cells) -high amperage setup (a low number of winds which is equal to a high kV motor) will deliver the same power to the prop as a high voltage (many cells)-low amperage setup. The former case will have a small number of large cells, while the latter many smaller cells. Nominally the total weigh of both setups will be approximately the same.

Ok with that all said, we tend to have gravitated to speed controls (ESC's) which can handle about 35-50 amps and a maximum 6 lipo cells hooked up in series.

So if you look at Bob Branch's setup, then you can assume he is carrying enough energy to complete the pattern. That is the battery weight you need to carry.

Now another detail is that the kV of the motor and the voltage of the battery will set the rpm the prop will turn under load. I don't recall Bob's setup off the top of my head, but if you assume a nominal 3.5V/cell under load (near the end of the flight), and give yourself 20% overhead, then your motor kV times 3.5*#cells *0.8 should be close to the rpm the prop is turning.

So if you already have the motor, ad believe the rpm that Bob says he needs to fly a good pattern, then the # of cells you need is just

# cells=rpm/(kV*3.5V*.

so for an explicit example, if rpm=9000 rpm, and you have a 900 kV motor, then you need 9000/(900*3.5*.

=3.6 cells. Since they don't sell partial cells, round this up to 4.

To understand your capacity per cell, take Bob's # of cells, and multiply his capacity/cell, then divide by the number of cells for you (=4). So your cells will be bigger than Bob's, if he uses 5 cells in his pack.

I would always say to buy only a single pack to begin with, just to make sure it is all working out ok. If you already have a 4s pack for example, but it is a bit too small, then fly it for a 2 minute flight and do a few maneuvers. See how much you use and then scale that to what size you will eventually need. I have hooked up smaller 2100mAHr packs in series and parallel for first flights, just to get a handle on how much I will need for the final setup.

bob branch · « **Reply #2 on:** February 11, 2010, 10:56:33 PM »

Walter

Alan brings up one of the real advantages of electrics. The short flight to trim things out with. Not just airplane handling but especially the power system in early flights. The rpm you have to turn really as he says is what dictates the battery. Since I am running a low kv motor, the axi 2826/12 a 4 cell system while it flew the plane fine, did not have me getting the performance out of the governor I want. This I could feel in the flight performance, I could tell in how the motor sounded and the amount of rpm change in maneuvers, and then the ICE esc plot confirmed it. I was running too close to the capacity of the 4 cell packs I use to be where I wanted to be. I was running at 90% plus power on the ICE plot. Going to 5 cells let me have the rpm I wanted for the lap times I want, bring the power band of the governor back to about 80% so I am getting more power from the governor power increase in the maneuvers that I like, and the wieght of the 5 cell vs the larger 4 cell I would have to carry to do the same is about a wash. When I am done testing I anticipate being able to drop a battery size in the 5 cell config, but due to our lovely winter here in the Detroit area have not had a day to fly since our late fall ran out, so I cannot say I am there or that I have hard confirmed data.

So there really as Alan said is not one right answer. Do you want to fly high pitch or low pitch? You can fly high kv or lower kv. You can change the configuration around by varying the number of cells to create more rpms if you need them and if you go up in cells may well be able to carry a smaller mah pack. Lots of possible answers. I think there are a lot more questions to answer too. For instance, does a lower kv motor regulate downline speed on the governor better than a higher kv motor? That's one I am interested in and the electric strega with the really big motor is the test bed I want to evaluate it in, but it can be studied in any platform. Just a mater of having the time and putting together the test regime to evaluate it.

keep those greasy electrons wiped off the plane. They build up you know.

bob branch

Rudy Taube · « **Reply #3 on:** February 13, 2010, 02:33:47 AM »

Removed

Dennis Adamisin · « **Reply #4 on:** February 13, 2010, 07:24:37 AM »

Quote from: Walter Hicks on February 11, 2010, 08:18:22 PM

Does anyone else besides Bob Branch have an Electric T-Rex? If so what is your set up. I have new in my hands RSM "turnkey " set up with Hacker motor, I also have several Turnigy motors. I am hoping Dennis Adamisin will Chime in here regarding the Turnigy power systems. I have Sk 3548- 900, SK 3548-1100 and C 3548- 800. I also have a Castle Creations 60 amp ESC with Huben Timer. If I understand this correctly I need at least a 4 cell 14.8 v 20 c, 4 cell 4000 + mah? Roger Anderson will be testing some of these soon also. I dont quite understand when I would need a 5 cell. It apears that you can set one up about 63-65 oz ? The 5 cell is obviously going to weigh more or maby not?

Hi Walter
OK first the REALLY short answer. Brodak stocks an Arrowind 2832 motor (950 kv) 4Sx3300 battery, Castle ICE50 and Hubin FM-2SR timer. THAT is the intended power system for the T-Rex (and similar) airplanes. Some points of comparison:

* The AXI 2826 is being used very sucessfully by Bob Branch in his T-Rex. The Turnigy 35-48 and the Hacker 30XL (used in the RSM system) are the same size.

* The Arrowind 2832 is 6mm longer, and more powerful. For a given prop (especially when you get into the 12" to 13" sizes) it will draw somewhat less current and require a slightly smaller battery.

* Power conversion isn't free, the 2832 is about 1.2 oz heavier than the 2826 (aka 35-48) motors.

I think the really missing piece is the prop we intend to use, particularly the PITCH. I'll pick on Bob's T-Rex as an example - (btw he wrote this up in his thread too) Bob planned on flying his E-Rex with the AXI 2826/12 kv=760 motor and 12x6P prop. Works well. Then he switched to the new APC 13x4.5P prop. The 4.5" pitch prop must spin roughly 1200 RPM faster than the 6" pitch prop. the combination of the 760 kv motor and 4S pack meant the motor had to spin uncomfortably close to its RPM limit on 4S. Bob had the choice of:

> A. changing from the /12 kv=760 version of the motor to the /10 kv=900 version of the motor
> B. changing from a 4S pack to a 5S pack

Of course, Bob chose "B" and his set-up is comfortably back on its sweet spot. He could have chosen A and succeeded, but would have needed larger than the 3000mah (?) packs he had on hand.

You last statement about 5S weighing more MIGHT or MIGHT NOT be true. There are still some pretty big gaps in the batteries capacities available. Per Alan's excercise you can got through and determine that you need a pack of X capacity, but the the nearest size up might be a big jump. Thus adding one (or more) cells can let you use a considerably smaller cell. 5S pack built of small cells can weigh less (or more) than 4S of another larger cell. It was this thought process that drove the development of the Brodak 6S power system for the Strega.

Walter Hicks · « **Reply #5 on:** February 13, 2010, 10:42:00 AM »

RSM set up will go into a Brodak Cardinal! What about Scorpion 3026- 710 1000 watts, Or Turnigy 4250 , for T -Rex?. I will purchase the Brodak motor thanks Dennis.

Archie Adamisin · « **Reply #6 on:** February 13, 2010, 02:24:15 PM »

Rudy,

I guess this is the great thing about stunt. We can go down (2) completely different roads and still arrive at the same result. I would however caution those who wish to try ECL that you don't have to spend quantum amounts of $$$ to get a good reliable system that will fly anything out there.

Whether it be the Brodak Turn Key systems, Scorpion, E-Flight, Rim-Fire, Thrust, Dulsky, or Turnigy motors, you can do well with all these reasonably priced motors. The question I have for Rudy is about efficiency. You are flying with a 5S 4000 pack. What is your average power usage? What is your flight routine? Currently we fly an 80 oz Strega on 6S 2800's @ 5.3 sec/lap on full 67' lines and use only 1700 mah per flight. This is with 15 laps after the clover. We turn a 13 x 4.5 APC "E" prop @ 10,100 rpm. Motor temp after flight is 100 deg F @ 75 deg air temp. Battery temp is 95-100 depending on time of measurement after flight. So this system is running in my opinion very efficient. Max efficiency on this motor is probably in the low to mid 80% range.

Your motor should be capable of running in the 90% range, however you still have to use 5S 4000 mah packs to fly a T-Rex? Where is the benefit of going to this high priced equipment if there is no payoff in weight savings? If I bought a motor capable of running over 90% efficient, I would be looking into smaller packs to save weight. This isn't the case with all I have heard using these high priced motors.

Now, please don't misunderstand my argument. I have seen Mike Palko's Mustang and the Neu Motor in it and it is awesome!!

I have heard wonderful things about Paul's System. I have seen Plettenburg motors and they are without a doubt the finest motors I have seen. I wouldn't even sit here and tell you that I would set my Turnigy SK 42-50-650 next to your Plettenburg without feeling a bit out of place. But when they are in the air, and you can't see the guts, I will guarantee I get much more bang for the buck with my economy class setup than you do. It's quite literally is a case of watts/$$$. It will fly just as well at a fraction of the cost.

I have a 3 year history with Turnigy motors and a 15 year history with electric flight. I have several different motors, ESC's, and batteries. I have been very fortunate to have had the opportunity to experience many facets of this hobby. The real enjoyment I get out of this hobby is the opportunity to learn and try different things. None of the setup's I have posted have been those I would have any concern over. I have tested them and they work. Experimentation for me is over. When I recommend a setup, I ask how big a model, how heavy, how long a lines you want to fly on, & how much do you want to spend.

Walter,

Brian Eather & Bruce Hoffman of Australia are flying T-Rex's with the EPS 50 System from Brodak. They are using the 12 x 6P or the 13 x 4.5 P and are having no issues with power. Only negative I have heard was that they had packs that were too big. They are flying with 4S 3700's & only using 2200 per flight.

If you want to go to the 6S EPS 65 system, it will work too. Just need to have a Charger capable of charging 6S.

Archie Adamisin
Muncie, Indiana

Alan Hahn · « **Reply #7 on:** February 13, 2010, 02:48:26 PM »

Quote from: Rudy Taube on February 13, 2010, 02:33:47 AM

Hi Walter, (Alan and Bob)

My P-47 (T-Rex) has a Pletenberg 25-10 with a Hyperion 5S 4000 mAh battery. It will turn an APC 14x7E at 8800 RPM, and not even break a sweat.

I would not consider using less than a 5S battery on this size/wt./thick airfoil/high drag plane. That is if you want to have it fly like it is on rails and .....<snip>......
EDITORIAL ... DANGER, Please read at your own risk Please take medication 1st, as needed!

I'm not sure why the CLPA community thinks that there are many ways to do this E-power model power thing and get optimal results. CL has come to E-power very late, over 20 years after we were using it in the RC world.

....<snip>...
Regards,

Rudy,

The reason I say what I do is that it is completely true. There is NO inherent advantage to high voltage. We are not transmitting our power across miles of transmission lines, in most cases only a few inches (where high voltage does have advantages--which is why we have high voltage transmission lines--and why I use 240V to power my table saw (length of wire from my electrical service box to the saw)!

The motor really can be considered a transformer, matching the input volts and amps into generating output mechanical power. There is absolutely no difference in efficiency here--2s, 3s, 4s, 5s, 6s,....--nothing to be gained or lost by any choice.

All that matters is 1) total energy you carry, 2) motor kV chosen to match voltage, 3) prop pitch chosen to match 1&2. I won't include the ESC, because I think we all figure out that it needs to be chosen to handle the amp range and voltage range.

Just because RC guys don't understand simple electricity and magnetism, there is no reason to blindly follow them.

One thing that Archie says that I totally agree with. And that is that manufacturers do provide certain size batteries and fixed kV choices in motors. Therefore you do need to temper my "No advantage" comments with what you can actually buy. So in that case I might agree that a high voltage setup might be preferable to a heavier low voltage setup, simply because the available cell sizes might fit your energy needs better in high cell counts.

I don't want to get into the $$ equation. That is just the same argument that is used for choosing the most expensive glow engines as opposed to cheaper alternatives. I think that depends on personal choices and you will always have agreements/disagreements about that. I see advantages to most arguments here.

So this isn't a rant! I enjoy having the discussion!

William DeMauro · « **Reply #8 on:** February 13, 2010, 04:27:15 PM »

I am putting together an E-T-Rex also. I will be using the Turnigy SK 35-48-900 in mine. Batteries will be 4 cell 4000 or similar. I wanted to go this route because I wanted to match it as close as possible to my SV-11 without spending the bucks I spent on that one. I want to be able to use the same batteries on both. As far as I'm concerned I will push that Turnigy motor and see how it holds up. I can always switch it out to a Scorpion easy enough. This project is moving very slow due to a major renovation project on my house so updates on progress wont be that often.
William

Walter Hicks · « **Reply #9 on:** February 13, 2010, 04:40:23 PM »

Thank all of your for your responses. I live in Central California(where are the farms and dairies are) and Roger Anderson is the only one near me who is doing electric. He is going to use the T-Rex also with various Turnigy motors. I am a middle of the pack advanced pilot. As you can see I am moving in the direction of electric. So we are kind of young here as far as experince goes. Roger is going to be using another Turnigy on his Pathfinder Tomorrow.

I appreciate all the different kinds of responses. I am like I am sure some other CLPA pilots not super technical, and
want to start the learning curve without having to mortgage my house(couldn't anyway in California).

I have an Arrowind 2832 on the way. As well as an ICE 50 esc. William keep us posted on how that set up works for you. I think I am going to remove the Stalker 66 from my already built T-Rex ARF and use the method Bob Branch did and mount the electric in it.

It is nice to have several ARFs to work with before you have to build a plane for electric from ground up.

Rudy Taube · « **Reply #10 on:** February 13, 2010, 07:59:55 PM »

Quote from Alan: "...... Just because RC guys don't understand simple electricity and magnetism, there is no reason to blindly follow them. ...."

Your right Alan, we ERC guys don't know much. I guess we all just went to inferior Graduate schools. I am very sorry I even tried to make a comment. I erased my prior post so my inferior information would not pollute this forum.

I apologize to all who read my illinformed posts. Tomorrow I will make sure I tell my ERC flying buddies that they don't understand simple electricity and magnetism. Two of them work as engineers in the Aerospace industry and design satellite systems for the DOD. One designs electronic control systems for RPVs that are sold to the DOD, one is a fellow Airline Pilot, ..... but hey, what do they know?

Again, I am very sorry I posted here and offended you with our ignorance, it won't happen again.

Dennis Adamisin · « **Reply #11 on:** February 13, 2010, 09:52:01 PM »

Quote from: Walter Hicks on February 13, 2010, 10:42:00 AM

RSM set up will go into a Brodak Cardinal! What about Scorpion 3026- 710 1000 watts, Or Turnigy 4250 , for T -Rex?. I will purchase the Brodak motor thanks Dennis.

Hi Walter
The Arrowind 3526 selected for the Strega power system is similar ( I think just a hair larger) than the Turnigy 42-50. I have no direct experience with the the Turnigy 42-50 but specs look good, including the 195g (7 oz) weight. Looks like it is available in 600 or 700 KV, so that would make it a pretty good candidate for 5S. The 600 KV would even work well with 6S and something like the 13x4.5P prop.

Have to check the "List your set-ups" thread but I believe Will DeMauro is using the Scorpion 3026 in his excellent SV-11 on 4Sx3600 (I think)

Alan Hahn · « **Reply #12 on:** February 13, 2010, 10:10:21 PM »

Quote from: Rudy Taube on February 13, 2010, 07:59:55 PM

Quote from Alan: "...... Just because RC guys don't understand simple electricity and magnetism, there is no reason to blindly follow them. ...."

Your right Alan, we ERC guys don't know much. I guess we all just went to inferior Graduate schools. I am very sorry I even tried to make a comment. I erased my prior post so my inferior information would not pollute this forum.

I apologize to all who read my illinformed posts. Tomorrow I will make sure I tell my ERC flying buddies that they don't understand simple electricity and magnetism. Two of them work as engineers in the Aerospace industry and design satellite systems for the DOD. One designs electronic control systems for RPVs that are sold to the DOD, one is a fellow Airline Pilot, ..... but hey, what do they know?

Again, I am very sorry I posted here and offended you with our ignorance, it won't happen again.

Rudy,

Please don't take my comments as an attack---they really aren't.

I have stated my comments here and there --basically everywhere! Really what I say is true. There is no THEORETICAL reason to choose any solution over another. There may be practical--as I commented.

So please----don't take my comments as a personal attack--it really wasn't meant that way. I enjoy your comments, and I bet I could convince you that I am right (maybe after a few beers!) ! And I would give you the same chance to convince me! (Maybe after a few, I would agree!).

And I also fly RC, so I don't hold any bias for that. But I also don't take any guff either from RC guys! Hey we all enjoy flying something. For me sometimes it is RC, sometimes it is CL. Most times these days it is electric, but I still enjoy trying to tame the glow beast too!

Kim Doherty · « **Reply #13 on:** February 13, 2010, 10:46:26 PM »

Alan,

The reason I say what I do is that it is completely true. There is NO inherent advantage to having limited experience and even less to having virtually no competitve experience. If it wasn't for the RC guys who don't understand simple electricity and magnetism the systems you now enjoy would still be a figment of your imagination. I don't want to get into the $$ equation either because people lacking in experience may tend to gravitate to purchasing substandard equipment. (If I didn't know better it would almost seem I was describing YOU)

So Alan please----don't take my comments as a personal attack--they really aren't meant that way. They are really ment to highlight the pompous, verbal diarrhea that you spew so frequently nowadays. So do yourself a favour. Go WIN something (anything!) then do it again and again until you have boxes and boxes of trophies and plaques then win a few national championships (you really only need to win a few) then give it a whirl at the world champs once or twice or say seven or eight times then puff your chest out and tell Rudi that the system he is using is so wrong or so yesterday. (heck tell Paul too) Go ahead we'll wait here for you. I'm sure with your advanced degrees and higher learnin you will have it done in no time. And when you come back don't forget to apologize to Rudy. Your lack of respect is one of the prime reasons I and others no longer bother posting in this forum.

Kim.

William DeMauro · « **Reply #14 on:** February 14, 2010, 06:27:55 AM »

"Have to check the "List your set-ups" thread but I believe Will DeMauro is using the Scorpion 3026 in his excellent SV-11 on 4Sx3600 (I think)"

I have flown my SV 11 with a 4s 3600 and the Scorpion 3026-890 v2 but I am at the upper limits of that battery, especially with the 13x4.5p on it. I prefer the 4000-4400 range batteries as they give me some headroom and the extra bit of noseweight I like in my plane.Since I have them I will try the 3600 in the T-Rex but I am predicting similar numbers to my SV.

Archie Adamisin · « **Reply #15 on:** February 14, 2010, 04:07:23 PM »

Walter,

I am so sorry that this thread has taken this really sour turn. You can obviously see that there is a major difference in opinion in how to approach your question of powering a T-Rex with an electric power-system.

My suggestion is to look in the list your set-up and pick what works best for you. Obviously there is no lack of opinions in this forum for what you should use, but I suggest that you look over what people have used and used successfully and go with it.

I wish you well in your conversion and hope that you will post your results.

Take Care,

Archie Adamisin
Muncie, Indiana

Walter Hicks · « **Reply #16 on:** February 14, 2010, 10:31:26 PM »

Thanks everyone again for your input , Roger Anderson, Ron Anderson and I will be going Electric with the T-Rex, so we will have fund learning the ins and outs of Electric C/l.

Alan Hahn · « **Reply #17 on:** February 15, 2010, 07:36:57 AM »

Quote from: Kim Doherty on February 13, 2010, 10:46:26 PM

Alan,

The reason I say what I do is that it is completely true. There is NO inherent advantage to having limited experience and even less to having virtually no competitve experience. If it wasn't for the RC guys who don't understand simple electricity and magnetism the systems you now enjoy would still be a figment of your imagination. I don't want to get into the $$ equation either because people lacking in experience may tend to gravitate to purchasing substandard equipment. (If I didn't know better it would almost seem I was describing YOU)

So Alan please----don't take my comments as a personal attack--they really aren't meant that way. They are really ment to highlight the pompous, verbal diarrhea that you spew so frequently nowadays. So do yourself a favour. Go WIN something (anything!) then do it again and again until you have boxes and boxes of trophies and plaques then win a few national championships (you really only need to win a few) then give it a whirl at the world champs once or twice or say seven or eight times then puff your chest out and tell Rudi that the system he is using is so wrong or so yesterday. (heck tell Paul too) Go ahead we'll wait here for you. I'm sure with your advanced degrees and higher learnin you will have it done in no time. And when you come back don't forget to apologize to Rudy. Your lack of respect is one of the prime reasons I and others no longer bother posting in this forum.

Kim.

Kim,
I'm sorry you feel the way you do.

I never said the system Rudy is using is wrong, I have said there is no inherent advantage to a low kV-high voltage setup.

That is extremely easy to prove-- I have shown it here many times.

I have yet to see anyone else show me that I am wrong. I am ready to have someone do that--and I will be the first to admit my ignorance if they do.

So fire away--but this time with a little math.

Paul Walker · « **Reply #18 on:** February 25, 2010, 12:51:39 PM »

It's too bad this thread had to degenerate into what it did. The comment about ERC guys was unnecessary.

I enjoy this forum and read what I choose to. I do try to read everybodies comments and learn what I can from each. As far as the equipment I use, it is very simple. I didn't want to reinvent the wheel, and I wasn't going to jump into ECL until I saw a system that I thought was "right". That didn't happen until I was in Spain for the 2006 WC's. Kim had his Shockwave there and to say the least, I was impressed. If it wasn't for some learning curve issues, he would have placed significantly higher.

Kim was gracious enough to share his knowledge with me on his system. My first plane copied it directly, and it worked great. Once I had a good starting base, I started to find ways to get weight out of the power system. I am now 5 ounces lighter with all the power necessary for even my heaviest planes. It is now going in a 62 ounce package, and I am very anxious to work with it. For my application, the motor of choice has worked very well, and has never been an issue. They have all been rear mounts, and have never shown any bearing wear issues (unlike other motors that are rear mounted). The batteries are more expensive, but try to find a lighter one for the energy inside it (5S2P 4000 at 14 ounces).

There are different motors, batteries, and ESC available, and I will pay close attention to everything posted here. I clearly do not think that my system IS the only way to go. It just happens to be the one I am using. If something more powerful and lighter (and reliable) comes along, you can be sure it will be in my competition plane very quickly. Nothing sacred here.

Please keep this dialog flowing, and please treat all with respect.

Thanks

Paul Walker

Dean Pappas · « **Reply #19 on:** February 25, 2010, 09:03:55 PM »

AMEN!

signed,
that moderator guy who tried very hard not to step on peoples' toes.
Dean

Author Topic: Power Systems for T-Rex (Read 2259 times)

Walter Hicks

Alan Hahn

Walter Hicks

Alan Hahn

Walter Hicks

Alan Hahn

Kim Doherty

Walter Hicks

Alan Hahn