algutkin

My Feedback: (1)

Thanks Greg,

I didn't know about the Matchbox. I just came back from the AZ Electric Festival where I looked inside some of those monster Yaks and was confused by all the electrical connections. Now I understand.

Based upon my battery inventory I can only do 10S, 4,000 mah, so the finished craft may not be able to perform like a 3D plane.

Try to keep warm, in between shoveling snow that is. I can't imagine 12 feet plus, of snow.


Al

P-51B

My Feedback: (5)

Al,

If you are thinking about a set up where a matchbox may be needed, you may want to consider using hitec digitals and using their programmer to make everything match. Less parts to fail and good servos to boot!

algutkin

My Feedback: (1)

P51b,

LOL.

I can't use those servos, I'm too cheap, I'm a lousy pilot, I'd never be able to take advantage of the servo speed, and my aircraft usually don't last very long.

I'm using the same setup as Greg, The DX7 with the included servos and standard 3004 Futabas. In addition, my planes don't need 6 volts to the servos, I bought a bunch of 4 cell nmh receiver batteries and I'm planning to use them.[&o] Greg is used to building 3D airplanes, his configs are severe overkill for a Mustang. I sure hope he has a sponsor, because after reading about Greg's conversions, his finished products cost more than a brand new PT Cruiser.

Al

normgoyer

Hi Al, we weren't that lousy a pilot we both surrvived 100s of hours of Texan flying not to mention the military jets you flew. Norm

P-51B

My Feedback: (5)

Al, I understand!


Just an FYI though, they make a range of digitals, from less expensive to the ones used on the giant scales with titanium gears.

flyingace451

Ok just so you guys know what we're talking about with the Eflite 160, here's my ideas on it. To put it simply, this thing is a BEAST. Greg's pictures make it look small, but it is roughly the size of a fist, and it puts out and will take a ton of punishment. I highly recomend it for any large scale conversion...plus with the 30% discount I get at the LHS for working there, I can actually afford it.

algutkin

My Feedback: (1)

Greg,

I just finished the main wing and attached the gear doors, looks like some spacers have to be made which will allow the doors to close flush. In addition, the 4-40 push rods were missing from my kit, I just have the clevises. This poses a delema, I could buy extra long 4-40 rods or mount the elevator and rudder servos in the tail instead. It will probably screw up the scale look of the P-51 to have servos sticking out, so, the alternative would be to make covers, similar to those in the wing and mount them in the sides of the fuse, flush with the existing lines. The downside is that most likely the plane will be tail heavy anyway and this will make it worse. The upside is that the controls would be rigid and the fuse would be empty, great for mounting the batteries.

If you ever get out from underneath the snow and get your electricity back so the computer works, you might want to take a look at the situation, I'm interested in your opinion.

Al

wollins

subscribed

Gordon W

Hi Greg

Checking the specs of the UBEC, the max input voltages for the various types are 35V, 40V and 45V. The off-load voltage of a 12s lipo could be as high as 50.4V, so isn't there a potential problem here?

Or will you power the UBECs from one 6s pack, presumably the one that has its -ve terminal connected to the RX?

Cheers

Gordon

wollins

Hey Gordon,

I can't presume to be able to answer for Greg but what I think he's doing is setting up two UBEC's in series so as to get the voltage capability. I only say this because I had a situation where I was concerned that my UBEC wouldn't be able to handle the amp draws of my high torque digital servos and I was advised by Jeff at Koolflight that I should consider a parallel UBEC setup for redundancy, lots of current capacity and peace of mind.

With this in mind I guess two UBECs could be set up in series to cater for higher voltage requirements.

Just my 2 cents!

Colin.

normgoyer

Hi, you guys are loosing me, why aren't you using high capacity separate receiver/servo battery such as the new Li-polys for this application? Why is the UBEC better? Norm

Greg Covey

Hi guys,

It looks like I missed a few posts this week. Fortunately, we are near the middle of Lake Ontario and only got 3' of snow. The East end called the Tug Hill Plateau area was buried with 10'-12' of snow. My absence this week was mainly due to work.

Norm,

The UBEC simply replaces the receiver battery so you run everything off the main flight pack(s). It is a mindset change for a pure electric enthusiast like me versus an R/Cer used to glow or gas powered planes. For me, never having to recharge a receiver battery is best since that is what I am used to.

Colin,

The two UBECS (or receiver batteries) are not used in series but rather in parallel. By using two (of either UBECs or Rx. Batts.), I obtain the added safety of never having a jammed retract servo take out my receiver (and plane).

Gordon,

You are correct. I forgot to mention that both UBECs will feed off the same 6s LiPo pack. Only the second 6s (or 4s) LiPo pack will be floating above ground to feed the ESC.

flyingace451,

Yes, as I mentioned before the E-flite Power 160 is the same as an AXI 5330 motor which can deliver 3000 watts burst. I have started my motor mounting so I hope to post some pictures this weekend with my Graupner 16x8 test prop.

Regards to all.

normgoyer

Thanks Greg, I have been using BEC in small aircraft but a separate batery for the receiver and servos in my larger aircraft. Norm

algutkin

My Feedback: (1)

Norm,

What Greg is doing is what all 3D guys do. They use a Ubec to put out 6 strong volts to the servos, the nimh 4 AA battery pack will not do this. The whole thing with 6 volts involves around making the servos go faster, faster servos mean better 3D response. The reliability factor is questionable and many experienced pilots will debate this to the end of time. I know that you know all this crap, but, I wanted to post it anyway just to feel better.

All my big planes have seperate receiver batteries, mainly 4 cell nimh, 4000 mah. The charging is easy and at least you know the servos will work with those reliable nimh batteries. They just don't work as fast.

When was the last time you saw a WWII warbird waddle in a hover, or do slow spins while traversing a wide cirlcle in hover mode?

Anyhow, just for giggles, I setup the P51 in Motocalc with Greg's minimun setup of 10S and the 16X8 prop and the results seemed to be outstanding, well beyond any scale performance for the Mustang. What 3D pilots dont' understand it that these scale planes don't really jump off the ground and go straight up. They accelerate gradually, the tail comes up, they may even bounce a few times on the grass before they actually leave ground effect. The speed buildup on takeoff takes time, but those 3 point landings are another story.

Greg, ancious to read about the prop. test, carry on.

Al

normgoyer

Thanks Al, those were facts that I never heard of. Of course I don't fly 3-d just nice lumbering big old scale models. I would like to see a modern F 22 or F 18 jcok fly the Wildcat I had. It took three hands to clean it up after climb out and muscles like our governor. Chain drive landing gear, 32 cranks, electric Curtiss prop and hydraulic flaps and no computers to help you out or fly by wire to ease the strain, oh yes the good old days, or where they? Norm

rc34074

My Feedback: (5)

Greg Covey-

I have seen advertisements for the new Apogee Lithium Manganese batteries. Are these a good option for larger planes like this? or 60 size planes?

Ed

Greg Covey

Ed,

I am not familiar enough with the Lithium Manganese batteries to answer your question. However, I can say that battery weight is less important on the bigger models than it is on the smaller models. With this in mind, you do not need to always use Lithium Polymer cells.

Al,

You missed a few things that should be considered. First, the extra voltage on a servo does not just increase speed but also increases torque. When using a standard size servo like the JR DS-821, it is important to get maximum torque on a giant-scale model like the P-51D which weighs 16lbs. In this manner, the control surface will more exactly follow the stick movement without added latency or blowback. Essentially, this provides better scale maneuvers.

DS-821 Specs:
Torque: 72 oz/in @ 4.8v, 88 oz/in @6v
Speed: .19 sec/60° @ 4.8v, .15 sec/60° @ 6v

Second, it is possible to have both 3D and scale flying skills.

The decision has been made (by popular feedback) to go with flaps and keep the bombs on the wing as in the stock Hangar 9 P-51D design. I will, however, be adding a Robart #121 retractable tailwheel controlled by an extra DS-821 servo.

Regards.

wollins

Greg,

Since I consider you the "guru" of conversions (I've followed quite a few of them) maybe you can help me out with your opinion.

Since I'm getting more and more into bigger conversions (above 60 size) I've come across a situation which appears to be common because of the bigger sizes of these planes.

ESC battery leads and ESC receiver leads don't reach back far enough. As we all know the preferred method of ESC placement is typically as far forward as possible to take advantage of the cooling of cowl vents etc.

The problem is since most of the ESCs have relatively short battery leads (Jeti's especially) and receiver leads, in most of my conversions now, I am barely able to get the ESC's power/battery leads to reach the battery since I tend to need my batteries fairly far back to balance. I also have a hard time getting the ESC's receiver/throttle lead to reach my receiver as well!

So to solve this problem I have been extending the Esc's power/battery leads by soldering on heavy gauge wire "extensions".

As for the ESC's receiver lead ... since the receiver is typically beyond the reach of the ESC's receiver/throttle lead, I typically end up using a heavy duty servo extension to solve that problem.

1. I would imagine this happens to you as well since you've been converting giant scale planes! Are you using that same "fix" that I am or is there some other method that I should know about?

2. Or are you solving this by extending the Esc's leads on the MOTOR side as opposed to the Esc's leads on its BATTERY side? (as I do) If so, is that better? Why?


Thanks!

Colin.

Greg Covey

Hi Colin,

I am doing the same thing that you described. In some cases, I make an extension cable for the power lines with Dean's Ultra connectors on both ends. Other times, I simply solder longer wires onto the power lines and then shrink wrap the bare wire.

In addition to front end ESC cooling, it is best to keep the three wires between the motor and ESC as short as possible because they are high power noise radiators. The peak power on these 3-phase AC lines can be very high.

Another problem with large scale models is the lack of access to the battery packs. Once the wing is installed, the packs are often sealed up for the flight. In the past, I have used various techniques to work around the problem as I prefer to keep the wing on for a day at the flying field.

On my P-51D review, I will be introducing a new part called the 6970 Arming Switch from [link=http://www.maxxprod.com/mpi/mpi-21.html#arming]MPI[/link]. In addition to adding safety by keeping your motor disarmed until you reach the flightline, it allows you to easily disconnect the ESC to recharge batteries in the plane as long as you use a balancing charger. When using two packs in series, you can also use an Arming Switch to disconnect the two packs so that they can be charged at the same time (by separate chargers) without a ground fault issue. Simply install the receptacle to the fuselage side and connect it in-between the battery and ESC.

I'll descibe this in more detail when I get to that part of the assembly.

algutkin

My Feedback: (1)

Greg,

Wait until you get the the point of installing those bombs on the wings. Sit down, because you might want to be secure while you laugh your butt off. Those bombs are slightly oversize for the size of the plane. I never saw a fighter with bombs that large. Talk about deviations from scale......

Oh yes, the landing gear doors do create somewhat of a minor trimming problem. However, the mounting was actually very easy compared to other planes. In the past I didn't put them on any other model, I always figure one bad landing and the doors will become history.

This plane is going to look and fly like a wimppy bird, not the mean and lean beast, that is was. Hopy you find ways to modify the appearance witout getting too far from the scale design.


Al

kihei11

My Feedback: (13)

Greg,

you just have the best job ever!!!

Randy and Kyle, Kihei Hawaii

P.S. Wow it got cold here last night felt like 65 with the wind chill.

Greg Covey

Hi Randy,

We call 65 degrees a warm wind, not a wind chill. Wish I was there!

Al,

Thanks for the heads-up. I'll do some research on the bomb size to see if it is scale or not. I may also have some hop-up information on the retract mechanism as several friends are building the P-47 and claim it is the same retract. A few people have had welding issues.

The motor can be mounted several ways. Here is the one I chose.

The E-flite Power 160 motor uses a similar x-mount to the AXI 5330 motor. This meant that the nylon spacers and screws from [link=http://www.hobby-lobby.com/motor-mount.htm]Hobby Lobby[/link] could be used to mount the motor in the P-51D. Since the 4" long 8-32 screws were not long enough, I needed to extend the firewall by making a box from 5-ply aircraft grade plywood and hardwood blocks.

Greg Covey

Before mounting the extension to the firewall, I drilled several air holes and mounted #10-24 T-nuts. The extension was coated with epoxy and then screwed into place. I also used some Pacer Z-42 Thread Locker on the 2" long #10 screws. Not shown in the first two photos are two smaller blocks that were glued and screwed into place on each side of the narrow middle section. They can be seen in the motor photos.

I used 3-1/8" of spacers (two 1" spacers, two 1/2" spacers, one 1/8" spacer) between the x-mount and the firewall extension box. An additional 1/4" spacer was used to take up some screw length so it didn't run into the original firewall. This provided about a 3/16" gap between the spinner backplate and the cowl. The 4" long screws were easily secured by a screwdriver entering the front of the cowl. Again, Pacer Z-42 Thread Locker was used to keep the screws secure.

Greg Covey

I did a quick mounting check of my Graupner 3-blade 16x8 test prop. The hub thickness was good but the center hole was 12.7mm instead of my desired 12mm. I added a single turn of masking tape around the 12mm prop adapter shaft and the prop fit perfectly.

On to mounting the ESC so I can add the cowl bottom and go back to finishing up the wing...

algutkin

My Feedback: (1)

Keep on working Greg.

By the way, that prop is a monster, you will need full right rudder. Man that thing puts out lots of torque on just 6S with the Axi 4130. If you try it on a work bench, better make sure the bench is firmly attached to the floor. The Graupner is nothing like the Master Airscrew 16X8, The Graupner pulls lots of air, and as you know, it's one heavy prop.

Al