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        Discussion Tail Rotor ESC for Airships

#1 Ed Couch Jan 15, 2013 07:49 PM

Tail Rotor ESC for Airships
 
Gentlemen

One of my big problems in flying our airships are that most of the tail rotor ESC's are built for use in ground vehicles that can give one forward or reverse when needed. For the blimps it translate to right or left directional control. Here is the hitch. Castle Creations and several other designs will allow you to set the range of reverse to 100 percent or what should be equal in rpm and amperage as the normal forward speed. In 90 percent of the cases that is not the case. What I am looking for is a speed controller that will give me the same rpm in reverse as it will forward. Presently its something that we have to live with as I have at least 10 Castle Creations ESC's in airships flying at this time. They work but its not any fun. This occurs not only in brushed motors but brushless as well.

My question is does anyone know of an ESC that will give 100 percent equal power forward and reverse? The controller needs to be able to handle brushless motors up to an Eflite 25 and up to 4 cells litepolly packs. 40 to 80 amps continuous. Big order but there should be something out there. Castle keeps saying we do but we can't seem to get it to work. Any help appreciated. ed

#2 aerocal Jan 16, 2013 02:06 AM

Im wondering the same thing.Im flying an oldschool Blimpworks brushed setup.Thinking about converting to brushless but I cant seem to find a brushless ESC that will reliably work in both directions evenly.

#3 ED B Jan 16, 2013 09:35 PM

Ed,

I used to fly a 13 ft. Aerostar blimp for the ECHL Trenton Titans. I found that if the tail fin prop was mounted backwards when the motor was run in the "forward" direction, then when you went into "reverse" the prop was much more efficient while the ESC/motor always seemed to be less efficient when run in reverse. The inefficient prop and efficient ESC/motor acted the same as the efficient prop and inefficient ESC/motor. If you haven't tried that, you should give it a shot. It's a simple cost free solution that worked for me. The blimp had a speed 400 brushed motor in the tail fin. I don't know if you will have the same results with a brushless motor. Good luck.

Ed

#4 Ed Couch Jan 17, 2013 09:24 AM

Ed

As they say "been there and done that". Normally we use two props back to back to provide equal thrust and drag both ways if the rpm match. That is why it is so important to have the rpm the same. There is really no reason why it can't be done its simply a matter of coding in this day and age. I used the set up you mention on a small 7.5 footer and learned to live with it but I did eventually find a brushed esc that worked. It came out of a small car that a friend had but would not handle over 4.8 volts. Thanks for the comment though. My main concern now is the brushless motors up to a 25 Eflite on 3/4 cells. ed

#5 pyronaught Jan 18, 2013 10:00 AM

1 Attachment(s)
I used a Turnigy TrackStar 120A brushless short course truck ESC in combination with two 12x5 three blade beechwood propellers mounted back to back for the tail rotor on my 40ft hot air blimp. I did not notice any difference in thrust between forward and reverse. I did not measure the thrust though, so there still could have been less in reverse but I could not detect it by feel. I'm familiar with the problem you are referring to and it is indeed an annoying one because you have no way of knowing what you will get until you buy the ESC and try it. Since the RC car people probably don't have the need to travel full speed in reverse, it doesn't bother them.

http://www.hobbyking.com/hobbyking/s...dProduct=22632

#6 Ed Couch Jan 18, 2013 06:41 PM

At about 60 bucks a unit its worth the try. I know all of us appreciate the information. Thanks I will follow up on this. ed

#7 pyronaught Jan 18, 2013 09:48 PM

If I get a chance I'll check it out again this weekend. I should be able to tell just from the sound if it is equal in both directions. I remember I had to program it to get it working right because the default settings were nowhere near equal in reverse.

#8 Ed Couch Jan 18, 2013 10:07 PM

Thanks, much appreciated. If you have an amp meter put it inline as well and check amps under load. See if they are same both ways. Again, appreciated.

ed

#9 Ed Couch Feb 07, 2013 01:00 PM

Gents

Per Pyro's suggestion I went ahead and ordered the ESC suggested and programming card. I was able to play with it a little this morning and thought I would go over the findings. First I utilized the card to preset the ESC to function both forward and reverse utilizing breaking fairly heavy before going in the opposite direction. One thing they did not have on the card was percentage power for reverse with default being set at 50 percent. This is the problem we have had since day one. After programming I tested everything and as suspected one way was about half the power of the reverse direction. Now I followed the instructions which are fun for setting the reverse power utilizing the transmitter. Following the beeps and tones was something out of Star Wars and R2D2 would have been proud. It took me a few times but I finally picked up on what was happening. Programmed for 100 percent reverse and turned things off at switch. Ok, now for the fun part. Tx back on, ESC lead plugged into the aileron output, remember this is for directional control and not throttle, flipped switch on ESC and let the unit do its thing to arm. Now for good part, moved stick right slowly to full thrown and tail rotor assembly is running like banshee. Moved stick back to center tail rotor stopped. Moved stick opposite direction to full position and speed came right up and about matches other direction. In other words we have equal right and left. Pyro you did it. Now I have to take this knowledge and go back to the Castle units and see if they will work the same way. If not I will be placing an order for more of these units. At about 65.00 dollars a unit, they are worth every penny spent. Also, the crossover from one direction to another is minimal, not as good as a brushed motor but much better than what we have been using on the castle units. Again, thanks to all for your comments. ed

#10 pyronaught Feb 07, 2013 06:12 PM

Yeah, once you get the hang of dealing with the R2D2 programming you can get them to work as a good tail motor ESC. It's tiresome to wade through all the beeps while counting them to figure out where you are in the process, but at least you only have to do it once. Too bad there is no way to download settings into them via USB or something, otherwise we could just post the correct settings on a forum like this and people could download them and avoid all the hassle. The cards are nice when they have what you want, but it sounds like that wasn't the case for this ESC. I don't think I even got the card for this one, or if I did then I ran into the same problem you did because I remember having to suffer through all the beep counting to get it working right.

#11 Ed Couch Feb 08, 2013 11:04 AM

Finally got the Castle Creations ESC for Cars in this case the Mambo Pro to work as we have discussed earlier. I used the computer program to set everything up as far as drag brake, punch etc as well as setting 100 percent braking for reverse. Test run same old same old. Good speed one way about 60 percent the other. Now for the kicker. I reprogrammed the ESC via the transmitter listening for the beeps and chims. Followed the exact same format as that used in the Hobby King unit only for the reverse breaking. Reset to 100 percent. I then set it back up on test unit. Hooked up amp meter in line and tested both directions for any varience. Nada, both directions running the same. I was showing about 14.5 amps with the set up I was using. The test assembly was a lower fin from a 20 foot airship I flew for a couple of years but is now in storage. Now I know how to go about setting up all the units I have operational and a couple of have in reserve. Thanks everyone for your comments and help.

#12 Richard N Apr 13, 2013 08:58 PM

Ed,

Is there a reason for not using a helicopter tail rotor drive or reversible pitch prop like the indoor 3D guys have been using?

Using this would remove the need for custom ESCs and for the motor to reverse direction giving you faster response. If your reversable pitch blades were symmetrical in section, you would have equal thrust in both directions.

#13 Ed Couch Apr 14, 2013 12:03 PM

Standard tail rotor system would work fine on small ships but I would not use it on something over 20 foot long plus the complication factor and so many moving parts. Doing over 120 flights per season things can just get out of hand. I know its been tried several times over the years but all went back to the standard system utilized at this time. ed

#14 pyronaught Apr 14, 2013 10:44 PM

Isn't a helicopter tail rotor just a prop that only spins in one direction? Without the counter-torque of the helicopters main rotor, such a tail rotor would only be able to turn in one direction. In a helicopter, moving the tail in the direction opposite to the thrust of the tail rotor is done by slowing the rotor speed so that it no longer counteracts the main rotor torque. You don't have that ability if used on a blimp, so you would only be able to turn in one direction.

Another way of making a blimp tail rotor would be to use one of those variable pitch props that can change the direction of thrust almost instantly without changing the motors direction of rotation. The only down side is you need an extra servo to operate the prop pitch and you are more limited in the choices of prop/motor since there are not very many varieties of these on the RC market. Something like an ElectiFly V-Pitch would work for medium size blimps though and would be good if you needed really fast response times for turning.

#15 Ed Couch Apr 15, 2013 08:50 AM

The tail rotor assembly has enough throw in most cases to go positive and negative as needed. It always seemed overally complicated as stated earlier. For playing around with it would be fine but for commerical work and keeping the KISS principle in play it has never panned out. I personally hate the tail rotor systems using brushless motor due to the time delay going one direction to the other or the crossover time that is not there with a brushed system. It took a bit getting used to but works fine once the ESC is properly set up. Now it is the standard and you see very few brushed systems in use commerically. ed


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