Back to Post
| Username | Post: There's a world of servos out there | |
|---|---|---|
|
Anonymous |
 11-03-03 03:09 AM - Post#29269
I've been thinking about the whole "Futaba 401 at 6V" thread from a month ago, and servos keep coming to my mind. I was thinking about how all throughout that thread, the only servos that were mentioned were "aircraft" servos (i.e. the Futaba 9253), and how for the most part all aircraft servos are rated at 4.8 volts. That got me to thinking about the world of car servos. For example, in aircraft circles we have the 9253 (and it's a great servo), but for cars there's the JR Z8450, with 98 oz./in., .08 transit, all-metal geared, rated for 6V usage, and it's only $20 more expensive than a 9253! Other examples of some of my favorite car servos are: * JR Z8550 (180 oz., .15 transit, all-metal gear digital, $120) * JR 590M (85 oz., .15 transit, all-metal gear analog, $45) All 3 of these are widely used in car circles, have good reputations, and are all rated at 6 volts. So my question is, why are these so often overlooked for aircraft use? Is there a difference in case size? Are the servo control electronics somehow incompatible with heli gyros? This isn't intended as a flaming thread in any way. It's just really got me curious as to why we aircraft guys seem so fixed on 4.8 volts, when there's such a wealth of great servos out there in other applications. Oh, and I almost forgot.. we never answered this in the other thread. If I use any other digital servo besides a 9253 with my 401 gyro, and I have the DS switch on (270 Hz pulse drive), will I damage the servo? What I mean is... is the 270 Hz pulse a standard spec, or a Futaba exclusive? If I'm using any other digital servo, should I leave the DS switch off? |
|
|
SpinCycl Senior Member Posts 279 
|
11-04-03 01:55 AM - Post#29369
Good thinking buddy. I have often thought the same thing. As for wing servos and cyclic/collective, I would have no problem using a "Car" servo. In fact some of them are a better deal. BUT............ For the Futaba Gyros, I would not mess with something that works WELL in a COMBO of sorts. We all have to admit that these gyros work great AS-IS and don't need 6v to work well. Sure, you could use a fast car servo, but I would not reccomend it. I do caution, though. Some of these car servos have really expensive replacement gears. The aircraft servos like the 9252/53 have very cheap gears. (probally because they strip every time :-)
|
|
|
Anonymous |
11-04-03 02:13 AM - Post#29372
My thinking on using a 6v system is that since NiCd batteries tend to fail in a "closed" mode, the loss of one cell in flight still leaves you with 4.8 volts, which any radio system can still handle (at least long enough to get you to the ground). Losing one cell on a 4.8 volt system only leaves you with 3.6 volts, which might as well be completely dead. I could be wrong in my thinking (and someone please correct me if I am), but it seems like running a 6v system gives you a bit of a safety margin. Also, I'll grant you that metal replacement gears are more expensive, but I can also tell you from personal experience that a 590M and 8550 are built like tanks! If you could have seen the torture that I put my T-Maxx through... 
|
|
|
reddragon Full Time Senior Member Posts 3870 
|
11-04-03 03:59 PM - Post#29404
Buddy, I see your point regarding the use of servos that are typically applied to other uses such as car use or boat use. I use whatever I deem fit. I have many cars as well. Sometimes some of the servos from my cars end up in my helicopters! As far as using another company's digital servos with the Futaba GY401; I have not seen it done. This is NOT to say that it CAN NOT be done. I would be interested to hear from those who have done it and are still using the set up today. The majority of the people out there use the brand to match brand set up when it comes to digitals. I would guess that it works best for them and they don't want any problems later, why tempt fate? You can however use off brand servos that are not digital. Just switch the DS switch to the non digital mode. If you don't and you use an analog servo, the servo will be pounded to death! 
|
|
|
Charlie Senior Member Posts 366 
|
11-04-03 07:05 PM - Post#29412
Quote:I am using a Hitec 5925 digital ultra speed. I have been flying this about one and a half years and never had a problem (works great). It holds rock solid (with my flying skills). I'm not a hard flier. The reason for doing this is I couldn't get the 9253 when I bought the gyro. |
|
|
SpinCycl Senior Member Posts 279
|
11-04-03 08:06 PM - Post#29414
I too have been considering the 5 cell safety margin. But, everytime I think it's a good idea, I have to come back to the facts. 1. In my experience, I have NEVER seen or had a crash from a cell going bad. 2. Most battery related crashes are from low charge state. (flyer forgot to check the pack before flying)  3. One of my fellow flyers I know crashed becase of the REGULATOR!, NOT the battery.  Don't get me wrong, I think 5 cell is a good idea. But, I can't see using 5cells and then cooking a gyro/servo, or using a regulator. In my experience, we should SIMPLIFY the electronics to keep reliability up. Car/Boat servos are OK in my book.... eventhough I still stick to aircraft 
|
|
|
galifrey Senior Member Posts 227 |
11-04-03 10:39 PM - Post#29420
If you are really kean you can use some of the KO Propo Servos with 0.06 transit times at 7.2v and a regulator.. Now they own even the airtronics WRX servos 
|
|
|
Anonymous |
11-05-03 02:16 AM - Post#29429
Still looking for the definitive answer, though: If I use any digital servo other than a 9253, do I turn the DS switch on or off? Do all digital servos operate at 270 Hz, or just the Futaba 9253? |
|
|
reddragon Full Time Senior Member Posts 3870
|
11-05-03 04:08 AM - Post#29431
Buddy, You're going to have to do some homework here if you need a more definitive answer. Apparently Charlie has used a Hitec 5925 digital with good results. He must have his GY401 DS switch in the ON position...right Charlie? The frame rate of the Futaba GY401 and GY502 is 270hz. The frame rate for the Futaba GY601 is 330hz. The frame rate is how much information is sent to the servo every millisecond. The faster gyros send more information in the same time frame hence the faster operation-more precision. The fact is it may be overkill on their high end GY601, most of us do just fine with their GY401. After checking information on both JR and Futaba digital servos they both deliver pulses of information to the servo motor six times faster than standard analog servos. Standard sevos typically transmit information to their motors at 50 cycles per second and the digital servos transmit information at 300 times per second. I would suppose that the other manufacturers digital servos operate at the same transmission rate and that is why Charlie is able to use his Hitec digital servo. Hmmm 
|
|
|
reddragon Full Time Senior Member Posts 3870
|
11-05-03 04:16 AM - Post#29432
For the record (by no means the gospel or the last word) I use 4 cell (1400 mah and up) packs for my helicopters. I don't see the need to use a five cell pack but others do. I know that SOME of our equipment CAN take the extra voltage but it really doesn't matter to me. I don't have to deal with regulators or other things like that. To me if I have one it is just one more thing that I have to worry about. Then again I don't sepnd my afternoons doing space age flips, tick tocks and piros...et al. But alas.....it's just how I operate. Others do JUUUUUST fine with a five cell pack. Dos centavos
|
|
|
Topcat Senior Member Posts 905 |
11-05-03 04:41 AM - Post#29434
Just a note as It happened tome. Do not run a 9205 high speed futaba servo with the futaba gy401 in digital mode. It wreaks havock and WILL burn the servo out. My 9205 WAS a good speed servo. I was flying and everything was good. then the tail just wouldn't do anything. The servo developed a DEAD spot init. Most likely caused by the 401 being in digital mode and the servo not a digital servo. Tis a BIG NO-NO
|
|
|
Charlie Senior Member Posts 366
|
11-05-03 11:25 AM - Post#29440
Quote: No! I run mine with the DS switch off. From what I understand, the DS mode is only for Futaba digital servo's. I never did any research on this, but I have read on other forums where people have had problems when they use other digital servo's with the DS mode on. So I have been a little scared to try it with the DS mode on. I would hate to have a tail servo fail, my flying skills aren't the very best. I don't fell I need it anyway, it seems to work fine with out it. I have had people fly my heli, and done some pretty hard 3D moves (not real crazy) and it held great. |
|
|
Anonymous |
11-05-03 01:31 PM - Post#29445
See, I would have guessed that Charlie had the DS switch off. What I understand of digital servos is that the servo's IC is what translates the "analog" signal from the receiver into a high pulse rate drive signal for the servo motor. This is why I've been wondering what the purpose of the DS switch is on the 401. If a digital servo has the circuitry in it to generate the high pulse rate signal it needs, then what good is a 270Hz pulse drive from a gyro? Does it really give increased performance, or is it just a gimmick? What would be really cool is if we could get someone like Jim Mahoney to take a 401/9253 combo, and test it with the DS switch both on and off, and see if there's any measurable advantage. I apologize if I'm missing something here. If I sound frustrated, it's because I know what question I have in my mind, but I don't seem to be doing a good job getting it out in words. |
|
|
reddragon Full Time Senior Member Posts 3870
|
11-06-03 01:45 AM - Post#29495
I was wrong. But in "theory" since Charlie's servo is digital it should work with the DS switch on. (don't try it Charlie) But as I have said before when you use a digital servo with a gyro in digital mode the brands should be alike and matching, Futaba for Futaba and so on. I read these posts at work today but I couldn't wait to come home to respond. Buddy, your point is not lost on me and I think I understand, no need to apologise. I for one know there is not much difference from the GY401 to the GY502. Performance wise it is minimal. I also think it is minimal going all the way up to their top of the line F3C pattern GY601 which must be used with their S9251 digital servo. Do we really need an LCD screen on our gyros? Isn't the screen on a high end radio enough? I think you are missing the point though that THESE are NOT normal piezo gyros. Piezo gyros have some drift problems like the JR units and some others. The SMM circuitry in these gyros are unlike any other in the industry. You may know that but some of us actually forget that fact. Why do you think that most of the top pilots are using Futaba gyros? Their entire gear may be JR or Airtronics or even Futaba...but their gyro most likely will be a Futaba. The technology is not the same so I really can not compare them. I can not say whether the 270hz frame rate is a gimmick or not. The main point is...they work and they work very well. If they didn't none of us would be using them. You see we don't buy into the GY601 because who really wants to spend that kind of dough on this gyro when you can get the same performance from the GY401? Not me! Yeah I think we do need Jim Mahoney to do some comparison tests. But judging from the way the gyro works there will be negligible difference with the DS switch ON or OFF. We have to go by what Futaba tells us. Besides, you would have to be a computer "linked" into the gyro to see if there was any difference.
|
|
|
5150 Member Posts 68 |
11-06-03 02:36 AM - Post#29517
Hey guys! Has anyone ever used any of the Multiplex Digital servos in their heli's? I know my buddies and I use them exclusively in our 1/5th scale cars and we aren't easy on those. They get thrashed around pretty good at 60-70mph and I have yet to have any one of the servo's fail in any way shape or form. They are bullet proof and have huge amounts of torque. Come to think of it I'm also running them in my TXT-1 as well as my offshore boat. And if that isn't a test I don't know what is. That boat is pretty hard on stuff but the same thing. No problems or glitches or anything for the couple of years I've been running them. Here's some of the torque specs for 5 cells: Power mc/V2......135 oz-in/.22 sec with a holding power of 405oz/in Power Speed mc/V2.......108oz-in/.16 sec with a holding power of 324oz-in They are just brutal for power! And those are just the mid-sized servos. Just curious if anyone else had used them for the helis or not. 5150
|
|
|
RC Man1 Full Time Senior Member Posts 2271 |
11-06-03 11:05 AM - Post#29532
I have been trying to find out for some time if Multiplex Digital servos are compatible with CSM or Futaba GY series of gyros. They must not be compatible, as I have never been able to get any positive feedback.
|
|
|
Raptor_in_Sweden Senior Member Posts 136 
|
11-06-03 01:34 PM - Post#29540
I checked with Hitec RCD some time ago about using Hitec digital 5925 servo with high speed data rate from Futaba or CSM Gyros. The service guy stated( in email) that all Hitec digital servos can handle the high speed data rate from modern gyros.
|
|
|
5150 Member Posts 68 |
11-06-03 07:45 PM - Post#29553
I'll have to check on that. When I get a copter I'll look into it. The Multiplex are 100% digital so I'll see. The guys at Multiplex told me that they should be compatible. I'll let you all know what I find. Guess that means I should hurry up and order a new heli then, right?  5150
|
|
|
reddragon Full Time Senior Member Posts 3870
|
11-07-03 03:30 AM - Post#29588
SHHH...(long pause)....do you hear that? Silence. In theory the digital servo should work with the Futaba GY401 gyro. Raptor_In_Sweden stated that Hitec said that the servo could handle the high rate of transmission. But who is willing to try it and see what happens?
|
|
|
Charlie Senior Member Posts 366
|
11-07-03 12:07 PM - Post#29600
Not me! I have been called a lot of things, but ginypig wasn't one of them  .
|
|
|
5150 Member Posts 68 |
11-09-03 07:47 AM - Post#29747
Soon as I get a heli I'm all over trying it. I think they will work great! And I've got enough of them around here! I'll keep all you guys posted when it happens. 5150
|
RC
|
|
|
|
|
|
FusionBB™ Version 2.2 |
©2003-2007 InteractivePHP, Inc.
Execution time: 0.075 seconds. Total Queries: 17 Zlib Compression is on.
All times are (GMT +0000) Greenwich Mean. Current time is 03:46 AM
Top
Execution time: 0.075 seconds. Total Queries: 17 Zlib Compression is on.
All times are (GMT +0000) Greenwich Mean. Current time is 03:46 AM
Top