400 servo question

[treaves]

I've seen several people recommend HS65MG as replacements for the stock servoes, with one going with HS5065MG. I have a couple of questions about this:

*) I understand the 5065 is digital, but what does that mean (in this context)? Why is one better than the other?

*) are these drop-in replacements? Or are modifications required?

*) Would all the factory servos be replaced with this, or are different servoes better for different positions?

Thanks (yes, I'm new to this).

[fogger]

Check out this thread, specifically post #9 by me :)

http://helifreak.com/showthread.php?t=56113

-Fog

[treaves]

O.K., but that doesn't answer any of my questions. You state you went with a different servo for one of them (but not why), you state you had to do some dremmel work (but not why - where both servos too big, the combination of those two?), and it doesn't mention anything about the difference between the 'analog' and 'digital' version of the servos.

[fogger]

Ok, let me clarify then.

1. The digitals are faster, have more torque and arrive at their max torque faster than standards. For a blade 400 IMO this is overkill and not worth the extra money. But that's up to you. Do a search for digital servos for plenty of information on this site and others on the technical differences.

2. They are not drop-in, this is why I modified the frame to allow them to fit. The body of the HS65MG's are just a hair longer in the direction between the two mounting holes. This meant that I had to remove material from the frame opening as I described. I didn't have time to take pics, sorry. But the two servos behind the main shaft go into the same opening. That opening needs to be widened slightly by removing material on the side closer to the main shaft. Then the servos will fit, but you still can't just slide them in (unless you take a lot of material out, which could compromise the mounting holes). I found it necessary to remove the back plate and move the servo lead strain relief out of the way to slide them in, then I screwed them back together.

3. I used the new HS56MG servos in all 3 CCPM positions, elevator, aileron, and pitch. Then I used a new Futaba S9650 digital tail servo on the tail (rudder) position.

Hope that helps man :)

-Fog

[fogger]

I retract my suggestion. Treaves felt it was too harsh. I apologise.

-Fog

[Wolfpackin]

Fogger,

From what I understand the stock B400 servos are digital but they don't accept the digital pulse from the gyro. And that's not an issue with the cyclic servos.

My question is how do the non-digital HS65 and the digital HS5065 compare in speed to the stock servos?

Also, the Spektrum SP75's (DSP?) are a direct fit in the B400 and are digital that will accept the gyro's pulse.
Do you know how these compare in speed to the others?

[sokal]

iv installed the jr ds285 they fit fine no mods just need washers or a screw with a bigger head. hey seem to work great, just got done rigging the head to them. flew a bit work great waiting on the 401 and the 3400g

[fogger]

I can't even find the specs on the ds75. The non "digital" version (I doubt the DS75 is a true digital servo) are:

E-fliteEFLRS75
Type: Sub-Micro
Torque: 17.2 oz/in @ 4.8V
Speed: .12 sec/60 deg @ 4.8V (highly doubtful they're even this fast)
Connector Type: Universal "S" Type
Dimensions: .90 x .45 x .94 in
Weight: .26 oz

HS65MG:
Motor Type: 3 Pole Neodynium Magnet
Bearing Type: Top Ball Bearing
Torque 4.8V/6.0V: 25/31 oz-in (1.8/2.2 kg-cm)
Speed 4.8V/6.0V: 0.14/0.11 second
Size: 0.9" x 0.5" x 0.9" (24mm x 12mm x 24mm)
Weight: 0.39 oz (11.2 g)

DSP75
http://www.spektrumrc.com/Images/px-clear.gifType programmable Digital Sub Micro
http://www.spektrumrc.com/Images/px-clear.gifTorque:19.0 oz/in @ 4.8vhttp://www.spektrumrc.com/Images/px-clear.gif
Speed:.11 sec/60° @ 4.8vhttp://www.spektrumrc.com/Images/px-clear.gif
Dimensions (WxLxH):.90x.45x.94” (23x12x24mm)http://www.spektrumrc.com/Images/px-clear.gif
Weight:.26oz. (7.5g)http://www.spektrumrc.com/Images/px-clear.gif
Motor Type:Coreless
http://www.spektrumrc.com/Images/px-clear.gifConnector Type:Universal

The HS65's are stronger and therefore center better and will overall respond more precisely than the stock servos. Also the metal gears are far more robust. I had spektrum S75's (from the dx6 combo) on my trex450 for a time and if you look at them sideways they strip. It's a joke. I am sure the spektrum and e-flight servos are essentially the same servo with maybe slight differences.

Think about it, you are comparing an el-cheapo $13 servo to a quality $36 servo... Sometimes you have to just use reason and ignore the inflated claims of budget oriented mfr's like e-flight.

Personally, I would not use *75 servos on anything but a small foamie plane.

-Fog

[fogger]

I really like the DS285's also, they worked great on my 450. But, they are also extremely easy to strip. It's just silly. I was ok with that because I was to the point where I was hardly ever crashing when I ran them.

However, on a newbies helicopter the last thing you want to have to do is tear out 2-3 ccpm servos and put in new gearsets every time you crash, and you will end up having to do this with the ds285's, I'm sorry to say. But the new metal gear version may be worth a look. At my LHS they were $40 a pop, so we went with the hs65's. Either one would be a good choice.

-Fog

[Wolfpackin]

Fog,

Excellent comparative information and interesting as well. Thanks.

So do you think using the HS65MG's for cyclic and maybe the HS5065MG for the tail would be a good setup?
I don't think I want to spend the money on something like the JR 3400 for the tail at this point.
I'm not familiar with the Futaba S9650. How does that fit on the B400?

Thanks again.

[fogger]

I have no experience with the new digital 5065. It may be fast enough for good quality tail duty. Certainly it will be better than the stock servo, of that I have no doubt. The s9650 was a bit of a squeeze in the 400 but it fits. Guys here is the thing, for just hovering a mediocre tail servo is ok. Once you progress beyond that it becomes important to have a very solidly performing tail. That means a good quality fast digital tail servo. It's just the way it is. Otherwise you will fight for tail control and crash more often as a result.

-Fog

[Wolfpackin]

7.5 Gram DS75 Digital Sub-Micro Servo


Key Features

Digital amplifier for improved precision and holding torque
Increased travel angle output for more available throw
Improved precision gear train for reduced gear free-play
Finer spline output shaft (compatible with S60 servo arms) for improved setup tuning and precision
Includes complete mounting hardware and an assortment of servo arms, including an extra-long 3D arm for extreme control throws
Universal connector compatible with major brand receivers
Weighs just .26 oz (7.5 g) with servo arm and servo leadOverview

Perfect for electric slow flyer, park flyer and high-performance 3D models, micro and mini electric helicopters, hand-launch gliders & 1/18 on- and off-road vehicles
Specs

Type Digital Sub-Micro
Dimensions (WxLxH):.45 x .90 x .94 in (12 x 23 x 24mm)
Weight:.26 oz (7.5 g)
Motor Type:Coreless
Connector Type:Universal
Application:Electric slow flyer to park flyer 3D airplanes, micro to mini electric helicopters and 1/18th scale onroad and offroad vehicles

No numbers for speed/torque :(

[fogger]

I can almost guarantee the numbers are exactly the same as the non-digital version. The digital version will theoretically achieve it's max torque number faster, but they in all probability have the same gears, the same motor, the same case. So the only delta is the electronics.

I mis-spoke in my response to the question as to the delta between digital and non-digital servos. All other things being equal, a digital servo does not have more torque than it's non-digital equivalent servo. Sorry if that statement was mis-leading. They do hold better in general, due to a more constant signal being sent to drive to the motor. They are faster to respond to input, but they do not have a higher maximum rotational speed. That said, would you expect a digital servo to hold as well as a non digital servo with double the torque? (this is a rhetorical question) In my experience, no.

Here is the somewhat technical low-down.

http://www.futaba-rc.com/servos/digitalservos.pdf

-Fog

[carlo_the_wonder_frog]

The biggest problem with the DS75 and E-Flite 75 servos is not speed or torque, its the fact that they do not center worth a darn and have too much slop in them. You will be chasing a perfect trim all the time. Any plastic geared servo on a heli will break the gear sets if the blades come in contact with terra firma. HS65MG servos are tried and true on higher performance helis already, and they will fit the 400, buy them once and never worry about them again. The high end digital servos ( 9650, 9257, 3400G, etc) are going to give you superior performance above all others. Once again buy once and not have to worry anymore.

I am waiting on the blade 400's to start hitting E-Bay used without the radios. Should be much cheaper to buy that way.

[widower]

The truth about digital servos (and as outlined in futaba's pdf) is that it will use full speed to get to the stop point. An analog servo slows down as it gets closer to the stop point. If you want the gory details, I can get more specific.

I've had 1 small crash (first flight). It stripped the elevator servo and one of the FETs that drive the servo motor burned out. So I replaced it with my tail servo and put a S3154 in its place. It was the only thing available at the local hobby store. I'm still running it in analog mode (updates sent to the servo are slower) and all is well about 15 battery packs later. Once the weather warms up, I'll change the gyro to digital mode and start dialing up different throttle and pitch curves. For now, the only changes I've done to the radio is increase flight timer to 6min (actually get 9min on my 2200mAh pack) and turned on expos at 20%.

[CoronaL]

replaced my 3 cyclics with HS65MG's
the front servo went in fine, but the two that are stacked near the main shaft I had to clearence the frame a bit. All in all not a bad mod, but still a bit unnerviing.
I'm waiting on my new X9303 to get everything setup, so I don't have to do it twice.

[skigolfmike]

I stripped the aileron servo. I did have a blade strike though. Looks like I bent the feathering shaft too. I'll go through the head to be safe and look at the fly bar, grips and main-shaft too. Probably wouldn't hurt to take a good look at the tail rotor.

For now, I'll probably get a DSP75 for the tail rotor and move the rudder servo to the aileron servo spot. I will take a look at the Hitec HS65MGs and the 9650 for the future though.

The weird part yesterday was I had the heli shut off after a landing. I thought it was weird at the time, but it came back alive on the bench, so I gave it another shot. At that point it I thought it got really squirrelly and I should have quit when I was ahead, but I kept at it and had the blade strike. What was really weird was when I changed the TX model to my CX2, it lost the program and reset everything to the default settings. I haven't looked at the Blade 400 prog. yet, but ya gotta wonder. The TX bats were getting low too, so I wonder if that had anything to do with it.

I flew a Kalt 30 back in the early 90s, I don't remember it being anywhere near as sensitive as the B400 seems to be. (I actually flew that heli fairly well) I'm practicing a lot on a sim and not having trouble hovering, (tail or nose in) so I'm just wondering if the smaller helis are just that much more unstable?

[widower]

Knock on wood, I've only had one crash and sure enough, stripped & killed the elevator servo as well. I replaced the tail servo with a futaba 3154 (I believe) and moved the orig to the elevator position.

From what I've seen, the HS65MG require filing and stuff to make them fit. It appears the DS285MG is an easier replacement. I have mine on order.

Regarding your tx programming, I believe your settings are saved to internal flash upon changing or powering down. If your tx batteries are low, it's possible to corrupt the internal flash. There is an alarm you can set for low tx batt in the dx6.

I flew a Shuttle 30 in the mid 80s, and I fully agree with the sensitivity. In those days, the dihedral was larger, CG was lower and there was no such thing as 3D flying. The b400 is definitely touchier. It took me quite a few battery packs to feel really comfortable with tail and side in hover. I need a bigger basement to get the gumption to try nose in. It was +1C here on Sunday so I managed to fly 2 batt packs and I told myself it was time to start doing more than just hovering. I'll tell you, this little machine really moves. Once I was comfortable with flying easy fig 8s, I started doing some nose in hovering. Once my heart slowed down, I realized the sim helped out a bunch. Nose in is much easier outside. Boy the b400 sure looks small when you are doing nose in. I also found that man-handling the heli when I'm uncomfortable with speed or height reacts the same as on the sim so that was a big help. I'm using g35 with the trex450 model and it sure helped. I'm still not ready for nose in in my basement. One thing that I did notice is there were times when it was tough to control altitude. The heli would at times drop faster than I expected and take longer to react versus the sim. Also, beware, if the heli gets behind you, don't look over your shoulder. Instead, turn and face the heli because that's what you're use to in the sim.

[fogger]

The new smaller helis are far squirlier than the old 30 size machines. Headspeeds are much higher, mass is quite a bit lower. The b400 in stock form is especially bad because it's servos are slow and weak, and this introduces control input lag and thus some amount of hysteresis... You wind up not only chasing the natural drift but also you end up over-correcting because the control inputs don't make an effect happen fast enough...

-Fog

[skigolfmike]

When I get a chance I'll look through the TX Manual to see about setting the alarm with the TX. Chances are pretty good that the battery voltage got low enough to "Boot" the system and wipe out the memory. I've been using the TX quite a bit on a sim and with the CX2 and the voltage was down to 5.0, 4.9.

The LHS had the E-Flite servos, DS75H, and gear sets. I also got a Spectrum DSP75 to try on the tail. I will consider going another route in the future (HS65MG/3153MG) combo. Maybe 3153MGs all around. We'll see.

Yesterday was not a good day for helis at our house. First my daughters boyfriend broke the blades off his Lama R22, then he busted the top of the inner shaft. Then I had the blade strike with the B400 and lastly my boy flew the CX2 under a table and climbed into the bottom of the table. Before we could check the heli, he took off again and it shed a blade. So, we took 3 helis out of service in one day.:roll:

[widower]

Wow. From what I've seen, the ds75h isn't in stock anywhere. I wonder if your LHS got them from a new b400 kit where someone didn't want the stock servos. From all the googling I've done regarding the ds75h, I think they are just a dsp75 programed to 'helicopter'. And the cheaper price because of quantity. But this is only a guess.

3 helis in one day hurts.

[skigolfmike]

The LHS had them (DS75H) new in the pack. I don't think the Spektrum DSP75 is the same. Same case, gears and motor, but different electronics. I doubt you can put an E-Flite DS75H on a Spektrum digital servo programmer and program it. My guess is it's similar, but not the same.

Followup: I just read the B400 manual and it states that the Spektrum DSP60, DSP75 and JR3400G can all be used in digital mode with the G110 gyro while the E-Flite DS75H cannot. The servos have to be different.

Turned out to be a crashfest yesterday. Hey, I only crashed one heli though. The CX2 I have parts for and is an easy fix. Just replace a lower blade. The B400 stripped a servo and bent the feathering shaft for sure. I also have a spare flybar and main shaft if needed. I don't have to fix the Lama, but my daughters boyfriend has to mail order parts to fix it. I have penty of parts to fix both my helis.:lol:

The TX manual says there is an alarm built in at 4.3 volts, so I shouldn't have had the TX problem or lost memory like that. However, it was only 35 degrees outside, so maybe it had something to do with the combination of cold and batteries that were close to done. it was still wierd though.