qspilotcmh

I have an Aeroworks ProX260 60 size profile with a DLE20.

AW calls for a Hitec 65MG for the throttle. I have 14 flights on mine with no issues. I am concerned about the vibration effecting the servo over the long term.

What do you think?

I need some nose weight and have thought about installing a Hitec 85MG.

Thanks

w8ye

My Feedback: (16)

I would think that the long term prognosis of a HS-65 would not be good in a profile gas plane?

I would go about the change over to the HS-85MG

Tired Old Man

My Feedback: (1)

I'm surprised the 65 has lasted this long. MG or not, it does not have the strength in the gear train to hold up.

qspilotcmh

Would a Hitec HS85MG be sufficient? I would hate to put a standard size servo on a small profile.

thanks

Tired Old Man

My Feedback: (1)

225mg is the smallest servo I would consider using on a gas engine. No, they are not cheap, but they are a lot cheaper than having a dead throttle on a profile with a terrible glide ratio.

qspilotcmh

Actually the 225mg is $5 cheaper than an HS85mg. I have 3 spare 225MG so maybe I will go that route instead of buying a 85MG. I was thinking about the 85MG because someone posted it has a shock protected POT. I'm not sure if the 225MG does as well.

Chris

w8ye

My Feedback: (16)

+

airraptor

My Feedback: (66)

I do not own a gas engine but i dont see it any differently than a big single four stroke. I have used many of those servos mentioned.

If you have installed the servos with the stock mounting rubber mounts the HS65 MG will last. I Use the HS-65HB (karbonite gears) on many applications. I have also crashed several planes with these servos and the gear train holds up very well so much so that the servo arm or the servo case will break first. I even had one hard mounted to the mount box on my Revolver and the firewall broke loose from the mount box. the Little HS-65 HB held the Saito 125 on the plane and the engine stayed running between full and half throttle as the engine moved around. I had a camera mounted on the plane and it recored this event.

You will be better off with the HS65 or HS 85 over the HS225 standard servo. The 225 have serveral issues with the pots in them and the overall centering. The HS5245 same size as the 225 but digital works much better and a very good servo but is 50 dollars.

Now i can see the little servos having a problem if tyou have the carb spring on the engine as i am sure they are stiff. When i get my gas engines i will remove those springs and run HS65 servos even if on larger engines like the 55. I always like to use light equipment. why put a 2 ounce 8711 servo on throttle when a small .5 servo will work. I dont skimp either on questionable items.

So i say keep using that 65 servo. Make sure it isnt touching the airframe and the servo gromits(sp) are installed correctly. No metal to metal contact no carb spring and should be fine.

If need more nose weight try to move your battery around. If can not do that then look at moving the tail servos foward by 4-6" that should give you about 2-3 more ounce in the nose with no more weight added to the plane.

a1pcfixer

My Feedback: (7)

That's one of the early mistakes flyers make when moving from glow up to gas, in that what's 'good enough' for glow must be the same for gas, which all too often is NOT the case. That carb return spring serves a very important & needed function. If/when your throttle linkage fails (breaks/falls off/etc) then that return spring will at the very least, return your gasser to an idle and NOT WOT!

That return spring takes very, very little effort to overcome, and any decent quality servo can easily overcome such with no effort.
Leave that throttle return spring in place & let it do it's job!

The Hitec HS85MG is by far, a better servo than the HS65MG and much preferred by those 3D flyers of profiles.

qspilotcmh

Thanks all! Just ordered a 85MG. Since I need a little weight on the nose I figure it a good upgrade.

Tired Old Man

My Feedback: (1)

I'm going to be a little more direct. The first sentence in your post illustrates why you are not qualified to make an assessment. Once you do own and use gas engines you will see things quite differently than you do now.

In the last 6 months I have replaced 5 high end throttle servos in aircraft owned and flown by other people for various reasons, usually set up. A less capable servo is less tolerant of set up errors, and cannot handle the shock loads of a lower frequency combustion impulse.

Some of us are extremely cognizant of how long small servos can and will hold up, along with their failure modes, when used on gas engines. The small Hitec and other similar servos from other makers were designed and intended for electric models. Those choosing to use them for internal combustion powered aircraft are only accellerating the expiration date of the aircraft.

dogshome

Direct it is then!

I need to fit 10 servos in a 70" Warbird. Got a 15cc Petrol engine. I do not intend fitting that weight of standard servos as it will make it a pig to land.

So, the throttle stands out as one to make smaller. It has little load (I cut the tail off the return spring) and will be mounted away from the engine, connected via a soft plastic snake. I have an electronic kill switch in case of failure. Can't see any problems with that

Flaps are the next victim for 'undersize' 'girlie' 'electric' servos. They are thin split ones and to be fair, aren't big enough to do a great deal.

Finally, since I like dual elevator servos, they might also be of the 'not-a-mans-servo' type mounted at the back (away from the satanic vibrator) and can't see any problem with that also.


Please feel free to alternate or be direct as applicable [&:]


P.S. My FS180 glow on an 18*8 shakes like a goodun. Little RCGF 15cc petrol is like a toy sewing machine on a 13*8. I don't imagine a DL20 on a 15" prop is going to shake like Gadaffi on a pickup heading south either!

airraptor

My Feedback: (66)

TOM and APC yes i dont own a gas yet but i still do not see your logic.

APC why dont GLOW engine have return springs. There have been many planes that have lost a throttle cable, push rod, pull pull set up and others that have failed.

I can see most gas engines as larger than most glow engines so i could see more impulse's getting to the servo by the engine moving enough to cause the push rod to pull or push on the servo. This could cause problems but if its correctly installed then i still dont se a problem but i dont as you say have any experience with them.
I do mount all my servo's close to the engine if there is room. so maybe with the short push rod length there isnt as much flex in the fuselage to cause problems.

I have two projects that i will have a DLE 30 or the Mintor 33 on and a DA-85 on the other. I will run the 65 on the 30cc and a 85 on the 85cc. That is the plane anyway.

TOM i do know you have a lot of experience on these engines and do listen just that this one seems like over kill.

I will say also that any of the smaller Hitec servos with plastic gears and junk. I have about 11-12 HS 81's that have been converted to metal gear because the plastic ones strip very easily. I had two of these 81's strip just by pluging them in to the reciever and truning them on with no horn hooked up.

Anyway you will be happy with the HS85 but you say you need a little more nose weight but will .2 ounces really make a difference on that plane? Do you need even more nose weight?

MetallicaJunkie

i wouldnt do it.... youre better off with a standard servo


*edit you can always use a 225 if yur 85 fails..... just make sure not to overdrive the servo and it will last a lot longer... when i was new i used to dial the endpoint to get as much WOT as i could causing the servo to work harder than necessary.... now i have learned that is not necessary, ive read that between 75 and 100% makes no difference in rpm... so i set it at approximately 85 to be sure

apalsson

My Feedback: (1)

Where weight is a consideration, the Hitec 5245MG servo is a good alternative.
In fact, I have on previous occasions used that servo in 50cc class planes because I had a few lying around.
On 6V, these servos have torque of 5.5Kg/cm (76oz/in) and speed of 0.12sec

Tired Old Man

My Feedback: (1)

People that clip or remove throttle return springs only illustrate their ignorance of the what, how, and why of the way things work. If you are using a servo that does not have the ability to deal with a throttle return spring you are using the wrong servo. Period.

I've been flying and working with gas engines using mini servos on throttles for 6 years now. Thousands of them, and I know what will and won't work. If you do everything right, a Futaba 3102 will get the job done. Bear in mind there are no reserves in strength.

acerc

A plane will fly without ailerons, rudder or elevator depending on type of craft. But none will get off the ground without throttle. Not counting control line, pylon etc. My weakest throttle servo is a HS645MG.So, I can rest assured that when I move that stick so will the throttle. And the throttle return spring is where it belong's-On the job!

airraptor

My Feedback: (66)

TOM can you go more into why gas engines need a throttle spring to run? not trying to be a jerk or anything just want to know why?

metal junkie you should have your servos set up to run atleast 100% all the time. If have to much throw then move in on the servo or out on the surface or the throttle arm.

You have some many steps (1024/2048 and so on) that the servo will move if you have a lower end point your not using all the servo has.


ACER that 5645 isnt enough i think you should run a HS M7990TH digital mega torque just to make sure you have enough lol

acerc

Yea I know, overkill. I bought a box of the,40 @ $10 a piece,  from a fella at my field. So thats why. I know,  proper set up does not  require anywhere near that. But when you have them

Tired Old Man

My Feedback: (1)

The throttle return spring serves a couple of important functions. The most obvious is what it does in the event of a linkage failure. It becomes an auto stop for the engine since it completely closes the throttle if, and I say again if, the user removed the idle stop screw like they should have.

The second is a bit more subtle. It maintains the centering of the throttle plate and absorbs much of the vibration load that courses through a carb, letting the throttle mechanism and carb venturi remain functional to a ripe old age.

A bit more about that Futaba 3102 since there's a couple things I forgot to mention. They will work with the following caveats. Never bump the linkage if the servo is powered up. Immediate gear strip. Never over drive one or let it bind or slam against a hard stop. Immediate gear strip. It has to be installed in a manner that permits the servo to match the engine almost exactly in vibration frequency and amplitude with the engine . That includes the linkage. If not, sooner or later gear strip. It has limits for what it can withstand, just as servos made for electrics do. I would not even consider an s3102 for anything larger than a well made 28cc engine.

airraptor

My Feedback: (66)

Thanks TOM I wasnt aware of the spring doing so much. I just assumed it was there since the chainsaw/leaf blower type engines.

Ernie Misner

Okay, about the HS 85mg servo: I about went crazy trying to find the info on where it states the 85 servo has a shock isolated pot...... even checked the specs at Servo City and couldn't find it. But I KNEW I had seen that many times so I went to the box of one of my spare 85's and there it is right on the box..... Shock protected pot and aluminum output gear.

In the profile forum there is a lot of info on throttle servos becuase they use such a short and direct link to the carb and take a huge amount of abuse. For some reason the 65's, 80, 81, 82, etc. all fail quickly on a profile plane but the 85's just keep on going and going.

Like I said, my personal experience with the profiles have proven this to me also. Most of the lesser servos begin causing dead sticks when they don't center correctly anymore around idle so watch out for that and if one sticks at full throttle like my HS 82 did you will KNOW you have a serious problem.

Granted I've only talked about fairly small and lightweight servos here because that's what is required on the profiles I usually fly.

Thanks,

Ernie

mike31

My Feedback: (67)

Use elastic thread as in pull pull if you can. Will absorb vibrations. If the carb has a return spring only one thread is needed. It's a ballancing act.

airraptor

My Feedback: (66)

Ernie i used to live in tacoma work out at the McChord AFB.
Ernie i used the HS65 mounted very close to the engine with very short push rods. Most are 1-5 " in length. i have never had a servo fail when mounted like this. I wonder what is so different from my use to yours? I do think that maybe since my firewall setup are more ridge than the Profile planes that allow more vibrations to get to the servo?

For the gas engines i can see them burning out if the carb requires 10-15 ounces of torque to hold them open and the servo is only 25 ounces it will be under constant load and burn up.

dogshome

That's why I only cut the tail off and do not remove the spring.


I'll let you know how it goes - my engine is only 15cc and I otherwise have a big bulk of servos to fit. On my 50cc Yak strong servos are a must - large control surfaces, wild manouvres and lots of vibration. Note that I wouldn't bother fitting a mini servo to a throttle on a 26 or 50cc plane as it makes no difference in weight. With the new small engines and in a small multi-function airframe (warbird):- I think it is worth it.

I'll be posting back on here if I'm wrong and the servo on the throttle fails - no point posting anything other than the truth.