I've used the futaba 3151, digital servos on my throttles forever and never have had a problem... http://www3.towerhobbies.com/cgi-bin...?&I=LXFKZ8&P=0

these have better specs...
http://www3.towerhobbies.com/cgi-bin...?&I=LXPHD2&P=0

You want a good inexpensive servo to put in your plane... get some Power HD-9150's from TBM. $33.00 each, with 220oz of torque, digitals. (not for throttle)

Here ya go Eric. Great cheap fast servo. Also it's metal geared so it will be safe.

http://www3.towerhobbies.com/cgi-bin...&I=LXN667&P=ML

Thanks guys for the help.

I like the 7955 too.

I have yet to loose a servo on the throttle on any of my gas or glow planes due to vibration, unless the engine was mounted on rubber or comes loose the servo is going to move just as much as the engine will and if the end points are adjusted correctly theres no pressure at either end point there shouldn't be any issues. I keep my throttle servo as close as possible to the carb. I do agree that a digital MG servo would be a good investment for obvious reasons. But 333 oz of torque is not only overkill it also adds more weight to the plane. Whats next a sailwench servo ?????

It it's around 2 ounces and in a standard servo package, I'll take all the torque I can get. Got a link to that sailwench servo?

The Hitec 7955tg list its stall torque or holding torque, the true torque as tested by TBM is only 248oz/in. Thats why I would just go with the HD-9150's they list 220oz/in, and put out 224oz/in More bang for your buck![8D]

I would think it would be hard to strip a servo from vibrations... when I first started with gassers I ran regular Futaba 3004 servos on my throttles and they did the job.

It's not so much about stripping the gears, it's about the electronics overheating, trying to correct the servo movement caused by the engine's vibrations. So a poorly setup throttle link can even bring a 333oz servo to its knees.

If a person can be so bad as to mess up a 333oz servo from setting it up wrong on the throttle he/she shouldn't be tinkering with large scale planes...

But it happens in real life I've seen people complaining about the horrible Hitec servos and after some investigation it seemed they were using them on control surfaces w/ big hinge gaps and w/o hinge tape on their fast planes.

I ran my new DL50 for two hrs and I still had 500mAh left in a 1450mAh battery. Is this cause I kept it under 2500rpm and the ignition will draw more at higher rpm's? By the way- engine ran flawlessly. First gasser!

Thanks

Yes more rpm = more current draw.
My 1100mah A123's are good for approx. 115 minutes 3D flight.

Thats what I figured, but wasn't sure. Thanks

My 333 oz throttles are setup pretty well.

Figure about 400-500 mAh per wot running hour on a 4.8v single plug ignition. Most people waaay over battery their ignition systems.

Yes 100% agree. Also Rx. A 2300mah 2S1P A123 lasts me 5 14 minute flights w/ 1 flight to spare on a 30% plane w/ 5x 7955TG, a 5245MG on the throttle and HS81 choke. These batteries can be charged at 4A w/ a heavy duty servo wire, so a 10 minute charge adds another 2 flights. I rarely do more than 5 flights anyway. Many use over 4 Amps in their 30% planes. Power boxes, balancers etc, the more you add the more can fail.

Yeh, I do read a lot of people using 2700mAh batteries. Thanks T.O.M.

I am running a 4.8 2500mAh battery for the engine and 6..0 2500mAh for the servos. And these are just NI-MH batterys I should be just fine right? I bought these for this plane brand new so I hope they wil be okay???

Massive overkill for the ignition. 1,000 mAh would have been plenty.

Something wrong with the guy only getting 5 flights on the 2,300 A123. Should be quite a bit more than that. I can, and generally do, more than that with a 1,000 mAh 4.8v nicad on a 50cc single. Using 70% as an A123 battery cut off point, or roughly 1,600 mAh, averaging 450 mAh/ignition hour, you should be getting close to 3 hours (lots of fudge factor) of ignition running time. Yes, I use them too and know that as the voltage drops the discharge rate increases. Are you running straight battery to the ignition? If so you're wasting a lot of flight time to heat discharged from excess voltage.

The flight battery is dependant on the servos and linkage installation. A 6v will run down faster than a 4.8 but you lose servo speed and torque. I would make it a point to field check that battery every couple of flights and recharge when the battery drops down to nominal capacity. Especially if you're using a JR 2.4 system, the "brownout" king.

Why do you say over killl? Because mAh is only the length of battery time will last right?? I have been running the 6 volt batterys in all of my other planes and not one problem. I run spektrum DX6i.

Well what you shoot for is the Rx and ignition batteries lasting the same amount of time. 2500mah on the Rx will be good for approx. max 90 minutes of flight time, 90 minutes ignition time consumes approx. .057 watts/minute. That would make 1A at 4.8 volts, 0.8A at 6 volts (2S1P A123 w/ rectifying diode). AA size NiMH batteries of any capacity all share about the same weight, so you could look for a solution w/ a smaller size so less weight. If you wanna use NiMH batteries, size 2/3AA would be your best bet. You would save about 35 grams/little over 1oz only.

http://www.powerstream.com/Size.htm

What brand and model cell are they? NiMh are awesome IF you know what cells to use. My fav on RX (50cc 3D aerobat) are Elite 2000 and 1950 FAUP both 5-cell. Fly about 6x10 minute flights flights with some capacity left at the end of the day. The ignition are Elite 1500 4-cell. Barely dent it. Maybe 600 mah for 6x10 minute flights.

By overkill I meant you have a lot more than you needed for a days flying. I don't use batteries that large on twins. 2,000 mAh at 4.8v provides two continuous hours running with a little to spare on a twin.

People buy more battery in cost and weight than they need because they do not understand how an ignition works. More is not always better, 6v is not optimum for a 4.8v circuit, and having more generally costs and weighs more. No big deal if that's what you seek but many are looking for the cheapest an most efficient way.

I think that depends on what voltage you are useing dont you?
I have used more standard servos for the throttle than I care to remember and never once had one fail, like you said it all depends on how well you set your planes up.


Hey Joe here ya go, its a little slow but it has plenty of power http://www3.towerhobbies.com/cgi-bin...?&I=LXE530&P=0

Any standard 50 oz in servo should work just fine on a throttle. If it happens to be a digital/coreless and metal geared even better. No need for more torque than 50 oz in but the better servos usually have greater.