1 or 2 st. servos

[x120leecraft]

Was wondering if its better to use 1 or 2 servos with 7.5 ob. Using 2 right now but doesnt seem to turn very far like my 3.5. Radio is turned all the way for travel. Or do you need more batt. Using 4 AA now. Have any ideas. Dave

 

[TUNLBOTR]

Was wondering if its better to use 1 or 2 servos with 7.5 ob. Using 2 right now but doesnt seem to turn very far like my 3.5. Radio is turned all the way for travel. Or do you need more batt. Using 4 AA now. Have any ideas. Dave

Dave, Needs more battery, on two servos those AA's are only throwing out 1500 MaH, you could use more voltage for sure.

Randy

 

[x120leecraft]

Was wondering if its better to use 1 or 2 servos with 7.5 ob. Using 2 right now but doesnt seem to turn very far like my 3.5. Radio is turned all the way for travel. Or do you need more batt. Using 4 AA now. Have any ideas. Dave

Dave, Needs more battery, on two servos those AA's are only throwing out 1500 MaH, you could use more voltage for sure.

Randy

Randy how should I change it. What baat. hookup etc. Dave

 

[jydracing]

Hi Dave you need 2 servoes. the 4 AA's is equal to 5 rechargeable. AA Dry cell has 1.5 volts each and a AA rechargeable has 1.2 volts each do not go over 6.0 volts. Sounds like you have the throw turned down on your transmitter. Or you need a longer arm on the servoes. Also look at it this way were the sterring rods hook on the sterring arm on the servo move them as far out as possable and were they hook to the engine move them in as far as possable. that will give the engine a more turning radious. Hope this helps Jimmy

 

[Boris Mazor]

Was wondering if its better to use 1 or 2 servos with 7.5 ob. Using 2 right now but doesnt seem to turn very far like my 3.5. Radio is turned all the way for travel. Or do you need more batt. Using 4 AA now. Have any ideas. Dave

Dave, Needs more battery, on two servos those AA's are only throwing out 1500 MaH, you could use more voltage for sure.

Randy

Randy how should I change it. What baat. hookup etc. Dave

Hi, Dave! This is a common huge mistake to put two servos on one device! Two servo connected to one device will work one against another, because they are not perfectly synchronized and power will be not doubled and battery will drain faster. DO NOT GO OVER 6 VOLT (5 NiCd or 4 AA)

When power of one servo is not enough, you have to use more powerful servo.

The travel of steering related to dimensions of arms on servo and device. If arms the same angle will be the same.

Bigger arm on device make angle smaller. Compare arm dimensions on 3.5 and 7.5 and you will get answer.

Call me if you need more. (901) 682 7436 Boris

 

[jydracing]

Hi Boris not wanting to start a fight here but i have to dissagree with you. I have been running tunnels for 20 years and always run two 1/4 scals servoes on the sterring becouse it does double the tork output. and never had a problem with the battery lasting. Most 7.5 and 11cc tunnels will not turn with one servo. One servo is not strong enough to overcome the tork of the engine in a turn. I have seen many try one servo and what usely happens is when they enter a turn the servo can not move it's full travel even though you are telling it to. then when the hull hooks up in the turn the engine tork lessens and the servo moves the rest of the travel and the boat hooks all the sudden. Than the hull is blamed for the hooking problem when in fact the problem is the builder did not put two servoes to turn the motor. See ya jimmy

 

[Grimracer]

Jimmys right.. I work with an R+D department that has 3 and even 4 servos linked together to fly some of the 40% stuff..

We dont see failures dont come from the lack of synchronization of the servos. Truth is the torque multiplies by a small amount.

ROCK ON

Grim

 

[Scott Wadlow]

Jimmys right.. I work with an R+D department that has 3 and even 4 servos linked together to fly some of the 40% stuff..
We dont see failures dont come from the lack of synchronization of the servos. Truth is the torque multiplies by a small amount.

ROCK ON

Grim

I have a 7.5 tunnel with a CMB and one 1/4 scale swings it around with no problems.

 

[HTV Boats]

I am not going to throw anyone under a bus here as everyone has valid points. Bottom line go with what works for "your hull". Ask others running that application works for them. I have run 7.5 OB's since the 80's on tunnels and V-bottoms. We used to link 2 standard (60oz) servos and it worked. I have seen 2 1/4 scale not linked but one rod pushing and one rod pulling. Technically the sterring bar on the engine was the link. I have seen over 200oz servos that would not turn a hull. Ball park I would say you need 100 oz to turn a .45 OB. I have successfully run a single 3305 Futaba (124oz-6V) but prefer the 3302 with 164oz-6v. Both have metal gears which I recomend highly. Jimmy makes a good point that different hulls have different needs. Use 2 3302's and if it wont turn you may have other issues. Flying trimmed out you may not be able to turn well until the boat sets and then hooks as it all happens too quick. Bear in mind torque is probably rated at the inner holes of the servo horn and as you go out you have a leverage factor reducing torque. Inner radius means less throw. Wider steering bars increase actual torque but less throw again. Better to reduce mechanically than tune it out electronically on your transmitter. Make sure your transmitter has 100% throw to start with.

 

[Grimracer]

Mic.

Servos torque is measured 1" from the center hole.. (Hence 130 inch / oz of torque) this equals holding a 130oz of weight at that distance.

This can be done using a static weight.

Hope this helps

Grim

 

[larcor69]

WOW you guy's are still in the 80's or early 90's with servo development, they make standard size servo's that put out more than 370 oz/in these day's and there fast too!!! look at a JR 9100 T I have 2 of them, here's one on e-bay new for 96.00 9100-T

 

[jydracing]

Hi all the hulls that i have raced was the leecraft 7.5 and 11cc and my Hornets. At racing speeds they need two servoes. I am using the Hitec 1/4 scale metal gear servoes. And a lot of factors do come into play speed, hull, Battery pack, Prop, Stock or mod engine. There are a few servoes that have around 300 inoz of tork But they will not fit in my radio boxes. it is kinda like this what works for me might not work for you. So with that said try one if that does not work add another. See ya Jimmy

 

[Matthew Hughes]

Another benifit is 2 servos is when your tunnel blows off and goes in side ways, there will be a large side load on the motor causeing the plastic servos to strip or break teeth. This is not a problem with metal geared servos but you can still strip the horn.

Mike

 

[Grimracer]

Larcor.. for what its worth..fast servos are not always a good thing in RC boating. (at least to me)

And trust me we are full aware of the size, power and speed of the "new" servos..

Here are the requirements in my book.

Brut Strength

Moderate power

Moderate to slow speed

Dependable

Weight is fully dependant on application

I personally don’t have a use for Digital servos in my boats.. My Helis ya.. my boats no..

Grim

 

[jydracing]

I Tried two of those 100.00 High tork high speed servos BIG MISTAKE. Was going through turn blew boat off when it landed it hit engine first another big mistake ripped out both Metal gear sets then i had a hand full of junk that cost 200.00 I will never do that again. i spend 55.00 ea for Hitec 1/4 scale servos and never took out a set of gears. Look at it this way smaller servoes = smaller gears Bigger servos = Bigger gears.

Also had to slow the servos down turned to fast for the tunnels. They may work great for the hydros and monos But i agree with Grim on the order that i pick servos. See Ya Jimmy

 

[Bill-SOCAL]

I use digital servos whenever possible for these reasons:

1 - I use a Futaba FASST 2.4 GHz radio and to take advantage of the HRS mode requires using digital servos. On the 3PM radio using HRS is the only way to set a failsafe that the radio remembers. And since I know I am going to forget to set the failsafe at least half of the time I turn on, I prefer to use the HRS mode.

2 - Digital servos center better and more accurately than analog servos.

3 - Digital servos have greater holding torque. Even if an analog servo has the same torque rating it cannot maintain that toque as holding torque. Digitals excel in this respect.

Speed is important in airplanes. In boats I actually slow down the steering and sometimes even the throttle servo.

 

[Jcazz]

Hi Guys, I used one Steering servo in my 11cc tunnel, It was a Digital Hitec 333oz, 5995TG, it was overkill but it worked VERY well, and left more room in my radio box than going with two servos....In this day and age you dont have to do 2 steering servos and more...Technology is alot better...Second i use the Nomadio React controller, Best **** controller i have ever seen and owned....2.4ghz, and does more than the Futaba 2.4 fasst system.. and i think its less expensive also, Check out Nomadio...Telementary is also nice...which these guys have yet to catch up on..

 

[larcor69]

yep, That Nomadio is way cool set up!!,

 

[Craig Murphy]

Agree on the Nomadio, combined with a digital servo and you can get some fantastic results... totally tailored steering, throttle, etc.

 

[Eric Bourlet]

Here is where you need to follow the manufactures recommendations. When I raced for B&M Leecraft I ran a single 1/4 scale servo and won many races and series championships. When Vans picked me up Carl's instructions said to use two standard size servos so that is what I did in the Shaman and that boat wins races and championships too. Both setups will work but it is best to take advantage of the development the designer put into the hull you are running. Yes they make standard size servos that have the torque in a single servo but remember the surface area of the splined shaft is smaller than either a 1/4 scale servo or two standard size servos. The reason that is important in a tunnel is the tremendous load that you will put on the output shaft in the event of a blow over and side loading the lower unit. I would say that two 1/4 scale servos is over kill in either situation, but if that is what the manufacturer recommends then use it.