Servo Torque

[TomGracey]

What would the safe minimum oz. of servo torque in a 12lb 48 inch Classic Thunderboat

 

[Ray Sametz]

100 oz min.

 

[FloridaScaleBoater]

I went old school 1/4 scale. Futaba S134MG

 

[Eddie t]

200oz and up would be safe

 

[Hydro Junkie]

Any of the above answers CAN be correct. It depends as much on how much drag your linkage has as the size of the boat. I tried to use a 80 inoz S3305 servo for the rudder on my 2000 Elam, only to discover it wouldn't turn at over half throttle. What I discovered is part of the linkage was a heavy cast piece of aluminum that slid over nylon inserts. To get the boat to turn, I had to change out the S3305 for a 300 inoz S9156 digital servo. Had there been less drag, the S3305 probably would have worked fine.
With that said, I would look at a 150 inoz or higher torque servo due to the size of your boat and the fact you're going to be using a larger rudder.
Let the "flaming" begin

 

[Grimracer]

just some simple info..

Grim

 

[Hydro Junkie]

I like it, almost like comparing a servo and arm to a torque wrench.

 

[Ron Olson]

Mike, I don't know what you know about this. In the US we're used to oz./in. but now I see more servos coming out using kg instead. Is there a way to convert oz./in. easily to kg?

 

[Mike Starrett]

Just google it. It will pop up a converter.

 

[Grimracer]

I have Smart Tools Unit Converter on my phone as well as using Google some times. Its just nice if I am out to the pond or flying site and have limited access.

Grim

 

[Hydro Junkie]

I was confused by the comparison chart due to the units used as well. Once I found out what the units were, the rest was easy.

 

[Greg Wannamaker]

Great tech lesson Grim, my rule of thumb for servo power is don't cheap out now or go skinny on the torque, buy the best servos you can, you have invested considerable time and money in your water sled, opening a smoking radio box or picking up pieces on the beach are sad days and you definitely don't want to be explaining yourself to a racing buddy as to why you just wrecked his sled too!

 

[Hydro Junkie]

Greg, truer words were never typed.

 

[Mark Anderson]

Hitech 645 on 6.6v would be my go to servo for that application. Actually most steering applications for inboard. Tom, I know that you are old timer too. Remember when an S7 was as good as it got with a whopping 42 ounce inches? We used to steer 20 pound scale boats with them all the time back in the day. With proper linkage geometry you will be fine with 100ozin servo.

 

[Daniel's Racing]

Hitec 645 are not what they once were. Total junk now. Not that they ever impressed me but they used to work for a while.
Forget anything analogue. Like running a FM radio. DATED !!!!

You aren't kidding. Spend the lousy $90 and put in a decent servo. Buy once cry once and not because of the crashed boat.

 

[Mark Anderson]

I have well over 50 645s in service. Several in the last 2 years, a lot with many years of heavy use. Never a failure. I must be lucky.

 

[Mike Hughes]

Same here. Its been my go to main servo for years.
Mike

 

[Shannon Muth]

The 645s were the only servo I used for rudder in Nitro boats and I never had an issue with ONE! IMHO this servo will not steer today's heavy gas boats at the speeds we're achieving. I have replaced all of my analog servos to digital and the digital replacement for the 645 is only used for throttle. All of my steering servos are Savox or Hitec 300 plus oz inch torque.

 

[dean werges]

just some simple info..

Grim

great video