Servo Propulsion - HELP

[Norway2112]

I just converted a simple servo into a drive motor by stripping it of all the gears and such for the Lindberg tug. This is how the tug came out of the box years ago, with a servo converted into a motor. Apparently the servo they used for the conversion wasn't like the one I used because my tug barely moves along. I used a Futaba S3003.

QUESTION: What servo should I use for this application so that I have enough rpm to get the boat moving at a realistic pace like originally did. Before it made a decent wake and even could move around a 41 lbs battleship, slowly but it did the job. Thanks!

Phillip

[steveciambrone]

should be the same motor. Lindberg just used a standard servo similar to the S3003. Did you use Nicads or dry cells? Dry cells or 5 Nicads/NIMHD will give you 6 volts. Same Propeller? check for binding. Transmitter trim?

Steve

[Brooks]

After you have relieved any binding, and checked the Tx trim, per Steve's suggestion:

The potentiometer will affect servo speed in some brands. Have you tried adjusting the pot by hand while sending the "go forward" signal to the sevo with the Tx? Pot position will affect sensitivity to neutral; be sure your manual efforts don't leave you with only one direction of servo rotation before you close it all back up.

Did you notice any slowness in the servo before dismantling it? Some are just defective, alas.

A squirt of wd-40 may clean the motor of gunk, but I'd save this as a last ditch resusitation attempt, in case any of the electronics are allergic to oil/solvent (should not be so, but you never know). Do this with the servo out of the boat, of course.

[patmat2350]

Another option- more power. As long as you don't stall the motor, the servo board should be able to control a bigger 6v motor, such as a 280. And if it puffs magic smoke in a stall, you're only out a $10 servo.

PM

[mfr02]

I would check for binding first, then make sure that the coupling between the drive motor and shaft is not slipping. I used a head drive motor from a dead CD player on mine, and that gives plenty of drive on 4 cells.
The other thing was the propellor - the one in my kit had incredibly thich blades which gave slow forward but quite rapid sideways. I spent a long time sanding the blades to make them thinner.
For coupling the servo motor shaft, which is very short and usually rounded to make life that bit more difficult, I prefer to use a flint spring from an old, dead, disposable cigarette lighter.

[Norway2112]

Its the same setup I had originally, same battery setup and such. I do have a new Rx and Tx. The prop and shaft are clean and bind free, so maybe its thr Rx trim like Steve suggested or the shaft slipping. The prop is a prop shop 4 blade, performed great on my first tug, so I was hoping for the same or similar proformance on this one. Thanks!

Phillip

[tim slocum]

Hey, Norway, your tug looked cool pushing that 41lb battleship.Im hoping we can recreate that same scenaro at this years regatta.I know this might sound simple,but did you make sure that the shaft is turning the right direction for what hand your prop is? ei. left hand prop, shaft turns counterclockwise for forward.

[CaptLee]

Usually use a med output servo in the Lindberg conversion (60 t0 80 0z. output) but in the latest we used a quarterscale on 1" Prop Shop 3 blade and it has way too much power for the NORMAL person, runs nice with a 12 lb barge.

[Aerominded]

...it has way too much power for the NORMAL person...

Hee hee, if we're thinking of the same Lindberg tug, CaptLee, I happen to like the way it gets up on a plane! :eek: :p :) :D

[Norway2112]

Usually use a med output servo in the Lindberg conversion (60 t0 80 0z. output) but in the latest we used a quarterscale on 1" Prop Shop 3 blade and it has way too much power for the NORMAL person, runs nice with a 12 lb barge.
I have the problem solved in that it was the coupler slipping on the shaft, but with the 1" 4 blade prop shop prop, I'm having trouble trimming it out so that it will run decent, I think it has a little too much power, tends to cavitate.

[magnat]

Can we get a vid of the Tug in action !!

[mfr02]

The simplest cure for cavitation is to not turn the wick up too far too quickly.
Using a converted servo as a motor/controller, I usually just use the trim slider as an engine room telegraph. This gives full proportional control.

[rlboats2003]

Using the trimmer pot lever almost give a full range (forward and Reverse) that a normal servo conversion to boat power. I like the Hitec 700 series servos. Bigger motor with more torque but still capable of running through the receiver. Use 5 2200 -2700mah AA for 6 volts for long run times. The 5th cell also powers the 1.5 volt mini running lights. Northwest Short Line makes a 1.5mm,2.0mm and 2.4 mm shaft diameter dog bone drive systems. Prop shop props are great for the small diameter prop needs.

Happy modeling,
Rich

[Norway2112]

The coupling was slipping on both shafts....but as you can see she puts out a nice little wake like I was hoping for, moves at an acceptable pace. I'm having probs with the prop cavitating i think, which is odd because this exact same prop and shaft used to be in another Lindberg tug and worked great, maybe it needs some trimming, any suggestions?

[mfr02]

Looking at the pics, the stern looks a bit high. Trimming the batteries sternward should sit the prop a bit lower and might cure the air bubble problem.