Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[big-geoff]

Some pics of my latest build a RT80R Rotor tug

GRP Hull, Plastic card superstructure, Crane and winches made of scrap bits and bobs.
Will be using 3 Graupner Schotchell II drives, 2 forward and 1 aft.

The only problem that is concerning me at the moment is how to independently control 3 drives, any help appreciated.

[big-geoff]

Hi Martin

I am thinking of buying a 2.4ghz 6 channel set, as they have a features for flying that can be played with, just got to get the money out of SHMBO

Looking at the info from Kooreen Shipbuilding (who have a good website and have loads of info availableto download), the main drives (forward engines) are used when towing for maximum power and the aft drive when manuvering and for stering adjustment when towing. So linking the 2 forward engines may be the best bet.

I must find someware to learn how to tow, I am not aware of anyone on the Isle of Wight who is like minded. Could be the start of a whole new club....

Cheers

Geoff

[poll]

   Hi  Big Geoff,  Best way I would think would to link all three motors to gether,
   A 30 amp speedo for your main drive, and a 15amp for your stern drive.
   You need your bow motors running a bit faster then your stern motor,
   to do this adjust the power or speed on your 15amp speedo,
   To operate this function you would need a four channel radio.
   ch 2&3 for your forward & reverse,  ch 4. would steer your forward operation,
   ch 1. for your rear drive/ rudder. when you get your head round it your tug will go
   sideways. Hope this is some help.

   Regards,

  John.               POLL

[big-geoff]

Thanks Poll

I am worried about running 2 motors from 1 esc, with my last tug I did just this and found that the port motor ran faster that stb, I could not find any reason for this both drives were aligned correctly and both motors were the same (speed 400's).

Can I use a esc for each motor and run 2 from 1 channel?

I wonder if a 6 channel set could do the job?

I certainly will try the way you suggest.

By the way I am using MFA 800 motors.

Here is a picture of my 1st 1/32nd scale tug "BG Coulies"

[poll]

 Geoff.   what radio Will you use?  yes a 6 channel radio will be fine.

             I use futaba radio, & Electronize speed controllers.

             John

[big-geoff]

Hi John

I am leaning toward something that wont require xtals or even go to 2.4ghz.

But I am not sure which is best for what I want, I realy need to handle a set and get as much info on what it can do before I will open my wallet.

My Local model shop thought that the 2.4ghz set would not work with boats, they felt that if anything came between the model and transmiter signal would be lost, but they could not give an example that they had heard of, it was just their thoughts on the matter, so I want to know if that is a problem or not. I dont mind spending the money if it is going to do the job and last.

The last time I bought a new radio was 1984 Acoms 2 channel and it still works perfectly, unlike the washing machine I bought that year......

Geoff

[poll]

     Hi  Geoff,  If you look to getting a 6 ch radio, Look for one with a Linear slide or
    a rotating knob type to operate your 3rd speedo,It will be hard to set up on the main
    sticks.  Also I think It will be hard to turn with the skeg on the stern, it's good to have a skeg
    If you have just the bow drive.  see photo

[Ghost in the shell]

twin VS and a azimuth prop? 

[big-geoff]

The drawings and info that I have found from the ship builders, showed that some skeg is needed, I have probably overdone it but it is nothing that can't be sawn off if the sea trials prove them troublesome.

I have found a document reporting on the model trials for the class where the difference between a skeg and a third drive is explored, it is all very technical and lots of mathematics, what does come out of the report is that the design outperformed the predictions from the mathematics when they tested the model.

Its a way to go yet before I get this one on the water, and I hope it works

Geoff

[pakirk]

Hi big-geoff
If you get a desent Tx like the 2.4GHz It will likley have mixers built in to it. I Strongly advise from experience to use SEPERATE Speed controlers. You can get some strange thing going on if you share them. I could waffle on and explain if you wish.
Use CH 3 for the rear motor, Set this as a master. Use ch5 and ch6 for the two forward motors Slave mixed to CH3 Master.
Drive the TWO servos for the forward units via a Y splitter on Ch4 and the rear servo from ch3. You could set CH3 as a master and mix ch4 to ch3 slave. This will give you some cool auto stearing. Like easy sideways.

This is the setup I used fore one I build and worked very well.
WORNING though use very strong servos to drive thease units. They have to power against the force of the propshaft and there is an amence amount of power there. Normal servos wil not work. I use JP SO6/2BBMG servos. @ 6V.
I also advise supporting the input shafts as that tend to buckle under Load.

[big-geoff]

Thanks for the info.

I have not got as far as what servos to get, where would I get them from?

Not much choice of shop over here...

Cheers

Geoff

[tigertiger]

Thanks for the info.

I have not got as far as what servos to get, where would I get them from?

Not much choice of shop over here...

Cheers

Geoff

I got my servo's from Als Hobbies
Very good service, and some of thier stuff is very cheap. My servo's were chaper than from servo city in the US.

I know there is postage to pay, but it is chaeper than phoning/driving around and no waiting two weeks for a shop to get a delivery.

http://www.alshobbies.com/

No connection, just a satisfied customer.

[big-geoff]

Many Thanks.

[pakirk]

Hi
I could not see theas servos at alls models.
I got mine from.
http://www.phillsmodels.com/

[Captain Jack]

Might I recommend the Spektrum DX 6 radio. It's 2.4ghz,computerized mixing. All trims, mixing, setting of throw lengths, and reversing of servos (if required after installing) is all programmable via the transmitter. Got mine for $199 dollars US currency.
 As for the ESC's, using two of them through the throttle channel works great. My American Enterprise equipped with jet drives uses this set up, using a "Y" connector from the throttle channel Therefore, two esc's each controlling a motor, from one channel. Tamiya makes an esc that controls two motors also, as well as a company called Novak. That should solve your forward motors running at different speeds problem.
The available mixing functions of the radio should cover the steering challenges.
I realize the radio is intended for aircraft, but no one makes a surface frequency radio that suits our needs for boating purposes. The 2.4ghz radios are set up not to interfere with eachother, or any other radio frequencies, automatically, when you switch them on. I've had no problems with range, never had a loss of control, or have never been "mutinied" by someone elses transmitter taking over control of my boat. Best thing is, the reciever antennas are only two inches long!

http://www.hobby-lobby.com/spektrum-radios.htm?c1=google&source=camp16spek

Tamiya#40537  ESC TEU103BK twin motor

http://www.teamnovak.com/products/esc/1841rooster_crawler/index.html

The Novak unit is pricey, but it's also waterproof!

....Fair winds, and following seas,
         Cap'n Jack

[BlazingPenguin]

I'm also in the throes of building a 'RotorTug'..... I've never had any probs with two motors worked from same ESC, but I have seen witchcraft a work when two seperate ESC's are worked from the same Rx channel though.
Finally managed  to get the knitting inside my Futaba F-14 with the kind help of John Pollit....Thanks John!
The plan is two have the two forward units 'linked' this will give me max power in both straight towing and when moving sideways as bow thruster, there will always be some element of 'creep' when carrying out that manouvre, so the aft unit will give me some degree of control and enable me to 'walk' up & down the job as required.
Another useful point is that with twin motor control for on the spot steering, it takes some getting used to and will require some thought to keep the turning axis at the centre of the boat, rather than just between the screws. My method should keep the centre of effort between both sets of screws, helping tight manouvering.

[big-geoff]

I have now installed the esc's 1 for each thruster, and will link the forward thrusters onto one channel.

I am now playing with the nav ligts, thank goodness its near christmas my local garden center have a massive display of christmas lights including lots for 6v battery strings of super bright white led's £4.99 6 led's per pack (got 4), am going to strip the led's of the wires [too thick] and use for all my nav lights. Perfect. :)

All I need now is for SHIMBO to ok the spend for a Futab 2.4 gig radio, meal out tonight me thinks 

Cheers for all the input so far everyone, I will have to get it on the water and get some pictures done, lets hope next weekend is fine.

Happy sailing

Geoff