Topic: Twin motor setup (Read 2899 times)

rickles23 · « **on:** July 16, 2020, 09:41:05 am »

Hi,

My knowledge of the black arts is limited so I hope you can understand this.

Is it possible to adapt two old servos to run as drive motors for a new project. If so how is it done, simple steps please with diagrams

Also rather than install a rudder could I steer by using the electric motors?

I use Futaba radio gear.

Thanks in advance.

Regards

Tug Fanatic · « **Reply #1 on:** July 16, 2020, 10:50:42 am »

Quote from: rickles23 on July 16, 2020, 09:41:05 am

Hi,

...........Is it possible to adapt two old servos to run as drive motors for a new project. If so how is it done, simple steps please with diagrams

Also rather than install a rudder could I steer by using the electric motors?................

Yes it is quite possible to both use servos as motors and have them as rudders (tank steering).

To convert a servo to a motor and controller basically involves removing the gearing inside the servo and either adjusting the feedback pot to a suitable neutral or replacing it with a suitable resistor. Remember all servos are, in detail, different. The problem that often arises is that the stopped position you controller is very precise which can make life less easy. Remember that servos are small motors. The link keeps the electronics in the servo case but you can obviously separate the parts.

http://www.boatnerd.com/model/tug/others/hyneshowto.htm

Tank steering works best with slow speeds, short hulls and widely spaced props. Long narrow hulls at high speed don't turn much! Personally I don't like tank steering but others will disagree. You turn the boat by increasing one motor throttle and reducing the other which isn't good if you want full power and turning at the same time

Allnightin · « **Reply #2 on:** July 16, 2020, 03:00:27 pm »

You can avoid the problem of finding the stop position if you use a continuous rotation servo rather than a conventional one as I explained here:

https://www.modelboatmayhem.co.uk/forum/index.php/topic,62952.msg665029.html#msg665029

Tug Fanatic · « **Reply #3 on:** July 16, 2020, 03:24:58 pm »

I would observe that all you are buying is a motor and an esc. There are lots of esc for around £4 on ebay (make sure that you get one without brake) and hundreds of motors for little more than £1 (make sure you buy one with carbon brushes).

This gives much more choice about what you actually end up with.

malcolmfrary · « **Reply #4 on:** July 16, 2020, 05:19:50 pm »

A small ESC Without Brake gives the combination of a wider choice of votage, more current (therefore a wider choice of motor) and a decent deadband for easy stopping.
Way back, butchering a servo was my preferred way to go, even to the extent of using an optically coupled switching amplifier to go between the servo guts (minus motor) and a much bigger motor. The lack of a deadband was a bit of hassle, but the advent of a range of smaller fully electronic ESCs that could handle high currents reliably while costing less than the transistors I was using caused me to rethink. For me, the availability of the small ESCs that can run on 6 cells or 2S Lipo has ended any thought of servo innrds. Unless I have a want for a winch and a dead servo. Then the Motor and gearbox are usable.
Another problem with a servo motor was the lack of a spindle. Very short, and a radiused end. Best way was a flint spring from a dead disposable gas lighter. Or, one of the motors from a dead CD/DVD deck. Usually a decent spindle, and a good match for the servo electronics. I would not be surprised if they were no longer brushed motors, though.

Stan · « **Reply #5 on:** July 16, 2020, 10:06:23 pm »

My question is this. What are you going to use servo motors for? These are very small motors and the will not handle much current they would be OK in a plastic kit conversation. This is something that was done many years but it is old hat these days but each to there own good luck with your project

Stan.

With guidance.

malcolmfrary · « **Reply #6 on:** July 17, 2020, 09:00:10 am »

I was assuming something about the size of, at max, one of the Lindberg Classic series. A servo's electronics will handle a nominal 6 volts tops and be able to handle a motor drawing 0.5A, so about 3 watts into the motor, probably around 2 and a bit watts power out. Not much, but enough for scale speed on a nicely shaped hull that size. Anything bigger or needing more power, real ESCs and motors become needed.

john44 · « **Reply #7 on:** July 17, 2020, 09:35:42 am »

Why would you want to convert 2 servo,s for use as drive motors?
Component shop provide a good selection of small motors, some with gearboxes.
They even do mini esc,s voltage reducers etc
You don,t say what and where they are to be used in/ on

John

Tug Fanatic · « **Reply #8 on:** July 17, 2020, 09:47:23 am »

Quote from: malcolmfrary on July 17, 2020, 09:00:10 am

I was assuming something about the size of, at max, one of the Lindberg Classic series. A servo's electronics will handle a nominal 6 volts tops and be able to handle a motor drawing 0.5A, so about 3 watts into the motor, probably around 2 and a bit watts power out. Not much, but enough for scale speed on a nicely shaped hull that size. Anything bigger or needing more power, real ESCs and motors become needed.

The Lindberg Harbour Tug is one of the classic plastic kits to convert. It is very weight sensitive so be careful. If you go the converted servo route then I believe that you will need a standard size servo (2oz - 50gm) rather than the continuous rotation micro servo suggested above. There is absolutely nothing wrong with doing this and the link that I gave earlier was for just such a conversion in a Lindberg tug. Personally I would go with separate components but I understand the "all in one box" appeal.

rickles23 · « **Reply #9 on:** July 17, 2020, 10:54:40 am »

Hi all,

Thank you all for the replies.

I have been asked to convert a small plastic warship to r/c.

I have just finished a 12 inch torpedo boat conversion that uses a single 'servo' type set up already installed, that is why I went with the servo idea.

Tug Fanatic

I went to the link and followed the instructions and photos. I then set up the gear on the bench and it works just fine.

Regards

Tug Fanatic · « **Reply #10 on:** July 17, 2020, 11:34:50 am »

Great

For my reference information what servo did you use and do you have a reasonable "stopped" area on transmitter stick throw?

rickles23 · « **Reply #11 on:** July 17, 2020, 12:15:27 pm »

Tug Fanatic,

Servo was a Hitec HS-311.

Nearly one (1) centimetre from centre to a low go start.

Regards

roycv · « **Reply #12 on:** July 17, 2020, 01:20:28 pm »

Hi, reference the small esc's now available there is a 'tank' version with a 2 channel i/p for driving 2 motors, connection is again using the sometimes used 2 pin Rx type connectors.

I agree taking a servo apart is not necessary these days and I saw a 1 grm esc in my searches so must fit into any small space.

regards
Roythat

rickles23 · « **Reply #13 on:** July 17, 2020, 05:06:18 pm »

roycv,

I shall have a look into this before going any further.

Regards

roycv · « **Reply #14 on:** July 17, 2020, 06:12:18 pm »

Hi Rickles here is what looks like a bargain of 2 separate speed contollers for £5.61. I have not tried them but just about to place an order myself. They look like the ones I already have in use. They work fine off 6 cells or 2 lipos. I suggest no more than 4 amps as Chinese amps seem different to ours!

The without brake is good for boats as otherwise there is a pause before going into reverse. You will need to buy some 2 pin battery leads, male and female but they are very cheap, there is also a built in BEC for the rx.

Roy

ttps://www.ebay.co.uk/itm/2-Piece-Dual-Way-Brushed-ESC-for-RC-Truck-Tank-Car-3-9-4V-without-Brake/164240384845?hash=item263d7d634d:g:9DIAAOSwgHxe4e5w

Tug Fanatic · « **Reply #15 on:** July 18, 2020, 09:11:38 am »

There is a build of a Lindberg Tug currently going on in this blog by Phil Parker who also contributes to this forum:
http://philsworkbench.blogspot.com/search/label/Lindberg%20Tugboat

Roycv
Does your double controller work with 1S (1 lipo) satisfactorily?

roycv · « **Reply #16 on:** July 18, 2020, 09:41:44 am »

Hi Tug, I only said one was available, I have had a closer look at that spec and am not really sure about it as it refers to switching LEDs on the extra channel. It is a lot of Chinese speak which is difficult to pin down. However I did put my money where my mouth is and ordered as mentioned in my last post.

This is for 2 separate brushed esc's for less than 3 quid each. I have a couple in use and they are tiny and excellent in performance. They use a 2kHz PRF for motor control and you can hear this on the bench but not when in the water. I am driving Monoperm motors and would be confident to use them up to about 4 amps, they run on 6 cells, 7.2 volts.
When a servo (standard) gives up the ghost the drive motor is usually working so worth stripping out, they can be used for really small boats.

regards
Roy

Tug Fanatic · « **Reply #17 on:** July 18, 2020, 09:55:50 am »

Are we looking at the same thing? The description that I get by using your link doesn't mention anything about LED's.
ttps://www.ebay.co.uk/itm/2-Piece-Dual-Way-Brushed-ESC-for-RC-Truck-Tank-Car-3-9-4V-without-Brake/164240384845?hash=item263d7d634d:g:9DIAAOSwgHxe4e5w

Tug Fanatic · « **Reply #18 on:** July 18, 2020, 10:46:51 am »

Sorry got confused. You are talking about 2 different things.

malcolmfrary · « **Reply #19 on:** July 19, 2020, 09:30:17 am »

Complete link that should work -
https://www.ebay.co.uk/itm/2-Piece-Dual-Way-Brushed-ESC-for-RC-Truck-Tank-Car-3-9-4V-without-Brake/164240384845?hash=item263d7d634d:g:9DIAAOSwgHxe4e5w
2 of 20 oriental Amps ESCs. Looking at the wires, probably 3 or 4 real world Amps. Should be good for 2S or 7 cell NiMH. Just my opinion, but not less than 4.8 volts, the regulator in the BEC will likely be out of range, and a low supply voltage will probably cause the internal electronics to misbehave at somepoint. It "might" work on 1S, but deliberately starting well into a safety margin is rarely a good practice.
No idea what the postage to Australia might be.

roycv · « **Reply #20 on:** July 19, 2020, 09:47:52 am »

Hi I have run one on 6 volts OK. But at around 1 -2 amps there is no sign of heating and you will note there is no heat sink either. I bought one tried it out and immediately bought 2 more and have ordered another 2. I shall try them on Monoperm Supers as well.
My postage was free although you can expect to wait a long time. Buying from Australia is a shorter route to China and at these prices probably no GST charge either.

Incidently I bought some 'saw drills' Yes I wondered too! They are a normal drill bit for half an inch and then a serrated spiral and come in several sizes. You drill in and then with the drill still running use a sawing action to elongate the hole to make a slot. I have a set of 6 from 3mm upward and they were a modest £5.68 p&p free.
I came across them from a video from Phil Parker on making a model railway layout and cutting a slot for the point actuator below.
regards
Roy

Tug Fanatic · « **Reply #21 on:** July 20, 2020, 07:12:32 pm »

Quote from: malcolmfrary on July 19, 2020, 09:30:17 am

Complete link that should work -
https://www.ebay.co.uk/itm/2-Piece-Dual-Way-Brushed-ESC-for-RC-Truck-Tank-Car-3-9-4V-without-Brake/164240384845?hash=item263d7d634d:g:9DIAAOSwgHxe4e5w
2 of 20 oriental Amps ESCs. Looking at the wires, probably 3 or 4 real world Amps. Should be good for 2S or 7 cell NiMH. Just my opinion, but not less than 4.8 volts, the regulator in the BEC will likely be out of range, and a low supply voltage will probably cause the internal electronics to misbehave at some point. It "might" work on 1S, but deliberately starting well into a safety margin is rarely a good practice.
No idea what the postage to Australia might be.

I don't think that have a built in BEC

Plastic - RIP · « **Reply #22 on:** July 20, 2020, 07:22:41 pm »

Quote from: malcolmfrary on July 19, 2020, 09:30:17 am

Complete link that should work -
https://www.ebay.co.uk/itm/2-Piece-Dual-Way-Brushed-ESC-for-RC-Truck-Tank-Car-3-9-4V-without-Brake/164240384845?hash=item263d7d634d:g:9DIAAOSwgHxe4e5w
2 of 20 oriental Amps ESCs. Looking at the wires, probably 3 or 4 real world Amps. Should be good for 2S or 7 cell NiMH. Just my opinion, but not less than 4.8 volts, the regulator in the BEC will likely be out of range, and a low supply voltage will probably cause the internal electronics to misbehave at somepoint. It "might" work on 1S, but deliberately starting well into a safety margin is rarely a good practice.
No idea what the postage to Australia might be.

It's probably not a normal regulator but a DC-DC converter to convert 3V into 5V

Tug Fanatic · « **Reply #23 on:** July 20, 2020, 08:23:20 pm »

I am lost here.

I cannot see any evidence of either a BEC nor a DC-DC converter. As far as I can see they are simple Esc that work with a 3-9v supply. I think that if I wanted BEC I would need to buy a separate module.

Am I wrong?

DaveM · « **Reply #24 on:** July 20, 2020, 10:49:03 pm »

As the inclusion of some sort of voltage through-feed from the main battery to the receiver is almost universal in speed controllers these days I'd be very surprised if you need a separate Rx battery pack or whatever. Of course, I've been wrong before......

Dave M

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Author Topic: Twin motor setup (Read 2899 times)