Model Boat Mayhem

Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: markrider on January 16, 2019, 08:48:07 pm

Title: 3 motor limit switch set up
Post by: markrider on January 16, 2019, 08:48:07 pm

So I have a PT boat with 3 motors
Have herd people set them up so when you do hard turns it turns the I side motor the other way to help turn.
They use limit switch and relays .
Any ideas how you would set that up to do thanks


Mark

Title: Re: 3 motor limit switch set up
Post by: RST on January 16, 2019, 09:36:36 pm

Depends on how you look at this.  These days modelling is getting increasingly complicated with computer controlled radio systems.  I don't buy this -I'm no programmer nor want to be so ome extra info would help...

• Are you dissatified with the current set-up you have?
• I currently have a PT boat in build less than 600mm length -what PT boat and size do you have?
• What set-up do you have (motors, ESC's, radio)?
• What is the size of the motors (physical size, current draw, any idents like "speed 400, 500" etc.?) and what batteries do you use?
• Are you you analogue or 2.4ghz radio?

....I think that's the kind of info folk will ask for otherwise we could recommend you the same things in the books, magazines and the rest of the internet will.  Pictures help also, but as I have no personal hosting method now I cannot advise how to post them here.

There's lots of PT boat builds and how-to's on the US forums (obviously, notwithstanding any UK builds).  In case you didn't know, a good place for PT boat models is https://www.rcgroups.com/forums/index.php



Cheers,
Rich

Title: Re: 3 motor limit switch set up
Post by: markrider on January 16, 2019, 10:02:29 pm

Hi
So it's Graupner Wiesel I'm rebuilding
3 X 540s motors and 11.4 lipo 3s
2.4ghz
I have seen limit switches used on the servo horn so when full steering it hits the switch but not sure how to reverse the motor ?

Title: Re: 3 motor limit switch set up
Post by: Klunk on January 16, 2019, 10:53:20 pm

have a look here
http://www.lutonmodelboat.co.uk/frame_hints.html
select Keith applefords section. should be mist of what you want there for old school stuff. I run 2 tugs with the microswitchs. one of which is a paddle wheeler

Title: Re: 3 motor limit switch set up
Post by: Plastic - RIP on January 17, 2019, 07:11:45 am

Isn't this normally done with 3 speed controllers and a model airplane elevon controller?


The 2 outers go through the elevon controller (throttle = elevator and steering = aileron) and the middle is just connected to the throttle?

Title: Re: 3 motor limit switch set up
Post by: Umi_Ryuzuki on January 17, 2019, 07:53:02 am

Often, a set of switches are set at the extent of the rudder horn travel.
The full throw of the rudder will never contact the switch unless the trim tab is thrown fully to
one side.This is done as a safety, so that the motor won't be reversed at full speed.

A pair of micro switches can be cemented together to create a double pole double throw switch.
The common would be run to the motor, and you would solder the leads from the ESC to the normally closed
tabs of the switch. So if  the switch is never thrown, the boat runs.
.
The leads +/- are then crossed over, and soldered to the normally open tabs. So when the trim is thrown to
contact the switch it will connect the crossover leads to the motor and allow you to spin the boat in the harbor.

So, sort of that...  ok2

Title: Re: 3 motor limit switch set up
Post by: malcolmfrary on January 17, 2019, 10:44:49 am

The limit switch is normally intended to just cut the inside motor, being mounted so that the rudder linkage just operates it at the rudder limit.  The resulting one sided drag is enough to enhance steering when running.  The reduction in power at this time helps reduce instability if turning when running flat out.  Most commonly used when only using one ESC.  Micro switches are pushing their limits when used in motor circuits - the "micro" does not refer to their size, it refers to the very short switching tme and could well refer to their current switching ability.
Using a mixer between the radio and ESCs works well and is proportional.  If the transmitter supports mixing, that works OK as well.

Title: Re: 3 motor limit switch set up
Post by: roycv on January 17, 2019, 11:09:36 am

Hi I agree with Malcolm reversing the inside motor is not necessary, it will be quite effective just stopping the motor.
regards,Roy

Title: Re: 3 motor limit switch set up
Post by: markrider on January 17, 2019, 12:08:46 pm

Thanks for replys chaps
Roy/Malcom
Yes that's the way .I'm.only using 1 ESC for it
Assume action do mixers
As my TX doesn't and can't see you can with one ESC would need 3 I would of thought ?


Thanks
Mark

Title: Re: 3 motor limit switch set up
Post by: DaveM on January 17, 2019, 02:01:13 pm

ACTion solution is here.Scroll down the list and click on Graupner Wiesel https://action-electronics.co.uk/wd.html (https://action-electronics.co.uk/wd.html)
Note P92/3 is now called P102. 500E motors and 12v battery can be replaced with the types you specified, although I'd recommend the 20A version of P94 and not the Lite (10A) type.
Latest incarnation of P94 has BEC so you must not use the 5v flylead from the P102 to the receiver.Dave M