Test Bed

[PeeWee]

HI all experienced PD's

I have just bought a Glasgow for the idea to use it as a propulsion test bed ready for when work starts on the Seeandbee.  ideally i would like to start from an educated position so i am asking for suggestions and recommendations.  This will hopefully be an electric system with independent paddles.



thank you
Ian

[Stuart Badger]

Hi PeeWee

I may make myself unpopular with you! but here goes

Firstly I would NOT recommend independant paddle drive. In full size vessels it was only ever used on paddle tugs - and even then carefully and only where other methods of manoeuvering were impossible. In a model with it's limited roll recovery having one paddle wheel operating while the other is static or in reverse can be a recipe for disaster.

As for using a model as a test bed - this is a very good idea to rationalise things like gearing and the mechanical aspects of your system. However - do not expect to learn anything about the way your final model will behave from a test bed. Each model is different, and even similar models will behave in vastly different ways - you have to work on the project in hand as it's very difficult to predict all but very basic behaviour from a test bed.

Good luck and have fun!

Stuart

[derekwarner_decoy]

Hi PD's.......Stuart is not on his own here PeeWee...in the old Yahoo days I purchased two x each Action Man mixer amplifiers & speed controllers & lots of other bits 

My end comment on PD's was that the result seemed ROBOTIC...& nothing like what I assumed a paddler should be

I suppose we sometimes get caught up in a vision of "perfection" in handling which did not exist

Again as Stuart eludes to.....we had extensive research & discussion of Maritime incidents where the Courts investigated loss of life due specifically to independent engine control to each wheel ..... .... ...one wheel dipped ...the opposite lifted out of the water & the engine overspeed .....the resulting in engine failure ...& the loss of life

Our final conclusions were that vessels with 'independent' wheel control contravened British Board of Trade Statutes.........Derek

PS....I was not, nor am in any way questioning the functionality of the previously nominated electronic equipment...I did acknowledge that they appeared totally suitable for tanks or track diven space vehicles

[Talisman]

As above i would agree they just don't look right on the water.
If stearage is your worry why not make a rudder extension which can be clipped on when on the water and removed when on display.

[PeeWee]

Hi All,

thank you for your responces, i could not be offended by any responses, if i was someone so easily put out then i would have no right being on a forum.

The test bed would only be used of testing Motor, ESC, Battery and paddle combinations.  By using the same hull and therefore same overall displacement i would be able to calculate power to battery life etc of a paddler. Not having built one before this would be vital for the Seeandbee (pending plans etc)  Stability is something i am aware of being impossible to test in this system.

It looks like single drive is the considered option from your experience and i will bow to your practical experience and knowledge in this area, therefore initial testing would be in this direction.

What options of drive transfer have been tried, IE chain, belt, geared etc. ideally i would not wish to have a noisy drive train.

again thank you

Ian

[scotfriend]

Hi PD's,

two years a go i build an two motor independent paddledrive in my Glasgow, i use one Graupner microspeed 10 speed controller for each motor, and on my transmitter i have one motor on channel one and the other on channel three, the rudder is also in working order. It isn't easy to sail this boat because the two motors are not really at the same speed with some wind or flow you must keep all the time an eye on your model. I like the challenge to sail this model and it is nice to turn it round like on a turntable. My problem is that the first motors i have bought are not strong enough (only 4 watt) they went away after 10-12 hours sailing so i ordered new ones (16 Watt) and what can i say the first one was dead after 3 hours. At the moment i like to wast the whole project with two motors because it is to expensive buying always new motors.

regards Hans

[Talisman]

Very impressed with your motor mount / drive system, would i be right in assuming you can adjust the tension in the belt?  :terrificoh
 to have the tools and skill to produce something like that ...

[bogstandard]

PeeWee,

The Glasgow is in fact a rather special hull. It is so forgiving and beamy, almost whatever you put in it, the hull will remain stable and give good results. So when you move onto a more slimline model, as mentioned, you might find all your testbed results will mean absolutely nothing.

All I can suggest is if you want to go the independant route, buy matched sets of all parts.

Don't go for the cheapo, open gearbox, build it to how you want it type. They are just too noisy. You can get super quality small sized industrial motors with g/boxes now with fixed ratios for reasonably low cost. I would go for one that gives an output of around 120 to 150 RPM.
For your matched speed contollers, try to get them that give exactly the same output no matter which way they run. Some give a reduced output when run in reverse. They will be more expensive than the cheapo's knocking about, but you only build the boat the once, so put in there the very best you can afford. Electronize are very good, but being rather large you can soon runout of hull space.
The last and to me the most important thing, get yourself a good rudder/motor mixer. That will take care of all the guesswork when sailing, and you won't need to worry too much if you do get into difficulties. If you set it all up correctly, it won't allow you to put your boat in danger. Plus you can run the whole lot from a two channel set.

John

[steamboatmodel]

I think John has hit the nail on the head. I have found that most people who install independent drive for multi propped boats or for side wheelers rely to much on them. A good friend of mine has independent control on his model, when he lets someone new try it out he advises them to ignore the independent control, until they have mastered maneuvering without it. You then start using the independent controls for small control changes.
Regards,
Gerald

[PeeWee]

I have used independent control on warships before and only once did i not have a mixer.  that ship required so much concentrated that i normally walked away with a headache. 

Mixers i think would be a must, once i had one set up that if i had full rudder from zero motor input then they would run opposite, managed to turn a 6 ft destroyer on a postage stamp. 

though its looking like paddles needs serious thought and planning and its that challenge i am looking forward to, indipendant drive or not.

lovely engineering Hans

[PeeWee]

Hi All,

Glasgow has arrived and looks like a good base model and easy to customise.

Thinking about motors, have any of you used either of the following

http://www.mobilemarinemodels.com/acatalog/Motors.html  G5

or

http://www.precisionmicrodrives.com/product_info.php?products_id=111

cheers
Ian

[bogstandard]

PeeWee,

The Mobile Marine G5 are the type I fitted, but mine were from my own sources.

You would need to ask them either the output speed of the gearbox at 12 volts, or the max rpm of the motor at 12 volts, and divide it by 44. You really need to be somewhere around the magic 150 RPM mark. Much higher and you would need to start playing around with different sized pulleys to get it to where you need it, too low, and you will not have enough speed to get you out of trouble. Your normal cruising about would be done at around 2/3rds throttle, with the top third as a run away from dogs and ducks, or fast stopping by going into reverse.

It is a shame really, as I gave all my spare ones away last year to a good cause.

Hope this helps.

John

[PeeWee]

Thank you John,  I will give MM a call tomorrow and confirm the motors details.

Ian

[Eddy Matthews]

Thank you John,  I will give MM a call tomorrow and confirm the motors details.

Ian

I'd be interested to hear the figures for the G5 motors Ian - Can you try to establish the no-load RPM at 12 volts, and also an idea of current draw for the motors?

Dimensions of the motors would also help - length, diameter, and output shaft size....

Regards
Eddy

[PeeWee]

Hi Eddy.

As requested, I spoke MMM today and have ordered 2 of these motors for testing.

the dimensions are
Shaft dia. = 5mm
Body size:-
OAL = 60mm
Dia. = 36mm

the RPM is said to be around 60-70 on 12v and half that on 6v

If this is the case then it would be a simple 2:1 pulley/gear system to reach the magic 150 RPM on full emergency power.

I will try to run some basic load free testing once they arrive.

Bad news is that they may be going out of production.
hope this helps
Ian