Drive system - general concensus?

[Eddy Matthews]

Hi Guys,

As a lot of you will know, I'm about to start building a model of the PS Waverley. I have two lovely geared MFA motors to use to power her, but what about the drive setup?

Should I use two motors for independent control? Not full size practice for a passenger vessel I know, but we have to be realistic and I don't want 10 foot turning circles!

Secondly, and more importantly, should I use a belt drive, chain drive, or gear drive system? I only need a 1:1 ratio drive as the motors are already geared to a suitable speed - As far as I can see, belt drive will be the quietest, but there is always the danger of slipage. Geared drive or chain drive will be noisier (sp? that just doesn't look right!) but with little or no chance of drive slip.

Finally, the motors and the paddleshaft are both 5mm diameter, so where's the best place to locate suitable pulleys/belts, sprockets/chain, or gears with that sized shaft in mind?

Regards
Eddy

[towboatjoe]

1. Definately go with independent control
2. Belt drive is best. It keeps down any noise being transmitted throughout the hull and lessens vibration.
3. The best place I know of is Stock Drive Products
http://www.sdp-si.com/index.asp

I've got a side wheeler to do in the future so keep me posted how things go.

[mjt60a]

I'm just about to face the same choice, I have two geared motors of which the output shaft turns at more or less the correct speed for the paddles. I had intended to use a geared drive (1:1) but I read elsewhere that belt drive is better and, if you can get the belt and wheels, a toothed belt like that used in a printer for the 'carriage return' is ideal.
I do intend to use independent drive BUT... I want to have both motors turn in the same direction at all times with one slowing during tight turns. I will fit a couple of microswitches on the rudder servo so they are normally closed and when open they introduce a resistance to the supply of one or other motor (haven't worked out exactly what value but something like the type used on fast electric cars) and reduce it to about half speed. The switches will operate when the rudder is at 'full turn' -
if it doesn't help much I can revert to using fully independent motors, maybe with a 'mixer' (add-on that goes between receiver and two speed controllers, enables one motor to be reversed using the rudder servo signal (?)...I've only read about them, never used one...)

[Khephre]

I like the independent control as well, having stuffed around with electric motor mixers, etc., a saga which the PDers from the old Yahoo site will know well!

I've gone for belt drives in PS Reliant, and have adjustable motor mounts to be able to add/release tension from the belts. Like Eddy I've got a couple of those luvverly MFA Geared motors, running on 12V so the output is around 106 rpm - a little sluggish for Reliant hence I've changed the pulley ratio to 1:1.5 - the higher output steps things up to around 150 rpm max at the paddlewheel.

Running around 3/4 throttle gives plenty of power with a little overscale speed in reserve for 'emergencies'. Mind you there's a hint of cavitation at the very top end so wouldn't want to use a much higher ratio.

Eddy, the belts I used were simple 'O' rings of around 3.5 - 4mm cross-section. I've had no slippage at all. But then... my paddle shafts have sealed stainless bearings at each end so the tension on the belts can be cranked up a  little higher than you might otherwise want.

You may have seen my Reliant's 'engine room' photo before but I've reposted it to the new website for reference. You can check it out at www.paddleducks.co.uk/photopost

As far as I'm concerned the end result works pretty well. Both paddle shafts can be withdrawn inside the hull so that the paddlewheels can be released, belts can be tensioned (or replaced) using the moving motor mounts, and the gearing ratios can easily be changed with a simple pulley swap-out each side.

I should imagine that the toothed belt or timing belt approach would give great results without any potential of overtensioning the transmission.

Just one question about those MFA motors - given the pile gearbox on the end, they're a bit noisy. So can I kill two birds with one stone by adding a stuffing gland to each gearbox - squirt in a bit of white grease to lube and quieten down the gears? or is that actually counter-productive?

cheers
Tony
Akl, NZ

[Eddy Matthews]

Thanks for the detailed reply and the photo Tony! A picture is worth a thousand words as they say! :-) That helps a great deal...

Where did you get the pulleys and the drivebelts?

I think I'll stick with a 1:1 drive setup, and adjust the voltage to increase or decrease the RPM if needed. I'll be using nicads, so it's easy enough to add or remove 1 or 2 cells.

Regards
Eddy

[Khephre]

Hi Eddy,

the pulleys were made locally by one of the members of our model club - a retired toolmaker and extraordinary model-maker who unfortunately passed away just a few days ago. I'm presently trying to negotiate with his estate to purchase his lathe so that I can produce pulleys etc. for other club members.

The O rings were purchased from a local bearings and seals shop - I suspect that these would be pretty plentiful in the UK as well. They're the bog-standard sort of O rings that you might expect to see in a housing or similar, and come in a huge range of sizes. They have around cross-section and are not too elastic.

Hope this helps.

Any thoughts on lubing the MFA gearboxes - waste of time or worth doing do you think?

Cheers for now

Tony

[Eddy Matthews]

I have used lithium grease on the gearboxes in the past, it doesn't clog them up and does help to reduce the noise a little.

Regards
Eddy

[Khephre]

Tks mate
Tony

[Walter Snowdon]

I would go for larger pulleys as they give a larger friction area and does away with risk of slippage. Also, as both motor and shaft speeds are very low, pulleys are not critical and can be made out of ply or plastic card laminations. Or how about old Mecanno pulleys? easily available second-hand and very cheep. These can be reemed out with a rat tail file to fit shafts.  (Eddy, for fabricated pulleys see Jakes paddlers, and for mecanno pulleys catch me with a pint in your hand) . For those who dont know Jake, he is a superb simplicity engineer. He cuts O rings to length and joins the ends with a tiny spot of superglue. Not one of them has come apart in several years of use,  Cheers, Walter

[Eddy Matthews]

(Eddy, for mecanno pulleys catch me with a pint in your hand) . Cheers, Walter

Why would me having a pint in my hand make any difference Walter? You don't even like lager!  :lol:

Regards
Eddy

[John Atwood]

Paddlwwheelers,

I built the Jeanie Deans (81" in length) from plans.  I paced myself as to what drive system I was going to use in the boat to drive both side paddles.  Rather than an independent drive system for each paddle, I chose a single drive for both paddles.

As it turned out, it was pretty simple and straight forward.
 
I found several catalogs that have a ton of small parts for drive systems.  I will look in my office for the name of them and will pass them on.
They had all I need.  A dream come true for me.  Cogged belts to match the drive teeth for the right size shafts.  

I used a 24 volt system because I need the weight in the boat!  I still added sand bags for additional weight.  John Atwood

[towboatjoe]

The best place I know for small gears and belts is Stock Drive Products
http://www.sdp-si.com/index.asp