Sternwheeler drive belt.

[Paul]

Hi folks,

My first posting and it's nothing but questions!

My queries are in regard to drive components for an upcoming project - my first attempt at a paddle drive boat.

The project in question is a 1:12 ( 42" ) model of the stern paddle launch called "Alligator" which was described in the May/June issue of the "Rudder" magazine in 1911.  I sourced a copy of said plans from John Fryant in the USA which briefly describes this vessel as being 42 foot in length and basically a very large flat bottomed punt.

I intend to power the model using an MFA/Como motor and gearbox assembly ( 50:1 ratio ) on 7.2V using a toothed belt drive to the paddlle wheel.  This wheel will be six inches in diameter with eight floats.

So far so good.  Now come the questions.

Other postings have referred to drive components sourced from SDP-SI in the USA. I've had a look at said site but am uncertain about what the best belt tooth pitch to use.  Is 2.5 mm too fine or should I look at say 3mm or perhaps 5mm ?  Is a belt width of 6mm acceptable - my concerns being that of the belt skipping teeth on the sprockets if too fine in pitch or too narrow in width ?

For a sternwheeler what is an acceptable wheel speed in free air and what will it likely drop to once the wheel is in the water?  This info. hopefully will help me select the size of the belt sprockets and the subsequent final drive gear ratio.

The MFA/Como motor gearbox combination referred to previously is base around a 540/1 three pole motor.  May I ask for suggestions as to what capacity ESC to use with this assembly?

Why choose this vessel as a first project you ask.  Well I saw a photo and brief description of a model called "Alligator" in Ships in Scale Nov/Dec 2010 and was very much taken with it, and then the more I thought about it I realised it was 100 years ago this month that said vessel was described in the magazine and felt I had better do something about it's centenary!  That's my excuse anyway. Furthermore, perhaps this could be the first alligator to be seen in or on Australian waters!

Cheers,

Paul.

[derekwarner_decoy]

Hi PD's ...& welcome Paul...a few points to ponder

1. Toothed drive belts usually matched to the width of the toothed pulleys........model car shops are a good source for both the pulleys & belts
2. the belts are extremely high in their tensile strength...they don't stretch [high strength reinforcement braiding bonded in a durable polyurethane belting matrix]
3. remember those model cars have high power IC engines & running at 12,000 rpm
4. your paddler engine as below may provide 1/50 of output power of those car IC engines
5. do a search in our PD search box on .....paddle wheel speed ...... paddle wheel RPM
6. you will find many references of full size shaft rpm of 30 to 70
7. you will also find references of model rpm being in the order of 150 rpm in water
8. the important requirement here is high torque & your chosen motor/gearbox should provide this
finally ...... 
9.many model paddle drives have been based on electric motor/gearbox of say 300 rpm max.... & then coupled with  an electronic speed controller to provide optimal shaft paddle speed

Now all of this would be OK for a side paddle wheeler where the motor & paddle shaft are say 2""apart......but I have not seen such small toother belts of say 8"circumference or sufficiently long to provide rotation to a stern wheel 

Spend some time in PD searches & think about it all & come back with your thoughts or more questions......Derek

[Eddy Matthews]

Welcome to Paddlducks Paul....

I've never found the MFA motors/gearboxes to be that good - The motors draw a very high current compared to Beuhler or Pitman motors. The upside is that the MFA motors are easy to get, Beuhlers and Pitmans are difficult to find!

I've only built 2 sternwheelers, and both of them had drive systems that gave about 80-90 rpm unloaded speed (ie. out of the water). This was too fast! So they needed very gentle use on the throttle to look realistic on the water. If I was building another one, I'd look for a paddle speed of about 60 rpm.

With the MFA motor, you'll need a 15 amp controller to be safe, with a Beuhler or Pitman 5 amp would be more than enough.

Regards
Eddy

[Barry]

http://www.motionco.co.uk/ have a wide range of belts and pulleys. Plastic chains and gears as well. There's a 'Centre Distance Calculator' which will work out the length of belt needed. Quite a few model helicopters use belts to drive the tail rotor that could be another avenue to look at.

[PeeWee]

Hi,
there is also HPC gears http://www.hpcgears.com/ when i was looking for some pullies and belts there proved to be very helpful on the phone. 

[mjt60a]

...errrr, isn't the aligator a sidewheeler?...am I confusing it with another similarly named type of craft?

[steamboatmodel]

...errrr, isn't the aligator a sidewheeler?...am I confusing it with another similarly named type of craft?

The Alligator he is referring to is a Sternwheel Launch. From the pages of the May & June 1911 issues of "The Rudder" Magazine. It is sternwheel pleasure boat design by R. M. Haddock and was never built. The sidewheel Alligators were built and used in logging.
Regards,
Gerald.

[mjt60a]

ah, yes I see, the sternwheeler looks like an attractive boat actually.....

[Paul]

Hi Eddy,

Thankyou for the info re. paddle speed.   Having done a little reading of the various posting I got the impression that the model paddle speed had to be greater by an appreciable amount than that of the full size vessel to compensate for slippage.  Your suggestion of 6o RPM ( which I assume is with the wheel assembly in the water ) is in fact the suggested speed for the full size "Alligator" launch ( 50 to 60 RPM actually ).  Am I to assume that a sternwheeler would in fact have a slower paddle RPM than a side wheeler?  Is this perhaps a situation where one big wheel is more efficient than two smaller ones?

Cheers,
Paul.

Welcome to Paddlducks Paul....

I've never found the MFA motors/gearboxes to be that good - The motors draw a very high current compared to Beuhler or Pitman motors. The upside is that the MFA motors are easy to get, Beuhlers and Pitmans are difficult to find!

I've only built 2 sternwheelers, and both of them had drive systems that gave about 80-90 rpm unloaded speed (ie. out of the water). This was too fast! So they needed very gentle use on the throttle to look realistic on the water. If I was building another one, I'd look for a paddle speed of about 60 rpm.

With the MFA motor, you'll need a 15 amp controller to be safe, with a Beuhler or Pitman 5 amp would be more than enough.

Regards
Eddy

[steamboatmodel]

Hi Eddy,

Thankyou for the info re. paddle speed.   Having done a little reading of the various posting I got the impression that the model paddle speed had to be greater by an appreciable amount than that of the full size vessel to compensate for slippage.  Your suggestion of 6o RPM ( which I assume is with the wheel assembly in the water ) is in fact the suggested speed for the full size "Alligator" launch ( 50 to 60 RPM actually ).  Am I to assume that a sternwheeler would in fact have a slower paddle RPM than a side wheeler?  Is this perhaps a situation where one big wheel is more efficient than two smaller ones?

Cheers,
Paul.

Welcome to Paddlducks Paul....

I've never found the MFA motors/gearboxes to be that good - The motors draw a very high current compared to Beuhler or Pitman motors. The upside is that the MFA motors are easy to get, Beuhlers and Pitmans are difficult to find!

I've only built 2 sternwheelers, and both of them had drive systems that gave about 80-90 rpm unloaded speed (ie. out of the water). This was too fast! So they needed very gentle use on the throttle to look realistic on the water. If I was building another one, I'd look for a paddle speed of about 60 rpm.

With the MFA motor, you'll need a 15 amp controller to be safe, with a Beuhler or Pitman 5 amp would be more than enough.

Regards
Eddy

Paul
The suggested speed for the Alligator launch is just that, as a full size boat was never built. The design published was done for an article in a magazine.
Regards,
Gerald.

[Yabbie1]

Hello Paul,

My first post here.  I know it's been a while Paul, but I'm wondering how you are getting on with your Alligator.

I have often looked at the Alligator's drawings (as reproduced in the book of The Rudder plans, "Designs to Inspire" and thought about building a model of it, but you've beaten me to it.  Although it's a simple flat-bottomed utility boat, it has quite a sense of style to it, with the paddle wheel nicely integrated into the lines.  I would have considered a plastic linked chain drive for the wheel, via a geared motor dressed up to look like the full-size transverse driving engine.

I would be interested to hear if you solved the drive speed question, and how well (or badly) the model steers.

Regards, Yabbie1.