Sternwheeler reduction ratio

[kiwimodeller]

Greetings all, I am hoping that some of us have had some experience with a steam powered sternwneeler and can give me some advice on what reduction ratio I should be looking for in the drive. My side wheeler goes well on a ratio of only 3.7 :1 but all the info we have on here says trhat sidewheelers need around 120 to 150 revs whereas a sternwheeler only needs the wheel to be running at about 40 to 60 rpm so presumably the reduction ratio needs to be at least double. The engine is a 16mm x 16mm double acting V twin. It seems that most steam engines run best around 400 to 500 rpm under load so that means a reduction of 10 to 1 would be needed to keep the wheel speed correct but any comments or suggestions would be most welcome. Thanks, Ian.

[derekwarner_decoy]

Hi Pd's........ ...Ian...I understand our previous thoughts on sidewheelers.... "need around 120 to 150" RPM, but not to sure where the 40 to 60 RPM for a stern wheel came from 

We could consider the swept surface area x depth [SSAxD] of x 2 for a twin side paddle & compare the [SSAxD] 1x for a single stern paddle

All things being equal  ...surface area x blade numbers [SSAxD] should be equal ....or  ....Derek 

[kiwimodeller]

Derek, in the post http://www.paddleducks.co.uk/smf/index.php?topic=5601.0 Eddy says he has built two sternwheelers that had wheel revs of 80 to 90 rpm out of the water and that this is too fast, that we should look at speeds of 40 to 60 rpm in the water. I am sure I have read the same in older posts to and anyway I aint gonner argue with Eddie! Cheers, Ian.

[Bierjunge]

It would be easier to answer your question if you tell us in addition

• the diameter of the sternwheel
• the surface area of each bucket
• the average number of buckets immersed
• the scale of the model boat
• the rough size (length, front surface, displacement) of the prototype

Then I would volunteer to make some calculations. It's all interconnected somehow, you know.

Moritz

[bill stafford]

there are a lot of variables to drive , inc. wind
be carfull , a stern wheeler may need up to 200 rpm , to get enough thrust to steer
my side wheel paddler revs up to 330 rpm (maths , on paper ) , but on a windy day , it has being called the turtle , slow .
dont tel any-one , but i have considered concealed props for next paddler , due to stroung winds were i sail
bill