Gearboxes (and motors)

[derekwarner_decoy]

Hi PD's....& yes Kiwi.........we reviewed & discussed the paper by Mr Brittle some years ago.........& whilst it considers & explains very well the dynamics of feathering paddles..........to my understanding very few OZ paddlers were fitted with the same ......

From memory & according to "Parsons"..... PS Moolgewanke  [ON31571] in the 1860's was the only paddler on our OZ waters with feathering wheels.........  ...I always thought the vessel had an unfortunate name........  .......Derek

[Harold H. Duncan]

Hi Derek,
Was just asking as the question had been asked re rpm required, may have been a different thread, or maybe on MBH, (yes I know but its way, way past my bedtime and the senior moments are holding hands).
Am well aware re the Murray River paddlers and their power plans are configured, having spent some time on the river during my 25 years living in South Australia. And your right, as I do vaguelly remember that discussion.
Was just using that as an indication of paddle rpm, as I'm doing a similar exercise for models of our local stern wheelers from the 1860's and later, which did have feathering.
We must catch up sometime when next I'm in Sydney, as I often travel south while I'm there.
cheers
kiwi

[bill stafford]

hello kiwi,
 i think i read this a while ago , and i will enjoy reading it again , thanks , BUT
i tend to reley on experiences , so , again , i state , paddlers do funny things .
i had my paddle running beside a larger adelaide , w 14 floats per p wheel , and larger out-side diameter ,in 1/18 scale .
my paddler had a smaller hull (1100mm approx.to 1500 mm adelaide ) 8 floats and a scale smaller OD p wheel , yet the adelaide was by far quicker, easier driven ,and slower revs than mine , yet walked away from me .
it was clear from this that my paddle wheels would reach a max. speed , by going any quicker , all i did was create more bubbles, it did generate more thrust , but not very efficiently .
my observations on this day , the larger diam. wheels seemed to be more efficient , w 14 floats , i suspect the diam. of the p wheel was a big part in it , but i dont really know , paddlers are all different , and do funny things
regards bill s

[derekwarner_decoy]

Hullo Bill & Kiwi....I agree paddle wheel dynamics are intriguing.....but we must be able to compare apples with apples

My float a boat plans for PS Adelaide were drawn as 1:24, however this did not provide sufficient calculated flotation for my engine & boiler so had the plans enlarged to 1:20

The new wheel size is 210 mm OD, the paddle blade wdith is 75 mm with a height of 18 mm & a 6mm 45 degree chamfer on the outer edge only, however with the hull at near correct waterline draft, effectively only three blades can be in the water at any one time

So each blade [75x18 = 1350 mm] - 18 for the 6mm triangle = 1332 sq mm per blade
Let’s also simplify the calculation & assume that three blades are doing equal work irrespective of their placement in the wheel [one digging in, one pushing & the last lifting]......
1332 x 3 = 3996 sq mm of blade surface area on each wheel  = 7992 mm total surface area to propel the vessel
So 7992 sq mm of surface thrust x the RPM x the block co-efficient of the hull will determine vessel speed  .......

I think this just highlights & confirms the points made below  ...but we also must remember that paddlers are not speed boats.....Derek 

[bill stafford]

gday derek , thank you for a very interesting info on paddle wheel design ,thats my concern
i am wary of building some paddlers now , the oscar-w has a wide wheel , but small diam.,it is possible that the width of the wheel will help a lot ,but i have observed the difference in model performance between my paddler and Adelaide , mine has 3 floats in the water at any 1 time also ,although i suspect , not as deep as adelaide , due to the smaller diam.,130mm approx. .
when i first got the model wet , it was hopeless,hardly any thrust to drive model , so i lowered the paddle wheel shaft ,until the top of the floats were at least 5mm under the water line at rest , completely different vessel now .
we have a adelaide in w/bool in 1/24, same as my paddler , and it seems to run easier than mine ,i suspect the hull shape of mine isnt helping , rather bluff in the bow area .most on the Murrey paddlers had , long , tapering bows ,this seems to make the hull more slippery .
this is why i suspect that the diam. of the p wheel helps drive+the number of floats+what about the width of the floats ?? also the depth of the blades ??
a lot of theory , and questions , model versus full size  regards bill s

[derekwarner_decoy]

Bill...I also have the Australian drawn 1:24 plans for Oscar W

Just yell out if you could use detail the wheel diameter x width & blade height & approx. immersion depth etc.............I don't think I would be breaching copyright law  .........Derek

[bill stafford]

gday derek ,

 thank you for the help and advise , i do have the plan as well , first i need to build the rodney , or rather get the spare time !! it will come , in time .
i have most of the details worked out +some mechanical parts .
i am also collecting bits for the adelaide in same scale +i have alum. paddle wheel rims cut out by laser cutter
i am wary of building a new model ,and suffering from lack of thrust ,hence the guarded concerns about p wheel diam.
regards bill s