Paddleducks
Paddler Modelling => Paddlewheels/Drive Systems => Topic started by: Broder Incertus on October 12, 2013, 08:00:01 PM
-
Greetings,
I seem to have misplaced this piece of knowledge since my last paddler too many years ago: what's a suitable paddle rpm? "It depends" I guess is the appropriate answer, but assuming Graupner paddle wheels or something of a similar size and a Glasgow sized tug? Something in the neighbourhood 150 rpm seem to be recommended, but the John H Amos in a recent issue of Model Boats apparently run well with 200–250 rpm, and IIRC someone's Aussie paddler required 300–350 rpm not to be blown backwards by the wind.
tia/tm
-
gday ,
you may have read my post about aussie paddlers needing 300-350 rpm .
I stand by that ,as most paddlers need to be able to generate forward motion , to steer , and not enough revs doesnt help .
paddler hulls do funny things , my hull does reach a "perfect " speed , were more revs does increase thrust , but also bubbles and reduces efficency.
i normally throttle back to about 250-300 rpm , and save the flat out speed for windy days , its hard to explain , but all hulls have a maximum speed , and they dont like being driven over this .
i also tank steer my model on windy days , and this has saved me from many a rescue .
i stand by my recomend of 300-350rpm , for side wheels paddlers , the set up can be tuned by different motors ,555 approx. 4500rpm,jaycay 2718 8/9000 rpm, speed motors up to 1500+rpm .
regards bill s
-
British paddle steamers late 19th early 20th ( sea going passenger ships) max revs 45 rpm. I find 100rpm works on my models. all depends on the hull shape.
-
Hi.
on my paddleboats i try to have around 150rpm max and this is so far enough some times on calm water i can sail my Glasgow with about 30 - 40 rpm.
greetings Hans.
-
gday ,
you may have read my post about aussie paddlers needing 300-350 rpm .
…
regards bill s
G'day,
That's the one!
-
OK, given the various data point, I guess the only way to know is to try and see if it works (and something like 150 to 200 at full throttle should work, at least as a first approximation, and with ESCs with good slow speed control).
/tm
-
this is what I found with one of my models, a 24 inch long hull, 4 inch beam, not particularly streamlined bow (it's a tug) 85mm dia wheels, 8 floats, non feathering, floats are 25mm width, 10mm height, max speed 160 rpm....
model perfprms very well up to around half throttle, any more and the wheels turn faster, produce a lot of splashing and bubbles but no increase in forward speed at all.
I suspect the reason is that eight floats on such a small diameter wheel means they are quite close together and 'clear away' the water below them faster than it can flow back.
I also have a PBM Edwardian model (35 inch by 4, I think and more streamlined shape) similar power, weight and wheel diameter but six floats per wheel - and it's much faster! and can run at full throttle without this cavitation happening. The hull shape probably helps with the speed but I do think the extra 30 percent-or-so space between floats plays it's part...
...I haven't yet tried building some 6 float wheels for the tug to see if it improves performance (or not) but I did meet a modeller at the kew bridge show who did that on his own model and told me it does.
maybe something to consider....