Paddle Wheels Question

[kazarka]

I have introduced myself and my project (restoration to fully functioning, a model of the PS Lucy Ashton) via the appropriate forum and have had a good 'ferret' here before asking this question so I hope that if it has been asked before you'll be 'gentle' with me.

My model was scratch built and for this reason the paddle wheels have fixed rather than feathering blades.The wheels are 100mm dia by 55mm wide, is there anywhere I can get such wheels as a kit or complete? Are such small wheels an impractical size to construct fully feathering blades?

I'm also trying to establish whether the current maximum rotation speed (approx 80 rpm) is 'correct'. Is there a standard formula for 'slippage', I can calculate the forward motion from 80 rpm were the model on rubber tyres on tarmac but I'm scratching my head a bit here

My thanks for any advice

[PeeWee]

Hi,
Try here http://www.clydemodelboats.co.uk/userimages/Paddle-Wheel-Kits(1698849).htm i have a couple of sets and they are good quality.  on the rpm, rule of thumb i aim for 120-150 rpm for max scale speed with about another 50-rpm in reserve for emergency avoidance.     never fully trust others are paying attention.

Never worry about asking a question, we are all here of the enjoyment of the hobby

[kazarka]

Many thanks for the most enlightening response, just my luck Clyde seem to be re-building their website so no pics, I'll fire off an email as they don't give dimensions and it apears most are designed for a 5mm shaft, mine is currently 1/8" (3.2mm)

Motors are currently driven from a 6v battery via a pair of ancient speed controllers (see pic), the radio being a '60's MacGregor Diggimac 111A, Right and left vertical sticks control speed, left stick horizontal controls rudder. So, whilst the system is in theory 'proportional' in practice there are around 5 'steps'.  I assume going up to 12v will double the speed? If not I'm going to have to re-build the gearbox which I may have to anyway owing to drive-shaft size   Just when I'd constructed a set of outer shaft bearings too!

[mjt60a]

....just my luck Clyde seem to be re-building their website so no pics....

I wonder if this would be any help - http://www.paddleducks.co.uk/smf/index.php?topic=3503.0
not 100 per cent certain but I think these would fit the Lucy Ashton with the outer rims left in place...?

edit; Ooops, my mistake, those were not 'clyde model boats' wheels but 'waverley models' ones ..

[Talisman]

I'll fire off an email as they don't give dimensions and it appears most are designed for a 5mm shaft, mine is currently 1/8" (3.2mm)

Hi,
No email received as yet but if i can help ...

I'm working on the assumption you need 8 Float Rimless wheels...

Yes they are designed to accept 5mm Dia Shaft .. Personally i think 3.2mm might be a little to light.

Not an excuse but a bit of info ...
I can't give a dia of the turning circle as when feathering the path is not a Dia. it is more an elliptical circle the floats go through.

My site is somewhat neglected but Help is only an email / Phone call away.

Anything else just ask.
Regards,
Kim

[Talisman]

....just my luck Clyde seem to be re-building their website so no pics....

edit; Ooops, my mistake, those were not 'clyde model boats' wheels but 'waverley models' ones ..

No problems Mick.

Yes, Waverley Models also do feathering paddle wheels
&
Barry does wheels in Styrene. (Listed in Traders Area)

Now that has got to be a fair posting?

Regards,
Kim

[derekwarner_decoy]

Hi PD's...... .. I must be diplomatic here 

I have purchased a set of styrene wheels of the manufacture noted here & found the quality to cost excellent 
I have purchased a set of brass wheels of the manufacture noted here....& whilst the quality of the laser wheels is excellent....providing a bolt kit complete with M3 bolts for a 1:24 scale vessel is questionable 

An M3 bolt @ 1:24 scale is 76.2 mm [approx 3"] shank/thread diameter...this is grossly over scale by 200% 

I have four wheel disks but these have hundreds of 3 mm clearance holes.....so are in my scrap bin 

Reading the previous specification on 1:24 wheel kits from Clyde Model Boats ........from memory suggested the bolts were 12BA........which is 200% better scale representation than the rubbish I purchased

I have no association with Clyde Model Boats  however do not need to see any member fall into the trap of grossly overscale  bolt & nut components for wheel kits..........Derek

[PeeWee]

Hi All,

here is a link to my MoL photo album.  There are several picturs of the clyde wheels and bolts.  i can confirm that they are far samller than M3. 
http://s716.photobucket.com/albums/ww169/peacocki/MOL/?start=all

[kazarka]

Thank you all for your comments . . . . I was in the middle of emailing Clyde Boats when I got a phone call to say the drawings from which the model was constructed 25 odd years ago had surfaced !  I'm collecting them tomorrow then I'll know exactly what's needed.

The pictures of the wheel construction were most helpful, I also take on board the advice on shaft diameter. Having examined the gearbox I've come to the conclusion that matters are not helped by it being a wee bit 'flimsy'.  I've also been thinking about bearings and whilst it's no doubt important to have some form of bearing between the inner paddlebox wall and the hold for waterproofing. with a rigid shaft is an outer bearing really needed?

I'll await the drawings but I'm tempted to re-construct the gearbox in a more rigid form and fit 5mm shafts. I'll photograph the construction which should give you lucky guys with lovely workshops a bit of a chuckle !

Attached, a couple of pics of the current gearbox.

[mjt60a]

....with a rigid shaft is an outer bearing really needed? ...

...a thought has just occured to me...just took a look at the pics of Lucy Ashton in the 'introduce yourself' thread...
I see the shaft passes into the outside edge of the paddlebox/sponson. now, if you intend to use feathering wheels, it won't be possible to have a shaft bearing there as the feathering rods cross it, you'd have the bearing for the centre of the feathering gear just slightly forward of the old/existing shaft bearing....

...I never thought to photograph that part of the setup so I've looked for a picture to illustrate it and the best I can find is this - http://www.paddleducks.co.uk/smf/index.php?topic=5011.75 - (scroll down a bit)  This thread is quite interesting to read from start in its own right anyway 

[mjt60a]

...this picture of the graupner plastic paddlewheel shows why the paddleshaft cannot go through the outside edge (of the paddlebox) the white part has to be fixed to it slightly ahead of the paddle shaft - http://www.westbourne-model.co.uk/acatalog/Graupner-Paddle-wheel-set.jpg

[kazarka]

I'm flabbergasted at the wealth of friendly help from this forum, thank you Mick, Ian, Derek & Kim.  Thanks to the pictures you've linked I now understand how the 'feathering' system works and most importantly the reasons for having a much more substantial and rigid drive shaft. It's also now clear that the holes in the outboard paddle cover were merely to facilitate fitting/removal of the paddle-wheels.

I collected the plans last night but they were not of the Lucy Ashton but of the Duchess of Fife. It appears they were bought for the detail on feathering wheels as with them was a re-scaled drawing for the LA wheels drawn by my late Father. My guess is that having built the boat his failing health and desire to see it in the water prompted the decision to abandon the feathering wheels and opt for the quicker and easier option of fixed blades. I also discovered (by 'lubricating' my dear old Mother with more whisky than is really wise) that when he first started the build he had access to a set of actual 'blueprints' which had to be returned somewhere after 2 weeks. More interesting is that whilst the fixed wheels currently on the model are 100mm in diameter, the drawing he made was for rims of 108mm dia with the blades just within (105mm). My guess is this is the 'scale' size so I'm going for as close to that as I can find.

First step is to remove and re-build the gearbox with 5mm final drive shafts through roller bearings and add bearings to the inner wheel case. I'll take some pics and post as I go along.

Again, a big thank you. 

[ophicleide]

I've followed this with interest, having spent some time a few years ago doing research on paddle wheels and the testing of self-propelled models in the design of full-size paddlers, most notably by Denny's of Dumbarton. 

Standard practice is to multiply the rpm of the real ship by the square root of the scale to achieve a proper scale speed (i.e the speed at which the model will produce the same wave effect in miniature as does the real ship).

So for a model at 1:48 of, say, the current Waverley, the following would apply:

Maximum of Waverley's engine (in 1947) = 56rpm. Square root of 48 is 6.93. 
Model maximum rpm therefore 56 x 6.93 = 388 rpm.

Waverley's service speed rpm = 42.  Model equivalent is 291rpm.

These of course are rpm in the water.

I applied this to my models of Waverley and Cardiff Queen (Cardiff Queen rpm for real ship maximum/service was 52/45, which works out at 360/312 rpm for the model at 1:48 scale).  Both models have scale feathering wheels. The result appears to prove the theory, as the wave pattern is correct.

The same formula works in reverse to work out what the scale speed should be (i.e. divide the speed of the real ship by the square root of the scale).  So again at 1:48, 18 knots becomes 2.6 knots for the model; 15 knots becomes 2.16 knots.  In theory, if a model is accurate, it should perform predictably.

I attach some photos of the models at roughly "service" speed which may be of interest.  I've tried to choose shots that show the wave pattern produced.

I've been following the forum on and off for a while; this is the first time I've got off my backside and posted. Thanks for the encouragement!

There's also an article on similar topics, but regarding model aircraft, here:   

http://www.astroflight.com/pdfs/ScaleSpeed.pdf

[derekwarner_decoy]

Hi PD's.....& welcome ophicleide  ...I like your mathematics ...it is always good to see a new member with an insight to these important points

As time progresses....please tell us more about your model vessel interests....... .....Derek

[Spankbucket]

...and do I detect an interest in the history of early tubas??