Feathering paddle wheel construction

[waldenmodels]

After a couple of false starts, I was actually able to draw a 14-float feathering wheel. No clue if it works. Can anyone see anything obviously wrong with it? Either way, I'll make a paper mockup to see if the mechanics are correct before I go any further...

Cheers,

Oliver

[mjt60a]

Looks OK, I'm guessing it's for Connaught? Remember though, one of the rods is thicker and does not pivot at the center, this is to pull the centre disc round otherwise the wheel would move around it until all the floats are facing out and the slack in the mechanism is taken up, then it will rotate but would do no good!
see the pic of the science museums model...

[mjt60a]

...the 'graupner' wheels for the Glasgow paddle tug use a similar arrangement, it isn't thicker but is moulded firmly onto the centre disc, and for the same reason...

[waldenmodels]

Thanks, guys, you're absolutely right - the "Driving Rod" is fixed. I've been using one of 19th century treatises on designing paddle wheels to construct this - it all kinda snaps into place once you've understood the principle involved.   It also appears that with the same basic geometric principles you can produce a wheel with any number of floats. Interestingly, there was some discussion here about whether the eccentric axis is higher or lower than the wheel axis by a smidgen. I discovered in drawing the wheel that it naturally came out that way.  I think I can improve this a bit further, i.e. make the floats to the left and right of the bottom float be more vertical. Can't wait to build one!

Cheers,

Oliver

[Stuart Badger]

Hi Oliver

this is a picture of one of the paddle wheels on my model of 'Old Trafford' the round arms on the eccentric wheel are the pivoting ones - and the flat arm (on the left slightly lower than centre) is the fixed actuating arm. Hope this helps. Just one small point - the eccentric hub should always be FORWARD of the paddle shaft.

Stuart

[waldenmodels]

Thanks, Stuart - here's a question: Is the eccentric axis on your model fixed to the paddle box, i.e. does it float in space here because the paddle box is not installed?

Cheers,

Oliver

[Stuart Badger]

Quite right Oliver! - the paddle boxes and sponsons were not installed when the photo was taken. Here's a shot of the complete mechanical installation. the eccentric is attached on a stub axle to the paddle box beam.

Stuart

[derekwarner_decoy]

Hi PD's & welcome Oliver to the question of feathering paddles

The attachment [PS Waverley - DRG No PW6] was downloaded some years back, but clearly***** shows a positave height differential 'dimension' between the paddle axis & the fixed eccentric axis

Pity we cannot read such dimensions ........Derek

[Eddy Matthews]

The drawing Robert McLuckie sent clearly shows the Waverley's paddlewheels, you can find it at: http://www.paddleducks.co.uk/index.php?ind=downloads&op=entry_view&iden=808

The difference in height between the paddleshaft and the eccentric is 2 inches....

Regards
Eddy

[kno3]

Quite right Oliver! - the paddle boxes and sponsons were not installed when the photo was taken. Here's a shot of the complete mechanical installation. the eccentric is attached on a stub axle to the paddle box beam.

Stuart

What a beautiful engine and paddlewheel! Congratulations. Looks Like Cheddar oscillators?


I have a question: is it possible to do away with the master rod and have the eccentric disc turned by other means?

[waldenmodels]

@kno3 - Buna Ziua!

Though I don't know much (yet) about the the mechanics, I think that might not be practical. For one, you would have to make sure somehow that the two drive systems stay in synch at all times. And if the eccentric drive should fail while the wheel keeps turning, wouldn't the rods get ripped apart?

Cheers,

Oliver

[Stuart Badger]

What a beautiful engine and paddlewheel! Congratulations. Looks Like Cheddar oscillators? (Yes they are!)


I have a question: is it possible to do away with the master rod and have the eccentric disc turned by other means?
[/quote]

In a word NO! 

There HAS to be a mechanical relationship principle between the paddle floats/angle of floats/and position on the circumference of the wheel for the floats to feather.

The system was invented in the early 19th century and is the most elegant solution to the problem of keeping the floats nearly vertical on entrance and egress to the water. If the eccentric disc was turned by other means ALL of the actuating arms would have to be solidly mounted to the disc. A drive system (as stated by Oliver) would have to be perfectly in sync with the paddle wheel at all speeds and all rotational directions. It WOULD be possible to achieve this with a set of gears between the paddle shaft and the eccentric disc using a driver, intermediate gear and driven gear from the main paddle shaft. Given the displacement between the two shafts these gears would have to be very small.

The beauty of the standard system is that there are no redundant parts, it is simple, effective and on the full size boats was very easy to manufacture using basic ship building skills.

Good design is about fitness for purpose - and on that basis the standard system is very nearly perfect.

Hope this helps

Stuart

[Walter Snowdon]

Hello Stuart. I like the neat chain drive. Is it metal chain and where did you source it from?. Walter

[Stuart Badger]

Hi Walter

The chain drive is in fact a miniature Delrin chain and sprockets. It's available from The Davall Gear Company of welham Green, Hatfield, Herts AL9 7JB. They are distributors for SDP/SI. They also do miniature metal genuine ROLLER chain! - at a price! They produce a catalogue that has absolutely everything you could ever need in terms of gears, chains, gearboxes, belt drive systems, bearings and mountings. The phone number is (+)44 (0)1707 283131. The manufacturers have a web site at   http://www.sdp-si.com/   Davall's web site is at http://www.davall.co.uk/  and you can purchase on-line.

Hope this helps.

Stuart