differential paddle drive

[sonofpincher]

I am new to the Forum, and not as expert as many of you Members, but have made two "paddlers", the first being Richard Webbs "Princess Elizabeth" in styrene, and the next a freelance paddle tug, both electric drive.  On both, I have used an RC car rear axle for the paddle shaft, complete with differental, and on each half of the axle, mounted styrene discs which are contacted by "braking" plates, linked to the rudder servo.  This may not be new to you all, and I'm sure someone has tried it before, but other Paddle enthusiasts I have spoken to at Boat Shows, suggested that it was new to them.  A description and photographs were published in the Dec. 2009 issue of Marine Modeller International.  It certainly works well, and greatly improves steering , especially going slowly. The useful characteristic of a diff. is that when the inside wheel is slowed or stopped by the brake, the outside wheel revolves twice as fast!

[derekwarner_decoy]

Hi PD's....& welcome sonof...... ...certainly in my 10 years @ Paddleducks......quite a number of members have considered differential drives....split drives...twin engine...twin steer paddles.....all basically for improved steerage

Over the years post WW1....a number of British naval tug's were designed with independent paddle drive [Director Class], however much earlier the British Board of Trade  outlawed such devices for open sea work....as they had the potential to allow one paddle to dip into the water & never self wright the vessel....with the loss of life  on a number of occasions

Think of the simplistic scenario... ...the paddler is on a straight course...(neglect swell, tide or wind)....if the port paddle were stopped/locked...the vessel would attempt to pivot on this locked port paddle & turn to port irrespctive of the rudder command

The next action is for the STDB paddle to overspeed  .......& then everything just gets worse.....Derek
 

[R.G.Y.]

Sonof, Go on with your experiments. Experts have been proven wrong many times through out history. We are only scaling the model not the elements so have to cheat all we can.  My prefered method to improve both stability and maneuverability is a removable bow rudder. Made of lead about an 1.5ins deep and 6ins long(on a 5-6ft model) pivoted just forward of center and considerably thicker in the forward section. This will transfer weight to the inside of the turn preventing the outside paddle digging in. Best of luck R.G.Y.

[Stuart Badger]

This is a knotty subject - and recurs from time to time on this forum. It is often stated that "there is a Board of Trade regulation" etc regarding passanger vessels/open sea work - THIS IS NOT SO.

The simple reason for tugs having (at times) uncoupled/coupled twin engines is that they often had to exert maximum power while having no steerage way. To make that power directional - without the help of propwash over the rudder, two engines were more often than not employed. The paddles being coupled or uncoupled together depending on need.

The reason for passanger vessels to have a coupled (or common) paddle shaft was because they never found themselves in those circumstances. At higher speeds under rudder steering or in 'dirty' conditions a paddle could dig in or come clear of the water. This would more often than not result in a fractured paddle shaft. This was expensive, difficult to repair and resulted in high claims against the owners of the ship. But it made far more economic and practical sense to usually stick to one engine and one shaft.

The reason for coupled paddles on passanger vessels was economic practicality and no other.

There is no record of any paddle driven passanger vessel capsizing due to the employment of either twin engines, an uncoupleable shaft or turning under paddle power alone.

All the best

Stuart

[derekwarner_decoy]

Hi PD's.....mmmmmmmm  ....I was simply posting from our old Yahoo days...example here is from June 18 2005 from our archives....but there is more on this discussion subject...........in the Search Box....try Twin Paddle Drive ......Derek


...... prototypical engine configurations of historic paddlers and it's been a source of many emails and  ............  Parliament which prohibited the use of any split drive for a paddle steamer carrying passengers and/or  ............  as to why). I'm not sure if this also applies to paddlers on the Murray, but perhaps "Capt. Dennis" (Kerr)  ............  hand, British Paddle tugs have certainly used twin engines with independantly driven wheels and my  ............  "Pert" and "Cracker" which both have independant drives to each wheel.  David...could you please take a  ............  through P.N. Thomas and see if we can find any twin engine shafts that look like they may be " ............ . >From my studies it would seem that if a tug had twin engines it could easily connect the two shafts  ............  harbour water). There were some accidents when a twin engine ship with disconnected shafts, rolled  ............  ships were built with easily disconnectable twin engines. Some have a coupling of some sort in the  ............  memory!! Most tugs were too small to squeeze twin engine into!!! It should be remembered that most  ............  come into its own. I believe that relatively few twin engine tugs were built. Cue the John H. Amos. She  ............  at both ends. She had a bridge set in between the twin (fore and aft) funnels and appears to have been  ............ . If I remember rightly, the old ferries (not paddlers though) that used to run across Auckland harbour ( ......

[Stuart Badger]

As I said Derek this 'myth' has been discussed again and again here. Apart from the very early days virtually ALL tugs had twin engines and a dog clutch system of connection/disconnection. As to the parliamentary 'regulations' I am assured by the Board of Trade and Hansard that no such legal regulation/requirement exists or has been discussed in the british parliament. As to the lack of room - most side lever engines (the most common variety used in tugs) were on average about 5 to 6 feet wide - so plenty of room for two. Most Paddle Harbour tugs after about 1870 had twin engines.

I have spoken to the BoT, Hansard and (my favourite) the engineman of Reliant when she was based at Seaham he had many tales to relate about the use of the dog clutch!

All the best

Stuart

[Eddy Matthews]

I know that Walter Snowdon has looked into the topic of a "Board of trade regulation" extensively, and he has found no evidence of such a regulation, so as Stuart has said, it appears to by a total myth with no basis in truth.

Regards
Eddy

[sonofpincher]

Well-- my description of the use of a model car differential to help two of my MODEL paddlers perform-- seems to have sparked a discussion about Board of Trade regulations.  I am glad that I don't have to fear a B of T Inspector coming down to the pond!  I was merely passing on something that has worked for me, and wondering if anyone else has tried it in a MODEL boat.  If they want more info. I will be happy to describe the system in detail -- but can't comment on what great big REAL boats do!

[derekwarner_decoy]

Hi PD's.....well sonof....go for it & post the ......the "system in detail"    please also add some too........Derek

[R.G.Y.]

Sonof, I am sure I have seen your device posted somewhere before? I thought it looked very promising. R.G.Y.

[Tug--Kenny]

Hi Sonofpincher,

I've built a Springer type of craft in the style of Waverley and used a car differential to power the paddles.  see pics below.

My reasoning was that if one wheel caught any twigs in the pond then the other wheel would speed up and turn the craft around and dislodge the debris. I never got around to proving this and found she sails well.

 As I only have one motor then I could not control one wheels speed against the other. She does however 'corner' better than conventional paddle wheelers as the bulky sides do allow the force of the water to be directed along the side of the ship rather than digging in and forcing her sides up or down.

Have a go and let us know your results please.

Ken

 

[sonofpincher]

Unfortunately, i have tried and failed to post pictures showing my two versions of the differential paddle drive system.  I am not an experienced modeller, and even worse at manipulating computers!  I was told by the Forum computer that I had exceeded the 500mb limit for pictures, but I cannot work out a way of reducing the images to the approved size.  So, if I don't work out how to do it, anyone interested can see a view of one of my boats if they can find a back-number of the Dec 1009 MMI

[Eddy Matthews]

There are numerous ways of reducing an image size - Just a few are discussed in detail here: http://www.paddleducks.co.uk/smf/index.php?topic=2656.0

Regards
Eddy

[pete]

Interesting subject! I have tried differential paddle drive on the 2 model paddlers I have built so far.
The first (Waverley) used a micro-switch to cut power to the inside paddle when full rudder was applied. This caused a massive heel towards the running paddle and had no apparent effect on the radius of the turn. If used with no forward speed on the vessel - heeling was all that happened.
The second and current model (Talisman) uses two speed controllers to separate motors for each paddle. Heel is no longer a problem, - probably due to a lighter superstructure and the paddles being spaced further from the hull sides. However, the results are not impressive. Slowing,stopping or reversing the inside paddle in a turn has little apparent effect. Running one paddle ahead and one astern whilst stationary will turn the boat in it's own length but only if it is flat calm with no wind and you have 20 minutes or so to spare!!
In summary, at a given scale, a model with a short hull ( say a tug) will benefit from independent drive but a long hulled vessel ( say a passenger steamer ) will not due to the extra resistance to the beam.

[derekwarner_decoy]

Hi PD's ...& welcome Pete ...we have not spoken before

EDDY...there are no text options or similies......!

Sorry Pete....your comments are very interesting .....please post a few .jpgs of your vessel/s build/s....Derek

PS...I just added the attachment to see if that was working.......