hello

[capnbob]

Hi Paddleducks,

I have been infatuated with paddle boats for quite a while.  I prefer the working boats, like the towboats and pool boats, as opposed to the fancy boats that carried passengers.  The stern wheelers I have built have all been static except for the last.  I built a scotch yoke mechanism in it so the pitman rods would drive the wheel.  On my next stern wheeler I would like to drive it with a steam engine that is similar to the engines in real boats.

On YouTube I found these two engines.  The first seems to be very extensive and accurate but also much more than I need.  ( http://www.youtube.com/watch?v=p0OmPBQMUXU ).  The other ( http://www.youtube.com/watch?v=-qhrSHaOU0U ) is more like what I am looking for but the dimensions are not at all to scale.  In farther searching, I have not been able to find plans for any engine that is suitable to put into a sternwheeler.

At a different forum one person was telling another that Paddleduck might have the plans he was looking for.  So I thought maybe I can find plans for the engine I am looking for.  If not at least I’ve found a forum that looks like it will be fun to be a part of.

Glad to be a member.
Bob

[derekwarner_decoy]

Hi PD's....& welcome Bob......

 ....from the two examples you have shown....one is a true scaled engine & drive system....and the second is shall we say a generic representation

Q1....do you plan to build your own engine & drive system?
Q2....do want to build the true scaled version?...or would the generic version suffice?

Remember life in the modeling world can be a series of compromises & depends on your final decision of choice

Anyway there are thousands of pages & articles to view & read....enjoy your stay.......& keep us posted with your thoughts or questions

A member from our world wide group will respond to any paddler question....Derek 

[kiwimodeller]

Welcome aboard Capnbob, I am sure you will find on here all the help you will need and a lot of pleasure from the discussions. Do you think you could post some photos and/or drawings of the Scotch Yoke you built. Did the design come from plans or did you design it yourself? Already on the forum there has been a lot of discussion about designs for drive systems for sternwheelers but there is always room for more ideas. I have a steam powered side wheeler with chain drive to the wheels and now I am starting work on a sternwheeler. I would like to use an authentic horizontal twin engine but I do not have the facilities or skills to build an engine myself and the only commercially available one is rather expensive. At the moment I am contemplating using either two single cylinder engines linked together or else the PM Research double acting V Twin which I have had good experience with in other boats. I would like to be able to drive a countershaft by chain to get the gearing right and then run links to the paddlewheel shaft so it looks authentic. Look forward to seeing your ideas. Regards, Ian.

[capnbob]

Thanks for your welcoming.

Derek,  The steam engine in its basic state is the cylinder, valve and pitman.  Then you have many valve linkages to control the steam.  The valves seen most in riverboat engines are the poppet valve.  This was used in the first video.  Some smaller riverboat engines used slide valves operated by cams, as in the second video, or eccentrics on the wheel shaft.  The second is much easier to build.  But the model being displayed is way out of scale.

As far as building.  I do not consider myself a machinist but I do hope to build as much as I can.
Kiwimodeller,    You seem to be in the same predicament I am in.  I am thinking of using two slide valve engines, as in the second video with two eccentrics on each side.  But have the eccentrics inside the engine house instead of on the wheel shaft.

The pictures are of the scotch yoke.  Years ago I read an article about the problems of running two scotch yokes 90 degrees out of faze.  Basically it said that if everything is tight the mechanism will lock up.  It went on to show the math and how much slop is needed.  The article is long lost so I opened up the width of the channel the crank rides in until it ran.

[capnbob]

Lets see if I get the pictures this time.

The bell crank on the end of the shaft has a bearing on the end that rides in a vertical channel.  The channel is attached to a square tube that runs horizontally.  This is attached to the pitman.  The two sides are 90 degrees out of phase. 

Bob

[kiwimodeller]

That is great thanks, nice clear photos and a simple mechanism. I understand about the need for a bit of play to eliminate tight spots and about the arms being out of phase. I presume that the arm length off the counter shaft and the length of the arm at the wheel shaft need to be the same? Can you tell me the centre to centre lengths of the arms please. The rest I should be able to work out. For mine I am tending towards using the PM Research twin because it is very controlable and reliable and many paddlers did use oscillating engines. I like the look of your belt drive too so that is something else for me to investigate. Cheers, Ian

[capnbob]

This boat was the start of the W.P.SNYDER Jr. that I never finished.  So the crank arms are 7/8" to be 1/48 scale.  It really doesn't matter what the length is as long as all four arms are the same.  Also the pitman arm should be at least nine times the length of the the arm for ease of operation.

Bob

[PeeWee]

Bob,  a belated welcome from me.  those pictures show a very nice arrangement for the stearnwheel mechanism.

Ian, on the PM do you mean http://www.pmresearchinc.com/store/product.php?productid=3091&cat=4&page=1  i have one of these in my workshop ready to be built.  hopefully this year sometime 

[capnbob]

PeeWee,
Is that PM engine reversable?

Bob

[kiwimodeller]

PeeWee, the engine I intend to use is the V Twin
http://www.pmresearchinc.com/store/product.php?productid=3650&cat=4&page=2
I have used them before and sold them to friends in our club, all of whom are still friends and happy with their purchases. Have not tried one in a paddler yet but I fitted one to a Kingston Mouldings Steam Yacht Tender which is 42" long and the 9" beam. At 40PSI it would push that along at way over scale speed on half throttle so it has plenty of power. Its advantages (as well as the power) are price, compact size and the fact that it can be throttled and reversed by one servo. It is also very controllable and will go down to a gentle tickover. Like all oscillators it does leak a little steam out of the faces but that improves as it is run and settles down. The engine you suggested looks great but it is fairly large and I believe it does not have a reverse valve although an external control could possibly be fitted. The other alternative I had looked at was using two of their 2A single cylinder oscillators. These are very cheap even for the machined kit and could be mounted horizontally with a coupling between them and the drive off the centre. I did have two set up on a base and got a valve from Dream Steam but before I got around to putting them in the hull somebody saw them and bought them so I think I will just go for the V Twin with chain or toothed belt drive to the countershaft.
Bob, thanks very much for the info about your drive, it will make life much easier for me. Cheers, Ian.

[PeeWee]

that V twin makes far more sense.  whilst i am looking forward to making my twin, you are correct in that it does not have an inbuilt reverse valve.  i would also need to use a different base as the one supplied is way too heavy for a model.