Constructing a paddlewheel?

[Eddy Matthews]

Hi Guys,

I've decided my next project will be a sternwheel towboat called the "Suter" - A photo is attached.

No problem with the basic boat, but this will be the first model where I need to make a paddlewheel - So can anyone give any tips on how to go about it? Are there any pitfalls I should avoid? Basically ANY help would be appreciated! :-)

Regards
Eddy

[mjt60a]

This is one for Towboat Joe, I'd say  

[towboatjoe]

For beauty there's nothing like making everything seperately and then glueing it all together. It's time consuming to build wheels, especiall when you need several exactly the same. It's best to use a good tight grained wood for strength when making the arms and carving out a flange.

I build a lot of models and always looking for shortcuts to speed up the building process. When I did the Lady Lois I made one form of a wheel with the flange, arms, iron circle, and blocking. Then I made a mold of it and poured five resin copies. For realism you can glue pin heads on the arms at the flange and iron circle to look like bolts.

[Eddy Matthews]

Thanks for that Joe.... Do you, or anyone else reading this, happen to have any photos of a wheel taken during construction? You know the old saying, a picture is worth a thousand words!

I like the idea of making one wheel frame and using that as a pattern to resin cast the five frames that I need - sounds like a great idea to save time AND get 5 frames that are identical!

Regards
Eddy

[Khephre]

Joe,

I was very interested to read that you'd cast a set of wheels - flanges, arms, etc. - in resin. My immediate reaction was to worry about whether the resulting castings might be too brittle for the intended purpose.

Did you reinforce the castings at all? Make the arms over scale thickness? Or does the final assembly process strengthen everything up?

Many tks
Tony
Akl, NZ

[towboatjoe]

Eddy,
I don't know if I have any photos or not. I could see if I could dig up the old mold and see if I can cast one. Here's a drawing that gives the details of an old stern wheel.

[towboatjoe]

Tony,
I use a casting resin sold at Micro Mark. It's not as brittle as regular resin and dries white. Parties interested in making accurate stern wheels here's another drawing to go with the drawing in above post. This one shos how the flange is made and coupled to the shaft.

[Eddy Matthews]

Thanks Joe, actually I'd never realised that the flange was a cast metal part - I don't know why, but I'd always assumed that the whole wheel was made of wood with metal bands around the rings, so your drawings have clarified a great deal as far as the details go!

Are the iron circles fitted to both sides of the wheel or only on the side that the spokes go?

Regards
Eddy

[towboatjoe]

On the old wood wheels, the iron circle is on both sides sandwiching the wood circle parts in between with bolts to hold them in place. On newer wheels the arms were made of steel and the iron circle was bolted, riveted, or welded on one side to the arms.

The Lady Lois (photo below) has four wheel assemblies. Notice the port two face inward on the flange and the starboard two face inward. "C" iron was used for arms with two iron circles. This vessel was built by Nashville Bridge Company in 1929.

[towboatjoe]

Well, I looked around the work shop and found I was out of casting resin, but I did find the old mold I made a few years ago. It's a little worn for wear, but you can grasp the idea. Since there's so many nooks and crannies for the resin to pour in, I opted to pour the resin directly onto the mold and then place the top art on for it to set up instead of using a pouring hole. It creats some flash, but no problem for an x-acto knife.

[Khephre]

Many thanks Joe,

I've checked out the Micromark website and found the high strength casting resin you refer to.

Reminded me of just how starved we New Zealanders are for good modelling materials!

Your drawings are also much appreciated and have already gone into the filing system.

Tks again
Tony
Auckland, NZ - where it's only 28 degrees C this morning but a whopping 95% humidity - like walking in warm soup!

[Eddy Matthews]

Thanks Joe,

Another couple of questions now spring to mind - bear in mind that I've never done any resin casting before! So these may be silly questions!!

Once you've made the "master" to make your mould from, does it need to be coated with something to stop the rubber mould material from sticking to it? If so, what do you use?

And in a similar vein, when I've made one half of the mould, do I also need to use some sort of release agent on that so that the top half of the mould doesn't stick to the bottom half?

I hope that makes sense? I know what I mean, but I'm not sure if it comes across clearly in text!

Regards
Eddy

[towboatjoe]

Absolutely! You'll want to brush on "RTV mold release agent" into the mold and on the halves that will go together.

Also when you make your master plug, you'll want to seal it good so the RTV mold material won't "grab" onto the plug. You'll want to coat the plug good with release agent before poring the mold too.

It's amazing how those things can seem to bond permantly together.

The way I made the wheel mold was to build a shallow box that the wheel would lie in and after I coated the wheel plug with release agent, I used four modeling pins to hold the wheel about half way from the bottom of the box. I then mixed the RTV mold material and slowly oured it till it was even with the top of the wheel and let it set up.

After it had cured, I cut alignment knotches in the mold so I could easily align the top part with the bottom part. Then I brushed release agent over the entire top of the mold, sides of the wooden box, and wheel plug. I then mixed some more RTV mold material and pored over it till it was almost to the top. To add rigidity to the top of the mold, I laid a piece of bass wood that just fit into the top of the box as it was curing. The top of the mold adhered itself to the bass wood when it cured.

After it all cured good, I carefullt removed the top, took out the plug, and now ready to brush on release agent and mix some casting resin.

[Eddy Matthews]

I can't see how your mould works Joe..... If you pour the bottom part (which is almost the entire thickness of the wheel frame), and then put the top part of the mould on, surely that will just trap air so all the detail of the top will be lost? Unless you have some small holes to let the air escape that aren't visible on the photo?

Sorry, but I'm a little confused.... Hey it doesn't take much to confuse me! :-)

Regards
Eddy

[towboatjoe]

It's not like pouring a mold with depth to it that will get air trapped in it. You have to slowly pour it around the impressions of the arms and rings where it will be even to edge of the mold. You could leave off the top part, but the resin has a tendecy to to make the edges of the casting round, to where placing the top of the mold on will help it have some flatness. The bottom mold is the thickness of the wheel frame.