DRIVES & ENGINE
Well, here I go talking about a subject where I'm probably going to step on a few toes. For this, I apologize in advance. The reason that this subject is a little touchy is that almost everyone who has built a sternwheel boat has had their own ideas on the best way to drive the paddlewheel and what to drive it with. Now, not all of these ideas were bad and some were pretty darn good but, most builders are less than willing to admit that there are some shortcomings in their approach. Well, here goes.
I'm going to divide this page into two subjects. One will be about engines and the other about drives. First, the engines.
ENGINES
I'll begin by correcting a common mis-conception. Many people believe that all that is needed, to make a sternwheeler go faster, is a bigger motor. T'aint necessarily so! In the page about 'paddlewheels', I stated that the speed of a sternwheel boat is determined by the wheel parameters and the hull efficiency. Therefore, a motor that is powerful enough to overcome drive train losses and spool the paddlewheel, is as large a motor as the vessel needs. After all, once the wheel has dug a hole in the water, spinning it any faster will not make the boat go any faster. In many cases, the amount of horsepower required to drive a wheel is surprisingly small.
How much horsepower, you ask? Well, there is no precise way to determine the exact amount of power a particular paddlewheel can utilize. At least, none that I know of. I have, however, developed an empirical formula which gives pretty good results for most of the wheels used on live-aboard size sternwheelers. The formula allows me to calculate the power required at the wheel shaft to spool the wheel but, drive train losses still have to be estimated.
Let's look at an example. For a paddlewheel that is 10 feet in diameter by 8 feet wide with 16 inch buckets, 70 to 75 horsepower will spool the wheel. Even a good drive train will have losses in the 20 to 25 horsepower range. Therefore, I would install 90 to 100 horsepower to utilize the paddlewheel to its maximum. This is not a lot of power if you consider that the vessel could be in the 70 foot range and weigh 30 to 35 tons and cruise at 8 to 8 1/2 miles per hour.
One last comment about engines. I strongly recommend the use of diesel motors. They have far better torque to rpm ratios and, of course, they are much less of a fire hazard.
DRIVES
Over the years, many systems have been dreamed up to turn a paddlewheel. There have been drives that utilized an entire farm tractor mounted to the stern of a vessel. The rear wheels were removed and replaced with paddlewheels and this was the drive.
Others have utilized differentials from heavy equipment with paddlewheels mounted on the ends of the axles. Some builders have mounted sprockets on the axles and ran chain from there to each side of the paddlewheel. I believe that some have even used the entire drive train out of their brother-in-laws Buick Skylark that he wrecked on the way home from the pub.
Still others have used hydraulic pumps and motors to transmit power from the engine to the wheel.
All of these have worked with some measure of success. However, many of them have had definite problems. These problems ranged from required frequent maintenance, to frequent break-downs or just to difficult to operate.
I can't take the space required to discuss the pros and cons of every system that's been devised to drive a paddlewheel. Therefore, I'll restrict this page to a brief look at hydraulic drives in general plus the one mechanical system that I prefer.
First, my observations on hydraulic drives.
Many people, especially novices, feel that hydraulics are the only way to drive a wheel because it is so simple. All you need is a pump, a valve, a motor and some hose and you can put the drive engine anywhere. Unfortunately, there's a bit more to it than that.
First of all, most paddlewheels require a large amount of torque to operate them properly. Therefore, large pumps and motors are usually required to meet this need and these must operate at very high pressure to directly drive a wheel. These components are very expensive, usually require frequent maintenance and parts aren't available from Sears. Sometimes, smaller, less expensive and more readily available components are used. These can operate at a lower pressure, however, they need to be attached to a jack-shaft which has a chain running from it to the paddlewheel. This is now mixing hydraulics with mechanical drive components.
Secondly, remotely locating the drive engine usually means putting it down in the hull. However, most personal size sternwheelers have fairly shallow hulls and installing the engine there, along with the necessary cooling and ventilation, isn't easy.
Last but not least, I have never seen any hydraulically driven equipment that wasn't eventually covered with oil. It's a constant job keeping the engine room clean and oil out of the river. Personally, I don't like a dirty engine room.
By now, I guess you can tell that I'm not a great fan of hydraulic drives. However, to be fair, I must state that there is one more reason why I don't support hydraulics. That is, I know little to nothing about the engineering required for these systems. I will admit, though, that on smaller vessels with paddlewheels in the 6 to 8 foot diameter range, hydraulic drives can be used with a good measure of success. I've seen it done.
Now, let's discuss mechanical drives.
The system that I'm going to propose is certainly not the only mechanical drive system that will work on a sternwheel boat nor is it an original idea of mine. Rather, it was an idea developed years ago by 'who knows who' and several builders have used it and many have improved on it. It does work well, requires little maintenance, is reasonably priced and, when properly sized and constructed, will take all the rigors of river use. This system also makes the vessel easy to operate (this is a nice way of saying that it makes a 'cub pilot' look good).
This system is comprised of two components. One is a transmission with torque converter which provides forward, neutral and reverse. The torque converter provides a cushion against the initial jolt of connecting the engine to the paddlewheel. The transmission can supply some gear reduction but it should be less than 3:1. The second component is the actual gear reduction portion. This usually requires three stages. The first stage is accomplished by vee belts, the second by chain and the third is the final drive chain which runs to the paddlewheel.
The vee belts are used for two reasons. One is to absorb some of the pulse of the paddlewheel so that this pulse doesn't eventually damage the transmission. Secondly, the belts will prevent serious damage if the paddlewheel suddenly gets jammed or locked up by debris such as logs, sandbars or jet-skis. The belts will also permit a rapid directional change of the wheel such as is sometimes required when you are about to hit a dock, a lock-wall or another boat. The belts will slip, smoke, squeal and scare you to death but, they will protect the drive train and, very often, save your ....er..reputation. Even when frequently used, these belts will last a good long time (mine are the originals- they are over 18 years old and they have been tested).
The second stage of gear reduction is accomplished by, what I call, the intermediate chain. This chain is usually required to obtain the needed gear reduction for paddlewheels 8 feet or larger in diameter. Also, this intermediate chain usually runs fast enough to require a bath lubrication. This means that it should run in an oil bath.
The final reduction takes place from the last jack-shaft of the intermediate chain to the paddlewheel shaft. This chain speed is usually slow enough to require only occasional hand oiling and greasing. All of these components can be mounted in and on a box and this can be installed in the vessel as a single item. A drive-shaft, then, connects the transmission to the gear reduction unit.
Now, when the proper transmission, belts, chain and jack-shafts are selected, the resulting drive is rugged, dependable, requires little service and allows for easy operation of the vessel. It has to or I wouldn't be operating a sternwheel boat.
Your next question probably is, how do I know what components to use? Well, of course, I can't answer that question until I know something about the paddlewheel that you intend to use. However, if you supply me with that information, I feel that I can help you size and select the proper components at least for the paddlewheels most often used on live-aboard size boats.
Remember, if building a sternwheel boat was easy, there would be a lot more of them than there are.
One last comment before closing. I'm a firm believer in putting all of a vessels equipment in one location. In most cases, on sternwheel boats, the best place is the aft end of the main deck. I suggest an area large enough to house not only the engine and drive-train but, also, the generator, misc. pumps, compressors, electrical panels plus spare parts and perhaps even a work bench. After all, on long trips you may need to make some repairs or, at least, do some service work and AAA won't go to the river.