No disrespect, but a Pelton Wheel is used for very high head applications. Sawmills with mill dams were what are classed as 'low head' applications. A Pelton wheel is primarily an impulse type of turbine. Low head turbines are reaction type, a whole different animal. Older sawmills used a variety of reaction type turbines, usually mounted with the shaft vertical. These turbines were similar to, or were, what is known as "Francis turbines". Various manufacturers designed and built low head/small output reaction type turbines for use in mills. The 'runner' or 'water wheel' was fairly similar in design from one manufacturer to the next, with the major differences being in the design of the wicket gates (which controlled the flow of water admitted to turn the runner) and in the setting. A lot of mill turbines were ordered for 'open flume' installation. No casing surrounded the turbine. There was a "stay ring" which contained the control gates (some makers used 'drum gates' to keep it really simple, some used wicket gates, some used a single 'butterfly' type of gate). This stay ring could be set at the bottom of a flume and bolted to the bottom of the flume. The water entered the turbine horizontally and was directed into the 'buckets' of the runner tangentially. The water passed through the buckets, and was discharged out the bottom of the runner. A 'Draft tube' was often used to provide a syphon or suction action and discharged into the tailrace.
Marlene: Welcome to our 'board. I've spent a good chunk of my career around hydro turbines, and do volunteer work as a mechanical engineer for a working museum in NY State called Hanford Mills. In the past, as a consulting engineer, I have designed hydro turbine installations for restored or re-created sawmills. One such mill is located in Wisconsin and was funded by Kohler (maker of plumbing fixtures and generating sets). Kohler wanted a re-creation of an 1840's sawmill with a 'sash saw' and sent a semi load of 'artifacts' from old sawmills to a local mill restorer/millwright. He, in turn, called me in to handle the engineering. The power for this sawmill was provided by a new Francis type open flume turbine. This was designed and built by The James Leffel Company of Springfield, Ohio. Leffel is still in business, and is now run by a man named Anders Dynge.
Another job where I did the engineering was for a mill using a 'chest' with an open flume hydro turbine mounted inside the chest, draft tube below the chest. The chest is made of heavy oak planking and held together with tie rods. A bolted and gasketed manway is provided to enter the chest (when it is unwatered) to maintain or inspect the turbine. The turbine shaft as well as the wicket gate operating shaft pass out of the shaft thru stuffing boxes to seal them.
A group whom you might contact is known by the acronyn of "SPOOM", which is short for "Society to Preserve Old Mills". Spoom has a quite a membership and their organization might be able to put you onto a suitable used/salvageable turbine. Hydro turbines are a different animal than gasoline, diesel or steam engines. Asking for a 40 HP turbine is kind of like asking for a 4 cylinder car. What type car, what body style, type of drive (2 wd or 4 wd), etc. A hydro turbine of 40 HP would need to have additional data such as:
-available head (height of water behind the dam and down to tailwater elevation, taking maximum and minimum levels behind the dam into account). Turbine runners are designed to operate using water with a specific range of heads (minimum and maximum 'pond' elevations if installed on a mill pond with a dam). The runners are also designed to turn at a fairly narrow speed range. It is up to the owners of the mill to provide suitable gearing to use the turbine's best output speed to drive the mill machinery. Other specifications are whether the turbine is to be furnished with a 'scroll case' ( a casing sort of like a centrifugal pump casing, resembling a the spiral of a snail's shell), or whether the turbine is to be mounted in an open flume installation. Draft tube details also are required- will a simple cone type draft tube be used in conjuntion with a formed concrete 'syphon bend', or will a draft tube with a syphon bend made of steel plate be required ?
Between Anders Dynge at Leffel, and SPOOM, you should get a good start in your search. Also contact Hanford Mills, they have a website. We have a few small 'relics' of vertical hydro turbines on display in the mill.
Be forewarned: if you do come across a used hydro turbine, it is more often than not a mess of heavily rusted parts. Often, putting an old small hydro turbine back into use requires reverse engineering a lot of the parts and having them made. The runner, and parts of the stay ring and control gates are usually together, but are more often than not a solid chunk of rusted machinery. I've worked on a few turbine restorations, and we sent a lot of work to the local machine shops. Stuff like wicket gate linkage pins, new turbine guide bearings (which are often water lubricated and may have had Lignum Vitae- a tropical hardwood- shoes), boring and bushing the stay ring for the wicket gate stem journals, and on it goes. Back in the days when mills used small hydro turbines for power, there was no stainless steel, no plastics, and very little use of bronze. The result is that parts on old hydro turbines are often rusted solidly together. Cast iron was the principal material, along with wrought iron or steel for the mechanical linkages and smaller working parts. Then, there is the situation where the turbine was removed and cast aside years earlier, and the result is some of the cast iron parts are broken or missing altogether. As long as there is a runner and stay ring and some remnants of the control gates, an old hydro turbine can usually be restored and put into operating order. The trick is determining the operating head the runner was designed for.
I'm happy to help you, as your project develops. Again, asking for a '40 HP hydro turbine' is like asking for a 4 cylinder car. Aside from specifying that you want a car and a 4 cylinder engine in it, think of all the other variables you need to consider if you were specifying that car. Hydro turbines are, as I noted, designed for fairly specific operating conditions. It is not like getting a 40 HP gasoline or diesel engine where you put fuel in the tank and know that the engine will start and run. Even then, you would need to know the output speed or governed speed of the engine at which it develops best torque, and the required rpm for the machinery you want the engine to drive. In between, you might wind up having to design some belting or a gear box to drop the engine rpm to the required rpm for your application. Hydro turbines are a bit more specific, since they rely on the 'head' of water to provide the energy. It comes down to head and available flow of water at your site. Get that data (or some reasonable engineering estimate of it) and you can determine if any used hydro turbines that you come across will work for your site.
Good Luck with your project-
Joe Michaels, P.E.
