Jensen Model #95G Turbine Power Plant Engine Prototype

USA - Manufacture date: 2005
Bore = N/A, Stroke = N/A ", Flywheel diameter =2.5"
Style: Prototype , Impulse Rotor

Dimensions: 14" length x 12" width x 10" height
(includes base)

Prototype Jensen 95G Turbines


E
very once in a while you get to be a part of something you can take pride in. This is very much the case with the Jensen model 95G Turbine Power Plant project. Recently documented information from a very rare tape recording confirmed that a Jensen steam turbine has been discussed off and on since 1932. I'm pleased to say that I was lucky enough to be a part of the project that finally brought this long awaited Jensen model to reality. The project took 2 years of discussions, planning, design, redesign, testing, more testing and finally, after far too long, approval and introduction to the Jensen product line. Throw in a few disappointments, several roadblocks and some serious sweat and you'll get a sense of the roller coaster ride this now mighty little power plant took us through.

The idea of a Jensen turbine is certainly not a new one. The idea has been reborn a number of times over the past 70 plus years, but it was always rejected as not being visual enough to demonstrate the system effectively. Let's face it... a spinning shaft sticking out of a enclosed rotor casing is about as entertaining as watching paint dry.

That was all before Karsten, a young German turbine maker, came to my attention a few years back. Several of Karsten's earliest designs can be seen on this site, along with a bit of the our history. After re-establishing a once lost relationship, I mentioned that I'd like to explore the idea of a Jensen turbine. As we traded ideas via email, we began to come up with what seemed to be a viable solution to the boredom factor and I began modeling the project in 3D to see if what we envisioned would actually work

Early 3D Design Rendering

View of the 95G Gear Train

After a couple of false starts and trip or two back to the drawing board, Karsten took the basic design and worked his own special magic to tweak the idea closer to a working design. He shipped me a couple working prototypes for testing but it soon became obvious that there were serious issues that were very much in need of solutions.

A steam turbine requires several things to work properly. The steam supply needs to be constant, at a usable pressure and it has to be of high velocity. Then there is the basic nature of a turbine which had be dealt with. A turbine rotor turns at very high rotational speeds, but it delivers very little useable output torque. In order to harness the energy a turbine produces, the low torque rotational force has to be reduced through a transmission system to increase the torque to a more usable level.

Testing continued and we began to find solutions to each problem, one by one. Some internal redesign ensued, along with adjustments to the transmission reduction system. A second round of prototype turbines arrived from Germany and the first of three was mated to a Jensen electrically heated boiler, as testing began anew.

It was immediately obvious that we were getting closer to the right track. We had plenty of back pressure in the system to maintain a steady steam supply. We had the steam velocity up to a  level that was producing amazing RPM's and the output though the gear train was in the proper range to theoretically power a Jensen DC generator. Still,  the combination just didn't quite seem to have the "WOW Factor" we were seeking.

 

Early view of the 95G Turbine
driving a Jensen 15E DC Generator

I decided it was time for some outsider input, so I contacted a small but very loyal group of Jensen aficionados and shared photos with them, asking them to maintain confidentiality until the project either came to an end, or it was accepted by Jensen. This proved to be a very good idea , but it also added another level of pressure to get the project right.

Karsten had  tweaked the design about as close to the optimum as his machine tools would take us. The rest fell to me to find a balance between performance, appearance and that elusive WOW factor. I tried a number of variants, making progress in small fits and starts, toward what I thought was a final version. However, the collectors' feedback soon told me I was not quite as close as I had hoped. They heartily agreed with the visual design of the turbine motor, but the small Jensen 15E DC generator was certainly not winning any hearts or minds. They indicated that while they were totally pumped over the turbine concept, "the gotta have it"  ingredient was missing. They unanimously agreed that they would prefer to see the more visually interesting Jensen model 15 AC generator used in the final version. So....  it was back to the drawing board again, with a whole new group of roadblocks to negotiate.

The problem was that the turbine worked fine with the lighter load of the DC generator, but the AC version had a much stronger magnetic field which gained in resistance as it turned faster. The turbine could turn the AC generator but it was too slow to light the lamp post above a dim glowing flicker. I must have made up 30 or 40 different combinations of pulley ratios, on my recently acquired lathe, but things were not improving to any great extent. It was frustrating to be so close, yet so far away from what was a potentially successful configuration. The collectors were enthusiastic about the addition of the Model 15 AC Generator and were getting excited by the "look" of the display. The "gotta have it" thing was steadily creeping into the design, as the crew provided feedback on each new batch of photos.

Flywheel and Model 15 AC Generator

Have you ever had a "EUREKA!!" moment? As sometimes happens, this one came while I was sleeping and it was enough to wake me up. It dawned on me that Karsten had left an exposed stub on the end of the final stage output shaft for a small, very narrow pulley. By extending this stub, I could fit a Jensen flywheel which would have a nice 3 inch diameter and a PTO groove already in place. At about 3:30 in the morning, I cranked up the lathe, chucked some brass and cut a new shaft extension. I pressed fitted it onto the exposed stub and added the flywheel. After installing a drive spring belt and waiting for the boiler to heat up, I held my breath and opened the throttle valve. The motor tried to run but wouldn't start on its own and it slowed down very quickly. I scratched my head a bit and gave the little turbine the evil eye.

While I was giving the machine the hairy eyeball, it was steadily building a full head of steam. This was announced by a plume suddenly rising from the relief valve. I reached for the throttle, gave it a twist and was rewarded by the sweetest sound I could have asked for at that moment. The little turbine began to spool up with a unique whine and continued to increase in speed until the lamp post was shining brightly. To my delight, it maintained enough speed to keep the bulb brightly lit through an entire boiler full of water. A few more test runs to make sure this was no fluke and I was off to bed again just as the sun began to come up.

The project was submitted to Jensen as somewhat of a "Fait Accompli". They knew I was working on some sort of prototype, but I suspect they were not giving it much hope or encouragement. After all, the project had been discussed any number of times for over 70 years with no results. It took a few weeks to convince Mr. Jensen to test the thing, but when he finally got around to it, he was an immediate convert. The Jensen model 95G was introduced in October of 2005 and is now a very successful product...  and the first totally new Jensen design since the 1960's. The first 25 of the 95G's were numbered, dated and signed by Tom Jensen Jr. as special collector pieces. These 25 pieces also have a minor but  intentional difference from later models which allows Jensen spot any attempt to fake a "first production" model.

Serial # 0000 Final Pre-Production Engine
with a Couple of  Friends

The  addition of the Jensen flywheel combined with the 1940's styling of the curved turbine shell, and the model 15 AC generator all worked together to create a whimsical retro look that the collectors loved. The addition of the Jensen flywheel also "branded" the model 95G as a true breed Jensen. The open visual design of the rotor, transmission and generator has been a hit with teachers and power plant public relations departments love that it makes it so easy to demonstrate how their plant works, even to non-mechanically inclined visitors. It took a few years to come to be, but Jensen now has a an all metal turbine to be proud of..  I'd like to think that Tom Sr. would have approved.

Many thanks go to Karsten, for the skillful application of his unique talents, as well as to the marvelous group of  Jensen fans, and you know who you are, for their invaluable feedback and loyalty to the effort and the Jensen company. Without the parts played by each and every one of you, this project could never have come to such resoundingly successful results.

 
 

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