I got it wet.

The water finally got soft enough to try the DSD. I’m extremely pleased that everything worked and wasn’t really surprised that it was slower than I wanted. Average speed, in still water, is around 13 mph. I was hoping for 6 or 7 mph faster. I had limited the diesel to 3000 rpm so the next time I try it  I’ll set the no-load rpm at 3500 and see if it will turn that fast under load. The prop was not surfacing and when I forced it to surface there didn’t seem to be a change in speed. I’m using the 35 hp SD 3 blade prop and it might be too much. Eventually, I hope to try the smaller prop used on the original 23 SD. Noise level and vibration were both very low. I haven’t figured out how to include the short video, but will….. eventually. My worries about the additional weight on the transom appear to be groundless.

Cut and paste this forum address for the video.   http://www.mudmotortalk.com/forums/viewtopic.php?t=5431

 

Ready for water

The DSD is ready to put on the boat and see how it runs. It’s heavier than I wanted, but I’ll have to live with it. If it is too heavy I’ll just rebuild it with a big Briggs or big Kohler. The most important thing I want to check is the CVT and I can do that with it setting on the trailer. I just need to get the prop in the water to see how it reacts under load. It has a little over one hour run time on it with the shop door open. I’ve taken the engine up to 3100 rpm with a prop rpm of 3565 and have detected no strange noises or vibrations. It really runs much quieter and smoother than I expected.                                                                       

Fuel system

I added an electric fuel pump to assist in priming the system after it has been idle for awhile. As soon as the engine starts the mechanical pump will provide sufficient fuel and the electric pump is turned off. There is also a fuel filter/water separator mounted between the electric pump and the mechanical pump.                                                                                                     

The control panel

The engine controls, with the exception of the throttle, are in a steel box mounted forward of and below the radiator. The toggle switch in the lower left is for the electric fuel pump that is only used for priming the system. The toggle has an indicator light directly above it that comes on when the pump is in operation. Above the light is a tach/hourmeter made by Tiny Tach and is designed for small diesel engines. Across the top are three idiot lights for oil pressure, water temperature and amps. Above and to the left of the start switch is a light for the glow plugs. The Hobbs meter is redundant except it is the original one that came with the engine and I elected to keep it to show total time on the engine.                              

The clutch

I tried to make a video of the clutch operation, but the file got too large. The only solution I could come up with is pictures of the clutch spinning at different rpm’s. The first picture is 0 rpm, the second is 1850 rpm, the third is 2400 rpm and the fourth is 2800 rpm. If you look closely you can see the upper clutch squeezing the belt and the lower clutch getting wider as the rpm’s increase. Since there is no load on the prop, full engagement of the clutch occurs at a lower rpm than if the prop were in the water.    

Back together

My DSD is essentially ready for a test run. I have two access panels to fabricate for the sides, but that is 2 or 3 hours work at most. I guess what I need, most, is some open water. I have set the idle at 900 rpm and at that speed you can count the prop blades as they go around. At idle, the prop spins at 250 to 275 rpm. I can grab the prop and stop it, but don’t want it to not turn since that would, potentially,  heat up the belt at one spot. The primary clutch starts to engage the sides of the belt at 1200 rpm. I have max set at 3000 rpm right now, but that is easy to adjust upwards once I find some soft water. With no load on the prop, full clutch engagement is at about 2500 engine rpm. At 3000 engine rpm the prop turns between 3450 and 3500 rpm. If the engine has enough torque to spin to 3500 rpm, with the prop in the water, the prop, theoretically, will be turning 4025 rpm. The engine manual says it is burning .9 gallons per hour at that rpm. The balance is excellent. The height of the engine takes the balance (over center point) to the front or rear with easy pressure on the tiller handle. The clutches and belt can be removed and replaced by one person, in the field, with hand tools. I am always open to questions or suggestions as long as they don’t involve cutting apart the box again.                                       

Major drive components

Below is a picture of the major components that make up the drive for the “Diesel Surface Drive” or DSD. From left to right they are the CVT box, the primary clutch, the belt, the secondary clutch and the lower unit.  

No really. The frame is really done this time.

Here is a picture of the box spread 1 1/2 inches. When I finished,  the top of the secondary clutch was tipped to the rear 1 or 2 degrees. I corrected that by putting 2 shims under the rear bolts of the thrust bearing. If I changed it now it would be wrong. Universal Welding cut me plates for the top and bottom, plus the lower 8 inches of the sides. The upper portion of the sides will be removable aluminum panels to allow access to the belt and clutches, I’ll start welding the top and sides tomorrow.                                         

Ooooops!!!

I got everything together and discovered the secondary clutch is backwards. When I put it on correctly the box is too narrow to align the clutches. OK, so I cut the 2 halves apart and spread them 1 1/2 inches.  The frame is welded back together and everything lines up and works properly. It looks like it is time to start installing the top, bottom and side panels.

The frame is done

I completed the frame for the box today. The front and back plates are within 1/32 of an inch of being parallel in every axis. The alignment was done using turnbuckles in the corners as spreaders. They allowed very precise adjustment and worked great!!! Once I  had everything lined up I welded in the angle iron frame pieces that form the sides, top, and bottom of the frame. I couldn’t resist starting it up and it worked as expected. The CVT responded properly, but I have a minor clearance problem on the secondary clutch at full throttle. It shouldn’t be difficult to correct. After I fix the clearance problem I’ll start fabricating the top, bottom and side panels. When they are complete, all it will require is the final welding.