I have a machine shop and engineering project for the Dauntless boat project.

I have done a fair amount of research on the motor mount of scale model boats that use electric motors. One thing that totally astonishes me is the casual use of cheap universal or “ball” joint between the motor and the drive shaft. What is typically displayed in the Dumas (boat kit manufacture) and other brands is a fairly noticeable angle between the motor and the drive shaft. Many times a crude plastic “dog-bone” connector is in use between the yokes.

Of course I have seen a lot of very good installs. The racers usually have found out the secret to best running is with straight shaft alignment. The modeler shouldn’t always follow prototype with a waterline level engine mount fastened to an angled drive shaft. Even if there are quality parts available to do it.

This is not a problem for an automobile and other low RPM drive-shafts that have no slop roller bearings built into the cross and yoke design. In my experience and opinion, slop is one heck of a problem for very high speed drives like are used in fast running model boats. I am talking 5000 to 10,000+ RPM. Would anyone build and run a dragster with the bearings removed from the U-Joint? Model boat builders seem to do it all the time. This is where a lot of the vibration noise is coming from.

I have installed hundreds of powerful motor and pump systems in commercial central plant HVAC system with a precision drive coupling between the pump and the motor. There are especially trained technicians with very expensive test equipment who do the alignment job correctly. For highest efficiency and lowest wear and noise (power loss) the two shafts and the coupling must be perfectly aligned. I believe no less care should be taken with the high RPM model boat drive line.

Yes, the quality model u-joints are made for a small angle but it is probably not wise to run anything more than a few 1000 RPM for short periods with that set-up.

So my design goal is to build a motor mount system with coupling and engine room drive shaft alignment built in. This includes the HQ stuffing tube mount through the hull. The prop end mount will have to be carefully designed if the boat design requires an exceptionally long drive shaft. I may even use ball bearings on the shaft and stuffing tube if I can figure a way to do it. However, I have read that BB’s are somewhat overkill as flanged Oilite bearings work great and are easy to replace.

A lot of time getting this part of the build right will pay big dividends when running out on the pond. I have read a lot of stories where the motor was installed (for the first time) the night before the big outing with a couple of straps to hull blocks and the u-joint expected to take care of all the alignment.

That’s not for me.