I looked up the Land and Sea site.

They sell a torque transducer which is mounted to a U joint yoke that they have modified. It appears that this yoke will twist quite a bit more than an all steel one and in the process twists a piece of ferromagnetic material rotating as part of the drive shaft. The magnetic properties of the magnetic material changes as a function of the amount of twist, which is in proportion to the torque. The stationary half of the device reads the change in magnetism and gives out an electrical reading in foot lbs of torque. (foot lbs is the same as lb feet as this is a non vector and the dimensions are commutative. We discussed this long ago, just believe me.)

They don't say how to calibrate the device but I would say the easiest way is to lock the crankshaft in a fixed position and put a torque wrench on the prop shaft spline. Then for every reading of the torque wrench, you set the calibration data points on the electronics. Remember, that torque is torque whether the shaft is rotating or stopped. Other torque measuring machines, e.g.,dynomometers are calibrated with the shaft stopped.

I looked under other related patents and this is a well developed technology. There are others which work off of light beams.

In any case, measuring torque means measuring the amount of twist on a shaft and one of the ways to do it is to measrue the reaction forces on the load as the traditional Pony brake machine.

The other way is to measure torque is to do what this device does and measure the twist of a rotating shaft with a non contact transducer.

It is very clever, but I like the idea of the optical pickup better, as it may be cheaper and less prone to drift.

Note, the car people are looking at fast transients in the torque readings. Most boat people are looking for steady state torque, unless you are in a drag boat.

Horsepower is the multiplication product of the torque times the rpm with a constant factor.

The transducer is mounted at the factory and the yoke is locked down/placed in a vice and a set amount of torque is applied and measured and calibration is set.

So how much would you pay for this on-board real time digital readout dyno?

I have no idea how much this might cost, but $1000 for the dash unit and $500 per engine might fly, as long as the installation was relatively simple. I wouldn't want to buy an extension box as part of the required installation. But sending my props away to have the strain gauge installed wouldn't bother me. That's assuming that the prop location is possible. Pulling the drive and having the input shaft modifed wouldn't bother me either.

As an option on boats I think you would market this instrument through the builders of high dollar boats, and it might have appeal beyond the high performance boat arena. For example, it might be worth it to the owner of a fast 50+ foot sport fisherman. Any where you can brag to your buddies about a big number right? It could be a testing tool for high performance marine service centres. And it could help engine builders sell their product, as long as the "after" test met expectations. Boat tests for magazines and TV shows might be another outlet.

I wonder if it would be possible to modify the engine coupler with the sensor? Not only would you get a torque reading but you might also have a pre-indication of coupler failure(i.e. your horsepower/torque would suddenly increase due to excessive coupler movement). It would also then be easily adaptable to virtually any marine engine/drive combo.

It needs to be permanetly fixed to a shaft. The stelling box looks to be the easiest application. High end builders who use these boxes- Skater, Formula, Fountain, etc. Might be able to also go on boats with trans.

We have an on board "real world" dyno that we use during testing. With our own computer system, we measure through dual mass air flow sensors and two wide range oxygen sensors. So were measuring air by weight going in, then we measure what was burned. It's as close as most state of the art dyno cells. So it's very possible, but expensive. This doesn't drift or vary, it's very unique.

Thanks,
Dustin

Dustin, So how does that get you tq and hp numbers?

From a theoretical point of view IIRC, you just need the material properties and physical dimensions to determine the deflection at some given torque. You'd have to assume a few things like homogenous material and the dimensions remain constant under the deformation but I think you'd be close enough for a baseline.

ttt. I'm getting closer to the on board dyno. Today dropped off the pieces to get it made. Can't wait.