Oddball non-boat Outboard question

It was pointed out earlier that there are plenty of industrial gearboxes available, the idea of using one off an outboard motor makes little sense, especially as the ratio you say you want, is not achievable.

 

You have explained the mechanical system but the goal that you are trying to achieve is not quite clear.
Perhaps, because you refer to the 1978 Parker prototype which claims to have attained 75mpg, you are trying to install a heavy diesel, hook it to a hydraulic transmission system to gain a high miles per gallon number because you believe that running a diesel engine at a particular rpm will save a lot of fuel.
You suggest that you will install a heavy hydraulic accumulator and let the engine go to idle and perhaps feel that what energy that you have stored in the accumulator will provide further propulsion.

While it could provide a small amount, you will then need a place for this low pressure oil, after it has gone through the hydraulic motor to sit. It cannot return to the high pressure accumulator without the diesel driving the pump to put it back into this reservoir at high pressure

While the accumulator might soften out surges, power transmission as it occurs in an ATV is direct and I have never felt a hindrance from being directly "hooked up" mechanically between the engine transmission and the rear axle

If you think that by running the diesel,{ at a term that I read constantly (and cringe) in forum threads}, at its sweet spot, there is often one extremely important part that is often omitted.

If you want to run a diesel at an optimum fuel efficient rpm, you have to include the horsepower that you are taking off the engine. Ie determine a constant

Ie Say you have an engine capable of producing 100 hp. At max throttle, poor fuel efficiency at this max throttle and max 100 hp draw. But instead you want to produce say 85 hp continuously, you can find an rpm that will provide this hp. Say that it is at 3500 rpm.

You cannot set a constant speed governor to 3500 and expect the engine to provide the lowest fuel consumption if you draw, 25 hp, 45 hp, 65hp and 85 hp off at this 3500 rpm

Your atv build will probably not run at one constant speed and one constant horsepower requirement.

By adding a heavy diesel, a heavy hydraulic accumulator, a storage tank to deal with the oil returning out of the accumulator when the engine is at idle, pumps, motors, heat exchangers for the oil, I am not sure that you will achieve what I THINK that you are trying to achieve

To your comment that you did not want to provide information on the project because you do not want to defend your concept. You don't have to defend it at all.
The contributors are only pointing out perhaps deficiencies, or what they feel might be deficiencies in your reasoning.

This is part of the engineering/design process

I have been part of the brainstorming process where several engineers are divided into two groups when presented with a problem or a particular design concept. A senior engineer will call one group the proponents and the other opponents and let each group beat each up each other with technical situations/faults that could occur. For and against
This is a very healthy and non hostile environment to find design solutions.

 

I was once employed as the "balloon popper". My sole purpose on the job, was to take all the ideas and concepts and find ways to poke a hole in their balloon. This is a form of attrition that is common in engineering, some call it debugging, lots of names really, but you beat the crap out of it and if it survives, you just might be onto something. If it doesn't, well you've just saved a bucket full of developmental funding.

 

Crash and Burn

Well, after about a dozen hours of reading and research, on the subject of boat gears I concede to the majority. While I did find ways to make it possible, the goal was feasibility and cost effectiveness and in latter regard the concept failed.

As to the overall diesel project, confidence remains high. Problems mentioned have been theoretically addressed and debated to the point where only the prototype will provide definitive, and accepted, answers. i.e. earlier in this project an engineer assisted in computing the gains and losses of smaller diesel at consistent rpm vs not; of gains employing accumulators for recapture of energy lost during braking, coasting and highway speed vs weight of devices needed to perform such tasks; even pros and cons of a lighter bladder accumulator vs the heavier piston accumulator and many more.

In a nutshell, and as stated before, I do not expect to achieve the 75 mpg of Mr. Parker's vehicle. I have made some concessions e.g. aerodynamics and weight. I do believe that more than 50 mpg will be realized, and more probably than not 50 mpg will be consistently attainable. I am cautiously optimistic that greater than 50 mpg will be consistently attainable.

Why this is generally exciting is that this vehicle will allow travel in the city, on the highway and offroad. (Although a top speed over 60 mph will be difficult without a supercharger or turbo or ECM of all of the above).
While 50+ mpg is not uncommon, 50+ mpg in an real off road vehicle is.

I am thankful for all the assistance provided and will return, I wish to recover my bucket seats in marine material (water resistant) and as low rpm diesel boat engines are common, it is likely that I will use marine engine gauges in the dash (but, those have yet to be designed or purchased)

I will not be as prolific in posting in the next bit, but I leave you with a copy of the plans from Mother Earth News for the first, and only, boat I ever built. With modern electronics it should be possible to extend either the distance traveled per charge or shorten the charge recovery time. Run time was the only downfall of the boat. http://www.motherearthnews.com/diy/bumper-boat-water-scooter-zmaz81mjzraw.aspx#axzz2Rrb7nXLM

 

Diesel ? Diesel torque would be a threat to an outboard box.

 

Dr. No ?

 

Most of the time, I didn't make the decisions, but some were obviously not going to meet expectations. We all knew the score and the process, it was just part of the program.