twin with single screw

Twin engines to single prop was done on Romsdal trawlers.
The engines had a standard PTO clutch with belt drives to the shaft.
Engines rotated the same way. Run either engine or both.
The prop was controlable pitch.

Ted

ps, she has been sold, so a lot of the pitures seem to be deleted

Powerboats: 65' Romsdal North Sea Trawler - Listing #: 3818

youtube video if it works

A good friend put a NA VW diesel in an old wooden fishboat converted to pleasure. About 1500 cc IIRC putting out 52 hp max. It worked great! And originally came out of a Rabbit. Cruised at about 6 kn and had lots of rpm left. Conventional marine gear hooked to shaft though so I can give no insight to belt drive. Dry stack exhaust and keel cooler so nothing to do to "marinize" it.

Why do you think you need two engines?

Might be an ideal time to consider a diesel electric set up? A dc generator on each vw and a dc traction motor on the shaft. Infinite power control from 1 rpm to max rpm that suits the prop. Fairly simple install. Then let your imagination go wild with battery set ups, house power use etc, etc.

Nomad Willy said:

If the newbie just wants a cheap power system I'll agree w PeterB but if the newbie can hardly wait to see if this works or that and sees his effort as an experiment w much to learn and is prepared for whatever could happen .... it would be a shame to discourage him.

".

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I didn't discourage or encourage. I simply asked the question, "Why?" One word. I'm assuming to this point that the only reason is he has the two engines, although he didn't directly answer that question. I felt by understanding why he was doing it, people might provide better input.

Dorado, a Florida boatbuilder made forays into this realm, usually in the opposite configuration, two drives from one engine.
The hardware could be reversed for twin engine/single drive.
They experimented with belts and chain drives, and I think they wound up with a gear drive called "Geared Up Systems".
I believe their efforts were focused on splitting the drives for shallow draft on deep vee hulls.

Mainship and Dusky each made at least one boat with the Geared Up (1 engine - 2 props) configuration, made with off the shelf industrial parts. I would be willing to bet it would also work in reverse as a mechanical gearbox shouldn't care which way the power goes.

Re airbags for engines and generators, engine isolation is a simple engineering problem that can be addressed by appropriate and reliable mounting solutions. Their are pneumatic isolation mounts made by several manufacturers, as well as units that use springs, rubber or polymers. These are marine industry suppliers that make appropriate engineered solutions.

Airbags, as pointed out may be fine in a static installation, but in a dynamic installation like on a boat any captive devices are liable to "short circuit" any isolation. Any reputable manufacturer will supply units that provide "positive capture" which means even if the primary isolation medium rubber/spring/oil/etc fails, the engine or generator stay put and don't bounce around an engine room.

Experimentation and stretching the envelope is all good fun, done my share of wacky stuff and will probably do some more, just be careful



Geared Up Systems?

kapnd said:

Dorado, a Florida boatbuilder made forays into this realm, usually in the opposite configuration, two drives from one engine.
The hardware could be reversed for twin engine/single drive.
They experimented with belts and chain drives, and I think they wound up with a gear drive called "Geared Up Systems".
I believe their efforts were focused on splitting the drives for shallow draft on deep vee hulls.

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Crankshafts are strong .

Why not just line the VW up on center line and crank the last engine if needed?

Otherwise the USN has gear boxes for 2 engines , with a common shaft.

Heavy tho , but easily had used.

BandB said:

I didn't discourage or encourage. I simply asked the question, "Why?" One word. I'm assuming to this point that the only reason is he has the two engines, although he didn't directly answer that question. I felt by understanding why he was doing it, people might provide better input.

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You must have a guilty conscience BandB. My post was addressed to PeterB on post
Number 22.

But the why he's bark'in down the DIY road is important. Some aircraft homebuilders spend years working on an airplane. Fly it once or twice and then sell it. And start a new build. Some build strictly according to plans and some only use the plans as a guide. And some say "what plans" and build only w what's in their heads. More boat builders do that for obvious reasons. I did on a 28' OB cruiser.

But if he's just trying to save money and knows little about building or engineering PeterB's post is spot on. It could very well be worse than a big old wood boat project.

Nomad Willy said:

You must have a guilty conscience BandB. My post was addressed to PeterB on post
Number 22.

.

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No, not at all. In his post, which you responded to, he said he was agreeing with me. So, I was involved in your response regardless of who you intended it for and I just wanted to make it clear I hadn't expressed any opinion.

I still haven't. Only have asked why. If he has reasons that make sense to him, then all is well.

Older tugs had twins on a single shaft. It was most common with diesel electric. I ran tugs with it. 2 engines running 2 generators, each with its own electric motor on the reduction gear. Running w/o a tow, you could run on one engine. Both electric motors were mounted to a reduction gear. All DC voltage. Many navy YTMs had this setup. Later people took out everything but the reduction gear and put 2 modern diesels with transmissions connecting where the electric motors were.
Smaller tugs had the DD quad or dual setup. Quad setup was only about 800 hp. The navy also used tandem engines in some torpedo recovery boats. Usually 2 DD 671 on each shaft in line with a hydraulic clutch in between. Probably boats built before the v12.
I think the best way to do the two VW engines would be a hydraulic system, or not at all.

Given the VW are low HP, using components from somewhere like here Home - Hybrid Electric Marine Propulsion might work well.

Or perhaps two engines turning hydraulic pumps connected to hydraulic drive it would stop the synchronization problems and make it easy to run just one motor.

motion30 said:

Or perhaps two engines turning hydraulic pumps connected to hydraulic drive it would stop the synchronization problems and make it easy to run just one motor.

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Motion,
If the OP is into hippie financing the cost of at least three major hydraulic components would not be cheap. Vetus has a good selection though.
Also running on one engine would almost necessate a reduction drive ratio very unsuited to running one engine. It would be like taking a regular boat w a 2-1 gear and running it direct drive. Very low thrust and significant overloading. Fine for a "get home" but basically just for an emergency.

Beebe showed just such a setup in his original book. His plan was to use one engine when passagemaking loading it for max efficiency at cruise speed and two engines for local cruising. Care must be taken not to overload when running on one engine.
A great plan but the devil is in the details as usual.

McGillicuddy said:

Might be an ideal time to consider a diesel electric set up? A dc generator on each vw and a dc traction motor on the shaft. Infinite power control from 1 rpm to max rpm that suits the prop. Fairly simple install. Then let your imagination go wild with battery set ups, house power use etc, etc.

Click to expand...

BandB said:

I didn't discourage or encourage. I simply asked the question, "Why?" One word. I'm assuming to this point that the only reason is he has the two engines, although he didn't directly answer that question. I felt by understanding why he was doing it, people might provide better input.

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Exactly right. He has the engines he has now advised, so messing about with a diesel electric set-up in a way makes more sense, rather than just trying to mechanically drive one shaft with two engines in a boat where space for that might be tight in that configuration. Not so much an issue if just driving generators, however.

Reading this thread I am back to the question already posted by some: What's the point? what's the goal? Looks complicated to me for no obvious reason.

L.

Lou_tribal said:

Reading this thread I am back to the question already posted by some: What's the point? what's the goal? Looks complicated to me for no obvious reason.

L.

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Still waiting on that myself

Had a few more hours to think this one over and no matter how much I try to think positive of 2 horrid 65hp Vw engines running a single prop with pulleys and v belts the idea is #@&^*there is no way it has any benefits other than been totally left field .
A single 120HP Perkins or similar with gear box can be purchased for a song and without rewriting marine design and marine engineering manuals should be given a little more thought .

VW Tolly said:

I am proposing to re power from a single gas to twin vw diesels by way of v belts to a common shaft to input a v drive transmission. Does anyone know of this being done?
I hope that I'm posting this in the right place. This is all new to me.

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Welcome to the forum.

A fairly conservative bunch here. They take a while to warm to new ideas.

I agree that this is not the most cost & time efficient way to re-power, but it doesn't have to be. Owning a boat in general doesn't make a lot of financial sense sense but we all enjoy it anyway.

AusCan said:

Welcome to the forum.

A fairly conservative bunch here. They take a while to warm to new ideas.

I agree that this is not the most cost & time efficient way to re-power, but it doesn't have to be. Owning a boat in general doesn't make a lot of financial sense sense but we all enjoy it anyway.

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Like he said. Don't be unduly put off by our comments, we are just trying to help - mainly because what you are contemplating gives 'thinking outside the box' a whole new meaning, but we're all keen to come along for the ride, all the same...

Peter B said:

Like he said. Don't be unduly put off by our comments, we are just trying to help - mainly because what you are contemplating gives 'thinking outside the box' a whole new meaning, but we're all keen to come along for the ride, all the same...

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When I was on acid in the sixties I had plans to put a aircraft jet engine on the bow of my sailing boat to fill the sails but much brighter people put me off the idea .

gaston said:

When I was on acid in the sixties I had plans to put a aircraft jet engine on the bow of my sailing boat to fill the sails but much brighter people put me off the idea .

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Gaston, someone promoting that idea should, I suspect, be put inside the box - a padded box...

Lou_tribal said:

Reading this thread I am back to the question already posted by some: What's the point? what's the goal? Looks complicated to me for no obvious reason.

Click to expand...

knotheadcharters said:

Still waiting on that myself

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See OP's follow-up post #19.

-Chris

VW Tolly said:

I do have the engines and I have the machining, welding, mechanical experience but know nothing about synchronization. I theorize finding the best ratio for economy with one engine and use the second engine for redundancy and extra power ie. crossing the bar etc. I would mount the engines on air bags to dampen vibration and tension/clutch v belts - four 5/8" belts per engine. I don't even know if I can drive the belts of the end of the crank or need carrier bearings.

These diesel engines are very small and light and put out about 65 hp each.

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Yes thanks Ranger,
And probably the "machining, mechanical experience and welding" has been frequently overlooked in our posts. However I'm still thinking it wouldn't be of much value unless the gear ratio problem can be solved or if running on one engine will be a rare event.

But he sounds like a good man to pull this off. Missed that at first.

motion30 said:

Or perhaps two engines turning hydraulic pumps connected to hydraulic drive it would stop the synchronization problems and make it easy to run just one motor.

Click to expand...

A friend of mine is a mechanics instructor. A recurring class project is to construct a mini modified pull tractor for a competition every year. Hydraulic drive has proven to be just the ticket and a couple years ago started winning the prize with a tractor powered by 7 Honda equipment engines. They can add, swap or remove engines with ease depending upon the class they are running in.

I also like the differential idea mentioned up thread as another way to skin the cat.

CPseudonym said:

A friend of mine is a mechanics instructor. A recurring class project is to construct a mini modified pull tractor for a competition every year. Hydraulic drive has proven to be just the ticket and a couple years ago started winning the prize with a tractor powered by 7 Honda equipment engines. They can add, swap or remove engines with ease depending upon the class they are running in.

I also like the differential idea mentioned up thread as another way to skin the cat.

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Now you've opened Pandora's box.
I can't find it on the internet right now, but there was a dragracer with 4 hemis (Chrysler?) Mopar anyway:lol:

Ted

Tommy Ivo
Thats a flashback!
I saw that thing get eaten alive by a go-cart powered with a helicopter turbine engine.
The noise it made was truly and earthshakingly glorious, but it was way too heavy.

Ted said:

Now you've opened Pandora's box.
I can't find it on the internet right now, but there was a dragracer with 4 hemis (Chrysler?) Mopar anyway:lol:

Ted

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Yep I remember that one it didn't work either

The question is what is the Hobby?

Boating ????? or re inventing , rebuilding boat propulsion machinery?

Another thought just how much power loss friction will occur with V belts pulleys , bearing block , and a gear box ??? . I think those little 65hp engines will be working very hard maybe 80%+/ WOT but they will be doing nothing .