Belt Drive

I found this posting by me from 2008


Chain Drive...discontinued
http://www.yachtforums.com/forums/15453-post14.html

Pulling Prop Belt Drive
http://www.yachtforums.com/forums/7567-post9.html
About three years ago I had mentioned my interest in such a configuration to the Volvo rep at the Ft Lauderdale show. He said I should come visit them in Norfork. I never did take the time to follow up on that invitation. I suspect they have been working on this for some considerable time.

I had previously suggested this idea for both single and/or dual props, but utilizing a kevlar belt drive component rather than 90 degree shafts:
From my website,"Other than direct straight-shaft drive of propellers, most marine drives today involve some sort of 90 degree arrangement, ie.sail drives, stern outdrives, outboards, etc. The 90 degree gear set (and there are usually two sets) is the potential weak link in the system. All the power is being transferred over a very physical small contact area between two bevel gears. This contact patch can be nothing more than a thin line on the opposing two teeth! Special hardened gears and maintaining close-fit tolerances permit the horsepowers of today. But when it comes to diesel engines, the situation gets worst. The diesel is by its nature a much more torque'y beast. Gears to handle an even modest horsepower diesel are extra hard pressed. Teeth can break or get worn so quickly as to loose all tolerance."

Volvo is talking some fairly big diesel power here. I can only think that the smaller dia props (dual configuration) are a factor in making it work, but I still have trouble believing it. I wish them the best of luck in a successful product.


New Drive System, IPS from Volvo Penta
http://www.yachtforums.com/forums/te...html#post15453

Chain Drive Duo Prop
http://www.runningtideyachts.com/dyn...ChainDrive.php

How interested are you???

 

Both Volvo links dont work

404

 

Chain vs Kevlar or Carbon Fiber Belt

At one time I was doing quite a bit of study of this subject in anticipation of producing some units...maybe over in Asia. But the boat market is less than well at the moment, so I'm not persuing that subject at the moment.

I started out favoring the idea of toothed belts over chain. But over a period of time I came to the realization that the silent chain approach made much more sense, and would be easier to impliment. This is particularly true when you start talking of HP greater than 20-30.

If you start looking thru the tables of pulley diameters (minimum dia) recommended by the belt manufacturers for specified powers transmitted you will find the diameters of the pulleys getting quite big which might require thicker struts, and all of this interferring with the prop...etc...etc

 

Frosty, I've got belt drives on nearly all my shop tools, the off set load on the pulley is negligible and almost all of the systems have some form of gravity tensioning so the weight of the motor maintains tension on the belt. In a boat I suppose that wouldn't work but it wouldn't be hard to have a spring do something similar. I'd think that over all in a small HP application a belt drive would end up lighter and a lot simpler, specially if the system only has F N R. The torque on a motorcycle sprocket is about what I would expect on a boat of the same weight and HP range.

PS
how did the burn turn out

 

If its a hypothetical question Ok but you are re inventing the wheel.

A spring??? tensioning an engine drive. Your power tools will not be over 2 HP--if that.

Whats wrong with a gearbox and shaft , how simple can it get.

Burns good. Ta

 

Belt drives are not exactly new to the marine industry. Here in Sweden we have a number of commuter ferries with multiple diesel engines driving a single propeller shaft via belts. Aside from the obvious bonus of arrangement, the belts soften the shocks from propblades hitting the unavoidable chunk of ice et c.

Those drives use multiple vee belts, there is no use for a toothed belt in this kind of transmission. One reason is that the combination of weight and spring constant of the "free" parts of the belt have to give a "flapping frequency" that is outside the frequency of the structure, otherwise there will be very high levels of stress and noise.

So, use traditional vee-belts, dimensioned in accordance with engineering praxis, keep the shaft distances short and don´t forget to design proper radial bearings that take the radial loads. Adjustment can be done via the normal engine mounts (remember the radial loads add to the engine weight when calculating the resonance frequency of the elastic mounts).

 

I may have posted some info on this before as it related more to a 'splitter' transmission question, but...

We built a single-in/dual-out splitter transmission using Dayco Panther cog belt drive components. Noise was non-existent as long as tension and alignment were correct (far quieter than any 'open' chain drive I've ever seen and without the myriad other headaches of a chain drive...like lubrication) and much quieter than the traditional 'square' tooth belts too. We were reliably transmitting 450HP to a pair of waterjets and a PTO hydraulic pump and a PTO water cooling pump.

 

I wasn't speaking of an 'open' chain drive but rather a contained one that maintains the perfect parallel shaft arrangement that is required for long term application. These 'silent chains' have been Incorporated in many industrial drive applications.

An older Oldsmobile vehicle application to connect the transverse motor and transmission arrangement proved highly durable for over 100K miles with just ordinary transmission fluid lubrication.

There are also a number of subtle differences in the chain to drive gear details in these 'silent chains'

There are a few other links over on this other posting:
http://www.boatdesign.net/forums/inboards/prop-shaft-systems-24636-4.html#post286085

All that said, I'd be interested in looking at more details of your belt system BMcf

 

'Silent Chain', FAQ

http://www.ramseychain.com/faq.asp

 

I knew exactly what you meant..hence my clarifier of 'open'. Back when we needed that custom one-off and very ligthweight 'splitter +PTOs' box, the cost of doing it with other than belts was too cost prohibitive. And then we discovered the Panther 'round-tooth' quiet belts in the design phase, used those, and all worked out.\

We did have cooling issues with the box when running at full power for long periods. Ended putting a pair of axial fans on vent hoses to blow a lot of air through...cured the problem.

I'm on the road..Rio..so when I get back to the office, I'll try remember to post up the 3D model of our 450 HP dual-ouput 'gearbox'.

 

If you read what anthony goodson was talking about he says that the belt system would have to be in a "cage". Basically an apparatus thats soul purpose so to make the belts line up with each other perfectly. There would then have to be flex coupling and sliding spline connections before and after this "cage" so that any movements of the prop and/or motor are not felt by the belt. In this application, the "cage" would be tensioning the belt not the motor mounts. I'm not sure if I like this application. Seems too complicated, but it would work.

As for what is wrong with the gearbox and shaft... nothing. But if nobody was trying to make something new and improved ... we'd still be rowing around.

 

Brian,
I think you found the flaw in your belt system driving a lower unit style drive. The pulley diameter is always going to be too large and necessitate to large of a housing. Maybe the chains would be a better solution for this. Although I think the 90 degree bevel gears are a very tough opponent. I've seen lower units with 5000 hrs plus on them. I see my application as more of a high speed application with shaft to propeller type systems, and shallow shaft angles... maybe even 0 degrees and surface piercing. Only purpose of the belt being to put shafts outboard where the engine can't be installed.

That is a picture of the new 7 Marine 557hp Outboard. This picture shows their "Propriety transfer case" which many are assuming to be a belt or chain. That is one heck of a belt haha.

BMcF,
I would be very interested to look at that model as well. I think it would basically be the same as the system I would like to design except remove one arm from the splitter... and make two of them one for each motor... And only need to transmit 100hp.

 

Jeepy you misunderstood my post ,the sliding spline and flex couplings are only on the input side of the cage ,the propshaft becomes the axle for the lower belt drum and terminates in a thrust bearing. Probably a deep groove angular contact bearing which will deal with axial and radial loads. I too am looking forward to BMcF's drawing.

 

Okay i guess you are right. Another flex coupling and sliding spline would be unnecessary. Thrust bearing would be something like the aquadrive system correct? http://www.aquadrive.net

 

Huge , inefficient push rod American dinosaur engine. when will America develop finesse in their engineering.

http://www.boats.com/blog/2011/02/seven-marine-reveals-557-hp-outboard-at-miami-boat-show/