Drives with Belts

[ViribusUnitis]

In looking through yachtworld, a strange drive system caught my eye.

It was a set of v-belts. The pully for the engine was smaller than the pully for the prop shaft. It also seems to allow the engine to be lower in the vessel. The listing claimed a 50 hp Perkins.

Is that typical? It seems strange and undersized for me.

[motion30]

seems strange to me as well Could tell how big the belts were?

[Chief Engineer]

I have seen that on a couple of boats in Fort Lauderdale years ago.

I seem to recall there were three belts........They were european built

[NotQuiteLost]

Originally Posted by ViribusUnitis

In looking through yachtworld, a strange drive system caught my eye.

It was a set of v-belts. The pully for the engine was smaller than the pully for the prop shaft. It also seems to allow the engine to be lower in the vessel. The listing claimed a 50 hp Perkins.

Is that typical? It seems strange and undersized for me.

I've got a Perkins 6-354T for my boat, and as a backup I've often considered getting a hydraulic motor that I could drive off my Westerbeke 71C-Four 20KW BEDA generator. It would be strictly a backup for motoring into/out of marinas/channels and such, but I've often thought I could get 3-4 knots true speed out of it without working too hard.

I've also toyed with the idea of building the entire power plant of a smaller (40-45') boat around a generator like the one I've got. It's pretty efficient fuel-wise, quiet and thus far really low maintenance. Plus, it's nice to have a 20kw set onboard for starting up big watermakers and such.

[Jim Cate]

G'Day all,

Have a friend with a Roberts 45 and a v-belt drive system like you describe. It has been lots of trouble, a general PITA, and I don't think anyone in their right mind would choose such a system for a serious cruising boat. Many failure modes, hard to replace belts, especially at sea (and where else will they fail??) and no obvious advantages over a conventional system.

Cheers,

Jim

[Steve Pope]

It does allow you to eliminate the reduction box all you need is a forward / reverse clutch with the reduction done by the pulleys.
They used to be a lot more popular in the 1950's /60's and 70's as a simple drive system before gearboxes were made specifically for pleasure craft. Also used on inshore fishing vessels.
A well designed set up would give very little trouble, but many amateur installations were never designed or aligned properly from the start.
Just as hydraulic drives had their day about the same time, most died from lack of maintenance as accessability (lack of) didn't help and the whine with hydraulic systems soon had folk replacing them.

[svHyLyte]

Friends of ours in Cape Canaveral, Florida, have a huge 50+ year old converted fishing trawler powered by a GMC 671 with a belt drive. The shaft is dead horizontal above a keel with carrier bearings at every few frames, The engine sits above the drive shaft amidship. Adjustable idler wheels are used to tighten toothed drive belts (of which they keep a supply aboard). Changing a belt reportedly takes all of about 30 minutes. They've been taking her to the islands every year since the 1970's.

FWIW...

[jenny2]

Originally Posted by ViribusUnitis

In looking through yachtworld, a strange drive system caught my eye.

It was a set of v-belts. The pully for the engine was smaller than the pully for the prop shaft. It also seems to allow the engine to be lower in the vessel. The listing claimed a 50 hp Perkins.

Is that typical? It seems strange and undersized for me.

A friend of mine bought a Holiday Mansion house boat its around 42 or 44 feet and came with two 350 chevys he got tired of feeding the thirsty gas engines he took them out it has volvo stern drives he built bell housings coupled to the drive units machanied shafts and put pullys on them then put a 6 cylnder lehman in with another bell housing on it two sets of pullys on the engine and runs both out drives it has three large v belts from engine to each outdrive its a slick rig very smooth 3.5 gallons per hour from 12 its not as fast he makes 10 knots at 1800 he also makes his own bio diesel from oil he gets from local resturants it has been over three years and he has never tightned the belts I am running his fule in my new catterpillar now it smells like a candle burning and quite a bit more power from it I asked catterpillar if it would hurt my engine or void my warnty they wanted to know how it was refined I told them and they said go for it .His pully system is very nice and so much more room in his engine compartment its a slick rig.

[redhead78]

These mech forums are very interesting, every time I check them out I see a different subject, all relating to our boats, how to fix them, make more comfortable, better, all from different points of view.I always come away a little wiser. Good job all Red

[capn_billl]

For less than 50HP a v-belt s a perfectly good drive if properly aligned. Hydraulics have issues if not maintained also.

[Joe Simmons]

What about electric drive? There is a possible steal on a 40' Graham that needs the diesel rebuilt. It has a good getset. If I buy it I might have the engine/tranny pulled and sell them. I feel like an Etek style motor with belt drive would be very easy to rig up and mount. I'd probably go with a flat belt with teeth. ( I see no reason to ever use a V-belt on a new application.) I think I could get something working for less than $1,000. Later I could put in a variable controller with regeneration if I was going to cruise.

Hydrolic could be nice too. Electric however, would not only be able to regen under sail, you could maneuver in and out of dock off your house bank.

If I do this, eventually I would have (8) 6V batteries, a 48V 200A controller w/ regen. Add some solar panels and I don't think you'd ever need to use your genset again. Only thing you'd need diesel for is a heater. You could even use an induction cooktop. No propane/alcohol.

jenny2 - Your post is unintelligible. Use the 'preview post' function. Maybe throw in some punctuation here and there.

[Dockhead]

Originally Posted by capn_billl

For less than 50HP a v-belt s a perfectly good drive if properly aligned. Hydraulics have issues if not maintained also.

Not directly applicable, but I own a snowmobile with 120 horsepower and a belt drive. The belt drive works hard because it is clutch, transmission, and drive all in one. But properly aligned it is extremely reliable -- got three years out of the original belt.

I can't say that I see anything inherently wrong with a properly engineered belt drive. There's plenty to go wrong with gears running in oil etc. One big advantage of belts is that they are totally simple, visible, and can be replaced in a trice. Some lubrication problem with gear drive and you're in trouble. There's hardly anything that could go wrong with a belt drive that couldn't be fixed by swapping out the belt. I'd say there's a lot to be said for it, actually.

[SkiprJohn]

Don Street talks about them in The Ocean Sailing Yacht. Very interesting and simple concept. I think he had one in Iolaire.

Belt tension and having one belt for each 5hp seems to be the key as well as proper alignment.

kind regards

[Joe Simmons]

What about the drive belts those choppers use between engine and tranny?

Those are 100hp +/- motorcycle engines.

[Blue Stocking]

Some years ago, I had reason to spend a bit of time on slip aboard "Sinbad". a large steel trawler-type yacht, about 80ft.
She had two big Volvos IIRC, sitting high up in the engine room, P & S, with toothed belts driving in a V arrangement to a single shaft, by separate pulley sets.
Hollow prop shaft, through which the variable pitch prop was operated, turning in a pressurized sealed oil bath tube.
Very neat engineering, with which the Pro captain seemed pleased.