Can anyone tell me what the continuous max HP spec is for a Paragon SA0 sail gear. I need to know if I should refurbish or upgrade. My motor produces 55 HP and 102 ft/lbs of torque continuously. A Hurth ZF12M would be ideal (53 hp cont duty 72 hp peak).
Pretty sure that exceeds what the Walter v-drive can handle as well. Maybe I need to re-power to a smaller motor. I'm Just kidding. Pete
Did some research on the SA0. My guess is that Henry Ford didn't know what the HP rating was either when it first put it in the Model T (its true). My concern is based in the realization that regardless of how well I polish and paint it up, it remains obsolete and is the weakest link in my drive train and something that cannot be repaired. Especially in some port outside the US. So it has to go. Most people worry about their Diesel engines failing. I worry about the clutch.
Found a bit of useful info from former Pearson 365 owners on this site that have since moved on to bigger better boats. When re-powering to more horse power and including a modern transmission there is a single formula that seems to work.
Step 1: Re-gear the RV-10 V drive to 1:1: ratio. The most important advantage to this move is higher HP rating. At 1:1: the RV-10 is rated at 2.7 x 100rpm/HP for gasoline. De-rating by .75 for diesel sets the max HP rating at 61 HP for light duty. De-rating further for continuous duty puts you at 46 HP. A bit of an overload for a 55 HP motor. AT the standard 2:1 the V drive derates to 33 hp max. I'm waiting to hear back from Walter about this modification.
Step 2: Install a modern Hurth 2:1 gearbox. The HBW150 (ZF15M) is currently in production, used in new boats and parts are available anywhere. I have a call into Tad to determine if Hurth offers direct drive 1:1 ration on anything. Or anyone for matter. I think not. If so I'm looking at an RV20 or 26 V drive at 2:1 to meet the HP rating. No Idea if it will fit. Also moving the gear reduction ahead of the V drive doubles the torque. Another reason why the RV-10 may be now be to small.
I know there are a bunch of Pearsons out there running the Paragon PM10L boxes. Also Obsolete and heavy too. I saw a rating at that box at 170 HP. Seems like overkill. No offset either and its long.
If Walter Machine goes under I'm not sure what we all will do with Pearson being the only Sailboat I know with this drive train configuration. We will have to re-power with the Volvo one piece sail drive system that goes through a 2 foot hole the hull. Time to stock up on spares if you can find them.
Pete
Pete,
Have you considered the BW71C Velvet drive? It may be a bit heavy for you but it will take any horsepower you will put into it with your diesel. I have owned a few and they are nice and smooth and do not require hold the lever for reverse. The good news is there are plenty in the used rebuilt category out there which helps on the cost aspect.
Walter V-drives are widely used in skiboats. They are not necessarily the small ones like we use, but I wouldn't be to worried about Walter. A bigger concern would be the low sulfur diesel fuel that the government is jamming down our throats. Old engines, new style of fuel, equals yet another not so well thought out mess. Oh I forget, we all are the top 1% being boat owners so we can afford to change out that diesel engine.
Dale
For Pearson boats with the gear reduction in the V-drive ( where it belongs for good reasons) a direct drive transmission is an optimal design. For my boat which has been re-powered with a larger engine, direct drive with offset is a desirable solution for several reasons. Offset will allow me to lift the rear engine mounts and flatten out the motor installation. This might keep all that engine oil from collecting over #4 under the rocker cover and helps with drive shaft placement.
The Velvet Drive 5000A series transmission is 12" long, has 6" of offset and 8 degrees down angle at the output and comes in 1.05:1 ratio. Its a 150 HP commercial rated gearbox much like the 71C Series and the Paragon PM10L boxes. An expensive, overdesigned yet reasonable solution for my boat.
http://www.velvetdrive.com/5000.html (http://www.velvetdrive.com/5000.html)
Keeping the 2:1 gear reduction in the v-drive has the added benefit of allowing the clutch and drive train to feel 1/2 the torque that the prop shaft feels. That's because it spins at twice the speed.
Gearboxes such as the Hurth types, put the gear reduction before the clutch. Hence these clutches slip more, run hotter and burn out frequently because they feel 2x the torque of the motor. I'm not pleased with Hurth's failure rates on these designs which have no margin in their specs. As a result I would de-rate further beyond the heavy duty commercial rating, and insist on an oil cooler. So for a 55 HP motor I need a Hurth ZM30 which is a 128 HP light duty rated gearbox. Its 10" long but with offset and half the weight of the Velvet Drive.
To solve the torque problem I would need to see if a larger RV-20 (26) v-drive will fit and have Walter machine set it up for 1:1. ( I can hear them grumbling now) My gearbox choice options are greatly enhanced by re-gearing the V-drive but on the downside it will double the torque requirement on the v-drive.
Or I could take Dales advice and try to fit 71C Velvet drive in there. $1450 rebuild from TAD.
Dale, I was up your way in S Wales a couple of weeks ago and would have stopped by but it was a week day. Nice barn you have over there.
Pete
Pete,
Please stop next time you are out my way, I would love to meet you and shake your hand. Glad you like the boat barn. Even if I am not home the barn is always open, help your self and take a look.
Found this on the Pearson 40 web site and it should be very helpful to you, hope this helps...
http://www.pearson40.net/velvet%20drive%20files/paragon_to_velvet.htm
Dale