- This topic has 3 replies, 1 voice, and was last updated 11 years, 11 months ago by
.
-
Posts
-
-
Rotation and the BW Velvetdrive
Author:
Trying to get a handle on how and which way everything turns in the Pearson. This is with the original W58, Borg Warner Velvetdrive and of course the Walter V-drive.
Starting with what I (think) I know.
– The engine. Facing the front of the engine IE the pulley end of the engine so looking forward in the boat the engine turns CCW. Working from memory since I haven’t run the engine in over four years (sigh, but maybe soon).
– The prop is left handed so looking at the prop from the stern facing forward the prop also rotates CCW.
– The BW Velvet drive can be modified/adjusted so putting the transmission in forward will keep the same rotation or reverse the rotation of the engine.
– Same for the Walter V-drive.
So anyone know the direction of rotation of each part of the drive train as installed in the Pearson? Am I correct that the BW and the Walter can be reversed? Easily?
Other than understanding how it all works I have a more specific reason for asking. The case on the current BW transmission is very corroded due to a leak left for years by the PO and I’m not sure if it will hold up. So I found a used transmission that looks clean. Not sure about the internals but I understand they are worth rebuilding if it’s not trashed.
This leads to the next question. Other than tearing it down to look at the guts or installing it in the boat, is there any way to tell if the transmission is working?
—
Reply Link: <https://www.pearson424.org/tiki/tiki-view_forum_thread.php?forumId=1&comments_parentId=1132#form>_______________________________________________
maillist mailing listhttps://pearson424.org/mailman/listinfo/maillist_pearson424.org
Post generated from Pearson424 Forum using Mail2Forum
-
As far as I know, it’s an industry standard that all these engines rotate counter-clockwise. Here’s what that means.
http://www.ebasicpower.com/faq/rotate.htmThe BW transmission doesn’t reverse rotation. If you had a transmission with a gear reduction it would reverse direction but the output shaft would exit the gearbox lower. Without the gear reduction, the input and output shafts are inline with each other. The gear reduction transmissions are different. You can’t modify the gearbox to reverse direction or give it a gear reduction. It would require that the engine be raised on the engine bed. The boat would have a more efficient power plant if the gearbox had a gear reduction but my guess is Pearson saved a few bucks by using the simpler and less expensive transmission without the gear reduction. At that time, marine engines ran at a slower RPM range and the gear reduction was not considered important. Many of these newer engines have smaller displacement and turn at a higher speed. This makes it hard to find a prop that will properly match the shaft speed at full power. Most engines out there are fitted with a gearbox that have a gear reduction and reverse direction. That’s why most boats use a right-hand prop vs the 424 with a left-hand prop.
The V-drive reverses the direction of rotation, but the output shaft reverses direction (facing aft) so the output is still counter-clockwise with no gear reduction. If you ever replace the V-drive, you can get one with a different gear reduction as I did. This of course requires a different propeller or an engine that spins faster. If your current engine redlines at 2500 RPM and you repower to an engine that redlines at 3100 RPM, you can use the same prop if you change the V-drive gear ration from 2:1 to 2.5:1. If you don’t change the gear reduction, you will cavitate before you reach full power.
The Velvet Drive is a very reliable and robust transmission. Even if the case is corroded, you can probably clean it up and have it serviced. They are heavy but if you have a strong back you should be able to remove the transmission for service. A full rebuild should run less than $1000. If it’s never been done, I recommend having it serviced. The original BW transmissions had some minor problems that have been addressed in later units with different parts. I don’t remember the details but my local shop retrofitted the gearbox when I had it last serviced.
Make sure you follow the owner’s manual when checking the gearbox oil level. It should be checked when warm. If you check it when cold, you can overfill it.
Rich
Original Message
Post generated from Pearson424 Forum using Mail2Forum
-
Thank you Rich for the information.
First I looked at the link you posted about engine rotation. According to the info on that link the proper way to designate engine rotation is from the flywheel end. So I went out to the boat over lunch and bumped the starter. Confirmed my memory was wrong. From the front, pulley end of the block the rotation was CW so using the proper terminology referencing the flywheel side the rotation is CCW or left hand.
Using your information on the Velvetdrive I did some further google searches and found a website that gave specs for the BW 71/72 transmissions. It listed several variations and stated there are direct drive and reduction versions. most popular is the inline. It wasn’t totally clear the way the doc was written but I think it was saying there is an inline version that is also reduction? It also showed the 1:1.88 reduction reverse the rotation of the engine at the transmission output but all others maintain the same rotation.
http://www.velvetdrive.com/techinfo/V7172/V7172pg1.pdf
Also looked at the used Velvetdrive which the seller told me is reversible to allow counter-rotating props with engines turning the same way. On the end of the Velvetdrive that mates to the engine there’s a metal plate bolted to the transmission. Cast into one side it says “RH this side up”. Opposite side it says “LH this side up.” So what the heck does that mean? It is a 1:1 drive by the way so no reduction.
However for my immediate purposes I guess this is all moot since from what I’m learning in the Pearson the Velvetdrives will all rotate the same and the change is in the V-drive. So if I needed I could swap out mine without worrying about that detail.
Now if I can figure out how to tell if this one is functional as is without tearing it down. Would also be very interesting to know about the upgrades incorporated in your rebuild.
Post generated from Pearson424 Forum using Mail2Forum
-
Skip
Here are my notes from when I repowered.http://www.richardcarter.net/repower/
Rich
Original Message
Post generated from Pearson424 Forum using Mail2Forum
-
- You must be logged in to reply to this topic.