Author Topic: LPW 3  (Read 339 times)

Quince the Carpenter

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LPW 3
« on: April 25, 2019, 11:02:39 PM »
Hi all,
I bought an LPW3 a few years back to replace an aging (and underpowered) SW2.  Only just now getting around to it! It's going into an 8 tonne auxiliary yacht here in NZ. Belt drive variable pitch prop, so no gearbox issues...
I'm in the process of bench testing the engine, and discovered that it appears the engine is governed to about 1500 rpm. The engine has never been run before, and it came from a generator supplier who'd over-stocked on engine replacements. I got lucky.
My question is:
Can I, or should I, replace the governed system with a throttle controlled system? Is it better for the engine to run at a constant revolution? I can vary the prop pitch at will, so no issues with power output.

cobbadog

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Re: LPW 3
« Reply #1 on: April 26, 2019, 06:51:24 AM »
In my humble opinion I would prefer a throttle governed engine so you can have more control in conjunction with your variable pitch prop. Fixed revs to me scare me especially at start up. If it has been sitting for a while all the oil is down in the sump then once started it is straight to full revs while the il is being picked up, excessive wear comes to mind.
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glort

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Re: LPW 3
« Reply #2 on: April 26, 2019, 08:58:56 AM »

How would you dock a boat and manouver it with a fixed throttle? Surely the prop can't have that much pitch variation?

What is the max RPM of the engine. If it's 2200 or so you are going to be down a fair bit of HP at 1500.  Boats dont vary RPM like a car, you could still cruise at 1500 Rpm if you had a throttle adjustment But have max power if you ever needed it.  Apart from that, I would MUCH prefer to back the engine down and pitch the prop up so one could have a more relaxing cruise  rather than have the thing pounding away as they seem to sound even when the RPM is low when you just did want to meander along and enjoy the scenery.

I agree with Cobba, Straight to full rpm from cold wouldn't be the best. a Lot of these generators have sump heaters when used in backup/ emergency applications so they can reliably go from a cold start to full tilt.

Not much of a boatie but I can't think of a single advantage to having  a fixed RPM in a boat but I can certainly think of a LOT of drawbacks!
The more nautical minded may have some positive reasons but They would have to be pretty substantial to outweigh the drawbacks I can see.

dieselspanner

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Re: LPW 3
« Reply #3 on: April 26, 2019, 12:36:03 PM »
Hi Quince

I like the set up, the lack of a gearbox is good with the belt drive takes out all the alignment problem. I've worked with VP props - and Kitchener gear - and believe that, properly maintained they are as reliable as a gearbox.

You could get away with fixed rpm, imho, but I agree with most of the reasons above for having a throttle, and also that warming up on tick over or leaving the engine running to heat domestic water / charge the service batteries would be far more comfortable.

An outfit I've worked for before had a V8 GMC in a work boat, it was reputed to have come out of a small tank and went from tick over to flat out with very little adjustment in between, consequently it was hard on gearboxes when shifting from ahead to astern, something a work boat does a lot of...

With the revs fixed you may find the same wear issues on the VP prop. If you could link the pitch control to the throttle to drop the revs as you passed thro' the neutral point it would save all sorts of wear on the thrust bearings etc. and give you a smoother input of power to the prop.

It's not an engine I'm familiar with, doubtless others here will help, but given the numbers of the LP motors out there I don't think there would be too much difficulty with the throttle and I'd hope that a variable speed governor would be an easy swap.

Looks like an interesting project, keep posting as it develops!

Cheers
Stef
Tighten 'til it strips, weld nut to chassis, peen stud, adjust with angle grinder.

Quince the Carpenter

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Re: LPW 3
« Reply #4 on: April 26, 2019, 09:01:10 PM »
Hi, Thanks for the responses.
Part of the reason for my query, is that I too, would prefer to idle the engine while warming up and close manoeuvring, but from my preliminary investigation of the throttle base plate it didn't seem obvious to me how to do it. I didn't want to mess with it (if it ain't broke....), and upset the governor setting.
I backed off the throttle stop, (in the foreground of the photo) and took a few turns back off the middle screw, but it didn't made an appreciable difference. The plate doesn't touch the back screw, confusing me further...
 It got me thinking that it would be smart to ask for advice, before I upset everything!

So, can I play with those screws without damaging anything?
Appreciate any comments.

PS, the prop can go from horizontal (for sailing) right through to reverse pitch. There's a lay shaft that sits on a cam to make slack for starting and charging.

glort

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Re: LPW 3
« Reply #5 on: April 26, 2019, 11:19:08 PM »

The 2 Screws on the top close together are the speed screws.  Back them Right out and you should have throttle control. The plate will have to move freely, ATM it looks like the 2 bolts close together are holding it captive.  The long one in the foreground should be Max speed.
By default the thing should go to idle and turning should increase RPM from there.  As you back off the screws, watch which way the arm moves. Reverse should be throttle increase.

Once it moves around, fire it up.  If it goes to full RPM just turn the plate to back it off or use the fuel cut off in the front of the pic.
This is a very simple system, Much more simple than I would have expected actually but once you get the throttle free to travel, You can rig up a cable in the round slot  and have full control.

Quince the Carpenter

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Re: LPW 3
« Reply #6 on: April 26, 2019, 11:50:15 PM »
Wonderful.
Just the news I want.
Thank you

sirpedrosa

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Re: LPW 3
« Reply #7 on: April 27, 2019, 12:51:49 AM »
Hi Everyone

As far as I can see in pic, I think it has the throttle linkage broken, I mean it laks that part fixes the cable enabling remote throtlle. Wont you agree?

Just my vision...

BR
VP
« Last Edit: April 27, 2019, 12:53:25 AM by sirpedrosa »
Bernard 18A - 1968 (mama's water pump - year of my birth)
Petter PAZ1 - Jun 1967, 3HP, sn 416xxxx

Quince the Carpenter

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Re: LPW 3
« Reply #8 on: April 27, 2019, 12:58:11 AM »
Ya. Something fell on the cast alloy hook...
Will have to invent something...

cobbadog

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Re: LPW 3
« Reply #9 on: April 27, 2019, 06:00:39 AM »
Now I've seen a pic of what you have I thought that a cable could be attached to the throttle cam just to the right of the very top bolt. It appears that a heavy cable would drop down that hole and the cable then go to the right and fit into what seems to be a groove. If this is the case I would certainly have a go at the adjustments suggested by Glort. In case there is an issue, count how many turns you do on each bolt to get it out of the way so they can be reset to the same position. Connecting the VP to the throttle also sounds a good idea.
Let us know how you get on.
Coopernook - the centre of our Universe.