How does it work?

[RLWP]

The teeth of the small reverse gears, but only when the gearbox is in neutral.

 

(Lister gearbox, that's the only one I know about.)

 

MP.

 

Planet gears. It's a bit academic really - what about the teeth of the small bevel gears in the Parsons box then?

 

Richard

Edited October 10, 2011 by RLWP

[MoominPapa]

Planet gears. It's a bit academic really - what about the teeth of the small bevel gears in the Parsons box then?

The axis of rotation of those is perpendicular to the axis of rotation of the box as a whole, so it gets a bit more complicated, I think (!?)

 

MP.

[alan_fincher]

I think it's rather confusing to bring the Blackstone box into it.

 

Same effect, but achieved a different way.

 

The dismantled pictures of Parsons one that Richard posted manage to show a lot of what is hidden in Sarah's "cover off" picture.

 

Specifically this shows the bevel gear on the output shaft

 

 

and this one of the smaller bevels at 90 degrees to it.....

 

 

 

All that is normally hidden away under the brake band in Sarah's picture, which is why she is not really seeing gears just by taking the cover off. In ahead gear, as Tim has said, the clutches lock the input and output together, and absolutely none of these gears are turning relative to each other. That only starts to happen in reverse.

 

It is absolutely, definitely, and beyond doubt, a feature of these boxes that they do make a lot of noise with reverse engaged. It is absolutely nothing to worry about. The most evocative memory I have of the Willow Wren fleet passing through were the different noises the boats made as they worked through locks. By sound alone, there is absolutely no doubt when one of these boxes is in reverse. Just enjoy!

 

EDITED" to take the "fears" out of "gears"!

Edited October 10, 2011 by alan_fincher

[RLWP]

The axis of rotation of those is perpendicular to the axis of rotation of the box as a whole, so it gets a bit more complicated, I think (!?)

 

MP.

 

It's probably another cycloid described on the surface of a cylinder - something to ponder as you put the box in reverse at a bridge hole

 

 

Richard

 

<snip>

 

that Richard posted

 

<snip>

 

Not me, it was Evo what found them

 

Richard

[alan_fincher]

Does this help at least those who understand engineering drawings ?

 

To make it slightly more obvious, I have got my "crayons" out...

 

Forward bevel (drive from engine) - Yellow

Aft bevel (drive to reduction gear in Sarah's case, although this picture is a direct drive gearbox) - Orange

(Two times) "Bevel pinions" - Blue

 

The clutch plates that lock it up for forward gear surround the aft bevel.

 

 

Clear as mud ?

[RLWP]

Well, apart from the fact that the 'ahead' bevel is only used in reverse, I guess that is right...

 

In forward, the plate clutch appears to lock the output shaft to the 'planet' gear carrier meaning the whole assembly rotates - gears, carrier, clutch. everything. In reverse, the plate clutch is free and the band brake works locking the carrier. The yellow gear drives the blue ones, which drives the orange one and the output shaft backwards

 

Richard

 

I may have my forwards and backwards backwards

Edited October 10, 2011 by RLWP

[alan_fincher]

In forward, the plate clutch appears to lock the output shaft to the 'planet' gear carrier meaning the whole assembly rotates - gears, carrier, clutch. everything. In reverse, the plate clutch is free and the band brake works locking the carrier. The yellow gear drives the blue ones, which drives the orange one and the output shaft backwards

Yes,

 

I believe so.

 

(To all of that!)

[Chertsey]

 

 

All that is normally hidden away under the brake band in Sarah's picture, which is why she is not really seeing gears just by taking the cover off. In ahead gear, as Tim has said, the clutches lock the input and output together, and absolutely none of these gears are turning relative to each other. That only starts to happen in reverse.

 

It is absolutely, definitely, and beyond doubt, a feature of these boxes that they do make a lot of noise with reverse engaged. It is absolutely nothing to worry about. The most evocative memory I have of the Willow Wren fleet passing through were the different noises the boats made as they worked through locks. By sound alone, there is absolutely no doubt when one of these boxes is in reverse. Just enjoy!

 

EDITED" to take the "fears" out of "gears"!

Ah yes, I see it. This is really starting to make sense now.

[Timleech]

It's probably another cycloid described on the surface of a cylinder - something to ponder as you put the box in reverse at a bridge hole

 

 

 

 

I've heard that style of box referred to as 'concyclic', but I have no idea whether there's any proper basis for that name.

 

Tim

[bizzard]

Well, apart from the fact that the 'ahead' bevel is only used in reverse, I guess that is right...

 

In forward, the plate clutch appears to lock the output shaft to the 'planet' gear carrier meaning the whole assembly rotates - gears, carrier, clutch. everything. In reverse, the plate clutch is free and the band brake works locking the carrier. The yellow gear drives the blue ones, which drives the orange one and the output shaft backwards

 

Richard

 

I may have my forwards and backwards backwards

Don't be backward in coming forward.

[Chertsey]

Well, having started out confused, briefly become even more confused, I think I can say now that I have a rudimentary grasp of it. I will go back over some of the earlier posts and links to try and consolidate it, but I certainly know (and understand!) a lot more than I did twelve hours ago. Thanks everyone!

[bizzard]

Is this another interlude?

If so i've another story.

[Guest]

Is this another interlude?

If so i've another story.

 

I think it's the finale - off you go..

[bizzard]

I think it's the finale - off you go..

I'd better wait its 4pm, afternoon tea and biccy's,whilst everyone double checks their manuals and data on the the subject,and rejoins the fray.

 

We'd better get the Potters wheel out.

Edited October 10, 2011 by bizzard

[bizzard]

Afternoon teas interlude over. So whilst everyones regrouping i'll get on.

Do away with wretched gearboxes altogether and install a marine steam engine,ie Sissons or similar.

No gearbox required as propshaft is connected directly to engines crankshaft.

As a steam engine will deliver and start on full power from rest therefore needing no form of gearbox or clutch.

Reverse is obtained by altering the addmission and exhaust valve events ''the cut off or reverser'' beautifully simple,but requires a large space for that potential ''bomb'' ''The boiler.'' bizzard.

Edited October 10, 2011 by bizzard

[alan_fincher]

Afternoon teas interlude over. So whilst everyones regrouping i'll get on.

Do away with wretched gearboxes altogether and install a marine steam engine,ie Sissons or similar.

No gearbox required as propshaft is connected directly to engines crankshaft.

As a steam engine will deliver and start on full power from rest therefore needing no form of gearbox or clutch.

Reverse is obtained by altering the addmission and exhaust valve events ''the cut off or reverser'' beautifully simple,but requires a large space for that potential ''bomb'' ''The boiler.'' bizzard.

Apart from the "bomb" bit and the references to steam, you could almost be describing a Bolinder semi-diesel ?

 

It's true they avoid the complexities discussed in the previous thread, (but, although having no personal experience, I do gather they introduce a few of their own......)

[bizzard]

Apart from the "bomb" bit and the references to steam, you could almost be describing a Bolinder semi-diesel ?

 

It's true they avoid the complexities discussed in the previous thread, (but, although having no personal experience, I do gather they introduce a few of their own......)

Yes quite, they didn't need a gearbox, just used the propeller and canal water as a clutch.

The boiler is always the headache,fairly regular inspections and pressure tests,blowing down and washing out very regularly especially if the feed waters hard,although softener tablets can be put in the water tank,sweeping firetubes,testing your safety valves frequently ect,maintaining boiler feed water pump and or injector,water level in the boiler and shoveling coal on the fire. The engine part itself once adjusted to run sweetly only requires regular oiling of parts,and minor adjustments,topping up cylinder lubricators with steam oil.As they're usually open frame machines and have a total loss lube system,so quite expensive on oil.

Yes a lot to do really but very satisfying and rewarding. And almost silent whilst running,until you let the boiler pressure build too much and it blows off excess steam.

[FORTUNATA]

I know what you're driving at. The manuals don't quite pull the whole thing together and explanations are a bit vague.

I know of 2 basic gearbox functions for my own Lister engine and can only conclude you need to first understand manual operation before being able to grasp hydraulic. With manual, there is a basic clutch and number of sprockets. In neutral, the clutch body spins but not the main shaft. There is an ahead shaft which when rotated manually, pushes a roller across a cam lever which in turn releases pressure on springs, allowing the inner clutch to release and bite with the main shaft as it moves position. So spring pressure and the cam levers as well as clutch operating yoke all work together.

For reverse as you state there is a brake band. When the cams are moved for aft by the operating lever the brake band tightens around the clutch body.

Actually for me it's a bit vague too. I'm familiar with the various components of a gearbox such as inner clutch cone assemblies, operating yokes, rollers and so on but I'd like to see one working to get the full picture.

As for hydraulic I assume it just does the same thing as manual except there's a selector valve and adjustable piston mechanism and much of this can be accessed for maintenance.

 

I wonder if this has the potential to become a new sub-forum, where people with furrowed brows (like me) can get a simple explanation, with pictures, of how some bit of equipment or technology works. Not when it goes wrong, but just how it works normally.

 

One thing that has mystified me forever is how reversing boxes work. This began with Warrior's occasionally temperamental Bruntons box which I am told has a sliding shaft, but I think I will leave that for the advanced class.

 

For now I will be happy if I can understand how Chertsey's Parsons box works (I think it's a type F but I have left the manual on the boat. Yes, I have the manual but it doesn't help me!). We had the cover off it the other week to adjust the brake band and I was able to look inside. I was even able to follow the instructions in the manual to make the adjustment (well, PB did the adjusting but I was reading the instructions). I gazed in wonderment at the contents looking as clean and new as when they were made in 1960-ish, isn't oil wonderful.

But I still do not understand how it actually works. Over to you, CWF teachers.