Lister LH150 Reversing Box

[paulcatchpole]

Hi all,

 

Thought I'd separate this to see if we got any more ideas...

 

This is our LH150 on the end of an unknown-quantity SR3 which we started for the first time yesterday, after it'd been sunk and all sorts.

 

We ran it with the reduction box off, and beforehand the output shaft of the LH150 had 1/2" of free end-float play, now it's been run, it has none, at least by hand...

 

The engine made a few slightly-sickening baulking/graunching squeals whilst running, which lasted at least a few RPM each time... I could ascribe these to the hand-start freewheel, knackered alternator bearings, loose pulley and the like, but I'm worried it may have been the reversing box.

 

Here're the pics of the box, can someone tell me if this looks okay or not?

 

 

 

 

 

Can anyone tell me whether that looks good/bad/ugly?

 

I've filled it full of diesel at the moment, in the hope of cleaning it out a bit - hope that wasn't the wrong thing to do either! Said diesel is pouring out of around the output shaft where it emerges into the reduction casing - would that be a knackered output seal, or is it more that I've brimmed it above where oil would normally be?

 

It's a bit slimey and grungy but not half as bad as the reduction. No water in it either, for a change.

 

PC

[paulcatchpole]

Been to the boat today, emptied all the diesel and remains of old oil out - the drain plug looked like this:

 

 

Hmm - I take it it's not supposed to be quite that gungy?

 

Anyhow, bunged some fresh EP80 in, after cleaning up the top cover and gasket...

 

Also, tried what Dave had suggested with the replace-the-screw to get it to release into neutral - which didn't quite work. With the original screw, or no screw, the output shaft won't move at all - locked in forward, as expected.

 

With the lever over so it should've been released, it allowed me to rock the output shaft through ten degrees or so, and also the end float, which is probably actually about 10mm, returned.

 

There's a video here, of the movement:

 

 

What do the experts say to this?

 

Furthermore, I ran the engine again for a good five mins, and managed to get the gear selector to move. In neutral or reverse positions, I get forward, whether I like it or not. If I select forward, the box stalls the engine - is this the infamous ahead-and-astern at the same time trick?

 

Could really do with some guidance on where to go from here, please!

 

PC

[springy]

Having watched the video I would say no it shouldnt be doing that. I'm

wondering about your description "you get forward in neutral or reverse and

stall in forward - doesn't make sense. If you got forward in forward and neutral,

and stall in reverse - makes perfect sense - forward friction band stuck in - hence

you always get forward, but when you apply the reverse friction band you try and

get forward and reverse at the same time - hence stall. Does the reduction gear

reverse the rotation ?

At least it does mean that the hydraulic pump is working because it succesfully

activates the friction band.

Cant remember if this has already been mentioned but these gearboxes are held in

forward by a spring pack, hydraulic pressure is used 1) to disengage forwards (ie

engage neutral) and then 2) engage reverse. Consequently sticking in forwards is

always a potential problem - particularly if the box has been submerged.

On the other hand if the hydraulics fail for any reason you STILL have fowards gear

- will get you home (even if you have to use the harbour wall for brakes).

 

edited to add - looking at the photos - is the "forward" friction band breaking up (ie

the inner one) - it looks somehow uneven.

 

springy

Edited May 3, 2010 by springy

[paulcatchpole]

Having watched the video I would say no it shouldnt be doing that. I'm

wondering about your description "you get forward in neutral or reverse and

stall in forward - doesn't make sense. If you got forward in forward and neutral,

and stall in reverse - makes perfect sense - forward friction band stuck in - hence

you always get forward, but when you apply the reverse friction band you try and

get forward and reverse at the same time - hence stall. Does the reduction gear

reverse the rotation ?

 

Ta for the reply...

 

I definitely got what was written above, as in forward with engine off (as expected), forward with neutral selected and engine running, forward with reverse selected and engine running. It stalled with forward selected and engine running.

 

At least it does mean that the hydraulic pump is working because it succesfully

activates the friction band.

Cant remember if this has already been mentioned but these gearboxes are held in

forward by a spring pack, hydraulic pressure is used 1) to disengage forwards (ie

engage neutral) and then 2) engage reverse. Consequently sticking in forwards is

always a potential problem - particularly if the box has been submerged.

On the other hand if the hydraulics fail for any reason you STILL have fowards gear

- will get you home (even if you have to use the harbour wall for brakes).

 

springy

 

How do we get to the point the pump works?

 

Also, bear in mind it wouldn't release to neutral using the extended-bolt trick either, it just sat there with the play that's shown in the video...

 

No worries about the dock wall, this is on hardstanding at the moment, but launching soon!

 

PC

[springy]

<snip>

I definitely got what was written above, as in forward with engine off (as expected), forward with neutral selected and engine running, forward with reverse selected and engine running. It stalled with forward selected and engine running.

<snip>

 

Curious

 

How do we get to the point the pump works?

 

The fact that it stalls means that it is trying to engage both gears at once. The fact that this

happens when you operate the gearchange means that the the pump & associated valves pistons

etc must be operating (to some extent at least)

 

Also, bear in mind it wouldn't release to neutral using the extended-bolt trick either, it just sat there with the play that's shown in the video...

 

Implies that the forward friction band is stuck in the engaged position or broken up and

jaming in the engaged position.

 

springy

[paulcatchpole]

Curious

 

The fact that it stalls means that it is trying to engage both gears at once. The fact that this

happens when you operate the gearchange means that the the pump & associated valves pistons

etc must be operating (to some extent at least)

 

Implies that the forward friction band is stuck in the engaged position or broken up and

jaming in the engaged position.

 

springy

 

Right, I get you on the hydraulic pressure...

 

Spotted your earlier edit, which bit in which piccy is that? I've still not managed to get my head around how this is supposed to work!

 

edited to add - looking at the photos - is the "forward" friction band breaking up (ie

the inner one) - it looks somehow uneven.

 

When it breaks up, what does it do? Thinking back to poking the brake-drum shaped thing, I think it looked and felt like two friction bands bonded to a central metal band, like a double-sided brake shoe, but I could have imagined that! The whole thing moves, certainly...

 

Ta for the help!

 

PC

[springy]

Hi Paul

 

 

In the following image the forward friction band is the double hatched item between

D and E, on your second photo it appears to be sticking out a bit at 3 o'clock and 9

o'clock positions.

 

The Reverse friction band is the double hatched item on the outside of item D.

 

In forward gear D is locked to E (held in place by the spring pack), in neutral the spring pack

is overcome by the hydraulic piston J, and for reverse the outer brake band is applied thus

locking D to the body of the gearbox and the drive passes through an epicyclic gear train to

provide reverse rotation (not very clearly shown on the left of this image).

If D and E stick together or the friction material breaks up and jams them then you would

get the situation described - always in forwards & locks up when reverse is selected.

 

springy

 

 

[RLWP]

Hi Paul

 

 

In the following image the forward friction band is the double hatched item between

D and E, on your second photo it appears to be sticking out a bit at 3 o'clock and 9

o'clock positions.

 

The Reverse friction band is the double hatched item on the outside of item D.

 

In forward gear D is locked to E (held in place by the spring pack), in neutral the spring pack

is overcome by the hydraulic piston J, and for reverse the outer brake band is applied thus

locking D to the body of the gearbox and the drive passes through an epicyclic gear train to

provide reverse rotation (not very clearly shown on the left of this image).

If D and E stick together or the friction material breaks up and jams them then you would

get the situation described - always in forwards & locks up when reverse is selected.

 

springy

 

Out of curiosity and no more, because of the epicyclics, does the box have a different drive ratio in forward and reverse then?

 

Richard

[springy]

Out of curiosity and no more, because of the epicyclics, does the box have a different drive ratio in forward and reverse then?

 

Richard

 

 

Not 100% sure but it does ring a vague bell that there is a slight difference - on the

gearbox ignoring reduction, ahead is direct drive - for efficiency, reverse goes via

epicyclic and is IIRC a slight reduction.

 

springy

[paulcatchpole]

Hi Paul

 

 

In the following image the forward friction band is the double hatched item between

D and E, on your second photo it appears to be sticking out a bit at 3 o'clock and 9

o'clock positions.

 

The Reverse friction band is the double hatched item on the outside of item D.

 

In forward gear D is locked to E (held in place by the spring pack), in neutral the spring pack

is overcome by the hydraulic piston J, and for reverse the outer brake band is applied thus

locking D to the body of the gearbox and the drive passes through an epicyclic gear train to

provide reverse rotation (not very clearly shown on the left of this image).

If D and E stick together or the friction material breaks up and jams them then you would

get the situation described - always in forwards & locks up when reverse is selected.

 

springy

 

Righty, well, I see what you mean about the band between D+E, and I'd have to agree that it does seem to stick out beyond the outer one of those - which is it supposed to be attached to - D or E (or neither? ) ?

 

I wonder if I managed to engage reverse then, when I thought I'd got forwards? It stalled with the selector arm all the way sternwards, whereas in the middle and all the way forwards, it ran in forward-gear. Does that help?

 

As has been pointed out elsewhere, there's been a lot of tinkering going on on this boat prior to us owning it - is there a change this may just be way out of adjustment?

 

PC

[springy]

Righty, well, I see what you mean about the band between D+E, and I'd have to agree that it does seem to stick out beyond the outer one of those - which is it supposed to be attached to - D or E (or neither? ) ?

 

IIRC forward band is attached to item E, reverse band is attached to the thin steel band which

surrounds the whole assembly.

 

I wonder if I managed to engage reverse then, when I thought I'd got forwards? It stalled with the selector arm all the way sternwards, whereas in the middle and all the way forwards, it ran in forward-gear. Does that help?

 

As has been pointed out elsewhere, there's been a lot of tinkering going on on this boat prior to us owning it - is there a change this may just be way out of adjustment?

 

PC

 

Is the selector arm still attached to the morse control (if applicable) and does that

give the appropriate mapping ie forward/reverse.

 

Actually, pushing the selector arm forwards to engage forward and pulling it back to engage

reverse does make sense.

 

springy

[paulcatchpole]

IIRC forward band is attached to item E, reverse band is attached to the thin steel band which

surrounds the whole assembly.

 

Is the selector arm still attached to the morse control (if applicable) and does that

give the appropriate mapping ie forward/reverse.

 

Actually, pushing the selector arm forwards to engage forward and pulling it back to engage

reverse does make sense.

 

springy

 

The morse control is still attached to the gearbox, yes, but not to the boat! It's on a piece of wood which could've conceivably gone either side at the stern, but I'd assumed port, which is where I got the idea that I'd engaged forward and it stalled, rather than reverse...

 

Hmm, I wonder what's actually gone wrong with the box then - have we reached a conclusion that something's happened to the friction material in terms of it falling off? I guess it's worth following the manual as far as adjustment goes, to see if I can get it to release with the swap-the-screw trick - or would the adjustment not affect that?

 

Interesting about the ratios in forward against reverse...

 

PC

[RLWP]

My reading is that you have either got the friction material come away on a band or cone. Or more likely, one of them is jammed together - probably the forward cone.

 

Richard

[paulcatchpole]

My reading is that you have either got the friction material come away on a band or cone. Or more likely, one of them is jammed together - probably the forward cone.

 

Richard

 

Hmm, I'll have to have a good poke around and see which is which then!

 

What're your thoughts on reasons for it to get jammed - physically due to deformation, or stuck from contamination/lack-of-use?

 

Hope it's just stuck and not fallen apart!

 

Glad you're seeing the wood despite the trees - I'm not very good at gearboxes, apart from the usual constant-mesh car type!

 

PC

[alan_fincher]

Out of curiosity and no more, because of the epicyclics, does the box have a different drive ratio in forward and reverse then?

 

Richard

 

Don't know about the Lister box, and have not studied the diagrams, so this may not apply.

 

But on a box I had on a previous boat, you could think of it a bit like the mechanism of a car differential, where the input from the engine, and the output to the reduction gear were equivalent to the two half shafts connecting to the wheels of a car, but where there were no other connections to it, so the whole of the bit containing the gears could turn itself, if allowed to.

 

By locking the whole thing together, so that the whole thing turned with no gears actually moving, you got forward drive, with no reduction.

 

But by clamping the part containing the gears with a brake band, so it could not turn, then instead the gears turned, and the output shaft turned in the reverse direction to the input.

 

If you think of jacking the back end of your Midget up, whilst left in gear, (with the engine off!), as you turn one rear wheel in one direction, the other one will rotate at the same speed but in the other. That's how reverse works on that type of marine box.

 

So there is no reduction whatsoever, in either forward or reverse on such a box. Any reduction is added by the seperate box, and comes afterwards.

 

Of course it's because there are no moving parts in forward gear, but all the cogs turn in reverse, that such a box tends to whine only when running backwards. I'm led to believe if you try using a wrong handed prop on such a box, so that you need to engage what is meant to be reverse, but to go forwards, then they have a very short life before needing a lot of work.

 

Apologies if this box is not of this type - it was a Parson's box I'm describing.

 

EDIT:

 

Actually I started to post the above in haste, and am no longer convinced this is a similar design box to what I'm talking about. Should probably have kept my mouth shut!

Edited May 4, 2010 by alan_fincher

[RLWP]

No, you're about right. There's a set of epicyclic gears sat in the middle of the box with a band brake on the outside of the ring gear. As you say it works by locking up different parts of the epicyclics - the ring gear or the spider usually.

 

Richard

[alan_fincher]

No, you're about right. There's a set of epicyclic gears sat in the middle of the box with a band brake on the outside of the ring gear. As you say it works by locking up different parts of the epicyclics - the ring gear or the spider usually.

 

Richard

OK, then,

 

Whilst I guess you could contrive to make it other than 1:1 when running in reverse, I really cannot conceive why you would make it anything else.

 

Someone will tell me I'm wrong though, I guess !

[paulcatchpole]

No, you're about right. There's a set of epicyclic gears sat in the middle of the box with a band brake on the outside of the ring gear. As you say it works by locking up different parts of the epicyclics - the ring gear or the spider usually.

 

Richard

 

Hmm, I'm finally getting it...

 

PC

[MoominPapa]

Hmm, I'm finally getting it...

 

PC

This is my understanding of how it works.

 

The input shaft is the "sun gear" in the centre, the output shaft is the ring gear around the outside, the planet gears are between the two on a spider which is free to rotate except when locked by the reverse brake-band. The forward clutch locks the input and output shafts together and the whole assembly rotates with no relative movement between the parts. In neutral the ring gear it stationary and the sun gear is moving. The spider rotates at half-input speed to allow this. In reverse the spider is locked and the planet gears are turned by the input sun gear and rotate the ring gear backwards.

 

What's clever is that in forward the only bearing surfaces that are actually moving and wearing are the shaft bearings and the forward selector fork. On the older manual boxes like I have, the while rotating assembly hangs off the end of the crank, so one of these bearings is the end engine main bearing, the other one is the reduction box bearing.

 

MP.

[RLWP]

OK, then,

 

Whilst I guess you could contrive to make it other than 1:1 when running in reverse, I really cannot conceive why you would make it anything else.

 

Someone will tell me I'm wrong though, I guess !

 

It's a feature of using epicyclic gears. You'd aim for 1:1 forward and take what ever happens in reverse. So you ruling design decision is to use an epicyclic cluster and a band brake for reverse and live with the different ratio.

 

Other boxes solve this in different ways with different results, like 1:1 in reverse and a second set of pistons, clutch plates and bearing shafts

 

Richard

 

Engineering isn't it. The world of compromise

[alan_fincher]

Engineering isn't it. The world of compromise

Is it ?

 

Why would you want a simple "marine" box to have a different ratio in one direction, than in the other ?

 

Just curious.

[RLWP]

Is it ?

 

Why would you want a simple "marine" box to have a different ratio in one direction, than in the other ?

 

Just curious.

 

You wouldn't! But you might want a simple marine box where forward gear is delivered in the simplest way possible, as MoominPapa explained. In forward there's bugger all going on in that gearbox. They used an epicyclic cluster to achieve this. The compromise (could be, as I haven't thought it through) is that reverse comes out at a different ratio. You could probably get reverse to be 1:1 with a more complex epicyclic set up, but why bother - it's only reverse - and this is supposed to be a simple gearbox.

 

Richard

 

No-one set out to design a box with different ratios forward and reverse. They set out to design a simple gearbox that fails safe into forward.

[alan_fincher]

I must be missing something, I think.

 

I'd say with the simplest possible arrangement, as described by MP, the ratio in reverse is 1:1 - exactly the same as in forwards.

 

I think you would have to go more complex, rather than less to achieve a different result.

 

But perhaps not ??

[RLWP]

I must be missing something, I think.

 

I'd say with the simplest possible arrangement, as described by MP, the ratio in reverse is 1:1 - exactly the same as in forwards.

 

I think you would have to go more complex, rather than less to achieve a different result.

 

But perhaps not ??

 

Waaaay back in post 8 I said

 

Out of curiosity and no more, because of the epicyclics, does the box have a different drive ratio in forward and reverse then?

 

Richard

 

I said this because I know that by driving and locking different parts of an epicyclic box - the sun, planet and ring gears - you get different directions of rotation and different gear ratios. Mr Fincher, have you done the tooth count and logical thinking to determine that the ratio in reverse is 1:1, because if so, I'd like to see your working out please.

 

Richard

 

Perhaps I'll have to work it out myself

[alan_fincher]

Jack up the back of your Midget, in gear, with the engine stopped, and hand-brake off.

 

Wind one wheel one full turn in one direction, whilst someone observes the other.

 

I'd be surprised if it does not go round exactly once, (although with BMC engineering, it might not be totally exactly, as there will be a bit of slop in there!).

 

The gears at each end of your half size have the came number of teeth. So do the ones that are driving from one of these to the other, (as each other), but it does not matter if these have a different number from the ones on the half shafts, as they are only acting as idlers between the two "half shaft" ones.

 

As I'm not an engineer, you are starting to make me nervous that I'm making an idiot of myself.

 

I might need to go and get some Lego Technic out, to give myself a warm feel that I'm not!

 

(I've not done any tooth counting thus far).