Lister LH150 Reversing Box

[MoominPapa]

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 ??

 

I don't think it's possible to have 1:1: you have a sun gear in the middle, a ring gear round the outside, and the planet gears in the gap between the two. The reverse ratio is determined by the ratio of the number of teeth on the sun gear to the number of teeth on the ring gear: the external circumference of the sun gear has to be smaller than the internal circumference of the ring gear, to leave a gap for the planet gears. The pitch of the teeth has to be the same on both so they can both mesh with the planet gears, therefore there must be more teeth on the ring gear and the gearbox must act as a reducing box in reverse.

 

I think?

 

 

MP.

[RLWP]

Here, knock yourself out: Epicyclic gears

 

And you shouldn't be jacking cars up in your condition (yes, you're right about the differential, because the bevel gears on the end of each half shaft have the same number of teeth). But a differential isn't an epicyclic gear cluster.

 

Richard

 

I think I'll adjust the brakes while it's jacked up though

[RLWP]

I don't think it's possible to have 1:1: you have a sun gear in the middle, a ring gear round the outside, and the planet gears in the gap between the two. The reverse ratio is determined by the ratio of the number of teeth on the sun gear to the number of teeth on the ring gear: the external circumference of the sun gear has to be smaller than the internal circumference of the ring gear, to leave a gap for the planet gears. The pitch of the teeth has to be the same on both so they can both mesh with the planet gears, therefore there must be more teeth on the ring gear and the gearbox must act as a reducing box in reverse.

 

I think?

 

 

MP.

 

To be honest, I haven't got my head around this gearbox. I can see the sun gear on the input shaft. I can see a planet gear on a carrier with a band brake. I don't think there is a ring gear (there doesn't have to be). Is the "plain disk" on the output shaft beside the spigot the aligns the input and output shafts another sun gear? is there an idler gear in the planet clusters?

 

Need an exploded diagram really

 

Richard

[alan_fincher]

I don't think it's possible to have 1:1: you have a sun gear in the middle, a ring gear round the outside, and the planet gears in the gap between the two. The reverse ratio is determined by the ratio of the number of teeth on the sun gear to the number of teeth on the ring gear: the external circumference of the sun gear has to be smaller than the internal circumference of the ring gear, to leave a gap for the planet gears. The pitch of the teeth has to be the same on both so they can both mesh with the planet gears, therefore there must be more teeth on the ring gear and the gearbox must act as a reducing box in reverse.

 

I think?

 

 

MP.

 

I think I'm probably having a bad day.....

 

In fairness I did say initially I was talking about a different make and model gearbox, and, indeed, when I pull out my old "Parsons Type F" manual, it confirms that box does contain a "bevel gear chain within a bevel gear case", just like a car differential in layout of the gears, and it explicitly says it "rotates the propeller in astern at the same speed as in ahead".

 

So I did understand that correctly.

 

However if the Lister LH 150 box is not of this design, but is a genuinely epicyclic box, (is it, for certain ?), then I completely concede that MP is correct, and you could probably achieve nothing like a 1:1 ratio on reduction. In fact I'd have thought such an arrangement would have been a bit worse than an "engineering compromise", but perhaps not.

 

I guess then I don't understand why you would go the epicyclic route, when the one I have described for the Parsons is a simpler piece of engineering, gives a 1:1 reduction, and still meets the requirement that none of the gearing is used in a forward drive.

 

Anyweay, sorry to have confused!

[paulcatchpole]

I think I'll adjust the brakes while it's jacked up though

 

I leave you lot alone for five minutes and what do I come back to?

 

I'm not sure if I'm less confused now, or more!

 

What's the thinking on my box anyway, jammed or fallen apart? And do I just poke it hard enough to find out? Crowbar?

 

PC

 

Edited to add, whilst looking for understanding about epicyclic gear trains, I never knew that pencil sharpeners used them...

 

http://en.wikipedia.org/wiki/File:Pencil_s...r_mechanism.jpg

Edited May 4, 2010 by paulcatchpole

[alan_fincher]

What's the thinking on my box anyway, jammed or fallen apart?

No idea, and no help at all I'm afraid.

 

I just like arguing, even when I seem to have made false assumptions about the internal design of what I'm discussing!

[RLWP]

I leave you lot alone for five minutes and what do I come back to?

 

I'm not sure if I'm less confused now, or more!

 

What's the thinking on my box anyway, jammed or fallen apart? And do I just poke it hard enough to find out? Crowbar?

 

PC

 

I think you've got a very useful, heavy mudweight

 

Richard

 

Seriously, I thought I could see evidence of rust on some of your pictures, like the red stuff on the other bits in this one:

 

 

I wouldn't be surprised if your cone clutch hadn't rusted up, like brakes do if you leave a car standing for a long time with the handbrake on?

 

There's one of those elusive reverse gear planet wheels at the bask of that picture

 

 

No idea, and no help at all I'm afraid.

 

I just like arguing, even when I seem to have made false assumptions about the internal design of what I'm discussing!

 

Hey, don't beat yourself up! Asking questions is a great way to learn about things. With your new found knowledge, go look at how a Borg Warner automatic gearbox works. Fascinating stuff!

 

Richard

[paulcatchpole]

No idea, and no help at all I'm afraid.

 

I just like arguing, even when I seem to have made false assumptions about the internal design of what I'm discussing!

 

Nah, good discussion is always useful and entertaining!

 

PC

[MoominPapa]

 

To be honest, I haven't got my head around this gearbox. I can see the sun gear on the input shaft. I can see a planet gear on a carrier with a band brake. I don't think there is a ring gear (there doesn't have to be). Is the "plain disk" on the output shaft beside the spigot the aligns the input and output shafts another sun gear? is there an idler gear in the planet clusters?

 

Need an exploded diagram really

 

Richard

 

Well that diagram clearly doesn't correspond with my description, because the forward clutch locks the output shaft and the spider together. If the sun gears are meshed with the gear on the output shaft, that locks them too, relative to the output shaft, and the whole thing is driven round as a unit, OK. But how does reverse work? There must be something meshing with the outside of the planet gears, surely?

 

As an aside, I see that Lister kept the use of the engine main bearing to support one end of the gearbox on this design, but added oil seals so that the box has its own oil. The earlier boxes run in the engine's oil.

 

MP.

 

Edited 'cause I mixed up my suns and planets.

Edited May 4, 2010 by MoominPapa

[paulcatchpole]

I think you've got a very useful, heavy mudweight

 

Richard

 

Seriously, I thought I could see evidence of rust on some of your pictures, like the red stuff on the other bits in this one:

 

I wouldn't be surprised if your cone clutch hadn't rusted up, like brakes do if you leave a car standing for a long time with the handbrake on?

 

There's one of those elusive reverse gear planet wheels at the bask of that picture

 

Richard

 

I'm fairly sure the red stuff is actually an internal paint finish, and the gungy black stuff isn't supposed to be there - I didn't take any pics post diesel, but it's a bit more red and clean now...

 

So I've a box that'll go forwards, and on top of that, if we want to stop, I can remove it quickly, attach a rope and throw it overboard... I like it...

 

I thought the planet geary-thingies were inside the ring? Why is that one on its own?

 

Also, why is the assembly splined, like in the diagram, and presumably where some of my float comes from?

 

And, and, how many spots does a leopard have?

 

PC

[RLWP]

Well that diagram clearly doesn't correspond with my description, because the forward clutch locks the output shaft and the spider together. If the sun gears are meshed with the gear on the output shaft, that locks them too, relative to the output shaft, and the whole thing is driven round as a unit, OK. But how does reverse work? There must be something meshing with the outside of the planet gears, surely?

 

As an aside, I see that Lister kept the use of the engine main bearing to support one end of the gearbox on this design, but added oil seals so that the box has its own oil. The earlier boxes run in the engine's oil.

 

MP.

 

Edited 'cause I mixed up my suns and planets.

 

I think (WARNING) that there's a sun gear on the input shaft, a sun gear on the output shaft, a planet that engages with the input sun gear, a planet that engages with the output sun gear, and the two planets mesh with each other reversing the box.

 

The input planet gear is shown above the input shaft, the output planet gear is shown below the input shaft. Annoyingly, this gives a ratio of 1:1

 

Paul, there's no ring gear in this installation. You don't have to have all three, like your pencil sharpener where the ring is present and fixed, the handle turns the carrier, the planet gears attach to the blades and there's no sun* gear

 

Richard

 

*Must be dark inside a pencil sharpener then

[paulcatchpole]

I think (WARNING) that there's a sun gear on the input shaft, a sun gear on the output shaft, a planet that engages with the input sun gear, a planet that engages with the output sun gear, and the two planets mesh with each other reversing the box.

 

The input planet gear is shown above the input shaft, the output planet gear is shown below the input shaft. Annoyingly, this gives a ratio of 1:1

 

Paul, there's no ring gear in this installation. You don't have to have all three, like your pencil sharpener where the ring is present and fixed, the handle turns the carrier, the planet gears attach to the blades and there's no sun* gear

 

Richard

 

Right, I think I've got that, just about.

 

What're the splines for then?

 

And am I still right that I need to try applying more freeing-fluid and a little force?

 

PC

 

*Must be dark inside a pencil sharpener then

 

Hmm, I was considering a location to put the gearbox if it turns out to be broken, and was looking for somewhere with those ambient conditions - now I know and can indeed use a pencil sharpener.

 

[RLWP]

Right, I think I've got that, just about.

 

What're the splines for then?

 

And am I still right that I need to try applying more freeing-fluid and a little force?

 

PC

 

Splines are for the sliding and the driving. Don't worry about them

 

Dunno about the freeing off. If it were a car I'd run it at idle 'til it was nice and hot, point the car down a long empty driveway then start it in gear with my foot on the clutch. If that didn't work I'd hold the clutch down, put my toe down on the accelerator then jam my heel down on the brake...

 

How do you do that with a boat??? You need a different expert

 

Richard

[WotEver]

How do you do that with a boat??? You need a different expert

Wouldn't repeatedly putting it into reverse with the engine running be the best way to free it (if it's going to free up by itself)?

 

Tony

[RLWP]

Wouldn't repeatedly putting it into reverse with the engine running be the best way to free it (if it's going to free up by itself)?

 

Tony

 

Ah yes. But every time Paul puts the box in reverse, because the engine is at idle, he has both clutches engaged and the box locks, stopping the engine.

 

Might work if he had the prop on, but now we're into a different set of probems...

 

Richard

[WotEver]

Ah yes. But every time Paul puts the box in reverse, because the engine is at idle, he has both clutches engaged and the box locks, stopping the engine.

Yeah, I know... but that was my point

 

Both clutches are engaged because the fwd clutch is stuck. He wants to un-stick the fwd clutch. So wouldn't repeated stallings (have I made a word up?) be sufficient to free it if it's going to free up?

 

Tony

[RLWP]

Yeah, I know... but that was my point

 

Both clutches are engaged because the fwd clutch is stuck. He wants to un-stick the fwd clutch. So wouldn't repeated stallings (have I made a word up?) be sufficient to free it if it's going to free up?

 

Tony

 

Could do I guess. I'd like to see some more momentum in the system.

 

I'm wondering about filling the box up with very hot oil. I've shifted a stuck piston that way once

 

Richard

 

You could keep horseses in your stallings

[WotEver]

You could keep horseses in your stallings

but you'd have to get them out when the jockeyses come...

[paulcatchpole]

Could do I guess. I'd like to see some more momentum in the system.

 

I'm wondering about filling the box up with very hot oil. I've shifted a stuck piston that way once

 

Richard

 

You could keep horseses in your stallings

 

Is that why you'd prefer the prop on, Richard - to get some momentum on it? I guess I could bring the ennin up to rather more than idle, to provide some energy at least? Are we not concerned about the amount of slip that might happen and the resulting wear, for each attempt? Or doesn't it matter cause it's knckered anyway?

 

Hot oil? Really? I was considering leaving it to soak in more diesel - part of the problem being that the box isn't diesel tight to that depth/height - it leaks out!

 

Boiling oil, man the battlements. Do I need a castellated nut?

 

 

but you'd have to get them out when the jockeyses come...

 

Jockeys? Jockey wheels? Idler wheels? Jockeys are idle? eh? I know a wheely good joke?

 

Sorry, at work at the moment, and generally gone a bit craaaazy.

 

PC

[RLWP]

Is that why you'd prefer the prop on, Richard - to get some momentum on it? I guess I could bring the ennin up to rather more than idle, to provide some energy at least? Are we not concerned about the amount of slip that might happen and the resulting wear, for each attempt? Or doesn't it matter cause it's knckered anyway?

 

Hot oil? Really? I was considering leaving it to soak in more diesel - part of the problem being that the box isn't diesel tight to that depth/height - it leaks out!

 

<snip>

PC

 

The prop is for momentum, but there would be a major advantage in keeping the oil in too....

 

Richard

 

I'm winging it here. You need a different expert on freeing up LH150 boxes. If it were mine I'd give it a go with some power on, if that didn't work it'd be in the garage in bits by now

[paulcatchpole]

The prop is for momentum, but there would be a major advantage in keeping the oil in too....

 

Richard

 

The oil will stay in at the right level, but to immerse the cones completely, it needs a lot more than 1.2L, and is high enough to run out of the top output oil seal...

 

Bit short of momentum on that end I'm afraid, but with the engine wound up, there should be a bit of moving flywheel mass at least...

 

I'm winging it here. You need a different expert on freeing up LH150 boxes. If it were mine I'd give it a go with some power on, if that didn't work it'd be in the garage in bits by now

 

Don't worry, so am I, but you're a clever chap with all things mechanical, so I value your thoughts!

 

I'll give it a poke, then a flush with more diesel, then some fresh oil again and give it a few goes with a bit more go from the ennin. If that doesn't work, then it's coming off. I've got the instructions for taking it apart now, after I found them in the ST2 manual, although it sounds a bit more than undo-bolts, hit with hammer if still doesn't come apart...

 

PC

[Guest User]

... Just to double check, have you yet tried disengaging the clutch as mentioned by Dave Mayall in post #98 of the "Stern Tube/Gearbox/Starter Confusion Part 3" thread ? ... "With the lid off, the box should be locked in gear. On the rear left of the box, there is a plate secured with 3 bolts and a 1/2" central bolt. Remove the central bolt, and insert one of the longer bolts from the lid. tighten the bolt, so that it operates the actuator arm, and the clutch should disengage, allowing free rotation of the output shaft." ... or as the Manual has it on dear old page 45 ... Remove screw "A" and replace it with screw "B", screw it in until the clutch just disengages and no more (the screws must be returned to their original holes before running !!!)

[WotEver]

Yeah, he tried that - still stuck in fwd.

 

T

[paulcatchpole]

Yeah, he tried that - still stuck in fwd.

 

T

 

Aye, Tony's right, I tried it, and the shaft went from being very 'solid' in FWD, to being able to rattle it left and right and in and out a bit, as in the youtube vid earlier on, but it wasn't in neutral and didn't turn freely.

 

I've been wondering if the above symptom was meaninful, but noone's picked up on it, so I guess not...

 

PC

[RLWP]

Aye, Tony's right, I tried it, and the shaft went from being very 'solid' in FWD, to being able to rattle it left and right and in and out a bit, as in the youtube vid earlier on, but it wasn't in neutral and didn't turn freely.

 

I've been wondering if the above symptom was meaninful, but noone's picked up on it, so I guess not...

 

PC

 

It means it's still in forward, 'cos the clutch is stuck, innit

 

Richard

 

Hopefully that rattle left and right doesn't mean your driveplate is knackered...