Bmc Commander Oil Leak

[seasurveys]

Hi There

 

A quick question that some may know the answer to :

 

BMC 2.2 Commander with Newage/Parsons Non hydraulic gear box , an oil leak has recently developed between the gear box and engine and as the oil is clean , it is most likely the gear box first motion shaft leak . My question is, because I have no drawings or breakdown of the components , has anyone have experience of separating the engine from the gear box and if so, does the gear box come off the bell housing leaving the bell housing attached to the engine or does the bell housing come off complete with the gearbox attached .

It may be possible for me to remove the gear box without removing the engine but it would be useful to have some idea as to what to expect . Does anyone know where I can obtain a simple drawing or breakdown of the unit and the way the drive is transmitted to the gear box . Standard FNR gear box with 2:1 Reduction gear.

 

Thanks in anticipation

 

John Lilley

[RLWP]

Most of the Parsons boxes should unbolt from the engine and come away nicely. I did something on a Parsons DA here: http://www.canalworld.net/forums/index.php?showtopic=48361

 

That one has a separate shaft to the engine, so has a drive flange on the input side:

 

 

Yours more likely has a splined shaft that slides into the driveplate

 

Richard

[seasurveys]

Hi There Richard.

Thanks for that, the gearbox on my engine is a Newage but I believe Parsons design & is slightly different in that the circular flange is there & this bolts to the engine bell housing. If you split at the flange I think that is the front plate of the g/box & releases all the oil but unsure if you can access the fwd. oil seal without removing the bell housing & also uncertain if the shaft can pull out of the flywheel with the bell housing still bolted to the engine. Just trying to forestall any problems that might occur by splitting at the wrong point, especially when access is slightly difficult to do the job twice.

 

 

 

Photo in following post of identical engine but mine still in boat. . . Note the bell housing.

 

Thanks

 

 

Johnj

Edited August 5, 2013 by seasurveys

[RLWP]

 

I would undo the bolts that hold the flywheel housing to the engine, not the ones that hold the gearbox to the flywheel housing. The flywheel housing can't be holding any oil in, the other bolts might

 

Richard

 

 

[seasurveys]

Thanks Richard

 

I think you are correct, I am sure undoing the aft set of flange bolts releases the oil from the gearbox, but was not certain if there was anything that had to be undone or released to allow the input shaft to uncouple from the flywheel & if so where that was located if the bell housing is removed first

 

Oil leak causing starter gear assy. to play up as the inertia clutch plates on the starter pinion fail to immediately lock and turn engine over. The plates get oil on & slip before fully locking together.

Difficulty in not knowing the internal set up.before removal. Do you know of any exploded view of this gearbox? Cannot find any diagrammatic info at this time.

 

 

Regards

 

 

John

[RLWP]

I don't have or know of a diagram of this box. However, I'd be surprised if there was anything locking the input shaft into the driveplate. After all, why would there be? It would make the thing damn difficult to put together, they're hard enough as it is!

 

I don't recognise your description of how your starter motor works, all the ones I have come across are either inertial with a spiral on the motor shaft, or pre-engaged with a solenoid. No matter how it works, chucking oil into it isn't going to help

 

 

Richard

Edited August 5, 2013 by RLWP

[seasurveys]

Thanks Richard

 

the starter is quite complicated, a set of steel/brass discs on a quickthread lock together & spin containing assembly on inertia start & turn pinion, when flywheel overruns plates release and when solenoid released all returns to rest. Very different to typical starter bendix.

 

Thanks again.

What I might do to keep the weight down is to remove the reduction box from the rear of g/box to allow a bit more aft movement & less weight. I assume this just pulls out of splines at the out put flange after releasing the circle of flange bolts. I assume this comes of as a complete unit.

 

 

John

[RLWP]

That looks likely

 

Do take some pictures to show us, won't you

 

Richar

[seasurveys]

Will Do................

 

John

[Tony Brooks]

Thats a B type gearbox and there is (from 45 year old memory) an intermediate plate between the gearbox flange and the bell housing.

 

I think the input shaft will be bolted direct to the flywheel and I also think it is machined to from the sun gear teeth for reverse gear. I seem to remember a cam on it that operated a small piston type oil pump for lubricating the planet gears.

 

Tip- the reverse gear drum has about 6 or so long bolts going right through it holding the assembly together. In my experience these occasionally fail and if they are in with the nuts towards the stern then the broken bolt can work out and jamb against that oil pump I was talking about. If they are inserted the other way round they may still jamb the box but the odd one can be carefully extracted via the inspection cover and the box will still work.

 

The starter sounds like what I consider a normal 2.2 pre-engage starter. They used a multi-plate clutch to prevent the engine over-speeding the armature when it fired, rather than the sprag clutch (free wheel) more normal today. I found that often a strip down and wash out (Single large internal circlip) and re-shim as required would solve such problems.

 

From memory I think we took the box away from the intermediate plate and dropped any oil we could not drain into the engine tray. I have a feeling you may have to undo a nut to pull the cam off the input shaft before removing the intermediate plate. Sometimes you can get away with the old gasket - maybe silicon would be OK today.

 

Richard, where on the photo are the rear mounting feet that normally fix between the gearbox and reduction box? I would hate to hang that great cast iron lump from the rear engine feet!

Edited August 5, 2013 by Tony Brooks

[RLWP]

 

Richard, where on the photo are the rear mounting feet that normally fix between the gearbox and reduction box? I would hate to hang that great cast iron lump from the rear engine feet!

 

No idea Tony, that's how it came and went.

 

I understand there is a Cardan shaft between the engine and gearbox in that particular installation

 

And, it's a DA, so it's an aluminium lump

 

Richard

[Tony Brooks]

Maybe, if it is a Parsons design the Parsons version was ally. I think the intermediate plate was but I am sure the case was cast iron.

 

I am talking about your second picture with the box on the engine, not the first one. I am certain the second photo shows a BMC B Type box, We had several of the horrid things on the hire fleet. They did not get on well with hire customers so we gradually changed them to PRMs.

[RLWP]

Oh right. That's the Ebay engine that the OP - seasurveys - used as a reference. I nicked the picture off Ebay to illustrate the thread

 

So, Seasurvey's gearbox is probably OK, the Parson's DA I also linked to is fine as well, but the Ebay one is a bit short of brackets

 

Richard

[seasurveys]

So is the consensus that the gearbox is a B type & primarily it has to be removed from the bell housing or does the team think it should be removed with the bell housing attached. The bell housing has the aft mountings attached to this. A slight problem exists in that the gearbox flange bolt heads (bolting to the bell housing) do not have enough clearance from the casting recess to get a socket on, presumably the original bolts had extra long projecting heads to enable a socket to attach, Are these nuts & bolts or just bolts does anyone know. I cannot imagine they are nuts & bolts because how could you access the nuts if the bell housing is attached to the engine. Can't afford to have the problem of nuts dropping where they shouldn't if I take the flange off instead of the bell housing but don;t want the problem of a loose gearbox that will not come off if it is still connected to the flywheel as at the time it will still be in the boat with limited manoeuvrability

 

Still slightly uncertain about how the drive connects & therefore how is disconnects from the flywheel though. There is no inspection plate other than the access plate for adjusting the fingers. The gear selection lever splines are at the base aft.

 

 

The starter is as Tony suggests, I have stripped it a few times to separate & wash the plates,I drilled a drainage hole in the underside of the nose cone to prevent oil collecting there & running back inside the pinion clutch assy. That has stopped the problem but the oil leak has to be sorted, still not absolutely sure it is the oil seal but not much else it could be really.

 

Unaware of the oil pump until now , just assumed there was an oil flinger onto the gears.

 

Thanks for the advice

 

 

John

[Tony Brooks]

Again, I stress this is from a 45 year old memory.

 

The drive is a "stub" shaft bolted to the flywheel, possibly using the flywheel securing bots or longer studs and nuts. I think it has the gear teeth to mesh with the reverse planet gears machined on it and also a cam or eccentric to drive a small piston oil pump. The cam and gear teeth are inside the box and have to pass through the oil seal in the intermediate plate. Now the hazy bit. I can nor remember if the cam and gear teeth will pass through the oil seal or if they can be removed from the stub shaft after the gearbox has been remove. If they will pass through the oil seal you will need to take great care when sliding the intermediate plate over the shaft. This is one reason I would handle the main parts of the box and the intermediate plate as separate items.

 

I think that you are right about the special long head securing bolts but I seem to remember a ground down socket and ring spanner. I think that they are 1/2" AF and suspect that a modern 1/4" square drive socket from a reputable maker may go on. I know my ParX 9/16 AF 1/4sd socket has been exceptionally useful for such tasks.

 

The flywheel housing should be threaded so no nuts inside to drop down.

 

Do not try to lift the box off on your own, especially if it has a reduction box on the end. They are seriously heavy.

 

The box should just slide off the stub shaft but make sure intermediate plate splits away from the box. Then you will be able to see if the plate will just pull over the stub shaft. It a bit like the Lister LH150. From memory replacing is much harder in that you need to get the gear teeth in line and the pump plunger onto the cam.

[RLWP]

I bow to Tony's experience. He's worked on a box of this type, my advice is what I would do faced with an unknown box

 

I have one of the smaller BMC boxes here somewhere

 

Richard

Edited August 6, 2013 by RLWP

[seasurveys]

Thanks Tony

I'll probably remove the reduction gear separately to minimize weight & awkwardness & from what I understand you are saying,, remove the gearbox from the bell housing without interfering with the bell housing & hope the drive separates easily on a spline or similar. Once the gearbox is clear then normal disassembly as required to access the oil seal. It is the intermediate plate that is the unknown quantity at the moment & how that prevents or restricts removal.

 

I'll try to find some exploded view somewhere but no luck at the moment.

 

 

Thanks again.

 

John

[Tony Brooks]

That is not what I am saying.

 

Clean the paint off from around the joint where the box bolts onto the flywheel housing and I think that you will find there is a plate sandwiched between the gearbox flange and the flywheel housing. It is held in place by the bolts through the gearbox flange.

 

I seem to remember that you can leave this plate on the input shaft and pull the gearbox away. The input shaft will slide out of the reverse gear drum. In this way you will be able to see if the plate will simply pull off the input shaft (still attached to the flywheel, or if you have further stripping to do. As I said I can not remember if the oil seal in the intermediate plate will allow you to pull the intermediate plate off the input shaft. If you leave it in place then you will be able to see. In any case you will not want to push the new oil seal over the shaft whilst holding the weight of the box. If you try there is every chance that you will damage the oil seal on the reverse sun gear teeth that are formed on the input shaft.

 

Pull the box and most innards away from the engine but leave the intermediate plate hanging on the input shaft that will still be attached to the flywheel.

 

From memory you will have to split and strip the reduction box to get it off the gearbox output shaft unless there is a cover on the back that will allow you access to the nut on the gearbox output shaft that secures one reduction gear to the gearbox shaft. Personally I would leave it on and get help. An A frame and pulley may allow you to support the box and take it out by yourself. Maybe some long lengths of studding screwed into the flywheel housing in place of the bolts would allow you to slide the box backwards.

 

The gearbox input shaft - that is bolted to the flywheel LH150 style - also carries a bearing that supports the front of the reverse gear drum. Again you really need to see all this and the only way you will do that is if you leave the intermediate plate on the engine.

 

No splines as such. Spur sun gear teeth, a bearing and a cam/eccentric. You pull the gearbox off the input shaft.

Edited August 6, 2013 by Tony Brooks

[RLWP]

Tony, would a photo of the front of the smaller BMC, and of an LH150 drive shaft help?

 

Richard

[Tony Brooks]

That's for the OP to say Richard, I thought that I had made the design and removal procedure clear enough. In any case your first photo of the Parsons box cleverly shows that the input shaft bolts to the flywheel. The B Type is similar.

 

Regrettably I never got hold of an A type box because all the petrol cruisers our customers had used Watamotor/Wortham Blake boxes on Ford engines. I have no idea how the drive for the A & B type compare but input shafts bolted to the flywheel seemed common at that time.

 

Because it was so long ago I simply can not promise that what I say is 100% correct but I think it is. I am 100% sure that he can pull the box off the shaft and leave the intermediate plate hanging on the shaft while he looks at it to see if it will just pull off.

[RLWP]

Lets do it anyway

 

Hang on

 

Richard

 

MORE: Right, this is a smaller BMC gearbox, no flywheel housing or seal plate:

 

 

The end view into the gearbox. The input shaft passes into the centre of the reverse cluster. Looks like there should be a bronze bush:

 

 

There is no oil pump in this gearbox

 

Finally, this is the input shaft from an LH150:

 

 

It bolts onto the flywheel. The gearbox can be removed leaving this on the flywheel. Tony is saying to remove the gearbox at the same flange as this gearbox, leaving the seal plate behind. Makes sense to me, backed up by the fact that is how this gearbox has been dismantled

 

Richard

Edited August 6, 2013 by RLWP

[seasurveys]

Thanks so much to both of you for the mine of information you have shared with me. I am very grateful. There are distinct similarities between the BMC Commander gearbox that I have and the photograph above in, that the gear selector splined shaft is in the identical position as is the brake band adjustment. It may be that my gearbox is slightly longer but it is difficult to tell from the photographs.

I will look for the plate as Tony suggests, I can see now why it would not be possible to remove the gear box still attached to the bell housing. Presumably the oil seal is fitted in the sandwiched face plate running on the plain section of shaft directly forward of the spur gear aft of the flywheel bolts.

In this case, I can see that it is obvious as soon as the bolts have been released from the gear box the oil will be lost so it needs to be drained out prior to stripping.

All that I have to sort out now is to figure some way of removing one or two of the flange bolts as, it does appear that some stage in the past they have been replaced with standard head bolts instead of the extended head bolts. I am sure this can be overcome with some ground sockets as previously suggested.

Tony's suggestion about installing long dowels to be able to to remove the gear box and keep it supported is a good idea. In this particular case the engine support rear is on the bell housing and it does not incorporate an engine bearer plate as shows in Richard's photograph.

When I go down next then I will confirm the way it has been suggested that it is designed. Just never noticed that there was an additional plate between the gearbox flange & bell housing.

If I have any further questions over the external design that have not been answered would you mind me just putting them to you?

Once the gearbox is off then I will be able to sort it without too much difficulty, it is just not knowing the transmission method to the gearbox which has now been comprehensively explained. I have spoken to some experienced marine engineers who claimed to have had experience of these units who absolutely assured me that the bell housing can be removed bringing the gearbox with it. I just had doubts over what they were saying. Thanks again.

John www.seasurveys.co.uk

Edited August 6, 2013 by seasurveys

[RLWP]

We like questions John

 

Letting the oil out will make it lighter too

 

Richard

[Tony Brooks]

Richard's photo is of the smaller?? A type box, not the B Type.

 

All the B Types I have come across use the engine oil drain pump to also drain the gearbox but a little oil remains.

 

The reverse brake band is supported by a post from underneath and I think it is adjustable. On no account mistake this for the oil drain. Actually as you are taking the box off and will be able to look inside you could reset it, but lets not make extra work. I think the oil drain is sideways into the bottom of the box towards the thick end.

 

The mechanical workings are similar to a number of marine boxes of this age, be it a bit cruder in some cases. A big drum counting twin planet gears to give reverse when the drum is locked plus a multiplate clutch, operated by toggles to lock the output shaft to the drum for 1:1 ahead. Any reduction is done separately in a box bolted to the back.

 

As the flywheel housing usually carries the rear engine feet there is no way I would want to take that off as well as the box. Its heavy enough already and I would not want the engine raised on bricks etc. when trying to push the box back into place, although you may have to so the half coupling will clear the prop-shaft.

Edited August 6, 2013 by Tony Brooks

[seasurveys]

The unit is fitted with a brass cylinder pump with change over valve for engine or gearbox drain & I have noted the adjuster on the base of the g/box. I will keep my fingers crossed that the box can be moved far enough aft to clear out without having to remove the rudder. The engine is fitted in a timber built Hillyard sailing vessel as can be seen on my website www.seasurveys.co.uk.
The main difference I can see between my g/box & the smaller Captain gearbox is the circumference bolts on the flange are pocketed slightly causing the need for thin walled socket.

 

Many thanks for your experienced help.

 

Regards

 

 

John

Edited August 6, 2013 by seasurveys