Bmc Commander Oil Leak

[bmcrich]

Hi Richard (RLWP). can you please tell me what is the gearbox in the top picture? I am trying to fix my friends gearbox. It is exactly the same as the grey one in your post ('the smaller bmc' as you describe it).

 

When I got to it this morning it was stuck in forward whether the lever was in reverse, neutral or forward the prop just kept spinning in forwards.

 

adjusting the brake band by the 2 square 'bolts' either side of the gearbox I eventually managed to get reverse and neutral but then I couldn't get it to go in forward gear at all.

 

there are 3 'toggles' approx. M6 (or imperial eq.) bolts with locknuts (which have been thoroughly rounded off- probably by ill fitting spanners) which look like they control the forward gear , I am guessing these need adjusting somehow as well as the band being adjusted correctly.

 

does anybody know the correct sequence to set these gearboxes up?

 

it is on an AVA2 which also needs attention.

 

thanks in advance

 

Rich

Edited September 7, 2013 by bmcrich

[Tony Brooks]

Something seems a bit wrong here unless the jammed in gear was oil drag because if it was jammed in ahead it would lock up when you got reverse.

 

I seem to remember having to adjust the three toggles evenly (checked with a feeler gauge between toggle and sliding cam that the lever moves) and then making sure it engages ahead. After that adjust the astern brake band.

 

I wonder if one of the ahead clutch plates has broken up locking the box in ahead.

A Richard says its the smaller BMC box its a BMC A type.

[RLWP]

Hi Rich, as Tony says it's a BMC 'A' box. I haven't taken it apart as yet, I'll see if I can find some time to have a look at it to help you out

 

Richard

[bmcrich]

great - thanks Richard and Tony - I am doing this 'blind' having never worked on either an AVA2 or this type of gearbox before. I figured the 'toggles' would have to be set somehow. now I just need to find the setting for the feeler gauge. Thanks again. Rich. ps if anyone knows where to get a manual it would be a massive help-or any spare parts/info (e.g. could do with the original shift lever- and some of the workings have been a bit abused) . cheers.

Edited September 8, 2013 by bmcrich

[Tony Brooks]

We used feelers to make sure each toggle was set to the same height and then adjusted each toggle adjuster an equal amount to ensure ahead gear engaged properly as the toggles slid over the ramp on the sliding cam operated by the gear level. Hence the feeler size is immaterial as long as its the same on each toggle.

 

Richard has done if far more recently than I have.

[bmcrich]

that is very helpful Tony thank you. just off (2 hour journey to Kinver) to see the lump now. I fear the toggle bolts will be too rounded to get a decent grip and will be on the hunt for some replacements (possibly whitworth??) before I can restart the job. I will let you know tonight how I got on. thanks again. Rich. ps - in a worst case scenario - Richard - would you consider selling or part ex your gearbox?

[Tony Brooks]

that is very helpful Tony thank you. just off (2 hour journey to Kinver) to see the lump now. I fear the toggle bolts will be too rounded to get a decent grip and will be on the hunt for some replacements (possibly whitworth??) before I can restart the job. I will let you know tonight how I got on. thanks again. Rich. ps - in a worst case scenario - Richard - would you consider selling or part ex your gearbox?

 

I doubt BSW, more likley BSF from what I can remember. BSW would, in my view, be a bit course for the fine adjustment required but who knows.

[RLWP]

that is very helpful Tony thank you. just off (2 hour journey to Kinver) to see the lump now. I fear the toggle bolts will be too rounded to get a decent grip and will be on the hunt for some replacements (possibly whitworth??) before I can restart the job. I will let you know tonight how I got on. thanks again. Rich. ps - in a worst case scenario - Richard - would you consider selling or part ex your gearbox?

 

I've a couple of rush jobs on at the moment, I'll get around to the BMC box tomorrow

 

And yes, it's for sale if you need it

 

Richard

[bmcrich]

Hi. Well after a while adjusting and readjusting the brake band I realised that as Tony suspected 'something was wrong here'- the reason for not engaging into forward was the owner had been turning a rod while I was adjusting and this rod was causing the shift lever to jam up and was not anything to do with the box itself!

 

I have some new bolts allegedly coming today so I will be trying to get the engine to run smoothly in the meantime while I wait for them to arrive.

So regards the toggle bolts- should l start by turning them in until they just contact the pistons equally and then turn them in a flat at a time until something happens ??

[RLWP]

I've just popped the cover off the box I have and finally managed to get a reasonable picture. Apart from the fact that the BMC pushes the cone in and the Parsons pulls it out, they both work the same way. Here's some stuff on the Parsons:http://www.canalworld.net/forums/index.php?showtopic=48361&p=899789

 

The BMC A type:

 

 

When the box is locked in forward gear, the tips of those fingers MUST be up on the large diameter cylinder behind the cone. I would adjust it so that the screws will just lock out the clutch when the fingers are on the big cylinder. On some gearboxes, if you overadjust it, you can break the levers which will be nigh on impossible to replace. So, undo the bolts, put the box in forwards, screw in the bolts with your fingers until the plungers tighten against the clutch plates. Then, yes, a flat at a time and see if you can lock the clutch AND get the box in and out of forward gear

 

RIchard

Edited September 10, 2013 by RLWP

[bmcrich]

thanks for all the advice it is much appreciated.

had to stop due to lack of light but I think I am nearly there.

Part of the confusion (I think) is that the propeller is (possibly) configured the opposite way so I have been bashing my head thinking that I am adjusting the 'wrong' way.

Is it common to have opposite running propeller's? (forgive my ignorance I am a land lubber)

i.e. what I thought was afore sends the boat in reverse and vice versa)

Still practising with the old bolts as the new ones haven't turned up yet.

hopefully daylight will bring more clarity! (and new bolts)

thanks again.

Rich

[RLWP]

You need to be careful here and check out what's what. That gearbox will be OK working properly - the band brake giving reverse and the plate clutches giving forwards. If it's working the other way around, it won't work well for long. It'll be bloody noisy too. This is because it will be driving forwards through the straight cut gear clusters - well, until the bearings break up!

 

Pushing the lever forwards should give forwards.

 

Richard

[bmcrich]

ok noted. thanks.

[bmcrich]

so - is it possible that the propeller operates in the opposite direction or more likely I have set the box up incorrectly? [l e a r n i n g c u r v e . com]

[RLWP]

It depends....

 

On the back of the box are the reduction gears. They are in the lump on the left in this picture:

 

 

Usually there are two of them, so that will reverse the direction of the prop relative to the engine. That is the most common arrangement

 

However, if you have a pair of engines in a boat, you generally have the propellers going in opposite directions (for various fascinating reasons we don't need to deal with now). So it could be that there are three reduction gears and then the prop goes the same way around as the engine

 

So, you probably have two reduction gears and the prop goes the opposite way around to the engine, unless the owner has managed to pick up a three gear reduction box and the prop goes the same way around as the engine

 

Best bet is to put the gearbox in forward, turn the engine over by hand and see which way the prop goes

 

Richard

 

MORE: unless the box has no reduction gears of course, in which case the prop goes the same way as the engine

Edited September 11, 2013 by RLWP

[bmcrich]

ok. it looks exactly the same as your picture except it is green not grey. so it has reduction gears. and I believe when I turned the starting handle the prop was turning the opposite way to the engine so it should be a 2 gear reduction. have finally located some bolts (allegedly!) so will pick them up and get back over there with this new knowledge. thanks.

[RLWP]

Good stuff

 

Richard

[bmcrich]

success!

I took the boat out and it drove in all directions, managed a 3 (well about 8 actually) point turn and even managed by swapping from fore to stern gear while wiggling the rudder to pull myself out after getting grounded in the silt . not bad I thought - for a land lubber .

 

 

for any body else with a similar problem I basically more or less followed the instructions from Richard (RLWP) re parsons gearbox (link a few posts before this one) and a couple of other instructions from Richard, Tony (also on this thread) and Paul from Wheaton- so all credit to those guys for their advice without which I would probably still be banging my head.

 

it is a BMC A type gearbox on an AVA2 Petter engine

 

this is what I did (missing out all the incorrect or guesswork stages!)

 

First read Richards link about the Parsons gearbox to understand how the box works then:

 

1: remove cover, turn engine a third of a turn at a time to show each toggle

2: loosen all 3 toggles

3: put box in forward gear ensuring the toggle 'fingers' ride the larger diameter of the cone

4: tighten up toggles until they just contact the pistons on the clutch

5: turn each toggle a flat at a time until clutch just locks (on this box I turned them in 2 and a half flats which is 5/12's of a complete turn so just over a quarter turn) then lock the lock nuts

6: put box in neutral

7: looking from the rear of the gearbox loosen the brass locknut on the right and left hand square bolt and wind each one out (square bolts are 15mm) so that the brake band is definitely free of the drum

 

turning the handle/engine slowly

8: wind in the right hand square bolt until the brake band just locks the drum

9: wind it back out until the drum is free again

10: put box in reverse

11: (still turning engine slowly) wind in the left hand square bolt until the brake band just locks the drum - at which point the prop should start turning the opposite way

12: check lever engages in all positions

13: turn starting handle in all gear positions and check rotation of prop

14: tighten brass locknuts and replace cover

15: go for a test drive

16: have a cup of tea

17: care not one bit about the rain

 

thanks and all credit to Richard Tony and Paul for making this fix possible

 

Rich

Edited September 11, 2013 by bmcrich

[RLWP]

Nice work Rich - I bet you've learned loads!

 

Richard

[Tony Brooks]

Ditto, nothing like having a go and sorting it.

 

Only too happy to help - but not if I am to be charged a penny a post

[bmcrich]

I sure have Richard.

aside from the engine work (still not 100% happy that each cylinder is perfectly in balance but it is loads better than it was)

 

I probably spent 2 days (16 hours or so) messing with the gearbox which I could have done in maybe 2-3 hours tops or even much less had I known what I was doing beforehand. (don't mention dropping one of the old bolts in the gearbox and having to fish it out before I could start again

"oh dear" says I - "I am going to have to take your gearbox off and turn it upside down !" oops I don't know anything about propeller attachments

 

- easily retrieved by purchasing a flexible magnetic pick up tool for £3.99 and just keep wiggling until it comes out!

phew!

 

apart from silly hold ups like that (and 'helpful' people turning things without you knowing) it is a pretty simple job once you have got your head around how the box works

 

the owners should now be able to tow their old 1929 wooden boat to its dry dock in Worcester for renovation and this metal one then has to journey from Worcester to London. fingers crossed it will be full steam ahead for them

 

thanks again for all your help and advice and you too Tony

 

Rich

just to add for anyone attempting this

the adjustment on the 2 square bolts for the brake band is VERY fine

even a 1/16 of a turn or less each side can make all the difference

Edited September 11, 2013 by bmcrich

[nick_theboatman]

Yes I have one of those - at least mine is a 1950 Commodore 3.4.

Very similar, same fwd/reverse and reduction boxes.

Looks pretty close to me...

 

All wrong Im afraid... (well maybe not but bit of "trousers off over head" thing).

 

I don't know if this post is too late for you but here we go:

 

First off manual (that I scanned and sent off to them) is here: http://www.motoren.ath.cx/Download.php?filename=/bmc/BMC_Commodore_Operators_Handbook_2nd_edition.pdf

Sorry its not a great scan but better than working blind.

I also sent them the CAV injector pump manual and the Lucas M45G starter manual as well, shoudl be on the site somehwere if you need them.

Looks like you have both of these on your unit.

 

The problem: the fwd/reverse box is a marine unit, th eblock and bell are truck units. There is a conversion plate that

interfaces the back of the bell to the box. This plate is also the boundary of the box oil. Attached to the inside (box side) of the plate is the box circulation oil pump. The output of this pump runs up a way cast into the plate and into a cavity around the primary drive shaft (which is bolted onto the flywheel). The shaft has a row of radial holes in it and is hollow from this point aft-wards. Further down this shaft there are further radial holes that let the oil back out to lubricate the sun gear bearing in the box. (Clever stuff, orbital box in a 1950 engine). So the oil is circulated from the botom of the box, through the pump, up teh way, iinto the cavity, into the centre of the primary drive, down its length aft-wards and out into teh bearing. The point being that the only thing that stops teh oil spewing out o fthe _front_ of the box through the hole that the primary drive passes through, into the bell, is an oil seal. So if that seal goes three things happen. First the pressure pushes oil forwards past the seal rather than down the centre of the shaft. Second, as teh bell has a drain hole, all the oil falls out the bottom of the bell and into your oversize drip tray (of course) and the oil empties (eventually) from the box. Not good. Thirdly (and this is what is happening to me) the oil splashes around inside the bell and into the drive end of the starter. It then works its way along the starter, past the intermediate plate and along the gap between two field coils where teh retaining bolt or stud lies. It then gets into the brushes. If you are really unlucky and have not taken off the clamp-on rubber seal that goes around the brush access aperures then the motor fils up with oil. Eew. Pretty rapidly the motor will not work. Also dumping 150amps into something filled with hot motor oil doesnt sound good to me either.

 

So now to stripping down. The seal is right at the front of the fwd/reverse box. Becuase of the way the thing is held together it is simply easier to strip the 2 boxes back-to-front. This means taking off the reduction box first then the fwd/reverse box. The instructions are in the manual, but put simply:

1. Take off the back of the reduction box (some puling required)

2. Take out the gears of the reduction box (note some versions apparently used needle bearings rather than balls in cassettes, no cassette so the needles went everywhere if you were not careful)

3. Take off the front of the reduction box

4. Release the shell of the fwd/reverse box, remove it leaving the planetary box housing in place

5. planetary box hosuing now comes off the primary shaft in one piece

6. Interface plate now comes off the back of the bell so you can get at the seal (which will be in the interface plate)

 

Looking closely at your photo it is difficult to see if the interface plate is between the fwd/reverse box or whether the box mounts directly to the bell - but the plate will be there as this supports the primary drive, the front of the planetary assembly and keep sthe oil in, so its there somehow.

 

Finally BMCs had a reputation for always leaking oil. No issue there about reputation...

 

Hope this helps

[seasurveys]

 

Hi All ref oil leak on BMC gearbox

 

After all this time, I have managed to get the gear box off with the exception of the front plate which is still in position on the bell housing. The main difference of between the smaller gear box in the photograph and my own gear box is that there is an oil pump fitted bolted to the front plate. I have removed the oil pump to make access easier. At the moment it looks as if I will need a drawer to remove the front plate and front bearing. The gear driving the epicylcic set has been removed.

At this moment I am uncertain how the oil pump cam collar is fitted and whether this pulls off along with the bearing and plate assembly without any further stripping. Until I see the design I cannot be absolutely certain and I cannot see the design until it is off. There are a couple of drilled and tapped holes close to the bearing which I am assuming are in order to fit a drawer. These holes tapped 5/16 unf.

Do you know of any reason why now that the front nut and locking, had been removed from the presumably bolted flywheel spigot, the assembly cannot be removed.

The front plate cannot be levered off as it will fracture & not sure how tight the bearing & collar are fitted to the flywheel output shaft.

The studs sticking out are If just to confirm they are tapped holes & they are not part of the assembly

 

 

 

 

 

[Tony Brooks]

Sorry, I can not remember anything about the cam etc. The only reason we took the boxes off was so we could renew the long through-bolts in the drum/ahead clutch assemble so we did not need to take the plate off.

 

As you are clearly aware of the dangers of snapping the plate I would try a pry/roll bar behind the cam and against the bearing, but be gentle and take care.

 

I am virtually sure it is not shrunk on so I suspect it is keyed, but why it will now not just pull off I have no idea.

 

Sorry

[RLWP]

 

 

 

At this moment I am uncertain how the oil pump cam collar is fitted and whether this pulls off along with the bearing and plate assembly without any further stripping. Until I see the design I cannot be absolutely certain and I cannot see the design until it is off.

 

Oh, it's endless fun in the gearbox game!

 

The base circle of the cam is really too near the diameter of the shaft for it to be a part that pulls off the end shown - so it must go off the other end. If it does, whatever retains it must be the other side of the bearing. This would lead me to th conclusion that there is a big nut (or something) on the shaft the other side of the plate. Therefore, you have to/can take the plate off without removing the pump cam

 

Richard