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David Mack

Wanted - Brunton Gearbox Manual

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Does anyone have a manual for a Brunton gearbox, as fitted to a National 2DM? Or failing that, can anyone tell me how to check and adjust the reverse brake band?

 

Thanks

 

David

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Does anyone have a manual for a Brunton gearbox, as fitted to a National 2DM? Or failing that, can anyone tell me how to check and adjust the reverse brake band?

 

Thanks

 

David

 

There isn't a brake band, there are cast iron cone clutches for ahead & astern.

 

What seems to be the problem?

 

Tim

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There isn't a brake band, there are cast iron cone clutches for ahead & astern.

 

What seems to be the problem?

 

Tim

 

Thanks Tim. Haven't looked inside yet, I just assumed there was a brake band.

 

We just get the feeling that sometimes it isn't fully engaging in reverse. So wondering what we should adjust before the problem gets any worse.

 

David

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Thanks Tim. Haven't looked inside yet, I just assumed there was a brake band.

 

We just get the feeling that sometimes it isn't fully engaging in reverse. So wondering what we should adjust before the problem gets any worse.

 

David

 

There is no adjustment, as such.

 

Does it ever stick in astern gear if you've wound it in particularly hard?

 

If it never does, it could be a clue that the astern cones have developed a 'step' or that the control mechanism is bottoming out in some way before it applies full pressure to the cone assembly. I can't honestly remember what the screwed brass sleeve on the control column does, & it doesn't appear in the 'instruction sheet' description or drawings. If it's the nut for the control screw, then screwing it up or down might affect the available travel of the cone assembly. Sorry I can't be more specific, it's a few years since I had one apart.

 

Tim

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I know its old but related. Is there any way to shorten the amount of turns you need to make the gearbox engage? I seam to have to turn for a life time. Ive never had one apart so i cant say whats in them. I dont really like something ive not seen inside or use to. I love the engine but would trade it quite happily.

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Hi as far as I know there is no way to reduce the travel, mine is exactly the same, I have played about with the threaded collar on the gear change tower but have not noticed any particular difference. One day I must take it apart and see how it all works. I have a copy of the information sheet for it if it is any interest to you?

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I know its old but related. Is there any way to shorten the amount of turns you need to make the gearbox engage? I seam to have to turn for a life time. Ive never had one apart so i cant say whats in them. I dont really like something ive not seen inside or use to. I love the engine but would trade it quite happily.

 

Given that it's general a crown gear and pinion, you could always change the ratio.

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Given that it's general a crown gear and pinion, you could always change the ratio.

I don't think it is, unless you mean at the roof, not in the box. If you did reduce the ratio for less turns F-N-R you'd need Charles Atlas driving it. Them Brunton boxes are heavy going even with the standard set up.

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Then there's something a little odd, my Brunton gear wheel is less than a full turn forward to reverse with the original GU crown gear and not at all heavy. Although it takes a bit of a kick to engage fully, there is no straining.

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I don't think it is, unless you mean at the roof, not in the box. If you did reduce the ratio for less turns F-N-R you'd need Charles Atlas driving it. Them Brunton boxes are heavy going even with the standard set up.

 

It isn't, . . . . it's nothing like a crown wheel and pinion arrangement, . . . . . either inside the box, or under the engine hole top.

 

In the [vertical] operating column, which is secured with 4 x bolts to the gearbox casing, is a large square threaded 'nut', under the external threaded retaining collar, through which the operating shaft moves up or down. At the bottom end of the operating shaft is a smaller diameter and finer pitch thread which goes into a phosphor bronze trunnion, which moves the mainshaft, and thus the ahead and astern clutch cones, into engagement by means of a bell crank lever and yoke.

There is no adjustment for wear on either the ahead or astern clutches. As the clutches wear the wheel simply turns a little further either way from neutral before the gears engage.

 

The wheel shouldn't be heavy, or stiff, to turn, and if it is, then there's something wrong.

Correctly set-up and in good order the gearwheel can be spun from neutral into either ahead or astern gear with only the thumb and fore-finger.

Edited by Tony Dunkley

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I know its old but related. Is there any way to shorten the amount of turns you need to make the gearbox engage? I seam to have to turn for a life time. Ive never had one apart so i cant say whats in them. I dont really like something ive not seen inside or use to. I love the engine but would trade it quite happily.

 

Hi as far as I know there is no way to reduce the travel, mine is exactly the same, I have played about with the threaded collar on the gear change tower but have not noticed any particular difference. One day I must take it apart and see how it all works. I have a copy of the information sheet for it if it is any interest to you?

 

The only way to reduce the gear wheel movement from neutral into either gear, is to renew one or both of the clutches.

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Hi as far as I know there is no way to reduce the travel, mine is exactly the same, I have played about with the threaded collar on the gear change tower but have not noticed any particular difference. One day I must take it apart and see how it all works. I have a copy of the information sheet for it if it is any interest to you?

Yes please!!!!!

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The only way to reduce the gear wheel movement from neutral into either gear, is to renew one or both of the clutches.

How the hell do you do this??

 

I have all the gu original parts my plan was if i have to put a new roof gear in.

 

Backly i want it semi short as i keep smacking my head on thr wheel. The other reason im wanting to swap from wheel to a push pull leaver as towy never had a wheel there, i then want to change the speed leaver and wire to a wheel then intend to put a kill leaver in where reverse leaver use to be for a bolly. I haven decided what to do about an oil rod position.

 

Reason being i want it as much to look like it wiuld in the 50s from the cabin views ov except engine unless i can get a bolly but i also notice i have to do about 4-5 turns stop to stop points but a tiny movement and its turning the prop really hard to find neutral to start it have to turn engine over and play to find middle.

 

 

The only way to reduce the gear wheel movement from neutral into either gear, is to renew one or both of the clutches.

How the hell do you do this??

 

I have all the gu original parts my plan was if i have to put a new roof gear in.

 

Backly i want it semi short as i keep smacking my head on thr wheel. The other reason im wanting to swap from wheel to a push pull leaver as towy never had a wheel there, i then want to change the speed leaver and wire to a wheel then intend to put a kill leaver in where reverse leaver use to be for a bolly. I haven decided what to do about an oil rod position.

 

Reason being i want it as much to look like it wiuld in the 50s from the cabin views ov except engine unless i can get a bolly but i also notice i have to do about 4-5 turns stop to stop points but a tiny movement and its turning the prop really hard to find neutral to start it have to turn engine over and play to find middle.

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How the hell do you do this??

 

I have all the gu original parts my plan was if i have to put a new roof gear in.

 

Backly i want it semi short as i keep smacking my head on thr wheel. The other reason im wanting to swap from wheel to a push pull leaver as towy never had a wheel there, i then want to change the speed leaver and wire to a wheel then intend to put a kill leaver in where reverse leaver use to be for a bolly. I haven decided what to do about an oil rod position.

 

Reason being i want it as much to look like it wiuld in the 50s from the cabin views ov except engine unless i can get a bolly but i also notice i have to do about 4-5 turns stop to stop points but a tiny movement and its turning the prop really hard to find neutral to start it have to turn engine over and play to find middle.

.

 

If you've got 4 - 5 turns from ahead to astern, then either the bevel gears under/in the engine hole top have been changed from the 1 : 1 bevels that were fitted originally, or there is a lot of cumulative wear in clutches, mainshaft bearings and bushes, and internal operating components, and probably excessive engine crankshaft end-float as well.

Edited by Tony Dunkley

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If you've got 4 - 5 turns from ahead to astern, then either the bevel gears under/in the engine hole top have been changed from the 1 : 1 bevels that were fitted originally, or there is a lot of cumulative wear in clutches, mainshaft bearings and bushes, and internal operating components, and probably excessive engine crankshaft end-float as well.

Shouldnt be excessive engine end float its ment to have had a compleate rebuild

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Shouldnt be excessive engine end float its ment to have had a compleate rebuild

 

The crankshaft end-float is set by means of shims behind the ahead [female] clutch cone thrust bearing, between the clutch cone and the timing case end cover.

I can't remember the last time I saw one that didn't have too much end-float, caused either by wear in the ahead clutch thrust bearing or not being shimmed up correctly during assembly.

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The crankshaft end-float is set by means of shims behind the ahead [female] clutch cone thrust bearing, between the clutch cone and the timing case end cover.

I can't remember the last time I saw one that didn't have too much end-float, caused either by wear in the ahead clutch thrust bearing or not being shimmed up correctly during assembly.

Ah ok thought was done by trust bearing in block, but im blind on these engines and boxes.

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Ah ok thought was done by trust bearing in block, but im blind on these engines and boxes.

 

 

Crank end-float in the direction of [towards] the gearbox can only occur in either neutral or astern gear and is limited by the front thrust face of the centre main bearing. The force of the end-thrust in that direction is only the same as any other engine, ie. minimal, and the thrust face acts mainly in locating the crankshaft and limiting movement.

 

When the Bruntons box is driving in ahead gear, there is a fairly hefty end-thrust force applied to the crank in the direction of [towards] the flywheel, acting as a self-servo engagement force to hold the ahead clutch in when it's transmitting power.

 

To engage either ahead or astern gear, the gearbox mainshaft, and the male cones of both sets of clutches moves/slides either towards or away from the engine, and due to the orientation of the helical cut teeth on the reduction pinion and wheel, the clutches are forced harder into engagement as the the power they're transmitting increases.

 

There is a separate [ball] thrust bearing within the mainbox to look after the astern thrust from the helical gears, but when ahead gear is engaged, the ahead thrust from them is transmitted directly to the crankshaft via the [female] ahead clutch cone which fits to a taper on the timing case end of it.

 

To ensure that all the gearbox thrust is taken by the [ball] thrust bearing, the timing case end of the centre main crankshaft bearing of a National marine engine is shortened slightly by having a generous amount machined off the timing end thrust face in comparison with the industrial version of the same engine. This is why Nationals fitted with Bruntons boxes and the marine engine centre main crankshaft bearing are frequently found with excessive crankshaft end float due to the thrust bearing not being shimmed up correctly.

Edited by Tony Dunkley

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Hi as far as I know there is no way to reduce the travel, mine is exactly the same, I have played about with the threaded collar on the gear change tower but have not noticed any particular difference. One day I must take it apart and see how it all works. I have a copy of the information sheet for it if it is any interest to you?

Hi Bobl

I am trying to build a spare Brunton box and a copy of the information sheet would be wonderful.

I believe the only part I am missing is the main gearbox casting itself.

I need to have both gearbox shafts turned up to replace the unusable originals, any one any ideas on what steel would be appropriate?

The threaded collar appears to only set the range of travel for the fine thread below, or if you like set the centre of the available movement.

Bob Tidy

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Right ive got to do an oil change so whilst the boat isnt going anywhere for a month+ due to current loacation and dock work and other work im doing im going to try and get my leaking oil drip tray out and replace it.

 

Im hoping u dont have to lift the entire engine as discussed on the forum before as this is no easy task.

 

Due to oil change i was thinking of removing the gearbox to get access to the drip tray i was hoping to remove the engine bed support block and slide the tray out but this wont move so my next attempt is to remove the gearbox.

 

Question is this fairly simply thing? E.g. remove the bolts to the block and simply pull off? Im not 100% sure i can get to all the bolts so this maybe abandoned before i even start.

 

If not ill have to go with lifting the engine.

Edited by billybobbooth

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Right ive got to do an oil change so whilst the boat isnt going anywhere for a month+ due to current loacation and dock work and other work im doing im going to try and get my leaking oil drip tray out and replace it.

 

Im hoping u dont have to lift the entire engine as discussed on the forum before as this is no easy task.

 

Due to oil change i was thinking of removing the gearbox to get access to the drip tray i was hoping to remove the engine bed support block and slide the tray out but this wont move so my next attempt is to remove the gearbox.

 

Question is this fairly simply thing? E.g. remove the bolts to the block and simply pull off? Im not 100% sure i can get to all the bolts so this maybe abandoned before i even start.

 

If not ill have to go with lifting the engine.

Brave man taking the engine out to sort out a leaking drip tray!

 

I don't know your layout, but I'd be tempted to try and fit another drip tray inside the existing one until the engine has to come out for another reason.

 

Even using plastic which can flex around obstructions during insertion. It's not going to be permanent. Assuming you have a National it will be out soon enough for other reasons! (Sorry, couldn't resist it). smile.png

 

George ex nb Alton retired

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Unfortunately due to being wood and a josher i have no way to get the old tray out or even fit lots of trays in my current tray,

1 it has side ways support blocks for the engine block so no way to slide it out front or back, at the front is the bolly fuel tanks 1 inch from flywheel, at the back i have about 3 inches before the box is in the back cabin and then to top it off i have a 1 1/2 foot by 7 inches of solid wood eather side of the engine.

 

So its box off or engine up. But must be sorted as the oil from the engine goes into the tray and into the floor which over the years has filled my floor with oily water crud mix. Mmmmmm tasty.

 

The only gap to put new tray in would be between the2 side wood engine blocks and the gearbox and the mount point on the gear box so even a small tray is tight as the current tray sits only a few inches under the engine

Edited by billybobbooth

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Right gearbox is off tray out new tray going in, question on the engine side of the gearbox there is a conection plate that i think the forward clutch sits in that is bolted to the engine output shaft is this plate ment to move a few mm round or is the nut ment to hold it tight. I wondered if this is what casusing my reverse to suddenly loose grip and only be ingear lightly till i drop revs then it will bite hard again. Also is it ment to have engine oil in it im guessing yes but surly this on the clutch plates will make it slip?

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