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billybobbooth

National gearbox

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Ok needs some semi urgen help on this. Ive got 3 problems

 

1 oil is getting from the geabox sump into the drive system of the clutches and causing reverse to slip at higher rpm back down it will bite and then be ok for a bit then slip the only wear inside the box is the reduction gears the clutches are ok just coated in oil. I know its getting in from the gearbox side and not the engine side.

 

2. My reduction gears are shot there still ok but there in a way i can copy them but a few years time might tell a diffrent story.

 

3. I beleive the wear to the gears is due to them running engine oil not gear oil. Is there any way to run them on gear oil. I.e. can you just blank off the feed to the engine sump and use it as a seperate sump on the gearbox as designed?

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Are the reduction gears spur or helical. Helical cut gears would definitely need an EP gear oil because there is more frictional rub on the teeth as they mesh.

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Engine oil is fine in the gearbox, clutches slipping has nothing to do with oil on them and everything to do with wear or bad adjustment of the gear change arrangement. Excessive wear may have been caused by not winding it into gear fully- it is sometimes necessary to give the control wheel a really strong wrench to get it in gear. Slipping clutches for long periods will cause excessive wear as will changing gear without slowing the engine down.

As an aside, we used to run an old loading shovel, Perkins engine and what appeared to be a conventional automotive clutch, the clutch bell housing was connected by oil ways to the engine sump, so the lined clutch was always running in oil. It worked perfectly well, the idea of the oil was to soften the drive take up as the nature of the machine involved a lot of F-N-R work

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Engine oil is fine in the gearbox, clutches slipping has nothing to do with oil on them and everything to do with wear or bad adjustment of the gear change arrangement. Excessive wear may have been caused by not winding it into gear fully- it is sometimes necessary to give the control wheel a really strong wrench to get it in gear. Slipping clutches for long periods will cause excessive wear as will changing gear without slowing the engine down.

As an aside, we used to run an old loading shovel, Perkins engine and what appeared to be a conventional automotive clutch, the clutch bell housing was connected by oil ways to the engine sump, so the lined clutch was always running in oil. It worked perfectly well, the idea of the oil was to soften the drive take up as the nature of the machine involved a lot of F-N-R work

I cant coment on other owners but i aways slow down engine before changing gear even when winding or in an emergency.

 

It only does it in reverse which has the clutch near the gearbox sump it will never slip in forwards. The forwards gear has very little oil on it but the reverse gear is covered in gear.

 

If you turn it harder in gear it makes no diffrence even quickly taking it out of gear and back makes no real diffrence only slowing the engine right down you hear it bit again and will be ok for around 5 sec and will slip other times it wont slip seams to do it more once the egine oil is hotter it also forces oil out the top of the box between the gear selector tube again only once engine oil is hot hence why i think its the oil.

 

Reason i asked about oil is the gearbox has a drain and fill point. But one is blanked and the other conected to the engine sump.

My very poorly reduction gears

post-17927-0-87843200-1485561301_thumb.jpg

post-17927-0-53906000-1485561382_thumb.jpg

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Looking at those gears its amazing your still able to move. New parts needed quickly.

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Two reasons for oil coming out of the top of the box- one , it's getting too hot , either because of slipping clutches or overhot engine and two: there is too much oil in the gearbox AND the engine, reduce the total amount and check the link pipe between engine and gearbox for blockage. The gearbox case should be just warm even after a long run, not mad hot.

I say again, any amount of oil on the clutches does not cause slipping,but wear in the clutches will- there comes a point when the clutches just won't engage properly, however much you try to adjust. Judging by the state of the reduction gears, your options are diminishing.

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Yes it does smell warm every now and then, im changing the engine oil so my intention is to change all the oil pipes on the engine as some have been soldered where they have clearly perished at some point, im trying to get new gears made up but if i cant get them done yet hence my question about being able to run it on gear oil and remove the joining pipe.

All this as i couldnt get my engine tray out without taking the box off,

 

Heat wise ive never checked the gearbox temp but engine in normally only just warm the engine coolant never get warm, but the oil smells very stale when hot, the oil level on the engine is exactly half way between the max line and min line. I must admit when i took the gearbox off there wasnt a mad rush of oil out of the feed pipe.

I double checked i def cant see any score marks of eather the gearbox housing or the clutches im hoping i can find some spare gears or get some made by end of feb as thats when i need to next move.

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That looks expensive. I don't know the arrangement of the reduction on your box but if it is separate from the box I would consider sprockets and chain or multi belt pulleys. I think the gears are probably case hardened (others will know) and if they are worn like those then they are probably not much more than mild steel remaining now. Sorry, don't know of any gearcutters.

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There was a very good gearbox specialist in Hayes town, not far from the train station. They certainly took on custom work, but I can't remember the name of the business.

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That looks expensive. I don't know the arrangement of the reduction on your box but if it is separate from the box I would consider sprockets and chain or multi belt pulleys.

That would change the direction of prop rotation!

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Are the reduction gears spur or helical. Helical cut gears would definitely need an EP gear oil because there is more frictional rub on the teeth as they mesh.

BMC/BL Mini's, 1100, 1300 & Maxi gearboxes all ran fine on engine oil with their common sump. Hypoid bevel gears in the old type rear axles need EP though.

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Reason i asked about oil is the gearbox has a drain and fill point. But one is blanked and the other conected to the engine sump.

My very poorly reduction gears

 

I've never seen gears like that before. Its as if corrosion, cavitation or some other random metal removal has taken place such as getting extremely hot and hot welding has taken place.

 

What is most surprising is the surface is the same both sides of each gear. I would expect the wear side surface to be far worse than the non-wear side.

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No there not good would explain the excessive wine from the box when in gear for these type of boxes.

 

But why these gears are poor and the rest of the box is perfect is odd. As there is no wear or play on any of the bearings and the clutch groves are 2mm deep.

 

Ive also think ive found the problem with reverse slipping every now and then and the gear rod out of the box was adjusted all the way down meaning when selecting reverse you ran out of thread just as reverse was selected hence why only doing it in reverse as forward had all the adjustment it wanted.

Think were going to have the redone to strait gears, and get a few made of each will cost more but we will always have a spare.

Next question is how long has it run like this but that well never know. I dont have any idea if the box has ever been rebuilt.

Edited by billybobbooth

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As these gears are used in both directions there isn't a non-wear side, just a less-wear side.

 

Are we talking of 'both directions' as in forward or reverse?

 

I would hope there might be a whole lot more forward than reverse!

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Looking again at the first picture it looks like someone has used a centre punch to stop the nuts from loosening, maybe they became loose prior to this being done, causing the damage to your gears? I'd be concerned as to where all the metal fragments have ended up as well.

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Well there is no metal in the gearbox side the oil isnt even got any signs of silver in the engine was rebuilt in 08 i think it was so this may have been prior to this.

Ill drain the engine sump later this week if i can ive just got to be very carefull as the engine is sat on blocks to get the old oil tray out. Ive seen inside the engine threw the side and the oil i could see was again black but i didnt see any metal in it. As ive already had quite a bit off doing the deconversion from semi rn back to national. After doing this the engine was so much better far better oil pressure and far far less smokey.

 

But will post with any findings. So i can get to the bottom of it.

 

I cant say about the gearbox nuts but the rear engine to drive plate nut was tight but not tight at the same time and the plate could move a little on removing the nut had been punched to stop it turning but the dowl in the guide had been worn ive got a new one to put in and have cleaned the crank gap for the dowl so the new one shouldnt move ive just got to find a long enough socket to put it on with the only damage is to the dowl and the reduction gears the rest is damage free.

Edited by billybobbooth

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Well that went well, cant get the small gear off the shaft, had a puller on there and nothing all it did was start to strip a thread on the puller a little bit. Without getting that off ive got no chance of getting new gears made. I have but 3 options try as much as pos as potentially brake my gearbox buy another replacement gearbox and pray its in good condition or able to be rebuild or 3 send my box off get a massive bill but a rebuild gearbox with new gears.

I know malcome has one but its no use its got 3 damaged gears in that and if i cant get my gears off i cant even swap my good parts over.

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Well that went well, cant get the small gear off the shaft, had a puller on there and nothing all it did was start to strip a thread on the puller a little bit. Without getting that off ive got no chance of getting new gears made. I have but 3 options try as much as pos as potentially brake my gearbox buy another replacement gearbox and pray its in good condition or able to be rebuild or 3 send my box off get a massive bill but a rebuild gearbox with new gears.

I know malcome has one but its no use its got 3 damaged gears in that and if i cant get my gears off i cant even swap my good parts over.

Have you tried heat on the errant gear?

 

George ex nb Alton retired

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Heating one spot fast on the side of the gear would expand it enough to release it. You do it fast waving around in one spot so as not to melt it. Oxy-acetylene is the way, small very hot flame.

Edited by bizzard

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I have no idea what access is like.

 

1 Bigger puller

2 chain drill along a tooth valley, cold chisel and remove

3 drill into the side of the gear and pull (harder)

4 angle grinder to remove one side of the gear close to, or down to shaft

 

2 and 3 will only work if the gear hasn't been tempered, but given the state of the gears, any temper they had must be long gone!

 

Heat is more likely to work if dissimilar materials. It can work but also seen what was a cold-weld just get worse.

 

Good luck!

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