AEW Horizon. Lubricant level?

[MAX THE MILLERParticipant @maxthemiller]

The lower gearbox on my AEW Horizon Milling Machine is "sealed for life" with no drain or level plugs. The oil seal on the input shaft has failed allowing most of the lubricant to escape. I have replaced the oil seal.

I have the correct semi fluid grease to refill the gearbox, but the question is how much fluid should I put in? There is nothing in the manual about this. There is no dip stick or sight window. My own idea is to fill it so that the gears on the lower shaft just dip into the fluid. It will then be distributed round the teeth of the mating gears and flung around the inside of the box by centrifiugal force. This level will be below the oil seals.

Anyone know better or have a better idea?

Thanks.

[MAX THE MILLERParticipant @maxthemiller]

[AB658Participant @ab658]

Hi Max,

I don't know your machine, but some observations from a lubrication perspective:-

Do you know why/how the seal failed? Pick-up on shaft; blown out perhaps by pressure build up in the box which might suggest initial overfilling leading to excessive churning & heat build-up? etc.

Is it likely that this is the first time the box has been opened from new? In which case the quantity that ran out was – probably – meant to be there (yes, OEMs don't always get it right, but usually do).

The semi-fluid grease (NLGI 00?) should have the consistancy of custard and should slump down to a level-ish surface.

The "scoop & throw" action of the lower teeth will create a trough that should fill itself quite quickly, but the level will sink until the rate of dropping-back from the interior surfaces equals the rate of picking up. For this reason, I would not be happy about the new level being only at the bottom of the teeth. In operating steady-state conditions that's OK, but at a standstill, it should be higher.

With a new seal – if it's a lip seal, lubricate it before fitting – and a good shaft surface running concentrically, there is no reason why the new level should not be at least up to the seal.

But, no shaft should be running submerged and it's not good practice to have rolling-element bearings anything like fully packed: they will overheat and could cause a seal blow-out in an un-vented box…..

Good luck!

Adrian

[MAX THE MILLERParticipant @maxthemiller]

Thanks for your informative reply Adrian.

I haven't yet run this machine in anger. I'm cleaning it at present.

The specified lubricant for the gearbox is "Shell Tivela compound A". This is a synthetic semi fluid grease with an NLGI consistency of 00. Unfortunately this is only available by the barrel full, so I'm using the Morris Lubricants equivalent.

It's obvious that the lid been removed from the gearbox at some time (probably top up the lubricant) as one of the retaining screws has a stripped thread. I'd say there's way too much lubricant in it, the shafts have certainly been submerged. The lubricant which has leaked out has been picked up by the pulley and belts and thrown everywhere inside the machine. The oil seal has hardened and left a ridge of rubber on the shaft. Don't worry, I'll polish the shaft and lubricate the new seal before fitting it.

I'd describe the existing lubricant as being like lumpy custard. It slumps into a lumpy heap rather than a levelish surface. That's why I'm changing it.

A bit of reading here:-

http://www.hanseatica.com.co/kluber/catalogos/

Reductores/Lubrication_of_gear_Systems.pdf (page 22)

suggests that immersion to 1 to 3 times tooth depth should suffice. It does depend on peripheral speed though, so I'll do some calculations. Immersion of 3 times tooth depth will put the lower shaft just above the fluid level, as the gears are of small diameter.

Edited By MAX THE MILLER on 20/11/2012 22:56:31

Edited By MAX THE MILLER on 20/11/2012 23:02:57

Edited By MAX THE MILLER on 20/11/2012 23:08:51

[Nick HopwoodParticipant @nickhopwood71702]

Hi Max

I have an AEW Horizon vertical milling machine. I don't know what you mean by the lower gearbox. I think you must have a different one from mine. The only gearbox on mine is in the head and there is a filler plug on the top and a sight glass on the side.

I assume yours isn't the same.

Nick

[MAX THE MILLERParticipant @maxthemiller]

Nick.

Mine is a universal machine ie horizontal and vertical. It has two gearboxes. Top one uses Shell Vitrea 41 (old designation) lower one semi-fluid grease.

[AB658Participant @ab658]

Hi Max,

Shell Tivela Compound A was unique at the time of its introduction. Its synthetic nature and specific chemistry was designed to overcome leakage problems & top-up requirements common at the time, by separating into its metallic soap base & synthetic fluid components in the early stages of use. Effectively, the soap was flung around the inside of the housing where it provided an effective sealing function and the lubrication was handled by the fluid. It was so effective that at least one major industrial gearbox OEM redesigned its gearbox casings to remove the top-up & drain facility.

It should not be used in a box that has been run on mineral oil-based lubricants without thorough cleaning and care also when refilling. It should not be allowed to come into contact with conventional oil-based paints (epoxy is fine).

I do not know the Morris product, but do satisfy yourself that their proposal works in the same way

Your description makes me wonder whether a previous owner didn't understand what he was dealing with. A lid-off inspection might suggest that there was insufficient lubricant – as much of the initial fill would be semi-solid on the casing – and topped up with a mineral product, hence the lumps. If he also noticed a leak (due to shaft wear) and replaced the seal with one of a non-compatible material, that could explain the hardening and aggravation of the wear and the leak. Note that a certain amount of oil bleed can take place in storage or inactivity, but this will re-combine in use.

With what we know now, I suggest the following are advisable: 1. clean the box & its internals to the best standard that you can manage; old/new or mixed chemistry is not a good idea; 2. use 100% of whatever product you choose, but do stick to the same behavioural type as already described; 3. change ALL the seals and ensure that the supplier is aware of the product with which they will be in contact.

I have sent you a PM.

Adrian

[MAX THE MILLERParticipant @maxthemiller]

The machine came from a school workshop and apart from the leaking oil seal it's in good condition, although in a filthy state. To change the oil seal the gearbox has to be removed from the main casing. I don't think it's ever been removed though, as the paint over the heads of the contersunk Allen screws holding it to the case was intact. Most likely the leak was noticed and rather than change the seal the gearbox was topped up with who knows what from time to time.

I shall take your advice on board and report back when the job is done.

[MAX THE MILLERParticipant @maxthemiller]

I think I've found the answer to this one. I've obtained the parts list for the machine and this shows a sight glass half way up the side of the box. My box has no sight glass and no boring in the case for it. The question is, was the sight glass ftted to early models and ommitted form later models or vice versa? I suppose it's possible early models used gear oil and were fitted with a sight glass so that the level could be checked. When a change was made to "Compound A" the boxes were considered sealed for life and a sight glass was no longer needed. Filling the box up to the half way mark will result in the lower two shafs and bearings being submerged. Sorry I can't use paragrphs in my post, but this forum doesn't recognise the CR Key. Max.

[AB658Participant @ab658]

I agree with your assessment of the design change, probably co-incident with a fluid change to TCA. If the box is now properly clean internally – no possibility of contamination with earlier mineral oil residues, if any – then filling to a similar level to that indicated by a sight glass, had one been fitted, should be OK. Assuming that the Morris product works in the same way as TCA, a proportion of the volume will attach itself as a coating to the internal surfaces, so lowering the final fluid level. By what proportion I cannot say, but if in use the box becomes too hot to touch, I'd have the top off again. Unlikely to be too little, but might be too much. Adrian

[TrevorhParticipant @trevorh]

Hi All

irrespective of the type of gearbox, in Industry we always fill to just below the shaft, this ensures that the lubricant is in contact with the gears and is splashed around to coat all other parts within and allows for expansion when it gets to its optimum temperature

cheers

[AB658Participant @ab658]

Fully agree: for an all-oil product, whether mineral or synthetic, it all runs back and in steady state operation only the lowest teeth should be submerged. But here we're talking about an unconventional product that separates permanently into the oil component (the lubricant) and a self-supporting metallic soap (the sealant) in the first few minutes of use. The soap starts off as part of the fluid volume, is separated in early use to coat the entire internals, and never returns. To achieve the correct ultimate fluid level, the initial charge needs to be greater. A

[MAX THE MILLERParticipant @maxthemiller]

All the original lubricant, which resembled lumpy black custard, was removed from the box. The box was then rinsed out several times with paraffin and wiped dry. The faulty oil seal on the input shaft was then replaced, having first made sure that the surfaces of the shaft coming into contact with the oil seal lip were not damaged. The box was then filled with semi fluid grease up to a level just below the bottom shaft. When driven under no load conditions the box whined slightly, but as this is a constant mesh box it wasn't possible to tell whether the whine was down to bearings or spur cut gears meshing. When the top cover was removed the semi fluid grease was found to have coated all the internal surfaces of the box. after several days it had not all migrated to the bottom of the box as an oil would. I intend to fill the box up to the halfway mark and see how it sounds then. The problem with TCA, unless someone here knows differently, is that it cannot be purchased in small quantities. You have to buy a drum full which costs a fortune. The replacement product I am using is a synthetic semi fluid grease WITHOUT Extreme Pressure additives. This is good because the box contains some yellow metal bearings. Other Semi fluid greases are available, but they are of the EP type. The top gearbox of the machine, which is oil lubricated has a sight glass which sets the oil level just below the bottom shaft. This would appear to confirm that the bottom box should be half filled with TCA, as indicated by its sight glass.

Edited By MAX THE MILLER on 04/07/2013 22:53:29

[AB658Participant @ab658]

Sounds like the replacement product is of conventional formulation using a synthetic fluid. Thus the fill quantity should be assessed as if it were any other semi-fluid grease, or oil. You refer to the lower shaft: what hangs below that, i.e. the approx. dimension to the lowest gear teeth? And an indication of box dimensions/volume would be helpful to judge it. NB: I've sent you a PM. A.

[MAX THE MILLERParticipant @maxthemiller]

AB658. I've replied to your PM.

The box is an irregular shape. I would estimate that it would take about 1 litre of fluid to fill it to just below the level of the lowest shaft, a depth of about 5 cms. The gear on this shaft is quite small, so if its teeth are to dip into the fluid, the fluid must almost touch the shaft.

To half fill the box would probably require about 2 lires of fluid, a depth of about 9 cms. Total depth of box is about 19 cms

I estimate the internal surface area of the box at about 2000 sq cms. All intenal surfaces are covered with a layer of grease about 3mm deep. This shows no signs of migrating to the bottom of the box.

The mass of grease in the bottom of the box will move, albeit slowly if the box is tilted.

Max.

Edited By MAX THE MILLER on 05/07/2013 21:00:51

Edited By MAX THE MILLER on 05/07/2013 21:01:49

Edited By MAX THE MILLER on 05/07/2013 21:02:40

[AB658Participant @ab658]

Hi Max, One last check: with a (gloved) finger, try to establish whether the newly deposited material is of similar consistancy to the bulk product. If the former is drier or stiffer, more may adhere, whilst if they're similar, it's doubtful that any more will adhere and you've reached a steady state. From then on, anything picked by the submerged gear teeth will return. However, from your description of a small gear, I wonder whether submerging the lower teeth alone will throw enough around to lubricate the other components continuously. With a semi-fluid product, rate of "slump" is important to maintain the process. Apart from the parallel parts of the shaft, what potential sources of "windage" and friction would be submerged if you were to half-fill the box? A

[MAX THE MILLERParticipant @maxthemiller]

 

The lubricant which is adhering to the inner surfaces of the gearbox appears to be of the same consistency as the lubricant in the "sump". It shows no signs of moving due to gravity and is in a layer about 3mm thick on all surfaces. I think it has found its way on to the surfaces, not because it's been flung off rotating gears, but because I stood the box on each end in turn to allow lubricant to flow into the bearings and "prime" them.

Attached is an end view of the gearbox. The shaft protruding from the RHS connects to the gear selection lever. The three step pulley is on the output shaft. The lowermost blanking plug shows the position of the input shaft and the uppermost blanking plug shows the position of the intermediate shaft. Were a sight glass fitted it would show the lubricant level as being up to the lower edge of the upper blanking plug.

The pinion on the input shaft is barely bigger than the input shaft itself. At present the lubricant level is such that the input shaft is not submerged, so the teeth of the pinion barely dip into the lubricant. The pinion is in permanent mesh with a large gear on the intermediate shaft. Neither the pinion or the large gear mesh with any other gears.

The intermediate shaft also carries a cluster of three gears which can slide along it to mesh with three matching gears on the output shaft. None of these gears dip into the lubricant at present.

I'm now convinced that the lubricant level should be as shown by the missing sight glass. This will mean that the input shaft is submerged. The intermediate and output shafts will not be submerged, but all of the gears on them will be about 1/3rd submerged. This means that much more lubricant will be thrown about inside the box due to centrifugal force.

Max.

Edited By MAX THE MILLER on 07/07/2013 21:23:56

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Edited By MAX THE MILLER on 07/07/2013 21:25:35

Edited By MAX THE MILLER on 07/07/2013 21:27:36

[AB658Participant @ab658]

Clear. The rotation & lubricant transfer between the constant mesh pinion & the intermediate shaft gear is of little help in lubricating the change gear pairs. To achieve that the fluid level, in steady-state running conditions, should reach the lowest teeth of the highest-positioned gear pair, plus a bit to allow for the fluid that's flying about at the time. Which sounds like the level you are considering. A

[mal butlerParticipant @malbutler23559]

Hello max I had a AEW recently which I sold I now have another with swivelling table.The first one I had I discarded the lower gearbox and used a layshaft with a 3 to1 reduction and ran through an inverter. As the motor was wired for star I had to find the star centre so I could wire it delta. I intend doing the same again as the lower gear box on my new one is noisy as is the upper gearbox I was wondering if you had any parts drawings of the upper gearbox and how to dismantle it. It looks like a quite complicated task. I also made a table power feed unit. I replaced the centre table switch with a double throw switch to control the table movement.

I have sent you private email

Mal

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