Lubricant

[Tim CooperParticipant @timcooper90034]

I am just starting some maintenance on my Robbe Dusseldorf.

The motors are Robbe Navy Compact (I think). The motor has a small metal gear, this meshes with a larger nylon gear on the prop shaft, all inside a plastic gearbox.. I have usually smeared them with lithium cycle grease. This seems to have gone to a thick paste since last time I took the gearbox apart. It's a bit of a swine to undo. This time I have liberally wiped 3 in 1 over both gears .

Is this a good lubricant for metal to nylon meshing gears.

Tim

[Tim CooperParticipant @timcooper90034]

[ashley needhamParticipant @ashleyneedham69188]

Grease can dry out over time. Perhaps Vaseline or a silicon grease….?

Ashley

[Richard SimpsonParticipant @richardsimpson88330]

3 in 1 is generally regarded as a light lubricant and will quickly be displaced by the loading on the teeth. This will lead to them being unprotected and prone to premature wear.

You need a lubricant which is specifically formulated to A) Take the load and B) Stay in place on the teeth. Automotive all purpose grease is as good as anything for gear wheels or at least a grease designed for gears. Grease does contain volatiles which will slowly evaporate over years so should be changed occasionally.

Edited By Richard Simpson on 17/08/2021 23:02:18

[Tim CooperParticipant @timcooper90034]

Thanks

I will have another look at it whilst I have it on the bench.

Wish I had thought to ask the question before putting the gearbox back together.

Tim

[Richard SimpsonParticipant @richardsimpson88330]

Think positively, at least you asked the question before you used the gearbox again!

[Paul TParticipant @pault84577]

In small gearbox situations I use Lanolin oil, the rotation of the gears keeps the oil moving inside the case and everything remains lubricated.

Any light oil will do the job but check that it doesn't react with nylon.

To avoid over pressuring the case don't fill more than 15% of the gearbox internal capacity

Edited By Paul T on 18/08/2021 10:52:05

[Tim CooperParticipant @timcooper90034]

Thanks

I'll grab the tools I need, make a mug of coffee and get it done .

Tim

[Richard SimpsonParticipant @richardsimpson88330]

My apologies, I had assumed that we were talking of a simple cover to prevent the lubricant being splashed around the model rather than a proper sealed gearbox that will actually hold oil. If it is a sealed gearbox then an oil would be fine but if it is just a cover then a grease would be the best option.

[Tim CooperParticipant @timcooper90034]

Richard

That's ok. It came apart much quicker this time. I have used some grease but not too much.

The Robbe Navy come with a nylon gear fixed to the prop shaft, and a metal one on the motor. One half of the gear box is fixed to the prop tube which is then fastened to a bullkhead. A cover plate and the motor are located from the other side of the bulkhead. Bolts go through the gearbox and cover plate to the motor. The bolt heads are on the gearbox side. Space here is limited by the deck, rudder servo, and a water pump. The bolt heads take an Allen key.

For obvious reasons it's been a while since I used this model so I thought I would check everything. Still Have the working features to check.

Tim

[Paul TParticipant @pault84577]

Richard

Isn't it odd that two engineers would make different assumptions about the same subject.

Even though closed gearboxes are quite rare in model building, I still went completely the other way to you and assumed that it was a closed unit rather than an open set of gears, it never occurred to me that we might be discussing an open set,

I hope that no one has applied my recommendations to an open gearbox as this will be the quickest way to share lubricant to every surface within a 2m radius.

Paul

[Richard SimpsonParticipant @richardsimpson88330]

When I saw your post I thought "Blimey Paul must know something I don't!"

I guess between us we have covered all possibilities!

[ashley needhamParticipant @ashleyneedham69188]

I would think for just two gears the merest smear of something would be adequate? An alternative might be spray grease as used for motorbike chains but that's an expense when a dab of vaselene on a stick would do??

If the boat was running at max power for hours and hours, perhaps but for the use its going to get..

I of course understand the need for adequate lubrication as an engineering thing but perhaps in this case there may be a danger of overthinking the issue. Did the new unit come ready lubricated or as I suspect, dry.

ONLY my thoughts for discussive purposes.

Ashley

[Malcolm FraryParticipant @malcolmfrary95515]

Metal rubbing or thumping metal, lubrication has always been a good idea. Metal to metal gear teeth, definitely lube. Metal to plastic, less so. Any atmospheric muck will incorporate into the lube and be thumped by the metal gear teeth into the plastic teeth.

Plastic gears have been touted as self lubricating, but that depends on the plastic involved. Bearings are another thing again.

The gearbox on top of a servo has lots of gears and usually a smear of grease, but I suspect that that is there more for the rubbing faces of gears against each other in a pile, and bearing surfaces, rather than the teeth, and that space is generally clean and sealed.

E&OE

[Richard SimpsonParticipant @richardsimpson88330]

Posted by ashley needham on 20/08/2021 09:23:04:

I would think for just two gears the merest smear of something would be adequate? An alternative might be spray grease as used for motorbike chains but that's an expense when a dab of vaselene on a stick would do??

If the boat was running at max power for hours and hours, perhaps but for the use its going to get..

I of course understand the need for adequate lubrication as an engineering thing but perhaps in this case there may be a danger of overthinking the issue. Did the new unit come ready lubricated or as I suspect, dry.

ONLY my thoughts for discussive purposes.

Ashley

I think while we would all agree that a minimum of lubrication is adequate what Paul and I were sharing was that the thinking is quite different depending on an enclosed gearbox as against open gears with a cover. The initial post was suggesting that 3 in 1 oil could be used. If this is used on open gears it is not a suitable lubricant.

I think motorcycle chain lube, being a wax base, might prove to be too sticky for small motor gears and increase the load on the motor.

Edited By Richard Simpson on 20/08/2021 11:26:23

[ashley needhamParticipant @ashleyneedham69188]

I am just writing without having done ANY research, but does MFA specify any lubricant for their all-in-one epic motor/gearboxes? Last time I looked there didn’t seem to be any lube present?

Ashley

[Tim CooperParticipant @timcooper90034]

I have used Some general motor grease now. Not packed the gearbox just a good smear on each gear and the bearing.

The MFA geared motors always seem to me to be lightly oiled.

Next model to be checked over is a Model Slipway Aziz, which has 2 MFA geared motors. I think in the past I have just oiled them an put the plastic cover back.

Tim

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