Noisy gearbox

[bluestag]

Hi,

 

Just a week ago I got to drive my first 7mm loco for the first time, and it was a treat.   My host installed my sound chip, and the LNWR 0-4-0ST was running on his layout.   What is unfortunate is that the gear box from Roxey Mouldings is a noisy one.   It growls.    At the slower speeds of a shunter it is not too loud, but at full throttle it drowns out the sound system.

 

Is this common with a worm and wheel gear?    The box itself is pretty rigid, the motor is small and would not tolerate an inefficient gear box.    The loco runs smoothly (until the wheels get dirty).   Could it be that the gears are not properly meshed?   There may be a bit of play in how the motor fits the gearbox.

 

 

[Simond]

Fag paper.  Buy a packet of blue Rizla.  They are very thin.

 

Presuming your gearbox is a fold-up, and you have soldered down the fold lines, and the axle bearings are soldered in place, and an axle spins freely in them, you need to adjust the mesh.  You also need some washers to ensure that the gearwheel stays centralised in the box, the gearwheel & axle should spin freely, but not have any appreciable sideplay.

 

If you haven’t already done these things, I’d recommend that you do.

 

Also make sure that your worm is not binding on the motor bearings or gearbox, it will move in & out of the motor depending which way the loco is going.  Ensure it spins freely.

 

Adjustment is annoyingly fiddly in most cases, but worth persevering with.

 

There are two screws which secure the motor.  One is completely hidden behind the gearwheel once the box is assembled, but you can reach the other.  

Remove the gear & axle.  

Barely loosen both screws, just enough that you can just move the motor.  

Reassemble the gear & axle with a fag paper between the gear & worm.  

Press the gear and worm together.

Tighten the accessible screw.

Remove the gear & axle and tighten the other screw.

Reassemble & test.

 

all being well, you will now have a smooth, quiet gearbox.  If not, try again.

 

good luck

simon

 

Edited July 21, 2019 by Simond

[doilum]

Why is it easy to do this in one direction only to find it sounds like a tractor in reverse? No amount of running in seems to help.

[Simond]

Hmmm.  Don’t know.  But a few suggestions:

 

Three things happen when you reverse a worm drive.  The motor armature shaft will press against “the other” thrust bearing, and the axle will press against “the other” axle bush.  The motor will also react in the opposite direction.

 

Dependent on the play in the system, this might mean that there is a tenth of a millimetre or half a millimetre of movement in each.  There’s not much you can do about the motor, except put washers between the thrust bearing and the worm, but you can definitely get down to a gnat’s proboscis of play in the axle.  

 

When it moves, check that wheels aren’t rubbing where they shouldn’t.   Ditto, the flywheel, if it has one.

 

You might find that the motor is pressing against the boiler when running one way, and against the chassis the other.  I fit all my locos with suspension or equalisation, so I always fit a torque link which stops the motor hitting stuff, but lets it move with the suspension.

 

hope these suggestions get you on the right track, good luck

Simon

[doilum]

Only half my locomotives have this problem. The others have an ABC gearbox!

[Simond]

I’ve used Portescap, ABC, Crailcrest and fold-up gearboxes over the years.  (And an Atlas and a Lima)

 

My go-to nowadays is Premier Components’ two-stage helical, with a Canon motor, though my Dukedog has a Premier worm & wheel single stage gearbox with the same motor which is fine.

 

atb

simon

[doilum]

Does the inherent problem lie with fold up gearbox? Would a milled frame solve the problem.

[hayfield]

High Level gearboxes are fold up but use plastic gears as well as brass, the quality of the etchings are very good as are the design

 

I also am having issues with the cheaper fold up 7 mm motor mounts, as said the meshing is important, I also think the large areas in the boiler and tank(s) amplify the sound. Must say the more expensive machined gearboxes do run exceptionally well, but the price differential is quite large

[bluestag]

2 hours ago, hayfield said:

High Level gearboxes are fold up but use plastic gears as well as brass, the quality of the etchings are very good as are the design

 

I also am having issues with the cheaper fold up 7 mm motor mounts, as said the meshing is important, I also think the large areas in the boiler and tank(s) amplify the sound. Must say the more expensive machined gearboxes do run exceptionally well, but the price differential is quite large

High Level is 4mm, I'm in 7mm.

 

My gear box has a steel worm and brass wheel. 

 

The body of the loco is a resin casting, which should not resonate at all.

 

I need the fag paper solution.    My particular gear box has the screws at 9 and 3...  

 

Packs of cigarettes in California are about 8 dollars, so I am not interested in buying 20 cigs to get one paper.   But I do have some rolling papers, and they are quite thin.   I bet the tissue paper that my etched kits come wrapped in would do the trick as well.

Edited July 21, 2019 by bluestag
add information

[laurenceb]

Rizla is a UK brand of rollng paper, tissue paper is thicker

[bluestag]

3 hours ago, laurenceb said:

Rizla is a UK brand of rollng paper, tissue paper is thicker

 

I'm in Los Angeles.    I'll use a rolling paper then.

 

Thanks.

[hayfield]

11 hours ago, bluestag said:

High Level is 4mm, I'm in 7mm.

 

My gear box has a steel worm and brass wheel. 

 

The body of the loco is a resin casting, which should not resonate at all.

 

I need the fag paper solution.    My particular gear box has the screws at 9 and 3...  

 

Packs of cigarettes in California are about 8 dollars, so I am not interested in buying 20 cigs to get one paper.   But I do have some rolling papers, and they are quite thin.   I bet the tissue paper that my etched kits come wrapped in would do the trick as well.

 

Sorry if I failed to say High Level gearboxes are 4 mm scale, I mentioned them purely to illustrate that fold up gearboxes can run both well and silently straight from being built without any meshing issues. Probably more to do with the quality of both the parts and design. A great pity Chris does not make a 7 mm version.

 

Most of the single stage motor mounts I have both in 4 & 7 mm scales also have steel worms and brass gears, what is common in both is the tendency for them to be noisey !! coincidence or design flaw 

[Guest Isambarduk]

A number of my older locos have perfectly functioning fold-up gearboxes.  In each case, I stiffened the sides with little gussets and I replaced the steel worm and brass worm wheels with a set of Nylatron worm and brass worm wheel from Ultrascale Gears.  These gears are as quiet as you like and are self-lubricating, so they require no maintenance.

 

 

Here is an example: Great Western Railway 'Dean Goods' 0-6-0

 

David

[hayfield]

David

 

Thanks for the link, but how does one know what gears to buy?

[Guest Isambarduk]

4 hours ago, hayfield said:

how does one know what gears to buy?

 

Well there is no right ones but it would make sense to have them as direct replacements to fit in your existing gearbox. 

 

There will be some adjustment, using the motor retaining screws, to ensure a suitable meshing of the gears so, as a start, I would look for a worm wheel that is about the same diameter as the one that you wish to replace (see the dimension GB in the table below the selection) and check that it gives a suitable ratio. (As an aside, these sets are so quiet and relatively efficient that I tend to go for the lower ratios of 20:1 and 26:1 to keep the motor revs lower so that the motor is quieter.)  If you are not happy with the same (or near) diameter, you can choose a larger worm wheel (higher ratio) or a smaller worm wheel (lower ratio) but you may have to elongate the holes for the motor attachment screws in the garbox to achieve a suitable mesh. 

 

I have always used 'Gear Type 2' because it has a boss and a grub screw, which is far easier to deal with than a the force or glue fit of the 'Gear Tye 1'

 

Finally, you need to specify i) WB (Worm Bore) so that it matches the diameter of the motor shaft, and ii) GB (Gear Bore, ie the bore of the worm wheel) to suit the diameter of the axle that you are driving (usually 3/16" but sometimes 1/8" for small prototypes).

 

I hope this helps but do ask again if I've not made it clear or if I have missed something.

 

David

[bluestag]

Well, I have not solved my noisy gearbox.    I took it all apart and used a wrapping paper for lash, and it is just as noisy as before.

 

What makes this a mystery is that I have built up a loco with the same manufacture of gearbox, Roxey Moldings.   It is also a 40:1 gearbox, and the gears look to be the same.   But it is nearly silent.   I'd swap the gears around but I have already soldered on to the worm wheels spacers to prevent them shifting about on the axle.

 

The difference between the two is the motor.    The noisy box has a Mashima 16XX motor, the new quiet box has an 1833 Mashima.

 

Considering that the new box is quiet, I'm tempted to buy another of the smaller box and hope that I just got some dodgy gears.   Or that I assembled the box skewed.    Possible I suppose, but I don't know.

 

If there was a small machined box that would fit, and fit the smaller motor (it is a SMALL prototype), I'd go that route.

[bluestag]

I have an inquiry into Ultrascale, as suggested.   Their page says it might take 3 months!   And that does not factor in Covid-19.   Really!   I'm as appreciative as anyone of the fact that this hobby is fueled by small operators working odd hours, but 3 months?

 

Anyway, they offer a nylon worm and brass wormwheel that look to be a good fit for the gear box that I have.   Possibly this year I'll be able to run the loco and not have it growl at me.

[Guest WM183]

Noise in one direction but not the other is usually from excessive end play in the worm shaft. Ideally you will have 0 lash, or very close to zero - no more than a few thousandths of an inch. Using the correct type of gear lube can also help tremendously. I think Labelle 102 is what I use in gear boxes of brass imports.

[hayfield]

1 hour ago, bluestag said:

Well, I have not solved my noisy gearbox.    I took it all apart and used a wrapping paper for lash, and it is just as noisy as before.

 

What makes this a mystery is that I have built up a loco with the same manufacture of gearbox, Roxey Moldings.   It is also a 40:1 gearbox, and the gears look to be the same.   But it is nearly silent.   I'd swap the gears around but I have already soldered on to the worm wheels spacers to prevent them shifting about on the axle.

 

The difference between the two is the motor.    The noisy box has a Mashima 16XX motor, the new quiet box has an 1833 Mashima.

 

Considering that the new box is quiet, I'm tempted to buy another of the smaller box and hope that I just got some dodgy gears.   Or that I assembled the box skewed.    Possible I suppose, but I don't know.

 

If there was a small machined box that would fit, and fit the smaller motor (it is a SMALL prototype), I'd go that route.

 

I have the same issues, I have been told its something to do with the meshing. I think I have made one quiet set out of 4 attempts

 

In 4 mm scale I use High Level gearboxes, they are nice, quiet and smooth. If only Chris made a 7mm version, or someone made wheels with 1/8th axles. I have also built a couple of Comet and one Branchlines gearboxes and they are all smooth and quiet in operation

 

Having said all of this I have two DJH gearboxes, the one with a D11 motor is silent, the one with a Mashima has a tinny sound ? These motor mounts and gearboxes are a dark art

[bluestag]

2 hours ago, WM183 said:

Noise in one direction but not the other is usually from excessive end play in the worm shaft. Ideally you will have 0 lash, or very close to zero - no more than a few thousandths of an inch. Using the correct type of gear lube can also help tremendously. I think Labelle 102 is what I use in gear boxes of brass imports.

It's the same forward and back.

 

[DCB]

I'm wondering if the worm wheel is centred over (under) the worm. Worm wheel should be centred under the worm both sideways and length ways. You seem to have shimmed out he sideplay but has that resulted in the gearwheel off centre to one side? 

 Most modern motors seem to have a mile of end float on the armature shaft so you have to split the difference as the worm moves back and forth, older ones had end float adjustment, but generally I associate gear noise with impending failure. I also associate nylon gears with impending failure!

[bluestag]

18 minutes ago, DavidCBroad said:

I'm wondering if the worm wheel is centred over (under) the worm. Worm wheel should be centred under the worm both sideways and length ways. You seem to have shimmed out he sideplay but has that resulted in the gearwheel off centre to one side? 

 Most modern motors seem to have a mile of end float on the armature shaft so you have to split the difference as the worm moves back and forth, older ones had end float adjustment, but generally I associate gear noise with impending failure. I also associate nylon gears with impending failure!

The wheel is not EXACTLY centered under the worm, but it is close.    It is remarkably tedious to get the wheel in a particular place under the worm.    The Roxey gearbox does not have any shims.    I own a lathe, so was able to turn a mess of shims of various thicknesses, and then just tried them until one fit well.    For me they need to be soldered to the wheel, or there are just too many fiddly bits to thread onto the axle.   My Mashima does not have much end float, so I don't think that is the problem.    I'll try the delrin worm and hope.

[doilum]

I remember Jim McGowan of Connoisseur Models publishing a guide to the black art of gear meshing. I have come to the conclusion that it is probably down to manufacturing tolerances in the budget gear sets. One in ten is perfect, one unusable, the rest in between?

[Guest WM183]

17 hours ago, bluestag said:

It's the same forward and back.

 

 

For some reason I thought you'd written that it was worse forward. I can read, I promise.

[bluestag]

2 hours ago, WM183 said:

 

For some reason I thought you'd written that it was worse forward. I can read, I promise.

No fear.