Garden Railway Forum

Well done Rik. That looks fine ( weird as an 0-4-0 ) but fine.

philipy wrote: Wed Mar 03, 2021 7:06 pm Well done Rik. That looks fine ( weird as an 0-4-0 ) but fine.

It reminds me of one of those Hornby tinplate clockwork locos which I used to have running at full pelt on the sitting room carpet as a kid .... My first train set!

Rik

ge_rik wrote: Wed Mar 03, 2021 6:33 pm I think I have identified the problem and fixed it (let's hope that's not famous last words!).

I thought that thing looked like it had been butchered to fit a different motor. You're more patient than me, I'd have long since given it a burial at sea by tossing it off the end of the local pier.......

The butchery was presumably to replace a cooked Mabuchi motor, but possibly also in the vain hope that fitting the same motor that LGB use will make it run like an LGB loco. Not likely with Bachmann gears......

That's the early Lyn chassis, the current one is a better design with metal gears. Bachmann supposedly designed the early drive in the belief that the large worms would act as flywheels, but they aren't heavy enough, or large enough in dia. for that.

Greg also touched on balancing the loco. 0-4-4 tank locos are notorious for losing traction, as they are hard to balance properly. When running funnel first, the load of the train transfers weight off the drivers onto the rear bogie. They run better bunker first, as the weight is then transferred onto the drivers. Try and get as much of the weight as far forward as you can.

Graeme

Well. It's been a while.....
After no end of unsuccessful searching, discussions with Bachmann and contacting several gear manufacturers I eventually tracked down a set of gears which were by no means perfect, but I felt I could use.

The worm has a 3mm bore (the Bachmann motor has a 2.5mm shaft) and the worm wheel has a 6mm bore (the nylon 'axle' on the loco is around 7.75mm).

I used a piece of 3mm copper tube, reamed out to around 2.4mm which is a force fit on the motor shaft. I 'removed' the moulded gear from the axle and turned it down to around 7.6mm (in the chuck of my drill using a flat file) and opened out the hole in the worm wheel to 7.5mm and force fitted it to the remains of the axle.

I redesigned the motor block to reposition the motor and to take the larger worm wheel.

It sort-of works! The gears grind horribly in one direction but are reasonably OK in the other direction, so I've eased the mesh by around 0.2mm. I've also moved the motor 1.5mm towards the worm - there is space, despite how it looks on the photo. I'm not going to be able to centre the worm over the worm wheel unless I can extend the motor shaft somehow.

Getting nearer........ Any tips on meshing gears anyone?
Trouble is, I can't see inside the block once it's assembled and so having to rely on what I imagine is going on inside.

Rik

Congratulations on getting this far Rik. I can't offer any expert advice on positioning/meshing of worm gearing, but from my model boating days, I used to extend motor shafts by fitting an 'interference fit' piece of brass tubing over the exposed motor shaft, and then used the OD of that tubing to size other necessary components. Not sure if that would be any help to you, but I look forward to seeing your progress

Lonsdaler wrote: Tue May 04, 2021 11:47 am Congratulations on getting this far Rik. I can't offer any expert advice on positioning/meshing of worm gearing, but from my model boating days, I used to extend motor shafts by fitting an 'interference fit' piece of brass tubing over the exposed motor shaft, and then used the OD of that tubing to size other necessary components. Not sure if that would be any help to you, but I look forward to seeing your progress

I might try that, using a longer piece of copper tube and then only reaming out half of it...

Rik

ge_rik wrote: Tue May 04, 2021 12:29 pm

Lonsdaler wrote: Tue May 04, 2021 11:47 am Congratulations on getting this far Rik. I can't offer any expert advice on positioning/meshing of worm gearing, but from my model boating days, I used to extend motor shafts by fitting an 'interference fit' piece of brass tubing over the exposed motor shaft, and then used the OD of that tubing to size other necessary components. Not sure if that would be any help to you, but I look forward to seeing your progress

I might try that, using a longer piece of copper tube and then only reaming out half of it...

Rik

Or perhaps one of the expert engineers amonst our members might volunteer to turn you a nice extension sleeve, rather than relying on files and hand drills.

Hi Rik,

That's brilliant, glad you managed to find a solution.

Another option to the meshing issue might be to print new axle muffs that match the new worms?

Rob

p.s. do you take commissions?

RobRossington wrote: Thu Jun 10, 2021 3:20 pm p.s. do you take commissions?

Only if I can charge realistically for the hours I put into sorting them out ......

Rik

ge_rik wrote: Thu Jun 10, 2021 6:14 pm

RobRossington wrote: Thu Jun 10, 2021 3:20 pm p.s. do you take commissions?

Only if I can charge realistically for the hours I put into sorting them out ......

Rik

I assumed that would be the answer

Looking at it would I be right in saying that your new motor block has the motor sat lower so that the new smaller worms can reach the axle gears?

RobRossington wrote: Mon Jun 14, 2021 11:09 am Looking at it would I be right in saying that your new motor block has the motor sat lower so that the new smaller worms can reach the axle gears?

Yes, that's the long and the short of it. A bit hit and miss making sure the gears mesh correctly. As the motor block housing is closed, it's not possible to see the gears or make adjustments. I'm now on my fourth variation..... Way one takes around 18 hours to print....

Rik

ge_rik wrote: Mon Jun 14, 2021 8:20 pm As the motor block housing is closed, it's not possible to see the gears or make adjustments.

At the risk of asking a stupid question, would it be possible to print a small window in one side of the housing, just large enough to see the mesh?

ge_rik wrote: Mon Jun 14, 2021 8:20 pm Yes, that's the long and the short of it. A bit hit and miss making sure the gears mesh correctly. As the motor block housing is closed, it's not possible to see the gears or make adjustments. I'm now on my fourth variation..... Way one takes around 18 hours to print....

I'm fairly sure you can get transparent PLA filament. Print the test housings using that.......

- if the gear mesh is badly out you'll soon know.

- if you are lucky and the mesh is OK, then the clear gearbox won't be clear after a coat of paint.

You'll probably need to hold everything up against a bright light to see the silhouette of the gears and there'll be so much distortion it will be like trying to read a newspaper through the bottom of a beer glass. Still a lot better than printing bits 'ad nauseum' until you get a gearbox that seems to work.....

Some plastics in transparent form are brittle, polystyrene being an example, and others like ABS and HIPS just can't be made in transparent anyway. I've no experience with PLA, so it may be that once you get a working gearbox, you may need to print one more in solid colour to get the physical properties you need.

Regards,
Graeme

GTB wrote: Tue Jun 15, 2021 5:38 am
I'm fairly sure you can get transparent PLA filament. Print the test housings using that.......

........You'll probably need to hold everything up against a bright light to see the silhouette of the gears and there'll be so much distortion it will be like trying to read a newspaper through the bottom of a beer glass. Still a lot better than printing bits 'ad nauseum' until you get a gearbox that seems to work.....

Yes you can get transparent PLA, and I did think about suggesting it, but in my limited experience, "translucent" is more accurate than transparent. I used it for the 'glass' in my platform lamps and its fine with a bright LED inside but not really see-through. It may be possible to improve the clarity by fiddling about with settings, but that would take longer, with uncertain end result, than the hit and miss approach anyway, I'm afraid.

Hi
Yes, I've tried putting windows into the sides but the wheels are in the in the way. The wheels and axle stubs are a single moulding and so I can't align the gears without them.

If my mk IV version doesn't work, I might try designing either a moveable cradle for the motor or moveable mounts for the wheel bearings.

Rik

ge_rik wrote: Tue Jun 15, 2021 7:49 am If my mk IV version doesn't work, I might try designing either a moveable cradle for the motor or moveable mounts for the wheel bearings.

I also thought about whether a multi-piece housing might be a better proposition. Basically a two piece assembly to carry the motor,with separate gear boxes at each end that carry the axles/worm wheel and can be adjusted up and down.

In the case of the wheels getting in the way of seeing the gear mesh, replace them with a simple temporary axle the same dia. while doing the adjustment. Doesn't have to be metal, even a suitable plastic tube would do the job. You might even be able to print something suitable, as all it has to do is pass through the bearings and the bore of the worm wheel to line them up.

Graeme

philipy wrote: Tue Jun 15, 2021 6:09 am Yes you can get transparent PLA, and I did think about suggesting it, but in my limited experience, "translucent" is more accurate than transparent.

I'm not particularly surprised. If I'd thought about it, that printing process is bound to have tiny voids and bubbles dispersed through the part, even if the filament is transparent.

Graeme

GTB wrote: Tue Jun 15, 2021 1:17 pm In the case of the wheels getting in the way of seeing the gear mesh, replace them with a simple temporary axle the same dia. while doing the adjustment. Doesn't have to be metal, even a suitable plastic tube would do the job. You might even be able to print something suitable, as all it has to do is pass through the bearings and the bore of the worm wheel to line them up.

Graeme

That's a good idea. The stub axles have an additional socketed square section on their ends which fit into square holes in the worm wheels. Quite a complex bit of engineering.
However, not outside the realms of possibility of a 3D printer Rik