Garden Railway Forum

I thought I'd take a video of the converted Bachmann Lyn in action but she just doesn't have any pulling power. I thought it might have something to do with the batteries but after a recharge it was no different and even replacing the batteries completely makes no difference, so I suspect the Buhler motor has had it. I can stall the loco with one finger. All my other locos will protest amid much wheel spinning under similar circumstances.

Has anyone else experienced anything like this?

Any ideas where in the UK I might be able to get a replacement motor?

Rik

ge_rik wrote: ↑Mon Mar 01, 2021 1:28 pm

Any ideas where in the UK I might be able to get a replacement motor?

You could try these people they seem to be the UK agents for Buhler.
https://www.bancroft.co.uk/stock-motors.html

philipy wrote: ↑Mon Mar 01, 2021 1:55 pm

ge_rik wrote: ↑Mon Mar 01, 2021 1:28 pm

Any ideas where in the UK I might be able to get a replacement motor?

You could try these people they seem to be the UK agents for Buhler.
https://www.bancroft.co.uk/stock-motors.html

Thanks. Will investigate.
However, see next post......

Rik

I found this on the Bachmann.com forum

They are very poor runners, by my estimation. Geared way too high. They will not pull much and have no low speed power. Being geared so high they run like a scalded dog, overheat the motor, melt the motor mounts, and at that point end up on the rip track.

The motors have very large diameter brass worm gears. Bachmann's claim at the time they were introduced was that these heavier worm gears would act as flywheels. Maybe so, but they sure did not help locomotive performance.

The motor case is made in two halves, right and left. In order to get into the case the drivers must be pried from the nylon drive gears. Once that's done the case can be taken apart.

On balance, not a locomotive that would provide good service. It would be a shame to use a Lyn for a bash if its motor block was retained. All that work for a locomotive that won't pull much, melts its motor mounts, and is only comfortable at running at about Mach I.

So, it might just be a characteristic of the motor block. In which case, replacing the motor might make little difference. There is evidence of some overheating in the plastic of the clamshell housing so I wondered if the motor might have been cooked at some point.

Rik

Looks like there's some shared experiences on our forum - https://gardenrails.org/forum/viewtopic ... 4052#p4052

Rik

If the motor/block is as dodgy as it sounds, then would it be a better option to print a new housing to accomodate the motor/gears of your choice?

philipy wrote: ↑Mon Mar 01, 2021 3:33 pm If the motor/block is as dodgy as it sounds, then would it be a better option to print a new housing to accomodate the motor/gears of your choice?

Possibly..... However, the wheels are mounted on stub axles with a square profile designed to fit into a nylon moulding which includes the worm wheels. Not sure if I will be able to use them with a different type of gearbox arrangement.

Rik

Further to my previous posts - I've now tried another test run and discovered, curiously, that it runs better in reverse than going forwards. In reverse it's almost but not quite passable - but going forwards, skin and rice pudding springs to mind.

I've removed the motion to eliminate that as a possible cause.




Rik

ge_rik wrote: ↑Mon Mar 01, 2021 3:54 pm .... the wheels are mounted on stub axles with a square profile designed to fit into a nylon moulding which includes the worm wheels. Not sure if I will be able to use them with a different type of gearbox arrangement.

Here's that the insides look like

Might be tricky to mount the wheels - unless I can find a worm which meshes with the existing worm wheels

Rik

ge_rik wrote: ↑Tue Mar 02, 2021 12:09 pm Might be tricky to mount the wheels - unless I can find a worm which meshes with the existing worm wheels

Bachmann and quality control have only a fleeting acquaintance from what I've seen........

I'm told they use Mabuchi motors, but I'm inclined to think it will be a cheaper chinese clone. The clone makers use Mabuchi motor codes and there should be a code printed on it somewhere. Usually in the form XX-nnn. There may also be a suffix letter if it's a special voltage, etc. Unless someone has replaced the original, the chance of Bachmann using Buhler motors would be somewhere between zero and none.

You need to establish the gear pitch of the axle gears, it's probably a standard metric gear in the range 0.5MOD - 1MOD from the look of it. You'll find websites that can take you through the measurement process, then you can find a matching worm.

My inclination of course would be to build a steel outside frame with a motor/gearbox and bevel gear final drive, probably with Walsall wheels. It would outlast me, but I realise you don't have the machinery for something like that.

It would be worth seeing if you can print a plain axle with square sockets and if your printer is up to that job, use them with the Bachmann wheels, plus a better motor and gears and print your own motor block.

Regards,
Graeme

Hi Graeme
It says it's a Buhler motor - unless it's a clever clone.
Rik
PS - You can see from the bulge in the side of the motor block that the motor (or its predecessor) has, in the past, got somewhat warm......

Shame you don't have 32mm track as I am doing a FR Single Fairlie Taliesin next on my list, maybe you could just make a bogie to 45mm from my 32mm one, after all, it's only the width that would change? More room for stuff, lol.

Failing that, just make up your own complete drive unit from scratch, I assume the boiler area is hollow so you could fit a vertical motor?

As a non-engineering person I wonder whether it would be possible to remove the worm gears from the drive shaft, fit them to a new, longer shaft with an outside motor attached, assuming there is space within the loco body?

Thanks chaps. I think my next option is to design and 3d print a new housing for the motor block. If the worm wheels are standard size, then maybe a motor with smaller diameter worms might give more thrust. I'm hoping that assumption is valid. The most obvious difference between the Bachmann block and lgb blocks is the diameter of the worms and all my lgb blocks perform far batter than this one does.

Rik

ge_rik wrote: ↑Tue Mar 02, 2021 6:55 pm I think my next option is to design and 3d print a new housing for the motor block.

At the risk of teaching granny... ,if I were doing that I think I'd try to leave ventilation holes in the side plates, to allow for the motor gettinga bit warm?

ge_rik wrote: ↑Tue Mar 02, 2021 6:55 pm If the worm wheels are standard size, then maybe a motor with smaller diameter worms might give more thrust. I'm hoping that assumption is valid.

With worm gears, the gear ratio is dependent on the number of starts of the screw, not the diameter of the worm. E.g. a single start worm used with a 40 tooth worm wheel has a ratio 40:1, no matter the diameter of the worm. Most of the worms I've seen on models are single start, but I can't really tell if the ones on your motor block are single or multi start. If it is multi start, swapping the worms for same-diameter single start versions would increase the gear ratio, giving more torque and less speed.

Since most worms are single start, to get more torque your best bet is to increase the number of teeth on the worm wheel, but for simple arrangements where the worm wheel is on the same axle as the wheels, your number of teeth on the worm wheel is limited by the size of the wheels, otherwise the worm wheel can foul the track.

Have you tried the Bachmann spare parts page? A quick search gave me this...
https://estore.bachmanntrains.com/index ... 3vmdta3l11

I think I mentioned before that I used two of the motor blocks in my red Garratt with no problems. I bought them in 1997 but they were labelled as Spectrum types so may be better quality.

If you apply finger pressure to the loco, do the wheels spin or stall? From the video it seems to stall.

The different operation in forward and reverse MAY be due to 'slop' on the main drive shaft allowing the worm gear to be pushed to one end and bind. I had to put a small brass shim behind the worm to hold it in place.

Can you measure the armature resistance with your multimeter? It could help determine if the motor is damaged. Expect resistance to be around 4 or 5 ohms. I can measure mine if it helps. And measure the milliamps the motor takes when running with its wheels in the air.

And the obvious - how much does it weigh and is the weight over the drivers or unbalanced at one end?

metalmuncher wrote: ↑Tue Mar 02, 2021 7:56 pm

ge_rik wrote: ↑Tue Mar 02, 2021 6:55 pm If the worm wheels are standard size, then maybe a motor with smaller diameter worms might give more thrust. I'm hoping that assumption is valid.

With worm gears, the gear ratio is dependent on the number of starts of the screw, not the diameter of the worm. E.g. a single start worm used with a 40 tooth worm wheel has a ratio 40:1, no matter the diameter of the worm. Most of the worms I've seen on models are single start, but I can't really tell if the ones on your motor block are single or multi start. If it is multi start, swapping the worms for same-diameter single start versions would increase the gear ratio, giving more torque and less speed.

Since most worms are single start, to get more torque your best bet is to increase the number of teeth on the worm wheel, but for simple arrangements where the worm wheel is on the same axle as the wheels, your number of teeth on the worm wheel is limited by the size of the wheels, otherwise the worm wheel can foul the track.

I can see that I'd get the same reduction ratio regardless of the diameter of the worm, but how about the amount of thrust on each tooth. Say, for example, the worm was a metre in diameter. Wouldn't amount of effort needed to push each tooth be greater than if the worm was only 5mm in diameter - or will the amount of thrust remain the same? Sorry if I'm getting my forces terminology mixed up.

Rik

gregh wrote: ↑Wed Mar 03, 2021 5:45 am Have you tried the Bachmann spare parts page? A quick search gave me this...
https://estore.bachmanntrains.com/index ... 3vmdta3l11

I think I mentioned before that I used two of the motor blocks in my red Garratt with no problems. I bought them in 1997 but they were labelled as Spectrum types so may be better quality.

Thanks for this comprehensive reply Greg
I've now investigated the parts needed to replace the motor block. I'd also need a new wheel set as the gears on the new block are different. The total comes to £98 with shipping to the UK and I'd then need to pay 20% VAT so it would be nearly £120 overall. I think I'll see if there's a cheaper solution.

gregh wrote: ↑Wed Mar 03, 2021 5:45 am If you apply finger pressure to the loco, do the wheels spin or stall? From the video it seems to stall.

The different operation in forward and reverse MAY be due to 'slop' on the main drive shaft allowing the worm gear to be pushed to one end and bind. I had to put a small brass shim behind the worm to hold it in place.

Yes, I can stall the loco with finger pressure. Something which is very difficult with my other locos. I'm going to try playing around with the block in its half assembled state to see if I can spot any sloppiness or binding. I'll give it a jolly good degrease and cleanup as well.

gregh wrote: ↑Wed Mar 03, 2021 5:45 am Can you measure the armature resistance with your multimeter? It could help determine if the motor is damaged. Expect resistance to be around 4 or 5 ohms. I can measure mine if it helps. And measure the milliamps the motor takes when running with its wheels in the air.

Armature resistance is 6 ohms and it draws around 100 mA on tickover and around 180mA on full power with wheels in the air.

gregh wrote: ↑Wed Mar 03, 2021 5:45 am And the obvious - how much does it weigh and is the weight over the drivers or unbalanced at one end?

I've placed the original weights from the Lyn in the side tanks. Slightly biased towards the cab so I might try adding something to the front end as per the Lyn.


Rik

Well folks! Thanks very much for all your kind thoughts, suggestions and contributions - both in words and, in one case, in posting me a replacement motor - which I maybe won't need to use. I think I have identified the problem and fixed it (let's hope that's not famous last words!).

By cleaning everything up and then closely scrutinising all the bits I figured out that the motor which was installed in the motor block was actually a replacement to the original. The original mountings for the motor had been filed away and the corners of the motor had also been filed to clear the worm wheels.
BY watching carefully, I discovered the motor twisted slightly (by only a couple of mm) when under power. This was sufficient for the motor can to rub against one of the worm wheels. I inserted a self-tapping screw through the clamshell housing to engage with a slot in the side of the motor can. This seems to have done the trick. The loco now runs as well (or as badly) going forwards as it does in reverse.



My next task is to design and 3D print a bespoke clamshell housing which include lugs to hold the motor more securely. The plastic of the original housing is so brittle that all the pillars for the self-tapping screws holding it together have either split or completely disintegrated.

Many thanks again to all those who contributed to the deliberations in this thread. To my mind, this sort of discussion is what a forum like this is all about.

Rik