Garden Railway Forum

Hello!

As per my Chocolate Factory thread, I've just purchased a cheap train set with the intention of using power bogie underneath a model of a Sentinel loco.

Unfortunately I allowed my eagerness to dismantle the thing combine with my eagerness to test it - when the latter went a little awry I instinctively grabbed at the loco to snatch it from harm's way, forgetting that I'd started taking the bogie apart - so that stayed on the track, and one of the wires to the motor snapped off, as you can see in the picture:



What I need to do is to simply solder the wire back on, but I'm worried that actually it will be anything but simple... I'm really not much good at soldering, and so I'm concerned that as soon as I get the iron anywhere near the bogie the plastic that it's made from will start to melt. I've got form on that score, having melted several battery boxes while attempting to attach wires.

Does anyone have any suggestions as to the best technique to use?

Thanks in advance,

Andrew.

Can the motor be removed?

Otherwise, use a low wattage soldering iron (18 watt).

Agree with Tom, plus ensure that the end of the wire is well tinned before you try to solder it to the motor tag, especially if you do end up soldering it in situ. Plus of course you will need an iron that is physically small enough to get into that gap between motor body and plastic frame.

Andrew wrote: ↑Sat Dec 01, 2018 1:41 pm Does anyone have any suggestions as to the best technique to use?

It looks like the screw visible in the photo is all that is holding the motor in place, so the first thing to do is remove the motor so you have clear access to the solder tag on the motor. Don't try and solder in a confined space surrounded by plastic if at all possible.

The solder tag is already tinned which will make it easier to solder, so.....

- Strip and tin the end of the wire first.

- Use a decent size soldering iron, as you need to get in quick, melt the solder and get back out. If you pfaff about with an iron that is too small, or too small a tip, or a dirty tip, by the time the solder melts the plastic will too.

This is the bit where you need at least 3 hands.......

- Hold the tinned end of the wire in contact in contact with the tinned solder tag, melt a little blob of solder onto the tip of the iron and touch the tip of the iron to the joint. As soon as the solder penetrates the joint, pull the iron away and let it all cool before you move anything.

Don't press hard on the joint with the tip of the iron, as all it will achieve is melting the plastic and moving the tag.

You'll get someone that will say no-no you must put the iron on the joint and take the solder to the joint. Not a good idea when you are soldering a wire to a metal tag held in a block of plastic. Plastic melts at a lower temperature than electrical solder, by the time you make the joint the plastic has melted.......

The trick is to get in with a hot iron and get out again in the shortest possible time. As always with soldering, cleanliness is next to godliness.......

If you've got a dead motor in the scrapbox, or something with a similar solder tag through a block of plastic, practice with that until confident you can do it on the real motor.

Keeping everything in place without it moving is also a desirable state of affairs. Use clamps, tape, whatever works to keep the tinned wire end in close contact with the tab.

For this job, I'd clamp the motor in my little bench vise, with the solder reel close by. Hold the wire in a pair of tweezers, melt a little blob of solder onto the tip of the iron, touch it to the joint and Bob's your Mother's brother.

In my case of course the odds are I'd get a hand tremor just as the solder melts and have to start again. Sigh.......

I have a couple of soldering stations since they are now cheap enough for hobby use. For this sort of wiring job I use the 45W one with a 3mm chisel tip. I have smaller tips, but only use them for circuit board work, as they don't transfer heat fast enough for this sort of job.

Regards,
Graeme

Graeme to the rescue as usual!

What would we do without you

Excellent advice, thank you!

It does indeed look like the motor should come out by undoing the screw - I was so busy panicking about melting things that I'd overlooked the obvious...

If I get the time, I'll give it a shot tomorrow. I've got a variable temperature iron - would anyone care to suggest an appropriate heat setting?

Thanks again,

Andrew.

Andrew wrote: ↑Sat Dec 01, 2018 10:45 pm If I get the time, I'll give it a shot tomorrow. I've got a variable temperature iron - would anyone care to suggest an appropriate heat setting?

The view is different from 10,000 miles away..........

I set the soldering station to 270C for soldering wires together, but we can still get Sn/Pb solders here in Oz.

You may need a higher setting for lead free solders, if that's all you have.

Regards,
Graeme

I don't pretend to be an expert at soldering but have persevered over time to become competent enough to tackle most applications. In our scale there are so many opportunities to use solder instead of epoxy or other adhesives to create strong joins. Also, the electrical connections are many and varied and need to be made correctly. My advice would be to take two pieces of spare wire and 'tin' the ends, then practise soldering them together until you feel confident enough to tackle the motor connection. You will be surprised how useful this will be in the future.

Thanks chaps!

I didn't get time this weekend, but I'll let you know how I get on...

All the best,

Andrew.

Success!!! It ain't beautiful, but it works, and my big plastic battery engine is back in one piece and trundling round the table!

Many thanks for your advice,

Andrew.

Yay!

Well done Andrew, congratulations. Now you have started try another solder joint so that you have more confidence in the future, it will be a useful skill to have.

Good idea... It won't be straight away, but the Sentinel project will involve some more soldering... I find DPDT switches particularly difficult, but the loco's intended to run on a simple oval and only needs to run forwards, so for now at least I think I'll keep the child-friendly on/off button. I might try making modifications to the battery holder so that the loco runs on two cells instead of three to slow it down a bit, and it looks like the batteries will need to go in a separate van, so I'll need some sort of connection between the two...

Cheers,

Andrew.

Andrew wrote: ↑Tue Dec 04, 2018 8:16 pm It won't be straight away, but the Sentinel project will involve some more soldering...

What Peter said.......

Whenever you get a few minutes with nothing else to do solder a couple of wires together as practice. The joints don't have to be pretty, they just need to work.

When wiring, use as much pre-assembly as possible, so you can clamp things so they don't move as the joints are made.

Soldering is a basic skill needed for repair work as well as scratch building, you just need to practice and build your confidence. Even on non-powered rolling stock, I can't remember building a large scale model without some soldering in it somewhere.

Regards,
Graeme