Author Topic: Motor choice  (Read 4687 times)

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Offline IanT

Re: Motor choice
« Reply #45 on: Feb 14 2021 11:19 »
Lovely work Nick.

Regards,

IanT
Nothing's ever Easy - At least the first time around.

Offline 753

Re: Motor choice
« Reply #46 on: Feb 14 2021 11:28 »
Nick

Your engine is looking superb, could you describe in more detail your methods of creating the curve of domes and safety valve covers to sit on the boiler.

I turn up a large thin over size flange at the base of a dome, then anneal and dress down the flange over a round former the same dia as the boiler, then return to the lathe and turn to size.

Mike

Offline Nick

Re: Motor choice
« Reply #47 on: Feb 15 2021 20:25 »
Thank you both for your kind words.

To create the flare, I first flycut the base of the workpiece to the correct diameter for the boiler or smokebox, and drill and tap it for an arbour. It then goes on to the gizmo you can see in the photo. As it is rotated, the base runs on a peg that is hidden between the vice jaws, so that the cutter path follows the profile of the base. I gradually take off as much material as I can with a ballnose cutter. The finish is terrible because it is impossible to stop the workpiece chattering. I strengthened the spring shown in the photo considerably and pushed on the end of the dome with my thumb but still couldn't hold it completely steady. But that doesn't matter because the final task is to file it by hand to the final shape - checking the profiles frequently.





I've heard about people using Mike's method, or some variant of it, but I'm not sure it would work for me because I'm not that confident about my abilities with a hammer. I would have to practice on a few pieces to start with. For me, modern technology will be the way to go. I enjoy using traditional methods but not to the point of making a fetish of them.

Nick

Offline IanT

Re: Motor choice
« Reply #48 on: Feb 15 2021 22:25 »
Very ingenious Nick - thank you for sharing the idea.

Regards,

IanT
Nothing's ever Easy - At least the first time around.

Offline 753

Re: Motor choice
« Reply #49 on: Feb 16 2021 09:58 »
Nick
Thank you for the explanation, I agree with Ian’s comment. I note you are using steel which is harder than brass, maybe that might machine better.

The method I described in my post the brass is annealed thus easier to work. I have a piece of square copper with rounded end that I dress the flare over the form thus not damaging the surface of the metal.

I find it fascinating how we find different solutions to overcome problems that come up building engines.

Mike

Offline Nick

Re: Motor choice
« Reply #50 on: Feb 17 2021 20:24 »
Quote
I note you are using steel

Only because it is what was to hand, and because it will be painted. The South Western, unlike some railways, didn't go in for polished brass or copper bonnets (thankfully). I agree, brass might cut down the machining time.

Quote
I find it fascinating how we find different solutions to overcome problems that come up building engines.

I couldn't agree more! It's what a forum is (or should be) all about.

Nick

Offline Nick

Re: Motor choice
« Reply #51 on: Feb 25 2021 10:40 »
The backhead is another component with interesting curves. Previously I had cut them from plate and filed the radius. This time I thought I would try a corner radius cutter. The workpiece was clamped to a plate drilled at the centres of three arcs: the top section of the backplate and the two fillets between that and the parallel section downwards. Each arc was cut in turn on using a rotary table, the fillets first and then the top to join them.

The finish left by the cutter wasn't bad, good enough that it was only a few minutes work with a file to smooth it all off. Result: a very consistent corner radius and a considerable time saving.

Nick






Offline Nick

Re: Motor choice
« Reply #52 on: Mar 31 2021 20:34 »
I'm waiting for the next batch of fittings to finish the cab and backhead.





In the meantime I started drawing the tender and turning the tender wheels.





The drawing isn't just for fun, I'm getting a lot of the parts made and so I had to draw them anyway. After that assembling them is not a whole lot more effort, and I find it helps me to work out the assembly.

The well tank is prototypical and by including it I figured that I could get a pack of 10 C-cells in the tender if I decided or discovered I needed the battery capacity. My original idea was to put them in the loco but I found I could only get a pack of AA batteries in there. It means a more weight in the tender for the loco to pull around, but with the motor between the frames, I can fill the firebox with scrap iron and get a lot of tractive weight on the driving wheels.





The tender wheels, like the loco wheels, are Mark Wood castings (only had a year to wait for them!) and very nice they are too. Fine grain cast iron, no hard skin or inclusions, they turn up very well with only the inevitable graphite dust to contend with.

Nick