Scratchbuilding locomotive drivers

[Guest Isambarduk]

I appreciate the input!

 

You are most welcome :-)

 

 

Is the crankpin press-fitted? And how did you hold the casting while machining?

 

The crankpin is a steel 12BA countersunk screw (screwed into a tapped hole from the back of the wheel), brass spacer, close-fitting brass top hat bush and a steel 12BA half-nut.

 

For the first machining operations (central hole and facing the rear boss), I held the casting in a four-jaw chuck.  For the subsequent operations, I mounted the wheel (face outwards) on an arbour and retained it with a nut screwed on the end of the arbour.

 

 

... do you know if the Birmingham caster you used are still in business?

 

It was a long time ago but, at the time, I had a friend and neighbour who is part of a 'well known' 4mm kit business and he took my pattern to the casters, along with a batch of their own.  I am sorry, I have no idea who the caster was or whether they are still aound.

 

David

[Hawk]

Long time no post, but I have not given up on my machining ambitions. Quite the contrary.

 

I have long been thinking about taking some machining classes, but as no such classes are available in my area I had to find an alternative. So I posted a wanted ad on a local Facebook group for a private tutor. And to my surprise I got a positive reply.

 

So a few nights ago I got my first machining lesson. It was almost a revelation to get the basics sorted out by a pro. What I learned this night will hopefully make a big difference on my future postings in this thread.

 

I have also changed the way I think about my lathe and machining. When I first bought the lathe I greatly underestimated the time it would take to acquire the skills to make parts with the quality I want.

 

But quite recently it struck me that buying a lathe is like buying a musical instrument like a guitar. You can not except to play beautiful melodies right after picking it up. You have to practice a lot, and taking lessons will speed up the learning process.

 

Before, I felt a little stupid after spending a couple of hours at the lathe and not having anything to show wifey but a brass disk with a pressed on steel rim.

 

If I had been practicing guitar for the same time, I would not have dreamt about making a recording of the session and let people listen to it!

 

But enough with the metaphors. If you are not prepared to spend a lot of time learning new skills, you should probably not buy a lathe. Spend the money on custom built parts instead. And If you are, find a way to try out a lathe for some hours. Don’t expect to produce something useful, the point is to find out if you enjoyed the time spent on the machine.

 

By the way, the going rate for a machining tutor in my area seems to be a bottle of decent red wine and a vinyl Frank Sinatra record!

[PaulCheffus]

Before, I felt a little stupid after spending a couple of hours at the lathe and not having anything to show wifey but a brass disk with a pressed on steel rim.If I had been practicing guitar for the same time,

Hi

 

I know what you mean, I bought a lathe and milling machine last August and until recently I had spent hours with it but had nothing to show for the time. However I learnt quite a lot about what my machines can and can't do. Finally at the end of last month I managed to finish the chuck key for my four jaw chuck (it came with just an Allen key as a chuck key)

 

Cheers

 

Paul

[Guest Isambarduk]

I have also changed the way I think about my lathe and machining.

 

The thing is, and I though that this is what you were going to say, owning and using machine tools is a pure joy in itself. 

 

Over the years (well, it's been several decades, now), I have most definitely found that the 'journey' of making parts for a model is every bit as much pleasure as the 'final arrival' of a completed model. 

 

David

[Hawk]

The thing is, and I though that this is what you were going to say, owning and using machine tools is a pure joy in itself. 

 

Over the years (well, it's been several decades, now), I have most definitely found that the 'journey' of making parts for a model is every bit as much pleasure as the 'final arrival' of a completed model. 

 

David

I am not quite ready to label the time spent with my lathe as a "pure joy". The learning curve has at times been so steep that I almost gave up. But I am more optimistic than ever. Maybe I in a couple of months will reach the pure joy stage!

 

I fully agree that the journey is a destination in itself. But It is extremely pleasing to have completed at least two scratch built engines and a handful of wagons.

[MarshLane]

Fascinating post Hauk,

 

Do keep up with the posts, as and when you progress.  I would love to know how to use to a lathe!  Not something I've dabbled in at all, but perhaps the interest is growing slowly (very slowly!)

 

Rich

[Hawk]

Besides trying to make wheels for my engines, I am also working on some wheelsets for wagons and railcars. 

These are also spoked wheels, and  I felt that it might be worth trying to 3D-print the wheel centers. 

 

So I had some centers printed in Detailed Plastic by Shapeways.  They are oversize by 0.2mm on all surfaces that are going to be machined:

 

 

They machine easily, and for an amateur machinist like me, it i far easier to obtain exact dimensions in plastic than in metal. 

 

 

I opted for a press fit that needs very little force. I am quite concerned about breaking the plastic. The plan is to use ACC  between the centres and the rings. If there are glues more suited for the purpose, please let me know!

 

 

It is hard to know if the 3D printed centres are strong enough for light 0-scale equipment, but it feels OK. If anyone have tried something similiar, chime in! How the Shapeways plastic stands up in time might also bee an issue.  I think I have read somewhere that some people have problems with old 3D prints. 

 

Comments? Tried something similiar? 

 

Edited August 11, 2023 by Hawk

[brack]

I made some 7mm scale bagnall 1'3" driving wheel centres in FUD to fit tyres off kbscale wheels. They seemed to come out fine, though mine aren't machined like yours.

I used super glue to fit the tyres. They seem to roll fine when mounted on axles, but kids/house have intervened and I've not actually put them into a mechanism yet.

Certainly i think they should be strong enough, especially with spokes spreading the load.

I can dig out a photo, or even the wheels themselves and take a new photo if you like?

 

(Bear in mind you model to a significantly higher standard than i)

[brack]

I had to go upstairs for something else, so here you go:

 

The wheels must be 3-4 years old now. Seem fine.

Edited June 23, 2019 by brack

[Hawk]

4 hours ago, brack said:

The wheels must be 3-4 years old now. Seem fine.

 

I think that one should be careful about the solvents you use for cleaning the parts. Again, I do not remember the original source but there are solvents that can make this type of plastic go brittle.

[brack]

FUD is always fairly brittle to start with. I generally use white spirit or isopropyl alcohol to wash prints at first, but I've 3d printed locos in this material from 2013 which are still fine. I usually fill and sand (if needed) then coat with klear, primer, paint and Matt varnish.

 

One day I'll build the chassis these wheels are for...

[Hawk]

Just a little bump of the thread to show the finished wheel, and to say that all earlier images in this thread has been reinserted. 

Hopefully, everybody will now be able to see them!

 

Edited August 11, 2023 by Hawk