Contact Us!
  • White Facebook Icon
  • White YouTube Icon
Subscribe for updates!

Subscribe to receive email updates from time to time. Never miss a thing and unsubscribe whenever you like.

This website and forum is free to use. The vast majority of video content produced is available on youtube.

However, should you find Charlotte's Steam Clinic useful and if you fancy supporting this platform/content, you can become a Patreon for as little as $1 per month. There's no obligation, it's just a nice way to help out and to show appreciation for the time that goes into this platform. 


If you prefer to use PayPal or if you would like to make a stand alone donation (and not a monthly one) here's a link to our PayPal account. Thanks again if you make a donation. It makes a difference to us. 

© 2017 by Charlotte's Steam Clinic Proudly created by Visual Trailer Ltd.

Oct 10, 2017

Potty Mill Engine advice


I am building this engine from the plans available here :-


and would like some advice as to how to machine this component

It is the crankshaft and would appear to be turned from a piece of flat bar 18mm wide by 6mm thick. I have both lathe and milling machine but I don't fancy turning the main part of the shaft due to the interrupted cut. Should I mark it out and mill away most of the excess or just go for it?


Any and all advice gratefully received.




Oct 10, 2017


I will preface this input by saying that, like Keith, I am not a trained engineer. Just a person who is self-trained in sticking things together.


My first choice, based on the size of this model, would be to produce the crank as three pieces. Turning the bearing end and the main shaft from round stock on the lathe and the flat end on the milling machine.


It would require you change the drawing to place a hole in the side of the bearing end and the center of the flat plate along with turning a short extension to each end of the main shaft.


In assembling the three pieces you could use a press fit, silver solder or Loctite.

Oct 10, 2017

Thanks for the response and advice, Charlie.

I have considered doing it the way you describe ( I had thought about threading the small stub extensions to prevent on-load separation) but wanted confirmation that it was the sensible way to go.


This engine isn't supposed to be an accurate model of an existing engine - it's a free scale interpretation of a typical mill engine and so can use any construction method I suppose.


Thanks again

Oct 10, 2017

My only concern with threading the ends would be the clocking of the threads to get the two end pieces lined up. Come to think of it, Keith does the timing with various thickness of washers to ensure his fitting line up.

Oct 15, 2017

So, what have you decided to do and please post photos when you do it.

Oct 15, 2017

Well, I had a trial run and made a built up one - 3 pieces with the shaft socketed into the bearing and the plate.


Result? Horrible, in my opinion - I am ashamed to even post a picture of it. I tossed it to the back of the workbench and will probably try again tomorrow.


To be fair, the bearing part of it was semi OK but the whole thing just looked clumsy and disjointed.

Oct 16, 2017



Ive attached a picture of my connecting rod for my engine....i turned the center in the lathe, the interupted cut was not that connecting rod is a little different shape, but the concept is the same.. Once the center was turned, i then machined the rest on the mill. You can see more detail pictures of my engine on my website.


Nov 6, 2017Edited: Nov 6, 2017

In my humble opinion, I would start with a length of rectangle bar and turn the ”shaft” center section on a lathe. Then i would mark out the bearing hole and bore it out. Finally, I would fit a mandril through the bearing and chuck it up in a rotary table to turn the outside diameter of the bearing end on a mill.

PS The interupted cut is no big deal if you take it nice and slow until your part is completly round. It’ll come out real nice.

Hugh Coleman
Jun 16, 2018

I’d be making it from the rectangular bar as described by bencsly. you can drill and ream your big end and small end holes accurately first. intermittent cuts are unpleasant, but sometimes necessary.

New Posts
  • CastingIronEngines
    May 13

    I saw a photo of a green twin oscillating steam engine on the Preston Services website a few years ago, and a Canadian buddy of mine challenged me to make one. Long story short, I built a foundry, used a 3D modeling program to model the engine using 3 photos, made the patterns, and cast the parts for a 60% scale engine. I recently got the engine running, and it can be viewed here: The plan at this point is to finish the painting work on the engine, and publish it in Live Steam and Outdoor Railroading magazine. It was a long journey to learn the foundry work, but I was able to cast some of the parts in gray iron, with the remainder being cast in 356 aluminum.
  • J. Meaney
    May 28

    I recently acquired a Stuart Turner 3MTB stationary engine. Unfortunately the slide valve and ancillary parts are missing. does any have or know where I could get drawing of these parts. I have contacted Stuart Turner who no longer have any of the old drawings or parts. Below is a top view of the valve chest. Any assistance would be appreciated.
  • jatolton
    Sep 6, 2018

    Hello everyone... my name is Jason and I am from Northern Ontario. I recently purchased some steam engines from an estate sale and there is one that is rather interesting. It looks like a Stuart S50 model like right down to the nuts and bolt pattern on the valve cover.... although the crank web on mine is bell shaped where on the early Stuart S50 it is round. The people at Stuart in the UK think it is a 40's ish model based on the photos. I questioned mine because it does not have the Stuart nameplate on the top of the base... where it is located on engine. They sent me a picture of an old model without the Stuart sign on the top of the base but at the bottom instead. The people in the UK say that picture has the Stuart sign on it is photo shopped and there is really not one on it at all. On the pictures of my engine I have put a gold ring on where the Stuart sign is normally. I have never seen a knock-off anywhere online. Opinions are certainly appreciated. Stuart thinks I have the real deal.... and possibly a gem. Any thoughts on the engine? condition, authenticity, value? Thanks so much, Sincerely, Jason.