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Taking Leave

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Martin King 219/09/2020 17:57:24
717 forum posts
279 photos

Hi Andrew,

I heartily endorse Brian Woods comments above!

I really enjoy your threads and expertise as a complete newbie at all this stuff

Also many thanks for you know what!

Cheers, Martin

Oily Rag19/09/2020 18:30:23
161 forum posts
77 photos


I join in the praise given above for your depth of knowledge and experience. Your posts are always a delight to read being well written and concise. I shall be sorry not to read your valuable inputs in future. Get back when you feel the need after earning some wonga!

Stay safe and drop by every now and then.



noel shelley19/09/2020 19:01:26
116 forum posts

Andrew, as one of those who has been helped by your advice, firstly thankyou. As one who has to earn a living I drift in when time allows, then may not be seen for months. I hope you will be back, when you have time. Best wishes. Noel.

Andrew Johnston21/09/2020 11:55:37
5657 forum posts
653 photos

Thanks for the encouraging replies. I've also had some PMs and a couple of 'phone calls, in one of which I was smacked round the head and told to stop being an idiot. embarrassed

The plan is now to take a break and concentrate on the paid for work that is finally coming in. After that, like it or lump it, I'll be back. I will still be reading, and responding to, PMs. The timing may be slow though, as for reasons never explained I no longer get an email to say I have a PM waiting.

I'm not entirely abandoning the traction engines and other engineering. There are three main tasks upcoming:

1. Collect the set of wheels from the rubber tyre company and get the second engine on it's wheels.

2. Re-design the safety valves to be pop types.

3. Understand the maths and see if I can create a 3D CAD model of a spiral bevel gear. If I can model it then I will be able to 3D print and/or machine it.


Daniel21/09/2020 12:27:53
328 forum posts
48 photos

That sounds like a better plan Andrew. yes

gary21/09/2020 19:48:52
96 forum posts
28 photos

good on you andrew, i have been following your traction engine build for a while now

Meunier21/09/2020 20:57:38
352 forum posts
5 photos
Posted by Andrew Johnston on 21/09/2020 11:55:37:

......was smacked round the head and told to stop being an idiot. embarrassed .....
Please convey my appreciation to your somewhat blunt anonymous correspondent it or lump it, I'll be back....
good to hear, Arnie...

.....I'm not entirely abandoning the traction engines and other engineering.......
Sagas lose their impact if they peter out halfway


Andrew Johnston22/10/2020 23:48:29
5657 forum posts
653 photos

The astute reader may have noticed that I've been posting again today. Like it or lump it I intend to continue.

Regarding the tasks mentioned above I now have the wheels for my traction engine complete with rubber tyres:


I'm very pleased with the rubber tyres, less so with the rust from the vulcanisation process. I've got rid of a lot of it with wire wheels and a drill. But I've also bought a cheap blast gun and some garnet grit to get rid of the rest.

The safety valve design is on hold.

I now understand the basics of spiral bevel gears and also the difference between involute and octoid tooth forms. So it's now a case of modelling something I can 3D print and then machine.

A further distraction has occurred. Following discussions on the MEM forum I have found some old notes on the internet on the design of skew bevel gears. Of course I am aware of the work by Kozo. But I think his designs are based on hypoid gearing and the tooth profiles are significantly asymmetric. If one looks are drawings, and photographs, of the logging locomotives that used skew bevel gears the tooth forms are symmetric and look like straight tooth bevel gears. The design notes I have found use symmetric tooth profiles as per the full size engines. So I plan to model same in CAD and 3D print them to see if they work.

Talking of work I am now working for the first time in ten months and have been dragged into the 21st century with Zoom meetings for the first time this week. Work has to take priority as the savings are depleted. And we have a reputation with the client for delivering late so we absolutely have to deliver what we say, when we say this time. I am now delving into electrochemical gas sensors, potentiostats and transimpedance amplfiers, although given the large effective series capacitance in the sensor the output amplifier is more like a differentiator, complete with all its noise problems.


Ady122/10/2020 23:53:43
3859 forum posts
522 photos


Steviegtr23/10/2020 00:00:31
1487 forum posts
154 photos

I spent many years installing instruments in the Electro chemical industry. ICI . Lindsey oil & some chemical plant in Ince, Chester. No idea what they were, i just installed them.

Good to see you are still around. Chin up & get grafting.


gary23/10/2020 07:06:57
96 forum posts
28 photos

good to see you back, gary

Thor23/10/2020 08:06:19
1275 forum posts
39 photos

Andrew, I'm glad you are back and I am looking forward to reading your posts again.


Brian H23/10/2020 08:47:09
1794 forum posts
108 photos

Glad that you're back Andrew.


Bob Lamb23/10/2020 09:28:57
127 forum posts
34 photos

Andrew, I enjoy reading your posts and have learnt a lot from them. Present times are pretty crazy and may well get worse before Christmas - I think we may all be getting a bit fed up with things. I hope you will reconsider your decision - slow down a bit on the posts but don't leave us all without the benefit of your knowledge. Hope the work goes well and look forward to seeing some more posts at sometime in the future. All the best - Bob

Chris Evans 623/10/2020 09:32:36
1744 forum posts

A very warm and sincere welcome back Andrew. I always valued your knowledge and enjoyed reading your posts. Chris.

ChrisH23/10/2020 10:27:18
879 forum posts
29 photos

Welcome back Andrew!


Nicholas Farr23/10/2020 12:02:24
2438 forum posts
1193 photos

Hi Andrew, your rubber tyres look really good and the wheels are good also.

Regards Nick.

John Alexander Stewart23/10/2020 18:30:47
776 forum posts
52 photos


I seem to remember reading that the Climax gears were hand-made wood patterns, then cast. i.e. not machined.

Although having seen about 1/2 dozen of them, I can't say that I looked that closely! The other 2 (Shay, Heisler) are more interesting, IMHO.

Kozo gives us a way to machine gears good enough for his model Climax, machining on small machines in the average workshop, so I give him top marks.

Yes, it is good to see you back posting; hope the flying stuff is also going well. Cheers from Canada!

Andrew Johnston23/10/2020 21:47:51
5657 forum posts
653 photos

Thanks for the welcoming comments. Looks like I've made the right decision to return. As before I'll have a few informal rules about posting. Some electronics threads in the past got a bit heated, so I intend to generally stay clear of electronics. It's my profession, not my hobby, so I have an approach to design and debug which probably isn't appropriate here.

Inevitably in the current panic there have been a lot of posts recently about import machinery, the pros and cons and what are best buys. I've never used any import machines and know nothing about them, so I will be steering clear of such threads. That's not to say I won't comment on machining issues involving said machines; the cutting process is not machine dependent.


Steviegtr23/10/2020 21:54:59
1487 forum posts
154 photos

I am pretty much the same as you there Andrew. See lots of questions about eastern machines & never having owned or even used one, better just read the posts.


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