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Member postings for tractionengine42

Here is a list of all the postings tractionengine42 has made in our forums. Click on a thread name to jump to the thread.

Thread: Enthusiasm
02/02/2013 05:24:25

Can't put a single number to it.

Level of interest and priority is high, time available is short.

Level of expenditure shows commitment but output does not justify it, the only justification is pleasure.

Amount of available time spent on Model Engineering extremely variable.

An accumulation of Model Engineering interests has lead to a large collection of 'under the bench projects' waiting their turn.

It will be completed 5 to 10 years later than expected.

Hmmm, I have heard of business models, maybe I need a hobby model?wink 2


Thread: Peep Price
19/11/2012 14:27:15


I actually have a similar problem when on this forum. Words in posts are shown highlighted in blue as though they are links put in by the person making the post. When you hover your cursor over or click it an add appears. I have supposedly won god knows how many iphones and other stuff.

So frustratingly annoying, I thought Norton was supposed to get rid of this kind of stuff. This thread alone has several false links.


Thread: Mach 3 Training
06/11/2012 14:25:09

Hi John/Russell

The link has also stopped working for me, I get a 'Forbidden' message.

It was fine a few days ago.


Thread: Encoder - How to build one?
05/11/2012 04:11:30


Jason, thanks for your post, very helpful information.

Neil, I am asking around for an old mouse so I can have a look. I am finding this very interesting but still a little confusing.

This is my latest encoder disc now at 63.5mm dia. with 100 - 0.5mm slots. Material between slots is nominally 1.5mm wide. So to get 2000 pulses I would have to gear it up 5:1.

Am I correct in thinking that so long as I place one photo switch in the centre of a slot and the other in the centre of the material between the slot I will be OK?

encoder 2.jpg


I thought this photo switch might be OK.

photo switch.jpg




Edited By tractionengine42 on 05/11/2012 04:12:26

02/11/2012 14:26:48

Thanks Michael and Michael, very helpful info.

I now understand the quadrature issue much better and how to place the photo switches.

I am busy sourcing the parts, some of the Farnell part no.s don't exist any more so I am having to source alternatives, great funfrown.

I am thinking of making the encoder disc with 3mm slots and using the photo switches specified by John S in the thread previously referenced. With 3mm between slots the disc come out at 107mm. I think this is manageable, 2mm slots would be better, I presume it depends upon the switches. I would rather play it safe and not get to fiddley.




02/11/2012 05:29:32

Hi everyone,

I am very interested in building an electronic gear box as referred to in MEW issue 108 and noted in this post.

An encoder is needed but these look quite expensive to purchase, so I would also be interested in building one of these as well. There is some good info and photo in this thread.

The electronic gear box circuit in issue 108 requires a phase A and phase B input from the encoder at 2000 pulses per rev of the gear hob.

My question is how do I set up to get these phase A and phase B inputs?

I have seen "quadrature" mentioned, but how does this work?

I think the following will be the case but I am not 100% sure.

1. If I can make a 50 slot encoder disc (to keep the diameter a reasonable size).

2. Then have 2 photo electric switches to give phase A and phase B inputs.

3. Then arrange these switches so that one is set to switch at the leading edge of a slot (Phase A) and, at exactly the same time, the other set to switch at the trailing edge of a slot. (phase B) (I am very unclear on this point an how this gives the "quadrature".

4. So with 50 slots and quadrature I get 200 impulses per rev of the gear hob?

5. So to get 2000 impulses I need to gear up the encoder disc by 10 x the gear hob speed?

My knowledge of electronics is extremely limited, any pointers in the right direction will be very much appreciated.



Edited By tractionengine42 on 02/11/2012 05:30:44

Thread: Electronic gearbox for gear hobbing.
31/10/2012 21:53:48

MEW issue 193 has a gear hobbing article for a mill using an electronic sync.


Thread: 1/4HP bench drill modification-slow speed
29/10/2012 14:30:15

Last week I had the pleasure of visiting Steve's workshop, full of economically innovative machine tool improvements and accessories.

Very high level of craftsman ship, many larger parts are fashioned entirely with hand tools requiring much patients.

Steve, thanks for an interesting and informative visit. I am looking forward to seeing the Aciera progress over the coming months.


Thread: Boiler Calculations
27/10/2012 10:35:52
Posted by Stub Mandrel on 26/10/2012 20:20:13:

I have a 2 5/8" seamless copper boiler tube, 0.041" thick.

Using Tubal Cain's formula thickness=pressure x diameter/2xUTS for a seamless tube

Safety factors are built in to the above



I concur with what Eddie has said.

The formula you give is from the standard formula for hoop stress in thin cylinders where stress = (pressure x shell radius) / shell thickness.

I was very surprised see UTS in your formula.

Using UTS does not provide any safety margin and to my way of thinking is more akin to burst pressures calculations.

As Eddie indicates, the safety margin is in what you use as your design stress, so thickness = working pressure x dia / 2 x design stress.

For example, pressure vessel codes typically use a design stress equal to material yield stress/1.5 for steel at ambient temperatures.

To check under hydrostatic test, you could use your test pressure and design stress of say 90% yield stress for steel. Eddie indicates that for copper a stress of 5000 psi would be suitable to use at your test pressure.

Unless there is something in Tubal Cain's book I am missing. hope my ramblings help.



Edited By tractionengine42 on 27/10/2012 10:38:51

Thread: Painting Brass
26/10/2012 13:55:11

Rather than using an etch primer you could try Polyester Spray Filler as a base which I think sticks to almost anything (after the part has had a good degraese and clean), it's like a body filler that you spray on. Some can be thinned depending on the brand. Like body filler it has a resin and hardener.

After it has dried rub it down and apply a primer (but not etch primer) ready for painting.

It's used on machine castings, car restoration and the like.

Normally it has a limited shelf life and not cheap. May not be good on fine detailed models unless you can thin it right down, other wise it will fill in the detail.



Edited By tractionengine42 on 26/10/2012 13:58:19

Thread: Filling holes
25/10/2012 01:52:34

As Michael says, because the thread pitch of M5 and 3/16 BSF are in essence the same, the M5 being 0.24mm larger in diameter, then you should be able to true it up to M5 if you guide the drill & tap perpendicular to the surface and get a good thread.

Personally I would tap M5 or M6 and use M5 or M6 bolts.

Another alternative is, if the design will accommodate a stud and nut arrangement rather than a bolt and threaded hole, then you can tap the hole M6 and make a stud M6 one side and M5 the other.


Thread: Piston Ring Material?
23/10/2012 01:59:52

Hi Don

Cast iron piston rings working with cast iron cylinders is probably the most commonly used combination for your type of application. I would recommend going for a good quality material like a grade 17 continually cast which has a very fine grain and uniform structure. I used this combination on my BR2 without any problem.

Because of it's free graphite content cast iron has the rare property of being a good bearing material with it's self, not so with most other materials.

Steel piston rings may be OK but I have no experience in this quarter.


Thread: Self adulation
17/10/2012 15:24:58

Reminds me of my own model engineering desires at 16 years, having just started work and decided a Myford would never be in my reach I suggested that, if I did not pay my board for a few weeks, I could afford to buy a Unimat lathe. lol. I would pay it back later. lol.

Taken to one side and given "when I were your age lad" treatment followed by the real facts of economic life, it wasn't to be, not for some time anyway.

Good luck to Alistair, he sounds very capable, not many his age dream of a career building and repairing steam engines.


Thread: Steel Tender Waterproofing
15/10/2012 01:57:36

I asked the same question to some guys with miniatures at a steam rally, I did as they recommended, light shot blast and then coated with isoflex liquid rubber. They said they had not had any problem over several years.


Thread: The Greatest Mechanical invention
10/10/2012 13:14:48

The crank shaft, without which your wonderful reciprocating engines would have limited use and the industrial revolution may not have happened.


Thread: Boiler Design
10/10/2012 06:01:56

Hi Phil

No offence taken, FEA is not really for the amateur environment. A simple method that can be used by the armature would be the way to go.

If a simple method could be devised then FEA could be used to help prove it, once verified no further FEA would be needed by the user. Just a thought.

When I was doing those FEA's in my photo's I did think about devising some simple formula myself and using the FEA to prove the ideas, I think, for me anyway, this would be an interesting exercise. Other interests and work make this a low priority though.

Looking forward to hearing your progress.


09/10/2012 14:46:35

Hi Phil

If it's acceptable to your boiler inspector I can do an FEA design check of your design, if it helps.

See my photo's

Don't wait to long as I won't have the facility indefinitely.


Thread: Tool and Cutter Grinder
09/10/2012 02:47:39

Unless your into building workshop equipment rather than models, I would not go down the route of anything sophisticated.

You can't go wrong with Harold's solution, simple, easy to build, quick and economical.


Thread: Needle flame gas torch
09/10/2012 02:00:13


The flame fast torch is 130 GBP +vat

The portaflame kit (regulator) is 88 GBP + Vat

By the time you add the postage and the vat it's 270.6 GBP. 45.10 GBP vat is a killer

I could get a needle flame propane oxy kit for less than 50 gbp + purchase of a 9L oxygen cylinder & gas for less than 100 GBP.

Thanks to Neil's post showing the old ME article I am inspired to have a go at building one.


08/10/2012 15:18:10


Some fascinating air brushes there.

Hmmm..... Now you've got me thinking.



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