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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: Allchin slide valve help please
10/08/2013 17:38:23

Hi agian

For some reason some silly smilley face things have appeared in my post which when I edit the post I can't get rid of.

Not to worry, from bitter experience I pasted from note ad to avoid loosing everything and having to start again.

Thanks

Nigel

Edited By tractionengine42 on 10/08/2013 17:39:20

10/08/2013 17:31:37

Hi
I am building an Allchin at 3” scale and now trying to set up the slide valve but there seems to be some discrepancy, I would very much appreciate it if anyone can clarify whether I have some error.


Can anyone clarify the required width of the slide valve in relation to the inlet ports in the cylinder.

I have made everything to the 1.5" scale drawings (x2). Referring to the 3 staem ports milled in the cylinder, the outside dimension across the 2 inlet ports is 31.75mm. (1.25" )


The dimension across the slide valve is 40.48mm (1.59375" ) thus overlapping the inlet ports 4.365mm per side when the slide valve is in a central position.


However, the Allchin book says “Set the die block to the centre of the radial slot, and turn the flywheel slowly, watching the valve. At dead centre at each end, the edge of the inlet port should show a thin black line. In other words, it should be open to steam at either end just before the crank reaches dead centre.”


This indicates to me that the slide valve should be 31.75mm wide (less about 0.2mm) and not 40.48mm wide as per the drawings.


Am I missing something here, or do these very long established drawings really have such an error?


If the drawings are in error then this also questions what width the steam cavity on the underside of the slide valve should be in relation to the cylindre inlet/exhaust ports?


As this is the very first time I have built a steam cylinder valve arrangement I don’t have the experience to be sure what’s correct. I am in dis-belief that the drawings are wrong and sure there must be something I am not seeing.

Thanks for any guidance.

Nigel

Edited By tractionengine42 on 10/08/2013 17:32:30

Edited By tractionengine42 on 10/08/2013 17:33:39

Edited By JasonB on 10/08/2013 18:08:59

Thread: Trouble getting started
25/06/2013 23:37:03

I think the Warco VMC is worth a look as it's very versatile and has good capacity at a fairly low price.

I have been using this to build my 3" scale TE for which it has surplus capacity. I have not had any problem with my VMC, speed change is however, by changing the drive belts. I assume the major and GH machines you mention have variable speed which is an advantage.

These gears cut in one pass, 7.2mm depth, with no problem.

gear cutting

Nigel

Thread: CAM software for turning
28/04/2013 22:36:37

John, Thanks again for your feedback that's great to know, I couldn't see any reference to the turn wizards on the Artsoft website or tutorial video.

Nigel

28/04/2013 22:12:58
Posted by John Stevenson on 28/04/2013 01:38:04

I bought it and can't get any usable code out of it help was not very forthcoming.

John, thanks for your feed back, I will give it a miss then.

Paul,  we both appear to be in the same boat. From what I have looked at Dolphin turn is the only reasonably priced comprehensive lathe cam but for me still too expensive for hobby use.

I see Cambam, as suggested by Martin, has a lathe plug in for profile turning. For most jobs writing the g code should be easy enough to learn. I think this will be the way I will go, cambam + plug in for profiling and own gcode for everything else. I don't think mach 3 turn has wizards like the mill version does.

Like you I am also using Cut 2D for milling, maybe this could be used for generating gcode for a profile but then the gcode will need editing to adapt to turning. Hopfully others will comment on this.

Nigel

Edited By tractionengine42 on 28/04/2013 22:14:25

27/04/2013 23:39:51

Hi

I am also interested in a lathe conversion and I am thinking of giving the cad to lathe software a try. The training videos are not great but it does appear to be very usable hobby work at a low price.

Nigel

Thread: How to get started with CAD/CAM for machining and engraving?
09/04/2013 11:00:42

Hi

Meshcam may be worth a look, allot depends upon what cad formats you have available to put into your cam. Mesh can (and others) can create some 3d profiles from jpg images but I have not done this myself.

It's probably worth using free trial periods to try out different packages.

Nigel

09/04/2013 07:09:13

Hi Dave

I am no expert but for that type of work I think Martin has put you on the right track with Cambam, I am sure he will give you his comments. I have not used it so I am not qualified to recommend it.

Vectric 2D cut would not be suitable, my work is very much more mechanical than artistic. Vector 2D is good for profiling shapes, pocketing, drilling and engraving.

VCarve pro does look great but as you say pricey for hobby use.

I would be interested to hear what you finally decide and how you get on.

Nigel

Edited By tractionengine42 on 09/04/2013 07:10:52

09/04/2013 00:02:35

Hi Dave

For cad I use Draftsight and Creo Ellements both free.

For Cam I use Vectric Cut 2d and for 3d Meshcam both easy to use and very low cost.

This website might be of interest

I have not used them yet but Micropath and Microcarve may be useful.

These were done using Vectric 2D.

Allchin hub with correct engraving\

 

Allchin hose brackets

 

Nigel

Edited By tractionengine42 on 09/04/2013 00:10:53

Thread: Drill bit sharpener
22/03/2013 19:49:42

Hi

Here's a better price (Edit -  maybe not, you may have to pay import duty?)

You might be interested in this thread.

I think with many drill sharpening jigs you have to be patient in learning how to set them up to get good results. Once you get the hang of it it's a breeze.

Nigel

Some operating instructions here.

 

Edited By tractionengine42 on 22/03/2013 20:18:27

22/03/2013 09:55:18

Hi

I use the proxxon drill sharpener which I find works quite well.

However, there is a learning curve, you have to be patient learning to use it correctly, my first few attempts were terrible.

Once you learn to set up the drill correctly it's fine for drills 3mm to 8mm

Video here

Nigel

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

Nigel

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

Hi

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.

Nigel

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.

Nigel

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

Hi

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

.

Cheers

Nigel

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.

encoder.jpg

Cheers

Nigel

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.

 

Nigel

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.

Nigel

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.

Nigel

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

Neil

Niel

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.

Nigel

 

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

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