Alibre - Have Taken The Plunge

The Trial Licence expired yesterday. I purchased the full copy today - which sparked a thumping great update and "Repair" (repair?) process.

Once it had settled down and made itself at home I went on and completed trying to draw my steam-lorry's cylinder block as it presently is. I think I have the LP ports off-centre, and some of the dimensions are a bit approximate.

The holes around the ports are for M5 studs, drawn at ~5mm (actually 0.2mm) diameter.

The idea is that a 3/8" thick steel plate will cover top and bottom of the cast-iron block, with holes through those plates to locate the cylinder covers themselves. Much of the sides will be cut back to lighten the thing, with that concealed under a lagging sheet. The photograph I have suggests the entire lump on the original - valve-chests and all - was a single, rectangular casting with no obvious cladding.

This shows the problems I have built in: stud-holes hitting the drilled passages, very narrow lands at the ends for sealing the cover-plates, the LP exhaust passage nearly breaking out of the metal at its entrance although it is actually tapered inwards in steps (by step-drill). Studs too numerous, giving no room for the steam inlets to the valve-chests.

It also shows where I didn't get the drawing process quite right!

Thank you all for the help and encouragement to get started.

Ironically, today's clutch of e-posts included an ad for TurboCAD 2023! No I won't be buying that as well.

Good for you

I can 99.9% guarantee you won't regret it

It's actually quite addictive once you get comfortable with it, a video game that yields positive results

Does that represent the actual stage the cylinder block is currently at?

As for drawing it you have done quite well, Main thing that I would say is that the initial rectangle you sketched would have been better if it were symmetrical about the mid point then bores become easier to place and hole patterns easier to mirror so less work positioning individual holes. It's something that comes with time as you get more used to how things work out.

Nigel - is that just an unfortunate phrasing / typographic error, or are you modelling the features at scale, rather than at actual size?

It is usual practice to model everything at actual size, then let the software take care of producing scaled views in any 2D drawings.

Use of section views in the model, or setting the part semi transparent, can be really helpful to see where holes get too close for comfort.

It's just practice practice practice from now on and so your experience grows

I run 2 to 4 projects at the same time, if you get tired with one then you go and do another, and they all build your knowledge and confidence in different ways. Then you experiment with the software, trying different approaches to the same problems

And unlike with our workshops everything gets completed!

The best bit is learning stuff can still be fun

Thankyou Jason!

Yes - I drew the block from measuring it on a table alongside the computer.

It's not quite right. I think some of the dimensions on the drawing are a bit out.

The block is not fully symmetrical. The centre-lines of the bores are at different distances from the port-faces, though the ports are symmetrical to the depth of the block. Also the two stud-holes at each end of the port face are spaced slightly towards the sides to allow some room for the valve-spindle and its bush and gland.

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Sorry - I'm not sure how you make something symmetrical as you say. I had turned the Grid and Grid Snap off as advised, and that makes the starting rectangle aligned with the grid but not the big dot in the middle. So had to place everything by dimensions from the edges.

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I found how to use the array tool to make the rows of passages and the longer rows of stud holes. Ideally the drilled passages should slope down through the block for more sealing area, more room for fastenings, and minimum clearance volume.... but I'd made it the safest way I could at the time, and drew it as I'd made it.

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I drew it after a lot of trial-and-error as a half-depth block in which to cut the two recesses that on assembly would form parts of the steam-passages. Then mirrored that, before cutting the two bores.

However, I found it very hard to calculate the sizes of the cutting rectangles for the HP side, leading first to biting into the block on both sides of the cylinder, then landing short so I had to take a second extruded cut at it. I think this is why the drillings on that side bite into the port wall. I could not make the holes tangential to the right edge, due to having two slightly overlapping sketches.

I tried to remove the faulty sketch lines but couldn't, so how do I do that?

..

It was also difficult to make the passages meet the ports, mainly by mis-measuring but I was not sure if the cutting depth was from the block surface or recess floor of the recess. In hindsight I ought perhaps have done this:

- Form the half-block, on the XY plane.

- Cut the outer port and all the passage drillings into them at each end.

- Cut the passage recess.

- Now mirror-copy the block to itself (to the XY plane.

- Cut the bores and on the crank-end face, their registers. (I have made the bottom closing plate, a rectangle in 3/8" thick steel, using a rotary-table to create the two shallow upstands that engage these registers.)

- To each end in turn, add the exhaust-port and its stud pattern.

- Add the crank-end cylinder registers.

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It would seem to use CAD efficiently without mistakes hard to put right, needs planning the drawing order, often but not necessarily always the physical making order.

The reason for now drawing the cylinders formally is to try to deign modifications that will overcome the built-in problems I did not or could not foresee. Short of buying a new lump of iron completely......

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One of my hopes by using CAD is that I can make copies on which to experiment. There are no full-size drawings to help me. The cylinders are also very prominent, In full-size they were between and slightly behind the driver's and mate's shoulders.and I am trying to represent fairly from a few old publicity photographs, something impossible to model to rivet-counting standards.

What I think are the starting-valve and its handle, are also prominent, on the back of the HP valve-chest. It must have been very awkward to operate there, while having also to use a globe-valve regulator - oh, and steer the wagon.

This valve and its associated passages are also something to accommodate. Helped by the overall slab-like appearance of the whole assembly. I think I can cut deep lightening recesses in the block, in which to install the passages as pipe fabrications, concealed under cladding. The starting-valve itself, if I have identified it as that correctly, is exposed.

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Besides, the photos all show the originals differing in details. Hindleys built a large number of engineering products in a wide range to good designs and quality, some now preserved; but their steam-wagons were perhaps not among these. Compared to their contemporaries from the major makers, they were rather crude even for their time. The largest fleet was probably that owned by Pickfords, but for reasons I don't know, the haulier and furniture-remover went over to using Foden wagons; a big blow to the North Dorset manufacturer.

One Hindley steam-wagon was bought by C.W. Harris, an engineering firm in Chewton Mendip, near Bristol. Harris made petrol motor-cars under the "Mendip" brand; but also introduced a steam-wagon badged "Mendip" and looking very suspiciously Hindley....

You can enable the measuring tool by highlighting an edge etc and right clicking, its at the bottom of the menu

if you click on a sketch line you should get the small menu that has a delete button, you must go to that sketch first though, you cannot delete a line in sketch 1 if you are in sketch2

Edited By Ady1 on 18/05/2023 09:53:15

Nice to see you getting to grips with Alibre Nigel. Your posts sparked a lot of interest!

I was you Nigel I would build a couple of full plans first to get more experience at using the Alibre software

Old Model Engineer Magazine plans, or full plans downloaded from the netty, nothing too ambitious, but you must get those finished first before moving on

At the moment you are trying to learn Alibre while designing a completely new project at the same time which is a bit of a step too far IMO

You need to do a couple of completions first

get them under your belt before moving on to the Barnes Wallis stage

Edited By Ady1 on 18/05/2023 10:24:12

Posted by Nigel Graham 2 on 18/05/2023 09:36:00:

Sorry - I'm not sure how you make something symmetrical as you say. I had turned the Grid and Grid Snap off as advised, and that makes the starting rectangle aligned with the grid but not the big dot in the middle. So had to place everything by dimensions from the edges.

You can use dimensions, but more effective is to use a symmetry constraint in the sketch

However, I found it very hard to calculate the sizes of the cutting rectangles for the HP side, leading first to biting into the block on both sides of the cylinder, then landing short so I had to take a second extruded cut at it. I think this is why the drillings on that side bite into the port wall. I could not make the holes tangential to the right edge, due to having two slightly overlapping sketches.

Rather than take second extrude cut, edit the sketch or depth for the first one to change its size.

If overlapping sketches is confusing - Toggle Sketches off on View Tab of the Ribbon. Then you'll only see the sketch that you are currently editing.

I tried to remove the faulty sketch lines but couldn't, so how do I do that?

Edit the sketch containing the lines, select line or lines, then either press Delete key on keyboard, or click the Delete symbol on the pop up window. Alternatively, right click the line, and select Delete from the context menu.

It would seem to use CAD efficiently without mistakes hard to put right, needs planning the drawing order, often but not necessarily always the physical making order.

There is an element of that. Also be aware that if you get the order 'wrong', it is possible to move items around in the Design Explorer to change the order afterwards. If you do that always press F5 to regenerate the part as this should highlight any failures that the change of order has lead to. Because features are built each one 'on top of' earlier features, changing the execution order can lead to problems, so proceed with caution.

Edited By David Jupp on 18/05/2023 10:11:01

David has covered the symmetry tool which I show being used to position the first rectangle. I also have the option of making a rectangle that starts at a ctr point but not sure if Atom has that, used for the initial port rectangle.

Another way to remove lines etc from a sketch is to use "trim" you can see me doing that.You can see me doing that where I muck up the steam passage drillings and start again with smaller holes

You will see throughout that I use mirror a lot so that initial placement of the axis saves a lot of time later.

Getting your passage holes to meet the ports, you don't just have to set a length, you can select geometry for where a cut or solid boss will extend to, I use that for the drilled holes setting the edge of the port as where they go to

I just used random sizes so the stud holes look a bit big (I tend to draw tapped holes at their tapping side which may be your typo as 4.2mm would be what I usually use.

Personally (and this is largely preference), I would have used feature pattern instead of sketch pattern for the steam drillings. That way only one circle to edit the size of to re-size hole - and if you actually intended the holes to touch or overlap, you can because the sketch won't have any overlaps.

There are usually several different options possible for any particular modelling task.

Edited By David Jupp on 18/05/2023 10:51:37

Nigel, now that you're working your way around how the interface works, it's time to remember that you shouldn't be calculating anything. Leave that to the program, and tell it where you want the cut to go to: an edge, face, bore centre, plane, whatever. Things like bolt holes should be done using the relevant tool that already has the data, and can be edited or shared later. Although this contrary to traditional methods, it makes the design work - the important bit that the computer can't do for you - so much easier.

Ady's advice to model an existing design or assembly you understand is excellent, and will save you a lot of time and frustration in the long run.

Finally, you wouldn't make a usable 2D drawing without some thought, planning and probably some simple sketches so why would 3D modelling be any different?

Well done Nigel. My perception in this thread is you're very close to getting past the difficult bit, which is getting going in the first place. I had a difficult time starting too, but after the basics clicked in my mind, I made rapid progress.

I suspect most failures to self-learn CAD fail in the early stages, and having a mentor on hand would quickly overcome that. If only! The alternatives are inferior. Though they've answered a lot of questions, I find it hard to follow blurry videos. Tutorials with screen-shots are better, but they don't help beginners get past subtle misapprehensions - things like accidentally snapping to the wrong point. Reference Manuals aren't teaching aids.

AI could be the answer: software provided with CAD that's learned the rules and makes human-level sensible suggestions whilst the learner explores the software and follows exercises. AI could, for example, spot missed steps and incorrect clicking immediately during an exercise, just as a human expert would. Unlike CAD software itself, which can't tell the difference between a beginner going off the rails and an expert developing a complex part.

Dave

Nigel really needs to complete a couple of plans before he starts designing any brand new stuff

Nigel,

There will come a time when you will want to include in your designs a proprietary part such as a flanged nut or similar. Rather than draw it from scratch, it is much quicker to import a ready-made part from an outside source. Atom has a link to Traceparts Library in the add-ons section of the Utilities tab. I have used this facility, but it requires registering an account which I know you would be reluctant to do. However, I watched a video on YouTube the other evening by James Clough (Clough42) in which he designed a grinding wheel balancing device (2 actually) and he downloaded the ceramic bearing CAD files for one design from McMaster-Carr. I tried a few downloads myself from there and was pleasantly surprised by the sheer amount, quality and variety of examples available. It doesn't support Alibre files directly, so I chose to download them as STEP files which Atom handles and displays correctly.

Apologies if you already know about this but I'd not come across it myself, so thought I'd share it.

John

Edited By John Hinkley on 18/05/2023 19:56:32

Thank you chaps.

Ady -

I am not trying to be as ambitious as you think! The cylinder-block is a drawing of one existing in the iron, so to speak. I used it as much as an exercise as anything, by measuring it with a rule and vernier caliper. It is simply a collection or extruded rectangles and circles, no more advanced than the tutorial exercises though with a couple of moves not in them.

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Nick -

The calculating was not something that would normally be left to the computer but were in the physical measurements of the item, so I could enter the right dimensions in the drawing. It was particularly in working out the spacing for those rows of holes.

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David -

For the rows of holes: Feature Pattern in the model rather than sketch? I explored both. I think I "drilled" the passages in Model mode but the stud holes in Sketch.

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Jason -

Just stopped to watch your video. Ah, I see what you mean about establishing its symmetry. And using the Mirror tool a lot.

When I set out the stud holes I drew reference lines as their centre-lines for the corner holes, and put the circles on their intersections; but used arrays to add the rest. That was the tricky bit because I was trying to work out exactly what values to type in, and it took me a lot of experimenting both to learn the tool and to determine what numbers to give it.

Also I copied the block closely, and the LP ports and stud layout are larger than on the HP end.

(I had established the port and passage sizes originally from Martin Evans' book on model locomotive building, but I am not sure how valid that is on a compound engine, and it might work just as well - or not - with equal port faces.)

I used 0.2" holes - near enough 5mm - from habit of always drawing screw-holes to the o.d. to show the mteal boundaries. I am not sure what the "standard" convention is but on a finished drawing I'd annotate it as tapped or clearance anyway.

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John -

Thank you for the tip. I'll try to not that although it will probably be a while before I start using facilities like that.

Edited By JasonB on 19/05/2023 06:56:43

Jason -

Thankyou - I have just viewed the first few minutes of you video again, with the screen enlarged to try make the image clearer.

I wanted to establish how you make things symmetrical from the start and I think I grasped it. A matter of identifying what axes the shape is actually on, and making the first extrusion symmetrical about is plane. (I think)..

Anyway, after some trial and error, an invented exercise purely to test this move, and making the thing from squares, this was result:

(Stare at it too hard and the shaded bit sometimes looks like a pyramid on the top!)

Edited By Nigel Graham 2 on 20/05/2023 21:40:14

Very nicely done Nigel. It looks as though Alibre Atom 3D is going to be a very good move for you.

You are getting the hang of it. Even if not all the parts sit on the same lines of symmetry it is always possible to add guide lines when sketching and use those or additional planes in 3D which can also be used.