Member postings for Nick Wheeler

You're right, nobody would machine a part all over and then twist it for the other end.

But a link that only needs a drilled hole at each end at 90° makes perfect sense made from a length of twisted bar. Which would be modelled like these were. I must have a go when I've finished my roof-bar ladder clamps. And done the welding on the Metro.

Yes, that's how you use it!

Your initial planning ensures that you model the first part so it makes sense to you compared to Alibre's origin and planes. So your column sketch would be rotated around the vertical axis, or the base extruded from the horizontal plane which is how I would start and build everything from there. Then you can click on the front(or whatever) view, and check your new part/sketch aligns the way you expect before committing to it and wasting time and frustration.

Surely any 3D program has a 'home' icon, that will rotate the view to whatever you designate whether that's the front or an angled view? Used together with a 'fit to screen' function, that would prevent such problems. It would be one of the things a real, on-site tutor would mention fairly early on....

That seems a lot of work to me for such a simple, unloaded part. Why not just drill a hole through a short 5/8UNF bolt and solder(epoxy!) an appropriate barb in place? Make a complete part from one piece if you have time to waste. I've made brake servo adapters from delrin expoxied together, although they went on the cool servo not a hot A-series inlet manifold.

That would be the next step for my suggestion, especially if you made the taper turning attachment a stepper motor on the cross slide. Then you would have most of the mechanical components for full CNC control, and would only need a viable controller. Which would make a good option.

Modern lathes aren't that much different to old ones, so there's little point in reinventing the wheel. I suggest that there could be reasonable market for some useful upgrades to a common machine, along with improved fit and finish. Even if that added 50% to the cost of current lathe, the price would still be affordable and reasonable.

So:

start with a 10x22 with a 1.5Kw motor and VFD for reliable variable speed. That takes a similar space to a Myford, but has a more useful range.

Ensure all the controls are properly installed, and work smoothly. I was amazed at how much better mine became after some basic, unskilled work with a scraper.

Paint it well, after adequate preparation.

add an electronic lead screw for all screw cutting and power feeds. This would need a sensible interface, not the four buttons and two-line screen beloved of DIY jobs...

Standard DI chuck fitting.

Branded bearings.

As big a spindle bore as practical.

DROs that don't get in the way of anything.

Increase the cross slide travel so the entire diameter can be turned without any clever setups.

Design some accessories that don't currently exist, like taper turning attachment, milling slide and an electronic headstock divider.

All that would make a good machine even better, and I suspect wouldn't add a huge amount to the manufacturing cost - they already get painted, and the electronic components ought to compare well with the existing mechanical gearing.

It does help to get organised before you start. You wouldn't start drawing on a board without a reasonable idea of what you're trying to achieve and at least some of the dimensions - bore, stroke, wheel diameter, whatever - or a basic layout sketch.

I don't know if Alibre does this, but Fusion allows you to define and name parameters before you need them, or to name a dimension when you define it. The same applies to sketches and new planes/axes. I find it much easier to pick the required plane, axis or dimension from a list that includes Main Spindle Axis, Headstock Midplane or Main Bearing Diameter than pointing at the visual representation. So much so that I rarely have such construction features visible. This also makes it easier when you go back to the model later and can't remember what dimension329 refers to.

It is essential to work out why an operation didn't work as expected immediately, as it will probably spoil any subsequent work. That can be as simple as drawing the profile on the wrong face or plane, adding a diameter rather than a radius, or an inadequately defined sketch/extrude/body/component. It's one of many reasons I prefer to model parts in place, as dimensional errors are immediately apparent.

You probably want micrometers big enough for your work in addition to calipers. For most of my work, a digital caliper is good enough.

The digital Mitutoyo caliper I was given returns the same numbers as the cheaper ones I bought, although it is nicer to use. I don't use it because it's twice the length.

For 100 parts, I'd be adding a folding contraption to position the stock in the spindle too. A few bit of angle welded together, with M6 bolts for fine adjustment would be my starting point.

That doesn't happen to me, I'll take the grinder to spanners, sockets etc without a second thought. And I've never met a long-term mechanic without a collection of similarly modified tools somewhere in their box. A couple of mine include a 30mm spanner cut in half and the jaws slimmed to ease the removal of Yak 18 oil lines, and the open end of an 11mm spanner with a socket welded to it making a sort-of-crows-foot to make loosening/tightening the securing nuts for the air compressor possible, let alone easy.

Just checking it requires more knowledge, skill and judgement than you currently have, which is proved by your chuck experiences.

Put the effort into actually using the machine to make some simple parts appropriate to your requirements for buying it. Then you'll be in a better position to fiddle about with the alignment, assuming that it's even necessary - I bought my lathe 8 years ago, and the installation procedure was to carry it down the cellar steps, stagger across the floor, plonk it on the bench and plug it in. It's never been bolted down, and the parts produced have always worked well enough.

I have the earlier one too. It's excellent, which you would expect for the price. But it has always worked and easily sets M8 rivnuts, unlike the plier type it replaced. Using caphead screws as the mandrels is a definite improvement if you use it a lot.

I suspect that M5 is as big as the tool will reliably set. I found my similar but cheaper version broke doing one. And it was a toss-up whether I broke first, or the tool did.

Edited By Nick Wheeler on 17/04/2023 16:38:54

Then why make such a big deal mentioning it? Effective suspension and steering geometry is complex enough that concentrating on the parts relevant to your current issue is sensible. For instance, ensuring that the King Pin Inclination intersects the ground in the centre of the tyre contact patch does have a noticeable affect on how much steering effort is required at the wheel. Getting it right also makes the vehicle actually turn better, instead of scrubbing across the ground.

I know someone who found and installed a stock width rack for his custom front suspension(mostly XJ6 in a Minor). But it was a rear steer rack in a front application and the wheels turned the wrong way. That led to an 18month sulk before he fixed it....

What makes you think Ackerman geometry affects the number of turns lock to lock? That's entirely down to the gearing in the rack/box/chains/whatever.

That video is largely how I made my crank. And it's done in eight minutes.

While it shows the steps required, it's a demonstration and not the tutorial Nigel needs to correct his misconceptions of how the program works. From what he's written many times, that tutorial needs to be face to face so that the explanations and resulting questions can be answered immediately without adding extra misunderstanding. That would probably make for a thirty minute session.

But if I was running the tutorial, instead of random exercises I would use the three examples he's already struggled with: the chassis rails, pumps and wheels. That would give a solid grounding in all the aspects of how and why to use either 2D or 3D base sketches, dimensions and constraints, extrudes, revolves, construction planes, projected geometry from already created and matching parts, joints etc, using parts he already understands and needs.

That's an afternoon, or preferably a couple of evening sessions helped along with beer, chocolate cake or whatever he prefers in such situations.

First item on the agenda would be a mind-wipe of anything to do with TurboCad!

Edited By Nick Wheeler on 14/04/2023 12:42:27

the computer can do that arithmetic better than you, and it already knows where the bits are and how their geometry relates to other parts. So a joint is created by specifying which features(edges, holes, centres, points, specific custom requirements etc) on the two parts need to match. Next you offset or rotate them as necessary - two joined parts don't necessarily need to touch. Then you specify how you want one part to move(or not) around another, whether that's rotate around one axis and slide along another or other simpler movements. Finally you add the limits for how far it can move.

The centre of a circle will still be a viable connection even if you make it bigger or extrude the face another 5mm. That won't be true if you calculated how far apart the original parts were.

So my crankshaft has marked joint origins at the centre of each end of the main journals. These are then mated together, and the new part rotated 90, 180 or 270° as dictated by the firing order. And if you get that wrong, changing it just a matter of editing the joint to a new number.

How can a 2D representation of a complex 3D object not be compromised? That's true whether it's of a view from the top of a hill or parts for a toy train. Written descriptions of the same things would be equally compromised.

As for the drawings, I suspect the only part I'd want on paper is the crankshaft, and that's mostly to get each bigend journal clocked correctly. Most of the rest of it could be dimensioned on the relevant face of each isolated part on the screen as needed without any extra work. Many of the decisions how to make the part are covered by how it was modelled originally, which is why I suggest that just chipping bits off a piece of virtual stock isn't the most efficient way of using CAD. These are just some of the reasons why the time spent learning the basics are a worthwhile investment; I couldn't do any of this in 2D, let alone on paper.

I don't have any need for anything more than the free version of Fusion; the main things I would gain would be to edit linked files in place, be able to work on more than ten files at a time(you can change the ten you want so it's annoying instead of a problem) and more advanced CAM. I don't currently have a CNC, so that last one isn't even an annoyance. Fusion's files don't have to be stored in the cloud, and my weird stuff is of no use to anybody else. But the cloud basis is an excellent reason not to use it commercially.

I still think the barriers you struggle with are because it doesn't work quite the way you think it should and don't have anyone to give you the jolt needed to get around that - like thumping an old TV when the picture started to roll. The same might apply to me with Turbocad, as I struggled with it on and off for years without producing a single usable piece of work. Many other users, including you, report the same problems. Some of those are simply down to the complexity and power of such programs; I can't do complex stuff in Word for example as I've never needed more than arranging a few paragraphs.

You keep saying that 3D first requires extra and specialist knowledge, but so does 2D draughting - much of it even more arcane, hard to explain and demonstrate. It doesn't take much knowledge or ability to start just knocking bits off a cube to get what you want, but it isn't particularly efficient whether it's on a screen or the bench.

Nick's engine image isn't a rendering, but straight from the design space. I don't have the artistic knowledge to use the settings to create pictures that don't look like cheap cartoons, and won't get any value from proving that again.

That engine started from a single sketch of three circles and two lines that define one crank journal:

with copies made, offset and jointed appropriately to create the whole crank. That offset was defined as a parameter and reused similarly for the bores, valves, ports, throttle butterflies and many other parts. Definitely not the long way around! The most difficult bit was creating a plausible exhaust manifold using 3D splines...

Since I finished it, Fusion gained a tangential joint so even the valves are now animated by the cams, which shows the clearance. Each part is defined as the appropriate material - aluminium for the block, steel for the crank, brass for the butterflies etc - and Fusion suggests the whole assembly will weigh 3328g.

If I ever do get around to building this, the block and head will require more thought, as they could only be made by casting - the block would be better split into separate, machinable crankcase and cylinder blocks, just as the cam boxes are separate to the head.

If I'm honest, a single cylinder engine is all I really need to make, as a four cylinder(better yet a V6) is just lots of tedious repetition.

With the complete model available, separate orthographic drawings with all their compromises won't be necessary to make many of the parts.

I've often wondered why modern small lathes don't come with an ELS as standard or even as an option.

An aftermarket conversion is going to be far more expensive to buy than a manufacturer installing them by the thousand. The mechanical parts are hardly complicated after all.