Member postings for John Barber 5

Thanks, Gary, for that information confirming that it really was "once in a lifetime". But that account doesn't mention the total darkness during daytime which to me was the most strange and memorable part, something which would only be expected normally during a total eclipse of the sun.

I've just discovered this description of gab valve gear on Wikipedia. It mentions the Blists Hill engine but doesn't refer to the counterweight.

One of the strangest things I've ever seen was a weather event in the Birmingham area round about 1980 (I can't be sure of the exact year). I was working for Lucas Girling at Tyseley at the time, and I'd been on my own in a room without windows. When I came back into the main office area something was different, but what? Then I realised it was pitch black outside even though it was the middle of the day. Everyone was staring out of the windows and asking (not entirely jokingly) if this was the end of the world. The sky stayed black for some time then it seemed to turn green before going back to normal. At the same time there was a massive amount of rain. Some parked vehicles wouldn't start afterwards because water had got right inside their engines causing a hydraulic lock. Fortunately my trusty old Transit just managed to turn over and fire. Does anyone else remember this event? I've never seen anything like it since.

Edited By John Barber 5 on 25/07/2023 11:53:11

Some interesting thoughts there. It hadn't occurred to me that the engine had a slip eccentric, but obviously it must if it is to operate in both directions with just one eccentric. I was previously thinking it might have something to do with the need to stop the engine at a precise position to align the cage with the floor, but if it was just a question of balancing the crankshaft it could probably be done in a simpler way. I like the idea that this is more a slip eccentric feature than a winding engine feature. Could it possibly be just to reduce friction so the "slip" happens reliably?

Edited By John Barber 5 on 18/07/2023 13:52:04

The winding engine at Blists Hill Museum has a counterweight arrangement which applies an upward force to the eccentric. This seems to be a feature special to that type of engine. I've also seen one at the Black Country Museum which uses a tension spring for the same purpose. I've heard a number of different theories as to what the purpose is. Can anyone give a definitive answer?

Edited By John Barber 5 on 18/07/2023 10:20:01

Edited By John Barber 5 on 18/07/2023 10:41:47

Edited By John Barber 5 on 18/07/2023 10:43:47

Thanks for pointing out that thread. There are some interesting ideas in it.

Thanks to everyone who has replied.

I may never need to do it myself, I just find it slightly annoying that if ever I did want to do it, I wouldn't be able to! I'm surprised I've never heard anyone mention this limitation before.

I can see how a sub-table would solve the problem, but it would also further raise the top slide which is already about 3mm too high to take full advantage of quick change tool posts.

I'm a relatively new ML7 user, and this evening I realised for the first time that the top-slide clamping arrangement doesn't give you the full range of angles. It can't come within 30 degrees or so of being perpendicular to the lathe axis, as would be required for turning a blunt taper. This must mean that there are certain turned components which it is impossible to make on an ML7 - a truly shocking thought!

Or am I missing something?

Fascinating. The wheels remind me of the Shepherd ball castor.

Thanks, both.

If I do an Extrude Cut and the sketch goes outside the material, I am left with some red lines in the Part display. What are they for, please, and can I switch them off?

Yes, I've just discovered you can define a chamfer by a length and an angle. That would be a very good method.

Hi David and Jason,

I have a couple of questions related to the second MEW article:

1. I assume he only used 'revolve cut' to teach us the technique, as it would have been easier to use extrude with a draft angle, as we did for the tapered hole in part 1.

2. At the assembly stage, is it not possible in Alibre to 'mate' the two conical surfaces, rather than just align them? That would better reflect the physical reality of the situation.

Thanks,

John

Just wondering if you might have created a "reference" circle, rather than a "sketch figures" circle.

Many thanks, David.

Does it mean anything when a 2-D drawing dimension is shown in red? I added two further dimensions to an existing drawing and one came out red. I couldn't see any way to change the colour, but when I deleted the dimension and added it again, it appeared in black as normal.

Just going back to the question of creating a section view precisely through the axis of a hole in 2-D drawings, I'm still not seeing the ghost lines which David referred to, but I've found his other suggestion of using constraints works well for me. I deliberately place the section line slightly off target, so I can see it snap into the correct position when the constraint kicks in. If the hole appears as a circle in the parent view, I use a co-incident constraint between the circle and the section line. If the hole is sideways on, I turn on hidden lines, then use a symmetry constraint between the section line and each side of the hole. This makes sure that diameters are correctly dimensioned as such in the sectioned view,

Thanks!

Is there a rule that a sketch can be used only once? I thought I could kill two birds with one stone by extruding a single sketch in one direction without a draft angle, and then in the opposite direction with a draft angle, but when I try to do the second extrude the "OK" button is grayed out.

The Home key doesn't appear to work for me. I looked under Help to see how to edit keyboard shortcuts and it was supposed to be under System Options, but doesn't appear to there for Atom. Is it a Design only feature?