Member postings for Chris Gill

Hi pgk

It was felled last year and will take some time to rot - still trying to grow. I'd forgotten about the potassium so I guess it could have created something akin to Prussian blue (pot ferricyanide)

Chris

I decided it might be a good idea to dig a large hole in a tree stump and plant something in it to hide the stump (a lime tree that was becoming dangerous). After chain drilling lots of holes with a spade drill I went in search of some beefy chisels and picked out a large gouge and a big locksmith's chisel (both over 100 years old and once the property of a great-great-uncle, I think).

The gouge had a couple of surprises in store (no, I still have all my fingers). On one side it has the maker's name - "H Wilson, Cast Steel" but on the other side it has a little picture of a boat with a coxswain and two rowers. Underneath it says "Oxford wins". Was that a common thing to do?

The second surprise was that it reacted with the tree sap and the sap on the blade turned blue (similar to Prussian blue). I know sap usually has a low pH but I'm puzzled by the colour. Any chemists out there got any ideas?

Howard - yes, I've been reading up on the arguments between Watt and others. Interesting.

Actually, Cruquius was one of three engines, all with 12-foot cylinders and annular pistons. The first one had 11 external pumps with the same total lift as the 8-beam versions. There are also two internal pump beams, another pump driven off one of the main beams and an additional beam to drive the control mechanism.

Nigel - I would love to have seen Ron's engines, they sound fascinating. You're right, the cataracts are going to be a challenge and then there is still the hydraulc stay (two rams that stop the piston creeping down from the top of its travel).

Unfortunately, I've backed myself into a corner by ignoring rules of thermodynamics that I learned 40-odd years ago and never used since. Cold compressed air aint the same as hot pressurised steam so my valve will never close (the cataract controls the opening of the valve in this engine). And nothing in my build will handle hot steam (aluminium, steel, pipes soft-soldered ...). With around 1000 parts so far, I don't want to start again.

The temptation is to follow Ron's example and automate the steam and equilibrium valves. It feels like cheating but it keeps the rest of the engine looking and acting like the original. I can see another option - make two more cataracts with scoggans and all the rest, except I can't see where to fit them in. At 1/30 scale, my fingers are a yard across!

Thanks to all who tried to help in spite of my rather vague question. Maybe a bit more background would have been a good idea to start with. I intended to post this last night but tried to show off by spending hours making a fancy meal and then fell fast asleep. Maybe some things should be left to the experts.

I'm trying to build a small scale (1/30) model of the biggest steam engine there is and using compressed air rather than steam. I went for the Cruquius engine because of the fascinating control gear and the excellent web site (**LINK**). I chose a small scale because I didn't think I'd get it through the door otherwise. I haven't built the cataracts or the hydraulic stays yet and, as someone said, miniaturising the cataracts will be interesting. The rest of it is working apart from the problem with the inlet and equilibrium valves.

With air, I don't need the condenser or the exhaust valve and I consolidated the annular piston and the main piston. The original was 12 feet across.

This is the cylinder before I put it in the engine:

And one of the control gear (sorry its on its side):

And the model so far with the cut-away building - an attempt to show off the 7-foot thick walls:

In this engine, the piston moves the valve control beam, which moves the plug frame. The plugs move the horns, which move the angular transformers and close the valves. The cataracts release the scoggans and that lets the counterweights open the valves. So my problem is to persuade the engine to keep moving enough to close the valve while it needs air to keep it moving.

Incidentally, the last sub-page on the Cruquius site is the detailed restoration report and is a really interesting read. I've learnt a lot from project already - I even discovered that "junk" is a perfectly good engineering term.

I agree - electrical valves just seem wrong but no matter how much I alter the timing, the valve never quite closes. The air pushing the piston is also operating the valve via the linkages. Other engines that I've built were reciprocating and had a flywheel to keep things moving past cut-off. The beast I'm trying to build has a pause at the top of the stroke, which allowed the pump buckets to sort themselves out, and a pause at the bottom of the stroke.

If I just push the valve stem down a little, I can get things to work until the next cycle. And there are two valves, essentially to let air in and out again, but they both have the same problem so to get it working I need both hands in the guts of it.

Hmm, lots of head scratching going on

Hi Nigel

It's a Cornish beam engine with steam (air in my case) pushing the piston up against the weight of the cross-head. After shut-off the piston continues to rise and linkages driven off a secondary beam operate the valves. The restoring force is the cross-head and that pulls the beams down again. The original was a pumping engine

The valves were originally Cornish double-beat valves but mine are a little simpler - just a sliding piston that closes the ports.

I wonder if anyone can suggest a way out of a dead end I seem to have created for myself.

Some time ago, I decided to have a go at a freelance project and build a Cornish engine. As I don't (yet) have any experience with live steam I decided to use compressed air.

Lots of time, planning and building later and I realised there was major flaw in my original idea. As the piston approaches the cut-off point it operates a linkage that closes the steam valve and residual energy in the steam continues to push the piston. But compressed air has no residual energy and so my engine reaches an equilibrium point where input pressure is balanced by leakage and restoring forces so it never actually closes the valve and just sits there hissing at me (OK, the valve isn't perfect!).

It doesn't matter how much I tinker with the linkage or the input pressure, it never closes the valve.

I've been puzzling over this for ages and the best I can come up with is to use an electromagnet to pull the valve closed at the right time. But I'm working at a very small scale so I'm still scratching my head over how to build the valves (equilibrium and steam) and find a position for the microswitches.

Is there a design for a valve that magically cuts off a couple of seconds after its been told to close?

Hi Rod

Wild flowers have become an interest of mine and I use Pl@ntnet to help identify things. I found Diosma Hirsuta in the Rotacea family seemed to be a strong candidate. It may also be called Pink Confetti Bush but I don't know any more about it than that.

The URL I use is: **LINK**

Chris

I bought a Creality Ender 5 recently and I like the machine

First job - more parts for the printer. Second job - fix toys for the grandchildren.

Now, I'm sure I had a project or two in mind ...

I hadn't thought of chickens but the house is part of a farm so it makes perfect sense.

Thanks MichaelG

A friend of mine found a rather curious thermometer in the cellar of a house he's renting and sent me a photo yesterday. My guess is that it's for brewing wine but if anyone else has theories around the combination of Fahrenheit and Weeks ...

If I could be bothered digging out my books on engineering thermodynamics (anyone remember Rogers & Mayhew) I could deduce something from the aparently linear rate of cooling but, hey, it's the weekend

Thanks to Shaun & Keith, my new hearth arrived safely. Now I can ditch the remains of an old Baxi fireplace that I took out a few years ago.

Hi all

I installed a 2-axis MDRO unit on my mill recently and it made a big difference to my work. Unfortunately, I found that the user manual is incomplete when it comes to machining an arc in the vertical plane.

After a lot of messing around I figured out how to do it. I also discovered that the default Y-axis direction means things don't work as per the book so I changed it to 1. I also found that the XZ options isn't available on this model of DRO.

If anyone is using this DRO and wants to machine vertical arcs I've created a 2-page addendum that might help. However, as I can't upload DOCX or even PDF, I've converted it into two JPG files below.

Let me know if there are any cases of muddled fingers (or if I've completely lost the plot)

Chris

Hi Gavin

I have the mill version of this DRO but the setup looks to be universal. When you switch it on you'll see the linear resolution on the display, I think mine says "LIN-5" or similar. Press Enter to get into the setup (you only get a few seconds). You can then scroll through the various options using the arrow buttons and should find DIRECT and there'll be a 0 or 1 in the X and Y values (and Z if you're lucky). The book does describe the conventional setting quite well but doesn't say which is 1 and which is 0. Rather oddly, you press X and Y to toggle the values rather than 0 or 1.

I just had to change the settings on my mill to get things to work as per the book.

If you drop me a PM I'll try to scan the manual to PDF for you

Hope this helps, Chris

Ah, that makes complete sense. Thanks Jason and John

Hi all

I've been using my SX2.7 mill for several months and only just paid attention to the front edge of the table. There is a T-slot just above the X axis scale and it seems to take a square M5 nut but nothing larger. Just above the Y axis handwheel there are two tapped M4 holes.

The T-slot appears in the diagrams in the manual but isn't referenced.

My theory is that they are for mounting a DRO (hence my interest) but does anyone know what these were actually intended for?

Sorry to say, I also find this new viewer unusable. As with others, the whole point of my digital subscription was to be able to use the archive. I often find I have to print to PDF so that I can enlarge some of the diagrams. I hope someone has a serious re-think.

Chris

After lots of messing around I finally managed to model something I may, one day, try to make.

I even got the various items working and it highlighted several small problems in the original design. Thanks for all the expert comments on this thread.

I have to admit I do keep hitting frustrating problems - reference lines that don't stay put and may vanish without trace, stack dumps and sketches that were editable before I clicked Save and then become locked in some way. Looking on Alibre's forum it seems even the professionals are having problems.

Thanks Jason

I was trying to think of a way to do that and kept getting it muddled up. That solution looks perfect

I may be missing a trick, but ...

I'm trying to model the top end of a piston rod. It consists of a cylinder with a slot cut most of the way along its axis. Then it has a hole drilled (extruded) through near the top. All OK so far.

Finally I want the top to have a half-round profile when viewed from the cross-hole side but square when viewed from the slot side. I've tried chamfer and fillet but, of course, they apply all the way round the edge. Is there a straightforward way to do this? Or do I need to create the top using separate sketches and extrusions?

Thanks