Why don’t we make models of things like this?

[HopperParticipant @hopper]

Posted by Mike Poole on 07/03/2017 20:59:06:

This was the compressor house at Cowley until 2001 when they were replaced with boring hydrovane boxes. There were four compressors, one is not shown. The two far ones were 2 stage 3000cfm, the motors were 600hp synchronous the exciter is the small unit on the end. They were started by a brine starter which is just a big tank of salt water with electrodes in it which provided the resistance to limit starting current. The piston of the low compression stage was 3ft diameter if I remember correctly. Outside was a chiller unit to cool the air and dry it to avoid problems with valves, it was also filtered to clean oil from the air as it was used for all purposes from paint spraying to weld guns. Next door was a substation which when I was an apprentice had open busbars, very scary place. I Don't think compressed air is used on the scale it one was, assembly was just the constant shriek of windy tools. Today battery tools are more convenient with no trailing hoses or cables. The big reason for replacing the compressors was modern robot welding guns use 12bar air and the old machines were a 6bar setup. No doubt the new ones are more efficient but these were 60-70 years old when they were retired and I doubt the replacements will last that long.

Mike

Edited By Mike Poole on 07/03/2017 21:11:41

Bit like the Ingersoll Rand XL compressors where I served my time at the Chrysler factory in Australia. They ran from factory opening in 1964 up to its closure in 2008 or so. The lunch and tea break table was just to the left of the picture below. Plus four very large boilers with blowers running flat out sitting across the floor. No wonder I have hearing loss today. Never thought of it but those old L twin compressors would make the basis for a good model. They had neat little oil pumps on the side with a row of cams operating plungers with oil going up through a sight glass full of glycerine.

[Mike PooleParticipant @mikepoole82104]

Posted by Neil Wyatt on 08/03/2017 07:15:56

PUMA-type robots might appeal to the younger modellers.

Neil

The Unimation PUMA was on of the first robots to use a programming language (VAL1). The mechanics are fairly primitive as backlash was reduced by meshing the gears tightly. The encoders were mounted on the end of the motor shaft and consisted of a slotted glass disc and a read head to give the A B and C channels. C was a marker to indicate one revolution of the disc. A geared potentiometer was part of the encoder assembly and a calibration routine was required to map the voltage at each marker pulse, once performed the robot could quickly find where it was. The downside of the shaft mounted encoder was that any end float in the motor shaft resulted in a broken disc this became a regular problem as there are six motors on each robot. As the discs were not a listed spare we commissioned a batch from a Swiss company at a very reasonable price. The control cabinet was another problem, the LSI 11 processor ran very hot so had a fan to cool it, fan failure resulted in most odd faults. The cards in the rest of the controller were inclined to have odd problems which very often were resolved by removing and reinserting the cards, I found that air pollution is capable of getting between the edge connector of the board and causing a faulty connection, reinserting the board cleans the connector although we usually used a soft rubber to clean the board contacts. This was actually a commonly used procedure on all sorts of equipment. The smallest PUMA we had was almost a model as it was a desktop machine we used for training. This was slightly different as it calibration was performed by putting the robot into limp mode and putting it into a precision nest. You had to remember to be supporting the arm when selecting limp or it just fell in a heap.

Mike

 

Edited By Mike Poole on 08/03/2017 10:59:57

[Neil WyattModerator @neilwyatt]

Posted by JasonB on 08/03/2017 09:40:18:

PS John Haining did a Scatter mill

I knew it was one of those damn cartwrights!

> 12inch howitzer the

Railguns – excellent subject!

> You had to remember to be supporting the arm when selecting limp or it just fell in a heap.

Awww!!!! Poor lickle wobot!

Neil

[Geoff TheasbyParticipant @geofftheasby]

Andy Ash,

One Alexanderson alternator still exists, in Sweden, and is fired up occasionally. Google it! 17kHz, I think. I also recal that the GPO Telephones system had multifrequency alternators for use in early trunking systems. (Apologies, I don't have the proper terminology)

Geoff

[Ian S CParticipant @iansc]

At one of the WW1 centenial exhibitions in Wellington (NZ) either at Te Papa, or at the National War Memorial, there is a model of a German rail way gun, I think it is 5" gauge, and about 6ft long.

Ian S C

[Danny M2ZParticipant @dannym2z]

I have been thinking about making scale models of ancient siege engines, trebuchets **LINK** ,battering rams and associated medieval weaponry. Our ancestors were so ingenious about battering down castle walls before the advent of gunpowder. My only plan drawings are from ancient woodcuts.

Anybody else interested?

* Danny M *

[Neil WyattModerator @neilwyatt]

I must admit I've thought about a making a model trebuchet or a ballista ever since I was a kid.

Neil.

[V8EngParticipant @v8eng]

Warwick Castle has an impressive replica Trebuchet which is fired regularly, it is apparently authentic. Having seen it a few years ago, I would not want to be on the receiving end!

I have put a link to the relevent info here. **LINK**

Neil, apparently they have a Ballista as well!

[Allan BParticipant @allanb]

I can see a little project in this, have got a few bits of oak nicking around, now just need to find some plans 😀

Allan

[duncan webster 1Participant @duncanwebster1]

Posted by Neil Wyatt on 08/03/2017 07:15:56:

Mike has widened the search out to compressors. Other thing that spring to mind are waterwheels and water turbines, I have seen a couple of windmill & waterwheel models.

I could go on

Neil

SWMBO wants me to make a waterwheel as a garden feature. Hubs and spoke slook easy enough, anyone got good ideas for rim and buckets?

[Allan BParticipant @allanb]

Traditional wheels are wonderful, no glue or pins, all just fit together, then a heated rim dropped on, flash quenched with water then it’s solid as anything.

Traditionally water wheels were make as two separate wheels, then wooden buckets spanning the gap, I have seen a couple of different hub layouts, one was a single hub with the two wheels mounted, the other had a centre shaft and a spacer separating them.

Early power is definitely a passion of mine 😀

Allan

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