What Did You Do Today (2017)

[JasonBModerator @jasonb]

But is the Force not also affected by radius and SPEED

M w2 r

So if Andrews balls are moving faster then they will generate more force which lets face it is how a governor works

[Neil WyattModerator @neilwyatt]

Posted by JasonB on 12/07/2017 20:44:41:

But is the Force not also affected by radius and SPEED

M w2 r

So if Andrews balls are moving faster then they will generate more force which lets face it is how a governor works

I'm assuming that gravity, speed and radius are pretty much fixed for any given engine. the arms need to be to scale, the governor is meant to fix the speed at a realistic value and if steam engines could pick up gravity waves they wouldn't have had to spend a fortune on LIGO.

So… the only thing it's practical to change is the mass of the balls, either by making them slightly over-scale or using something like lead (depleted uranium would be ideal but don't go inhaling the swarf…).

[duncan webster 1Participant @duncanwebster1]

With a Watt type governor, if you want to run the model at the same speed as the original, but still have the arms at about 45 degrees to vertical you need to run the governor faster than its full size cousin by square root of scale, so a 1/10 scale model governor should run at sqrt(10)=3.16 times. Changing the mass of the balls won't affect the angle, but it will affect the 'power', ie how much force it exerts. With spring loaded governors it's more complicated, but intuition tells me running faster is good.

[JasonBModerator @jasonb]

As I said earlier model traction engines DO run faster than full size so you have already gained an increase in force which may negate the need for heavier balls.

Thickness of the flat springs on a pickering could be altered with the difference being hard to see without a micrometer

Slight reduction on pully dia would be hard to spot and could easily give another 10%

Final decider may be to ask youself how much belt work you are likely to do and would the extra effort be worthwhile?

[Martin KyteParticipant @martinkyte99762]

According to Marks Handbook, for a Watt governer, which is essentially a conical pendulum, the equation of the governer is given as 35,200/square of the RPM which gives the hight of the balls from the top pivot in inches and is mass independent which is the main point of interest. "There is a definite ball position for a given speed. and the governer is said to be static. " (quoted from the book.) and the controlling force consists of the weight of the balls. It goes on to say that if a heavy weight is added to the sliding (bottom) part of the governer (the sleeve) it becomes a Porter or loaded governer and when the four arms are of equal length the equation fro the hight is

[w +w1)/w}x35,200/RPM^2

and goes on to say that this type can be run at higher speeds, is more powerfull with the same weight balls and gives more control motion for a given increment of speed.

For spring loaded governers, which is what Andrew is building it states that "the controlling force is partly or wholly produced by springs called( speeder springs) and that "sensitivities of the order of 0.01% is obtainable.

So whilst I totally agree that more massive weights would seem desireable in a scale governer it is the lessening of controlling force that is the basic issue rather than the position of the balls at a given speed. Since Andrew is working on a spring loaded governer the controlling force would seem to be selectable by altering the spring rate rather than messing about with denser material for the balls.

I have taken note of JasonB's comments regarding faster speeds and that he has already suggested the variation of spring rate.

Im sure Andrew will shortly dazzle us with the sums as it would seem to be well within his capabiliies especially after being scared off with the price of tungsten. The only cheaper way I can think of, is have a wander around Iraq looking for depeleted Uranium, but then again, maybe not.

Thanks, by the way, for getting me interested in this line of research.

regards Martin

Edited By Martin Kyte on 13/07/2017 08:59:48

Edited By Martin Kyte on 13/07/2017 09:01:56

Edited By Martin Kyte on 13/07/2017 09:02:43

[Martin King 2Participant @martinking2]

Hi All,

Bit off the wall but I have been messing about with the bits and pieces left over from a large haul of micrometers and milliing cutters and finally came up with this but not sure which 'shade' looks best (if any!)

Its been fun doing it and even 'The War Office' approves!

I am clearly losing the plot…. Cheers, Martin

[NigeParticipant @nige81730]

Looking good now Martin

[RobboParticipant @robbo]

You're not alone Martin. I inherited a hefty Chinese 4-jaw chuck with a Boxford lathe, and used the chuck as a base for a standard lamp. It was only a 6" chuck, but weighed 11 kg. 

Edited By Robbo on 13/07/2017 17:38:13

[Anonymous]

Posted by Martin King 2 on 13/07/2017 15:06:48:

Bit off the wall but I have been messing about with the bits and pieces left over from a large haul of micrometers and milliing cutters…………

That's a shame, at least three of the four milling cutters look to be in pretty good condition – all you need is a horizontal milling machine.

Andrew

[Martin King 2Participant @martinking2]

Hi Andrew,

Got quite few if those cutters, mostly what I might call thick slitting saw types if you need any.

No use to me except for this kind of fun stuff.

Martin

[Anonymous]

Posted by Martin Kyte on 13/07/2017 08:58:46:

Im sure Andrew will shortly dazzle us with the sums as it would seem to be well within his capabiliies especially after being scared off with the price of tungsten.

Bother, more mathematics to do; I'm never going to finish the traction engines at this rate.

There seems to be a dearth of information on how the Pickering governor actually works, and what is important. So to start with here is my qualitative explanation of how I think it works. We have three rotating balls on vertical leaf springs. As the governor speeds up the balls tend to fly out, but are constrained by the leaf springs. As the balls move out the leaf springs become bent and the ends move closer together. So far so good. The Pickering governor arranges that the leaf spring ends moving together cause a central spindle to move downwards. There seemed to be some confusion about the categorization of the Pickering governor in the literature, but as far as I can see it is a spring loaded governor. This is because there is an adjustable torsion spring resisting any downward movement of the central spindle. When these forces are in equilibrium the the sleeve valve operated by the governor should be in the correct position to let the engine run at the set speed.

Now the first question is what do the leaf springs actually do? If the downward force on the spindle caused by the balls moving outwards is countered by the torsion spring, why would we want the leaf springs to do anything at all in terms of resisting movement of the balls? So my WAG is that the leaf springs are essentially to hold the balls in place and act as flexible levers rather than as springs per se.

The force acting downwards on the spindle can be countered by adjusting the torsion spring, so do we want the forces to be large or small as they largely cancel anyway? I think larger is better within reason. Inevitably there is going to be some friction, static in particular, involved in moving the sleeve valve. I think the forces in the spindle need to be somewhat larger than the frictional forces, or the sleeve valve will not move proportionally. I'd see this as a sort of deadband, potentially leading to hunting, which rather defeats the object of the governor in the first place!

Mention of friction leads to another practical point. From what I can see of the full size Pickering governors they often came with attached valves, which were balanced, ie, the governor didn't need to work against the steam pressure. In the drawings I have this isn't the case. The sleeve valve is simply an inverted open can operating in a hole which crosses the steam path to the valve chest.

There are several possibilities; one the governor was never really intended to work, but just be for show, so it doesn't matter if the sleeve valve doesn't operate smoothly. There is nothing about finish or tolerances on either the sleeve valve or hole on the drawings. So is the hole intended to be leaky so that the sleeve valve sees roughly the same pressure top and bottom?

Or should I just drill a small hole in the top of the sleeve valve?

That's enough pontification for the moment; the washing up calls!

Andrew

WAG = wild a** guess

[Neil WyattModerator @neilwyatt]

Observation, governor valves don't need to close, just be able to constrict the flow.

[JasonBModerator @jasonb]

Should have made a Fowler with its balanced valve operated by the governor

Do you know what the full size Burrells had rather than what is on the model drawings?

 

EDIT. A quick look in Gilbert's and it seems the Burrell valve is a very similar shape to that of the Fowler

Edited By JasonB on 14/07/2017 08:11:40

[Anonymous]

Posted by Neil Wyatt on 13/07/2017 21:42:37:

Observation, governor valves don't need to close, just be able to constrict the flow.

Hmmm, the full size traction engine boys say that a throttling (Pickering) governor needs to be set up so that the steam can be cut off completely, ie, valve closed.

Andrew

[Anonymous]

Posted by JasonB on 14/07/2017 07:30:09:

Do you know what the full size Burrells had rather than what is on the model drawings?

I understand that Burrell made their own Pickering style governors. In the book by Gilbert there is a rather useful works drawing of the Burrell SCC cylinder. A section view clearly shows a double valve seat, and valve,.for the governor.

It's a right PITA but I have to go to work now. I'd much rather ferret around for information on how governors behave. Roll on retirement.

Andrew

[Clive HartlandParticipant @clivehartland94829]

A little while back someone asked about the rotary overlapping decoration on tools and things, I was watching a TV programme about bespoke watches being made and they were decorating parts of the watch in that manner and they called it, 'Perlage'.

I have seen it used on the breech of shotguns and supposedly it retains oil on close fitting sliding parts.

Clive

[MikeParticipant @mike89748]

It tends to be called "engine turning" in the gun trade, as far as I know, and it does create an oil-retaining surface, as does the pattern left by hand scraping. I once applied "engine turning" to something I'd made by holding the job in a vertical slide on the lathe, and made the circles by gripping an unsharpened pencil in the chuck and applying a little valve grinding paste. It was such a boring job it was hardly worth it, so does anyone know how it is applied on an industrial scale?

[Steve PaveyParticipant @stevepavey65865]

Years ago an old toolmaker told me that, during the war when many women were working in the armaments industry, he had several in his toolmaking department. They were making go/no go gauges for the turners on the shop floor. One of the women decided to finish her batch with engine turning, and got told in best toolmakers language not to waste time. However, the ones she had finished were sent down to the shop floor, and because they had been finished so well they were treated with much more care than the others – as a result lasting a lot longer. Once that was realised engine turning became the standard finish.

Done with a piece of dowel and some abrasive, some people prefer to call it spotting – real engine turning is done with an ornamental lathe with a cutting tool, according to horologists. Also seen on old Bugattis and the engine cowl of the Spirit of St Louis.

[V8EngParticipant @v8eng]

At the 2017 Ally Pally Model Engineering Exhibition there was a demonstration of work by the Society of Ornamental Turners, it included somebody doing engine turning on metal.

I have put a link to the SOT website, much of it relates to woodwork but the napkin ring fiesta has some good exmples in metal.

The machinery used to achieve the effects is fascinating as well, it's worth a browse of their site.

**LINK**

I remember seeing an American site on clockmaking which showed a flat ended sort of spindle rotating (end on) against the work piece then being moved along to the next position, now there's a job for cnc! sorry cannot remember the site's name.

Edited By V8Eng on 14/07/2017 10:31:43

[richardandtracyParticipant @richardandtracy]

I really do not understand why it's not referred to as ornamental milling. In most of the decorative work, the lathe is there as an indexing mechanism and a rather unusual flycutter is used. That makes it milling to me.

What you call it has no effect on the complexity & quality of the work, though.

Regards,

Richard

[Neil WyattModerator @neilwyatt]

Posted by Andrew Johnston on 14/07/2017 07:54:16:

Posted by Neil Wyatt on 13/07/2017 21:42:37:

Observation, governor valves don't need to close, just be able to constrict the flow.

Hmmm, the full size traction engine boys say that a throttling (Pickering) governor needs to be set up so that the steam can be cut off completely, ie, valve closed.

Andrew

That's probably more to do with getting it adjusted properly than the need for it actually to cut off the steam flow when in use?

As an electronic analogy, I think a governor is nearer to a linear controller rather than PWM

[BazyleParticipant @bazyle]

The Ornamental Turners have been at MEX too but were sometimes hidden behind the stairs.

This is an example from my album Sandown12

[Neil WyattModerator @neilwyatt]

Google isn't all bad. It offered me an app earlier, free access to the Feynman Lectures on my phone!

I expect a fascinating but difficult ride!

Neil

[Martin KyteParticipant @martinkyte99762]

Well if you can't understand it from Dick Feynman you are never going too. Enjoy.

Martin

[Anonymous]

Posted by Sam Longley 1 on 12/07/2017 08:38:22:

Being a beginner & at the risk of looking a total idiot – does the tungsten have to be "pure".

No it doesn't; it's more a case of what I can obtain. Pure tungsten has a density of 19.25g/cm³ whereas the alloy I chose (97W-Ni-Fe) was 18.5g/cm³. Other heavy alloys were around 17g/cm³. The tungsten/copper alloys obviously vary, in the ratio 80/20 the density is around 15g/cm³ which is still very respectable compared to steel.

I had looked at fishing weights, but I assumed they would come in a large enough size? The finished balls need to be around 3/4" diameter.

Andrew

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