Member postings for John Olsen

Mamod boilers are brass and dezincification does not seem to be a problem.

How bad is the dent? Is it worth worrying about? They run at a pretty low pressure, and provided they are used with the standard burner are pretty much inherently safe, eg if the safety valve was blocked off the burner would be unable to build up enough pressure to burst the boiler. Also the burner would be unable to heat the boiler up to a temperature that would soften the joints or damage the material even if bone dry. They are below the size where there is any legal requirements in most countries.

John

Most of the Weir pumps had Monel metal piston rods. I have about four inches cut from one that had been quite badly seized. I also have a copy of their catalogue somewhere, I wonder where that is?

John

I don't know how they are installing fibre in the UK, but here in NZ it only required two small holes on my property, one right by the house where the fibre comes out of the ground, and one in the lawn area where they were making a turn. Both about a foot square. The fibre was put into the ground using a machine to thrust from one end, and one of the guys used a detector device so that he could tell where it was going and correct the angle from the thruster machine. So no real disturbance to any of the garden, not that ours is especially fancy, but there are trees and shrubs. It would be 30 or 40 metres from the front fence to where the fibre enters the house.

Satellite was good for getting connected (Internationally) back in the day, but has some limitations. There are only so many spots in the geostationary orbit, and the delay is long enough that you don't want a double hop. The bandwidth is limited by the range of frequencies that pass through the atmosphere easily. The delay is not so much of a problem for TV, but can be for Internet connections. So hence lots of long distance optical fibres have been and are being laid, since you can get plenty of bandwidth, and increasing the number of fibres in a cable does not greatly add to the cost of the installation. This is also why there is interest in constellations of low orbit satellites, since it pretty much eliminates the delay, at the cost of requiring handover between satellites at frequent intervals.

For local connections, fibre has a lot of advantages, not least bandwidth but also being less prone to getting stolen and less problem with corrosion.

John

Well, I find the study of this sort of thing fascinating, even if we may never know the full details of this device. It does give us a glimpse of the sort of things that the ancients were actually capable of. The existence of this one device obviously implies the existence of a workshop capable of making it, and although one does not expect them to have been mass produced, there were quite likely more than one made, as well as possibly simpler variants when the ideas were being developed. The problem of course is that metals does not always survive well, both due to corrosion and also due to the fact that it is very recycleable.

As well as this, we know about Hero's simple steam turbine. I wonder what else they might have been playing with?

John

A gyroscope will move at right angles to the force applied. They don't really resist movement, they just try to move at right angles to the force applied. So if you have a gyroscope with a vertical axis and you push the top away from you, it will actually move to the right or left. Which way will depend on the way the gyroscope is turning. So now if you have two gyroscopes of the same mass and rotational speed on the same axis, one turning clockwise and the other turning anticlockwise, when you push away, one will want to move right and the other will want to move left, both with the same force, so they will cancel. The only remaining resistance to movement will now come from the total inertia of the system.

You do generally move the bars to initiate the lean, but it is only by a very small amount. If you think about the fact that you might only want to move the track of the wheels across by a foot or so, and you might be traveling at fifty feet per second or so, you can see that a very small angle on the handlebars would shift the track of the wheels sideways by a large distance quite quickly. (It is not too hard to exceed fifty feet per second on a bicycle, let alone on a motorcycle.)

Getting a motorbike or bicycle to lean by shifting weight is one of those things where the tyre contact forces come into play. Shifting your weight to one side makes the tyre contact area with the road change, which introduces forces into the steering. You will I think notice that the control available in this way is very limited compared to what can be achieved with the bars.

John

Gyroscopic forces have got very little to do with it all. Bikes have been built with counter rotating flywheels beside each wheel, which can be used to completely cancel any gyroscopic effects. It is still very easy to ride such a bike.

The main factor in balance on a bike is like balancing a broomstick on your hand, except you only have one plane to worry about with the bike. When you are going straight, you move the steering as required to keep the centre of support under the centre of gravity. When you want to turn, you steer to move the centre of support out to one side, then steer so that all the forces balance. So you actually push slightly the "wrong' way to start the turn, then steer slightly with the turn, Then to come out, you steer a little tighter into the turn to get the bike upright again. It doesn't pay to think to hard about this while you do it!

Centrifugal force only exists if you have a rotating frame of reference, what is actually happening is that as you turn you have a centripetal acceleration, which to the rider in his rotating frame of reference appears as if there is a force away from the centre. This is not a real force, it is just things trying to continue in a straight line.

Forces from the tyres also make a difference, that and castor and trail on the front are why a bike can continue for a while with no input from the rider, although it will usually tend to drop into a curve.

John

I have that issue. I will send you a personal message.

regards

John

Try it with a magnet first. Obviously if it really is bronze or brass there won't be any suck, however this looks a bit like a couple of gears I have in a drawer. They were spare primary drive gears for some sort of two stroke motorcycle engine that I picked up at a surplus shop. Mine are steel, but as is sometimes done they had been copper plated. This is done selectively to allow nitriding only the surfaces that need to be hard. So the teeth would not have been plated, and would get the hardlayer, while the rest of the material would remain in its normal state. Which is still likely to be fairly tough. The plating typically seems to end up going black, but apparently is enough to stop the nitrogen reaching the steel underneath.

I've seen connecting rods treated the same way, so the eye where the rollers ran on the crankshaft would be hardened while the body of the rod would not.

John

DC31K has said exactly what I thought when I saw the pictures. Cutting keyways in shafts was once an important function for shapers, and if you look you will find that some power shapers are built so that you can if necessary feed a shaft right through the machine. One of mine has a forked end on the connection to the ram to permit this, so you could if necessary cut a keyway in the middle of a shaft of any arbitrary length. (You drill a hole at each end to permit the tool to start and finish the cut.) The setup on the shaper pictured above would also permit that.

John

OK, this is not a Stuart. Not that that matters for the questions, and it looks like a nice design.

If the two eccentrics are being made in one piece, then the angle between them would matter, however if as is more usual they are made as two parts, then the angle only matters when you set them up on the shaft, one being set for each direction. Since your eccentrics are supposed to have a groove, there is nothing to stop you having a small grub screw set down inside the groove to bear on the shaft, so each eccentric can be set separately

The hole in the bottom of the strap is for a small screw with a spigot on the end. The thread only goes as far as the thickness of the strap, and the spigot protrudes into the groove on the eccentric strap. This stops the strap working sideways on the eccentric. Some designs make the strap with a groove and the eccentric with a ridge around it, which is more like full size practice and would provide more surface in contact. But that is more tricky to machine, especially in small sizes.

John

I just measured the centre from my early eighties original Unimat 3. It measures as 10.37mm on a metric mike, or .405 on my Moore and Wright. It is parallel, a ground surface, and is an easy slide fit into the headstock or tailstock bore. I would guess that it was originally chosen to be the largest that would fit inside the spindle thread while leaving enough meat for the chucks etc to screw on.

I've never had anything try to jam in either bore. I would have preferred a proper taper, except I would guess that such would reduce the size that can go through the headstock. I guess you can't have everything on such a small lathe, and it has done some good work over the years. I've done between centres turning and also between centres milling for a Stuart double ten crankshaft and it has always done the job.

regards

John

Meanwhile I have several empty or mostly empty drill boxes here in NZ. It turns out to be uneconomical to buy the drills to fill them, you can buy a full set in another box cheaper than buying loose drills of the same quality.

John

Not long after the 70's fuel crisis we had a talk at uni by a guy who had been researching the possible effects of adding ethanol to petrol. One concern was the effect of the ethanol on the plastic floats in some carburettors. He said that one thing they had found was that the material in a Jaguar carb float was in fact not even suitable for use with ordinary petrol........

John

Figuring out how to hold things can sometimes be a quite major part of the art of machining. Quite often the thinking and planning part takes longer than actually mounting the part, which then takes longer than the actual machining.

I've used sacrificial layers added onto the faceplate quite often. These can be plywood, or if you want a more accurate thickness, a piece of aluminium, which I prefer. They can be held on in various ways, depending on whether or not your faceplate has T slots or through slots. Whatever holds the extra piece on has to either be clear of where the job needs to sit, or flush with the surface, eg using countersunk fasteners. With an aluminium plate, you can tap holes into it to hold the job to it. You do need enough thickness to allow this.

The beauty of mounting things on the faceplate is that it allows jobs that are much closer to the theoretical limits of the machine than chucks do. This is useful for those of us with smaller machines than we would like, which is probably most of us. I was able to bore a three inch bore HP cylinder on my Myford, the furthest out part of the casting was clearing the bed by about an eighth of an inch.

regards

John

From my long experience of electronics I would say that the magic smoke has escaped from one or more devices inside. I suspect that unless you are very experienced with power electronics you are not going to be able to fix it yourself, so checking with the manufacturer is probably your best bet. The problem with fixing this sort of stuff is that a low level fault can easily destroy a power device, so you come along, spot the obviously blown up power device, and promptly destroy another one because the original fault is still there. Fuses don't operate fast enough to save the devices either.

John

I'd agree with the bit about having to unlearn reflexes. I still have a tendency to want to pull the electrode away when I finish, when of course the correct thing is to release the button and wait until the gas cuts off.

With DC only you will not be able to do aluminium. The scratch start will be a bit of a limitation too, but I guess better to have a try with what you have rather than spending a lot on new equipment. If anyone is thinking of buying TIG equipment as a learner, I'd suggest that you go for something more than the bare minimum. The features I would suggest you want to have would be HF start, which makes it a lot easier starting the weld, and AC (as well as DC) which means that you can do aluminium. Being able to do aluminium turns out to be a very useful bonus feature that I hadn't really thought about when I got mine. I had been thinking mainly in terms of stainless steel tanks for the boat, which it does really well.

If it doesn't have a gas solenoid you should be able to add one externally. I've seen a video on Youtube where a guy added one to one of those very cheap very small DC welders that you see advertised. Thus turning a DC MMA welder into a simple TIG machine.

regards

John

I don't know if you still have the larger boat, but if you do maybe you could come up with a trade through the Steam Boat Association. You would have a better chance of that in the UK than you would where I am anyway, here in NZ it would be unlikely for more than one steam launch to come up for sale in a year. Other than that, if you are a member, the whole run of the Funnel magazines is now available online, I have started to read the early ones and there is a bit about steam canoes in some of them. Another thing you could look up, some time back there was a steam punt described in the Model Engineer. He built a copper Yarrow style boiler for it which I think would be within the size that the Model clubs can certify. I'll see if I can find the reference, I would have all the magazines here in my collection.

Steam launch props do tend to be on the large side, with large pitch too. The large diameter is good because a large slow turning prop is more efficient, and the high pitch is necessary because of the relatively low RPM. For an example, the prop on my "Dancer" is 22 inches pitch and 22 inches in diameter. Enormous compared to what you would see on say a 120 hp outboard. I don't have any measurement of the power that the steam plant puts out, but from back of the envelope calculations it is not going to be over 10 bhp on the shaft and probably less, yet that is enough to drive Dancer along at a good 8 knots.

I think I said this already, but anyway, I would avoid the Stuart Number 1, although it is a fine engine. I have built two of them, one with reversing gear. Although they are nice, they are not really beefy enough for the continuous work in a boat. You can sneak in bigger bearings if you try, by making a new crankshaft as large as the space will allow, but the crosshead is still single sided, and the bored type like on the 5A is preferable. Some guys here in NZ made a set of castings for an engine very like the 5A, but with ball bearing mains and I think for the big end too. This makes a very sound job and they have been quite successful in a couple of boats here.

One thing that Cliff Blackestaff said in those early Funnel magazines that I think is worth repeating, don't go for a typical vertical firetube boiler, it puts too much weight up high for a canoe style hull. (The low squat type is OK) You either want a horizontal firetube (Scotch or similar) or a water tube boiler. It used to be that any weight saved with a small water tube boiler was lost in the weight of the insulation for the casing, but now that you can get ceramic fiber based insulation I think you can definitely save some weight with the water tube type. This could be helpful with a canoe. The other aspect is that a tall vertical boiler can look a bit silly in a small boat.

regards

John

I have all those issues. Looks a nice engine, might be a bit fiddly to build but a good size if you ever want to put it in a model boat. (The Stuart is a bit big for a boat, unless you want one about 6 feet long)

I'll send you a PM.

regards

John

Yes, Lithium is not really a problem. There was concern about things like cobalt being needed for some of the Lithium battery types, but I think the need for that has been reduced or eliminated now.

I don't think Lithium is actually a rare earth anyway, at least not on my copy of the periodic table. Where the rare earths come in is for permanent magnets which may be in the electric motors, but then, they don't have to be used there either. Electric cars can use ordinary off the shelf AC induction motors, and I have driven one that did.

Funny thing about mining, once it has stopped it is romantic and a great tourist attraction.

John

The reason I asked above about the hydrogen mines is because of course there aren't any. All hydrogen has to be manufactured, at present mostly from fossil fuel stocks, in the process releasing lots of carbon dioxide into the atmosphere, a thing we were supposed to be trying to avoid. The Germans used to use a different process of passing steam over red hot iron, the iron of course having been made by the usual process involving coal and lots of carbon dioxide.

The point is that hydrogen is not a source of energy, it is merely another way of storing energy and transporting it from place to place. The question them becomes is it a good and economical one? Hydrogen is tricky stuff, it is a small molecule and loves to escape out of containers, through the pores of the metal if necessary. It also ignites quite easily. It takes a lot of energy to make the hydrogen, so the electricity generating system will need upgrading whatever you do.

If you are going to burn the hydrogen in an IC engine, you need to consider that the efficiency will be quite low, so you will probably need to carry more fuel. For this technique you would probably be better to synthesise hydrocarbon fuels, using water and CO2 extracted from the atmosphere. The resulting fuel can then be distributed using the same networks as at present. Since the C02 is extracted from the atmosphere, the process is carbon neutral, and the only major technology change is at the refinery and the power plant providing it with the energy needed for the synthesis. But the overall efficiency remains low since IC engines are pretty abysmal at best.

If you decide to use hydrogen fuel cells, the efficiency will be much higher, since from what I hear the fuel cell can be up around 90% or so, and the electric motor that it runs can also be pretty high, much better overall than the IC option. But the fuel cell currently requires pure hydrogen although I believe there is work being done on cells that can accept hydrocarbons. So you tend to need a new fuel distribution system. The other thing to consider is that the cells tend to require rare and expensive catalysts inside, more so than batteries. It seems that it is possible to eliminate the rare metals from Lithium batteries, it is going to be much harder to eliminate the catalysts from fuel cells.

So long term I don't know what the best solution will turn out to be, but hydrogen is not a panacea. In the meantime, if a battery electric suits your needs then you should probably consider one...they are not suitable for every use case, but if everyone who could use one had one it would make a difference.

John