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Member postings for John Olsen

Here is a list of all the postings John Olsen has made in our forums. Click on a thread name to jump to the thread.

Thread: Old gear
18/09/2021 22:22:38

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.


18/09/2021 11:49:04

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.


Thread: How do you make this
18/09/2021 04:36:13

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.


Thread: Unimat Millenium Model.
17/09/2021 06:56:39

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.



Thread: Empty Drill Boxes
02/09/2021 12:18:18

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.


Thread: What are the potential hazards of using E10 fuel on classic car seals
02/09/2021 12:15:23

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........


Thread: Mounting stuff to a Faceplate
31/08/2021 06:43:57

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.



Thread: Tig welder controls not working correctly
29/08/2021 12:09:23

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.


Thread: Dipping a toe in TIG - what do I need (apart from skill)?
10/08/2021 00:55:01

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.



Thread: Steam Canoe Machinery
09/08/2021 06:11:17

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.



Thread: Triple Expansion Engine
08/08/2021 01:03:40

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.



Thread: Hydrogen
23/07/2021 02:44:59

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.


23/07/2021 00:17:02

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.


22/07/2021 06:57:53

Where are the hydrogen mines?

Thread: Digital CNC phase converter build
20/07/2021 12:12:48

OK, I was thinking in terms of the usual model engineering scale of things, where a Bridgeport is a big machine, you seem to be looking at quite a bit more power than that.

The two phases of your existing supply being at 180 degrees doesn't actually matter, you just need a third phase at about the right phase angle and voltage and things will work. I stand to be corrected here, but if you had a star connected motor, I think the centre tap of the transformer would not be an actual neutral point and so should not be connected to the star point of any motor. Think about it like this, if you had a 480V three phase supply and measured the Voltage between two phases and looked at it on a scope, it would look just like what you see with the single phase supply. So it is true that your converter just needs to provide one new phase at 90 degrees. (We could do vector diagrams to show this....) But this will be effectively a delta connected supply, with no actual neutral point. If you want one you can provide a delta to start transformer at the output although for 40 hp, say 30 KW or so that would be a big and expensive transformer

If there is a rotary component, eg an idler motor, then what you get out will be not too bad. I've actually run a 3 HP 460 Volt motor on single phase, with the 240 Volt supply being stepped up by a transformer and applied to two of the motor connections. It did not self start of course, but a kick on the pulley in the right direction would get things going. I never measure it, but had I needed to run another three phase motor, connecting it to the three phases of that motor would have provided a converter.

With electronics of course it is possible to do this sort of conversion at any sort of power level you like, so long as your wallet can stand the pace. AC to DC and back again is pretty standard for long distance and undersea transmission, and they work up into the 100's of Megawatt range. But I don't know what is commercially available in the sort of size range you want. It won't be cheap, but then the transformer and idler motor won't be either.

Hopefully it is redundant to say that any system will need to be done properly and in accordance with any local regulations, this sort of stuff can easily kill you or burn your house down!



20/07/2021 01:36:40

First consideration has to be how much three phase power do you need? Closely allied to that is the question of what can the existing single phase connection provide?

After that, I guess you will have to look at the cost and merits of the different approaches.

1 A static converter (Transformer plus inductors and capacitors) will work and allow you to use more than one machine from it, but the phase to phase angles will not be ideal .

2 A rotary converter, similar to the above plus an idler motor will give better output phases but will waste a bit of power keeping the idler motor turning. The idler motor provides a bit of flywheel effect, helping with the surge when you turn a machine on.

3 The various sorts of electronic inverter will provide excellent output waveforms and so on, but may cost a little more. You have the choice of providing one big one that all the machines connect to as if it was an ordinary three phase supply, or little ones on the basis of one per machine, which give the advantage that you can use the inverter as a variable frequency drive.

4 Generate your own three phase as per Noels suggestion. Perfectly feasible but has its own set of troubles like noise and complexity.

5 Pay through the nose to have three phase installed. This always seems to cost far more than the job really warrants, I get the impression that suppliers around the world would rather you didn't have three phase.

You can't add capacitors to the AC output of an inverter to smooth the supply or to provide for starting surges. On electronic inverters, such capacitors would go inside on the DC bus and you would not want to try to modify the design. There will be small capacitors on the output to help suppress interference, and you probably don't want to change those either. On a rotary inverter, the idler motor provides a flywheel function.

My own preference is to use a VFD for each machine, which gives the advantage of variable speed, but for some machines this means getting inside to alter the wiring, eg to make sure that a coolant pump or a fine feed motor is getting what it needs rather than running off the variable frequency supply. Some may not be comfortable modifying their machines in this way. I think with the relatively low cost of VFD's these days it is quite a good way to go.


Thread: re-magnetising magnetic base
08/07/2021 04:23:09

If I needed to do something like that I would be thinking about using my DC inverter welder to provide the necessary current. It can do 200 Amps, and has its own built in current limiting so it is not going to complain if it is connected to a coil of heavy wire. Then it would be just a matter of making up a magnetic circuit with the coil of heavy wire around it. It doesn't actually take very long to remagnetise things, long enough for the field to build up to the maximum, which is going to be in milliseconds rather than seconds.

Another approach is to use a car battery and a coil.


Thread: De-snagging an SL125
27/06/2021 04:45:24

I had the CB100, rather than the SL version, but the muffler was just a large chamber, the only baffle it had was the little unit that appears as part 6 in your picture. It was not excessively loud, even after I converted it to 125 and put a hot cam in it. They never had any packing material like the Dunstall Decibels used. (I had one of those on a Triumph 250, it was reasonably quiet just after it was repacked, and got louder quite quickly as it shredded the packing and blew it out the back.)

I did notice when I had occasion to ask some years back that Honda mufflers were a bit on the pricey side. Bad enough if you just want one, but it would help explain why the fours after a couple of years all had four into one systems fitted. Quieter, lighter, and cheaper as well as more power!


21/06/2021 03:09:14

The shaper compares more to a horizontal mill than a vertical mill in terms of the work it does. Great for flat surfaces, not so good at making pockets and boring holes. You can do some interesting things if you put either a rotary table or a dividing head and tailstock onto a shaper.

However, in terms of the sort of work mentioned, eg small stationary engines and locomotives, my suggested order of acquisition would be the lathe first (of course!) followed by a vertical mill. The mill will also act as a drill. Shapers are not available new, so if you decide you want one, the best course is just to keep your eyes open and see what comes up. On the other hand, if you were able to get a mill that does both vertical and horizontal milling you probably don't need a shaper. Still, I like having mine, and I have three of them.


Thread: Steam operated drain cocks
14/06/2021 05:01:57

Sorry Duncan, 1 is the end that should connect to the cylinder. The pressure from the steam on the other end holds the valve on the seat. When there is no pressure there, any pressure in the cylinder can open the valve, allowing it to drain. The ones on my steam launch are just like the one shown, and they work fine. If the pressure in the cylinder gets high enough, say from trying to compress water, it can overcome the steam pressure on the other end and vent anyway, so they act as a relief valve, although I have also provided separate relief valves as well. The operating valve should be a changeover type, so that in one position it connects live steam to the valve, and in the other it connects the cylinder end of the valve to atmosphere.

The operating cylinder part needs to be big enough to hold the valve on its seat, but not so much bigger that it won't act as a relief valve. The ratio of the areas will approximately determine the pressure at which it opens.

I don't have drawings of mine, they were made by eye from a sketch, and they would be a bit big for all but the largest of model locos.


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