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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.

22/04/2019 22:33:09

Lathe tool shapes will work fine. The most useful general purpose general purpose tool is probably a V shape, eg grind the end to a V with some clearance each side, and grind a bit of top rake on top, then put a very small radius or flat on the V end. This is used for planing flat surfaces, and it will cut feeding either when you are planing down a surface, when you get to the far side, you add a little more cut and then reverse the direction of the table feed. A similar shape is sometimes used as a roughing cutter on a lathe, but they are not usually expected to cut in both directions.

But otherwise...a standard lathe type knife tool will cut into a corner, a parting type tool can cut slots and so on. Slots of course have all the usual problems like parting off. A narrow angle cutter is all that is needed to cut dovetails, along with a bit of thought about how to set the clapper box angle.


21/04/2019 23:13:22

First time I have seen one mounted on the wall!

That is a ten inch Alba just like mine, a very handy size of machine. I see you have a very solid looking vice with it too, you will find that useful.

I don't suppose you will have any desperate need to take the head off, but there is a trick to it if you do. You have to turn the head around so it is upside down.



Thread: Making Holes in Copper Sheet
19/04/2019 10:49:55

I would probably use a hole saw for the initial hole, still using the bits of ply as you intend. Ordinary drills are not always very good on sheet metal. Otherwise a step drill or a conecut would make a better job on sheet metal than a normal drill, but they can be a bit expensive if you don't already have one.. Using a boring tool, either a boring head in the mill if you have one, or boring in the lathe should be a good way to get the final size. Take it gently with all the work, copper can be a bit grabby at times.


Thread: Telescopic bore gauges
17/04/2019 01:32:52

Mine didn't come from Arc Euro, but are the same sort of thing. They can be a bit fiddly, there is a bit of a knack to it but I would expect to get a bore within about a thou of nominal with them. But then the internal mike I have for larger bores also can be a bit fiddly, and they are a lot more expensive.


Thread: Notre Dame
16/04/2019 23:56:32

Of course if we were really serious about feeding the hungry etc, we wouldn't be wasting our time posting on this site, we would be out digging in the garden to give the produce to the poor.

Not all resources can be usefully applied to any particular problem, eg the people who can rebuild the cathedral probably could not directly contribute to curing cancer.


Thread: Folding Bike design & build
10/04/2019 01:15:49

My wife and I took a couple of Dahon folding bikes on a world tour last year, which meant they had to fit into a standard airline check in bag size. That means 1580mm max total dimensions of the bag, and under 23 kg. So small bikes are of interest, since the trip was successful enough that we would love to do the same sort of thing again. This looks like a promising design, but I would echo the question someone asked above, what is the gearing like. It is hard to get a high enough top gear with small wheels. Not that you are going to want to go extremely Dahon has the 16 inch wheels and an 8 speed derailleur. The bottom gear is plenty low enough, the top could be a little higher but it is really hard to do that since you need a larger front sprocket. It has been done but they are hard to get, I might have to make one. The gear hub inside the back wheel is a good idea, again provided you can manage to source something suitable.

The other thing I would suggest thinking about is a carrier of some sort. My wife's Dahon came with one and it does not significantly affect the folded size. I had to buy and fit one for mine, which meant a bit of modification on the milling machine, but again it can be left on when folded and still fit the airline bag. I did fit it using quick release fasteners so that it can be taken off easily. Even if you do not plan airline travel, one of the good uses for a folding bike is trips to the shops from either a small apartment or even a caravan or campervan. (US RV) You may not need (or want!) to carry a lot of stuff but it is a handy thing to be able to do. We were able to fold down the big bag once the bike was out and strap it on the little carrier, wear the carry on, and bicycle to our bed and breakfast places.

The Dahons are around the 11 or 12 kg mark, which leaves a bit of extra available in the bag to carry clothes etc. Between that and our carry on bags, we were able to travel for two months quite comfortably. Of course there are little expedients to keep the weight of the bags down, like wearing the camera and keeping the lenses in my pockets.

Bikes are a bit frustrating, when you think that the 12 kg or so of mostly aluminium should be able to pack down into under 30 litres or so, if only there was a simple way to do that. Well, we could pack it down OK by melting it, but getting it unpacked would be more of a challenge.


Thread: ST #5A Reverse Gear
06/04/2019 20:42:26

Some of the Stuart engines use a rod to retain the reversing handle in the desired position, It attaches to (with a pivot) one corner of the valve chest and has a screw with a cross hole in it to grip on it at the reversing lever, and a small knob on the end to stop the reversing lever going too far. An alternative arrangement would use an arm with a slot in it.


Thread: Stress Relieving Rolled Mild Steel
05/04/2019 10:33:49

I would get out the propane torch and heat it up to a good red heat, keep it there for a while, and then let it cool as slowly as possible. A few chunks of firebricks around it to make a rudimentary furnace would help keep the drafts off. There will be some scale but not as much as with the old way of putting it in the embers of the fire overnight. There is very little danger of accidently getting it too hot, you won't melt it with anything you are likely to have at home.

If you don't have a propane torch, it is a really worthwhile thing to acquire, since you can also use it to harden bits of silver steel, or drill rod if you like. (or gauge plate.)


Thread: shaper machine unknown accessory
04/04/2019 04:54:05

I think Jordi has it right, it is for adjusting the stroke. I will also guess that it is not a manufacturers accessory, but something that has been made by a former owner. It is not that a precise adjustment of the stroke is all that important, it is that it can take a bit of to and fro to get the stroke anything like, and while you are doing it your hands are inside the machine, just waiting for someone to bump the power switch and put you in a world of pain.

Some shapers are easy to 18 inch Alba has the screw and bevel gears inside the bull wheel, so it can all be done from the operators side. My 6 inch Ammco does not, but it is a small machine, and it is easy to get the position right, you get the slotted arm in the vertical position and the crank pin will slide up and down easily and stay in the right position while you lock it up. My 10 inch Alba has the same arrangement, but it is not so easy to get it adjusted to a good position, it fights a bit and the rather small door opening gets in the way. So it is easy to see that someone might have decided that a more sophisticated way of adjusting the stroke was desirable.


01/04/2019 15:04:03

It looks to me like the leadscrew from a lathe cross slide or compound table. The right angle pin at the end would go in a hole in the slide, so that the slide is pulled back and forth when the handle is turned, but the alignment between the screw part and the slide is not too critical. It doesn't look like anything I have seen on a shaper before.

The shaper itself looks like a good machine, and the vice looks like just the bee knees! The gearbox does indeed seem to be ex motorcycle, possibly replacing a stepped pulley for a belt drive. My Dad once used one from a two stroke motorcycle for a drill press, cutting away the engine part first.


Thread: Open Crank IC Plans
27/03/2019 00:17:03

The Rina engine was described in Model Engineer a few years back. were a few problem areas in the drawings but I can help with corrections. I haven't actually built the engine.


Thread: Super adept on ebay
25/03/2019 00:51:33

So how is your silk purse version coming along Neil?

Haven't done anything with my Aussie clone version yet...


24/03/2019 23:45:37

For the shaping between centres, yes, for a circular part you use the worm drive on the dividing head for a feed. But you can also make flats at arbitrary angles by setting to the angle, then taking a cut with the normal table feed. My eccentric straps used a combination of those techniques. The bottom half of the strap is a circular arc between the two "ears" for the screws, and the top part is a trapezoidal shape. I made a long piece of the section desired, then sliced it up into the four pieces needed and cleaned up the sides in the lathe. Then they were halved to make the top and bottom pieces.

Note that the supplementary table can do either concave or convex, depending on the slope of the angled guide bar.

Someone further back mentioned keeping the cutting edge back relative to the clapper box. Ideally you would do this, but it is not always possible. One case is when cutting keyways in a bore, and another was cutting the inside of my expansion links, which needed a tool that stuck out in front. If you can, have the cutting edge behind the clapper box, but if you can't, make sure things are as rigid as possible. My 10 inch Alba came with a set of Jones and Shipman tool holders, the kind that take a quarter inch square bit. They are the sort meant for a lathe, and this means that the tool bit is out in front, but despite this they work very well on the shaper. That is not to say that the proper shaper ones would not work better, but since they are pretty rare these days, try what you have, Just making sure things are as rigid as possible.

I have ME back to about 1944 with a few before that, so if you can't find the 1950 article give me a shout and I can scan it.

24/03/2019 20:23:51

There is another technique for doing large radius arcs of a circle on a shaper. It uses a supplementary table, pivoted at one side of the main table, and constrained to tilt by an angled guide bar. I built one, based on a special vice for a planer described in an old book, and used it to make expansion links for my steam launch engine. I wrote an article for Model Engineer some years back, it can be found at:



Volume 194





John Olsen (New Zealand) Cutting Curves on the Shaping Machine A novel attachment

The curve cut is not actually a precise arc of a circle, but it is close enough for all practical purposes. The radius can be anything up to infinity, but there is a limit to how small it can be depending on the size of the supplementary table and the machine. Smaller radii would be better done on a lathe. The ones I did for my expansion links would be about 6 inches or so radius, somewhat larger than I could do on the Myford.

The shaping between centres technique, as shown in the Popular Mechanics article, is a very useful one when you need something to have a partly round shape. I have used this to produce eccentric straps, where they have a half round shape but the ears for the screws stick out so they can't be turned on the lathe. Ammco used to make an attachment for their six inch shaper to do this sort of work. Not being able to get hold of an original one, I've made a copy for my Ammco. I also have a ground flat bar about 2 inches by 4 inches by a couple of feet long that lets me mount my Vertex dividing head on the 18 inch Alba shaper The tailstock goes nearest the shaper and the dividing head is over the edge of the table, allowing the use of most of the stroke for the actual job.

John Olsen

Thread: New drill-1PH to 3PH wiring
09/03/2019 20:42:10

The .45 kW inverter will be fine with your motor, a bit of spare capacity is not a problem. The motor will need to be wired delta. This is usually not a problem, unless the star point is buried inside the winding, but since it is a dual voltage motor it must be accessible. There is quite likely a little diagram, maybe inside the cover over the terminal.

The remote control parts will all be low voltage rated. Usually all you need is a couple of switches (forward/reverse and on/off) and a potentiometer for the speed. The latter is probably about 10k ohms, linear, but check what the instructions say, if you can decipher them! I made mine up in one of those small diecast boxes that the electronics shops usually sell.

No switches or plugs on the motor side, and preferably shielded cable there.

If you are not used to this stuff it might pay to find someone who has done it before to help.


Thread: Bowl shaped propellor
08/03/2019 21:51:29

Actually film cameras typically either had an in lense shutter or a focal plane shutter. The in lense shutter exposes the entire negative at the same time, but the focal plane shutter, found in any single lense reflex, does not, at least at the higher speeds. This gives rise to distortions in moving subjects. The shutter consists of two moving blinds which travel across the film plane. At low speeds there is a time where the whole film plane is exposed but at high speeds the two blinds form a moving slit which travels across the film. For a typical 35mm single lense reflex, the highest speed at which the film is fully exposed is 1/60 of a second, and this speed is used for flash. At higher speeds, motion distortion effects may be seen, but they would be most obvious in vertically moving objects. Objects moving horizontally would be just stretched or shrunk a little

I've been told that the reason that artists depict things like fast moving cars with the radiator leaning forwards is that that is how they appeared in photos at the time, taken with a vertical run shutter. Most modern SLRs have a horizontal run shutter, although I have a Pentax MX with a vertical run shutter with metal blades. That also runs faster than most, with the flash sync at 1/125 second.


Thread: Building as Hand Operated Shaper
06/03/2019 20:09:03

Good to see that there are some shapers being made, too many have gone to scrap. The Gingery book are a good resource even if you don't need to do the whole thing from scratch. There are plenty of good ideas in them about how to end up with an accurate machine even if you lack a larger machine to do the job on. I like the idea of building a mock up in wood first, I did this sort of thing a lot when building my steam launch. The entire interior layout and cabin design was first built with scrap material like cardboard and cover sheets from MDF at the hardware suppliers. It is a good cheap way of letting you visualise the whole job.


Thread: Precision division plates
06/03/2019 19:53:27

There is a technique for making an accurate leadscrew from scratch. When you draw wire through a die you can get long lengths with a very consistent diameter. The die will eventually wear, but for the sort of length we need we can get a very consistent diameter. So then you turn a long mandrel parallel, and close wind the wire around it to form a thread. Because the wire is constant diameter and the mandrel is parallel, this will give a constant pitch screw, with the pitch being the diameter of the wire. Now you cast a lead nut around the wire thread and break it free...coating the wire with graphite first will help. Now you have a nice accurate leadscrew, so you can set up and cut a worm, or probably first, cut a more lasting type of leadscrew for your lathe.

So the worm is not an impossible problem, however to make the worm wheel, you need accurate dividing you need an accurate worm and wheel.

I've tried the technique where you use a tap to form a worm wheel. It works, but there is no guarantee that you will end up with the number of teeth that you planned for, quite often you will get one more or one less. Presumably the teeth can also be out of position by a small amount, but how will you check?


Thread: Morse Taper 2 blanks
05/03/2019 19:20:07

The morse taper blanks that I have had occasion to modify have been just surface hardened...probably nitrided. So a bit of a grind on the end to take off a millimeter or so, and then you are into material that you can drill and tap. This may not apply to all makes but it is worth a try, I have done it to more than one.


Thread: Larger ball check valve lift
03/03/2019 04:15:55

The usual rule of thumb is that the lift should be no more than a quarter of the diameter. That provides an opening equal to the area of the hole. So a higher lift gives no extra flow, and increases the time taken for the ball to come back down when the flow reverses. Generally a smaller lift makes for less problems with the balls not seating properly, but of course you don't want to restrict the flow too much. The ball should not be able to move sideways too much either

The piston diameter and stroke don't bear directly on what the lift should be, but the hole should obviously be large enough for the flow expected. So a similar size to the pipe you would expect to use to carry the resulting flow would be reasonable.

(If you care to do the maths, you will find that the area of a round hole is equal to the (cylindrical) area between the ball and seat when the ball has lifted 1/4 of the diameter of the hole. The same applies for poppet valves. )


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