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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: Glue du jour
22/01/2020 05:31:23

My understanding is that if Loctite is still runny, it is still good. So if you can still get it out of the bottle it should be OK. (Maybe not if you are working on life critical stuff! )

It can go off in the bottle, especially if you do things like clearing the nozzle with a metal pin. Metal ions will catalyze the reaction.


Thread: New legislation that could affect us all.
09/01/2020 20:36:12

We have got into the habit of always closing the lid down properly ever since we saw a video somewhere of a rat climbing up out of a toilet. They are out there in the sewers and apparently the u bend is no obstacle to a determined rat.


Thread: VFD Question
08/01/2020 10:20:53

Hi Gerard,

The usual VFD can only provide a maximum phase to phase voltage the same as the input AC Voltage. So it will run a delta connected 240 Volt motor at full power. The same motor if Star connected would run off the usual 415 V supply. This supply would provide 240 Volts between phase and neutral. Most motors come star connected for 415, and it is usual to have to restrap them to delta connected to run off a VFD, at least the type of VFD that is designed for 240V input. (There are VFD's that will take three phase input, these are not usually of much interest to amateurs since we usually don't have three phase power.)

There are VFDs that will take a 240V supply and provide the correct output for a 415 V star connected motor, probably by using a voltage doubling rectifier. I have no experience with these, but they have been on the market for a while, so presumably work OK.

Incidently you can run a motor on a lower voltage than the plate rating when necessary. I have a shaper with a Delta connected 460 Volt motor. This makes it impossible to lower the voltage rating, since if I star connected it the required Voltage would go up, to over 600 Volts. But it actually runs fine from a VFD , even the the voltage is effectively half what it should be. This limits the maximum power to about half the nameplate rating too, but since it is a three horsepower motor, half that will shift metal quite fast enough for most purpose.

So normal 3 phase is 240 phase to neutral, 415 phase to phase, but the three phase from a VFD is 240V phase to phase, and there is no neutral. (The neutral from the incoming mains is not a neutral for the output side.)


Thread: The Engineers Emporium - Red Wing hit and miss engine
02/01/2020 23:11:05

I got my Red Wing castings direct from PM Research in Wellsville, a little country town in upstate New York. I'm planning to install the minimag magneto as described on RCDons site. Anyone thinking of doing this should contact the minmag people, they were out of stock when I ordered mine and had been thinking of dropping the kit due to lack of demand.


Thread: Eccentrics
25/12/2019 04:23:21

The ideal lead on the eccentrics will depend on the lap of the associated valve. If you are sufficiently curious, you could measure all the relevant parts and do a diagram or better yet, use the Dockstater software to see what the events are like.


Thread: Castings, creating a datum before milling
23/12/2019 04:26:47

Nick, To drill gunmetal with less risk of grabbing, it would be worthwhile to stone the rake off the cutting edges of the drill. This can be done by hand with a small stone. To be clear, this is not done on the end facets of the drill, it is done on the flute so that where the drill is cutting it has zero or negative rake, rather than the positive rake that the flute gives as it reaches the cutting edge.

A drill treated this way is not as good for cutting steel as it used to be, but if you can manage it, it can be good to have a few treated this way for brass and gunmetal.


Thread: Three phase Variac Internal wiring
15/12/2019 19:55:34

Robert, I don't think that connection with the two in series will work properly, at least not if you put any load on it. The impedence of the one with the load on will be lower than the other, so the voltage will vary with the load. The two cores would need to be magnetically coupled for it to work well.

We once had a number of VHF receivers that were burning out lots of mains transformers, a little 25 VA affair. By testing (with a Variac!) we found that they had too few turns on the primary, and were only good for about 180V input. The magnetising current below that was very small, only 20mA or so, but there is is very pronounced knee in the curve when you reach saturation. We successfully rewound one with about 20% more turns and that gave no further trouble, but of course that was an unauthorised modification and we could not persuade the powers that be to let us fix the rest, so we just had to keep on changing the transformers at frequent intervals.


Thread: Nuts
04/12/2019 21:16:57

Further to Neils comment...the 11foot8 bridge is actually in Durham North Carolina at the corner of Gregson and Peabody Streets. The bridge was recently raised 8 inches, so it is now 12 foot 4. This has not prevented someone from hitting it already. Last I saw the total number of collisions was up to 151 See

There is also a low bridge under a railway line in Needles California which is 8 foot 6 inches, we were in a campervan at the time that would not have made it, but were observant enough to see the signs. (N K St, Needles, California.)



Thread: pressure release valve
17/11/2019 20:51:38

If the relief valve is on the turret it is liable to lift water when it goes off. That can lead to a slug of water going down the main steam line to the engine. With larger plant this is the last thing you want to happen. It is not so likely to cause problems with the sot of engine you would run off a five inch boiler. If you keep the original valve and set the one on the turret to lift at a slightly higher pressure, it will only open if the original valve is not quite coping.

Ideally the size of the valve should be such that the pressure does not rise more than 10% over the set pressure when the boiler is being fired and no steam is being taken for other purposes. That is called an accumulation test, eg how much pressure accumulates when the plant is running full bore, the load stops taking steam, and the valve has to control the pressure.


Thread: Black anodised steel????
13/11/2019 00:53:53

The reason galvanising is called that is because the Galvanic action takes place when the protected metal is exposed to wet corrosive surroundings. When this happens, the action is such that the zinc is consumed and the steel is protected. So if galvanised metal is used in salt water, the zinc will eventually be consumed.


Thread: Battery charger problem
03/10/2019 01:15:26

A lithium battery that has gone below 3.7 volts per cell is probably not going to recover. Some of the chargers sold for charging them for model aircraft have a setting that will attempt to recover a cell that has been over discharged, I think by gently charging them at a low constant current until the cell comes up into the normal range. (3.7V is flat, 4.2 V is fully charged.) This sometimes works, but not all that often.

NiCd cells can suffer from whiskering, tiny crystals of nickel that short them out. A pulse of a good high current will sometimes fuse the whisker, after which they will take a charge again, although probably not improved by the experience. So far as I know there is no similar effect with lithium cells and as has been commented, they do not react well to overcharging.


Thread: Red Wing build article
02/10/2019 00:01:16

I'm currently building one, and a Minimag to go with it, the same as in the RCDON build log referred to by MichaelR above. I'm about 9/10 of the way through both builds. I picked up my set of castings at the factory when I was in the USA last year, and started machining them about last Christmas. Not very fast working, but my main project is getting my steam launch finished.

I'd be happy to discuss the Red Wing. The casting are all of excellent quality and I am very pleased with it.


Thread: cutter slippage using ER series collets
29/09/2019 02:25:59

Well, I hadn't heard of ball bearing nuts, so I did a google, and found an interesting video showing the difference.


So now I guess I will have to buy a new nut for my ER32 set!


Thread: Petrol Gen for 7 1/4 locomotive
16/09/2019 02:39:07

If you want to be a bit different you could have a three phase motor, which would be smaller than a single phase of the same power. You would supply it with a VFD (AC motor control) which would be supplied from the Generator. The downside of this sort of arrangement is that everything is high voltage. The nice side is that everything is available off the shelf.


Thread: To Pin or Not To Pin
11/09/2019 06:59:42

I've just received the latest "Funnel" magazine from the Steam boat association and there is some discussion there about pinned and loctited crankshafts for the Leak compound engine. Apparently the published build instructions from Camden press suggest doing it that way, and apparently quite a lot of people have had trouble with cranks made that way. I didn't have the Camden book when I built mine, just the original Model Engineer articles, so I went for a crank locally cast in SG iron, which is also what the Funnel now suggests as a solution. It is interesting that the pinned and loctited ones should give trouble, since in a steam launch there should not generally be a lot of shock loading, unless you are in the habit of running hard aground. I would have thought that a locomotive would be more demanding.

Press fits with no keys work fine on many motorcycle crankshafts, but getting the right degree of interference could be a bit of a challenge in the home workshop


Thread: Just bought an ML7, what should i do first?
11/09/2019 06:17:59

Ok, just been out to check what my one has. The spindle has a 65 tooth bull wheel, that's the one with the little dog to engage and disengage it. The other one on the spindle has 30 teeth. The ones on the back gear shaft seem to be the 21 and 56 combination, assuming I counted correctly which is a bit harder with that one. It is a bit oily under there! My ML7 is early fifties vintage.

Is it the one on the spindle that is broken, or the back one? Mine has one tooth missing on the spindle one. I have the spare but have not yet got around to putting it in, and it actually works fine for the odd time I have needed back gear. NDIY is right that you can do a fix in a number of ways that will be quite satisfactory, they are not all that heavily loaded.

The usual cause of broken teeth on these gears is using the back gear to stop the spindle rotating so you can get a stuck chuck off. This is not what you should do!

The 65 tooth gear means that you cannot use a simple detent on the bullgear to do simple dividing, unless all you ever need is either 13 or 5 divisions.


10/09/2019 06:44:06

You can get a new back gear easy enough from RDG, mine was about NZ$60 if I recall correctly. Change wheels are not a problem until you want to cut threads, so long as you have enough to give you a useful fine feed. The price sounds pretty good considering the prices sometimes asked for Myfords here in NZ, even if you do have to do a bit of work. Don't rush into doing any major work. until you have had a bit of a play with it.

So whereabouts in NZ are you? I'm in Cambridge (NZ) myself.


Thread: Hello
02/09/2019 23:24:29

AS Bill says, there is a little sliding catch on the bull wheel which is held in place with an allan screw. To engage it, you need to loosen the allan screw, slide the catch inwards to engage with the gear teeth on the smaller wheel, then tighten the screw again. You need an Allan key with a very short leg for this, eg cut away most of the smaller leg of the Allan key so it will reach in Ok


Thread: Lathe rigidity
02/09/2019 06:23:40

You could make a split lap to polish the shaft. The lap needs to be made of something softish, brass or aluminium for instance, bored to an easy fit on the shaft, and then split with a saw cut and drilled and tapped for a screw that can be used to close it up slightly. Then you can lap the spindle, using a bit of fine valve grinding paste. You can work the lap by hand since the lathe will be out of action. This is quite a slow way of removing material so gives quite good control. The spindle wants a good clean afterwards of course.


Thread: Trip to New Zealand
27/08/2019 04:11:41

Since other people might also be interested here are a few suggestions:

Most cities have a model railway club with a track.

Auckland has the Museum of Transport and Technology (MOTAT) which has a beam pumping engine and plenty of other stuff to see from trams to aircraft.

Glenbrook Vintage Railway is not far out of Auckland, they have their own dedicated branch line and run steam locos. Would pay to check when they run first.

Whanganui has a working river paddle steamer, the Waimarie. Again it would pay to check when they run.

There is a good steam museum at Tokomaru near Palmerston North, however it has only just been bought by new owners and I am not sure what the situation is with visiting yet.

Near Christchurch there are two places, Ferrymead heritage park and Mcleans island "Steam Scene." I haven't been to either for a long time but I believe they are both worth a look.

At Ashburton there is the Plains railway, they have a beautiful Rogers 2-4-2 of 1877 vintage among other things.

There is a gas works museum in Dunedin.

On Lake Wanaka is the twin screw steamer Earnslaw, well worth a trip both for the scenery and the ship. The Earnslaw runs daily.

I don't know how you plan to travel within NZ, but many tourist find that a self contained campervan is a good way to go. Being a relatively sparsely populated country, public transport is not all that prolific although there are plenty of flights between the main centres. I think sometimes people book two separate campervans, one in each island, since it saves the cost of crossing the strait with one. We drive on the left here, same as the UK. Apart from near the cities, there is very little motorway and most main roads are only one lane each way. You generally don't need to plan to drive very far in any one day.



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